Ecological impacts of the late Quaternary megaherbivore extinctions.

PubMed

Gill, Jacquelyn L

2014-03-01

As a result of the late Quaternary megafaunal extinctions (50,000-10,000 before present (BP)), most continents today are depauperate of megaherbivores. These extinctions were time-transgressive, size- and taxonomically selective, and were caused by climate change, human hunting, or both. The surviving megaherbivores often act as ecological keystones, which was likely true in the past. In spite of this and extensive research on the causes of the Late Quaternary Extinctions, the long-term ecological consequences of the loss of the Pleistocene megafauna remained unknown until recently, due to difficulties in linking changes in flora and fauna in paleorecords. The quantification of Sporormiella and other dung fungi have recently allowed for explicit tests of the ecological consequences of megafaunal extirpations in the fossil pollen record. In this paper, I review the impacts of the loss of keystone megaherbivores on vegetation in several paleorecords. A growing number of studies support the hypothesis that the loss of the Pleistocene megafauna resulted in cascading effects on plant community composition, vegetation structure and ecosystem function, including increased fire activity, novel communities and shifts in biomes. Holocene biota thus exist outside the broader evolutionary context of the Cenozoic, and the Late Quaternary Extinctions represent a regime shift for surviving plant and animal species.

A model of late quaternary landscape development in the Delaware Valley, New Jersey and Pennsylvania

USGS Publications Warehouse

Ridge, J.C.; Evenson, E.B.; Sevon, W.D.

1992-01-01

In the Delaware Valley of New Jersey and eastern Pennsylvania the late Quaternary history of colluviation, fluvial adjustment, and soil formation is based on the ages of pre-Wisconsinan soils and glacial deposits which are indicated by feld relationships and inferred from mid-latitude climate changes indicated by marine oxygen-isotope records. The area is divided into four terranes characterized by sandstone, gneiss, slate and carbonate rocks. Since the last pre-Wisconsinan glaciation (> 130 ka, inferred to be late Illinoian), each terrane responded differently to chemical and mechanical weathering. During the Sangamon interglacial stage (??? 130-75 ka) in situ weathering is inferred to have occurred at rates greater than transportation of material which resulted in the formation of deep, highly weathered soil and saprolite, and dissolution of carbonate rocks. Cold climatic conditions during the Wisconsinan, on the other hand, induced erosion of the landscape at rates faster than soil development. Upland erosion during the Wisconsinan removed pre-Wisconsinan soil and glacial sediment and bedrock to produce muddy to blocky colluvium, gre??zes lite??es, and alluvial fans on footslopes. Fluvial gravel and overlying colluvium in the Delaware Valley, both buried by late Wisconsinan outwash, are inferred to represent episodes of early and middle Wisconsinan (??? 75-25 ka) upland erosion and river aggradiation followed by river degradation and colluvium deposition. Early-middle Wisconsinan colluvium is more voluminous than later colluvium despite colder, possibly permafrost conditions during the late Wisconsinan ??? 25-10 ka). Extensive colluviation during the early and middle Wisconsinan resulted from a longer (50 kyr), generally cold interval of erosion with a greater availability of easily eroded pre-Wisconsinan surficial materials on uplands than during the late Wisconsinan. After recession of late Wisconsinan ice from its terminal position, soil formation and

Northern Hemisphere Glaciation during the Globally Warm Early Late Pliocene

PubMed Central

De Schepper, Stijn; Groeneveld, Jeroen; Naafs, B. David A; Van Renterghem, Cédéric; Hennissen, Jan; Head, Martin J.; Louwye, Stephen; Fabian, Karl

2013-01-01

The early Late Pliocene (3.6 to ∼3.0 million years ago) is the last extended interval in Earth's history when atmospheric CO2 concentrations were comparable to today's and global climate was warmer. Yet a severe global glaciation during marine isotope stage (MIS) M2 interrupted this phase of global warmth ∼3.30 million years ago, and is seen as a premature attempt of the climate system to establish an ice-age world. Here we propose a conceptual model for the glaciation and deglaciation of MIS M2 based on geochemical and palynological records from five marine sediment cores along a Caribbean to eastern North Atlantic transect. Our records show that increased Pacific-to-Atlantic flow via the Central American Seaway weakened the North Atlantic Current and attendant northward heat transport prior to MIS M2. The consequent cooling of the northern high latitude oceans permitted expansion of the continental ice sheets during MIS M2, despite near-modern atmospheric CO2 concentrations. Sea level drop during this glaciation halted the inflow of Pacific water to the Atlantic via the Central American Seaway, allowing the build-up of a Caribbean Warm Pool. Once this warm pool was large enough, the Gulf Stream–North Atlantic Current system was reinvigorated, leading to significant northward heat transport that terminated the glaciation. Before and after MIS M2, heat transport via the North Atlantic Current was crucial in maintaining warm climates comparable to those predicted for the end of this century. PMID:24349081

Late Quaternary transgressive large dunes on the sediment-starved Adriatic shelf

USGS Publications Warehouse

Correggiari, A.; Field, M.E.; Trincardi, F.

1996-01-01

The Adriatic epicontinental basin is a low-gradient shelf where the late-Quaternary transgressive systems tract (TST) is composed of thin parasequences of backbarrier, shoreface and offshore deposits. The facies and internal architecture of the late-Quaternary TST in the Adriatic epicontinental basin changed consistently from early transgression to late transgression reflecting: (1) fluctuations in the balance between sediment supply and accommodation increase, and (2) a progressive intensification of the oceanographic regime, driven by the transgressive widening of the basin to as much as seven times its lowstand extent. One of the consequences of this trend is that high-energy marine bedforms such as sand ridges and sand waves characterize only areas that were flooded close to the end of the late-Quaternary sea-level rise, when the wind fetch was maximum and bigger waves and stronger storm currents could form. We studied the morphology, sediment composition and sequence-stratigraphical setting of a field of asymmetric bedforms (typically 3 m high and 600 m in wavelength) in 20-24 m water depth offshore the Venice Lagoon in the sediment-starved North Adriatic shelf. The sand that forms these large dunes derived from a drowned transgressive coastal deposit reworked by marine processes. Early cementation took place over most of the dune crests limiting their activity and preventing their destruction. Both the formation and deactivation of this field of sand dunes occurred over a short time interval close to the turn-around point that separates the late-Quaternary sea-level rise and the following highstand and reflect rapid changes in the oceanographic regime of the basin.

Late quaternary environments, Denali National Park and Preserve, Alaska

USGS Publications Warehouse

Elias, S.A.; Short, S.K.; Waythomas, C.F.

1996-01-01

Late Quaternary pollen, plant macrofossils, and insect fossils were studied from sites along three rivers in the foothills north of the Alaska Range in Denali National Park and Preserve. The aim was to carry out a reconaissance of late Quaternary organic sediments in the region, emphasizing the mid-Wisconsin, or Boutellier interstadial interval. Samples of probable early- to mid-Boutellier age (ca. 60 000 to 40 000 B.P.) from Unit 2 at the Toklat High Bluffs site indicate open boreal woodland with dense alder shrub vegetation. Organic Unit 1 at the Foraker River Slump site indicates open taiga with shrubs of probable Boutellier age. Fossil evidence from the youngest horizon in this unit indicates graminoid tundra environments, marking the transition from interstadial to late Wisconsin glacial environments. Early Holocene samples from the Foraker exposures suggest birch shrub tundra; coniferous forest apparently became established only alter 6500 B.P. Local variations in forest composition at the Foraker and Sushana sites were probably the result of disturbances, such as fire.

Origin and late quaternary tectonism of a western Canadian continental shelf trough

NASA Astrophysics Data System (ADS)

Moslow, Thomas F.; Luternauer, John L.; Rohr, Kristin

1991-08-01

Analyses of high resolution and multi-channel seismic profiles from the central continental shelf of western Canada ascribe a late Quaternary glacial origin to large-scale troughs. Along the margins of Moresby Trough, one of three large-scale cross-shelf bathymetric depressions in Queen Charlotte Sound, seismic profiles within Quaternary sediments show a divergence of reflectors, thickening and folding of seismic units, and concavity of reflectors suggestive of drag. Compactional subsidence, growth faulting, and compaction faulting are also observed. Fault traces commonly terminate below the seabed. Deformation of Quaternary sediments due to faulting is plastic in nature and maximum offset of reflectors is 2.5 m. The observed Quaternary deformation appears to be a product of rapid deposition, loading and subsidence of late Quaternary sediment, which is unrelated to seismic activity. In addition, Quaternary faulting was probably activated by post-glacial loading and isostatic rebound of consolidated Tertiary strata along the margins of continental shelf troughs. The presence of mass movement (slump or debris flow) deposits overlying lithified Tertiary strata along the flanks of Moresby Trough provides the only evidence of seismic activity in the study area. The lack of a mud drape over these deposits implies a late Holocene age for the timing of their emplacement. The Quaternary troughs are incised into Tertiary-aged sedimentary fill of the Queen Charlotte basin. Previous workers had interpreted seafloor escarpments paralleling the trough margins to indicate that the location of Moresby Trough was controlled by renewed or continued activity on Tertiary-aged faults. A multi-channel seismic line across Moresby Trough shows that such an escarpment on the seafloor does not correlate to faults either in the Tertiary basin fill or the underlying basement. Tertiary reflectors are continuous underneath Moresby Trough; the seafloor escarpment is an erosional feature and was

Middle and Late Pleistocene glaciations in the southwestern Pamir and their effects on topography

USGS Publications Warehouse

Stubner, Konstanze; Grin, Elena; Hidy, Alan J.; Schaller, Mirjam; Gold, Ryan D.; Ratschbacher, Lothar; Ehlers, Todd

2017-01-01

Glacial chronologies provide insight into the evolution of paleo-landscapes, paleoclimate, topography, and the erosion processes that shape mountain ranges. In the Pamir of Central Asia, glacial morphologies and deposits indicate extensive past glaciations, whose timing and extent remain poorly constrained. Geomorphic data and 15 new 10Be exposure ages from moraine boulders and roches moutonnées in the southwestern Pamir document multiple Pleistocene glacial stages. The oldest exposure ages, , underestimate the age of the earliest preserved glacial advance and imply that the modern relief of the southwestern Pamir (peaks at ∼5000–6000 m a.s.l.; valleys at ∼2000–3000 m a.s.l.) already existed in the late Middle Pleistocene. Younger exposure ages (∼40–80 ka, ∼30 ka) complement the existing Central Asian glacial chronology and reflect successively less extensive Late Pleistocene glaciations. The topography of the Pamir and the glacial chronologies suggest that, in the Middle Pleistocene, an ice cap or ice field occupied the eastern Pamir high-altitude plateau, whereas westward flowing valley glaciers incised the southwestern Pamir. Since the Late Pleistocene deglaciation, the rivers of the southwestern Pamir adjusted to the glacially shaped landscape. Localized rapid fluvial incision and drainage network reorganization reflect the transient nature of the deglaciated landscape.

Reconstruction of the extent and variability of late Quaternary ice sheets and Arctic sea ice: Insights from new mineralogical and geochemical proxy records

NASA Astrophysics Data System (ADS)

Stein, R. H.; Niessen, F.; Fahl, K.; Forwick, M.; Kudriavtseva, A.; Ponomarenko, E.; Prim, A. K.; Quatmann-Hense, A.; Spielhagen, R. F.; Zou, H.

2016-12-01

The Arctic Ocean and surrounding continents are key areas within the Earth system and very sensitive to present and past climate change. In this context, the timing and extent of circum-Arctic ice sheets and its interaction with oceanic and sea-ice dynamics are major interest and focus of international research. New sediment cores recovered during the Polarstern Expeditions PS87 (Lomonosov Ridge/2014) and PS93.1 (Fram Strait/2015) together with several sediment cores available from previous Polarstern expeditions allow to carry out a detailed sedimentological and geochemical study that may help to unravel the changes in Arctic sea ice and circum-Arctic ice sheets during late Quaternary times. Our new data include biomarkers indicative for past sea-ice extent, phytoplankton productivity and terrigenous input as well as grain size, physical property, XRD and XRF data indicative for sources and pathways of terrigenous sediments (ice-rafted debris/IRD) related to glaciations in Eurasia, East Siberia, Canada and Greenland. Here, we present examples from selected sediment cores that give new insights into the timing and extent of sea ice and glaciations during MIS 6 to MIS 2. To highlight one example: SE-NW oriented, streamlined landforms have been mapped on top of the southern Lomonosov Ridge (LR) at water depths between 800 and 1000 m over long distances during Polarstern Expedition PS87, interpreted to be glacial lineations that formed beneath grounded ice sheets and ice streams. The orientations of the lineations identified are similar to those on the East Siberian continental margin, suggesting an East Siberian Chukchi Ice Sheet extended far to the north on LR during times of extreme Quaternary glaciations. Based on our new biomarker records from Core PS2757 (located on LR near 81°N) indicating a MIS 6 ice-edge situation with some open-water phytoplankton productivity, the glacial erosional event should have been older than MIS 6 (e.g., MIS 12?).

Late Quaternary landscape evolution in the Kunlun Mountains and Qaidam Basin, Northern Tibet: A framework for examining the links between glaciation, lake level changes and alluvial fan formation

USGS Publications Warehouse

Owen, L.A.; Finkel, R.C.; Haizhou, M.; Barnard, P.L.

2006-01-01

The Qaidam Basin in Northern Tibet is one of the largest hyper-arid intermontane basins on Earth. Alluvial fans, pediment surfaces, shorelines and a thick succession of sediments within the basin, coupled with moraines and associated landforms in the adjacent high mountain catchments of the Kunlun Mountains, record a complex history of Late Quaternary paleoenvironmental change and landscape evolution. The region provides an ideal natural laboratory to examine the interaction between tectonics and climate within a continent-continent collision zone, and to quantify rates of landscape evolution as controlled by climate and the associated glacial and hydrological changes in hyper-arid and adjacent high-altitude environments. Geomorphic mapping, analysis of landforms and sediments, and terrestrial cosmogenic radionuclide surface exposure and optically stimulated luminescence dating serve to define the timing of formation of Late Quaternary landforms along the southern and northwestern margins of the Qaidam Basin, and in the Burhan Budai Shan of the Kunlun Mountains adjacent to the basin on the south. These dates provide a framework that suggests links between climatic amelioration, deglaciation, lake desiccation and alluvial fan evolution. At least three glacial advances are defined in the Burham Budai Shan of the Kunlun Mountains. On the northern side of this range these occurred in the penultimate glacial cycle or early in the last glacial cycle, during the Last Glacial Maximum (LGM)/Lateglacial and during the Holocene. On the south side of the range, advances occurred during the penultimate glacial cycle, MIS-3, and possibly the LGM, Lateglacial or Holocene. Several distinct phases of alluvial fan sedimentation are likewise defined. Alluvial fans formed on the southern side of the Kunlun Mountains prior to 200 ka. Ice-contact alluvial fans formed during the penultimate glacial and during MIS-3. Extensive incised alluvial fans that form the main valley fills north of

Quaternary fluvial history of the Delaware River, New Jersey and Pennsylvania, USA: The effects of glaciation, glacioisostasy, and eustasy on a proglacial river system

NASA Astrophysics Data System (ADS)

Stanford, Scott D.; Witte, Ron W.; Braun, Duane D.; Ridge, John C.

2016-07-01

Fluvial, glacial, and estuarine deposits in the Delaware Valley record the response of the Delaware River to glaciation, sea-level change, and glacioisostasy during the Quaternary. Incision following an early Pleistocene glaciation created the present valley, which is inset into a Pliocene strath and fluvial plain. Middle and upper Pleistocene and Holocene deposits were laid down in this inset valley. Estuarine terraces in the lower valley and bayshore at + 20 m (probably Marine Isotope Stage [MIS] 11), + 8 m (MIS 5e), and + 3 m (MIS 5a or c), and a fluvial deposit that correlates to offshore MIS 3 marine deposits at - 20 m are at elevations consistent with glacioisostatic models. Successive incisions during lowstands in the middle and late Pleistocene lengthened, deepened, and narrowed the channel in the lower valley and shifted the channel westward in Delaware Bay. During MIS 2 glaciation, from 25 to 18 ka, the Delaware was diverted to the Hudson Shelf Valley by glacioisostatic tilting. Most glacial sediment was trapped in fluvial-lacustrine valley fills north of the terminal moraine. Incision of the valley fill was accomplished during the early stage of rebound, between 17 and 12 ka. Drainage to the Delaware shelf was restored between 15 and 13 ka as the forebulge collapsed. During incision, multiple postglacial terraces formed where the valley was perpendicular to rebound contours and so was steepened and elevated northward; and a single terrace formed where the valley paralleled the contours, and there was no differential elevation or steepening. About 65% of the original volume of MIS 2 glacial sediment remains in the main valley, and most of the eroded volume is in the channel in the lower valley beneath Holocene estuarine fill. Little glacial sediment reached the Delaware or Hudson shelf. Overbank deposition on the lower postglacial terrace and modern floodplain spans the Holocene. The volume of Holocene sediment in the estuary and bay yields a basinwide

Late Pleistocene glaciation of the Mt Giluwe volcano, Papua New Guinea

USGS Publications Warehouse

Barrows, T.T.; Hope, G.S.; Prentice, M.L.; Fifield, L.K.; Tims, S.G.

2011-01-01

The Mt Giluwe shield volcano was the largest area glaciated in Papua New Guinea during the Pleistocene. Despite minimal cooling of the sea surface during the last glacial maximum, glaciers reached elevations as low as 3200 m. To investigate changes in the extent of ice through time we have re-mapped evidence for glaciation on the southwest flank of Mt Giluwe. We find that an ice cap has formed on the flanks of the mountain on at least three, and probably four, separate occasions. To constrain the ages of these glaciations we present 39 new cosmogenic 36Cl exposure ages complemented by new radiocarbon dates. Direct dating of the moraines identifies that the maximum extent of glaciation on the mountain was not during the last glacial maximum as previously thought. In conjunction with existing potassium/argon and radiocarbon dating, we recognise four distinct glacial periods between 293-306 ka (Gogon Glaciation), 136-158 ka (Mengane Glaciation), centred at 62 ka (Komia Glaciation) and from >20.3-11.5 ka (Tongo Glaciation). The temperature difference relative to the present during the Tongo Glaciation is likely to be of the order of at least 5 ??C which is a minimum difference for the previous glaciations. During the Tongo Glaciation, ice was briefly at its maximum for less than 1000 years, but stayed near maximum levels for nearly 4000 years, until about 15.4 ka. Over the next 4000 years there was more rapid retreat with ice free conditions by the early Holocene. ?? 2011 Elsevier Ltd.

Soil-landscape development and late Quaternary environmental change in coastal Estremadura, Portugal

NASA Astrophysics Data System (ADS)

Daniels, Michael; Haws, Jonathan; Benedetti, Michael; Bicho, Nuno

2015-04-01

This poster integrates soil-landscape analysis with archaeological survey and paleoenvironmental reconstruction. Soils in surface and buried contexts in Estremadura, Portugal, provide evidence of landscape stability and instability, relative age relationships between landforms, and general paleoenvironmental conditions during the late Quaternary. These factors provide insight into the distribution and condition of Paleolithic archaeological sites and help understand the record of human settlement in the region. Late Pleistocene and Holocene dunes extend inland approximately 10 km from coastal source regions. Surface soils in Holocene dunes under maritime pine (Pinus pinaster) forest exhibit A, E, C/Bh and A, C horizon sequences and classify as Quartzipsamments. Surface soils in late Pleistocene dunes exhibit A, E, Bh, Bhs, Bs horizon sequences and classify as Haplorthods. Both Pleistocene and Holocene dunes commonly bury a heavily weathered soil formed in calcareous sandstone. The boundary between underlying buried soils and overlying surface soils is characterized by a lag deposit of medium to coarse, moderately-rounded gravels, underlain immediately by subsurface Bt and Bss horizons. The lag deposit and absence of buried A horizons both indicate intense and/or prolonged surface erosion prior to burial by late Quaternary dunes. Soil-geomorphic relationships therefore suggest at least two distinct episodes of dune emplacement and subsequent landscape stability following an extensive episode late Pleistocene landscape instability and soil erosion. A conceptual model of soil-landscape evolution through the late Quaternary and Holocene results from the integration of soil profile data, proxy paleoenvironmental data, and the partial record of human settled as revealed in the archaeological record.

Late Quaternary chronology of paleo-climatic changes in Caspian Sea region based on Lower Volga sections

NASA Astrophysics Data System (ADS)

Kurbanov, Redzhep; Yanina, Tamara; Murray, Andrew; Svitoch, Alexander; Tkach, Nikolai

2017-04-01

Lower Volga is a unique region for understanding the history of the Caspian Sea in the Pleistocene, its correlation of paleogeographic events with glacial-interglacial rhythms of the East European Plain and the global and regional climate changes. The reason is representativeness of Quaternary sections, their completeness, presence of both marine and subaerial sediments, paleontological richness of the materials and available for study. The purpose of this work is to reconstruct the paleogeographic events in the Late Pleistocene of the Lower Volga region on the basis of summarizing the study results for the Srednyaya Akhtuba reference section. Located near city of Volgograd, at Khvaynian plain natural outcrop of Srednyaya Akhtuba section, reveals in a series of exposures a unique to the region series of marine Caspian continental deposits with four levels of buried soil horizons and loess. The results were obtained during 2015 and 2016 complex field research with application of lithological, paleopedological, paleontological, paleocryological, OSL-dating, paleomagnetic methods, that allowed more fundamental approach to the chronological assessment of individual horizons. The structure of the Srednyaya Akhtuba reference section reflects a number of paleogeographic stages of development of the study area. The oldest phase (layers 22-19) is not characterized by OSL dating or faunal material. Based on the sequence of dated layers, we assume its Middle Pleistocene age (MIS-6 stage), corresponding to Moscow stage of the Dnieper glaciation of the East European Plain and the final stage of Early Khazarian transgressive era of Caspian sea. The next stage (layers 18-14), represented by three horizons of paleosols, refers to the first half of the Late Pleistocene (MIS 5). Epoch of soil formation, based on the results the OSL-dating, can be referred to the warm sub-stages (MIS 5c and 5a), with unstable climatically transitional phase from Mikulino (Eemian) interglacial to the

The influence of climate on species distribution over time and space during the late Quaternary

NASA Astrophysics Data System (ADS)

Carotenuto, F.; Di Febbraro, M.; Melchionna, M.; Castiglione, S.; Saggese, F.; Serio, C.; Mondanaro, A.; Passaro, F.; Loy, A.; Raia, P.

2016-10-01

Understanding the effect of climate on the composition of communities and its change over time and space is one of the major aims in ecology and paleoecology. Herein, we tackled on this issue by studying late Quaternary large mammal paleocommunities of Eurasia. The late Quaternary was a period of strong environmental instability, especially characterized by the occurrence of the last glacial maximum (LGM). We used community phylogenetics and joint species distribution models in order to understand the factors determining paleocommunity composition in the late Quaternary. Our results support the existence of strong climatic selection operating on the LGM fauna, both through the disappearance of warm-adapted species such as Elephas antiquus, Hippopothamus amphibious, and Stephanorhinus hemitoechus, and by setting the stage for the existence of a community characterized by cold-adapted large mammals. Patterns of abundance in the fossil record, co-occurrence between species pairs, and the extent of climatic forcing on faunal composition, differ between paleocommunities, but not between extinct and extant species, which is consistent with the idea that climate change, rather than the presence of humans, exerted a major effect on the survival of the late Quaternary megafauna.

Late Quaternary climate change shapes island biodiversity.

PubMed

Weigelt, Patrick; Steinbauer, Manuel Jonas; Cabral, Juliano Sarmento; Kreft, Holger

2016-04-07

Island biogeographical models consider islands either as geologically static with biodiversity resulting from ecologically neutral immigration-extinction dynamics, or as geologically dynamic with biodiversity resulting from immigration-speciation-extinction dynamics influenced by changes in island characteristics over millions of years. Present climate and spatial arrangement of islands, however, are rather exceptional compared to most of the Late Quaternary, which is characterized by recurrent cooler and drier glacial periods. These climatic oscillations over short geological timescales strongly affected sea levels and caused massive changes in island area, isolation and connectivity, orders of magnitude faster than the geological processes of island formation, subsidence and erosion considered in island theory. Consequences of these oscillations for present biodiversity remain unassessed. Here we analyse the effects of present and Last Glacial Maximum (LGM) island area, isolation, elevation and climate on key components of angiosperm diversity on islands worldwide. We find that post-LGM changes in island characteristics, especially in area, have left a strong imprint on present diversity of endemic species. Specifically, the number and proportion of endemic species today is significantly higher on islands that were larger during the LGM. Native species richness, in turn, is mostly determined by present island characteristics. We conclude that an appreciation of Late Quaternary environmental change is essential to understand patterns of island endemism and its underlying evolutionary dynamics.

Mammoth Mountain and its mafic periphery—A late Quaternary volcanic field in eastern California

USGS Publications Warehouse

Hildreth, Wes; Fierstein, Judith; Champion, Duane E.; Calvert, Andrew T.

2014-01-01

The trachydacite complex of Mammoth Mountain and an array of contemporaneous mafic volcanoes in its periphery together form a discrete late Pleistocene magmatic system that is thermally and compositionally independent of the adjacent subalkaline Long Valley system (California, USA). The Mammoth system first erupted ca. 230 ka, last erupted ca. 8 ka, and remains restless and potentially active. Magmas of the Mammoth system extruded through Mesozoic plutonic rocks of the Sierra Nevada batholith and extensive remnants of its prebatholith wall rocks. All of the many mafic and silicic vents of the Mammoth system are west or southwest of the structural boundary of Long Valley caldera; none is inboard of the caldera’s buried ring-fault zone, and only one Mammoth-related vent is within the zone. Mammoth Mountain has sometimes been called part of the Inyo volcanic chain, an ascription we regard inappropriate and misleading. The scattered vent array of the Mammoth system, 10 × 20 km wide, is unrelated to the range-front fault zone, and its broad nonlinear footprint ignores both Long Valley caldera and the younger Mono-Inyo range-front vent alignment. Moreover, the Mammoth Mountain dome complex (63%–71% SiO2; 8.0%–10.5% alkalies) ended its period of eruptive activity (100–50 ka) long before Holocene inception of Inyo volcanism. Here we describe 25 silicic eruptive units that built Mammoth Mountain and 37 peripheral units, which include 13 basalts, 15 mafic andesites, 6 andesites, and 3 dacites. Chemical data are appended for nearly 900 samples, as are paleomagnetic data for ∼150 sites drilled. The 40Ar/39Ar dates (230–16 ka) are given for most units, and all exposed units are younger than ca. 190 ka. Nearly all are mildly alkaline, in contrast to the voluminous subalkaline rhyolites of the contiguous long-lived Long Valley magma system. Glaciated remnants of Neogene mafic and trachydacitic lavas (9.1–2.6 Ma) are scattered near Mammoth Mountain, but Quaternary

Late Quaternary faulting along the Death Valley-Furnace Creek fault system, California and Nevada

USGS Publications Warehouse

Brogan, George E.; Kellogg, Karl; Slemmons, D. Burton; Terhune, Christina L.

1991-01-01

The Death Valley-Furnace Creek fault system, in California and Nevada, has a variety of impressive late Quaternary neotectonic features that record a long history of recurrent earthquake-induced faulting. Although no neotectonic features of unequivocal historical age are known, paleoseismic features from multiple late Quaternary events of surface faulting are well developed throughout the length of the system. Comparison of scarp heights to amount of horizontal offset of stream channels and the relationships of both scarps and channels to the ages of different geomorphic surfaces demonstrate that Quaternary faulting along the northwest-trending Furnace Creek fault zone is predominantly right lateral, whereas that along the north-trending Death Valley fault zone is predominantly normal. These observations are compatible with tectonic models of Death Valley as a northwest-trending pull-apart basin. The largest late Quaternary scarps along the Furnace Creek fault zone, with vertical separation of late Pleistocene surfaces of as much as 64 m (meters), are in Fish Lake Valley. Despite the predominance of normal faulting along the Death Valley fault zone, vertical offset of late Pleistocene surfaces along the Death Valley fault zone apparently does not exceed about 15 m. Evidence for four to six separate late Holocene faulting events along the Furnace Creek fault zone and three or more late Holocene events along the Death Valley fault zone are indicated by rupturing of Q1B (about 200-2,000 years old) geomorphic surfaces. Probably the youngest neotectonic feature observed along the Death Valley-Furnace Creek fault system, possibly historic in age, is vegetation lineaments in southernmost Fish Lake Valley. Near-historic faulting in Death Valley, within several kilometers south of Furnace Creek Ranch, is represented by (1) a 2,000-year-old lake shoreline that is cut by sinuous scarps, and (2) a system of young scarps with free-faceted faces (representing several faulting

Geomorphic investigation of the Late-Quaternary landforms in the southern Zanskar Valley, NW Himalaya

NASA Astrophysics Data System (ADS)

Sharma, Shubhra; Hussain, Aadil; Mishra, Amit K.; Lone, Aasif; Solanki, Tarun; Khan, Mohammad Khatib

2018-02-01

The Suru, Doda and Zanskar river valleys in the semi-arid region of Southern Zanskar Ranges (SZR) preserve a rich repository of the glacial and fluvial landforms, alluvial fans, and lacustrine deposits. Based on detailed field observations, geomorphic mapping and limited optical ages, we suggest four glaciations of decreasing magnitude in the SZR. The oldest Southern Zanskar Glaciation Stage (SZS-4) is inferred from glacially polished bedrock and tillite pinnacles. The SZS-4 is ascribed to the Marine Isotopic Stage (MIS)-4/3. The subsequent SZS-3 is represented by obliterated and dissected moraines, and is assigned to MIS-2/Last Glacial Maximum. The multiple recessional moraines of SZS-2 glaciation are assigned the early to mid Holocene age whereas, the youngest SZS-1 moraines were deposited during the Little Ice Age. We suggest that during the SZS-2 glaciation, the Drang-Drung glacier shifted its course from Suru Valley (west) to the Doda Valley (east). The study area has preserved three generations of outwash gravel terraces, which broadly correlate with the phases of deglaciation associated with SZS-3, 2, and 1. The alluvial fan aggradation, lacustrine sedimentation, and loess deposition occurred during the mid-to-late Holocene. We suggest that glaciation was driven by a combination of the mid-latitude westerlies and the Indian Summer Monsoon during periods of cooler temperature, while phases of deglaciation occurred during enhanced temperature.

Exploring the MIS M2 glaciation occurring during a warm and high atmospheric CO2 Pliocene background climate

NASA Astrophysics Data System (ADS)

Tan, Ning; Ramstein, Gilles; Dumas, Christophe; Contoux, Camille; Ladant, Jean-Baptiste; Sepulchre, Pierre; Zhang, Zhongshi; De Schepper, Stijn

2017-08-01

Prior to the Northern Hemisphere glaciation around ∼2.7 Ma, a large global glaciation corresponding to a 20 to 60 m sea-level drop occurred during Marine Isotope Stage (MIS) M2 (3.312-3.264 Ma), interrupted the period of global warmth and high CO2 concentration (350-450 ppmv) of the mid Piacenzian. Unlike the late Quaternary glaciations, the M2 glaciation only lasted 50 kyrs and occurred under uncertain CO2 concentration (220-390 ppmv). The mechanisms causing the onset and termination of the M2 glaciation remain enigmatic, but a recent geological hypothesis suggests that the re-opening and closing of the shallow Central American Seaway (CAS) might have played a key role. In this article, thanks to a series of climate simulations carried out using a fully coupled Atmosphere Ocean General Circulation Model (GCM) and a dynamic ice sheet model, we show that re-opening of the shallow CAS helps precondition the low-latitude oceanic circulation and affects the related northward energy transport, but cannot alone explain the onset of the M2 glaciation. The presence of a shallow open CAS, together with favourable orbital parameters, 220 ppmv of CO2 concentration, and the related vegetation and ice sheet feedback, led to a global ice sheet build-up producing a global sea-level drop in the lowest range of proxy-derived estimates. More importantly, our results show that the simulated closure of the CAS has a negligible impact on the NH ice sheet melt and cannot explain the MIS M2 termination.

Late Quaternary dynamics of a South African floodplain wetland and the implications for assessing recent human impacts

NASA Astrophysics Data System (ADS)

Tooth, S.; Rodnight, H.; McCarthy, T. S.; Duller, G. A. T.; Grundling, A. T.

2009-05-01

Knowledge of the long-term geomorphological dynamics of wetlands is limited, so currently there is an inadequate scientific basis for assessing anthropogenically induced changes and for developing conservation, remediation, and/or sustainable management guidelines for these fragile ecosystems. Along the upper Klip River, eastern South Africa, geomorphological and sedimentological investigations, geochronology, and remote sensing have been used to establish the late Quaternary dynamics of some internationally important floodplain wetlands, thus providing a reference condition against which to assess the extent of recent human impacts. Optically stimulated luminescence dating reveals that the wetlands have developed over at least the last 30 ky as a result of slow meander migration (< 0.2 m y - 1 ), irregular cutoff events, and infrequent avulsions (approximately one every 3-6 ky) that have occurred autogenically as a natural part of meander-belt development. Following European settlement in the Klip valley (late nineteenth century), however, modifications to local flora and fauna, as well as the initiation of local wetland drainage schemes, have had major impacts. In particular, proliferation of exotic willows and associated debris jams, and the artificial excavation of a 1.2-km-long channel section across the wetlands have initiated an ongoing avulsion that is characterised by failure (gradual abandonment) of the main channel and rapid incision of a headcutting channel. Compared to the pre-settlement condition, little change in lateral migration activity has occurred, but this avulsion provides a clear example of anthropogenically accelerated change, occurring only ~ 1 ky after the last natural avulsion and in a part of the wetlands where avulsions have not occurred previously. Subsequent human interventions have included installing weirs in an attempt to control the resulting erosion and promote reflooding, but ongoing maintenance has been required. In areas that

Global late Quaternary megafauna extinctions linked to humans, not climate change.

PubMed

Sandom, Christopher; Faurby, Søren; Sandel, Brody; Svenning, Jens-Christian

2014-07-22

The late Quaternary megafauna extinction was a severe global-scale event. Two factors, climate change and modern humans, have received broad support as the primary drivers, but their absolute and relative importance remains controversial. To date, focus has been on the extinction chronology of individual or small groups of species, specific geographical regions or macroscale studies at very coarse geographical and taxonomic resolution, limiting the possibility of adequately testing the proposed hypotheses. We present, to our knowledge, the first global analysis of this extinction based on comprehensive country-level data on the geographical distribution of all large mammal species (more than or equal to 10 kg) that have gone globally or continentally extinct between the beginning of the Last Interglacial at 132,000 years BP and the late Holocene 1000 years BP, testing the relative roles played by glacial-interglacial climate change and humans. We show that the severity of extinction is strongly tied to hominin palaeobiogeography, with at most a weak, Eurasia-specific link to climate change. This first species-level macroscale analysis at relatively high geographical resolution provides strong support for modern humans as the primary driver of the worldwide megafauna losses during the late Quaternary.

Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

NASA Astrophysics Data System (ADS)

Ao, Hong; Roberts, Andrew P.; Dekkers, Mark J.; Liu, Xiaodong; Rohling, Eelco J.; Shi, Zhengguo; An, Zhisheng; Zhao, Xiang

2016-06-01

Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential relationships between northern hemispheric monsoon response and major Cenozoic changes in Antarctic ice cover. Here we document long-term East Asian summer monsoon (EASM) intensification through the Late Miocene-Pliocene (∼8.2 to 2.6 Ma), and attribute this to progressive Antarctic glaciation. Our new high-resolution magnetic records of long-term EASM intensification come from the Late Miocene-Pliocene Red Clay sequence on the Chinese Loess Plateau; we identify underlying mechanisms using a numerical climate-model simulation of EASM response to an idealized stepwise increase in Antarctic ice volume. We infer that progressive Antarctic glaciation caused intensification of the cross-equatorial pressure gradient between an atmospheric high-pressure cell over Australia and a low-pressure cell over mid-latitude East Asia, as well as intensification of the cross-equatorial sea-surface temperature (SST) gradient. These combined atmospheric and oceanic adjustments led to EASM intensification. Our findings offer a new and more global perspective on the controls behind long-term Asian monsoon evolution.

Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

NASA Astrophysics Data System (ADS)

Ao, H.; Roberts, A. P.; Dekkers, M. J.; Liu, X.; Rohling, E. J.; Shi, Z.; An, Z.; Zhao, X.

2016-12-01

Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential relationships between northern hemispheric monsoon response and major Cenozoic changes in Antarctic ice cover. Here we document long-term East Asian summer monsoon (EASM) intensification through the Late Miocene-Pliocene (˜8.2 to 2.6 Ma), and attribute this to progressive Antarctic glaciation. Our new high-resolution magnetic records of long-term EASM intensification come from the Late Miocene-Pliocene Red Clay sequence on the Chinese Loess Plateau; we identify underlying mechanisms using a numerical climate-model simulation of EASM response to an idealized stepwise increase in Antarctic ice volume. We infer that progressive Antarctic glaciation caused intensification of the cross-equatorial pressure gradient between an atmospheric high-pressure cell over Australia and a low-pressure cell over mid-latitude East Asia, as well as intensification of the cross-equatorial sea-surface temperature (SST) gradient. These combined atmospheric and oceanic adjustments led to EASM intensification. Our findings offer a new and more global perspective on the controls behind long-term Asian monsoon evolution.

Evidence for a heavily glaciated Antarctica during the late Oligocene "warming" (27.8-24.5 Ma): Stable isotope records from ODP Site 690

NASA Astrophysics Data System (ADS)

Hauptvogel, D. W.; Pekar, S. F.; Pincay, V.

2017-04-01

High δ18O values (> 3.0‰) from a 9 kyr resolution benthic foraminiferal stable isotope record from the Ocean Drilling Program hole 690B located on the Maud Rise, Antarctica, indicate a heavily glaciated Antarctic continent during late Oligocene (27.8-24.5 Ma). Values ranging 2.5-3.0‰ during interglacial periods and 3.0-3.6‰ during glacial intervals are consistent with an ice sheet near or larger than modern size. In addition, this record does not exhibit the long-term late Oligocene warming trend seen in records from low-latitude drill sites. Oxygen isotope values from 26.0 to 24.5 Ma are comparable (ranging between 2.5 and 3.3‰) to values that preceded the δ18O event Oi2b at 26.7 Ma, indicating no significant glacial collapse occurred during the late Oligocene. A gradient between ocean basins during the Oligocene has already been linked to the development of a modern, multilayered ocean and worked to bathe the low latitude to midlatitude, deep-sea records with a warmer water mass. We suggest that this masked the significant Antarctic glaciation in low-latitude paleoceanographic records. Additionally, we propose a resolution for conflicting lines of evidence from some Antarctic proximal records suggesting significant glaciation and others suggesting reduced glaciation during the late Oligocene by allowing a modern-sized ice sheet to grow on an Antarctic continent as more land surface area existed above sea level during this time. This could allow at least some portions of the Antarctic coastline to remain ice-free during glacial minima while still maintaining modern or near-modern ice volume.

The Late Eocene 187Os / 188Os excursion: Chemostratigraphy, cosmic dust flux and the Early Oligocene glaciation

NASA Astrophysics Data System (ADS)

Dalai, Tarun K.; Ravizza, Gregory E.; Peucker-Ehrenbrink, B.

2006-01-01

High resolution records (ca. 100 kyr) of Os isotope composition ( 187Os / 188Os) in bulk sediments from two tropical Pacific sites (ODP Sites 1218 and 1219) capture the complete Late Eocene 187Os / 188Os excursion and confirm that the Late Eocene 187Os / 188Os minimum, earlier reported by Ravizza and Peucker-Ehrenbrink [Earth Planet. Sci. Lett. 210 (2003) 151-165], is a global feature. Using the astronomically tuned age models available for these sites, it is suggested that the Late Eocene 187Os / 188Os minimum can be placed at 34.5 ± 0.1 Ma in the marine records. In addition, two other distinct features of the 187Os / 188Os excursion that are correlatable among sections are proposed as chemostratigraphic markers which can serve as age control points with a precision of ca. ± 0.1 Myr. We propose a speculative hypothesis that higher cosmic dust flux in the Late Eocene may have contributed to global cooling and Early Oligocene glaciation (Oi-1) by supplying bio-essential trace elements to the oceans and thereby resulting in higher ocean productivity, enhanced burial of organic carbon and draw down of atmospheric CO 2. To determine if the hypothesis that enhanced cosmic dust flux in the Late Eocene was a cause for the 187Os / 188Os excursion can be tested by using the paired bulk sediment and leachate Os isotope composition; 187Os / 188Os were also measured in sediment leachates. Results of analyses of leachates are inconsistent between the south Atlantic and the Pacific sites, and therefore do not yield a robust test of this hypothesis. Comparison of 187Os / 188Os records with high resolution benthic foraminiferal δ18O records across the Eocene-Oligocene transition suggests that 187Os flux to the oceans decreased during cooling and ice growth leading to the Oi-1 glaciation, whereas subsequent decay of ice-sheets and deglacial weathering drove seawater 187Os / 188Os to higher values. Although the precise timing and magnitude of these changes in weathering fluxes

Geomorphological and sedimentary evidence of probable glaciation in the Jizerské hory Mountains, Central Europe

NASA Astrophysics Data System (ADS)

Engel, Zbyněk; Křížek, Marek; Kasprzak, Marek; Traczyk, Andrzej; Hložek, Martin; Krbcová, Klára

2017-03-01

The Jizerské hory Mountains in the Czech Republic have traditionally been considered to be a highland that lay beyond the limits of Quaternary glaciations. Recent work on cirque-like valley heads in the central part of the range has shown that niche glaciers could form during the Quaternary. Here we report geomorphological and sedimentary evidence for a small glacier in the Pytlácká jáma Hollow that represents one of the most-enclosed valley heads within the range. Shape and size characteristics of this landform indicate that the hollow is a glacial cirque at a degraded stage of development. Boulder accumulations at the downslope side of the hollow probably represent a relic of terminal moraines, and the grain size distribution of clasts together with micromorphology of quartz grains from the hollow indicate the glacial environment of a small glacier. This glacier represents the lowermost located such system in central Europe and provides evidence for the presence of niche or small cirque glaciers probably during pre-Weichselian glacial periods. The glaciation limit (1000 m asl) and paleo-ELA (900 m asl) proposed for the Jizerské hory Mountains implies that central European ranges lower than 1100 m asl were probably glaciated during the Quaternary.

Late Quaternary geomorphic history of a glacial landscape - new sedimentary and chronological data from the Cordillera de Cochabamba (Bolivia)

NASA Astrophysics Data System (ADS)

May, J.-H.; Preusser, F.; Zech, R.; Ilgner, J.; Veit, H.

2009-04-01

Throughout the Central Andes, glacial landscapes have long been used for the reconstruction of Late Quaternary glaciations and landscape evolution. Much work has focused on the Andes in Peru, Chile and the Bolivian Altiplano, whereas relatively little data has been published on glaciation history in the eastern Andean ranges and slopes. Even less is known with regard to the postglacial evolution of these glacial landscapes. In the Cordillera de Cochabamba (Bolivia), local maximum advances probably peaked around 20-25 ka BP and were followed by significant readvances between ~12-16 ka BP. This generally points to temperature controlled maximum glacial advances along the humid eastern slopes of the Central Andes, which is supported by glacier-climate-modelling studies. However, most studies include only marginal information with regard to the complex geomorphic and sedimentary situation in the Cordillera de Cochabamba. Furthermore, the chronological results are afflicted with several methodological uncertainties inherent to surface exposure dating and call for application of alternative, independent age dating methods. Therefore this study aims at i) documenting and interpreting the complex glacial geomorphology of the Huara Loma valley in the Cordillera de Cochabamba (Bolivia), ii) analyzing the involved units of glacial sediments, and iii) improving the chronological framework by applying optically stimulated luminescence (OSL) and radiocarbon dating (14C). For this purpose, geomorphic mapping was combined with field documentation of sedimentary profiles. The involved sediments were subject to geochemical and mineralogical analysis in order to deduce information on their erosional and weathering histories. In addition, the interpretation of OSL ages from glacial and proglacial sediments integrated several methodological procedures with regard to sample preparation and statistical analysis of the measurements in order to increase the degree of confidence. These

An East Siberian ice shelf during the Late Pleistocene glaciations: Numerical reconstructions

NASA Astrophysics Data System (ADS)

Colleoni, Florence; Kirchner, Nina; Niessen, Frank; Quiquet, Aurélien; Liakka, Johan

2016-09-01

A recent data campaign in the East Siberian Sea has revealed evidence of grounded and floating ice dynamics in regions of up to 1000 m water depth, and which are attributed to glaciations older than the Last Glacial Maximum (21 kyrs BP). The main hypothesis based on this evidence is that a small ice cap developed over Beringia and expanded over the East Siberian continental margin during some of the Late Pleistocene glaciations. Other similar evidence of ice dynamics that have been previously collected on the shallow continental shelves of the Arctic Ocean have been attributed to the penultimate glaciation, i.e. Marine Isotopes Stage 6 (≈140 kyrs BP). We use an ice sheet model, forced by two previously simulated MIS 6 glacial maximum climates, to carry out a series of sensitivity experiments testing the impact of dynamics and mass-balance related parameters on the geometry of the East Siberian ice cap and ice shelf. Results show that the ice cap developing over Beringia connects to the Eurasian ice sheet in all simulations and that its volume ranges between 6 and 14 m SLE, depending on the climate forcing. This ice cap generates an ice shelf of dimensions comparable with or larger than the present-day Ross ice shelf in West Antarctica. Although the ice shelf extent strongly depends on the ice flux through the grounding line, it is particularly sensitive to the choice of the calving and basal melting parameters. Finally, inhibiting a merging of the Beringia ice cap with the Eurasian ice sheet affects the expansion of the ice shelf only in the simulations where the ice cap fluxes are not large enough to compensate for the fluxes coming from the Eurasian ice sheet.

The ``Problem of the quaternary'' and the taxonomic rank of the late cenozoic in the international stratigraphic scale

NASA Astrophysics Data System (ADS)

Zubakov, V. A.

2011-02-01

An international scientific conflict has arisen around the International Stratigraphic Scale, the main document that regulates the rules of reading of geological records and, hence, concerns all Earth sciences. The matter of debate is the geological time scale of 2004, developed by the International Commission on Stratigraphy, where the Quaternary system was abandoned. This ICS decision triggered a protest among Quaternary geologists, members of INQUA, and became the subject of much controversy. This article provides a comprehensive analysis of the Quaternary problem and proposes a reasonable scientific solution that may be appropriate for both parties. The subject of Late Cenozoic geology is discussed: glaciations, human evolution, and recent deposits. In contrast to Charles Lyell's definition of the Plio-Pleistocene according to the percentage of modern mollusk species, it is defined here as a blanket formation, which is correlative to the topography and consists of mapped stratogens hosting fossils of modern biogeocenoses. Features of the description of the Plio-Pleistocene in terms of gravitational orbital tuning are considered. Four paleogeographic phases of modern environment evolution are recognized and ranked as stages: (1) The Messinian evolutionary explosion involved the appearance of many biogeocenoses and the bipedal walking of our extinct ancestors armed with sticks. It was a consequence of the Early Greenland (7.6 Ma BP) and Patagonian (6.7 Ma BP) hyperglaciations. (2) The Zanclean age is marked by climatic and hydrological but not evolutionary boundaries. (3) The appearance of the Villafranchian animal assemblage and Australopithecus, who used stones as weapon: 4.0-3.6 Ma BP. Orogeny and isolation of the Arctic Ocean changed the global climate dramatically. (4) The sexual revolution became the third evolutionary jump: the appearance of the first woman, "Eve", and the genus Homo with her: 1.9 Ma BP. According to the current view, the Plio

Global late Quaternary megafauna extinctions linked to humans, not climate change

PubMed Central

Sandom, Christopher; Faurby, Søren; Sandel, Brody; Svenning, Jens-Christian

2014-01-01

The late Quaternary megafauna extinction was a severe global-scale event. Two factors, climate change and modern humans, have received broad support as the primary drivers, but their absolute and relative importance remains controversial. To date, focus has been on the extinction chronology of individual or small groups of species, specific geographical regions or macroscale studies at very coarse geographical and taxonomic resolution, limiting the possibility of adequately testing the proposed hypotheses. We present, to our knowledge, the first global analysis of this extinction based on comprehensive country-level data on the geographical distribution of all large mammal species (more than or equal to 10 kg) that have gone globally or continentally extinct between the beginning of the Last Interglacial at 132 000 years BP and the late Holocene 1000 years BP, testing the relative roles played by glacial–interglacial climate change and humans. We show that the severity of extinction is strongly tied to hominin palaeobiogeography, with at most a weak, Eurasia-specific link to climate change. This first species-level macroscale analysis at relatively high geographical resolution provides strong support for modern humans as the primary driver of the worldwide megafauna losses during the late Quaternary. PMID:24898370

Impact of glaciations on the long-term erosion in Southern Patagonian Andes

NASA Astrophysics Data System (ADS)

Simon-Labric, Thibaud; Herman, Frederic; Baumgartner, Lukas; Shuster, David L.; Braun, Jean; Reiners, Pete W.; Valla, Pierre G.; Leuthold, Julien

2014-05-01

The Southern Patagonian Andes are an ideal setting to study the impact of Late-Cenozoic climate cooling and onset of glaciations impact on the erosional history of mountain belts. The lack of tectonic activity during the last ~12 Myr makes the denudation history mainly controlled by surface processes, not by tectonics. Moreover, the glaciations history of Patagonia shows the best-preserved records within the southern hemisphere (with the exception of Antarctica). Indeed, the dry climate on the leeward side of Patagonia and the presence of lava flows interbedded with glacial deposits has allowed an exceptional preservation of late Cenozoic moraines with precise dating using K-Ar analyses on lava flow. The chronology of moraines reveals a long history covering all the Quaternary, Pliocene, and up to the Upper Miocene. The early growth of large glaciers flowing on eastern foothills started at ~7-6 Myr, while the maximum ice-sheet extent dates from approximately 1.1 Myr. In order to quantify the erosion history of the Southern Patagonian Andes and compare it to the glaciations sediment record, we collected samples along an age-elevation profile for low-temperature thermochronology in the eastern side of the mountain belt (Torres del Paine massif). The (U-Th)/He age-elevation relationship shows a clear convex shape providing an apparent long-term exhumation rate of ~0.2 km/Myr followed by an exhumation rate increase at ~6 Myr. Preliminary results of 4He/3He thermochronometry for a subset of samples complete the erosion history for the Plio-Pleistocene epoch. We used inverse procedure predicting 4He distributions within an apatite grain using a radiation-damage and annealing model to quantify He-diffusion kinetics in apatite. The model also allows quantifying the impact of potential U-Th zonation throughout each apatite crystal. Inversion results reveal a denudation history composed by a pulse of denudation at ~6 Ma, as suggested by the age-elevation relationship

Quantifying Late Quaternary Deformation along the Santa Ynez River, Santa Maria Basin, California

NASA Astrophysics Data System (ADS)

Slatten, C. L.; Onderdonk, N.

2017-12-01

The fault bounded Santa Maria Basin, located on the Central Coast of California, is positioned in an area of convergence between the rotating Western Transverse Ranges and the non-rotated Southern Coast Ranges. The Santa Ynez River Fault (SYRF) is an east-west trending fault that parallels the Santa Ynez River west of Lake Cachuma, California and defines the southern structural boundary of the Santa Maria Basin. However, the rate and style of Late Quaternary deformation and uplift in this region and the potential for seismic hazard along the fault is lacking. Fluvial terraces are key geomorphological components of fluvial systems that can be used to provide insights into regional and local uplift and deformation. The Santa Ynez River delineates the northern edge of the Santa Ynez Mountains and flows west through the Santa Ynez Valley to its mouth at the Pacific Ocean. The Santa Ynez River Field Area is a 10 km stretch of the Santa Ynez River just west of Lake Cachuma where terraces are well developed and the SYRF cuts through terraces and the active river (Figure 1). If there has been Quaternary movement of the SYRF we expect to find deformation in these areas. An initial survey of the area identified five terrace levels ranging from 8 m to 135 m above modern river level. The fluvial terraces are being mapped as separate units, surveyed for deformation with GPS based transects, and sampled for optically stimulated luminescence (OSL) dating. These combined methods will allow us to document the geomorphic characteristics and landform evolution of the lower Santa Ynez River, evaluate the possibility of Late Quaternary activity of the SYRF, and determine the rate of Late Quaternary regional uplift along the western Santa Ynez River in the Santa Maria Basin providing a possible basis for augmentation of the seismic hazards for Santa Barbara County.

Late Quaternary changes in intermediate water oxygenation and oxygen minimum zone, northern Japan: A benthic foraminiferal perspective

NASA Astrophysics Data System (ADS)

Shibahara, Akihiko; Ohkushi, Ken'ichi; Kennett, James P.; Ikehara, Ken

2007-09-01

A strong oxygen minimum zone (OMZ) currently exists at upper intermediate water depths on the northern Japanese margin, NW Pacific. The OMZ results largely from a combination of high surface water productivity and poor ventilation of upper intermediate waters. We investigated late Quaternary history (last 34 kyr) of ocean floor oxygenation and the OMZ using quantitative changes in benthic foraminiferal assemblages in three sediment cores taken from the continental slope off Shimokita Peninsula and Tokachi, northern Japan, at water depths between 975 and 1363 m. These cores are well located within the present-day OMZ, a region of high surface water productivity, and in close proximity to the source region of North Pacific Intermediate Water. Late Quaternary benthic foraminiferal assemblages experienced major changes in response to changes in dissolved oxygen concentration in ocean floor sediments. Foraminiferal assemblages are interpreted to represent three main groups representing oxic, suboxic, and dysoxic conditions. Assemblage changes in all three cores and hence in bottom water oxygenation coincided with late Quaternary climatic episodes, similar to that known for the southern California margin. These episodes, in turn, are correlated with orbital and millennial climate episodes in the Greenland ice core including the last glacial episode, Bølling-Ållerød (B/A), Younger Dryas, Preboreal (earliest Holocene), early Holocene, and late Holocene. The lowest oxygen conditions, marked by dysoxic taxa and laminated sediments in one core, occurred during the B/A and the Preboreal intervals. Suboxic taxa dominated mainly during the last glacial, the Younger Dryas, and most of the Holocene. Dysoxic conditions during the B/A and Preboreal intervals in this region were possibly caused by high surface water productivity at times of reduced intermediate ventilation in the northwestern Pacific. Remarkable similarities are evident in the late Quaternary sequence of benthic

Quaternary geologic map of the Shelby 1° x 2° quadrangle, Montana

USGS Publications Warehouse

Fullerton, David S.; Colton, Roger B.; Bush, Charles A.

2013-01-01

The Shelby quadrangle encompasses approximately 16,084 km2 (6,210 mi2). The northern boundary is the Montana/Saskatchewan (U.S./Canada) boundary. The quadrangle is in the Northern Plains physiographic province and it includes the Sweet Grass Hills. The primary river is the Marias River. The ancestral Missouri River was diverted south of the Bearpaw Mountains by a Laurentide ice sheet. The fill in the buried ancestral valleys of the Missouri River and Marias River in the southeast quarter of the quadrangle contains a complex stratigraphy of fluvial, glaciofluvial, ice-contact, glacial, lacustrine, and eolian deposits. The map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (for example, ground-moraine deposits, end-moraine deposits, stagnation-moraine deposits, all composed of till) are distinguished for purposes of reconstruction of glacial history. Surficial deposits and materials are assigned to 21 map units on the basis of genesis, age, lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in pedology or agronomy. Rather, it is a generalized map of soils recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. Glaciotectonic (ice-thrust) structures and deposits are mapped separately, represented by a symbol. On the glaciated plains, the surficial deposits are glacial, ice-contact, glaciofluvial, alluvial, lacustrine, eolian, colluvial, and mass-movement deposits. In the Sweet Grass Hills, beyond the limit of Quaternary glaciation they are fluvial, colluvial, and mass-movement deposits. Till of late Wisconsin age is represented by three map units. Tills of Illinoian and pre-Illinoian glaciations are not mapped, but are widespread in the subsurface. Linear ice-molded landforms (primarily drumlins) indicate directions of ice flow

Response to “Comment on 'The transition on North America from the warm humid Pliocene to the glaciated Quaternary traced by eolian dust deposition at a benchmark North Atlantic Ocean drill site', by David Lang et al.”

NASA Astrophysics Data System (ADS)

Lang, David C.; Bailey, Ian; Wilson, Paul A.; Foster, Gavin L.; Bolton, Clara T.; Friedrich, Oliver; Gutjahr, Marcus

2014-11-01

In volume 93 of Quaternary Science Reviews we published a new record of terrigenous inputs to Integrated Ocean Drilling Program (IODP) Site U1313 that tracks the history of aeolian dust deposition in the North Atlantic Ocean and aridity on North America during the late Pliocene-earliest Pleistocene intensification of northern hemisphere glaciation (iNHG, 3.3 to 2.4 Ma). Naafs et al. (2014) are generally supportive but question one of our conclusions, specifically our argument that "glacial grinding and transport of fine grained sediments to mid latitude outwash plains is not the fundamental mechanism controlling the magnitude of the flux of higher plant leaf waxes from North America to Site U1313 during iNHG." They suggest that our argument is predominantly based on our observation that the relationship between sediment lightness (L*)-based terrigenous inputs and dust-derived biomarkers, which is observed to be linear elsewhere (Martínez-Garcia et al., 2011), is non-linear at Site U1313.

Late Quaternary uplift rate across the Shimokita peninsula, northeastern Japan forearc

NASA Astrophysics Data System (ADS)

Matsu'Ura, T.

2009-12-01

I estimated the late Quaternary uplift rate across the northeastern Japan forearc (Shimokita peninsula) by using the height distribution of MIS 5.5 marine terraces as determined from tephra and cryptotephra stratigraphy. The heights of inner-margins (shoreline angles) of the MIS 5.5 marine terrace surface were previously reported to be 43-45 m and 30 m around Shiriyazaki and Gamanosawa, respectively. These heights decrease westward and are possibly due to a west-dipping offshore fault. But in some places, the heights of terrace inner-margins are probably overestimated by thick sediments. I found the MIS 5.5 wave-cut platform which is overlain by gravels and loess deposits containing a basal Toya tephra horizon (MIS 5.4) at Shiriyazaki by boring. The MIS 5.5 wave-cut platform (paleo sea level) is about 25 m above sea level, nearly half of the reported height of the terrace inner-margin. My result shows that the late Quaternary uplift rate across the Shimokita peninsula should be reconsidered. Further studies are also required whether or not the intra-plate (offshore) fault is a factor of the forearc uplifting at the peninsula. This research project has been conducted under the research contract with Nuclear and Industrial Safety Agency (NISA).

Late-Quaternary glaciation and postglacial emergence, southern Eureka Sound, high-Arctic Canada

NASA Astrophysics Data System (ADS)

O Cofaigh, Colm Seamus

Eureka Sound is the inter-island channel separating Ellesmere and Axel Heiberg islands, High Arctic Canada. This thesis reconstructs the glacial and sea level history of southern Eureka Sound through surficial geological mapping, studies of glacial sedimentology and geomorphology, surveying of raised marine shorelines, radiocarbon dating of marine shells and driftwood and surface exposure dating of erratics and bedrock. Granite dispersal trains, shelly till and ice-moulded bedrock record westerly-flow of warm-based, regional ice into Eureka Sound from a source on southeastern Ellesmere Island during the late Wisconsinan. Regional ice was coalescent with local ice domes over Raanes and northern Svendsen peninsulas. Marine limit (dating <=9.2 ka BP; <=9.9 ka cal BP) is inset into the dispersal trains and records early Holocene deglaciation of regional ice. Collectively these data indicate an extensive ice-cover in southern Eureka Sound during the Last Glacial Maximum. Ice-divides were located along the highlands of central Ellesmere and Axel Heiberg islands, from which ice converged on Eureka Sound, and subsequently flowed north and south along the channel. Deglaciation was characterised by a two-step retreat pattern, likely triggered by eustatic sea level rise and abrupt early Holocene warming. Initial break-up and radial retreat of ice in Eureka Sound and the larger fiords, preceded terrestrial stabilisation along coastlines and inner fiords. Location of deglacial depocentres was predominantly controlled by fiord bathymetry. Regionally, two-step deglaciation is reflected by prominent contrasts in glacial geomorphology between the inner and outer parts of many fiords. Glacial sedimentological and geomorphological evidence indicates spatial variation in basal thermal regime between retreating trunk glaciers. Holocene emergence of up to 150 m asl along southern Eureka Sound is recorded by raised marine deltas, beaches and washing limits. Emergence curves exhibit

Late Frasnian-Famennian climates based on palynomorph analyses and the question of the Late Devonian glaciations

NASA Astrophysics Data System (ADS)

Streel, Maurice; Caputo, Mário V.; Loboziak, Stanislas; Melo, José Henrique G.

2000-11-01

have alternated with less cold but wetter climates, thus giving rise to the development of mountain glaciers in high latitudes and explaining the jerking character of the global major marine regression. In high latitude regions, the development of an ice cap reaching sea level is only recorded by the end of the Latest Famennian, immediately below the DCB but, even if glacial evidences are not known at near the FFB, a short (0.1 Ma?) glaciation seems the best reasonable explanation of the major eustatic fall following the Kellwasser Event. The sudden growth and decay of a hypothetical Earliest Famennian ice sheet can be explained by the reduction and, later, increase in greenhouse capacity of the atmosphere. These changes in the atmospheric CO 2 might have provoked changes in the mode of ocean-atmosphere operation. It may also be partly controlled by a volcanic paroxysm and/or bolide impacts. The Hony microtektites represent the best known evidence of the impact of extraterrestrial bodies on Earth corresponding to the UKW, and they are immediately followed by a regression, suggested by the quantitative analysis of acritarch assemblages. In the paleo-tropical Late Famennian, a peat-forming vascular plant community occurs for the first time and makes possible quantitative palynology of autochthonous sediments allowing the recognition of different swamp and near-swamp characteristic miospores. The early Latest Famennian starts with a widespread transgression which could correspond to the melting phases of the hypothetical Late Famennian mountain glaciers. During the end-Famennian, the coastal lowland vegetation has a worldwide distribution from sub-polar to equatorial regions. The climate has become less cold in high latitudes but wetter than before probably because the midlatitude cyclonic activity allows sufficient polar transportation of moisture to form large snow cover. Extensive coastal glaciers developed in different Bolivian and Brazilian basins, well dated by

Late Quaternary Alluvial Fans of Southern Baja California, Mexico: Relation to Eastern Pacific Tropical Cyclones

NASA Astrophysics Data System (ADS)

Antinao, J.; McDonald, E.

2009-12-01

In the arid, non-glaciated regions of the Southwestern USA and Northwestern Mexico, aggradation in alluvial fan systems has been traditionally linked to cold and humid periods (e.g., Last Glacial Maximum) or to the transition to warm periods (e.g., the Pleistocene-Holocene transition, PHT). However, major intervals of sediment transport and aggradation have also occurred during climatically warm periods in these regions. These periods have also been identified as portraying enhanced humidity or “monsoonal’ conditions. Investigations on the weather systems able to perform geomorphic work during predominantly warm periods, i.e. the North American Monsoon (NAM) and Eastern Pacific (EP) Tropical Cyclones (TCs), have concentrated mainly in the USA. To understand the relative contribution of these systems to sediment transport over millennial timescales, we have mapped and characterized preliminarily the alluvial fans in four different areas of the Southern Baja California peninsula, Mexico. This region is dominated by EPTC precipitation, which in turn is driving the sediment transport along alluvial channels. Detailed geomorphologic mapping shows that a distinct Late Quaternary chronostratigraphy of alluvial fan units can be developed using geochronological and pedological tools. Specifically, a soil chronosequence can be compared to sequences in the SW USA, allowing a correlation to Late Pleistocene - Holocene events in the region. At least five alluvial units can be identified. Older units have well defined gravel pediments, Av and B horizons and pervasive pedogenic carbonate morphology, with alluvial terraces that rise tens of meters above the present channel. Intermediate age units have developed B horizons and carbonate morphology at different stages. The younger units have thin soil horizons, no carbonate morphology in the soil profile, and some of them are subject to episodic flooding during TC activity. The chronosequence developed is the first step towards

Late Quaternary faulting in the Cabo San Lucas-La Paz Region, Baja California

NASA Astrophysics Data System (ADS)

Busch, M.; Arrowsmith, J. R.; Umhoefer, P. J.; Gutiérrez, G. M.; Toke, N.; Brothers, D.; Dimaggio, E.; Maloney, S.; Zielke, O.; Buchanan, B.

2006-12-01

While Baja California drifts, active deformation on and just offshore indicates that spreading is not completely localized to the rift axis in the Gulf of California. Using on and offshore data, we characterize normal faulting- related deformation in the Cabo San Lucas-La Paz area. We mapped sections of the north trending faults in a 150 km long left-stepping fault array. Starting in the south, the San Jose del Cabo fault (east dipping) bounds the ~2 km high Sierra La Laguna. It is >70 km long with well defined 1-10 meter fault scarps cutting the youngest late Quaternary geomorphic surfaces. Our preliminary mapping along the north central section exhibits extensive late Quaternary terraces with riser heights of tens of meters above Holocene terraces. The San Jose del Cabo fault trace becomes diffuse and terminates in the area of Los Barriles. Moving northward, the fault system steps to the west, apparently transferring slip to the faults of San Juan de Los Planes and Saltito, which then step left again across the La Paz basin to the NNW trending Carrizal Fault. It has an on shore length of > 60 km. We produced a 25 km detailed strip map along the northern segment. It is embayed by convex east arcs several km long and 100 m deep. In the south, few-m-high scarps cut a pediment of thin Quaternary cover over tertiary volcanic rocks. The escarpment along the fault is hundreds of meters high and scarps 1-10 m high where it goes offshore in the north. Near Bonfil, a quarry cut exposes the fault zone. It comprises a 5-10 m wide bedrock shear zone with sheared tertiary volcanic units. On the footwall, the lower silty and sandy units have moderately well developed pedogenic carbonate, whereas the upper coarse gravel does not. These late Quaternary units appear to be faulted by one to three earthquakes. Finally, we mapped the Saltito fault zone NNE of La Paz. It is a NW trending structure with well developed 5- 10 meter high bedrock scarps defining its NW 5 km and slightly

A major change in precipitation gradient on the Chinese Loess Plateau at the Pliocene-Quaternary boundary

NASA Astrophysics Data System (ADS)

Peng, Wenbin; Nie, Junsheng; Wang, Zhao; Qiang, Xiaoke; Garzanti, Eduardo; Pfaff, Katharina; Song, Yougui; Stevens, Thomas

2018-04-01

Spatiotemporal variations in East Asian Monsoon (EAM) precipitation during the Quaternary have been intensively studied. However, spatial variations in pre-Quaternary EAM precipitation remain largely uninvestigated, preventing a clear understanding of monsoon dynamics during a warmer climatic period. Here we compare the spatial differences in heavy mineral assemblages between Quaternary loess and pre-Quaternary Red Clay on the Chinese Loess Plateau (CLP) to analyze spatial patterns in weathering. Prior studies have revealed that unstable hornblende is the dominant (∼50%) heavy mineral in Chinese loess deposited over the past 500 ka, whereas hornblende content decreases to <10% in strata older than ∼1 Ma in the central CLP because of diagenesis. In the present study we found that hornblende is the dominant heavy mineral in 2-2.7 Ma loess on the northeastern CLP (at Jiaxian), which today receives little precipitation. Conversely, hornblende content in the upper Miocene-Pliocene Red Clay at Jiaxian is <10%, as in the central CLP. The early Quaternary abundance of hornblende at Jiaxian indicates that the current northwestward-decreasing precipitation pattern and consequent dry climate at Jiaxian must have been initiated since ∼2.7 Ma, preventing hornblende dissolution to amounts <10% as observed in the central CLP. By contrast, the 7 Ma and 3 Ma Jiaxian Red Clay hornblende content is significantly less than that of the Xifeng samples, despite the fact that today Xifeng receives more precipitation than Jiaxian, with expected enhanced hornblende weathering. This suggests that the northeastern CLP received more precipitation during the Late Miocene-Pliocene than at Xifeng, indicating that the precipitation gradient on the CLP was more east-west during the Late Miocene-Pliocene rather than northwest-southeast as it was in the Quaternary. A comparison of magnetic susceptibility records for these sections confirms this inference. We attribute this major change in

Late Quaternary paleoseismicity and seismic potential of the Yilan-Yitong Fault Zone in NE China

NASA Astrophysics Data System (ADS)

Yu, Zhongyuan; Yin, Na; Shu, Peng; Li, Jincheng; Wei, Qinghai; Min, Wei; Zhang, Peizhen

2018-01-01

The Yilan-Yitong Fault Zone (YYFZ), which is composed of two nearly parallel branches with a spacing of 5-30 km and a length of ∼1100 km, is considered to be the key branch of the Tancheng-Lujiang Fault Zone (TLFZ) in NE China. It was traditionally believed that the YYFZ experienced weak activity or was inactive during the Late Quaternary, without the capability to generate strong earthquakes (M ≥ 7), based on the absence of typical outcrops and large historical or instrumental earthquakes (M > 6). However, our paleoseismic study shows that the YYFZ is the primary seismotectonic structure (M ≥ 7) that poses significant earthquake threats to NE China. The synthesis of data collected from geologic investigations, geomorphic mapping, trench logging and the dating of samples indicates that the YYFZ is an active structure that has undergone segmented strong tectonic deformation since the Late Quaternary with a characteristic assemblage of landforms, including linear scarps and troughs, offset or deflected streams, linear sag ponds, small horsts and grabens. The latest ruptures of the YYFZ migrated from previous boundary faults into the basin interior, forming a left-stepping en echelon pattern in plain view, and the kinematics of these events in the Late Quaternary were dominated by reverse dextral slipping. Multi-segment cluster faulting might have occurred during three cluster periods, i.e., ∼34750-35812 a BP, ∼21700-22640 a BP, and ∼4000 a BP-present, which implies that the recurrence interval of large earthquakes along the YYFZ may be as long as tens of thousands of years.

Munroa argentina, a Grass of the South American Transition Zone, Survived the Andean Uplift, Aridification and Glaciations of the Quaternary.

PubMed

Amarilla, Leonardo D; Anton, Ana M; Chiapella, Jorge O; Manifesto, María M; Angulo, Diego F; Sosa, Victoria

2015-01-01

The South American Transition Zone (SATZ) is a biogeographic area in which not only orogeny (Andes uplift) and climate events (aridification) since the mid-Miocene, but also Quaternary glaciation cycles had an important impact on the evolutionary history of the local flora. To study this effect, we selected Munroa argentina, an annual grass distributed in the biogeographic provinces of Puna, Prepuna and Monte. We collected 152 individuals from 20 localities throughout the species' range, ran genetic and demographic analyses, and applied ecological niche modeling. Phylogenetic and population genetic analyses based on cpDNA and AFLP data identified three phylogroups that correspond to the previously identified subregions within the SATZ. Molecular dating suggests that M. argentina has inhabited the SATZ since approximately 3.4 (4.2-1.2) Ma and paleomodels predict suitable climate in these areas during the Interglacial period and the Last Glacial Maximum. We conclude that the current distribution of M. argentina resulted from the fragmentation of its once continuous range and that climate oscillations promoted ecological differences that favored isolation by creating habitat discontinuity.

Munroa argentina, a Grass of the South American Transition Zone, Survived the Andean Uplift, Aridification and Glaciations of the Quaternary

PubMed Central

Amarilla, Leonardo D.; Anton, Ana M.; Chiapella, Jorge O.; Manifesto, María M.; Angulo, Diego F.; Sosa, Victoria

2015-01-01

The South American Transition Zone (SATZ) is a biogeographic area in which not only orogeny (Andes uplift) and climate events (aridification) since the mid-Miocene, but also Quaternary glaciation cycles had an important impact on the evolutionary history of the local flora. To study this effect, we selected Munroa argentina, an annual grass distributed in the biogeographic provinces of Puna, Prepuna and Monte. We collected 152 individuals from 20 localities throughout the species’ range, ran genetic and demographic analyses, and applied ecological niche modeling. Phylogenetic and population genetic analyses based on cpDNA and AFLP data identified three phylogroups that correspond to the previously identified subregions within the SATZ. Molecular dating suggests that M. argentina has inhabited the SATZ since approximately 3.4 (4.2–1.2) Ma and paleomodels predict suitable climate in these areas during the Interglacial period and the Last Glacial Maximum. We conclude that the current distribution of M. argentina resulted from the fragmentation of its once continuous range and that climate oscillations promoted ecological differences that favored isolation by creating habitat discontinuity. PMID:26110533

Phylogeographic Insights into a Peripheral Refugium: The Importance of Cumulative Effect of Glaciation on the Genetic Structure of Two Endemic Plants

PubMed Central

Zecca, Giovanni; Minuto, Luigi

2016-01-01

Quaternary glaciations and mostly last glacial maximum have shaped the contemporary distribution of many species in the Alps. However, in the Maritime and Ligurian Alps a more complex picture is suggested by the presence of many Tertiary paleoendemisms and by the divergence time between lineages in one endemic species predating the Late Pleistocene glaciation. The low number of endemic species studied limits the understanding of the processes that took place within this region. We used species distribution models and phylogeographical methods to infer glacial refugia and to reconstruct the phylogeographical pattern of Silene cordifolia All. and Viola argenteria Moraldo & Forneris. The predicted suitable area for last glacial maximum roughly fitted current known distribution. Our results suggest that separation of the major clades predates the last glacial maximum and the following repeated glacial and interglacial periods probably drove differentiations. The complex phylogeographical pattern observed in the study species suggests that both populations and genotypes extinction was minimal during the last glacial maximum, probably due to the low impact of glaciations and to topographic complexity in this area. This study underlines the importance of cumulative effect of previous glacial cycles in shaping the genetic structure of plant species in Maritime and Ligurian Alps, as expected for a Mediterranean mountain region more than for an Alpine region. PMID:27870888

Eolian sediment responses to late Quaternary climate changes: Temporal and spatial patterns in the Sahara

USGS Publications Warehouse

Swezey, C.

2001-01-01

This paper presents a compilation of eolian-based records of late Quaternary climate changes in the Sahara. Although the data are relatively sparse, when viewed as a whole, they reveal a general pattern of widespread eolian sediment mobilization prior to 11,000 cal. years BP, eolian sediment stabilization from 11,000 to 5000 cal. years BP, and a return to widespread eolian sediment mobilization after 5000 cal. years BP. Furthermore, an eolian-based record from southern Tunisia reveals the existence of millennial-scale changes in eolian sediment behavior. These millennial-scale variations provide examples of eolian sediment responses to climate changes at a scale intermediate between seasonal and orbital ('Milankovitch') changes, and they are also coincident with abrupt atmospheric and oceanic changes. The general synchroneity of the eolian stratigraphic records and their coincidence with various oceanic and atmospheric changes suggest that global forcing mechanisms have influenced late Quaternary eolian sediment behavior in the Sahara. ?? 2001 Elsevier Science B.V.

Possible refugia in the Alexander Archipelago of southeastern Alaska during the late Wisconsin glaciation

USGS Publications Warehouse

Carrara, P.E.; Ager, T.A.; Baichtal, J.F.

2007-01-01

The interpretation of the extent of late Wisconsin glaciation in southeastern Alaska has varied between geologists and biologists. Maps and reports of the region prepared by geologists commonly indicated that late Wisconsin ice extended as a large uniform front west to the edge of the continental shelf. However, the distribution of plants and animals in the region has led many biologists to suggest that there may have been ice-free areas that served as refugia during the late Wisconsin. Based on analyses of aerial photographs, topographic maps, and bathymetric charts, in conjunction with a review of previous literature and reconnaissance fieldwork throughout the region, this study presents data supporting a limited ice extent in the Alexander Archipelago during the late Wisconsin and identifies possible ice-free areas that may have served as refugia. These areas include (1) the Fairweather Ground, (2) the Herbert Graves Island area, (3) the western coast of southern Baranof Island and adjacent continental shelf, (4) Coronation Island and the adjacent continental shelf, (5) the Warren Island area, (6) the continental shelf from west of Heceta Island to Forrester Island in the south, (7) parts of the west coast of southern Dall Island, and (8) lowland areas in southern Prince of Wales Island. The identification of these possible refugia has bearing on the recolonization of the Alexander Archipelago, as they could have served as centers of biotic dispersal upon regional deglaciation and as stepping stones for early humans with a maritime tradition entering the western hemisphere from Asia. ?? 2007 NRC Canada.

Regional variations in provenance and abundance of ice-rafted clasts in Arctic Ocean sediments: Implications for the configuration of late Quaternary oceanic and atmospheric circulation in the Arctic

USGS Publications Warehouse

Phillips, R.L.; Grantz, A.

2001-01-01

The composition and distribution of ice-rafted glacial erratics in late Quaternary sediments define the major current systems of the Arctic Ocean and identify two distinct continental sources for the erratics. In the southern Amerasia basin up to 70% of the erratics are dolostones and limestones (the Amerasia suite) that originated in the carbonate-rich Paleozoic terranes of the Canadian Arctic Islands. These clasts reached the Arctic Ocean in glaciers and were ice-rafted to the core sites in the clockwise Beaufort Gyre. The concentration of erratics decreases northward by 98% along the trend of the gyre from southeastern Canada basin to Makarov basin. The concentration of erratics then triples across the Makarov basin flank of Lomonosov Ridge and siltstone, sandstone and siliceous clasts become dominant in cores from the ridge and the Eurasia basin (the Eurasia suite). The bedrock source for the siltstone and sandstone clasts is uncertain, but bedrock distribution and the distribution of glaciation in northern Eurasia suggest the Taymyr Peninsula-Kara Sea regions. The pattern of clast distribution in the Arctic Ocean sediments and the sharp northward decrease in concentration of clasts of Canadian Arctic Island provenance in the Amerasia basin support the conclusion that the modem circulation pattern of the Arctic Ocean, with the Beaufort Gyre dominant in the Amerasia basin and the Transpolar drift dominant in the Eurasia basin, has controlled both sea-ice and glacial iceberg drift in the Arctic Ocean during interglacial intervals since at least the late Pleistocene. The abruptness of the change in both clast composition and concentration on the Makarov basin flank of Lomonosov Ridge also suggests that the boundary between the Beaufort Gyre and the Transpolar Drift has been relatively stable during interglacials since that time. Because the Beaufort Gyre is wind-driven our data, in conjunction with the westerly directed orientation of sand dunes that formed during

Geochemical evidence for the origin of late Quaternary loess in central Alaska

USGS Publications Warehouse

Muhs, D.R.; Budahn, J.R.

2006-01-01

Loess is extensive in central Alaska, but there are uncertainties about its source and the direction of paleo-winds that deposited it. Both northerly and southerly winds have been inferred. The most likely sources of loess are the Tanana River (south), the Nenana River (southeast), and the Yukon River (north). Late Quaternary loess in central Alaska has immobile trace-element compositions (Cr/Sc, Th/Ta, Th/ Sc, Th/U, Eu/Eu*, GdN/YbN) that indicate derivation mostly from the Tanana River. However, other ratios (As/Sb, Zr/Hf, LaN/YbN) and quantitative modeling indicate that the Yukon River was also a source. During the last glacial period, there may have been a longer residence time of the Siberian and Canadian high-pressure cells, along with a strengthened Aleutian low-pressure cell. This would have generated regional-scale northeasterly winds and explains derivation of loess from the Yukon River. However, superim-posed upon this synoptic-scale circulation, there may have been strong, southerly katabatic winds from expanded glaciers on the northern flank of the Alaska Range. These winds could have provided eolian silt from the Tanana River. Yukon River and Tanana River sediments are highly calcareous, whereas Fairbanks-area loess is not. This suggests that carbonate leaching in loess kept ahead of sedimentation and that late Quaternary loess in central Alaska was deposited relatively slowly. ?? 2006 NRC Canada.

Human Dispersals Along the African Rift Valley in the Late Quaternary

NASA Astrophysics Data System (ADS)

Tryon, C. A.; Faith, J. T.; Peppe, D. J.

2014-12-01

Climate- and tectonic-driven environmental dynamics of the East African Rift System (EARS) during the Quaternary played an important role in the demographic history of early Homo sapiens, including expansions of modern humans across and out of Africa. Human forager population size, geographic range, and behaviors such as hunting strategies and residential mobility likely varied in response to changes in the local and regional environment. Throughout the Quaternary, floral and faunal change was linked at least in part to variations in moisture availability, temperature, and atmospheric CO2, which in addition to uplift and faulting, contributed to the expansion and contraction of a number of large lakes that served as biogeographic barriers to many taxa. This is particularly clear for the Lake Victoria basin, where biogeographic, geological, and paleontological evidence documents repeated expansion and contraction of the ranges of species in response to lake level and vegetation change. Across much of eastern Africa, the topography of the rift facilitated north-south dispersals, the timing of which may have depended in part on the expansion and contraction of the equatorial forest belt. Dispersal potential likely increased during the more arid periods of the late Quaternary, when the roles of lakes and forests as dispersal barriers was reduced and the extent of low net primary productivity dry grasslands increased, the latter requiring large home ranges for human foragers, conditions suitable for range expansions within H. sapiens.

Quaternary geologic map of the Havre 1° x 2° quadrangle

USGS Publications Warehouse

Compilations by Fullerton, David S.; Colton, Roger B.; Bush, Charles A.

2012-01-01

The Havre quadrangle encompasses approximately 16,084 km2 (6,210 mi2). The northern boundary is the Montana/Saskatchewan (U.S./Canada) boundary. The quadrangle is in the Northern Plains physiographic province and it includes parts of the Bearpaw Mountains, the Little Rocky Mountains, and the Boundary Plateau. The primary river is the Milk River. The ancestral Missouri River was diverted south of the Bearpaw Mountains by a Laurentide ice sheet. The fill in the buried ancestral valley at and southwest of Havre contains a complex stratigraphy of fluvial, glaciofluvial, ice-contact, glacial, lacustrine, and eolian deposits. The old valley east of Havre now is occupied by the Milk River. The map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (e.g., ground-moraine deposits, end-moraine deposits, stagnation-moraine deposits, all composed of till) are distinguished for purposes of reconstruction of glacial history. Surficial deposits and materials are assigned to 24 map units on the basis of genesis, age, lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. Glaciotectonic (ice-thrust) structures and deposits are mapped separately, represented by a symbol. On the glaciated plains and on the Boundary Plateau the surficial deposits are glacial, ice-contact, glaciofluvial, catastrophic flood, alluvial, lacustrine, eolian, and colluvial deposits. In the Bearpaw Mountains and Little Rocky Mountains beyond the limit of Quaternary glaciation they are fluvial, colluvial, and mass-wasting deposits and residual materials. Tills of late Wisconsin and Illinoian ages are represented by map units. Tills of two pre-Illinoian glaciations are not mapped but are widespread in the subsurface and are identified in

Present and past denudation rates in the central Tianshan (Central Asia): impact of the Quaternary glaciations?

NASA Astrophysics Data System (ADS)

Charreau, J.; Puchol, N.; Blard, P.; Braucher, R.; Leanni, L.; Bourles, D. L.; Graveleau, F.; Dominguez, S.

2012-12-01

Denudation controls the mass transfer from the uplifting highlands to the lowlands basin. It impacts the isostatic compensation and hence tectonics, the rheology and may drives the Earth climate through its potential impact on atmospheric CO2. Denudation is therefore a key factor governing the evolution of the Earth's surface. Quantitative records of past denudation rates over geological time scales are thus of major importance to untangle the complex interactions between tectonics, climate and surface processes. This is particularly true at the Plio-pleistocene transition where the onset of Quaternary glaciations may have enhanced worldwide denudation rates. The Tianshan stands out as a key area to better address these problems. This range owes its impressive present high topography to the recent deformation due to the India-Asia collision and is moreover sandwiched between two large intracontinental endorheic basins where the total material eroded from the uplifting range may be deciphered from the sedimentary archive. Moreover, here, potential changes in the sediment volume are insensitive to global sea-level variations. Accurate reconstruction of past denudation rate require well-dated sedimentary archives. Over past decades, several magnetostratigraphic studies were carried out in the piedmonts, where remarkable sedimentary sections are exposed in deep rivers entrenchment which expose the thick conglomeratic Xiyu formation, initially assigned to be Plio-pleistocene in age. This led several authors to conclude that, in this region, the sediment fluxes rapidly increaseed at the onset of glaciations. However, absolute magnetostratigraphic dating unambiguously show that this formation is highly diachronous and, therefore, can't owe its origin to a climate change. Given the strong lateral facies variations, reconstruction of past denudation rates from the sedimentary archive require detailed chronostratigraphy and a knowledge of the basin geometry, both almost

Late Quaternary cooling rate constrained by multiple IRSL thermochronometers of potassium feldspars for granites from Kongur Shan, Chinese Pamir

NASA Astrophysics Data System (ADS)

Qin, Jintang; Chen, Jie; Valla, Pierre; Herman, Frédéric

2015-04-01

The Kongur Shan (East Pamir), located at the northwestern Tibetan Plateau, is one of the most active orogens on Earth, where both tectonic processes along major active faults and climatic forcing (extensive glaciers coverage) are contributing to the regional landscape evolution. The exhumation rates since late Miocene was constrained to be ~6.5 - 4.2 mm/yr. However, it is still debated whether the exhumation rate accelerated since the Quaternary, of which the climate was featured by the cyclic glaciations with periods of 100 ka and 40 ka. In this study, we tried to employ luminescence thermochronology, which is a still in developing method, to resolve the impact of glacial cycles on exhumation rate. Our study site is located ~10 km to the east of the active Kongur normal fault, along the major valley of Gez river. We sampled three granite rocks from a sub-horizontal tunnel across the granite massif; one was from the entrance of the tunnel, and other two samples were from inside of the tunnel, where the measured ambient temperature is as high as 60-70 ° C. The distances of these samples are within 2 km. Four types of IRSL signals extracted from potassium feldspars (K-feldspars) were measured for each individual sample, and the results of isothermal decay experiments indicated these signals were of different thermal stabilities. Therefore, they may serve as four thermochronometers with different closure temperature. We employ these multiple thermochronometers together for each single sample to constrain their cooling rates. Our preliminary results, which are based on the simplified luminescence model of K-feldspars, suggest that the averaged cooling rate of the last 200 ka is as high as 1.4 oC/ka, which corresponds to an exhumation rate of ~ 2.3 to 0.9 cm/yr with the geothermal gradient assumed to be 60 to 150 oC/km. It seems to imply that the glacial cycles during the Quaternary substantially accelerated the exhumation rate of granite massif of Kongur Shan.

Radiocarbon dating late Quaternary loess deposits using small terrestrial gastropod shells

USGS Publications Warehouse

Pigati, Jeff S.; McGeehin, John P.; Muhs, Daniel R.; Bettis, E. Arthur

2013-01-01

Constraining the ages and mass accumulation rates of late Quaternary loess deposits is often difficult because of the paucity of organic material typically available for 14C dating and the inherent limitations of luminescence techniques. Radiocarbon dating of small terrestrial gastropod shells may provide an alternative to these methods as fossil shells are common in loess and contain ∼12% carbon by weight. Terrestrial gastropod assemblages in loess have been used extensively to reconstruct past environmental conditions but have been largely ignored for dating purposes. Here, we present the results of a multi-faceted approach to understanding the potential for using small terrestrial gastropod shells to date loess deposits in North America. First, we compare highly resolved 14C ages of well-preserved wood and gastropod shells (Succineidae) recovered from a Holocene loess section in Alaska. Radiocarbon ages derived from the shells are nearly identical to wood and plant macrofossil ages throughout the section, which suggests that the shells behaved as closed systems with respect to carbon for at least the last 10 ka (thousands of calibrated 14C years before present). Second, we apply 14C dating of gastropod shells to late Pleistocene loess deposits in the Great Plains using stratigraphy and independent chronologies for comparison. The new shell ages require less interpretation than humic acid radiocarbon ages that are commonly used in loess studies, provide additional stratigraphic coverage to previous dating efforts, and are in correct stratigraphic order more often than their luminescence counterparts. Third, we show that Succineidae shells recovered from historic loess in the Matanuska River Valley, Alaska captured the 20th century 14C bomb spike, which suggests that the shells can be used to date late Holocene and historic-aged loess. Finally, results from Nebraska and western Iowa suggest that, similar to other materials, shell ages approaching ∼40 ka should

Epiguruk: a late Quaternary environmental record from northwestern Alaska

USGS Publications Warehouse

Hamilton, T.D.; Ashley, G.M.

1993-01-01

Epiguruk, a prominent bluff along the Kobuk River in northwestern Alaska, exposes a rich depositional record of Quaternary eolian and fluvial sand, with associated loess, paleosols, and periglacial features. Three major complexes of alluvial and eolian deposits are separated by two conspicuous organic-rich paleosols which formed during cool-moist interstadial intervals. Sediments between the two paleosols include eolian, channel, and floodplain deposits that formed during alluviation of the Kobuk River to a height of about 12m above the present level. The youngest depositional complex, which overlies the upper paleosol, is divisible into late Wisconsinan and Holocene components and into fluvial-channel, flood-plain, eolian-dune, sand-sheet, loess, and pond facies. Eolian sand from the active Kobuk sand sea overloaded the river during late Wisconsinan time, causing it to alluviate to about 13m above its modern level. The Holocene record reflects erosion and deposition by a small southern Tributary to the Kobuk River, downcutting by the Kobuk River toward its modern level, and subsequent erosion across a meander belt nearly 8km wide. 66 radiocarbon ages, many from rooted shrubs, provide a firm chronology for the past 35 k.y. at Epiguruk. -from Authors

Palynological evidence for a southward shift of the North Atlantic Current at 2.6 Ma during the intensification of late Cenozoic Northern Hemisphere glaciation

NASA Astrophysics Data System (ADS)

Hennissen, Jan A. I.; Head, Martin J.; De Schepper, Stijn; Groeneveld, Jeroen

2014-06-01

The position of the North Atlantic Current (NAC) during the intensification of Northern Hemisphere glaciation (iNHG) has been evaluated using dinoflagellate cyst assemblages and foraminiferal geochemistry from a 260 kyr interval straddling the base of the Quaternary System from two sites: eastern North Atlantic Deep Sea Drilling Project Site 610 in the path of the present NAC and central North Atlantic Integrated Ocean Drilling Program Site U1313 in the subtropical gyre. Stable isotope and foraminiferal Mg/Ca analyses confirm cooling near the marine isotope stage (MIS) G7-G6 transition (2.74 Ma). However, a continued dominance of the dinoflagellate cyst Operculodinium centrocarpum sensu Wall and Dale (1966) indicates an active NAC in the eastern North Atlantic for a further 140 kyr. At MIS 104 ( 2.60 Ma), a profound dinoflagellate cyst assemblage turnover indicates NAC shutdown in the eastern North Atlantic, implying elevated atmospheric pressure over the Arctic and a resulting shift in the westerlies that would have driven the NAC. These findings challenge recent suggestions that there was no significant southward shift of the NAC or the Arctic Front during iNHG, and reveal a fundamental climatic reorganization near the base of the Quaternary.

History of research on glaciation in the White Mountains, New Hampshire (U.S.A.)

USGS Publications Warehouse

Thompson, W.B.

1999-01-01

The glacial geology of the White Mountains in New Hampshire has been the subject of many investigations since the 1840's. A series of controversies evolved during this period. First was the question of what geologic processes were responsible for eroding the bedrock and depositing the cover of surficial sediments. By the 1860's, the concept of glaciation replaced earlier theories invoking floods and icebergs. Research in the late 1800's concerned the relative impact of continental versus local glaciation. Some workers believed that surficial deposits in northern New Hampshire were the product of valley glaciers radiating from the White Mountains, but in the early 1900's continental glaciation was established as the most important process across the region. Debate over the extent and timing of alpine glaciation in the Presidential Range has continued until recent years. The most intensely argued topic has been the manner in which the Late Wisconsinan ice sheet withdrew from the White Mountains: whether by rapid stagnation and downwastage, or by progressive retreat of a still-active ice margin. The stagnation model became popular in the 1930's and was unchallenged until the late 1900's. Following a research hiatus lasting over 40 years, renewed interest in the glacial history of the White Mountains continues to inspire additional work.

Detailed view into the dynamics of the Late Miocene glaciation episode that accompanied terrestrial evolution

NASA Astrophysics Data System (ADS)

Tzanova, A.; Herbert, T.; Lawrence, K. T.; Peterson, L.; Kelly, C. S.

2015-12-01

We focus on the period of ~ 9 - 5 Ma when an episode of notably cool temperatures corresponds to evidence of high latitude Northern Hemisphere glaciation and mid-latitude terrestrial evolution. Alkenone-based sea surface temperatures (SST) from six globally distributed sites: ODP Sites 907 and 982 in the North Atlantic, ODP Site 1088 in the South Atlantic and ODP Sites 883, 884 and 887 in the North Pacific, and the Monte dei Corvi marine section in the Mediterranean unequivocally establish a dramatic, Late Miocene cold episode that persisted over approximately 2.5 Myr. In this work we establish the timing and synchronization of temperature decrease as well as rebound at orbital timescales. All sites were notably warmer than their modern annual average at ~9 Ma and exhibit sustained cooling beginning at ~8 Ma. SSTs rebound close to ~5.9 Ma at most locations suggesting that the cooling trend that began in the Late Miocene slowed down or even reversed in some locations in the Pliocene. The newly reconstructed SSTs highlight the role of cooling and an increase in equator to pole temperature gradients in terrestrial evolution at this pivotal time.

Map showing spatial and temporal relations of mountain and continental glaciations on the Northern Plains, primarily in northern Montana and northwestern North Dakota

USGS Publications Warehouse

Fullerton, David S.; Colton, Roger B.; Bush, Charles A.; Straub, Arthur W.

2004-01-01

This report is an overview of glacial limits and glacial history on the plains in northern Montana and northeastern North Dakota (long 102?-114?W.) and also in adjacent southern Alberta and Saskatchewan, Canada. In the Rocky Mountains and on the plains adjacent to the mountains in Montana, the map also depicts spatial relations of valley glaciers and piedmont ice lobes to continental ice sheets. Glacial limits east of 102?, in the United States and also in adjacent Canada, are depicted on published maps of the U.S. Geological Survey Quaternary Geologic Atlas of the United States (I-1420) map series. The limits shown here are from data compiled for the Lethbridge, Regina, Yellowstone, and Big Horn Mountains 4? x 6? quadrangles in the Quaternary Geologic Atlas series. This geospatial database has been prepared with a degree of detail appropriate for viewing at a scale of 1:1,000,000. Because of the degree of generalization required, the map is intended for regional analysis, rather than for detailed analysis in specific areas. It depicts the geographic positions of the limits of mountain and continental glaciations and the limits of selected glacial readvances. That information provides a foundation for reconstruction of geologic history and for reconstruction. The base map is simplified. Selected hydrographic features, selected towns and cities, selected physiographic features, and a grid of 1? x 2? topographic quadrangles are included to aid the reader in location of the glacial limits and other features that are depicted here on other maps at different scales. Most of the geologic data were compiled at 1:250,000 scale. The nominal reading scale of the digitized map data is 1:1,000,000. Enlargement will not restore resolution that was lost by simplification or generalization of data. Accompanying illustrations show regional directions of ice movement from Canada into the United States during maximum Illinoian glaciation, during maximum late Wisconsin glaciation

Late Quaternary Compression Revealed By Surface Faults At The Western Margin of Corsica Basin (corse, France)

NASA Astrophysics Data System (ADS)

Fellin, M. G.; Picotti, V.; Zattin, M.

Corsica is a continental block located between the Ligurian-Balearic and the North Tyrrhenian Seas (Corsica basin). Recent studies indicate that from Eocene to Pliocene the structural evolution of Corsica was controlled by extensional tectonics which prob- ably continued till Holocene (Jolivet et al., 1998). New field data have been collected in the the Marana plain (Eastern Corsica), which is a subsiding area covered by allu- vial deposits. These deposits have been dated as late Quaternary by Conchon (1978) through outcrop analyses, wells, paleosoils and weathering rinds. The master fault, separating the Marana plain from the mountain range to the west, shows an extensional tectonics and a later compressional reactivation. The river network in the Marana plain area is characterized by incised meanders formed at the intersection between the rivers and the master fault. This feature is related to a river profile convexity and not to a lithological change of the bedrock. Therefore the incised meanders may be due to a recent activity of the master fault. Reverse faults cutting Wuermian deposits of the Marana plain have been observed for the first time and they indicate a late Quaternary NW-SE directed compression. This regime is in good agreement with the present day compressional stress field determined on the basis of earthquakes focal mechanism in the Ligurian Sea (Baroux et al., 2001) and it may be responsible for the reactivation of the master fault of the Marana plain. Conchon O., 1978: Quaternary studies in Corsica (France). Quaternary Research, v. 9, pp. 41-53. Jolivet L. et al., 1998: Midcrustal shear zones in postorogenic extension: ex- ample from the North Tyrrhenian Sea. J. Geoph. Res., v. 103 (B6), pp.12,123-12,160. Baroux E. et al., 2001: Analyses of the stress field in southern France from earthquakes focal mechanisms. Geophys. J. Int., v. 145, pp. 336-348.

Traces of Old Glaciations in East-central Alaska

NASA Astrophysics Data System (ADS)

Duk-Rodkin, A.; Barendregt, R. W.; Weber, F.

2001-12-01

reversed overprint. The second site may be related to an older glacial event based on the high degree of clast weathering (>90%) and the presence of a luvisol over 1m depth. Clasts at the third site are better preserved suggesting the normal magnetization of these sediments may be Brunhes age. Deeply weathered clasts and red soils (Wounded Moose Paleosol)are found on pre-Mid Pleistocene glacial drift surfaces in west-central Yukon and appear also to be present on the older drift surfaces in east-central Alaska (for example, the well developed paleosol exposed in a borrow pit at the Tok town site). The presence of relatively old (early Brunhes) glacial deposits at high elevations (third site) could be explained by tectonic uplift, however a minimum of 300m of post depositional uplift would be required to account for the present elevation of these surfaces. Evidence for the diversion of the Yukon River by the first glaciation is seen near Circle, Alaska where lower fluvial gravels free of argillites of eastern (Ogilvie Mountains) provenance, are overlain by glacial outwash gravels containing approximately 8% argillites. The lower gravels are considered Late Pliocene (Gauss) based on plant macro fossils and normal polarity, and based on the absence of argillites, are clearly preglacial. Normally magnetized Late Pliocene pre-glacial fluvial gravels, the White Channel gravels, are found in the Tintina Trench and Klondike Plateau, which are conformably overlain by the Klondike outwash gravels associated with the first glaciation.

Glacistore: Understanding Late Cenozoic Glaciation and Basin Processes for the Development of Secure Large Scale Offshore CO2 Storage (North Sea).

NASA Astrophysics Data System (ADS)

Stewart, H. A.; Barrio, M.; Akhurst, M.; Aagaard, P.; Alcalde, J.; Bauer, A.; Bradwell, T.; Cavanagh, A.; Faleide, J. I.; Furre, A. K.; Haszeldine, S.; Hjelstuen, B. O.; Holloway, S.; Johansen, H.; Johnson, G.; Kuerschner, W.; Mondol, N. H.; Querendez, E.; Ringrose, P. S.; Sejrup, H. P.; Stewart, M.; Stoddart, D.; Wilkinson, M.; Zalmstra, H.

2014-12-01

The sedimentary strata of the North Sea Basin (NSB) record the glacial and interglacial history of environmental change in the Northern Hemisphere, and are a proposed location for the engineered storage of carbon dioxide (CO2) captured from power plant and industrial sources to reduce greenhouse gas emissions. These aspects interact in the geomechanical and fluid flow domain, as ice sheet dynamics change the properties of potential seal and reservoir rocks that are the prospective geological storage strata for much of Europe's captured CO2. The intensification of the global glacial-interglacial cycle at the onset of the Pleistocene (2.5-2.7 Ma) was a critical tipping-point in Earth's recent climate history. The increased severity of glaciations at the Plio-Pleistocene boundary triggered the first development of large-scale continental ice sheets in the Northern Hemisphere. The central part of the NSB preserves a unique history of the depositional record spanning at least the last 3 Ma, which also forms the overburden and seal to the underlying CO2 reservoirs. There is good evidence that these ice sheets created strong feedback loops that subsequently affected the evolution of the Quaternary climate system through complex ocean-atmosphere-cryosphere linkages. Understanding NSB dynamics, including the role of fluids in controlling compaction, cementation, and diagenetic processes in shale-dominated basins, is essential for CO2 storage site characterisation to increase understanding and confidence in secure storage. An increased understanding of the overlying sequence will inform quantitative predictions of the performance of prospective CO2 storage sites in glaciated areas in Europe and worldwide; to include improved resolution of glacial cycles (depositional and chronological framework), characterise pore fluids, flow properties of glacial landforms within the sequence (e.g. tunnel valleys) and the geomechanical effects (quantify compaction, rock stiffness, strength

(Model) Peatlands in late Quaternary interglacials

NASA Astrophysics Data System (ADS)

Kleinen, Thomas; Brovkin, Victor

2016-04-01

Peatlands have accumulated a substantial amount of carbon, roughly 600 PgC, during the Holocene. Prior to the Holocene, there is relatively little direct evidence of peatlands, though coal deposits bear witness to a long history of peat-forming ecosystems going back to the Carboniferous. We therefore need to rely on models to investigate peatlands in times prior to the Holocene. We have developed a dynamical model of wetland extent and peat accumulation, integrated in the coupled climate carbon cycle model of intermediate complexity CLIMBER2-LPJ, in order to mechanistically model interglacial carbon cycle dynamics. This model consists of the climate model of intermediate complexity CLIMBER2 and the dynamic global vegetation model LPJ, which we have extended with modules to determine peatland extent and carbon accumulation. The model compares reasonably well to Holocene peat data. We have used this model to investigate the dynamics of atmospheric CO2 in the Holocene and two other late Quaternary interglacials, namely the Eemian, which is interesting due to its warmth, and Marine Isotope Stage 11 (MIS11), which is the longest interglacial during the last 500ka. We will also present model results of peatland extent and carbon accumulation for these interglacials. We will discuss model shortcomings and knowledge gaps currently preventing an application of the model to full glacial-interglacial cycles.

Quaternary geologic map of the Wolf Point 1° × 2° quadrangle, Montana and North Dakota

USGS Publications Warehouse

Fullerton, David S.; Colton, Roger B.; Bush, Charles A.

2016-09-08

The Wolf Point quadrangle encompasses approximately 16,084 km2 (6,210 mi2). The northern boundary is the Montana/Saskatchewan (U.S.-Canada) boundary. The quadrangle is in the Northern Plains physiographic province and it includes the Peerless Plateau and Flaxville Plain. The primary river is the Missouri River.The map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (for example, ground-moraine deposits, end-moraine deposits, and stagnation-moraine deposits, all composed of till) are distinguished for purposes of reconstruction of glacial history. Surficial deposits and materials are assigned to 23 map units on the basis of genesis, age, lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in pedology or agronomy.  Rather, it is a generalized map of soils recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed.  Glaciotectonic (ice-thrust) structures and deposits are mapped separately, represented by a symbol. The surficial deposits are glacial, ice-contact, glaciofluvial, alluvial, lacustrine, eolian, colluvial, and mass-movement deposits.Till of late Wisconsin age is represented by three map units. Till of Illinoian age also is mapped.  Till deposited during pre-Illinoian glaciations is not mapped, but is widespread in the subsurface.  Linear ice-molded landforms (primarily drumlins), shown by symbol, indicate directions of ice flow during late Wisconsin and Illinoian glaciations. The Quaternary geologic map of the Wolf Point quadrangle, northeastern Montana and North Dakota, was prepared to provide a database for compilation of a Quaternary geologic map of the Regina 4° × 6° quadrangle, United States and Canada, at scale 1:1,000,000, for the U.S. Geological Survey Quaternary Geologic Atlas of the United States map series

Final closure of Panama and the onset of northern hemisphere glaciation

NASA Astrophysics Data System (ADS)

Bartoli, G.; Sarnthein, M.; Weinelt, M.; Erlenkeuser, H.; Garbe-Schönberg, D.; Lea, D. W.

2005-08-01

The Greenland ice sheet is accepted as a key factor controlling the Quaternary "glacial scenario". However, the origin and mechanisms of major Arctic glaciation starting at 3.15 Ma and culminating at 2.74 Ma are still controversial. For this phase of intense cooling Ravelo et al. [1] [A.C. Ravelo, D.H. Andreasen, M. Lyle, A.O. Lyle, M.W. Wara, Regional climate shifts caused by gradual global cooling in the Pliocene epoch. Nature 429 (2004) 263-267.] proposed a complex gradual forcing mechanism. In contrast, our new submillennial-scale paleoceanographic records from the Pliocene North Atlantic suggest a far more precise timing and forcing for the initiation of northern hemisphere glaciation (NHG), since it was linked to a 2-3 °C surface water warming during warm stages from 2.95 to 2.82 Ma. These records support previous models [G.H. Haug, R. Tiedemann, Effect of the formation of the Isthmus of Panama on Atlantic Ocean thermohaline circulation, Nature 393 (1998) 673-676. [2

Is the extent of glaciation limited by marine gas-hydrates?

USGS Publications Warehouse

Paull, Charles K.; Ussler, William; Dillon, William P.

1991-01-01

Methane may have been released to the atmosphere during the Quaternary from Arctic shelf gas-hydrates as a result of thermal decomposition caused by climatic warming and rising sea-level; this release of methane (a greenhouse gas) may represent a positive feedback on global warming [Revelle, 1983; Kvenvolden, 1988a; Nisbet, 1990]. We consider the response to sea-level changes by the immense amount of gas-hydrate that exists in continental rise sediments, and suggest that the reverse situation may apply—that release of methane trapped in the deep-sea sediments as gas-hydrates may provide a negative feedback to advancing glaciation. Methane is likely to be released from deep-sea gas-hydrates as sea-level falls because methane gas-hydrates decompose with pressure decrease. Methane would be released to sediment pore space at shallow sub-bottom depths (100's of meters beneath the seafloor, commonly at water depths of 500 to 4,000 m) producing zones of markedly decreased sediment strength, leading to slumping [Carpenter, 1981; Kayen, 1988] and abrupt release of the gas. Methane is likely to be released to the atmosphere in spikes that become larger and more frequent as glaciation progresses. Because addition of methane to the atmosphere warms the planet, this process provides a negative feedback to glaciation, and could trigger deglaciation.

The Late Quaternary tephrostratigraphy of annually laminated sediments from Meerfelder Maar, Germany

NASA Astrophysics Data System (ADS)

Lane, Christine S.; Brauer, Achim; Martín-Puertas, Celia; Blockley, Simon P. E.; Smith, Victoria C.; Tomlinson, Emma L.

2015-08-01

The record of Late Quaternary environmental change within the sediments of Meerfelder Maar in the Eifel region of Germany is renowned for its high precision chronology, which is annually laminated throughout the Last Glacial to Interglacial transition (LGIT) and most of the Holocene. Two visible tephra layers are prominent within the floating varve chronology of Meerfelder Maar. An Early Holocene tephra layer, the Ulmener Maar Tephra (∼11,000 varve years BP), provides a tie-line of the Meerfelder Maar record to the varved Holocene record of nearby Lake Holzmaar. The Laacher See Tephra provides another prominent time marker for the late Allerød, ∼200 varve years before the transition into the Younger Dryas at 12,680 varve years BP. Further investigation has now shown that there are also 15 cryptotephra layers within the Meerfelder Maar LGIT-Holocene stratigraphy and these layers hold the potential to make direct comparisons between the Meerfelder Maar record and other palaeoenvironmental archives from across Europe and the North Atlantic. Most notable is the presence of the Vedde Ash, the most widespread Icelandic eruption known from the Late Quaternary, which occurred midway through the Younger Dryas. The Vedde Ash has also been found in the Greenland ice cores and can be used as an isochron around which the GICC05 and Meerfelder Maar annual chronologies can be compared. Near the base of the annual laminations in Meerfelder Maar a cryptotephra is found that correlates to the Neapolitan Yellow Tuff, erupted from Campi Flegrei in southern Italy, 1200 km away. This is the furthest north that the Neapolitan Yellow Tuff has been found, highlighting its importance in the construction of a European-wide tephrostratigraphic framework. The co-location of cryptotephra layers from Italian, Icelandic and Eifel volcanic sources, within such a precise chronological record, makes Meerfelder Maar one of the most important tephrostratotype records for continental Europe during

On the age of the penultimate full glaciation of New England

USGS Publications Warehouse

Oldale, R.N.; Colman, S.M.

1992-01-01

Tills that discontinuously underlie the late Wisconsinan till throughout New England represent the penultimate full glaciation of the region. In southern New England, the late Wisconsinan till and the tills that locally underlie it are informally referred to as upper and lower tills, respectively. For the most part, the ages of the lower tills are not firmly established, and regional correlations between occurrences of lower till, including those on Long Island, New York, are tenuous. Where a lower till underlies deposits having limiting middle Wisconsinan radiocarbon ages (e.g., the Montauk till member of the Manhassett Formation on Long Island at Port Washington, New York, and the lower till at New Sharon, Maine), many workers have assigned the till an early Wisconsinan age. However, lower tills throughout much of New England may be Illinoian or older in age and may correlate with a lower till exposed at Sankaty Head, Nantucket Island, Massachusetts, that is pre-Sangamonian in age. The till at Sankaty Head lies below marine beds containing marine faunas indicative of sea-water temperatures both warmer and slightly cooler than those off Nantucket today and that have uranium-thorium and amino-acid racemization (AAR) age estimates suggesting a Sangamonian age (marine oxygen-isotope stage 5).The lower till at Sankaty Head and the Montauk till member on Long Island were deposited during a full glaciation of New England that was at least as extensive as the late Wisconsinan advance of the Laurentide ice. Global ice-volume data from the marine oxygen-isotope record and the late Pleistocene eustatic sea-level record inferred from raised coral terraces support an advance of this magnitude during marine oxygenisotope stage 6, but not during stage 4.An early Wisconsinan age of the southern New England lower tills and, hence, of the penultimate glaciation there is problematic in terms of the pre-Sangamonian age of the lower till on Nantucket, and in terms of the late

Coastal Marine Terraces Define Late Quaternary Fault Activity and Deformation Within Northern East Bay Hills, San Francisco Bay Region

NASA Astrophysics Data System (ADS)

Kelson, K. I.

2004-12-01

Detailed mapping of uplifted marine platforms bordering the Carquinez Strait between Benicia and Pinole, California, provides data on the pattern and rate of late Quaternary deformation across the northern East Bay Hills. Field mapping, interpretation of early 20th-century topographic data, analysis of aerial photography, and compilation of onshore borehole data show the presence of remnants of three platforms, with back-edge elevations of about 4 m, 12 m, and 18 m. Based on U-series dates (Helley et al., 1993) and comparison of platform elevations to published sea-level curves, the 12-m-high and 18-m-high platforms correlate with substage 5e (ca. 120 ka) and stage 9 (ca. 330 ka) sea-level high stands, respectively. West of the Southhampton fault, longitudinal profiles of platform back-edges suggest that the East Bay Hills between Pinole and Vallejo have undergone block uplift at a rate of 0.05 +/- 0.01 m/ka without substantial tilting or warping. With uncertainty of <3 m, the 120 ka and 330 ka platforms are at the same elevations across the NW-striking Franklin fault. This west-vergent reverse fault previously was interpreted to have had late Pleistocene activity and to accommodate crustal shortening in the East Bay Hills. Our data indicate an absence of vertical displacement across the Franklin fault within at least the past 120ka and perhaps 330ka. In contrast, the stage 5e and 9 have up-on-the-east vertical displacement and gentle westward tilting across the N-striking Southhampton fault, with a late Pleistocene vertical slip rate of >0.02 m/ka. The northerly strike and prominent geomorphic expression of this potentially active fault differs from the Franklin fault. Our mapping of the Southhampton fault suggests that it accommodates dextral shear in the East Bay Hills, and is one of several left-stepping, en echelon N-striking faults (collectively, the "Contra Costa shear zone", CCSZ) in the East Bay Hills. Faults within this zone coincide with geomorphic

The late Quaternary decline and extinction of palms on oceanic Pacific islands

NASA Astrophysics Data System (ADS)

Prebble, M.; Dowe, J. L.

2008-12-01

Late Quaternary palaeoecological records of palm decline, extirpation and extinction are explored from the oceanic islands of the Pacific Ocean. Despite the severe reduction of faunal diversity coincidental with human colonisation of these previously uninhabited oceanic islands, relatively few plant extinctions have been recorded. At low taxonomic levels, recent faunal extinctions on oceanic islands are concentrated in larger bodied representatives of certain genera and families. Fossil and historic records of plant extinction show a similar trend with high representation of the palm family, Arecaceae. Late Holocene decline of palm pollen types is demonstrated from most islands where there are palaeoecological records including the Cook Islands, Fiji, French Polynesia, the Hawaiian Islands, the Juan Fernandez Islands and Rapanui. A strong correspondence between human impact and palm decline is measured from palynological proxies including increased concentrations of charcoal particles and pollen from cultivated plants and invasive weeds. Late Holocene extinctions or extirpations are recorded across all five of the Arecaceae subfamilies of the oceanic Pacific islands. These are most common for the genus Pritchardia but also many sedis fossil palm types were recorded representing groups lacking diagnostic morphological characters.

Reconnaissance study of late quaternary faulting along cerro GoDen fault zone, western Puerto Rico

USGS Publications Warehouse

Mann, P.; Prentice, C.S.; Hippolyte, J.-C.; Grindlay, N.R.; Abrams, L.J.; Lao-Davila, D.

2005-01-01

The Cerro GoDen fault zone is associated with a curvilinear, continuous, and prominent topographic lineament in western Puerto Rico. The fault varies in strike from northwest to west. In its westernmost section, the fault is ???500 m south of an abrupt, curvilinear mountain front separating the 270- to 361-m-high La CaDena De San Francisco range from the Rio A??asco alluvial valley. The Quaternary fault of the A??asco Valley is in alignment with the bedrock fault mapped by D. McIntyre (1971) in the Central La Plata quadrangle sheet east of A??asco Valley. Previous workers have postulated that the Cerro GoDen fault zone continues southeast from the A??asco Valley and merges with the Great Southern Puerto Rico fault zone of south-central Puerto Rico. West of the A??asco Valley, the fault continues offshore into the Mona Passage (Caribbean Sea) where it is characterized by offsets of seafloor sediments estimated to be of late Quaternary age. Using both 1:18,500 scale air photographs taken in 1936 and 1:40,000 scale photographs taken by the U.S. Department of Agriculture in 1986, we iDentified geomorphic features suggestive of Quaternary fault movement in the A??asco Valley, including aligned and Deflected drainages, apparently offset terrace risers, and mountain-facing scarps. Many of these features suggest right-lateral displacement. Mapping of Paleogene bedrock units in the uplifted La CaDena range adjacent to the Cerro GoDen fault zone reveals the main tectonic events that have culminated in late Quaternary normal-oblique displacement across the Cerro GoDen fault. Cretaceous to Eocene rocks of the La CaDena range exhibit large folds with wavelengths of several kms. The orientation of folds and analysis of fault striations within the folds indicate that the folds formed by northeast-southwest shorTening in present-day geographic coordinates. The age of Deformation is well constrained as late Eocene-early Oligocene by an angular unconformity separating folDed, Deep

Geochronology of Quaternary glaciations from the tropical Cordillera Huayhuash, Peru

NASA Astrophysics Data System (ADS)

Hall, Sarah R.; Farber, Daniel L.; Ramage, Joan M.; Rodbell, Donald T.; Finkel, Robert C.; Smith, Jacqueline A.; Mark, Bryan G.; Kassel, Christopher

2009-12-01

The Cordillera Huayhuash in the central Peruvian Andes (10.3°S, 76.9°W) is an ideal mountain range in which to study regional climate through variations in paleoglacier extents. The range trends nearly north-south with modern glaciers confined to peaks >4800 m a.s.l. Geomorphology and geochronology in the nearby Cordillera Blanca and Junin Plain reveal that the Peruvian Andes preserve a detailed record of tropical glaciation. Here, we use ASTER imagery, aerial photographs, and GPS to map and date glacial features in both the western and eastern drainages of the Cordillera Huayhuash. We have used in situ produced cosmogenic 10Be concentrations in quartz bearing erratics on moraine crests and ice-polished bedrock surfaces to develop an exposure age chronology for Pleistocene glaciation within the range. We have also collected sediment cores from moraine-dammed lakes and bogs to provide limiting 14C ages for glacial deposits. In contrast to the ranges to the north and south, most glacial features within the Cordillera Huayhuash are Lateglacial in age, however we have identified features with ages that span ˜0.2 to ˜38 ka with moraine sets marking the onset of glacier retreat at ˜0.3 ka, ˜9-10 ka, ˜13-14 ka, ˜20-22 ka, and >26 ka. The range displays a pronounced east-west variation in maximum down-valley distance from the headwall of moraine crests with considerably longer paleoglaciers in the eastern drainages. Importantly, Lateglacial paleoglaciers reached a terminal elevation of ˜4000 m a.s.l. on both sides of the Cordillera Huayhuash; suggesting that temperature may have been a dominant factor in controlling the maximum glacier extent. We suggest that valley morphology, specifically valley slope, strongly influences down-valley distance to the maximum glacier extent and potential for moraine preservation. While regionally there is an extensive record of older (>50 ka) advances to the north (Cordillera Blanca) and to the south (Junin region), the apparent

Towards Greenland Glaciation: Cumulative or Abrupt Transition?

NASA Astrophysics Data System (ADS)

Tan, N.; Ramstein, G.; Contoux, C.; Ladant, J. B.; Dumas, C.; Donnadieu, Y.

2014-12-01

The insolation evolution [Laskar 2004] from 4 to 2.5 Ma depicts a series of three summer solstice insolation minima between 2.7 and 2.6 Ma, but there are other more important summer solstice minima notably around 3.82 and 3.05 Ma. On such a time span of more than 1 Ma, data shows that there are variations in the evolution of atmospheric CO2 concentration with a local maximum around 3 Ma [Seki et al.2010; Bartoli et al. 2011], before a decrease between 3 and 2.6 Ma. The latter, suggesting an abrupt ice sheet inception around 2.7 Ma, has been shown to be a major culprit for the full Greenland Glaciation [Lunt et al. 2008]. However, a recent study [Contoux et al. 2014, in review] suggests that a lowering of CO2 is not sufficient to initiate a glaciation on Greenland and must be combined to low summer insolation, with surviving ice during insolation maximum, suggesting a cumulative process in the first place, which could further lead to full glaciation at 2.7 Ma. Through a new tri-dimensional interpolation method implemented within the asynchronous coupling between an atmosphere ocean general circulation model (IPSL-CM5A) and an ice sheet model (GRISLI), we investigate the transient evolution of Greenland ice sheet during the Pliocene to diagnose whether the ice sheet inception is an abrupt event or rather a cumulative process, involving waxing and waning of the ice sheet during several orbital cycles. ReferencesBartoli, G., Hönisch, B., & Zeebe, R. E. (2011). Atmospheric CO2 decline during the Pliocene intensification of Northern Hemisphere glaciations. Paleoceanography, 26(4). Contoux C, Dumas C, Ramstein G, Jost A, Dolan A. M. (2014) Modelling Greenland Ice sheet inception and sustainability during the late Pliocene. (in review for Earth and Planetary Science Letters.).Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., & Levrard, B. (2004). A long-term numerical solution for the insolation quantities of the Earth. Astronomy & Astrophysics, 428

Climatic, geomorphic, and archaeological implications of a late Quaternary alluvial chronology for the lower Salt River, Arizona, USA

NASA Astrophysics Data System (ADS)

Huckleberry, Gary; Onken, Jill; Graves, William M.; Wegener, Robert

2013-03-01

Recent archaeological excavations along the lower Salt River, Arizona resulted in the unexpected discovery of buried late Pleistocene soils and cultural features dating 5800-7100 cal YBP (Early Archaic), the latter representing the earliest evidence of human activity in the lower Salt River floodplain thus far identified. Because the lower Salt River floodplain has been heavily impacted by recent agriculture and urbanization and contains few stratigraphic exposures, our understanding of the river's geological history is limited. Here we present a late Quaternary alluvial chronology for a segment of the lower Salt River based on 19 accelerator mass spectrometry 14C and four optically stimulated luminescence ages obtained during two previous geoarchaeological investigations. Deposits are organized into allostratigraphic units and reveal a buried late Pleistocene terrace inset into middle-to-late Pleistocene terrace deposits. Holocene terrace fill deposits unconformably cap the late Pleistocene terrace tread in the site area, and the lower portion of this fill contains the Early Archaic archaeological features. Channel entrenchment and widening ~ 900 cal YBP eroded much of the older terrace deposits, leaving only a remnant of fill containing the buried latest Pleistocene and middle-to-late Holocene deposits preserved in the site area. Subsequent overbank deposition and channel filling associated with a braided channel system resulted in the burial of the site by a thin layer of flood sediments. Our study confirms that the lower Salt River is a complex mosaic of late Quaternary alluvium formed through vertical and lateral accretion, with isolated patches of buried soils preserved through channel avulsion. Although channel avulsion is linked to changes in sediment load and discharge and may have climatic linkages, intrinsic geomorphic and local base level controls limit direct correlations of lower Salt River stratigraphy to other large rivers in the North American

Evidence from Lake Baikal for Siberian glaciation during oxygen-isotope substage 5d

USGS Publications Warehouse

Karabanov, E.B.; Prokopenko, A.A.; Williams, D.F.; Colman, Steven M.

1998-01-01

The paleoclimatic record from bottom sediments of Lake Baikal (eastern Siberia) reveals new evidence for an abrupt and intense glaciation during the initial part of the last interglacial period (isotope substage 5d). This glaciation lasted about 12 000 yr from 117 000 to 105 000 yr BP according to correlation with the SPEC-MAP isotope chronology. Lithological and biogeochemical evidence of glaciation from Lake Baikal agrees with evidence for the advance of ice sheet in northwestern Siberia during this time period and also with cryogenic features within the strata of Kazantzevo soils in Southern Siberia. The severe 5d glaciation in Siberia was caused by dramatic cooling due to the decrease in solar insolation (as predicted by the model of insulation changes for northern Asia according to Milankovich theory) coupled with western atmospheric transport of moisture from the opea areas of Northern Atlantic and Arctic seas (which became ice-free due to the intense warming during preceeding isotope substage 5e). Other marine and continental records show evidence for cooling during 5d, but not for intense glaciation. Late Pleistocene glaciations in the Northern Hemisphere may have begun in northwestern Siberia.

Asynchronous glaciations in arid continental climate

NASA Astrophysics Data System (ADS)

Batbaatar, Jigjidsurengiin; Gillespie, Alan R.; Fink, David; Matmon, Ari; Fujioka, Toshiyuki

2018-02-01

Mountain glaciers at ∼26-19 ka, during the global Last Glacial Maximum near the end of the last 105 yr glacial cycle, are commonly considered on the basis of dating and field mapping in several well-studied areas to have been the largest of the late Quaternary and to have advanced synchronously from region to region. However, a numerical sensitivity model (Rupper and Roe, 2008) predicts that the fraction of ablation due to melting varies across Central Asia in proportion to the annual precipitation. The equilibrium-line altitude of glaciers across this region likely varies accordingly: in high altitude, cold and arid regions sublimation can ablate most of the ice, whereas glaciers fed by high precipitation cannot ablate completely due to sublimation alone, but extend downhill until higher temperatures there cause them to melt. We have conducted field studies and 10Be dating at five glaciated sites along a precipitation gradient in Mongolia to test the Rupper/Roe model. The sites are located in nearby 1.875 × 1.875° cells of the Rupper/Roe model, each with a different melt fraction, in this little-studied region. The modern environment of the sites ranges from dry subhumid in the north (47.7° N) to arid in the south (45° N). Our findings show that the maximum local advances in the dry subhumid conditions predated the global Last Glacial Maximum and were likely from MIS 3. However, we also found that at ∼8-7 ka a cirque glacier in one mountain range of the arid Gobi desert grew to a magnitude comparable to that of the local maximum extent. This Holocene maximum occurred during a regional pluvial period thousands of years after the retreat of the Pleistocene glaciers globally. This asynchronous behavior is not predicted by the prevailing and generally correct presumption that glacier advances are dominantly driven by temperature, although precipitation also plays a role. Our findings are consistent with and support the Rupper/Roe model, which calls for

Effects of late quaternary climate change on Palearctic shrews.

PubMed

Prost, Stefan; Klietmann, Johannes; van Kolfschoten, Thijs; Guralnick, Robert P; Waltari, Eric; Vrieling, Klaas; Stiller, Mathias; Nagel, Doris; Rabeder, Gernot; Hofreiter, Michael; Sommer, Robert S

2013-06-01

The Late Quaternary was a time of rapid climatic oscillations and drastic environmental changes. In general, species can respond to such changes by behavioral accommodation, distributional shifts, ecophenotypic modifications (nongenetic), evolution (genetic) or ultimately face local extinction. How those responses manifested in the past is essential for properly predicting future ones especially as the current warm phase is further intensified by rising levels of atmospheric carbon dioxide. Here, we use ancient DNA (aDNA) and morphological features in combination with ecological niche modeling (ENM) to investigate genetic and nongenetic responses of Central European Palearctic shrews to past climatic change. We show that a giant form of shrew, previously described as an extinct Pleistocene Sorex species, represents a large ecomorph of the common shrew (Sorex araneus), which was replaced by populations from a different gene-pool and with different morphology after the Pleistocene Holocene transition. We also report the presence of the cold-adapted tundra shrew (S. tundrensis) in Central Europe. This species is currently restricted to Siberia and was hitherto unknown as an element of the Pleistocene fauna of Europe. Finally, we show that there is no clear correlation between climatic oscillations within the last 50 000 years and body size in shrews and conclude that a special nonanalogous situation with regard to biodiversity and food supply in the Late Glacial may have caused the observed large body size. © 2013 Blackwell Publishing Ltd.

Ages and inferred causes of late Pleistocene glaciations on Mauna Kea, Hawai'i

USGS Publications Warehouse

Pigati, J.S.; Zreda, M.; Zweck, C.; Almasi, P.F.; Elmore, D.; Sharp, W.D.

2008-01-01

Glacial landforms on Mauna Kea, Hawai'i, show that the summit area of the volcano was covered intermittently by ice caps during the Late Pleistocene. Cosmogen 36Cl dating of terminal moraines and other glacial landforms indicates that the last two ice caps, called Older Makanaka and Younger Makanaka, retreated from their maximum positions approximately 23ka and 13ka, respectively. The margins and equilibrium line altitudes of these ice caps on the remote, tropical Pacific island were nearly identical, which would seem to imply the same mechanism for ice growth. But modelling of glacier mass balance, combined with palaeotemperature proxy data from the subtropical North Pacific, suggests that the causes of the two glacial expansions may have been different. Older Makanaka airatop Mauna Kea was likely wetter than today and cold, whereas Younger Makanaka times were slightly warmer but significantly wetter than the previous glaciation. The modelled increase in precipitation rates atop Mauna Kea during the Late Pleistocene is consistent with that near sea level inferred from pollen data, which suggests that the additional precipitation was due to more frequent and/ or intense tropical storms associated with eastward-moving cold fronts. These conditions were similar to modern La Ni??a (weak ENSO) conditions, but persisted for millennia rather than years. Increased precipitation rates and the resulting steeper temperature lapse rates created glacial conditions atop Mauna Kea in the absence of sufficient cooling at sea level, suggesting that if similar correlations existed elsewhere in the tropics, the precipitation-dependent lapse rates could reconcile the apparent difference between glacial-time cooling of the tropics at low and high altitudes. Copyright ?? 2008 John Wiley & Sons, Ltd.

Identifying the pollen of an extinct spruce species in the Late Quaternary sediments of the Tunica Hills region, south-eastern United States

USGS Publications Warehouse

Luke Mander,; Jacklyn Rodriguez,; Pietra G. Mueller,; Jackson, Stephen T.; Surangi W. Punyasena,

2014-01-01

Late Quaternary fluvial deposits in the Tunica Hills region of Louisiana and Mississippi are rich in spruce macrofossils of the extinct species Picea critchfieldii, the one recognized plant extinction of the Late Quaternary. However, the morphology of P. critchfieldii pollen is unknown, presenting a barrier to the interpretation of pollen spectra from the last glacial of North America. To address this issue, we undertook a morphometric study of Picea pollen from Tunica Hills. Morphometric data, together with qualitative observations of pollen morphology using Apotome fluorescence microscopy, indicate that Picea pollen from Tunica Hills is morphologically distinct from the pollen of P. glauca, P. mariana and P. rubens. Measurements of grain length, corpus width and corpus height indicate that Picea pollen from Tunica Hills is larger than the pollen of P. mariana and P. rubens, and is slightly larger than P. glauca pollen. We argue that the morphologically distinctive Tunica Hills Picea pollen was probably produced by the extinct spruce species P. critchfieldii. These morphological differences could be used to identify P. critchfieldii in existing and newly collected pollen records, which would refine its paleoecologic and biogeographic history and clarify the nature and timing of its extinction in the Late Quaternary.

Late Quaternary tectonic activity and lake level change in the Rukwa Rift Basin

NASA Astrophysics Data System (ADS)

Delvaux, D.; Kervyn, F.; Vittori, E.; Kajara, R. S. A.; Kilembe, E.

1998-04-01

Interpretation of remotely sensed images and air photographs, compilation of geological and topographical maps, morphostructural and fault kinematic observations and 14C dating reveal that, besides obvious climatic influences, the lake water extent and sedimentation in the closed hydrological system of Lake Rukwa is strongly influenced by tectonic processes. A series of sandy ridges, palaeolacustrine terraces and palaeounderwater delta fans are related to an Early Holocene high lake level and subsequent progressive lowering. The maximum lake level was controlled by the altitude of the watershed between the Rukwa and Tanganyika hydrological systems. Taking as reference the present elevation of the palaeolacustrine terraces around Lake Rukwa, two orders of vertical tectonic movement are evidenced: i) a general uplift centred on the Rungwe Volcanic Province between the Rukwa and Malawi Rift Basins; and ii) a tectonic northeastward tilting of the entire Rukwa Rift Basin, including the depression and rift shoulders. This is supported by the observed hydromorphological evolution. Local uplift is also induced by the development of an active fault zone in the central part of the depression, in a prolongation of the Mbeya Range-Galula Fault system. The Ufipa and Lupa Border Faults, bounding the Rukwa depression on the southwestern and northeastern sides, respectively, exert passive sedimentation control only. They appear inactive or at least less active in the Late Quaternary than during the previous rifting stage. The main Late Quaternary tectonic activity is represented by dextral strike-slip movement along the Mbeya Range-Galula Fault system, in the middle of the Rukwa Rift Basin, and by normal dip-slip movements along the Kanda Fault, in the western rift shoulder.

Widespread Antarctic glaciation during the Late Eocene

NASA Astrophysics Data System (ADS)

Carter, Andrew; Riley, Teal R.; Hillenbrand, Claus-Dieter; Rittner, Martin

2017-01-01

Marine sedimentary rocks drilled on the southeastern margin of the South Orkney microcontinent in Antarctica (Ocean Drilling Program Leg 113 Site 696) were deposited between ∼36.5 Ma to 33.6 Ma, across the Eocene-Oligocene climate transition. The recovered rocks contain abundant grains exhibiting mechanical features diagnostic of iceberg-rafted debris. Sand provenance based on a multi-proxy approach that included petrographic analysis of over 275,000 grains, detrital zircon geochronology and apatite thermochronometry rule out local sources (Antarctic Peninsula or the South Orkney Islands) for the material. Instead the ice-transported grains show a clear provenance from the southern Weddell Sea region, extending from the Ellsworth-Whitmore Mountains of West Antarctica to the coastal region of Dronning Maud Land in East Antarctica. This study provides the first evidence for a continuity of widespread glacier calving along the coastline of the southern Weddell Sea embayment at least 2.5 million yrs before the prominent oxygen isotope event at 34-33.5 Ma that is considered to mark the onset of widespread glaciation of the Antarctic continent.

The timing and extent of Quaternary glaciation of Stok, northern Zanskar Range, Transhimalaya, of northern India

NASA Astrophysics Data System (ADS)

Orr, Elizabeth N.; Owen, Lewis A.; Murari, Madhav K.; Saha, Sourav; Caffee, Marc W.

2017-05-01

The glacial history of three tributary valleys (Namlung, Gopal Kangri and Stok Kangri) of the Stok valley, south of the Indus valley in the northern sector of the Zanskar Range, northern India is characterized using geomorphic mapping and cosmogenic 10Be surface exposure dating. The new glacial chronostratigraphy for the Stok valley is the first for the northern Zanskar Range and provides insights into the spatial variability of glaciation in the Himalayan-Tibetan orogen. This framework facilitates the understanding of the nature and the timing of landscape evolution and paleoenvironmental change in the Himalayan-Tibetan orogen. At least four glacial stages are evident within each of the tributary valleys of Gopal Kangri (MG1-MG4, youngest to oldest) and Stok Kangri (MS1-MS4) that feed into the Stok valley. With the exception of the MG4 glacial advance ( 124 ka) in Gopal Kangri, the Stok valley has preserved evidence of glaciations from 50 ka to the present. Equilibrium-line altitudes and glacier reconstructions for the Stok valley and its tributaries demonstrate that glaciations have become progressively less extensive through time. Former glacier extents of the Stok region are comparable in length with glacial advances during the last glacial cycle in eastern Zanskar and in the southern Ladakh Range to the south and north of the Indus valley, respectively. Landscape evolution in the study area has occurred across numerous glacial-interglacial cycles by a combination of glacial and fluvial processes and is similar to that of the Ladakh Range.

High resolution seismic stratigraphy and sedimentological signature of the Late Quaternary deposits in the northern Western Basin (Ross Sea, Antarctica)

NASA Astrophysics Data System (ADS)

Corradi, N.; Finocchiaro, F.; Ivaldi, R.; Melis, R.; Pittà, A.

2003-04-01

The northern Western Basin is a sector of the continental shelf of the Western Ross Sea that is considered to be the natural northward extension of the Drygalski Basin by many authors. The literature provides a general model of the evolution of the basin and the recent papers propose a seismic stratigraphy for the post-Miocene sedimentation. However, the sedimentary processes during the Late Quaternary and, in particular, the Last Glacial Maximum (LGM) are still little understood (Brambati et al., 2001). In this paper we present the preliminary results of the very high-resolution seismic surveys (Sub Bottom Profiler, Huntec Deep Tow Boomer and Sparker) and their calibration with the sediment samples collected during the three Marine Geology Campaigns of the PNRA (XIII, XIV and XVII), with the scientific objective of the research to investigate the role of the East Antarctic Ice Sheet (EAIS) in the morphogenesis and deposition of the Late Quaternary sedimentary series.

Plant controls on Late Quaternary whole ecosystem structure and function.

PubMed

Jeffers, Elizabeth S; Whitehouse, Nicki J; Lister, Adrian; Plunkett, Gill; Barratt, Phil; Smyth, Emma; Lamb, Philip; Dee, Michael W; Brooks, Stephen J; Willis, Katherine J; Froyd, Cynthia A; Watson, Jenny E; Bonsall, Michael B

2018-06-01

Plants and animals influence biomass production and nutrient cycling in terrestrial ecosystems; however, their relative importance remains unclear. We assessed the extent to which mega-herbivore species controlled plant community composition and nutrient cycling, relative to other factors during and after the Late Quaternary extinction event in Britain and Ireland, when two-thirds of the region's mega-herbivore species went extinct. Warmer temperatures, plant-soil and plant-plant interactions, and reduced burning contributed to the expansion of woody plants and declining nitrogen availability in our five study ecosystems. Shrub biomass was consistently one of the strongest predictors of ecosystem change, equalling or exceeding the effects of other biotic and abiotic factors. In contrast, there was relatively little evidence for mega-herbivore control on plant community composition and nitrogen availability. The ability of plants to determine the fate of terrestrial ecosystems during periods of global environmental change may therefore be greater than previously thought. © 2018 John Wiley & Sons Ltd/CNRS.

Stratigraphic evolution of the inner continental shelf in response to late Quaternary relative sea-level change, northwestern Gulf of Maine

USGS Publications Warehouse

Barnhardt, W.A.; Belknap, D.F.; Kelley, J.T.

1997-01-01

Accumulations of deltaic and littoral sediments on the inner continental shelf of Maine, Gulf of Maine, preserve a record of postglacial sea-level changes and shoreline migrations. The depositional response of coastal environments to a cycle of regression, lowstand, and transgression was examined with seismic-reflection profiles, vibracores, and radiocarbon dates collected from sediments at the mouths of the Kennebec and Penobscot Rivers. Sequence-stratigraphie analysis of these data reveals two distinctly different successions of late Quaternary deposits that represent end members in an evolutionary model for this glaciated coast. Seaward of the Kennebec River, coarsegrained shorelines with foreset beds occur at depths of 20-60 m and outline the lobate margin of the Kennebec River paleodelta, a complex, rock-framed accumulation of glaciomarine and deltaic sediments capped by estuarine and marine deposits. Sand derived from this system today supports large barrier spits and extensive salt marshes. In contrast, the mouth of the Penobscot River is characterized by thick deposits of glaciomarine mud overlain by marine mud of Holocene age, including gas-charged zones that have locally evolved into fields of pockmarks. The distinct lack of sand and gravel seaward of the Penobscot River and its abundance seaward of the Kennebec River probably reflect differences in sediment sources and the physiography of the two watersheds. The contrasting stratigraphie framework of these systems demonstrates the importance of understanding local and regional differences in sediment supply, sea-level change, bedrock structure, and exposure to waves and tides in order to model river-mouth deposition on glaciated coasts. Evolution of shelf deposits was largely controlled by relative sea level, which locally fell from a highstand (+60 to +70 m at 14 ka) contemporary with deglaciation to a lowstand (-55 m at 10.8 ka). The sea-level lowering was accompanied by fluvial incision of older

Demographic stability and high historical connectivity explain the diversity of a savanna tree species in the Quaternary

PubMed Central

Telles, Mariana P. C.; Chaves, Lázaro J.; Lima-Ribeiro, Matheus S.; Collevatti, Rosane G.

2017-01-01

Abstract Background and Aims Cyclic glaciations were frequent throughout the Quaternary and this affected species distribution and population differentiation worldwide. The present study reconstructed the demographic history and dispersal routes of Eugenia dysenterica lineages and investigated the effects of Quaternary climate change on its spatial pattern of genetic diversity. Methods A total of 333 individuals were sampled from 23 populations and analysed by sequencing four regions of the chloroplast DNA and the internal transcribed spacer of the nuclear DNA. The analyses were performed using a multi-model inference approach based on ecological niche modelling and statistical phylogeography. Key Results Coalescent simulation showed that population stability through time is the most likely scenario. The palaeodistribution dynamics predicted by the ecological niche models revealed that the species was potentially distributed across a large area, extending over Central-Western Brazil through the last glaciation. The lineages of E. dysenterica dispersed from Central Brazil towards populations at the northern, western and south-eastern regions. A historical refugium through time may have favoured lineage dispersal and the maintenance of genetic diversity. Conclusions The results suggest that the central region of the Cerrado biome is probably the centre of distribution of E. dysenterica and that the spatial pattern of its genetic diversity may be the outcome of population stability throughout the Quaternary. The lower genetic diversity in populations in the south-eastern Cerrado biome is probably due to local climatic instability during the Quaternary. PMID:28115317

The late Quaternary history of lodgepole and jack pines

Treesearch

William B. Critchfield

1985-01-01

Lodgepole and jack pines (Pinus contorta Dougl. ex. Loud, and Pinus banksiana Lamb.), components of the North American boreal forest, have pioneering roles after major disturbances such as fire or glaciation. These species are closely related and hybridize in western Canada, but their fossil records and contemporary variation...

Lignin geochemistry of a Late Quaternary sediment core from Lake Washington

NASA Astrophysics Data System (ADS)

Hedges, John I.; Ertel, John R.; Leopold, Estella B.

1982-10-01

Long-term lignin stability and paleovegetation patterns were investigated using CuO oxidation products of sediments from an 11 m core of Late Quaternary sediment collected from the mid-basin of Lake Washington, Washington State. Relatively constant yields of lignin-derived phenols (normalized to organic carbon) from the entire core indicate minimal in situ lignin degradation over the last 13,000 years. Compositional patterns within the phenolic suite and increased corresponding yields from baseextracted sediments indicate that sedimentary lignins are present predominantly as well preserved plant tissue fragments. Abundance patterns of vanillyl, syringyl, and cinnamyl phenols record four distinct sequences within the core characterized by: (a) high concentrations of gymnosperm wood in a basal horizon of glacial flour, 11-10 m; (b) an essentially pure mixture of nonwoody angiosperm tissues in late Pleistocene sediments, 10-8 m; (c) relatively high concentrations of angiosperm woods in the bottom half of a limnic peat sequence deposited approximately 10,000-7,000 years B.P., 8-4 m; and (d) a progressive enrichment in gymnosperm woods at the expense of angiosperm woods over the last 7,000 years in the upper limnic peat, 4-0 m. Vascular plant tissues account for less than half the total sedimentary organic carbon throughout the core.

Late Quaternary Arc-parallel Extension of the Kongur Extensional System (KES), Chinese Pamir

NASA Astrophysics Data System (ADS)

Chen, J.; Schoenbohm, L. M.; Owen, L. A.; Li, W.; Yuan, Z.; Li, T.; Robinson, A. C.; Sobel, E. R.; Caffee, M. W.

2016-12-01

Recent normal and strike-slip faulting on the Pamir Plateau of the NW Tibetan Plateau has been linked to synorogenic extension, radial thrusting or oroclinal bending, or northward propagation of the Karakorum fault from its southern segment. Clearly the precise driver remains poorly understood. The 250 km long Kongur Extensional System (KES) lies along the northeastern margin of the Pamir at the western end of the Himalayan-Tibetan orogenic belt, and is part of a regional fault system, which accommodates east-west extension in the hanging wall of the active Main Pamir Thrust (MPT).To better understand the nature of extension in the Pamir and to test the existing models, late Quaternary slip rate along the KES need to be defined. We employ geomorphic mapping, dGPS surveying, and 10Be surface exposure and depth profile dating to quantify rates of fault slip using offset outwash terraces, landslides, and moraines at ten sites as strain markers to identify spatial patterns in deformation rate along the KES. Field mapping and kinematic analysis across offset features show that the overall extension direction is subhorizontal, oriented E-W.A systematic north to south decrease in late Quaternary slip magnitude and rate along the KES from 7 mm/yr at Muji to the north to less than 1 mm/yr at Dabudaer to the south. These geologic rates are consistent with geodetic rates determined by GPS data. All available geologic and geodetic data clearly show that the KES is an independent structure which accommodates east-west extension between the west Pamir Plateau and east Pamir-Tarim basin, and is not kinematically linked with the northern Karakoram fault. Recent extension of the KES is arc-parallel and likely relates to the collision between the Pamir and Tian Shan along longitude E74.4 and clockwise rotation of Tarim block.

Late Pliocene to Late Quaternary Apparent Exposure Ages from Glacial Deposits in Ak-Shyrak, Central Kyrgyz Tian Shan

NASA Astrophysics Data System (ADS)

Blomdin, R.; Harbor, J.; Stroeven, A. P.; Petrakov, D. A.; Gribenski, N.; Heyman, J.; Ivanov, M.; Caffee, M. W.; Hättestrand, C.; Lifton, N. A.; Rogozhina, I.; Usubaliev, R.

2014-12-01

The Tian Shan in central Asia is one of the world's highest mountain ranges. The 2500 km-long WSW-ENE-trending arc of mountains extends from the western Kyrgyz Republic across northwestern China and almost to the border with Mongolia. Understanding the glacial history of this vast region is important because there is a general lack of paleoclimatic data from this highly continental location, at the confluence of major climate systems, and because glaciers are sensitive monitors of climate change. We examine the glacial history of the Ak-Shyrak massif and surrounding plateaus with average altitudes of ~3500 m a.s.l. To reconstruct the glacial history of this area we use a combined approach including geomorphological mapping, and cosmogenic nuclide surface exposure dating of erratic boulders on glacial landforms. We observe large site-specific scatter in our 10Be and 26Al exposure ages. Apparent minimum surface exposure ages range from ~2 ka to ~2.5 Ma, with early Quaternary- late Pliocene apparent exposure ages relating to some of the highest 10Be concentrations ever recorded for glacial deposits. Most dated boulders, however, fall in the apparent exposure age range of 100 ka to 300 ka. Consistent with previous results from the western and central Tian Shan, none of our boulders record a global last glacial maxima expansion of glaciers, and this contrasts to data from the eastern Kyrgyz Tian Shan. This spatial variation in glacier extent might be due to differences in paleoclimate. However, local physiographic conditions (e.g. altitude, slope, aspect) or external forcing factors other than climate (e.g., landslides) may cause local or regional differences in glacier response. We refrain from assigning mapped glacial advances to marine oxygen isotope stages because of the considerable age scatter. Finally we assess and discuss possible reasons for the observed age scatter and early Quaternary-late Pliocene apparent exposure ages in terms of prior and/or incomplete

Pleistocene glaciation of Fenland, England, and its implications for evolution of the region

PubMed Central

West, R. G.; Hughes, P. D.

2018-01-01

Detailed investigation of landforms and their underlying deposits on the eastern margin of Fenland, East Anglia, demonstrated that they represent a series of glaciofluvial delta-fan and related sediments. Associated with these deposits are glacially dislocated sediments including tills, meltwater and pre-existing fluvial sediments. These ‘Skertchly Line’ deposits occur in the context of a substantial ice lobe that entered Fenland from the N to NE, dammed the streams entering the basin and caused glacial lakes to form in the valleys on the margins. Bulldozing by the ice lobe caused a series of ice-pushed ridges to form at the dynamic margin, especially at the ice maximum and during its retreat phases. Meltwater formed a series of marginal fans that coalesced into marginal accumulations in the SE of the basin. The ice lobe is named the Tottenhill glaciation. Further investigations of the Fenland margin have revealed the extent of the Tottenhill glaciation in the Fenland Basin, to the south and west, in sufficient detail to demonstrate the nature of the Tottenhill ice lobe and the landscape left on deglaciation. The ice lobe is likely to have been prone to surging. This is indicated by the low gradient of the ice lobe, the presence of underlying ductile Mesozoic clays, the evidence of ice-marginal flooding and the presence of arcuate glaciotectonic push moraines. Regional correlation, supported by independent numerical geochronology, indicates that the glaciation occurred ca 160 ka, i.e. during the late Middle Pleistocene, Marine Isotope Stage (MIS) 6, the Wolstonian Stage. Comparison and correlation across the southern North Sea Basin confirms that the glaciation is the equivalent of that during the Late Saalian Drenthe Stadial in The Netherlands. The implications of this correlation are presented. Before the glaciation occurred, the Fenland Basin did not exist. It appears to have been initiated by a subglacial tunnel valley system beneath the Anglian

Pleistocene glaciation of Fenland, England, and its implications for evolution of the region.

PubMed

Gibbard, P L; West, R G; Hughes, P D

2018-01-01

Detailed investigation of landforms and their underlying deposits on the eastern margin of Fenland, East Anglia, demonstrated that they represent a series of glaciofluvial delta-fan and related sediments. Associated with these deposits are glacially dislocated sediments including tills, meltwater and pre-existing fluvial sediments. These 'Skertchly Line' deposits occur in the context of a substantial ice lobe that entered Fenland from the N to NE, dammed the streams entering the basin and caused glacial lakes to form in the valleys on the margins. Bulldozing by the ice lobe caused a series of ice-pushed ridges to form at the dynamic margin, especially at the ice maximum and during its retreat phases. Meltwater formed a series of marginal fans that coalesced into marginal accumulations in the SE of the basin. The ice lobe is named the Tottenhill glaciation. Further investigations of the Fenland margin have revealed the extent of the Tottenhill glaciation in the Fenland Basin, to the south and west, in sufficient detail to demonstrate the nature of the Tottenhill ice lobe and the landscape left on deglaciation. The ice lobe is likely to have been prone to surging. This is indicated by the low gradient of the ice lobe, the presence of underlying ductile Mesozoic clays, the evidence of ice-marginal flooding and the presence of arcuate glaciotectonic push moraines. Regional correlation, supported by independent numerical geochronology, indicates that the glaciation occurred ca 160 ka, i.e. during the late Middle Pleistocene, Marine Isotope Stage (MIS) 6, the Wolstonian Stage. Comparison and correlation across the southern North Sea Basin confirms that the glaciation is the equivalent of that during the Late Saalian Drenthe Stadial in The Netherlands. The implications of this correlation are presented. Before the glaciation occurred, the Fenland Basin did not exist. It appears to have been initiated by a subglacial tunnel valley system beneath the Anglian (=Elsterian

Aleksis Dreimanis: a legacy in Quaternary science

NASA Astrophysics Data System (ADS)

Hicock, Stephen R.; Menzies, John

2000-12-01

Aleksis Dreimanis was born and raised in Latvia. His interest in Quaternary and glacial geology began early and developed into a career that has spanned 7 decades. At age 20 he published his first paper in glacial geology and soon after began teaching at the University of Latvia. Teaching and research were interrupted by World War II but resumed at the Baltic University (Pinneberg, Germany), then at the University of Western Ontario where he has been ever since. Throughout his career, Dreimanis has successfully balanced the twin disciplines of Quaternary history and glacial geology. He was among the first to study quantitatively the relationship between till lithology and till formation and to study how glacial transport and dynamics affect till texture and deformation. With co-workers he developed the well-known stratigraphic scheme of the last glaciation in the Great Lakes region of North America. Aleksis became world-renowned through his committee work, especially as President of the INQUA Commission on Genesis and Lithology of Glacial Quaternary Deposits. His diplomacy, enthusiasm, and passion for his subject have inspired students and colleagues around the globe and resulted in remarkable international dialogue, cooperation, and consensus. Professor Aleksis Dreimanis is an honest scientist, a gentleman, and a true scholar who has left a rich legacy for future Quaternarists.

The Acoustic Signature of Glaciated Margins

NASA Astrophysics Data System (ADS)

Newton, A. M. W.; Huuse, M.

2016-12-01

As climate warms it has become increasingly clear that, in order to fully understand how it might evolve in the future, we need to look for examples of how climate has changed in the past. The Late Cenozoic history of the Arctic Ocean and its surrounding seas has been dominated by glacial-interglacials cycles. This has resulted in major environmental changes in relative sea levels, ice volumes, sea ice conditions, and ocean circulation as marine and terrestrially-based ice sheets waxed and waned. In this work, the acoustic signatures of several glaciated margins in the Northern Hemisphere are investigated and compared. This includes: NW Greenland, West Greenland, East Greenland, mid-Norway, Northern Norway, and the North Sea. These shelf successions preserve a geomorphological record of multiple glaciations and are imaged using seismic reflection data. To date, the majority of work in these areas has tended to focus on the most recent glaciations, which are well known. Here, the focus of the work is to look at the overall stratigraphic setting and how it influences (and is influenced by) the evolution of ice sheets throughout the glacial succession. Landform records are imaged using seismic data to provide a long-term insight into the styles of glaciation on each margin and what relation this may have had on climate, whilst the stratigraphic architectures across each site demonstrate how the inherited geology and tectonic setting can provide a fundamental control on the ice sheet and depositional styles. For example, Scoresby Sund is characterised by significant aggradation that is likely related to subsidence induced by lithospheric cooling rather than rapid glacial deposition, whilst the subsidence of the mid-Norwegian margin can be related to rapid glacial deposition and trapping of sediments behind inversion structures such as the Helland-Hansen Arch. The insights from this multi-margin study allow for regional, basin-wide, glaciological records to be developed

Micromorphological investigations of the Late Quaternary loess-paleosol sequences of the Kashmir Valley, India

NASA Astrophysics Data System (ADS)

Dar, Reyaz Ahmad; Chandra, Rakesh; Romshoo, Shakil Ahmad; Kowser, Nazia

2015-11-01

The loess-paleosol sequences of the Karewa Group preserve a valuable repository of the Late Quaternary climatic changes and the landscape evolution history of the Karewa Basin of Kashmir Valley in their lithological and pedogenic records. Three representative loess-paleosol sections at Shankerpora (SP), Khan Sahib (KS) and Pattan (PT) localities were chosen for detailed lithostratigraphic fieldwork and micromorphological observations of thin sections. Lithostratigraphic analysis revealed lateral and vertical variation in thickness and number of paleosol profiles from south-west to north-west of the Karewa Basin suggesting the availability of land-surface for periodic loess deposition. The SP section is marked by 6 (SP-S6, S7, S8, S9, S10, S12), KS section by 3 (KS-S2, S4, S5) and PT section by 2 (PT-S1, S3) thick mature paleosol profiles. Theses paleosols have well developed 'Ah' and 'Btk' horizons representing prolonged land-surface stability when pedogenic processes outpace loess deposition. On the other hand comparatively thin to thick paleosol profiles represent weak to moderate pedogenic maturity indicating short stratigraphic breaks with rapid loess deposition. Micromorphological observations of thin sections suggested that clay illuviation and CaCO3 accumulation have operated within the paleosol profiles. CaCO3 features are often associated with clay coatings suggesting decalcification of carbonates followed by clay illuviation. Pedogenic CaCO3 probably resulted from the precipitation of the soil solution near the average depth of wetting front. The pedogenic CaCO3, illuvial clay, mottles, iron manganese features, pedal microstructure and blocky aggregates reveal variation in the pedogenic maturity among and within the loess-paleosol sections. The morphological (both micro- and macro-morphological) attributes of loess-paleosols suggest variation of climatic conditions during the Late Quaternary period in the Karewa Basin of Kashmir Valley, India.

Late Quaternary river channel migrations of the Kura River in Transcaucasia - tectonic versus climatic causes

NASA Astrophysics Data System (ADS)

von Suchodoletz, Hans; Gärtner, Andreas; Hoth, Silvan; Umlauft, Josefine; Godoladze, Tea; Faust, Dominik

2015-04-01

Large-scale river channel migrations either in the form of avulsions or combing, i.e. progressive lateral migrations, are global phenomena during the Late Quaternary. Such channel migrations were triggered by tectonics, climate change, human activity or a combination of those factors. River channel migrations have the potential to cause significant human and economic losses. Thus, a more thorough knowledge about underlying causes and process rates is essential. Furthermore, such studies will elucidate the sensitivity or robustness of rivers to different external and internal forcing-agents, i.e. they help to identify the dominant drivers of regional landscape evolution. The Caucasus region is part of the active collision zone between the Africa-Arabian and the Eurasian plates, and is characterized by high current tectonic activity. Furthermore, significant environmental changes took place during the Late Quaternary, i.e. the shrinking or even disappearance of glaciers in the Greater and Lesser Caucasus or fundamental changes of the vegetation cover varying between woodland and grassland-dominated vegetation. The Kura River is the main gaining stream of the Transcaucasian Depression located between the Greater Caucasus Mountains in the north and the Lesser Caucasus Mountains in the south, and receives several tributaries from both mountain ranges. This study focusses on the middle course of the Kura River in eastern Georgia, SE of the city of Tbilisi. Integration of fluvial geomorphology, geochronology, heavy mineral analyses and seismo-tectonic analyses demonstrates that this part of the Kura River underwent large-scale channel migrations up to >10 km during Late Pleistocene and Holocene. It is interpreted that these movements followed both tectonic and climatic triggers: Whereas SW-ward migrations were caused by tectonic uplift in and SW-directed advance of the Kura fold and thrust belt as part of the Greater Caucasus, NE-ward migrations occurred during cold

Disappearance of the last lions and hyenas of Europe in the Late Quaternary - a chain reaction of large mammal prey migration, extinction and human antagonism

NASA Astrophysics Data System (ADS)

Diedrich, Cajus G.

2010-05-01

, Harz Mountain Karst) such as humans (archaeology cf. Günther 1988) but there are also lacking radiocarbon dating series or new excavations. Humans must have been in antagonism to the large predators about their prey and also their Late Palaeolithic sanctuaries - the large caves especially in southern Europe, in which they left thousands of animal figurations mainly during the Gravettian to Late Magdalenian periods (e.g. Breuil 1952, Begouen and Clottes 1987, Chauvet et al. 1995). Therefore the extinction reason of the largest predators of the Late Quaternary seems to be a complex combination of climate change with resulting maximum glacier extension which finally caused a southern directed megafaunal migration and reduction of the available caves and habitat areas in general. Finally in those southern European regions a higher competition about larger caves as cave bear hibernation places, hyena den sites and human settlement/sanctuary sites must have happened. Therefore an active hunt onto lions and hyenas can not be excluded nor be proven well yet, even if there are finds of necklesses in Europe from Late Palaeolithic ages made of mainly carnivore teeth including rare lion and hyena teeth, which might have been only collected. The resettlement of the northern European region by humans and a reduced "reindeer fauna" and its main and largest predators such as wolves and wolverines after the maximum glacier extension in the middle Late Weichselian started not before the Late Magdalenian (Magdalénian V: e.g. Perick Caves, Martins Cave - Sauerland Karst; Rübeland Caves - Harz Mountain Karst, Teufelsbrücke stone arch - Thuringian Karst). Humans occupied at that post-maximum glaciation time many caves in the Sauerland Karst region and even at open air sites in the Münsterland Bay or central Germany (cf. Bosinski 1987, Günther 1988). Within this Late Magdalénian V-VI times in the record of ten thousands of bones from more then 100 sites no hyena or lion remains are

Molluscan evidence for early middle Miocene marine glaciation in southern Alaska

USGS Publications Warehouse

Marincovich, L.

1990-01-01

Profound cooling of Miocene marine climates in southern Alaska culminated in early middle Miocene coastal marine glaciation in the northeastern Gulf of Alaska. This climatic change resulted from interaction of the Yakutat terrane with southern Alaska beginning in late Oligocene time. The ensuing extreme uplift of the coastal Chugach and St. Elias Mountains resulted in progressive regional cooling that culminated in coastal marine glaciation beginning in the early middle Miocene (15-16 Ma) and continuing to the present. The counterclockwise flow of surface water from the frigid northeastern Gulf of Alaska resulted in a cold-temperate shallow-marine environment in the western Gulf of Alaska, as it does today. Ironically, dating of Gulf of Alaska marine glaciation as early middle Miocene is strongly reinforced by the presence of a few tropical and subtropical mollusks in western Gulf of Alaska faunas. Shallow-marine waters throughout the Gulf of Alaska were cold-temperate to cold in the early middle Miocene, when the world ocean was undergoing peak Neogene warming. -Author

Late Quaternary faulting in the Vallo di Diano basin (southern Apennines, Italy)

NASA Astrophysics Data System (ADS)

Villani, F.; Pierdominici, S.; Cinti, F. R.

2009-12-01

The Vallo di Diano is the largest Quaternary extensional basin in the southern Apennines thrust-belt axis (Italy). This portion of the chain is highly seismic and is currently subject to NE-extension, which triggers large (M> 6) normal-faulting earthquakes along NW-trending faults. The eastern edge of the Vallo di Diano basin is bounded by an extensional fault system featuring three main NW-trending, SW-dipping, right-stepping, ~15-17 km long segments (from north to south: Polla, Atena Lucana-Sala Consilina and Padula faults). Holocene activity has been documented so far only for the Polla segment. We have therefore focused our geomorphological and paleoseismological study on the southern portion of the system, particularly along the ~ 4 km long Atena Lucana-Sala Consilina and Padula faults overlap zone. The latter is characterized by a complex system of coalescent alluvial fans, Middle Pleistocene to Holocene in age. Here we recognized a > 4 km long and 0.5-1.4 km wide set of scarps (ranging in height between 1 m and 2.5 m) affecting Late Pleistocene - Holocene alluvial fans. In the same area, two Late Pleistocene volcanoclastic layers at the top of an alluvial fan exposed in a quarry are affected by ~ 1 m normal displacements. Moreover, a trench excavated across a 2 m high scarp affecting a Holocene fan revealed warping of Late Holocene debris flow deposits, with a total vertical throw of about 0.3 m. We therefore infer the overlap zone of the Atena Lucana-Sala Consilina and Padula faults is a breached relay ramp, generated by hard-linkage of the two fault segments since Late Pleistocene. This ~ 32 km long fault system is active and is capable of generating Mw ≥6.5 earthquakes.

Quantitative estimates of Asian dust input to the western Philippine Sea in the mid-late Quaternary and its potential significance for paleoenvironment

NASA Astrophysics Data System (ADS)

Xu, Zhaokai; Li, Tiegang; Clift, Peter D.; Lim, Dhongil; Wan, Shiming; Chen, Hongjin; Tang, Zheng; Jiang, Fuqing; Xiong, Zhifang

2015-09-01

We present a new high-resolution multiproxy data set of Sr-Nd isotopes, rare earth element, soluble iron, and total organic carbon data from International Marine Global Change Study Core MD06-3047 located in the western Philippine Sea. We integrate our new data with published clay mineralogy, rare earth element chemistry, thermocline depth, and δ13C differences between benthic and planktonic foraminifera, in order to quantitatively constrain Asian dust input to the basin. We explore the relationship between Philippine Sea and high-latitude Pacific eolian fluxes, as well as its significance for marine productivity and atmospheric CO2 during the mid-late Quaternary. Three different indices indicate that Asian dust contributes between ˜15% and ˜50% to the detrital fraction of the sediments. Eolian dust flux in Core MD06-3047 is similar to that in the polar southern Pacific sediment. Coherent changes for most dust flux maximum/minimum indicate that dust generation in interhemispheric source areas might have a common response to climatic variation over the mid-late Quaternary. Furthermore, we note relatively good coherence between Asian dust input, soluble iron concentration, local marine productivity, and even global atmospheric CO2 concentration over the entire study interval. This suggests that dust-borne iron fertilization of marine phytoplankton might have been a periodic process operating at glacial/interglacial time scales over the past 700 ka. We suggest that strengthening of the biological pump in the Philippine Sea, and elsewhere in the tropical western Pacific during the mid-late Quaternary glacial periods may contribute to the lowering of atmospheric CO2 concentrations during ice ages.

Low atmospheric CO(2) levels during the Permo- Carboniferous glaciation inferred from fossil lycopsids.

PubMed

Beerling, D J

2002-10-01

Earth history was punctuated during the Permo-Carboniferous [300-250 million years (Myr) ago] by the longest and most severe glaciation of the entire Phanerozoic Eon. But significant uncertainty surrounds the concentration of CO(2) in the atmosphere through this time interval and therefore its role in the evolution of this major prePleistocene glaciation. Here, I derive 24 Late Paleozoic CO(2) estimates from the fossil cuticle record of arborsecent lycopsids of the equatorial Carboniferous and Permian swamp communities. Quantitative calibration of Late Carboniferous (330-300 Myr ago) and Permian (270-260 Myr ago) lycopsid stomatal indices yield average atmospheric CO(2) concentrations of 344 ppm and 313 ppm, respectively. The reconstructions show a high degree of self-consistency and a degree of precision an order of magnitude greater than other approaches. Low CO(2) levels during the Permo-Carboniferous glaciation are in agreement with glaciological evidence for the presence of continental ice and coupled models of climate and ice-sheet growth on Pangea. Moreover, the Permian data indicate atmospheric CO(2) levels were low 260 Myr ago, by which time continental deglaciation was already underway. Positive biotic feedbacks on climate, and geotectonic events, therefore are implicated as mechanisms underlying deglaciation.

Low atmospheric CO2 levels during the Permo- Carboniferous glaciation inferred from fossil lycopsids

PubMed Central

Beerling, D. J.

2002-01-01

Earth history was punctuated during the Permo-Carboniferous [300–250 million years (Myr) ago] by the longest and most severe glaciation of the entire Phanerozoic Eon. But significant uncertainty surrounds the concentration of CO2 in the atmosphere through this time interval and therefore its role in the evolution of this major prePleistocene glaciation. Here, I derive 24 Late Paleozoic CO2 estimates from the fossil cuticle record of arborsecent lycopsids of the equatorial Carboniferous and Permian swamp communities. Quantitative calibration of Late Carboniferous (330–300 Myr ago) and Permian (270–260 Myr ago) lycopsid stomatal indices yield average atmospheric CO2 concentrations of 344 ppm and 313 ppm, respectively. The reconstructions show a high degree of self-consistency and a degree of precision an order of magnitude greater than other approaches. Low CO2 levels during the Permo-Carboniferous glaciation are in agreement with glaciological evidence for the presence of continental ice and coupled models of climate and ice-sheet growth on Pangea. Moreover, the Permian data indicate atmospheric CO2 levels were low 260 Myr ago, by which time continental deglaciation was already underway. Positive biotic feedbacks on climate, and geotectonic events, therefore are implicated as mechanisms underlying deglaciation. PMID:12235372

Late Quaternary Faulting along the San Juan de los Planes Fault Zone, Baja California Sur, Mexico

NASA Astrophysics Data System (ADS)

Busch, M. M.; Coyan, J. A.; Arrowsmith, J.; Maloney, S. J.; Gutierrez, G.; Umhoefer, P. J.

2007-12-01

As a result of continued distributed deformation in the Gulf Extensional Province along an oblique-divergent plate margin, active normal faulting is well manifest in southeastern Baja California. By characterizing normal-fault related deformation along the San Juan de los Planes fault zone (SJPFZ) southwest of La Paz, Baja California Sur we contribute to understanding the patterns and rates of faulting along the southwest gulf-margin fault system. The geometry, history, and rate of faulting provide constraints on the relative significance of gulf-margin deformation as compared to axial system deformation. The SJPFZ is a major north-trending structure in the southern Baja margin along which we focused our field efforts. These investigations included: a detailed strip map of the active fault zone, including delineation of active scarp traces and geomorphic surfaces on the hanging wall and footwall; fault scarp profiles; analysis of bedrock structures to better understand how the pattern and rate of strain varied during the development of this fault zone; and a gravity survey across the San Juan de los Planes basin to determine basin geometry and fault behavior. The map covers a N-S swath from the Gulf of California in the north to San Antonio in the south, an area ~45km long and ~1-4km wide. Bedrock along the SJPFZ varies from Cretaceous Las Cruces Granite in the north to Cretaceous Buena Mujer Tonalite in the south and is scarred by shear zones and brittle faults. The active scarp-forming fault juxtaposes bedrock in the footwall against Late Quaternary sandstone-conglomerate. This ~20m wide zone is highly fractured bedrock infused with carbonate. The northern ~12km of the SJPFZ, trending 200°, preserves discontinuous scarps 1-2km long and 1-3m high in Quaternary units. The scarps are separated by stretches of bedrock embayed by hundreds of meters-wide tongues of Quaternary sandstone-conglomerate, implying low Quaternary slip rate. Further south, ~2 km north of the

Species-specific responses of Late Quaternary megafauna to climate and humans

PubMed Central

Lorenzen, Eline D.; Nogués-Bravo, David; Orlando, Ludovic; Weinstock, Jaco; Binladen, Jonas; Marske, Katharine A.; Ugan, Andrew; Borregaard, Michael K.; Gilbert, M. Thomas P.; Nielsen, Rasmus; Ho, Simon Y. W.; Goebel, Ted; Graf, Kelly E.; Byers, David; Stenderup, Jesper T.; Rasmussen, Morten; Campos, Paula F.; Leonard, Jennifer A.; Koepfli, Klaus-Peter; Froese, Duane; Zazula, Grant; Stafford, Thomas W.; Aaris-Sørensen, Kim; Batra, Persaram; Haywood, Alan M.; Singarayer, Joy S.; Valdes, Paul J.; Boeskorov, Gennady; Burns, James A.; Davydov, Sergey P.; Haile, James; Jenkins, Dennis L.; Kosintsev, Pavel; Kuznetsova, Tatyana; Lai, Xulong; Martin, Larry D.; McDonald, H. Gregory; Mol, Dick; Meldgaard, Morten; Munch, Kasper; Stephan, Elisabeth; Sablin, Mikhail; Sommer, Robert S.; Sipko, Taras; Scott, Eric; Suchard, Marc A.; Tikhonov, Alexei; Willerslev, Rane; Wayne, Robert K.; Cooper, Alan; Hofreiter, Michael; Sher, Andrei; Shapiro, Beth; Rahbek, Carsten; Willerslev, Eske

2014-01-01

Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary remain contentious. We use ancient DNA, species distribution models and the human fossil record to elucidate how climate and humans shaped the demographic history of woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison and musk ox. We show that climate has been a major driver of population change over the past 50,000 years. However, each species responds differently to the effects of climatic shifts, habitat redistribution and human encroachment. Although climate change alone can explain the extinction of some species, such as Eurasian musk ox and woolly rhinoceros, a combination of climatic and anthropogenic effects appears to be responsible for the extinction of others, including Eurasian steppe bison and wild horse. We find no genetic signature or any distinctive range dynamics distinguishing extinct from surviving species, underscoring the challenges associated with predicting future responses of extant mammals to climate and human-mediated habitat change. PMID:22048313

Late Quaternary deglacial history of the Mérida Andes, Venezuela

NASA Astrophysics Data System (ADS)

Stansell, Nathan D.; Abbott, Mark B.; Polissar, Pratigya J.; Wolfe, Alexander P.; Bezada, Maximiliano; Rull, Valentí

2005-10-01

Radiocarbon-dated sediment cores from seven lakes and two bogs spanning the Cordillera de Mérida in the Venezuelan Andes were used to identify and date the regional history of late Pleistocene and Holocene glacial activity. Coring sites were selected at different elevations across a pronounced rain shadow from southeast (wet) to northwest (dry). Sediment lithostratigraphy and magnetic susceptibility, in conjunction with AMS radiocarbon dates on macrofossils and charcoal, were used to constrain deglaciation. The local expression of the Last Glacial Maximum occurred between 22 750 and 19 960 cal. yr BP. On the wetter southeastern side of the Cordillera de Mérida, glaciers had significantly retreated by 15 700 cal. yr BP, followed by several minor glacial advances and retreats between 14 850 and 13 830 cal. yr BP. At least one major glacial readvance occurred between 13 830 and 10 000 cal. yrBP in the wetter southeastern sector of the region. The drier northwest side of the Cordillera de Mérida records initial glacial retreat by 14240cal.yrBP. Multiple sites on both sides of the Mérida Andes record a further phase of extensive deglaciation approximately 10000cal.yrBP. However, the north-northwest facing Mucubají catchment remained partially glaciated until ca. 6000cal.yrBP. Deglacial ages from the Venezuelan Andes are consistently younger than those reported from the Southern Hemisphere Andes, suggesting an inter-hemispheric deglacial lag in the northern tropics of the order of two thousand years.

Neotectonics of interior Alaska and the late Quaternary slip rate along the Denali fault system

USGS Publications Warehouse

Haeussler, Peter J.; Matmon, Ari; Schwartz, David P.; Seitz, Gordon G.

2017-01-01

The neotectonics of southern Alaska (USA) are characterized by a several hundred kilometers–wide zone of dextral transpressional that spans the Alaska Range. The Denali fault system is the largest active strike-slip fault system in interior Alaska, and it produced a Mw 7.9 earthquake in 2002. To evaluate the late Quaternary slip rate on the Denali fault system, we collected samples for cosmogenic surface exposure dating from surfaces offset by the fault system. This study includes data from 107 samples at 19 sites, including 7 sites we previously reported, as well as an estimated slip rate at another site. We utilize the interpreted surface ages to provide estimated slip rates. These new slip rate data confirm that the highest late Quaternary slip rate is ∼13 mm/yr on the central Denali fault near its intersection with the eastern Denali and the Totschunda faults, with decreasing slip rate both to the east and west. The slip rate decreases westward along the central and western parts of the Denali fault system to 5 mm/yr over a length of ∼575 km. An additional site on the eastern Denali fault near Kluane Lake, Yukon, implies a slip rate of ∼2 mm/yr, based on geological considerations. The Totschunda fault has a maximum slip rate of ∼9 mm/yr. The Denali fault system is transpressional and there are active thrust faults on both the north and south sides of it. We explore four geometric models for southern Alaska tectonics to explain the slip rates along the Denali fault system and the active fault geometries: rotation, indentation, extrusion, and a combination of the three. We conclude that all three end-member models have strengths and shortcomings, and a combination of rotation, indentation, and extrusion best explains the slip rate observations.

Evaluation of ERTS-1 imagery for mapping Quaternary deposits and landforms in the Great Plains and Midwest

NASA Technical Reports Server (NTRS)

Morrison, R. B. (Principal Investigator); Hallberg, G. R.

1973-01-01

The author has identified the following significant results. The main landform associations and larger landforms are readily identifiable on the better images and commonly the gross associations of surficial Quaternary deposits also can be differentiated, primarily by information on landforms and soils. Maps showing the Quaternary geologic-terrain units that can be differentiated from the ERTS-1 images are being prepared for 20-odd potential study areas in Illinois, Iowa, Missouri, Kansas, Nebraska, and South Dakota. Among the more distinct features are the major moraines and outwash channels of the last (Wisconsin) glaciation. Analysis of dissection/drainage patterns from the synoptic imagery is proving useful for detecting anomalies that may be caused by stream diversions and moraines of pre-Wisconsin glaciations, by variable loess deposition, by tectonism, and other factors. Numerous abandoned river valleys have been mapped. Trend-lines of several known pre-Wisconsin moraine systems have been identified in Iowa, Nebraska, and Kansas, and also several similar trend-lines, that may indicate previously unknown moraine systems of middle and possibly early Pleistocene age, have been found in Iowa and Missouri. The area inundated by a major flood in southwestern Iowa also has been delineated from ERTS-1 imagery.

Climate change not to blame for late Quaternary megafauna extinctions in Australia

PubMed Central

Saltré, Frédérik; Rodríguez-Rey, Marta; Brook, Barry W.; Johnson, Christopher N; Turney, Chris S. M.; Alroy, John; Cooper, Alan; Beeton, Nicholas; Bird, Michael I.; Fordham, Damien A.; Gillespie, Richard; Herrando-Pérez, Salvador; Jacobs, Zenobia; Miller, Gifford H.; Nogués-Bravo, David; Prideaux, Gavin J.; Roberts, Richard G.; Bradshaw, Corey J. A.

2016-01-01

Late Quaternary megafauna extinctions impoverished mammalian diversity worldwide. The causes of these extinctions in Australia are most controversial but essential to resolve, because this continent-wide event presaged similar losses that occurred thousands of years later on other continents. Here we apply a rigorous metadata analysis and new ensemble-hindcasting approach to 659 Australian megafauna fossil ages. When coupled with analysis of several high-resolution climate records, we show that megafaunal extinctions were broadly synchronous among genera and independent of climate aridity and variability in Australia over the last 120,000 years. Our results reject climate change as the primary driver of megafauna extinctions in the world's most controversial context, and instead estimate that the megafauna disappeared Australia-wide ∼13,500 years after human arrival, with shorter periods of coexistence in some regions. This is the first comprehensive approach to incorporate uncertainty in fossil ages, extinction timing and climatology, to quantify mechanisms of prehistorical extinctions. PMID:26821754

Mapped plant macrofossil and pollen records of late Quaternary vegetation change in eastern North America

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, S.T.; Overpeck, J.T.; Webb, T. III

We compiled a plant macrofossil database for 12 eastern North American tree and shrub taxa (Picea sp., P. glauca, P. mariana, Larix laricina, Abies balsamea, Tsuga canadensis, Pinus strobus, P. banksiana, P. resinosa, Betula papyrifera, B. alleghaniensis, B. Series Humiles) at 264 late Quaternary sites. Presence/absence maps for these taxa at 18,000, 15,000, 12,000, 9000, 6000, 3000, and 0 {sup 14}C yr B.P. show changes in geographic ranges of these species in response to climatic change. Comparison of the macrofossil maps with isopoll maps for corresponding taxa corroborates inferences from the pollen data, and reveals species-level patterns not apparent inmore » the pollen maps.« less

Large-scale evolution of the central-east Greenland margin: New insights to the North Atlantic glaciation history

NASA Astrophysics Data System (ADS)

Pérez, Lara F.; Nielsen, Tove; Knutz, Paul C.; Kuijpers, Antoon; Damm, Volkmar

2018-04-01

The continental shelf of central-east Greenland is shaped by several glacially carved transverse troughs that form the oceanward extension of the major fjord systems. The evolution of these troughs through time, and their relation with the large-scale glaciation of the Northern Hemisphere, is poorly understood. In this study seismostratigraphic analyses have been carried out to determine the morphological and structural development of this important sector of the East Greenland glaciated margin. The age of major stratigraphic discontinuities has been constrained by a direct tie to ODP site 987 drilled in the Greenland Sea basin plain off Scoresby Sund fan system. The areal distribution and internal facies of the identified seismic units reveal the large-scale depositional pattern formed by ice-streams draining a major part of the central-east Greenland ice sheet. Initial sedimentation along the margin was, however, mainly controlled by tectonic processes related to the margin construction, continental uplift, and fluvial processes. From late Miocene to present, progradational and erosional patterns point to repeated glacial advances across the shelf. The evolution of depo-centres suggests that ice sheet advances over the continental shelf have occurred since late Miocene, about 2 Myr earlier than previously assumed. This cross-shelf glaciation is more pronounced during late Miocene and early Pliocene along Blosseville Kyst and around the Pliocene/Pleistocene boundary off Scoresby Sund; indicating a northward migration of the glacial advance. The two main periods of glaciation were separated by a major retreat of the ice sheet to an inland position during middle Pliocene. Mounded-wavy deposits interpreted as current-related deposits suggest the presence of changing along-slope current dynamics in concert with the development of the modern North Atlantic oceanographic pattern.

Compound-specific isotope records of late-quaternary environmental change in southeastern North Carolina

NASA Astrophysics Data System (ADS)

Lane, Chad S.; Taylor, Audrey K.; Spencer, Jessica; Jones, Kaylee B.

2018-02-01

Reconstructions of late Quaternary paleohydrology are rare from the U.S. Atlantic coastal plain (ACP). Here we present compound-specific hydrogen (δ2Halkane) and carbon (δ13Calkane) isotope analyses of terrestrially-derived n-alkanes from Jones Lake and Singletary Lake in eastern North Carolina spanning the last ∼50,000 years. Combined with pollen, charcoal, and bulk geochemical analyses, the δ2Halkane data indicate arid conditions during the late-Pleistocene, but differing edaphic conditions at the sites perhaps related to differing water table depths. The δ13Calkane data indicate a significant C4 plant component during the late Pleistocene, but other proxies indicate a sparsely-vegetated landscape. The Pleistocene-Holocene transition is marked by rapid fluctuations in δ2Halkane values that are similar to the patterns of Bølling Allerød and Younger Dryas isotope data from Greenland indicating sensitivity of the regional climate to short-lived, high-amplitude climatic events. The δ2Halkane data indicate a mesic early Holocene that supported colonization by Quercus-dominated ecosystems. Evidence of middle Holocene aridity in eastern Tennessee and western North Carolina contrasts with evidence of mesic conditions on the ACP, a geographic pattern similar to modern teleconnected precipitation responses to the Pacific Decadal Oscillation. A transition to Pinus-dominated ecosystems ∼5500 cal yr B.P. is accompanied by a large increase charcoal, but is not coincident with any large changes in δ2Halkane values, indicating that hydrologic change was likely not responsible for sustained late-Holocene dominance of Pinus. The lack of a change in middle Holocene hydrology and the spatiotemporally heterogeneous nature of the Quercus-Pinus transition on the ACP indicate prehistoric anthropogenic land management practices may represent the most parsimonious explanation for the regionally pervasive ecological change.

Late Quaternary landscape evolution in the Great Karoo, South Africa: Processes and drivers.

NASA Astrophysics Data System (ADS)

Oldknow, Chris; Hooke, Janet; Lang, Andreas

2016-04-01

The Great Karoo spans the north-central part of South Africa at a major climatic boundary. The characteristics, sequences, spatial patterns and drivers of river response to Late Quaternary climate changes in this region remain unclear due to the fragmentary alluvial/colluvial stratigraphic record and the lack of dated palaeoclimatic archives. Dendritic gully networks incised into deep deposits (up to 6 m) of colluvium and alluvium in the upper Sundays River catchment expose a legacy of "cut and fill" features. In 1st order tributaries, these are predominantly discontinuous palaeochannels and flood-outs with localised palaeosols, whereas in 2nd & 3rd order tributaries there are: 1) incised palaeo-geomorphic surfaces, 2) semi-continuous inset terrace sequences, 3) buried palaeo-gully topography. Using a combination of field mapping, logging of sediment outcrops, soil micromorphological and grain size analysis, mineral magnetic measurements and radiometric dating (OSL & 14C), we derive a stratigraphic evolution model which demonstrates a) the number of phases of incision, aggradation and pedogenesis, b) the spatial and temporal extent of each phase and c) the drivers of alluviation and associated feedbacks. Our reconstruction of regional valley alluviation indicates four distinct terrace units of contrasting depositional age. The base of the succession reflects slow aggradation under periglacial conditions associated with the Last Glacial Maximum. Subsequent channel entrenchment, causing terrace abandonment (T1) occurred in the deglacial period when vegetation and rainfall were in anti-phase. Re-instatement of connectivity with deep upland colluvial stores resulted in the injection of a pulse of sediment to valley floors, triggering compartmentalised backfilling (aggradation of T2) which propagated upstream as far as the second order drainage lines. This backfilling restructured the local hydrology, which, in concert with enhanced summer-rainfall, contributed to a

Micropaleontologic record of late Pliocene and Quaternary paleoenvironments in the northern Albemarle Embayment, North Carolina, U.S.A.

USGS Publications Warehouse

Culver, S.J.; Farrell, K.M.; Mallinson, D.J.; Horton, B.P.; Willard, D.A.; Thieler, E.R.; Riggs, S.R.; Snyder, S.W.; Wehmiller, J.F.; Bernhardt, C.E.; Hillier, C.

2008-01-01

Micropaleontological data provide a strong actualistic basis for detailed interpretations of Quaternary paleoenvironmental change. The 90??m-thick Quaternary record of the Albemarle Embayment in the mid-Atlantic coastal plain of the USA provides an excellent opportunity to use such an approach in a region where the details of Quaternary environmental change are poorly known. The foraminiferal record in nine cores from the northern Outer Banks, east of Albemarle Sound, North Carolina, indicates the deposition of subhorizontal, mostly open-marine early to late Pleistocene units unconformably upon a basement of late Pliocene reduced-oxygen, fine-grained, shelf-basin deposits. Pollen data record several warm-cool fluctuations within the early to mid-Pleistocene deposits. Diatom data indicate that some fresh and brackish-water units occur within the generally open-marine Pleistocene succession. A channel cut by the paleo-Roanoke River during the last glacial sea-level lowstand occurs in the northern part of the study area. Pollen indicates that the basal fluvial valley fill accumulated in cooler than modern climate conditions in the latest Pleistocene. Overlying silts and muds accumulated under cool climatic, estuarine conditions according to diatom and pollen data. Radiocarbon ages from the estuarine deposits indicate that the bulk of these sediments accumulated during the latest Pleistocene. The estuarine channel-fill deposits are overlain by Holocene open-marine sands deposited as the rising sea transgressed into the estuary approximately 8.5 to 9.0??kyr BP. Within the barrier island drill cores of this study, fully marine sedimentation occurred throughout the Holocene. However, immediately west of the present barrier island, mid- to late Holocene estuarine deposits underlie the modern Albemarle Sound. The islands that currently form a continuous barrier across the mouth of Albemarle Sound have a complex history of Holocene construction and destruction and large

Thermokarst transformation of permafrost preserved glaciated landscapes.

NASA Astrophysics Data System (ADS)

Kokelj, S.; Tunnicliffe, J. F.; Fraser, R.; Kokoszka, J.; Lacelle, D.; Lantz, T. C.; Lamoureux, S. F.; Rudy, A.; Shakil, S.; Tank, S. E.; van der Sluijs, J.; Wolfe, S.; Zolkos, S.

2017-12-01

Thermokarst is the fundamental mechanism of landscape change and a primary driver of downstream effects in a warming circumpolar world. Permafrost degradation is inherently non-linear because latent heat effects can inhibit thawing. However, once this thermal transition is crossed thermokarst can accelerate due to the interaction of thermal, physical and ecological feedbacks. In this paper we highlight recent climate and precipitation-driven intensification of thaw slumping that is transforming permafrost preserved glaciated landscapes in northwestern Canada. The continental distribution of slump affected terrain reflects glacial extents and recessional positions of the Laurentide Ice sheet. On this basis and in conjunction with intense thermokarst in cold polar environments, we highlight the critical roles of geological legacy and climate history in dictating the sensitivity of permafrost terrain. These glaciated landscapes, maintained in a quasi-stable state throughout much of the late Holocene are now being transformed into remarkably dynamic environments by climate-driven thermokarst. Individual disturbances displace millions of cubic metres of previously frozen material downslope, converting upland sedimentary stores into major source areas. Precipitation-driven evacuation of sediment by fluidized mass flows perpetuates non-linear enlargement of disturbances. The infilling of valleys with debris deposits tens of metres thick increases stream base-levels and promotes rapid valley-side erosion. These processes destabilize adjacent slopes and proliferate disturbance effects. Physically-based modeling of thaw slump development provides insight into the trajectories of landscape change, and the mapping of fluvial linkages portrays the cascade of effects across watershed scales. Post-glacial or "paraglacial" models of landscape evolution provide a useful framework for understanding the nature and magnitude of climate-driven changes in permafrost preserved glaciated

Regional deformation of late Quaternary fluvial sediments in the Apennines foreland basin (Emilia, Italy)

NASA Astrophysics Data System (ADS)

Stefani, Marco; Minarelli, Luca; Fontana, Alessandro; Hajdas, Irka

2018-04-01

Our research is aimed at estimating the vertical deformation affecting late Quaternary units accumulated into the foreland basin of the Northern Apennines chain. Beneath the study alluvial plain, compressive fault-fold structures are seismically active. We reconstructed the stratigraphic architecture and the depositional evolution of the alluvial deposits, which accumulated in the first 40 m of subsurface, through the last 45,000 years, from before the Last Glacial Maximum to the present. A 58 km-long stratigraphic profile was correlated from the foothill belt near Bologna to the vicinity of the Po River. The analysis of the profile documents subsidence movements through the last 12,000 years, exceeding - 18 m in syncline areas, with subsidence rates of at least 1.5 m/ka. Anticlines areas experienced a much lower subsidence than the syncline ones.

Eskers and other evidence of wet-based glaciation in Phlegra Montes, Mars.

NASA Astrophysics Data System (ADS)

Gallagher, Colman; Balme, Matt

2016-04-01

Although glacial landsystems produced under warm/wet based conditions are very common on Earth, glaciological and landform evidence indicates that glaciation on Mars during the Amazonian period (3 Ga to present) has been characterised by cold/dry based glaciers, consistent with the prevailing cold, hyperarid conditions. However, this presentation describes a system of sinuous ridges, interpreted as eskers (1), emerging from the degraded piedmont terminus of a Late Amazonian (˜150 Ma) glacier in the southern Phlegra Montes region of Mars. This is probably the first identification of martian eskers that can be directly linked to their parent glacier. Together with their contextual landform assemblage, the eskers are indicative of glacial melting and subglacial meltwater routing but the confinement of the system to a well-defined, regionally significant graben, and the absence of eskers elsewhere in the region, suggests that melting was a response to locally enhanced geothermal heat flux, rather than regional, climate-induced warming. Now, however, new observations reveal the presence of many assemblages of glacial abrasion forms and associated channels that could be evidence of more widespread wet-based glaciation in Phlegra Montes, including the collapse of several distinct ice domes. This landform assemblage has not been described in other glaciated, mid-latitude regions of the martian northern hemisphere. Moreover, Phlegra Montes are flanked by lowlands displaying evidence of extensive volcanism, including contact between plains lava and piedmont glacial ice. These observations suggest that the glaciation of Phlegra Montes might have been strongly conditioned by both volcanism and more restricted forms of ground-heating. These are important new insights both to the forcing of glacial dynamic and melting behaviour on Mars by factors other than climate and to the production of liquid water on Mars during the Late Amazonian. (1) Gallagher, C. and Balme, M. (2015

Influence of late Quaternary climate change on present patterns of genetic variation in valley oak, Quercus lobata Née.

PubMed

Gugger, Paul F; Ikegami, Makihiko; Sork, Victoria L

2013-07-01

Phylogeography and ecological niche models (ENMs) suggest that late Quaternary glacial cycles have played a prominent role in shaping present population genetic structure and diversity, but have not applied quantitative methods to dissect the relative contribution of past and present climate vs. other forces. We integrate multilocus phylogeography, climate-based ENMs and multivariate statistical approaches to infer the effects of late Quaternary climate change on contemporary genetic variation of valley oak (Quercus lobata Née). ENMs indicated that valley oak maintained a stable distribution with local migration from the last interglacial period (~120 ka) to the Last Glacial Maximum (~21 ka, LGM) to the present compared with large-scale range shifts for an eastern North American white oak (Quercus alba L.). Coast Range and Sierra Nevada foothill populations diverged in the late Pleistocene before the LGM [104 ka (28-1622)] and have occupied somewhat distinct climate niches, according to ENMs and coalescent analyses of divergence time. In accordance with neutral expectations for stable populations, nuclear microsatellite diversity positively correlated with niche stability from the LGM to present. Most strikingly, nuclear and chloroplast microsatellite variation significantly correlated with LGM climate, even after controlling for associations with geographic location and present climate using partial redundancy analyses. Variance partitioning showed that LGM climate uniquely explains a similar proportion of genetic variance as present climate (16% vs. 11-18%), and together, past and present climate explains more than geography (19%). Climate can influence local expansion-contraction dynamics, flowering phenology and thus gene flow, and/or impose selective pressures. These results highlight the lingering effect of past climate on genetic variation in species with stable distributions. © 2013 John Wiley & Sons Ltd.

Late Pliocene age control and composite depths at ODP Site 982, revisited

NASA Astrophysics Data System (ADS)

Khélifi, N.; Sarnthein, M.; Naafs, B. D. A.

2011-05-01

Ocean Drilling Program (ODP) Site 982 provided a key sediment section at Rockall Plateau for reconstructing northeast Atlantic paleoceanography and monitoring benthic δ18O stratigraphy over the Late Pliocene to Quaternary onset of major Northern Hemisphere Glaciation. A renewed hole-specific inspection of magnetostratigraphic events and the addition of epibenthic δ18O records for short Pliocene sections in holes 982A, B, and C, crossing core breaks in the δ18O record published for Hole 982B, now imply a major revision of composite core depths. After tuning to the orbitally tuned reference record LR04 the new composite δ18O record results in a hiatus, where the Kaena magnetic event might been lost, and in a significant age reduction for all proxy records by 130 to 20 ka over the time span 3.2-2.7 million yr ago (Ma). Our study demonstrates the significance of reliable composite-depth scales and δ18O stratigraphies in ODP sediment records for ocean-wide correlations in paleoceanography and makes Late Pliocene trends found at Site 982 much better comparable to those published from elsewhere in the North Atlantic.

Geochronology of Tropical Alpine Glaciations From the Cordillera Huayhuash, Peru

NASA Astrophysics Data System (ADS)

Hall, S. R.; Farber, D. L.; Rodbell, D. T.; Finkel, R. C.; Ramage, J. M.; Smith, J. A.; Mark, B. G.; Seltzer, G. O.

2004-12-01

The Cordillera Huayhuash of the Central Peruvian Andes (10.3° S, 76.9° W) is an ideal range to study regional climate signals and variations in paleo-ice volumes. Located between the Cordillera Blanca to the north and the Junin region to the south, the range trends nearly north-south with modern glaciers confined to the high peaks (>4800 m). Cross-cutting relationships, geomorphology, and correlation with surface exposure dated moraines in the nearby Cordillera Blanca suggest the region preserves a rich record of tropical glaciation. In order to determine the glacial chronology we mapped and dated glacial features of the Jahuacocha valley (which drains the western side of the range) and two eastern drainages, the Mitococha valley, and the Carhuacocha valley. At each locality we used ASTER data, aerial photographs, and GPS to map glacial features both within main valleys and tributaries. We sampled quartz-bearing erratics on moraine crests as well as ice-polished bedrock surfaces for exposure age dating using in situ produced cosmogenic 10Be and 26Al. In the Jahuacocha valley, the greatest ice extent reached an elevation of ˜4090m and moraine crest boulders yield and age of ˜11.2 ±0.6 ka suggesting a significant late Glacial ice advance or stillstand. A younger cluster of moraines exists ˜1 km up-valley at an elevation of ˜4100m. These moraines, dated at ˜8.0 ±1.0 ka, suggest an early Holocene advance. In the Mitococha valley, a young moraine and polished bedrock dated at ˜0.2 ka and ˜11.4 ±0.4 ka respectively span the late Glacial through recent. The late Glacial features of this eastern drainage occur at an elevation of ˜4100m while the recent events occur at an elevation of ˜4380m. Our preliminary results suggest that all three valleys experienced a very similar glacial history with minor differences likely due to the variations in valley morphology. Comparing the chronology of glaciation in the Cordillaera Huayhuash with that in regions to the

Climate warming and humans played different roles in triggering Late Quaternary extinctions in east and west Eurasia

PubMed Central

Wan, Xinru

2017-01-01

Climate change and humans are proposed as the two key drivers of total extinction of many large mammals in the Late Pleistocene and Early Holocene, but disentangling their relative roles remains challenging owing to a lack of quantitative evaluation of human impact and climate-driven distribution changes on the extinctions of these large mammals in a continuous temporal–spatial dimension. Here, our analyses showed that temperature change had significant effects on mammoth (genus Mammuthus), rhinoceros (Rhinocerotidae), horse (Equidae) and deer (Cervidae). Rapid global warming was the predominant factor driving the total extinction of mammoths and rhinos in frigid zones from the Late Pleistocene and Early Holocene. Humans showed significant, negative effects on extirpations of the four mammalian taxa, and were the predominant factor causing the extinction or major extirpations of rhinos and horses. Deer survived both rapid climate warming and extensive human impacts. Our study indicates that both the current rates of warming and range shifts of species are much faster than those from the Late Pleistocene to Holocene. Our results provide new insight into the extinction of Late Quaternary megafauna by demonstrating taxon-, period- and region-specific differences in extinction drivers of climate change and human disturbances, and some implications about the extinction risk of animals by recent and ongoing climate warming. PMID:28330916

Ancient glaciations and hydrocarbon accumulations in North Africa and the Middle East

NASA Astrophysics Data System (ADS)

Le Heron, Daniel Paul; Craig, Jonathan; Etienne, James L.

2009-04-01

At least six glaciations are purported to have affected North Africa and the Middle East region over the last one billion years, including two in the Cryogenian (Neoproterozoic), Hirnantian (Late Ordovician), Silurian, Carboniferous and Early Permian events. The sedimentary record associated with these glaciations, together with the intensity to which each has been investigated, is highly variable. As hydrocarbon exploration proceeds aggressively across the North Africa and Middle East regions, we review the relationship between glaciation and hydrocarbon accumulations. With the exception of Oman, and locally Egypt, which were tectonically active both during the Neoproterozoic and Early Palaeozoic all glaciations took place along an essentially stable passive continental margin. During the Neoproterozoic, two glaciations are recognised, referred to as older and younger Cryogenian glaciations respectively. Both of these Cryogenian events are preserved in Oman; only the younger Cryogenian has been reported in North Africa in Mauritania and Mali at the flanks of the Taoudenni Basin. The process of initial deglaciation in younger Cryogenian glaciations resulted in incision, at least locally producing large-bedrock palaeovalleys in Oman, and the deposition of glacial diamictites, gravels, sandstones and mudstones. As deglaciation progressed "cap carbonates" were deposited, passing vertically into shale with evidence for deposition in an anoxic environment. Hence, younger Cryogenian deglaciation may be associated with hydrocarbon source rock deposits. Hirnantian (Late Ordovician) glaciation was short lived (< 0.5 Myr) and affected intracratonic basins of Mauritania, Morocco, Algeria, Libya, Egypt and Saudi Arabia. The organisation of the glacial sedimentary record is considered to be controlled at the basin-scale by the location of fast-flowing ice streams active during glacial maxima, and by the processes of meltwater release during glacial recession. In these latter

Late Quaternary stratigraphy and geochronology of the western Killpecker Dunes, Wyoming, USA

USGS Publications Warehouse

Mayer, J.H.; Mahan, S.A.

2004-01-01

New stratigraphic and geochronologic data from the Killpecker Dunes in southwestern Wyoming facilitate a more precise understanding of the dune field's history. Prior investigations suggested that evidence for late Pleistocene eolian activity in the dune field was lacking. However, luminescence ages from eolian sand of ???15,000 yr, as well as Folsom (12,950-11,950 cal yr B.P.) and Agate Basin (12,600-10,700 cal yr) artifacts overlying eolian sand, indicate the dune field existed at least during the latest Pleistocene, with initial eolian sedimentation probably occurring under a dry periglacial climate. The period between ???13,000 and 8900 cal yr B.P. was characterized by relatively slow eolian sedimentation concomitant with soil formation. Erosion occurred between ???8182 and 6600 cal yr B.P. on the upwind region of the dune field, followed by relative stability and soil formation between ???5900 and 2700 cal yr B.P. The first of at least two latest Holocene episodes of eolian sedimentation occurred between ???2000 and 1500 yr, followed by a brief (???500 yr) episode of soil formation; a second episode of sedimentation, occurring by at least ???700 yr, may coincide with a hypothesized Medieval warm period. Recent stabilization of the western Killpecker Dunes likely occurred during the Little Ice Age (???350-100 yr B.P.). The eolian chronology of the western Killpecker Dunes correlates reasonably well with those of other major dune fields in the Wyoming Basin, suggesting that dune field reactivation resulted primarily due to departures toward aridity during the late Quaternary. Similar to dune fields on the central Great Plains, dune fields in the Wyoming Basin have been active under a periglacial climate during the late Pleistocene, as well as under near-modern conditions during the latest Holocene. ?? 2003 University of Washington. All rights reserved.

Preliminary Vertical Slip Rate for the West Tahoe Fault from six new Cosmogenic 10Be Exposure Ages of Late Pleistocene Glacial Moraines at Cascade Lake, Lake Tahoe, California

NASA Astrophysics Data System (ADS)

Pierce, I. K. D.; Wesnousky, S. G.; Kent, G. M.; Owen, L. A.

2015-12-01

The West Tahoe Fault is the primary range bounding fault of the Sierra Nevada at the latitude of Lake Tahoe. It is a N-NW striking, east dipping normal fault that has a pronounced onshore quaternary scarp extending from highway 50 southwest of Meyers, CA to Emerald Bay. At Cascade Lake, the fault cuts and progressively offsets late Pleistocene right lateral moraines. The fault vertically offsets the previously mapped Tahoe moraine ~83 m and the Tioga moraine ~23 m, measured from lidar data. Seventeen samples were collected for 10Be cosmogenic age analysis from boulders on both the hanging and footwalls of the fault along the crests of these moraines.We report here the initial analysis of 6 of these boulders and currently await processing of the remainder. The 10Be exposure ages of 3 boulders each on the younger Tioga and older Tahoe moraines range from 12.7 +/- 1.6 to 20.7 +/- 3.3 ka and 13.3 +/- 2.1 to 72.5 +/- 8.8 ka, respectively. Using the oldest ages as minima, these preliminary results suggest that the slip rate has averaged ~1 mm/yr since the penultimate glaciation, in accord with estimates of previous workers, and place additional bounds on the age of glaciation in the Lake Tahoe basin. The Last Glacial Maxima and penultimate glaciation near Lake Tahoe thus appear to coincide with the Tioga and Tahoe II glaciations of the Eastern Sierra.

Spotted hyena and steppe lion predation behaviours on cave bears of Europe - ?Late Quaternary cave bear extinction as result of predator stress

NASA Astrophysics Data System (ADS)

Diedrich, Cajus G.

2010-05-01

Cave bears hibernated in caves all over Eurasia (e.g. Rabeder et al., 2000) including alpine regions using mainly larger caves for this purpose. Late Quaternary spotted hyenas Crocuta crocuta spelaea instead occupied mainly areas close to the cave entrances as their dens (Diedrich and Žák 2006, Diedrich 2010). The largest predator, the steppe lion Panthera leo spelaea was only a sporadic cave dweller (Diedrich 2007b, 2009b). His presence and its remains from caves all over Europe can be recently explained best as result of imported carcasses after killing by their largest antagonists, the Late Quaternary spotted hyenas. In some cases the kill might have happened in the hyena den cave itself during the theft of prey remains by lions (Diedrich 2009a). Another reason of their remains in caves of Europe is the hunting onto the herbivorous cave bears, especially during hibernation times, when megafauna prey was less available in the open environments (Diedrich 2009c). These lion remains from caves of Europe, nearly all of which were from adult animals, provide evidence of active predation by lions onto cave bears even in medium high alpine regions (Diedrich 2009b, in review). Lion skeletons in European cave bear dens were therefore often found amongst originally articulated cave bear skeletons or scattered cave bear remains and even close to their hibernation nests (Diedrich et al. 2009c, in review). Not only lions fed on cave bears documented mainly by the large quantities of chewed, punctured and crushed cave bear long-bones; even damaged skulls reveal that hyenas scavenged primarily on cave bear carcasses which were mainly responsible for the destruction of their carcasses and bones (Diedrich 2005, 2009d). Predation and scavenging on cave bears by the two largest Late Quaternary predators C. c. spelaea and P. l. spelaea explains well the large quantity of fragmented cave bear bones over all European caves in low to medium high mountainous elevations, whereas in

Assessment of geomorphological and hydrological changes produced by Pleistocene glaciations in a Patagonian basin

NASA Astrophysics Data System (ADS)

Scordo, Facundo; Seitz, Carina; Melo, Walter D.; Piccolo, M. Cintia; Perillo, Gerardo M. E.

2018-04-01

This work aims to assess how Pleistocene glaciations modeled the landscape in the upper Senguer River basin and its relationship to current watershed features (drainage surface and fluvial hydrological regime). During the Pleistocene six glacial lobes developed in the upper basin of the Senguer River localized east of the Andean range in southern Argentinean Patagonia between 43° 36' - 46° 27‧ S. To describe the topography and hydrology, map the geomorphology, and propose an evolution of the study area during the Pleistocene we employed multitemporal Landsat images, national geological sheets and a mosaic of the digital elevation model (Shuttle Radar Topography Mission) along with fieldwork. The main conclusion is that until the Middle Pleistocene, the drainage divide of the Senguer River basin was located to the west of its current limits and its rivers drained the meltwater of the glaciers during interglacial periods. However, processes of drainage inversion and drainage surface reduction occurred in the headwater of most rivers of the basin during the Late Pleistocene. Those processes were favored by a relative shorter glacial extension during LGM and the dam effect produced by the moraines of the Post GPG I and III glaciations. Thus, since the Late Pleistocene, the headwaters of several rivers in the basin have been reduced, and the moraines corresponding to the Middle Pleistocene glaciations currently divide the watersheds that drain towards the Senguer River from those that flow west towards the Pacific Ocean.

Ice thickness and topographic relief in glaciated landscapes of the western USA

NASA Astrophysics Data System (ADS)

Brocklehurst, Simon H.; Whipple, Kelin X.; Foster, David

2008-05-01

The development of relief in glaciated landscapes plays a crucial role in hypotheses relating climate change and tectonic processes. In particular, glaciers can only be responsible for peak uplift if they are capable of generating significant relief in formerly nonglaciated landscapes. Previous work has suggested that relief in glaciated landscapes should scale with the thickness of the ice. Here we summarise a field-based test of this hypothesis in two mountain ranges in the western United States, the Sierra Nevada, California, and the Sangre de Cristo Range, Colorado. These areas exhibit a range of degrees of glacial occupation during the Quaternary, including some drainage basins essentially unoccupied by ice, allowing a detailed exploration of how relief in different parts of a drainage basin evolves in response to glacial modification. We mapped last glacial maximum (LGM) trimlines to estimate the ice thickness at the equilibrium line altitude during the LGM, and determined several metrics of relief for drainage basins across the full spectrum of LGM ice extents. Comparison between measures of relief and ice thickness estimates indicates that relief production in glaciated mountain belts scales with ice thickness and consequently also drainage area. We extended our study to the Bitterroot Range in Idaho/Montana, and the Teton Range in Wyoming, for a more comprehensive understanding of sub-ridgeline relief, or 'missing mass'. This measure of mean relief is surprisingly little affected by either the degree of glacial modification or the total material removed by glaciers, but appears to be influenced by the more active tectonics of the Teton Range. While the effects of glacial modification on the landscape are clear (valley widening, hanging valley formation), the overall change in the relief structure of the mountain ranges studied here is surprisingly modest.

Late Quaternary alluviation and offset along the eastern Big Pine fault, southern California

USGS Publications Warehouse

DeLong, S.B.; Minor, S.A.; Arnold, L.J.

2007-01-01

Determining late Quaternary offset rates on specific faults within active mountain belts is not only a key component of seismic hazard analysis, but sheds light on regional tectonic development over geologic timescales. Here we report an estimate of dip-slip rate on the eastern Big Pine oblique-reverse fault in the upper Cuyama Valley within the western Transverse Ranges of southern California, and its relation to local landscape development. Optically stimulated luminescence (OSL) dating of sandy beds within coarse-grained alluvial deposits indicates that deposition of alluvium shed from the Pine Mountain massif occurred near the southern margin of the Cuyama structural basin at the elevation of the Cuyama River between 25 and 14??ka. This alluvial deposit has been offset ??? 10??m vertically by the eastern Big Pine fault, providing a latest Quaternary dip-slip rate estimate of ??? 0.9??m/ky based on a 50?? fault dip. Incision of the adjacent Cuyama River has exposed a section of older Cuyama River sediments beneath the Pine Mountain alluvium that accumulated between 45 and 30??ka on the down-thrown footwall block of the eastern Big Pine fault. Corroborative evidence for Holocene reverse-slip on the eastern Big Pine fault is ??? 1??m of incised bedrock that is characteristically exposed beneath 2-3.5??ka fill terraces in tributaries south of the fault. The eastern Big Pine fault in the Cuyama Valley area has no confirmed record of historic rupture; however, based on our results, we suggest the likelihood of multiple reverse-slip rupture events since 14??ka. ?? 2007 Elsevier B.V. All rights reserved.

Late Quaternary environmental dynamics in the Atacama Desert reconstructed from rodent midden pollen records

USGS Publications Warehouse

de Porras, M.E.; Maldonado, A.; De Pol-Holz, R.; Latorre, C.; Betancourt, Julio L.

2017-01-01

In the past two decades, much has been learned about the late Quaternary climate history of the Atacama Desert with some details still unclear about the seasonality, timing and extent of wet and dry phases. Modern climate studies reveal that, far from exhibiting a unique pattern, seasonal precipitation originates from many sources and mechanisms. For the last 16 ka, we attempt to sort out these complexities in pollen records from four fossil rodent midden series spanning 22°–25°S in northern Chile. Widespread wet conditions prevailed during the late Pleistocene and early Holocene, particularly between 13 and 9 ka, evidenced by <400 m lowering of pollen zones (plant communities) compared to today. Regional differences in the timing and magnitude of this displacement may be related to the prevailing source (tropical/extra‐tropical) or mode (NNW/SE) of tropical precipitation through time. Wet conditions persisted well into the early Holocene, lasting ∼1–1.5 ka longer than previously suggested. The pollen record suggests extreme drying ∼8 ka, possibly associated with a northward shift of the Inter Tropical Convergence Zone, tracking minimum insolation values at subtropical latitudes during the austral summer. The establishment of conditions similar to today happened ∼4 ka. 

Ice-Sheet Glaciation of the Puget lowland, Washington, during the Vashon Stade (late pleistocene)

USGS Publications Warehouse

Thorson, R.M.

1980-01-01

During the Vashon Stade of the Fraser Glaciation, about 15,000-13,000 yr B.P., a lobe of the Cordilleran Ice Sheet occupied the Puget lowland of western Washington. At its maximum extent about 14,000 yr ago, the ice sheet extended across the Puget lowland between the Cascade Range and Olympic Mountains and terminated about 80 km south of Seattle. Meltwater streams drained southwest to the Pacific Ocean and built broad outwash trains south of the ice margin. Reconstructed longitudinal profiles for the Puget lobe at its maximum extent are similar to the modern profile of Malaspina Glacier, Alaska, suggesting that the ice sheet may have been in a near-equilibrium state at the glacial maximum. Progressive northward retreat from the terminal zone was accompanied by the development of ice-marginal streams and proglacial lakes that drained southward during initial retreat, but northward during late Vashon time. Relatively rapid retreat of the Juan de Fuca lobe may have contributed to partial stagnation of the northwestern part of the Puget lobe. Final destruction of the Puget lobe occurred when the ice retreated north of Admiralty Inlet. The sea entered the Puget lowland at this time, allowing the deposition of glacial-marine sediments which now occur as high as 50 m altitude. These deposits, together with ice-marginal meltwater channels presumed to have formed above sea level during deglaciation, suggest that a significant amount of postglacial isostatic and(or) tectonic deformation has occurred in the Puget lowland since deglaciation. ?? 1980.

The Lower Molopo River super site (SW Kalahari) and its relevance for the analysis of supra-regional Late Quaternary climate and land-use changes in Southern Africa

NASA Astrophysics Data System (ADS)

Winkelbauer, Jennifer; Völkel, Jörg; Bens, Oliver; Heine, Klaus

2013-04-01

The semi-arid to semi-humid Kalahari of southern Africa is a region with enormous climatic fluctuations due to recent and former shifting of tropical and subtropical atmospheric circulation patterns and changing climatic factors. Although it is clear that large, rapid temperature changes have occurred during the Late Quaternary, we have only limited, and often imprecise, knowledge of how the major moisture-bearing atmospheric circulation systems have reacted to these changes. During the Last Glacial Maximum (LGM) a transition zone existed at approximately 24° S that was characterized by the overlap of alternating tropical summer rain in the north (ITCZ) and subtropical winter rain (Westerlies) in the south. As part of this transition zone, the study area of the Lower Molopo River valley (20-21° E and 26° 45'-28° 40'S) offers ideal conditions for terrestrial research on Late Quaternary paleoclimate and environmental changes. Here dunes, pans, slopes and river terraces coexist as major geomorphological types in an ideal way, including different fluvial sediment facies interbedded with slope and eolian sediments, as well as the confluence of the Molopo and Orange River systems. Such geoarchives are typically modified by climatic fluctuations and changes. To assess the paleoclimatic information in time and space, physico-chemical parameters of the sediment archives must be determined to clearly characterize single sediment types and their spatial interrelation. Particularly the interpretation of stratigraphical interbeddings of different sediment facies delivers types, directions or intensities of alternating processes. The sedimentological analysis is systematically combined with OSL- and 14C-dating techniques. The results of our analysis on dune development and fluvial activity comprehensively clarify the chronology of significant shifts in Late Quaternary river regimes, rainfall inputs and atmospheric circulation patterns (Hürkamp et al. 2011) and will be

Quaternary Geologic Map of Connecticut and Long Island Sound Basin

USGS Publications Warehouse

Stone, Janet Radway; Schafer, John P.; London, Elizabeth Haley; DiGiacomo-Cohen, Mary L.; Lewis, Ralph S.; Thompson, Woodrow B.

2005-01-01

The Quaternary geologic map (sheet 1) and explanatory figures and cross sections (sheet 2) portray the geologic features formed in Connecticut during the Quaternary Period, which includes the Pleistocene (glacial) and Holocene (postglacial) Epochs. The Quaternary Period has been a time of development of many details of the landscape and of all the surficial deposits. At least twice in the late Pleistocene, continental ice sheets swept across Connecticut. Their effects are of pervasive importance to the present occupants of the land. The Quaternary geologic map illustrates the geologic history and the distribution of depositional environments during the emplacement of glacial and postglacial surficial deposits and the landforms resulting from those events.

Climate warming and humans played different roles in triggering Late Quaternary extinctions in east and west Eurasia.

PubMed

Wan, Xinru; Zhang, Zhibin

2017-03-29

Climate change and humans are proposed as the two key drivers of total extinction of many large mammals in the Late Pleistocene and Early Holocene, but disentangling their relative roles remains challenging owing to a lack of quantitative evaluation of human impact and climate-driven distribution changes on the extinctions of these large mammals in a continuous temporal-spatial dimension. Here, our analyses showed that temperature change had significant effects on mammoth (genus Mammuthus ), rhinoceros (Rhinocerotidae), horse (Equidae) and deer (Cervidae). Rapid global warming was the predominant factor driving the total extinction of mammoths and rhinos in frigid zones from the Late Pleistocene and Early Holocene. Humans showed significant, negative effects on extirpations of the four mammalian taxa, and were the predominant factor causing the extinction or major extirpations of rhinos and horses. Deer survived both rapid climate warming and extensive human impacts. Our study indicates that both the current rates of warming and range shifts of species are much faster than those from the Late Pleistocene to Holocene. Our results provide new insight into the extinction of Late Quaternary megafauna by demonstrating taxon-, period- and region-specific differences in extinction drivers of climate change and human disturbances, and some implications about the extinction risk of animals by recent and ongoing climate warming. © 2017 The Author(s).

Late Pleistocene glaciations of the arid subtropical Andes and new results from the Chajnantor Plateau, northern Chile

NASA Astrophysics Data System (ADS)

Ward, Dylan J.; Cesta, Jason M.; Galewsky, Joseph; Sagredo, Esteban

2015-11-01

The spatiotemporal pattern of glaciation along the Andes Mountains is an important proxy record reflecting the varying influence of global and regional circulation features on South American climate. However, the timing and extent of glaciation in key parts of the orogen, particularly the deglaciated arid Andes, are poorly constrained. We present new cosmogenic 10Be and 36Cl exposure ages for glacial features on and near the Chajnantor Plateau (23 °S). The new dates, although scattered due to cosmogenic inheritance, imply that the most recent extensive glacial occupation ended before or during the global Last Glacial Maximum (LGM). We discuss this new record in the context of published glacial chronologies from glacial features in Peru, Bolivia, and northern Chile rescaled using the latest cosmogenic 10Be production rate calibration for the tropical Andes. The results imply regionally synchronous moraine stabilization ca. 25-40 ka, 15-17 ka, and 12-14 ka, with the youngest of these moraines absent in records south of ∼20 °S, including in our new Chajnantor area chronology. This spatial pattern implicates easterly moisture in generating sufficient snowfall to glaciate the driest parts of the Andes, while allowing a role for westerly moisture, possibly modulated by the migration of the Southern Westerly Wind belt, in the regions near and south of the Atacama Desert.

Do coastal fronts influence bioerosion patterns along Patagonia? Late Quaternary ichnological tools from Golfo San Jorge

NASA Astrophysics Data System (ADS)

Richiano, Sebastián; Aguirre, Marina; Castellanos, Ignacio; Davies, Karen; Farinati, Ester

2017-12-01

Late Quaternary marine molluscan skeletal concentrations from Argentina constitute a remarkable record of variations in palaeoceanographical conditions during interglacial times (mainly ca. 125 ka to present). Particularly, the Golfo San Jorge coastal area represents an extraordinary geographical zone to target from different points of view, mainly due to its linkage between northern and southern Patagonia, characterized by particular and contrasting physico-chemical conditions with direct consequences for littoral marine communities, determining their composition and structure. Among varied biological activities controlled by different environmental factors (i.e., substrate nature, sedimentation rates, water depth, sea surface temperature, salinity, nutrients-productivity), bioerosion traces can provide palaeoenvironmental evidence with important implications for palaeoclimate interpretations. In addition, the application of bioerosion patterns regionally and through time is a recent valuable worthy palaeoenvironmental tool not as yet developed for Patagonia. We attempted to characterize, qualitatively/semiquantitatively, the ichnotaxonomic composition of the coastal area of northern Golfo San Jorge since the Late Pleistocene; to compare results with those obtained for other geographical areas along Patagonia and the Bonaerensian coastal sectors; lastly, to evaluate its palaeoenvironmental/palaeoclimatic significance in a clue area in terms of circulation patterns near the Southern Ocean climatic pump. At Bustamante (Northern Patagonia Frontal System) Domichnia traces were dominant during the Late Pleistocene while Praedichnia in the mid-Holocene. Bustamante exhibits the highest ichnodiversity for the whole Argentinean coastal area. Ichnodiversity is not strongly different between Late Pleistocene and mid-Holocene interglacials and compared to present; however, the relative abundance of some ichnotaxa (e.g., Oichnus, Iramena, Pennatichnus, at Camarones; Oichnus

Century scale climatic rhythms in the equatorial Indian Ocean during the late Quaternary: Faunal and geochemical proxies from the Maldivian Archipelago

NASA Astrophysics Data System (ADS)

Sarkar, S.; Gupta, A. K.

2012-04-01

The equatorial Indian Ocean is swept by the Indian Ocean equatorial westerlies (IEW) which are strong during monsoon transitions in April-May and October-November, driving Eastward Equatorial Current (EEC) in the upper ocean. This study is based on the biogenic sediments from Ocean Drilling Program (ODP) Hole 716A, recovered beneath the narrow equatorial track (7 Degree North to 7 Degree South) along which the IEW prevail. We analyzed 300 Kyr record of benthic and planktic foraminifera, pteropods combined with stable isotope values measured on planktic foraminifer Globigerinoides ruber from 451 core samples to understand paleoceanographic and paleoclimatic changes in the equatorial Indian Ocean during the late Quaternary (~450 - 150 Kyrs). Factor and cluster analyses of the 53 highest-ranked benthic foraminiferal species enabled to identify five biofacies, indicating varied nature of deep-sea environments during the late Quaternary, with a major shift across the middle Brunhes epoch (across Marine Isotope Stage 9 and 8). Biofacies Robulus nicobarensis - Trifarina reussi (Rn-Tr), Uvigerina porrecta - Reussella simplex (Upo-Rs) and Cymbaloporetta squammosa - Bolivinita sp. (Cs-Bsp) document high organic flux with low oxygen paleoenvironment dominating before the mid-Brunhes event, similar to Globigerina bulloides population, while benthic foraminiferal biofacies Hoeglundina elegans - Miliolinella subrotunda (He-Ms) and Uvigerina peregrina - Quinqueloculina seminulum (Upe-Qs) record high seasonality in food supply with well-oxygenated deep water after ~300 Kyr. These changes are also visible in planktic foraminifera and pteropod record. In the present day, the strength of the IEW is inversely related to the Indian Ocean Dipole (IOD). The IEW weakened across MIS 9/8 during which time the IOD strengthened, causing heavy rains and floods over the equatorial East Africa and deficient rainfall over Australasia. The proxy response changed from low to high frequency cycles

Deciphering tectonic, climatic-induced and hydrothermal signals in the late-stage exhumation history of the upper Rhône valley (Swiss Alps)

NASA Astrophysics Data System (ADS)

Valla, Pierre; Rahn, Meinert; Shuster, David; van der Beek, Peter

2015-04-01

Neogene exhumation of the European Alps is understood as the interplay between tectonics and climatic-induced erosion. While the former has been influenced by a decrease in plate convergence, the latter has been suggested to be affected by climatic variation and the onset of Plio-Quaternary glaciations, leading to relief amplification. However, even though geomorphologic and sedimentologic studies both suggest topographic relief change and transition from fluvial to oscillations between glacial/fluvial conditions, precise quantification on both the timing and magnitude of this transition are yet sparse. Our study focuses on the upper Rhône valley (Swiss Central Alps) within the Visp-Brig area (Aar massif). This area encompasses some of the most spectacular reliefs within the Alps with several nearby summits around or above 4000 m crosscut by the glacially overdeepened Rhône valley. It also shows among the highest late Neogene exhumation rates within the Western-Central European Alps, influenced by tectonic activity along the major Simplon-Rhône extensional fault system. Moreover, the upper Rhône valley has experienced enhanced glacial erosion associated with strong relief development during the Pliocene-Quaternary period. Finally, structural inheritance, late-stage tectonics and rapid exhumation may have promoted recent hydrothermal activity in this region, although timing of its onset and its precise causes remain poorly understood. We investigated the late-stage cooling history by using different low-temperature thermochronometers along a pseudo-vertical bedrock profile (elevation between 600 and 2900 m) and additional samples from an on-site 500-m geothermal well, resulting in a total elevation difference of nearly 3 km. Apatite fission-track (AFT) ages and track-length data have been added to previously published and new apatite (U-Th-Sm)/He (AHe) and 4He/3He data. Our results confirm high-exhumation rates (0.6 to 0.9 km/Myr) within late-Cenozoic to

Late Quaternary Productivity Records from Coccolith Sr/Ca

NASA Astrophysics Data System (ADS)

Stoll, H. M.; Burke, A.; Mejia Ramirez, L. M.; Shimizu, N.; Ziveri, P. P. I.

2014-12-01

The Sr/Ca of coccoliths has been proposed as an indicator of productivity on the basis of correlation with export production in sediment traps and across upwelling productivity gradients, although the mechanism responsable for this relationship is not clear. For diverse oceanographic settings in the Late Quaternary, we compare coccolith Sr/Ca productivity records with those of other productivity indicators and proxies for mechanisms of productivity forcing. For the Somalia Basin in the Arabian Sea, coccolith Sr/Ca shows a large variation coherent with precessional forcing of wind strength as a mechanism for productivity regulation. During the glacial, the Sr/Ca peak is decoupled from productivity indicators based on organic C accumulation rate. For the Northern Bay of Bengal, coccolith Sr/Ca, Ba/Ti, and relative abundance of G. bulloides, all suggest greater productivity during the interglacial periods, consisted with Nd isotopic evidence for greater riverine nutrient inputs. In the Andaman Sea, coccolith Sr/Ca is highest during precessional maxima in the summer monsoon, consistent with proxies for chemical weathering in the Irawaddy rivershed. In the Eastern Mediterranean, coccolith Sr/Ca is on average low, and peaks during the E. Holocene interval characterized by deposition of sapropel S1. The peak in Sr/Ca however is comparable to the level maintained throughout the Holocene in the Western Mediterranean, where no sapropel occurs, implicating deepwater oxygen levels as a significant contributor to sapropel formation. Finally, on the Agulhas Bank, minima in coccolith Sr/Ca occur during obliquity minima which are periods of anomalous equatorward deposition of IRD in the Southern Ocean. Northward explansion of the westerly wind field during these cold intervals, block upwelling on the Agulhas Bank and result in low productivity.

New insights into the earliest Quaternary environments in the Central North Sea from 3D seismic

NASA Astrophysics Data System (ADS)

Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

2014-05-01

In the past the transition between an unconformable surface in the south to a conformable horizon towards the north has made identification and mapping the base-Quaternary in the central North Sea difficult (Sejrup et al 1991; Gatliff et al 1994). However recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) has allowed greater confidence in the correlation to the region 3D seismic datasets and thus has allowed the base-Quaternary to be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The revised base-Quaternary surface reaches a depth of 1248 ms TWT with an elongate basin shape which is significantly deeper than the traditionally mapped surface. Using RMS amplitudes and other seismic attributes the revised base-Quaternary has been investigated along the horizon and in time slice to interpret the environments of the earliest Quaternary prior to the onset of glaciation. Combined with analysis of aligned elongate furrows over 10 km long, 100 m wide and 100 m deep suggest a deep marine environment in an almost enclosed basin with persistent strong NW-SE bottom currents in the deepest parts. Pockmarks were formed by the escape of shallow gas on the sides of a small delta in the eastern part of the basin. The progradation of large deltas from both the north and south into the basin make up the majority of the deposition of sediment into the basin. Key Words: base-Quaternary; seismic interpretation; paleoenvironments References: Gatliff, R.W, Richards, P.C, Smith, K, Graham, C.C, McCormac, M, Smith, N.J.P, Long, D, Cameron, T.D.J, Evans, D, Stevenson, A.G, Bulat, J, Ritchie, J.D, (1994) 'United Kingdom offshore regional

Imprint of Late Quaternary Climate Change on the Mid-Atlantic Landscape

NASA Astrophysics Data System (ADS)

Pavich, M.; Markewich, H.; Newell, W. L.; Litwin, R.; Smoot, J.; Brook, G.

2009-12-01

Recent geomorphic, lithostratigraphic, palynologic and chronostratigraphic investigations of the mid-Atlantic region show that much of the modern landscape flanking the Chesapeake Bay and the Potomac River is developed on late Quaternary sediments. These deposits, dated by OSL and 14C, include transgressive marine and estuarine sediments deposited between 120ka and 32ka, and parabolic dunes formed between 32ka and 15ka. The stacked estuarine units were deposited in a subsiding basin as eustatic sea level fell from +7m to -60m. The estuarine units contain pollen that provides evidence for millennial scale climate fluctuations. The dunes formed during the period of rapid expansion of the Laurentide Ice Sheet as sea level fell to -120m. Permafrost features such as frost wedges and periglacial “pots” formed during cold intervals associated with marine oxygen isotope stages 4 and 2. This periglacial climate, along with glacioisostatic adjustments to growth and decay of the Laurentide Ice Sheet, affected landscape processes at least as far south as the Potomac River valley. While many of these features were recognized in earlier mapping and stratigraphic investigations, OSL dating has greatly extended the range of available dates and significantly improved our understanding of the impacts of highly variable periglacial climate on this region.

Late Quaternary stratigraphy, sedimentology, and geochemistry of an underfilled lake basin in the Puna (north-west Argentina)

USGS Publications Warehouse

McGlue, Michael M.; Cohen, Andrew S.; Ellis, Geoffrey S.; Kowler, Andrew L.

2013-01-01

Depositional models of ancient lakes in thin-skinned retroarc foreland basins rarely benefit from appropriate Quaternary analogues. To address this, we present new stratigraphic, sedimentological and geochemical analyses of four radiocarbon-dated sediment cores from the Pozuelos Basin (PB; northwest Argentina) that capture the evolution of this low-accommodation Puna basin over the past ca. 43 cal kyr. Strata from the PB are interpreted as accumulations of a highly variable, underfilled lake system represented by lake-plain/littoral, profundal, palustrine, saline lake and playa facies associations. The vertical stacking of facies is asymmetric, with transgressive and thin organic-rich highstand deposits underlying thicker, organic-poor regressive deposits. The major controls on depositional architecture and basin palaeogeography are tectonics and climate. Accommodation space was derived from piggyback basin-forming flexural subsidence and Miocene-Quaternary normal faulting associated with incorporation of the basin into the Andean hinterland. Sediment and water supply was modulated by variability in the South American summer monsoon, and perennial lake deposits correlate in time with several well-known late Pleistocene wet periods on the Altiplano/Puna plateau. Our results shed new light on lake expansion–contraction dynamics in the PB in particular and provide a deeper understanding of Puna basin lakes in general.

Glaciation as a destructive and constructive control on mountain building.

PubMed

Thomson, Stuart N; Brandon, Mark T; Tomkin, Jonathan H; Reiners, Peter W; Vásquez, Cristián; Wilson, Nathaniel J

2010-09-16

Theoretical analysis predicts that enhanced erosion related to late Cenozoic global cooling can act as a first-order influence on the internal dynamics of mountain building, leading to a reduction in orogen width and height. The strongest response is predicted in orogens dominated by highly efficient alpine glacial erosion, producing a characteristic pattern of enhanced erosion on the windward flank of the orogen and maximum elevation controlled by glacier equilibrium line altitude, where long-term glacier mass gain equals mass loss. However, acquiring definitive field evidence of an active tectonic response to global climate cooling has been elusive. Here we present an extensive new low-temperature thermochronologic data set from the Patagonian Andes, a high-latitude active orogen with a well-documented late Cenozoic tectonic, climatic and glacial history. Data from 38° S to 49° S record a marked acceleration in erosion 7 to 5 Myr ago coeval with the onset of major Patagonian glaciation and retreat of deformation from the easternmost thrust front. The highest rates and magnitudes of erosion are restricted to the glacial equilibrium line altitude on the windward western flank of the orogen, as predicted in models of glaciated critical taper orogens where erosion rate is a function of ice sliding velocity. In contrast, towards higher latitudes (49° S to 56° S) a transition to older bedrock cooling ages signifies much reduced late Cenozoic erosion despite dominantly glacial conditions here since the latest Miocene. The increased height of the orogenic divide at these latitudes (well above the equilibrium line altitude) leads us to conclude that the southernmost Patagonian Andes represent the first recognized example of regional glacial protection of an active orogen from erosion, leading to constructive growth in orogen height and width.

The history of Antarctic Peninsula glaciation

USGS Publications Warehouse

Barker, Peter F.

2007-01-01

As Co-Chief Scientist on DSDP Leg 35 in 1974, Cam Craddock (1930-2006) produced the first useful information on Cenozoic Antarctic Peninsula glaciation - an early middle Miocene (15-17 Ma) apparent glacial onset. Subsequent work, onshore and offshore, has greatly extended our knowledge but that early conclusion stands today. Cenozoic Antarctic Peninsula palaeoclimate as presently known is broadly consistent with global palaeoclimate proxies. Initial glacial onset was within the Eocene-Oligocene boundary interval (although earlier, short-lived glaciations have been proposed, from indirect measurements) and the peninsula probably became deglaciated in the earliest Miocene (ca. 24 Ma). The renewed middle Miocene glaciation probably continued to the present and, for the last 9 Myr at least, has persisted through glacial (orbital) cycles, with grounded ice advance to the shelf edge during maxima. Although orbital cyclicity affected earlier AP palaeoclimate also, the level of glaciation through a complete cycle is uncertain.

Response to comment on "No late Quaternary strike-slip motion along the northern Karakoram fault"

NASA Astrophysics Data System (ADS)

Robinson, Alexander C.; Owen, Lewis A.; Chen, Jie; Schoenbohm, Lindsay M.; Hedrick, Kathryn A.; Blisniuk, Kimberly; Sharp, Warren D.; Imrecke, Daniel B.; Li, Wenqiao; Yuan, Zhaode; Caffee, Marc W.; Mertz-Kraus, Regina

2016-06-01

In their comment on ;No late Quaternary strike-slip motion along the northern Karakoram fault;, while Chevalier et al. (2016) do not dispute any of the results or interpretations regarding our observations along the main strand of the northern Karakoram fault, they make several arguments as to why they interpret the Kongur Shan Extensional System (KES) to be kinematically linked to the Karakoram fault. These arguments center around how an ;active; fault is defined, how slip on segments of the KES may be compatible with dextral shear related to continuation of the Karakoram fault, and suggestions as to how the two fault systems might still be connected. While we appreciate that there are still uncertainties in the regional geology, we address these comments and show that their arguments are inconsistent with all available data, known geologic relationships, and basic kinematics.

Seismic stratigraphy and late Quaternary shelf history, south-central Monterey Bay, California

USGS Publications Warehouse

Chin, J.L.; Clifton, H.E.; Mullins, H.T.

1988-01-01

The south-central Monterey Bay shelf is a high-energy, wave-dominated, tectonically active coastal region on the central California continental margin. A prominent feature of this shelf is a sediment lobe off the mouth of the Salinas River that has surface expression. High-resolution seismic-reflection profiles reveal that an angular unconformity (Quaternary?) underlies the entire shelf and separates undeformed strata above it from deformed strata below it. The Salinas River lobe is a convex bulge on the shelf covering an area of approximately 72 km2 in water depths from 10 to 90 m. It reaches a maximum thickness of 35 m about 2.5 km seaward of the river mouth and thins in all directions away from this point. Adjacent shelf areas are characterized by only a thin (2 to 5 m thick) and uniform veneer of sediment. Acoustic stratigraphy of the lobe is complex and is characterized by at least three unconformity-bounded depositional sequences. Acoustically, these sequences are relatively well bedded. Acoustic foresets occur within the intermediate sequence and dip seaward at 0.7?? to 2.0??. Comparison with sedimentary sequences in uplifted onshore Pleistocene marine-terrace deposits of the Monterey Bay area, which were presumably formed in a similar setting under similar processes, suggests that a general interpretation can be formulated for seismic stratigraphic patterns. Depositional sequences are interpreted to represent shallowing-upwards progradational sequences of marine to nonmarine coastal deposits formed during interglacial highstands and/or during early stages of falling sea level. Acoustic foresets within the intermediate sequence are evidence of seaward progradation. Acoustic unconformities that separate depositional sequences are interpreted as having formed largely by shoreface planation and may be the only record of the intervening transgressions. The internal stratigraphy of the Salinas River lobe thus suggests that at least several late Quaternary

Exceptionally well preserved late Quaternary plant and vertebrate fossils from a blue hole on Abaco, The Bahamas.

PubMed

Steadman, David W; Franz, Richard; Morgan, Gary S; Albury, Nancy A; Kakuk, Brian; Broad, Kenneth; Franz, Shelley E; Tinker, Keith; Pateman, Michael P; Lott, Terry A; Jarzen, David M; Dilcher, David L

2007-12-11

We report Quaternary vertebrate and plant fossils from Sawmill Sink, a "blue hole" (a water-filled sinkhole) on Great Abaco Island, The Bahamas. The fossils are well preserved because of deposition in anoxic salt water. Vertebrate fossils from peat on the talus cone are radiocarbon-dated from approximately 4,200 to 1,000 cal BP (Late Holocene). The peat produced skeletons of two extinct species (tortoise Chelonoidis undescribed sp. and Caracara Caracara creightoni) and two extant species no longer in The Bahamas (Cuban crocodile, Crocodylus rhombifer; and Cooper's or Gundlach's Hawk, Accipiter cooperii or Accipiter gundlachii). A different, inorganic bone deposit on a limestone ledge in Sawmill Sink is a Late Pleistocene owl roost that features lizards (one species), snakes (three species), birds (25 species), and bats (four species). The owl roost fauna includes Rallus undescribed sp. (extinct; the first Bahamian flightless rail) and four other locally extinct species of birds (Cooper's/Gundlach's Hawk, A. cooperii/gundlachii; flicker Colaptes sp.; Cave Swallow, Petrochelidon fulva; and Eastern Meadowlark, Sturnella magna) and mammals (Bahamian hutia, Geocapromys ingrahami; and a bat, Myotis sp.). The exquisitely preserved fossils from Sawmill Sink suggest a grassy pineland as the dominant plant community on Abaco in the Late Pleistocene, with a heavier component of coppice (tropical dry evergreen forest) in the Late Holocene. Important in its own right, this information also will help biologists and government planners to develop conservation programs in The Bahamas that consider long-term ecological and cultural processes.

Paleomagnetic investigation of late Quaternary sediments of south San Francisco Bay, California

USGS Publications Warehouse

Hillhouse, John W.

1977-01-01

Paleomagnetic inclinations of the Late Quaternary sediments of South San Francisco Bay were determined from bore hole samples collected near Dumbarton Bridge. The sediments consist of estuarine muds and nonmarine sand deposits, floored by bedrock of the Mesozoic Franciscan Formation. - Beneath Dumbarton Bridge the entire sedimentary fill is normally polarized; therefore, the fill postdates the Brunhes-Matayama polarity reversal (700,000 y. B.P.). Magnetic time lines such as the Mono Lake excursion (24,000 y. B.P.) and the reversed Blake event (110,000 y B.P.) were not found in this bore hole. In addition to Holocene and modern deposits of San Francisco Bay, an older estuarine unit occurs in the stratigraphic section. The older unit was deposited during a period of high sea level, tentatively correlated with the Sangamon interglacial period. Because evidence of the Blake event is not present in the older estuarine unit, the proposed age of this unit could not be confirmed. Although the Holocene estuarine deposits of South San Francisco Bay carry stable remanent magnetization, a reliable record of geomagnetic secular variation could not be recovered because the water-saturated sdiment was deformed by drilling.

Late Quaternary palaeolakes, rivers, and wetlands on the Bolivian Altiplano and their palaeoclimatic implications

NASA Astrophysics Data System (ADS)

Rigsby, Catherine A.; Platt Bradbury, J.; Baker, Paul A.; Rollins, Stephanie M.; Warren, Michelle R.

2005-10-01

Drill cores of sediments from the Rio Desaguadero valley, Bolivia, provide new information about the climate of tropical South America over the past 50 000 years. The modern Rio Desaguadero is fed by Lake Titicaca overflow (and by local tributaries) in the wetter northern Altiplano and discharges into Lake Poopo in the more arid central Altiplano. During the late Quaternary the Rio Desaguadero valley was the site of several generations of palaeolakes and wetlands that formed during periods of increased precipitation and local runoff, augmented by increased overflow from Lake Titicaca. Sediments recovered by drilling in eight localities along the 390-km long valley of the Rio Desaguadero yield a regional history of lacustrine sedimentation and effective precipitation. Lacustrine strata in the drill cores record 12 distinct wet periods in the past 50 000 years. Four of these wet periods resulted in the formation of major palaeolakes in the Rio Desaguadero valley: during the last glacial maximum from before 20 000 to 16 000 cal. yr BP, during the late glacial from about 14 000 to 12 000 cal. yr BP, in the early Holocene from about 10 000 to 7900 cal. yr BP, and in the late Holocene from 4500 cal. yrBP to present. The period that appears to have been most arid was between 7900 and 4500cal.yrBP. The Altiplano wet periods were generally synchronous with North Atlantic cold events (respectively, the last glacial maximum, the Younger Dryas, the 8200cal.yrBP event, and the Neoglacial) implying a relationship between past precipitation variability in tropical South America and North Atlantic sea-surface temperature.

Assessing Biological and Stratigraphic Determinants of Fossil Abundance: A Case Example from the Late Quaternary of Po Plain, Italy

NASA Astrophysics Data System (ADS)

Kowalewski, Michal; Azzarone, Michele; Kusnerik, Kristopher; Dexter, Troy; Wittmer, Jacalyn; Scarponi, Daniele

2017-04-01

Absolute fossil abundance [AFA] can be defined as a relative concentration of identifiable fossils per unit of sediment. AFA, or "sediment shelliness", is controlled by the interplay between the rate of input of skeletal remains (biological productivity), pace of shell destruction (taphonomy), rate of sedimentation, and sediment compaction. Understanding the relative importance of those drivers can augment both stratigraphic and biological interpretations of the fossil record. Using 336 samples from a network of late Quaternary cores drilled in Po Plain (Italy), we examined the importance of those factors in controlling the stratigraphic distribution of fossils. All samples were vertically and volumetrically equivalent, each representing a 10 cm long interval of a core with a diameter of 7 cm ( 0.375 dm3 sediment per sample). Sample-level estimates of AFA (1) varied over 4 orders of magnitudes (from <4 to 44200 specimens per dm3 of sediment); (2) appeared invariant to core depth (rho=-0.04, p=0.72); (3) were statistically indistinguishable (chi-square=1.53, p=0.46) across systems tracts; and (4) did not vary substantially across facies (chi-square=6.04, p=0.20) representing a wide range of depositional and taphonomic settings. These outcomes indicate that compaction (which should increase downcore), sedimentation rates (which vary predictably across systems tracts), and pace of shell destruction (expected to differ across depositional settings) are unlikely to have played important role in controlling fossils density in the sampled cores. In contrast, samples with very high shell density (AFA > 4000 specimens per dm3) were characterized by exceedingly low evenness reflecting dominance by one super-abundant species (Berger-Parker index > 0.8 in all cases). These super-abundant species were limited to small r-selective mollusks capable of an explosive population growth: the marine corbulid bivalve Lentidium mediterraneum and the brackish hyrdobiid gastropod Ecrobia

Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

USGS Publications Warehouse

Vazquez, Jorge A.; Woolford, Jeff M

2015-01-01

The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ∼1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ∼17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ∼17 ka, and produced a lava flow field covering ∼35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

Late Quaternary chronostratigraphic framework of terraces and alluvium along the lower Ohio River, southwestern Indiana and western Kentucky, USA

USGS Publications Warehouse

Counts, Ronald C.; Murari, Madhav K.; Owen, Lewis A.; Mahan, Shannon; Greenan, Michele

2015-01-01

The lower Ohio River valley is a terraced fluvial landscape that has been profoundly influenced by Quaternary climate change and glaciation. A modern Quaternary chronostratigraphic framework was developed for the lower Ohio River valley using optically stimulated luminescence (OSL) dating and allostratigraphic mapping to gain insights into the nature of fluvial responses to glacial–interglacial/stadial–interstadial transitions and Holocene climate change. River deposits, T0 (youngest) to T7 (oldest), were mapped along a 75 km reach of the lower Ohio River and were dated using 46 OSL and 5 radiocarbon samples. The examination of cores combined with OSL and radiocarbon dating shows that fluvial sediments older than marine oxygen isotope stage (MIS) 2 are present only in the subsurface. Aggradation during MIS 6 (Illinoian glaciation) filled the valley to within ∼7 m of the modern floodplain, and by ∼114 ka (MIS 5e/Sangamon interglacial) the Ohio River had scoured the MIS 6 sediments to ∼22 m below the modern floodplain surface. There were no fluvial sediments in the valley with ages between MIS 5e and the middle of MIS 3. The MIS 3 ages (∼39 ka) and stratigraphic position of T5 deposits suggest the Ohio River aggraded 8–14 m during MIS 4 or MIS 3. Near the end of MIS 3, the Ohio River incised the mid Last Glacial (mid-Wisconsinan) deposits ∼10 m and began aggrading again by ∼30 ka. Aggradation continued into MIS 2, with maximum MIS 2 aggradation occurring before ∼21 ka, which is coincident with the global Last Glacial Maximum (LGM). As the Ohio River adjusted to changing fluxes in sediment load and discharge following the LGM, it formed a sequence of fill-cut terraces in the MIS 2 outwash that get progressively younger with decreasing elevation, ranging in age from ∼21 ka to ∼13 ka. From ∼14 ka to ∼13 ka the Ohio River rapidly incised ∼3 m to form a new terrace, and by ∼12 ka at the onset of the Holocene, the Ohio River

Late Quaternary Faulting in Southeastern Louisiana: A Natural Laboratory for Understanding Shallow Faulting in Deltaic Materials

NASA Astrophysics Data System (ADS)

Dawers, N. H.; McLindon, C.

2017-12-01

A synthesis of late Quaternary faults within the Mississippi River deltaic plain aims to provide a more accurate assessment of regional and local fault architecture, and interactions between faulting, sediment loading, salt withdrawal and compaction. This effort was initiated by the New Orleans Geological Society and has resulted in access to industry 3d seismic reflection data, as well as fault trace maps, and various types of well data and biostratigraphy. An unexpected outgrowth of this project is a hypothesis that gravity-driven normal faults in deltaic settings may be good candidates for shallow aseismic and slow-slip phenomena. The late Quaternary fault population is characterized by several large, highly segmented normal fault arrays: the Baton Rouge-Tepetate fault zone, the Lake Pontchartrain-Lake Borgne fault zone, the Golden Meadow fault zone (GMFZ), and a major counter-regional salt withdrawal structure (the Bay Marchand-Timbalier Bay-Caillou Island salt complex and West Delta fault zone) that lies just offshore of southeastern Louisiana. In comparison to the other, more northerly fault zones, the GMFZ is still significantly salt-involved. Salt structures segment the GMFZ with fault tips ending near or within salt, resulting in highly localized fault and compaction related subsidence separated by shallow salt structures, which are inherently buoyant and virtually incompressible. At least several segments within the GMFZ are characterized by marsh breaks that formed aseismically over timescales of days to months, such as near Adams Bay and Lake Enfermer. One well-documented surface rupture adjacent to a salt dome propagated over a 3 day period in 1943. We suggest that Louisiana's coastal faults make excellent analogues for deltaic faults in general, and propose that a series of positive feedbacks keep them active in the near surface. These include differential sediment loading and compaction, weak fault zone materials, high fluid pressure, low elastic

Loess sedimentation in Tibet: provenance, processes, and link with Quaternary glaciations

USGS Publications Warehouse

Sun, Jielun; Li, S.-H.; Muhs, D.R.; Li, B.

2007-01-01

Well-preserved loess deposits are found on the foothills of mountains along the middle reaches of the Yarlung Zangbo River in southern Tibet. Optically stimulated luminescence (OSL) dating is used to determine loess ages by applying the single-aliquot regeneration technique. Geochemical, mineralogical, and granulometric measurements were carried out to allow a comparison between loess from Tibet and the Chinese Loess Plateau. Our results demonstrate that (i) the loess deposits have a basal age of 13-11 ka, suggesting they accumulated after the last deglaciation, (ii) loess in southern Tibet has a "glacial" origin, resulting from eolian sorting of glaciofluvial outwash deposits from braided river channels or alluvial fans by local near-surface winds, and (iii) the present loess in the interior of Tibet has accumulated since the last deglaciation when increased monsoonal circulation provided an increased vegetation cover that was sufficient for trapping eolian silt. The lack of full-glacial loess is either due to minimal vegetation cover or possibly due to the erosion of loess as glaciofluvial outwash during the beginning of each interglacial. Such processes would have been repeated during each glacial-interglacial cycle of the Quaternary. ?? 2007 Elsevier Ltd. All rights reserved.

Geochemical and Sedimentological Records of Late Quaternary Climate Change, Lake Tanganyika, Tropical East Africa

NASA Astrophysics Data System (ADS)

Felton, A. A.; Russell, J. M.; Cohen, A. S.; Baker, M. E.; McGlue, M. M.; Lezzar, K. E.

2005-12-01

We have analyzed piston core records from Lake Tanganyika (western Tanzania, East African Rift Valley) to investigate possible signals of tropical paleoclimate change during the Late Quaternary. Long paleoclimate records from East Africa are of importance for understanding climatic processes such as the role of solar variability in regulating tropical climates at Milankovitch time scales, and the relationship between abrupt climate changes, migration of Intertropical Convergence Zone, and regional climate variability (Nicholson, 2000). However, records of pre-Holocene climate variability from tropical African lakes (>25ka) are still quite rare. Long records from Lake Tanganyika are of particular interest given the lake's antiquity and its demonstrated potential for producing high resolution (frequently annually laminated) sedimentary records (Cohen et al., 1993). We analyzed physical properties, grain size, total organic carbon, major, minor and trace element variability, and biogenic silica data for a 7.75 m core from the Kalya slope and horst region of central Lake Tanganyika at 640m water depth. Nine 14C dates provide an age model for the core, which spans ~62 cal kyr. Elemental concentrations preserved in Lake Tanganyika sediments record variability in deposition and runoff into the lake basin. Under conditions of rapid erosion, exposure and rapid weathering of bedrock has been shown to generate high concentrations of original silicate minerals enriched in soluble cations such as sodium and potassium, elements that are also biologically conservative. Prior to 40ka cal yr. core sediments are characterized by high magnetic susceptibility, intermediate levels of organic carbon, low to intermediate levels of biogenic silica, and fine grain size, indicative of relatively high precipitation. There is a profound decrease in magnetic susceptibility, a decrease in organic carbon and an increase in grain size at 40ka cal yr, which persists until ~16ka cal yr. Seismic

Late Quaternary landscape evolution, climate, and neotectonism along the eastern margin of the Puna Plateau: Pucará Valley, NW Argentina

NASA Astrophysics Data System (ADS)

McCarthy, J. A.; Schoenbohm, L. M.; Bierman, P. R.; Rood, D. H.

2013-12-01

The eastern margin of the Puna Plateau has been the focus of many studies seeking to link climatically-moderated surface processes and tectonism through dynamic feedbacks. However, evaluating any theories regarding climatic-tectonic feedbacks requires the determination of tectonic, climatic, and geomorphic chronologies across a wide region, from plateau to wedge-top to foreland. In this study, we contribute to that effort by examining Quaternary landscape evolution of a single intermontane basin of spatially uniform climate, adjacent to the plateau margin. The semi-arid Pucará Valley contains eight abandoned and incised geomorphic surfaces, most of which are deformed by active structures. These geomorphic surfaces - thin alluvial fans and strath terraces - dominate the landscape and record multiple pulses of incision in the late Quaternary. We find no evidence for significant depositional intervals and valley incision continues currently. Substantial accumulations of pedogenic carbonate and pedogenic gypsum within abandoned surfaces indicate that arid or semi-arid conditions are long lived in this valley. Conversely, relict periglacial morphology in adjacent ranges supports cooler temperatures in the past. River incision is enhanced across active structures, but preliminary observations suggest that the magnitude of deformation cannot fully explain the magnitude of incision. As a result, we argue that extrabasinal base-level lowering is the primary driver of incision in the Pucará Valley, but Quaternary deformation is significant enough to spatially influence erosion. Cooler climatic intervals may influence the sedimentology of alluvial and fluvial deposits, but we find no evidence for significant climatic changes that could change rates or styles of landscape evolution over this time frame. Pending cosmogenic nuclide analysis of fan deposits and river sediments will permit the derivation of fault slip rates, surface ages, modern and paleo-erosion rates, and

Late Quaternary denudation, Death and Panamint Valleys, eastern California

USGS Publications Warehouse

Jayko, A.S.

2005-01-01

Late Quaternary denudation rates are constrained from alluvial fans and tributary watersheds in central Death and Panamint Valleys. Preliminary results suggest that the denudation rate is in part a function of the mean watershed elevation. Rainfall increases semi-logarithmically with higher elevation to about 2500 m where it becomes limited by the regional average maximum moisture content of the air mass. The fan volumes show a power-law relation to the watershed areas. The fan volumes ranged from about 250,000 to 4000 km3 and the watershed areas range from about 60,000 to 2000 km2. The upper limit of the denudation rates estimated from small Death Valley fans restricted to the east side of the basin along the Black Mountain frontal scarp range between about 0.03 to 0.18 mm/yr. The maximum is made by assuming most of the clastic accumulation in these fans followed the last highstand of Lake Manly around 24,000 yr which is the least conservative condition. The upper limit of the denudation rates from the Panamint fans range from 0.04 to 0.20 mm/yr assuming the accumulation mainly postdates OIS-4 ???60,000 yr or OIS-2 ???20,000 yr based on the presence or absence of inset shorelines from the last glacial-pluvial maximum. The greater denudation rate associated with the higher mean watershed elevations can mainly be attributed to the greater rainfall at higher elevation. Denudation rates are about a third or less of the Neogene dip-slip rates reported from nearby active faults consistent with relief increasing during dryer periods. ?? 2005 Elsevier B.V. All rights reserved.

The Evolution of Northern Hemisphere Glaciation

NASA Astrophysics Data System (ADS)

Wright, J. D.

2001-05-01

For much of the last 50 million years, high-latitude regions remained too warm to allow snow to accumulate and form ice sheets. Shackleton et al. (1984) published a landmark paper correlating the first occurrence of ice-rafted detritus (IRD) observed at Rockall Plateau with a prominent increase in benthic foraminiferal d18O values during the late Pliocene. These late Pliocene to Pleistocene ice sheets were modulated on an orbital frequency and have characterized the global climate over the past 2.6 myr (Shackleton and Opdyke, 1973; Shackleton et al., 1984; Ruddiman, et al., 1986). During the early Pliocene, northern hemisphere glaciation (NHG) variations were less significant (Jansen et al., 1993). Our understanding of the Plio-Pleistocene ice sheet cycles can be viewed from two different perspectives. When viewed from the late Pleistocene, the fundamental question is what changed near the early/late Pliocene boundary to produce the large-scale, glacial-interglacial cycles of the past 2.6 Ma. In contrast, the view from the middle to late Miocene is quite different. Since the pioneering work of Shackleton et al. (1984), the record of NHG has been extended further back in time with drilling in the Norwegian Sea (ODP Leg 104). At Sites 642 and 644, IRD was found throughout the late Miocene and back to ~12 Ma. More recent drilling in the high northern latitudes occurred on ODP Leg 151. Site 909 recovered a middle Miocene section from the Fram Straits with rounded quartz grains that were interpreted as IRD (Wolf-Welling et al., 1996). Age estimates for those sediments place the first northern hemisphere ice sheets at least as old as 14 Ma. The occurrence of sand-sized particles (>1000 μm) and coal below this level indicates the possibility of glacial activity in the Northern Hemisphere as early as 16 Ma. Thus, the late Pliocene to Pleistocene cycles appear to be the resumption of the glacial-interglacial pattern that began during the Miocene. While the Miocene ice

Late Quaternary palaeoenvironmental reconstruction of sediment drift accumulation in the Malta Graben (central Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Ferraro, Serena; Sulli, Attilio; Di Stefano, Enrico; Giaramita, Luigi; Incarbona, Alessandro; Graham Mortyn, P.; Sprovieri, Mario; Sprovieri, Rodolfo; Tonielli, Renato; Vallefuoco, Mattia; Zizzo, Elisabetta; Tranchida, Giorgio

2018-06-01

The Malta Graben is a deep tectonic depression in the Sicily Channel, bounded by NW-SE normal faults and filled by thick Pliocene-Quaternary deposits. A previous analysis of a giant piston core (LC09) from the Malta Graben had revealed a wide range of sedimentary features (carbonate turbidites, bioturbated mud and scours), although the chronostratigraphic constraint of the stacking pattern has remained elusive. After establishing a reliable chronological framework based on seven radiocarbon dates for a shorter core from the Malta Graben (ANSIC03-735), a down-core analysis of planktonic foraminifer and coccolith abundance, stable isotopes and sediment grain size was carried out. Since the last glacial maximum, palaeoenvironmental conditions (surface fertility and deep chlorophyll maximum during the last glacial and the Younger Dryas; warm and oligotrophic water masses, with a deep nutricline and intense winter mixing during the Holocene) as well as selected calcareous plankton taxa trends and peaks seem to be similar to those reported for other central and western Mediterranean sites, possibly in spite of a unique response of these areas to late Quaternary climatic fluctuations. Four distinct layers, each tens of centimetres thick, are barren of foraminifers but not of coccoliths. Morphobathymetric data as well as new high-resolution and high-penetration seismic profiles show that prolonged contouritic activity has persisted on the western side of the Malta Graben. It is thus likely that layers barren of foraminifers are due to the overflow of fine-grained (clayey) material beyond drift channel dikes.

Late Quaternary palaeoenvironmental reconstruction of sediment drift accumulation in the Malta Graben (central Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Ferraro, Serena; Sulli, Attilio; Di Stefano, Enrico; Giaramita, Luigi; Incarbona, Alessandro; Graham Mortyn, P.; Sprovieri, Mario; Sprovieri, Rodolfo; Tonielli, Renato; Vallefuoco, Mattia; Zizzo, Elisabetta; Tranchida, Giorgio

2018-03-01

The Malta Graben is a deep tectonic depression in the Sicily Channel, bounded by NW-SE normal faults and filled by thick Pliocene-Quaternary deposits. A previous analysis of a giant piston core (LC09) from the Malta Graben had revealed a wide range of sedimentary features (carbonate turbidites, bioturbated mud and scours), although the chronostratigraphic constraint of the stacking pattern has remained elusive. After establishing a reliable chronological framework based on seven radiocarbon dates for a shorter core from the Malta Graben (ANSIC03-735), a down-core analysis of planktonic foraminifer and coccolith abundance, stable isotopes and sediment grain size was carried out. Since the last glacial maximum, palaeoenvironmental conditions (surface fertility and deep chlorophyll maximum during the last glacial and the Younger Dryas; warm and oligotrophic water masses, with a deep nutricline and intense winter mixing during the Holocene) as well as selected calcareous plankton taxa trends and peaks seem to be similar to those reported for other central and western Mediterranean sites, possibly in spite of a unique response of these areas to late Quaternary climatic fluctuations. Four distinct layers, each tens of centimetres thick, are barren of foraminifers but not of coccoliths. Morphobathymetric data as well as new high-resolution and high-penetration seismic profiles show that prolonged contouritic activity has persisted on the western side of the Malta Graben. It is thus likely that layers barren of foraminifers are due to the overflow of fine-grained (clayey) material beyond drift channel dikes.

Formation of most of our coal brought Earth close to global glaciation

PubMed Central

2017-01-01

The bulk of Earth’s coal deposits used as fossil fuel today was formed from plant debris during the late Carboniferous and early Permian periods. The high burial rate of organic carbon correlates with a significant drawdown of atmospheric carbon dioxide (CO2) at that time. A recent analysis of a high-resolution record reveals large orbitally driven variations in atmospheric CO2 concentration between ∼150 and 700 ppm for the latest Carboniferous and very low values of 100 ± 80 ppm for the earliest Permian. Here, I explore the sensitivity of the climate around the Carboniferous/Permian boundary to changes in Earth’s orbital parameters and in atmospheric CO2 using a coupled climate model. The coldest orbital configurations are characterized by large axial tilt and small eccentricities of Earth’s elliptical orbit, whereas the warmest configuration occurs at minimum tilt, maximum eccentricity, and a perihelion passage during Northern hemisphere spring. Global glaciation occurs at CO2 concentrations <40 ppm, suggesting a rather narrow escape from a fully glaciated Snowball Earth state given the low levels and large fluctuations of atmospheric CO2. These findings highlight the importance of orbital cycles for the climate and carbon cycle during the late Paleozoic ice age and the climatic significance of the fossil carbon stored in Earth’s coal deposits. PMID:29073052

Formation of most of our coal brought Earth close to global glaciation.

PubMed

Feulner, Georg

2017-10-24

The bulk of Earth's coal deposits used as fossil fuel today was formed from plant debris during the late Carboniferous and early Permian periods. The high burial rate of organic carbon correlates with a significant drawdown of atmospheric carbon dioxide (CO 2 ) at that time. A recent analysis of a high-resolution record reveals large orbitally driven variations in atmospheric CO 2 concentration between [Formula: see text]150 and 700 ppm for the latest Carboniferous and very low values of 100 [Formula: see text] 80 ppm for the earliest Permian. Here, I explore the sensitivity of the climate around the Carboniferous/Permian boundary to changes in Earth's orbital parameters and in atmospheric CO 2 using a coupled climate model. The coldest orbital configurations are characterized by large axial tilt and small eccentricities of Earth's elliptical orbit, whereas the warmest configuration occurs at minimum tilt, maximum eccentricity, and a perihelion passage during Northern hemisphere spring. Global glaciation occurs at CO 2 concentrations <40 ppm, suggesting a rather narrow escape from a fully glaciated Snowball Earth state given the low levels and large fluctuations of atmospheric CO 2 These findings highlight the importance of orbital cycles for the climate and carbon cycle during the late Paleozoic ice age and the climatic significance of the fossil carbon stored in Earth's coal deposits.

A late Pleistocene long pollen record from Lake Urmia, NW Iran

NASA Astrophysics Data System (ADS)

Djamali, Morteza; de Beaulieu, Jacques-Louis; Shah-hosseini, Madjid; Andrieu-Ponel, Valérie; Ponel, Philippe; Amini, Abdolhossein; Akhani, Hossein; Leroy, Suzanne A. G.; Stevens, Lora; Lahijani, Hamid; Brewer, Simon

2008-05-01

A palynological study based on two 100-m long cores from Lake Urmia in northwestern Iran provides a vegetation record spanning 200 ka, the longest pollen record for the continental interior of the Near East. During both penultimate and last glaciations, a steppe of Artemisia and Poaceae dominated the upland vegetation with a high proportion of Chenopodiaceae in both upland and lowland saline ecosystems. While Juniperus and deciduous Quercus trees were extremely rare and restricted to some refugia, Hippophaë rhamnoides constituted an important phanerophyte, particularly during the late last glacial period. A pronounced expansion in Ephedra shrub-steppe occurred at the end of the penultimate late-glacial period but was followed by extreme aridity that favoured an Artemisia steppe. Very high lake levels, registered by both pollen and sedimentary markers, occurred during the middle of the last glaciation and late part of the penultimate glaciation. The late-glacial to early Holocene transition is represented by a succession of Hippophaë, Ephedra, Betula, Pistacia and finally Juniperus and Quercus. The last interglacial period (Eemian), slightly warmer and moister than the Holocene, was followed by two interstadial phases similar in pattern to those recorded in the marine isotope record and southern European pollen sequences.

Environmental evolution in the Picos de Europa (Cantabrian Mountains, SW Europe) since the Last Glaciation

NASA Astrophysics Data System (ADS)

Ruiz-Fernández, Jesús; Oliva, Marc; Cruces, Anabela; Lopes, Vera; Freitas, Maria da Conceição; Andrade, César; García-Hernández, Cristina; López-Sáez, José Antonio; Geraldes, Miguel

2016-04-01

The Western Massif of the Picos de Europa (latitude 43° N, longitude 4-5° W) includes some of the highest peaks in the Cantabrian Mountains. This massif was heavily glaciated during the Last Glaciation, though the post-glacial environmental evolution is still poorly understood. Using a complementary geomorphological and sedimentological approach, we have reconstructed the environmental events occurred in this massif since the last Pleistocene glaciation. The geomorphological distribution of glacial landforms suggests the occurrence of four main glacial stages: maximum glacial advance, glacial expansion after the maximum advance, Late Glacial and Little Ice Age. Moreover, a 5.4-m long sedimentary sequence was retrieved from the karstic depression of Belbín providing a continuous record of the paleoenvironmental conditions in this area since the Last Glaciation until nowadays. This section suggests that the maximum glacial expansion occurred at a minimum age of 37.2 ka cal BP, significantly prior to the global Last Glacial Maximum. Subsequently, periglacial processes prevailed in the mid lands of the massif until glaciers expanded between 22.5 and 18.7 ka cal BP. Following the melting of the glaciers, a shallow lake appeared in the Belbín depression. Lake sediments do not show evidence of a cold stage during the Late Glacial, when moraine systems formed at higher locations. The terrestrification of this lake started at 8 ka cal BP and the area turned into grassland. At 4.9 ka cal BP the existence of charcoal particles in the sediments of Belbín sequence reveals the onset of human occupation in the massif through the use of fire activity for grazing purposes. Finally, the presence of moraines inside the highest northern cirques shows evidence of the last glacial phase that occurred during the Little Ice Age cold event. Since then, the warming climate has led to the melting of these glaciers and periglacial processes prevail in the high lands of the massif.

Late Quaternary tephrostratigraphy of Baegdusan and Ulleung volcanoes using marine sediments in the Japan Sea/East Sea

NASA Astrophysics Data System (ADS)

Lim, Chungwan; Toyoda, Kazuhiro; Ikehara, Ken; Peate, David W.

2013-07-01

Only Ulleung and Baegdusan volcanoes have produced alkaline tephras in the Japan Sea/East Sea during the Quaternary. Little is known about their detailed tephrostratigraphy, except for the U-Oki and B-Tm tephras. Trace element analysis of bulk sediments can be used to identify alkaline cryptotephra because of the large compositional contrast. Five sediment cores spanning the interval between the rhyolitic AT (29.4 ka) and Aso-4 (87 ka) tephras were analyzed using an INAA scanning method. Source volcanoes for the five detected alkaline cryptotephra were identified from major element analyses of hand-picked glass shards: Ulleung (U-Ym, and the newly identified U-Sado), and Baegdusan (B-J, and the newly identified B-Sado and B-Ym). The eruption ages of the U-Ym, U-Sado, B-J, B-Sado, and B-Ym tephras are estimated to be 38 ka, 61 ka, 26 ka, 51 ka, 68-69 ka, and 86 ka, respectively, based on correlations with regional-scale TL (thinly laminated) layer stratigraphy (produced by basin-wide changes in bottom-water oxygen levels in response to millennium-scale paleoclimate variations). This study has allowed construction of an alkaline tephrostratigraphical framework for the late Quaternary linked to global environmental changes in the Japan Sea/East Sea, and improves our knowledge of the eruptive histories of Ulleung and Baegdusan volcanoes.

Proterozoic (pre-Ediacaran) glaciation and the high obliquity, low-latitude ice, strong seasonality (HOLIST) hypothesis: Principles and tests

NASA Astrophysics Data System (ADS)

Williams, George E.

2008-03-01

Sedimentological observations and palaeomagnetic data for Cryogenian glacial deposits present the climatic paradox of grounded glaciers and in situ cold climate near sea-level, glaciomarine deposition, and accompanying large (up to 40 °C) seasonal changes of temperature, all in low to near-equatorial (< 10°) palaeolatitudes (equated with geographic latitudes). Neither the "snowball Earth" nor the "slushball Earth" hypothesis can account for such strong seasonality near the palaeoequator, which together with findings from sedimentology, chemostratigraphy, biogeochemistry, micropalaeontology, geochronology and climate modelling argue against those scenarios. An alternative explanation of glaciation and strong seasonality in low palaeolatitudes is offered by a high (> 54°) obliquity of the ecliptic, which would render the equator cooler than the poles, on average, and amplify global seasonality. A high obliquity per se would not have been a primary trigger for glaciation, but would have strongly influenced the latitudinal distribution of glaciers. The principle of low-latitude glaciation on a terrestrial planet with high obliquity is validated by theoretical studies and observations of Mars. A high obliquity for the early Earth is a likely outcome of a single giant impact at 4.5 Ga, the widely favoured mechanism for lunar origin. This implies that a high obliquity could have prevailed during most of the Precambrian, controlling the low palaeolatitude of glaciations in the early and late Palaeoproterozoic and Cryogenian. It is postulated that the obliquity changed to < 54° between the termination of the last Cryogenian low-palaeolatitude glaciation at ≤ 635 Ma and the initiation of Late Ordovician-Early Silurian circum-polar glaciation at 445 Ma. The High Obliquity, Low-latitude Ice, STrong seasonality (HOLIST) hypothesis for pre-Ediacaran glaciation emerges favourably from numerous glacial and non-glacial tests. The hypothesis is in accord with such established

Constant Chinese Loess Plateau dust source since the Late Miocene

NASA Astrophysics Data System (ADS)

Bird, Anna; Millar, Ian; Stevens, Thomas; Rodenburg, Tanja; Rittner, Martin; Vermeesch, Pieter; Lu, Huayu

2017-04-01

The dramatic deepening of northern hemisphere glaciation at the Pliocene-Pleistocene boundary is accompanied by major changes in global climate. The role of the global atmospheric dust cycle in this event is not clear; in particular, whether, changes in the dust cycle influenced climates change, or resulted from it. Miocene and Quaternary wind-blown Chinese loess records past dust-cycle history, influences of aridification and monsoon circulation. Previous work on the vast Chinese Loess Plateau is in conflict over whether changes in dust source occur at the Pliocene-Pleistocene boundary (2.59 Ma), or at 1.2 Ma, despite these intervals marking major shifts in monsoon dynamics (Sun 2005; Nie et al. 2014a). Here we present Sr, Nd and Hf isotopic data from multiple sites and show that the dust source remains the same across these boundaries. The use of isotope tracers from multiple sites allows us to demonstrate that shifts in sediment geochemistry can be explained by grain-size and weathering changes. Nd and Hf isotopes show that the dust was dominantly sourced from the Tibetan Plateau, with some input from bedrock underlying the Badain Jaran/Tengger deserts. This shows that a major established and constant dust source on the northern Tibetan Plateau has been active and unchanged since the late Miocene, despite dramatically changing climate conditions. Changes in loess accumulation are therefore a function of climate change in the Tibetan Plateau source regions rather than due to expanding source areas controlled by aridification over a widening area over the Pliocene and Quaternary.

Late Quaternary eolian and alluvial response to paleoclimate, Canyonlands, southeastern Utah

USGS Publications Warehouse

Reheis, M.C.; Reynolds, R.L.; Goldstein, H.; Roberts, H.M.; Yount, J.C.; Axford, Y.; Cummings, L.S.; Shearin, N.

2005-01-01

In upland areas of Canyonlands National Park, Utah, thin deposits and paleosols show late Quaternary episodes of eolian sedimentation, pedogenesis, and climate change. Interpretation of the stratigraphy and optically stimulated luminescence ages of eolian and nearby alluvial deposits, their pollen, and intercalated paleosols yields the following history: (1) Eolian deposition at ca. 46 ka, followed by several episodes of alluviation from some time before ca. 40 ka until after 16 ka (calibrated). (2) Eolian deposition from ca. 17 ka to 12 ka, interrupted by periods of pedogenesis, coinciding with late Pleistocene alluviation as local climate became warmer and wetter. (3) A wetter period from 12 to 8.5 ka corresponding to the peak of summer monsoon influence, during which soils formed relatively quickly by infiltration of eolian silt and clay, and trees and grasses were more abundant. (4) A drier period between ca. 8.5 and 6 ka during which sheetwash deposits accumulated and more desertlike vegetation was dominant; some dunes were reactivated at ca. 8 ka. (5) Episodic eolian and fluvial deposition during a wetter, cooler period that began at ca. 6 ka and ended by ca. 3-2 ka, followed by a shift to drier modern conditions; localized mobilization of dune sand has persisted to the present. These interpretations are similar to those of studies at the Chaco dune field, New Mexico, and the Tusayan dune field, Arizona, and are consistent with paleoclimate interpretations of pollen and packrat middens in the region. A period of rapid deposition and infiltration of eolian dust derived from distant igneous source terranes occurred between ca. 12 and 8 ka. Before ca. 17 ka, and apparently back to at least 45 ka, paleosols contain little or no such infiltrated dust. After ca. 8 ka, either the supply of dust was reduced or the more arid climate inhibited translocation of dust into the soils. ?? 2005 Geological Society of America.

Technical note: Late Pliocene age control and composite depths at ODP Site 982, revisited

NASA Astrophysics Data System (ADS)

Khélifi, N.; Sarnthein, M.; Naafs, B. D. A.

2012-01-01

Ocean Drilling Program (ODP) Site 982 provided a key sediment section at Rockall Plateau for reconstructing northeast Atlantic paleoceanography and monitoring benthic δ18O stratigraphy over the late Pliocene to Quaternary onset of major Northern Hemisphere glaciation. A renewed hole-specific inspection of magnetostratigraphic reversals and the addition of epibenthic δ18O records for short Pliocene sections in holes 982A, B, and C, crossing core breaks in the δ18O record published for Hole 982B, now imply a major revision of composite core depths. After tuning to the orbitally tuned reference record LR04, the new composite δ18O record results in a hiatus, where the Kaena magnetic subchron might have been lost, and in a significant age reduction for all proxy records by 130 to 20 ky over the time span 3.2-2.7 million years ago (Ma). Our study demonstrates the general significance of reliable composite-depth scales and δ18O stratigraphies in ODP sediment records for generating ocean-wide correlations in paleoceanography. The new concept of age control makes the late Pliocene trends in SST (sea surface temperature) and atmospheric pCO2 at Site 982 more consistent with various paleoclimate trends published from elsewhere in the North Atlantic.

Late Quaternary stratigraphy of the La Janda Basin (SW Spain) - first results and palaeoenvironmental significance

NASA Astrophysics Data System (ADS)

Höbig, Nicole; Santisteban, Juan; Mediavilla, Rosa; May, Simon Matthias; Klasen, Nicole; Brückner, Helmut; van't Hoff, Jasmijn; Reicherter, Klaus

2017-04-01

The La Janda basin in southern Spain is a near-shore geo-bio-archive comprising a variable Quaternary depositional history, with shallow marine, lacustrine, palustrine, and terrestrial strata. In the 1930s the lake was drained and is serving now as a huge agricultural area. The 33 m-core recovered in fall 2016 along with several shallower drill cores up to c. 15 m, reveals insights into a unique mixed terrestrial palaeo-environmental archive in Andalucia influenced by the Atlantic Ocean and hence the North Atlantic Oscillation (NAO) within the Gulf of Cádiz. The basin's evolution was influenced both by the postglacial marine transgression and by an active tectonic fault controlling most of the accommodation space by causing subsidence. Our long core was accompanied by further corings along an E-W striking transect in order to reveal also the relation of the influence of tectonic activity with sedimentary sequences. Multi-Sensor Core Logging has been completed. Results of sedimentological, geochemical and micropalaeontological analyses will be presented in the frame of the climate variations during the Late Pleistocene and the Holocene, along with a preliminary age-depth model based on radiocarbon (AMS-14C) and optical stimulated luminescence (OSL) dating techniques. Our investigations ultimately aim at providing valuable information on major Late Pleistocene to Holocene climatic and palaeo-environmental fluctuations in the southernmost part of the Iberian Peninsula.

Sedimentology of the mid-Carboniferous fill of the Olta paleovalley, eastern Paganzo Basin, Argentina: Implications for glaciation and controls on diachronous deglaciation in western Gondwana during the late Paleozoic Ice Age

NASA Astrophysics Data System (ADS)

Moxness, Levi D.; Isbell, John L.; Pauls, Kathryn N.; Limarino, Carlos O.; Schencman, Jazmin

2018-07-01

Both global and regional climate drivers contributed to glaciation during the late Paleozoic Ice Age (LPIA). However, the transition from icehouse to greenhouse conditions was asynchronous across Gondwana suggesting that, in some cases, regional controls played a significant role in deglaciation. Of particular interest to understanding changing LPIA climatic conditions, is the eastern Paganzo Basin. This region was flanked by ice centers in the Precordilleran and Sierras Pampeanas regions of Argentina on the west, and major ice sheets in the Paraná, Chaco-Paraná, and Sauce Grande basins to the east, all of which resided between ∼40 and 65° S latitude. Hypotheses on the occurrence of ice in the eastern Paganzo Basin are based on interpretations of the narrow, steep-walled, Olta-Malanzán paleovalley as carved by an alpine glacier or by an outlet glacier draining an eastern ice sheet, and that glaciers deposited coarse clastics within the paleovalley. However, we found no evidence for glaciation. Rather, gravel from prograding alluvial fans/fan deltas and rock falls ponded drainage resulting in lacustrine activity in the eastern end of the valley. A transition from either subaerially or shallow subaqueously deposited sandstones to marine mudstones in the western end of the Olta paleovalley suggest a marine transgression, which, in turn, was overlain by deposits of prograding Gilbert-type deltas. Dropstones were from rock falls off valley walls and rafting by lake ice rather than from icebergs. Therefore, we conclude that the climate in western Argentina resulted from uplift induced glaciation in the Precordilleran region and along the western margin of the Paganzo Basin, and the occurrence of a precipitation shadow to the east. The disappearance of the western glaciers during the mid-Carboniferous, prior to deglaciation elsewhere at the same paleolatitude, resulted from a westward shift in the position of the active margin, collapse of the glaciated upland

Rivers turned to rock: Late Quaternary alluvial induration influencing the behaviour and morphology of an anabranching river in the Australian monsoon tropics

NASA Astrophysics Data System (ADS)

Nanson, Gerald C.; Jones, Brian G.; Price, David M.; Pietsch, Timothy J.

2005-09-01

Late Quaternary alluvial induration has greatly influenced contemporary channel morphology on the anabranching Gilbert River in the monsoon tropics of the Gulf of Carpentaria. The Gilbert, one of a number of rivers in this region, has contributed to an extensive system of coalescing low-gradient and partly indurated riverine plains. Extensive channel sands were deposited by enhanced flow conditions during marine oxygen isotope (OI) Stage 5. Subsequent flow declined, probably associated with increased aridity, however, enhanced runoff recurred again in OI Stages 4-3 (˜65-50 ka). Aridity then capped these plains with 4-7 m of mud. A widespread network of sandy distributary channels was incised into this muddy surface from sometime after the Last Glacial Maximum (LGM) to the mid Holocene during a fluvial episode more active than the present but less so than those of OI Stages 5 and 3. This network is still partly active but with channel avulsion and abandonment now occurring largely proximal to the main Gilbert flow path. A tropical climate and reactive catchment lithology have enhanced chemical weathering and lithification of alluvium along the river resulting in the formation of small rapids, waterfalls and inset gorges, features characteristic more of bedrock than alluvial systems. Thermoluminescence (TL) and comparative optically stimulated luminescence (OSL) ages of the sediments are presented along with U/Th ages of pedogenic calcrete and Fe/Mn oxyhydroxide/ oxide accumulations. They show that calcrete precipitated during the Late Quaternary at times similar to those that favoured ferricrete formation, possibly because of an alternating wet-dry climate. Intense chemical alteration of the alluvium leading to induration appears to have prevailed for much of the Late Quaternary but, probably due to exceptional dryness, not during the LGM. The result has been restricted channel migration and a reduced capacity for the channel to adjust and accommodate sudden

Aspects of late Quaternary geomorphological development in the Khangai Mountains and the Gobi Altai Mountains (Mongolia)

NASA Astrophysics Data System (ADS)

Lehmkuhl, Frank; Nottebaum, Veit; Hülle, Daniela

2018-07-01

The reconstruction of geomorphological processes as a result of environmental change is approached by investigating and dating some fluvial, aeolian and lacustrine archives at specific locations that form a N-S basin and range transect across the Khangai Mountains south to the eastern Gobi Altai mountains in Mongolia. Geomorphological processes varied a) spatially with different climatic conditions and vegetation cover in relation to different elevation and latitude and b) temporally due to climatic shifts during the late Quaternary. In total, 15 sections from three distinct sub-regions along that transect were dated by 22 OSL ages. The Khangai Mountain sub-region exhibits mainly late Glacial to Holocene aeolian silty to sandy cover sediments mainly in the upper catchment reaches (>1800 m a.s.l.). Sections in the northern and central Gobi represent river terraces and alluvial fans in basin areas as well as aeolian sediments in the mountains above 2200 m a.s.l. The oldest terrace surface found in this study (T2; NGa1) dates to the penultimate Glacial cycle. The T1 terrace surfaces, on the northern Khangai Mountain front and in the central Gobi sub-region yield a maximum accumulation during the global Last Glacial Maximum (gLGM) and late Glacial time. During the gLGM phase represents rather sheetflow dominated transport built the alluvial fans and in late Glacial times the sediments exhibit more debrisflow controlled accumulation. Incision, forming the T1-terrace edges is therefore, supposed for the Pleistocene-Holocene transition and subsequent early Holocene. The geomorphic evidence is interpreted as stronger fluvial morphodynamics induced by enhanced humidity under beginning interglacial conditions. These processes coincided with the development of aeolian mantles at higher altitudes in the Khangai and Gobi Altai mountains where higher temperatures and humidities supported the formation of a vegetation cover, that served as a dust trap at least since late Glacial

Impacts of late Quaternary environmental change on the long-tailed ground squirrel (Urocitellus undulatus) in Mongolia.

PubMed

McLean, Bryan S; Nyamsuren, Batsaikhan; Tchabovsky, Andrey; Cook, Joseph A

2018-03-08

Impacts of Quaternary environmental changes on mammal faunas of central Asia remain poorly understood due to a lack of geographically comprehensive phylogeographic sampling for most species. To help address this knowledge gap, we conducted the most extensive molecular analysis to date of the long-tailed ground squirrel (Urocitellus undulatus Pallas 1778) in Mongolia, a country that comprises the southern core of this species' range. Drawing on material from recent collaborative field expeditions, we genotyped 128 individuals at 2 mitochondrial genes (cytochrome b and cytochrome oxidase I; 1 797 bp total). Phylogenetic inference supports the existence of two deeply divergent infraspecific lineages (corresponding to subspecies U. u. undulatus and U. u. eversmanni), a result in agreement with previous molecular investigations but discordant with patterns of range-wide craniometric and external phenotypic variation. In the widespread western eversmanni lineage, we recovered geographically-associated clades from the: (a) Khangai, (b) Mongolian Altai, and (c) Govi Altai mountain ranges. Phylogeographic structure in U. u. eversmanni is consistent with an isolation-by-distance model; however, genetic distances are significantly lower than among subspecies, and intra-clade relationships are largely unresolved. The latter patterns, as well as the relatively higher nucleotide polymorphism of populations from the Great Lakes Depression of northwestern Mongolia, suggest a history of range shifts into these lowland areas in response to Pleistocene glaciation and environmental change, followed by upslope movements and mitochondrial lineage sorting with Holocene aridification. Our study illuminates possible historical mechanisms responsible for U. undulatus genetic structure and contributes to a framework for ongoing exploration of mammalian response to past and present climate change in central Asia.

Tidal notches, coastal landforms and relative sea-level changes during the Late Quaternary at Ustica Island (Tyrrhenian Sea, Italy)

NASA Astrophysics Data System (ADS)

Furlani, Stefano; Antonioli, Fabrizio; Cavallaro, Danilo; Chirco, Pietro; Caldareri, Francesco; Martin, Franco Foresta; Morticelli, Maurizio Gasparo; Monaco, Carmelo; Sulli, Attilio; Quarta, Gianluca; Biolchi, Sara; Sannino, Gianmaria; de Vita, Sandro; Calcagnile, Lucio; Agate, Mauro

2017-12-01

In this paper we present and discuss data concerning the morphostructural evolution at Ustica Island (Tyrrhenian Sea, Italy) during Late Quaternary. New insights on the relative sea-level changes of Ustica are coming from data collected during a geomorphological field survey around the island, together with the bathymetric analysis of the surrounding seabed and 14C datings on samples of speleothems, flowstones and marine shells found inside three selected sea caves. The survey was mainly accomplished on June 2015 through the first complete snorkel investigation off the about 18 km-long volcanic coast of the island, which allowed to precisely define location, relationship and morphometric features of coastal landforms associated with modern sea level. This study highlights the occurrence, for the first time in the Mediterranean, of tidal notches in correspondence of carbonate inclusions in volcanic rocks. The elevation of the modern tidal notch suggests that no significant vertical deformations occurred in the southeastern and eastern sectors of Ustica in the last 100 years. However, the presence of pillow lavas along the coast demonstrates that Ustica was affected by a regional uplift since the Late Quaternary, as also confirmed by MIS5.5 deposits located at about 30 m a.s.l., which suggests an average uplift rate of 0.23 mm/y. Radiocarbon dating of fossil barnacles collected inside the Grotta Segreta cave indicate an age of 1823 ± 104 cal. BP. The difference in height with respect to living barnacles in the same site suggests that their present elevation could be related to stick-slip coseismic deformations caused by the four earthquake sequences (two of which with Mw = 4.63 ± 0.46) that strongly struck the island between 1906 and 1924.

Toward a Late Quaternary tephrostratigraphic framework for East African palaeoenvironmental records

NASA Astrophysics Data System (ADS)

Lane, Christine; Martin-Jones, Catherine; Johnson, Thomas; Lamb, Henry; Pearce, Nick; Scholz, Christopher; Smith, Victoria; Verschuren, Dirk

2015-04-01

Understanding the spatial and temporal variability of climate forcing and environmental response across a continent as climatically diverse as Africa relies upon comparison of data from widespread palaeoenvironmental archives. Accurate, precise and independent chronologies for such records are essential; however this remains a challenge in many environments, often preventing the valid comparison of detailed palaeo-proxy records. Many studies have now shown that volcanic ash (tephra) can be detected in terrestrial and marine sediments thousands of kilometres from their source, often as microscopic or "cryptic" layers. As well as offering opportunities for both direct (e.g. by 40Ar/39Ar methods) and indirect (e.g. by associated 14C dates) dating of the sediment sequence, tephra layers can provide stratigraphic tie-lines between archives, facilitating precise correlations at single moments in time. Furthermore, where two or more tephra layers are co-located in multiple records, rates of change can be compared within a period of equivalent duration, even in the absence of absolute age estimates. Investigations into the presence of visible and non-visible (crypto-) tephra layers within lacustrine palaeoenvironmental records of the last ~150 ka BP from across East Africa are revealing the potential for this approach to (i) correlate palaeoclimate archives from across and beyond tropical Africa within a regional tephrostratigraphic framework; (ii) provide age constraints for individual core chronologies, in particular beyond the limits of radiocarbon dating; and (iii) increase our knowledge of the history of Late Quaternary explosive volcanism in East Africa.

Holocene glaciation of the central Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Bowerman, Nicole D.; Clark, Douglas H.

2011-05-01

Sediment cores from two bedrock-dammed lakes in North Fork Big Pine Creek, Sierra Nevada, California, preserve the most detailed and complete record of Holocene glaciation yet recovered in the region. The lakes are fed by outwash from the Palisade Glacier, the largest (˜1.3 km 2) and presumably longest-lived glacier in the range, and capture essentially all of the rock flour it produces. Distinct late-Holocene (Matthes) and late-Pleistocene (Recess Peak) moraines lie between the modern glacier and the lakes. The lakes have therefore received continuous sedimentation from the basin since the retreat of the Tioga glacier (Last Glacial Maximum) and capture rock flour related to all post-LGM advances. A total of eight long cores (up to 5.5 m sediment depth) and one short surface sediment short core preserve a coherent record of fluctuating rock flour flux to the lakes through the Holocene. Age constraints on rock flour spikes in First and Second lakes based on 31 14C-dated macrofossils indicate Holocene glaciation began ˜3200 cal yr B P, followed by a possible glacier maximum at ˜2800 cal yr B P and four distinct glacier maxima at ˜2200, ˜1600, ˜700 and ˜250-170 cal yr. B.P., the most recent maximum being the largest. Reconstruction of the equilibrium-line altitudes (ELA) associated with each distinct advance recorded in the moraines (Recess Peak, Matthes, and modern) indicates ELA depressions (relative to modern) of ˜250 m and 90 m for Recess Peak and Matthes advances, respectively. These differences represent decreases in summer temperatures of 1.7-2.8 °C (Recess Peak) and 0.2-2° (Matthes), and increases in winter precipitation of 22-34 cm snow water equivalent (s.w.e.) (Recess Peak) and 3-26 cm s.w.e. (Matthes) compared to modern conditions. Although small, these changes are significant and similar to those noted in the Cascade Range to the north, and represent a significant departure from historical climate trends in the region.

Seismic stratigraphy and depositional history of late Quaternary deposits at the eastern Yellow Sea shelf

NASA Astrophysics Data System (ADS)

Yoo, Dong-Geun; Lee, Gwang-Soo; Kim, Gil-Young; Chang, Se-Won; Kim, Kyoung-Jin

2017-04-01

The late Quaternary stratigraphy and sedimentation at the eastern Yellow Sea shelf was studied using a dense network of high-resolution, single-channel seismic reflection profiles and sediment data. The shelf sequence in this area consists of six seismic units formed since the LGM. During the LGM, the study area was completely exposed, resulting in subaerial erosion associated with paleo-channel incision by the Huanghe and Korean Rivers. As the shelf was flooded, the incised channels were backfilled fluvial or coastal sediments, forming incised channel-fill deposits (SU1). The paleo-river may have supplied abundant terrigenous sediments to the study area around the paleo-river mouth and adjacent area. These sediments were trapped within the paleo-estuary and formed SU2, regarded as an estuarine deposit. Two types of serial sand ridges (SU3 and SU5) which correspond to transgressive deposits developed. SU3 on the southern part, west of Jeju Island (80 110 m deep) is regarded as a moribund-type mainly formed during the early to middle stage of transgression. These are thought to have ceased growing and remobilizing. In contrast, SU5 (occurring 30 50 m deep off the Korean Peninsula) is generally regarded as active sand ridges deposited during the late stage of transgression and is partly modified by modern tidal currents. As the transgression continued, the near-surface sediments were reworked and redistributed by shelf erosion, resulting in a thin veneer of transgressive sands (SU4). The uppermost unit (SU6) formed the Heuksan Mud Belt (HMB), which is one of the most prominent mud deposits in the Yellow Sea. The lower part of the HMD corresponds to shelf-mud deposited during the late stage of transgression, whereas the upper part consists of a recent shelf-delta developed after the highstand sea level at about 7 ka BP.

Modeling global vegetation in the late Quaternary: What progress have we made and what are the priorities for the future?

NASA Astrophysics Data System (ADS)

Kaplan, Jed

2017-04-01

More than two decades ago, the development of the first global biogeography models led to an interest in simulating global land cover in the past. These models promised the possibility of creating a coherent picture of the Earth's vegetation that went beyond qualitative extrapolation of site-based observations, e.g., from paleoecological archives, and was not limited to areas with a high density of sites. Then as now, the goal of much work simulating past vegetation was to explore and understand the role of biogeophysical and biogeochemical feedbacks between the Earth's land surface and the climate system. Paleovegetation modeling for the late Quaternary has also influenced debates on the character of natural vegetation, conservation and ecological restoration goals, and the co-evolution of humans, civilizations, and the landscapes in which they live. The first simulations of global land cover in the past used equilibrium vegetation models, e.g., BIOME1, BIOME3, and BIOME4, and focused on well-known timeslices of interest in paleoclimate research, including the Last Glacial Maximum (21,000 BP) and the mid-Holocene (6,000 BP). Questions addressed included: quantification of the importance of terrestrial vegetation in the glacial carbon cycle, the role of changing vegetation cover on glacial inception, and the influence of biogeophysical feedbacks on the amplitude and spatial pattern of the mid-Holocene African Monsoon. In the intervening years, as both vegetation and climate models evolved and improved, the spatial resolution, number of periods studied, and the type of research questions addressed expanded greatly. Studies covered the dynamics of Arctic vegetation, wetland area, wetland methane emissions, and paleo-atmospheric chemistry, dust emissions and effects on paleoclimate, among others. A major recent advance in paleovegetation modeling for the late Quaternary has come with the development of Dynamic Global Vegetation Models (DGVMs) that are capable of

Comparative Earth history and Late Permian mass extinction

NASA Technical Reports Server (NTRS)

Knoll, A. H.; Bambach, R. K.; Canfield, D. E.; Grotzinger, J. P.

1996-01-01

The repeated association during the late Neoproterozoic Era of large carbon-isotopic excursions, continental glaciation, and stratigraphically anomalous carbonate precipitation provides a framework for interpreting the reprise of these conditions on the Late Permian Earth. A paleoceanographic model that was developed to explain these stratigraphically linked phenomena suggests that the overturn of anoxic deep oceans during the Late Permian introduced high concentrations of carbon dioxide into surficial environments. The predicted physiological and climatic consequences for marine and terrestrial organisms are in good accord with the observed timing and selectivity of Late Permian mass extinction.

Tephra compositions from Late Quaternary volcanoes around the Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Kraus, S.

2009-12-01

/Hf ratios lower than N-MORB, all other volcanoes including the Larsen Rift centers display Zr/Hf higher than N-MORB. It is expected that the correlation of the new data with published data from tephra layers found in ice, lake and marine sediment cores will contribute to a better constrained timing of individual climatic events identified in the northern Antarctic Peninsula area. Late Quaternary volcanoes around the northern Antarctic Peninsula.

The enigma of the Australian Alps, young landscapes and missing cryogenic features.

NASA Astrophysics Data System (ADS)

Slee, Adrian; Shulmeister, James; Clark, Doug

2014-05-01

Widespread evidence for pre last glacial cycle glaciation of late Quaternary ages has been documented from mid-latitude southern hemisphere mountain environments in New Zealand, southern South America and the Tasmanian Highlands. On mainland Australia however cirque and small valley glaciation in the Australian Alps is limited to OIS 4-3 and the last glacial maximum (OIS 2) (Barrows et al. 2001). This contrasts with the other southern hemisphere glacial records that indicate significantly more extensive glaciations preceding the last glacial cycle. In both the Southern Andes and Tasmania the maximum glaciations occurred prior to 783 kya (Glasser et al. 2008, Colhoun et al. 2010) while in tectonically active New Zealand it is at least clear that the scale of glaciation has been diminishing over the last 3 glacial cycles (Shulmeister et al. 2010). In all these locations early workers argued for extensive ice coverage, but subsequent investigations limited the extent and number of glacial advances before more recent work has locally re-extended the glacial limits and greatly increased the number of glacial advances. Similarly, in the highlands of SE Australia the possibility of more pervasive ice coverage was initially entertained; but since the 1960s and especially the 1980s the general consensus is that the lack of glacial evidence is a result of cold dry conditions prevailing for much of the Quaternary on the Australian Alps (Reeves et al. 2013) Recent work by the authors on the extent of relict periglacial block deposits in Australia have identified these block deposits as far north as 29°30'S on the Great Dividing Range, confirming strong freeze-thaw conditions well into the sub-tropics at moderate (900-1200 m) elevations. Curiously, however, the same mapping work has also highlighted the limited development of block deposits and other freeze-thaw landforms, such as tors, in the highest regions of the Australian Alps, in areas beyond the known limits of

Quaternary deposits and landscape evolution of the central Blue Ridge of Virginia

USGS Publications Warehouse

Eaton, L. Scott; Morgan, Benjamin A.; Kochel, R. Craig; Howard, Alan D.

2003-01-01

A catastrophic storm that struck the central Virginia Blue Ridge Mountains in June 1995 delivered over 775 mm (30.5 in) of rain in 16 h. The deluge triggered more than 1000 slope failures; and stream channels and debris fans were deeply incised, exposing the stratigraphy of earlier mass movement and fluvial deposits. The synthesis of data obtained from detailed pollen studies and 39 radiometrically dated surficial deposits in the Rapidan basin gives new insights into Quaternary climatic change and landscape evolution of the central Blue Ridge Mountains.The oldest depositional landforms in the study area are fluvial terraces. Their deposits have weathering characteristics similar to both early Pleistocene and late Tertiary terrace surfaces located near the Fall Zone of Virginia. Terraces of similar ages are also present in nearby basins and suggest regional incision of streams in the area since early Pleistocene–late Tertiary time. The oldest debris-flow deposits in the study area are much older than Wisconsinan glaciation as indicated by 2.5YR colors, thick argillic horizons, and fully disintegrated granitic cobbles. Radiocarbon dating indicates that debris flow activity since 25,000 YBP has recurred, on average, at least every 2500 years. The presence of stratified slope deposits, emplaced from 27,410 through 15,800 YBP, indicates hillslope stripping and reduced vegetation cover on upland slopes during the Wisconsinan glacial maximum.Regolith generated from mechanical weathering during the Pleistocene collected in low-order stream channels and was episodically delivered to the valley floor by debris flows. Debris fans prograded onto flood plains during the late Pleistocene but have been incised by Holocene stream entrenchment. The fan incision allows Holocene debris flows to largely bypass many of the higher elevation debris fan surfaces and deposit onto the topographically lower surfaces. These episodic, high-magnitude storm events are responsible for

The low-latitude Rapitan glaciation (Invited)

NASA Astrophysics Data System (ADS)

MacDonald, F. A.; Schmitz, M. D.; Crowley, J. L.; Roots, C.; Maloof, A. C.; Jones, D. S.; Strauss, J.

2009-12-01

The snowball Earth hypothesis1 was developed in response to strong palaeomagnetic evidence for low-latitude glaciation from “Marinoan” glacial deposits in the Elatina Formation of Australia. An earlier Cryogenian glaciation, commonly referred to as the “Sturtian” glaciation, has been inferred from the ubiquity of pre-Marinoan glacial deposits; however, the synchroneity and global extent of this event have been questioned due to the lack of precise U/Pb ages and robust paleomagnetic data. Herein we provide new age constraints on the Franklin LIP with revised U/Pb ID-TIMS dates on the the Mt. Harper volcanic complex in the Yukon Territory and the Coronation sills of Victoria Island. Furthermore we present a new age from a tuff interbedded with diamictite in the Upper Mt. Harper Group. A glaciogenic origin of the diamictites is provided by striated clasts and laminae-penetrating dropstones. These glacial deposits can be traced from Alaska westward through the Yukon Territory and into the Northwest Territories, and are correlative to the Rapitan Group. Throughout the Cordillera, the Rapitan Group and its correlatives commonly host iron formation, are the lower of two Cryogenian glacial horizons, and globally are thought to be equivalent to the Sturtian glaciation. The age of the tuff interbedded with the glacial deposits in the Mt. Harper Group is within 1 million years of the revised age on the Franklin LIP. Several paleomagnetic studies on dikes, sills, and basalts spanning >2000 km of NW Canada have agreed that the Franklin LIP erupted when NW Laurentia was in an equatorial position2,3. Consequently, the Sturtian glaciation on Laurentia can now be confidently inferred to have occurred at a very low palaeolatitude. Thus, there were at least two Cryogenian glaciations of global extent. 1 Kirschvink, J.L., in The Proterozoic Biosphere, edited by J. W. Schopf and C. Klein (Cambridge University Press, Cambridge, 1992), pp. 51. 2 Park, J.K., Paleomagnetic

A fractal analysis of quaternary, Cenozoic-Mesozoic, and Late Pennsylvanian sea level changes

NASA Technical Reports Server (NTRS)

Hsui, Albert T.; Rust, Kelly A.; Klein, George D.

1993-01-01

Sea level changes are related to both climatic variations and tectonic movements. The fractal dimensions of several sea level curves were compared to a modern climatic fractal dimension of 1.26 established for annual precipitation records. A similar fractal dimension (1.22) based on delta(O-18/O-16) in deep-sea sediments has been suggested to characterize climatic change during the past 2 m.y. Our analysis indicates that sea level changes over the past 150,000 to 250,000 years also exhibit comparable fractal dimensions. Sea level changes for periods longer than about 30 m.y. are found to produce fractal dimensions closer to unity and Missourian (Late Pennsylvanian) sea level changes yield a fractal dimension of 1.41. The fact that these sea level curves all possess fractal dimensions less than 1.5 indicates that sea level changes exhibit nonperiodic, long-run persistence. The different fractal dimensions calculated for the various time periods could be the result of a characteristic overprinting of the sediment recored by prevailing processes during deposition. For example, during the Quaternary, glacio-eustatic sea level changes correlate well with the present climatic signature. During the Missourian, however, mechanisms such as plate reorganization may have dominated, resulting in a significantly different fractal dimension.

Late quaternary lake level changes of Taro Co and neighbouring lakes, southwestern Tibetan Plateau, based on OSL dating and ostracod analysis

NASA Astrophysics Data System (ADS)

Alivernini, Mauro; Lai, Zhongping; Frenzel, Peter; Fürstenberg, Sascha; Wang, Junbo; Guo, Yun; Peng, Ping; Haberzettl, Torsten; Börner, Nicole; Mischke, Steffen

2018-07-01

The Late Quaternary lake history of Taro Co and three neighbouring lakes was investigated to reconstruct local hydrological conditions and the regional moisture availability. Ostracod-based water depth and habitat reconstructions combined with OSL and radiocarbon dating are performed to better understand the Taro Co lake system evolution during the Late Quaternary. A high-stand is observed at 36.1 ka before present which represents the highest lake level since then related to a wet stage and resulting in a merging of Taro Co and its neighbouring lakes Zabuye and Lagkor Co this time. The lake level then decreased and reached its minimum around 30 ka. After c. 20 ka, the lake rose above the present day level. A minor low-stand, with colder and drier conditions, is documented at 12.5 cal. ka BP. Taro Co Zabuye and Lagkor Co formed one large lake with a corresponding high-stand during the early Holocene (11.2-9.7 cal. ka BP). After this Holocene lake level maximum, all three lakes shrank, probably related to drier conditions, and Lagkor Co became separated from the Taro Co-Zabuye system at c.7 ka. Subsequently, the lake levels decreased further about 30 m and Taro Co began to separate from Zabuye Lake at around 3.5 ka. The accelerating lake-level decrease of Taro Co was interrupted by a short-term lake level rise after 2 ka BP, probably related to minor variations of the monsoonal components. A last minor high-stand occurred at about 0.8 ka before today and subsequently the lake level of Taro Co registers a slight increase in recent years.

Two late quaternary pollen records from the upper Kolyma region, Soviet Northeast: A preliminary report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, P.M.; Brubaker, L.; Andreev, A.A.

Pollen records from Sosednee and Elikchan Lakes provide the first continuous late Quaternary vegetation history for the upper Kolyma drainage of the Soviet Northeast. Full-glacial spectra at these sites are similar to those from Eastern Beringia, with high percentages of grass, sedge, and wormwood pollen indicative of herb tundra. In the Elikchan area at approximately 12,500 B.P., herb tundra was replaced by a stone pine-larch forest, perhaps similar to forests in the modern region. In contrast, the herb tundra near Sosednee Lake was succeeded by a birch-alder shrub tundra followed by a larch woodland. Stone pine increased in the regionmore » after larch and prior to 8600 B.P. A Holocene decline in stone pine, which is evident at Elikchan Lake, is less marked or absent at Sosednee Lake. The differences in these pollen records is somewhat surprising given the proximity of the two sites. Such differences indicate that numerous well-dated sites will be needed to describe the vegetation and climate histories of Western Beringia.« less

Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean

USGS Publications Warehouse

Polyak, L.; Bischof, J.; Ortiz, J.D.; Darby, D.A.; Channell, J.E.T.; Xuan, C.; Kaufman, D.S.; Lovlie, R.; Schneider, D.A.; Eberl, D.D.; Adler, R.E.; Council, E.A.

2009-01-01

Sediment cores from the western Arctic Ocean obtained on the 2005 HOTRAX and some earlier expeditions have been analyzed to develop a stratigraphic correlation from the Alaskan Chukchi margin to the Northwind and Mendeleev-Alpha ridges. The correlation was primarily based on terrigenous sediment composition that is not affected by diagenetic processes as strongly as the biogenic component, and paleomagnetic inclination records. Chronostratigraphic control was provided by 14C dating and amino-acid racemization ages, as well as correlation to earlier established Arctic Ocean stratigraphies. Distribution of sedimentary units across the western Arctic indicates that sedimentation rates decrease from tens of centimeters per kyr on the Alaskan margin to a few centimeters on the southern ends of Northwind and Mendeleev ridges and just a few millimeters on the ridges in the interior of the Amerasia basin. This sedimentation pattern suggests that Late Quaternary sediment transport and deposition, except for turbidites at the basin bottom, were generally controlled by ice concentration (and thus melt-out rate) and transportation distance from sources, with local variances related to subsurface currents. In the long term, most sediment was probably delivered to the core sites by icebergs during glacial periods, with a significant contribution from sea ice. During glacial maxima very fine-grained sediment was deposited with sedimentation rates greatly reduced away from the margins to a hiatus of several kyr duration as shown for the Last Glacial Maximum. This sedimentary environment was possibly related to a very solid ice cover and reduced melt-out over a large part of the western Arctic Ocean.

Ecosystem resilience to abrupt late Quaternary change in continental southern Siberia

NASA Astrophysics Data System (ADS)

Harding, Poppy; Mackay, Anson; Bezrukova, Elena; Shchetnikov, Alexander

2017-04-01

Quaternary climate variability is dominated by long term orbital forcing along with abrupt sub-Milankovitch events on the scales of millennia to centuries, driven by internal feedback mechanisms, volcanic forcing and fluctuating solar activity. Although these are well documented in the North Atlantic region, their expression is poorly understood in Siberia, particularly in relation to abrupt climatic events. Siberia has the world's highest level of continentality offering an opportunity to study changes remote from oceanic influences and improving understanding of interactions between the Siberian High and other atmospheric systems including the Aleutian Low, Arctic oscillation and Icelandic Low1 and ENSO2. Understanding of palaeoenvironmental change in Siberia is essential due to the region's high sensitivity to climatic change, with warming rates considerably higher than the global average over the past 50 years3, triggering significant environmental changes, including permafrost degradation, shifts in the forest-steppe biome, increases in forest fires and warming of seasonally ice-covered lakes. Additionally, the region provides essential palaeoenvironmental context for early hominins, for example at globally important sites such as Denisova cave4, and megafauna extinctions5. This presentation outlines ongoing work at Lake Baunt, SE Siberia including: key quaternary climate forcings, the site and its regional context, the key methods and preliminary results. These include a dated record back to ˜30ka BP (based on multiple 14C dates and Bayesian age modelling), multiproxy indicators of palaeoproductivity (e.g. biogenic silica and diatom analyses) and lake mixing regimes (inferred from diatom analyses). Together these highlight several key Quaternary fluctuations potentially correlated to events recorded in Greenland Ice Cores (GS2, GS2.1, GI1, GS1), and these are considered against key Quaternary records including those from nearby Lake Baikal and Hulu Cave in

Aragonite preservation in late Quaternary sediment cores on the Brazilian Continental Slope: implications for intermediate water circulation

NASA Astrophysics Data System (ADS)

Gerhardt, S.; Groth, H.; Rühlemann, C.; Henrich, R.

We present late Quaternary records of aragonite preservation determined for sediment cores recovered on the Brazilian Continental Slope (1790-2585m water depth) where North Atlantic Deep Water (NADW) dominates at present. We have used various indirect dissolution proxies (carbonate content, aragonite/calcite contents, and sand percentages) as well as gastropodal abundances and fragmentation of Limacina inflata to determine the state of aragonite preservation. In addition, microscopic investigations of the dissolution susceptibility of three Limacina species yielded the Limacina Dissolution Index which correlates well with most of the other proxies. Excellent preservation of aragonite was found in the Holocene section, whereas aragonite dissolution gradually increases downcore. This general pattern is attributed to an overall increase in aragonite corrosiveness of pore waters. Overprinted on this early diagenetic trend are high-frequency fluctuations of aragonite preservation, which may be related to climatically induced variations of intermediate water masses.

Wet-based glaciation in Phlegra Montes, Mars.

NASA Astrophysics Data System (ADS)

Gallagher, Colman; Balme, Matt

2016-04-01

Eskers are sinuous landforms composed of sediments deposited from meltwaters in ice-contact glacial conduits. This presentation describes the first definitive identification of eskers on Mars still physically linked with their parent system (1), a Late Amazonian-age glacier (~150 Ma) in Phlegra Montes. Previously described Amazonian-age glaciers on Mars are generally considered to have been dry based, having moved by creep in the absence of subglacial water required for sliding, but our observations indicate significant sub-glacial meltwater routing. The confinement of the Phlegra Montes glacial system to a regionally extensive graben is evidence that the esker formed due to sub-glacial melting in response to an elevated, but spatially restricted, geothermal heat flux rather than climate-induced warming. Now, however, new observations reveal the presence of many assemblages of glacial abrasion forms and associated channels that could be evidence of more widespread wet-based glaciation in Phlegra Montes, including the collapse of several distinct ice domes. This landform assemblage has not been described in other glaciated, mid-latitude regions of the martian northern hemisphere. Moreover, Phlegra Montes are flanked by lowlands displaying evidence of extensive volcanism, including contact between plains lava and piedmont glacial ice. These observations provide a rationale for investigating non-climatic forcing of glacial melting and associated landscape development on Mars, and can build on insights from Earth into the importance of geothermally-induced destabilisation of glaciers as a key amplifier of climate change. (1) Gallagher, C. and Balme, M. (2015). Eskers in a complete, wet-based glacial system in the Phlegra Montes region, Mars, Earth and Planetary Science Letters, 431, 96-109.

A New Chronology of Late Quaternary Sequences From the Central Arctic Ocean Based on "Extinction Ages" of Their Excesses in 231Pa and 230Th

NASA Astrophysics Data System (ADS)

Hillaire-Marcel, C.; Ghaleb, B.; de Vernal, A.; Maccali, J.; Cuny, K.; Jacobel, A.; Le Duc, C.; McManus, J.

2017-12-01

Merging the late Quaternary Arctic paleoceanography into the Earth's global climate history remains challenging due to the lack of robust marine chronostratigraphies. Over ridges notably, low and variable sedimentation rates, scarce biogenic remains ensuing from low productivity and/or poor preservation, and oxygen isotope and paleomagnetic records differing from global stacks represent major impediments. However, as illustrate here based on consistent records from Mendeleev-Alpha and Lomonosov Ridges, disequilibria between U-series isotopes can provide benchmark ages. In such settings, fluxes of the particle-reactive U-daughter isotopes 230Th and 231Pa from the water column, are not unequivocally linked to sedimentation rates, but rather to sea-ice rafting and brine production histories, thus to the development of sea-ice factories over shelves during intervals of high relative sea level. The excesses in 230Th and 231Pa over fractions supported by their parent U-isotopes, collapse down sedimentary sequences, due to radioactive decay, and provide radiometric benchmark ages of approximately 300 and 140 ka, respectively. These "extinction ages" point to mean sedimentation rates of ˜4.3 and ˜1.7 mm/ka, respectively, over the Lomonosov and Mendeleev Ridges, which are significantly lower than assumed in most recent studies, thus highlighting the need for revisiting current interpretations of Arctic lithostratigraphies in relation to the global-scale late Quaternary climatostratigraphy.

Reconstructing the groundwater flow in the Baltic Basin during the Last glaciation

NASA Astrophysics Data System (ADS)

Saks, T.; Sennikovs, J.; Timuhins, A.; Kalvāns, A.

2012-04-01

In last decades it has been discussed that most large ice sheets tend to reside on warm beds even in harsh clima tic conditions and subglacial melting occurs due to geothermal heat flow and deformation heat of the ice flow. However the subglacial groundwater recharge and flow conditions have been addressed in only few studies. The aim of this study is to establish the groundwater flow pattern in the Baltic Basin below the Scandinavian ice sheet during the Late Weichselian glaciation. The calculation results are compared to the known distribution of the groundwater body of the glacial origin found in Cambrian - Vendian (Cm-V) aquifer in the Northern Estonia which is believed to have originated as a result of subglacial meltwater infiltration during the reoccurring glaciations. Steady state regional groundwater flow model of the Baltic Basin was used to simulate the groundwater flow beneath the ice sheet with its geometry adjusted to reflect the subglacial topography. Ice thickness modelling data (Argus&Peltier, 2010) was used for the setup of the boundary conditions: the meltwater pressure at the ice bed was assumed equal to the overlying ice mass. The modelling results suggest two main recharge areas of the Cm-V aquifer system, and reversed groundwater flow that persisted for at least 14 thousand years. Model results show that the groundwater flow velocities in the Cm-V aquifer in the recharge area in N-Estonia beneath the ice sheet exceeded the present velocities by a factor of 10 on average. The calculated meltwater volume recharged into the Cm-V aquifer system during the Late Weichselian corresponds roughly to the estimated, however, considering the fact, that the study area has been glaciated at least 4 times this is an overestimation. The modeling results attest the hypothesis of light dO18 groundwater glacial origin in the Cm-V aquifer system, however the volumes, timing and processes involved in the meltwater intrusion are yet to be explored. This study was

Late Pleistocene-Holocene paleoclimate in southwestern Brazilian Amazonia with basis on floristic changes interpreted from isotope data

NASA Astrophysics Data System (ADS)

Rossetti, D. F.; Cohen, M. C. L.; Pessenda, L. C. R.

2015-12-01

Previous late Quaternary paleoclimatic interpretations in Amazonia have considered fluctuating dry to wet episodes with changes from savanna to forest, a view that concurs with other proposals of undisturbed rainforest despite global oscillations. Most of this debate is based on pollen data, but such elements are scarce in Amazonian sedimentary records. This work interprets vegetation in the Late Pleistocene and Holocene in a southwestern Amazonia lowland using δ13C, δ15N, C/N integrated with geomorphology, sedimentology and radiocarbon dating. The goal was to reconstruct vegetation changes through time and analyze their relation to climate and sedimentary dynamics. Fluvial channel and floodplain deposits with phytoplankton, as well as C3 and C4 land plants, were recorded. Between 42,033-43,168 cal yr BP and 34,804-35,584 cal yr BP, C4 land plants increased as a result of a climate drier than todaýs. However, wet climate prevailed from this time-frame until the onset of the Last Glaciation Maximum. In the Pleistocene/Holocene transition, there was an increased contribution of C4 land plants potentially related to dry episodes. However, the increased contribution of this type of land plant is not synchronous with Holocene dry episodes previously documented for the Amazonian lowland. On the other hand, it is remarkable that the record of this plant type was verified only in sites with modern grassland confined to fluvial paleo-landforms. Thus, rather than due to a dry climatic episode, the recorded grassland expansion and its maintenance up to the present time in the studied sites is more likely associated with the evolution of depositional environments, being coincidental with the progressive abandonment of fluvial systems. An important conclusion derived from the present work is that great care must be placed when reconstructing late Quaternary paleoclimate in Amazonia based on changes in floristic patterns, as they may be also a response to sedimentary dynamics.

Geomorphological and sedimentological evidences in the Western Massif of Picos de Europa since the Last Glaciation

NASA Astrophysics Data System (ADS)

Ruiz-Fernández, Jesus; Oliva, Marc; Cruces, Anabela; Lopes, Vera; Conceição Freitas, Maria; García-Hernández, Cristina; Nieuwendam, Alexandre; López-Sáez, José Antonio; Gallinar, David; Geraldes, Miguel

2015-04-01

The Western Massif of Picos de Europa includes some of the highest peaks of the Cantabrian Mountains. However, the environmental evolution in this massif since the Last Glaciation is still poorly understood. This research provides a new geochronological approach to the sequence of environmental events occurred here since the maximum expansion of glaciers during the last Pleistocene glaciation. The distribution of the glacial landforms suggests four main stages regarding the environmental evolution in the massif: maximum glacial advance, phase of second maximum glacial expansion, Late Glacial and Little Ice Age. A 5.4-m long sedimentological section retrieved from the kame terrace of Belbín, in a mid-height area of the massif, complements the geomorphological interpretation and provides a continuous paleoenvironmental sequence from this area since the Last Glaciation until nowadays. This section suggests that the maximum glacial expansion occurred at a minimum age of 37.2 ka cal BP, significantly prior to the global Last Glacial Maximum. Subsequently, a new glacial expansion occurred around 18.7-22.5 ka cal BP. The melting of the glaciers after this phase generated a shallow lake in the Belbín depression. Lake sediments do not reveal the occurrence of a cold stage during the Late Glacial, whilst, at higher locations, moraine complexes were formed suggesting a glacier readvance. The terrestrification of this lake started at 8 ka cal BP, when Belbín changed to a peaty environment. At 5 ka cal BP human occupation started at the high lands of the massif according to the existence of charcoal particles in the section. The presence of moraines in the highest northern cirques evidences the last phase with formation of small glaciers in the Western Massif of Picos de Europa, corresponding to the Little Ice Age cold event. Since then, the warming climate has led to the melting of these glaciers.

Salt lake Laguna de Fuente de Piedra (S-Spain) as Late Quaternary palaeoenvironmental archive

NASA Astrophysics Data System (ADS)

Höbig, Nicole; Melles, Martin; Reicherter, Klaus

2014-05-01

This study deals with Late Quaternary palaeoenvironmental variability in Iberia reconstructed from terrestrial archives. In southern Iberia, endorheic basins of the Betic Cordilleras are relatively common and contain salt or fresh-water lakes due to subsurface dissolution of Triassic evaporites. Such precipitation or ground-water fed lakes (called Lagunas in Spanish) are vulnerable to changes in hydrology, climate or anthropogenic modifications. The largest Spanish salt lake, Laguna de Fuente de Piedra (Antequera region, S-Spain), has been investigated and serves as a palaeoenvironmental archive for the Late Pleistocene to Holocene time interval. Several sediment cores taken during drilling campaigns in 2012 and 2013 have revealed sedimentary sequences (up to 14 m length) along the shoreline. A multi-proxy study, including sedimentology, geochemistry and physical properties (magnetic susceptibility) has been performed on the cores. The sedimentary history is highly variable: several decimetre thick silty variegated clay deposits, laminated evaporites, and even few-centimetre thick massive gypsum crystals (i.e., selenites). XRF analysis was focussed on valuable palaeoclimatic proxies (e.g., S, Zr, Ti, and element ratios) to identify the composition and provenance of the sediments and to delineate palaeoenvironmental conditions. First age control has been realized by AMS-radiocarbon dating. The records start with approximately 2-3 m Holocene deposits and reach back to the middle of MIS 3 (GS-3). The sequences contain changes in sedimentation rates as well as colour changes, which can be summarized as brownish-beige deposits at the top and more greenish-grey deposits below as well as highly variegated lamination and selenites below ca. 6 m depth. The Younger Dryas, Bølling/Allerød, and the so-called Mystery Interval/Last Glacial Maximum have presumably been identified in the sediment cores and aligned to other climate records. In general, the cores of the Laguna de

Long-Term Changes In The Behaviour Of Jakobshavns Isbrae, West Greenland During The Late Quaternary-Holocene

NASA Astrophysics Data System (ADS)

O'Cofaigh, C.; Jennings, A.; Moros, M.; Andrews, J. T.; Kilfeather, A.; Dowdeswell, J. A.; Richter, T.

2008-12-01

This poster shows the initial results of a joint scientific project to reconstruct the Late Quaternary-Holocene behavior of Jakobshavns Isbrae in central west Greenland, one of the largest ice streams draining the modern Greenland Ice Sheet. The underlying rationale for this research is to determine if recent observed changes to the mass balance of the Greenland Ice Sheet are part of the natural variability in ice-sheet dynamics, or if they relate to anthropogenically-induced climate warming. Key to resolving this question is an understanding of long-term changes in ice sheet behavior during the Late Quaternary and the Holocene. This research will allow assessment of the links between deglaciation and internal and external environmental controls, such as the influence of inflowing Atlantic Water, and will facilitate modelling of the likely future behavior of the GIS. Currently, four marine sediment cores arrayed along a transect from the Disko Bugt Fan to Disko Bay are providing information on changes in sediment flux and sedimentation style, such as abrupt intervals of iceberg-rafting vs. "normal" hemipelagic sedimentation, as well as the paleoceanographic setting and ice sheet-ocean interactions. The cores are being analysed using a variety of proxies including IRD, mineralogy, oxygen isotopes, foraminiferal assemblages, lithofacies analysis and AMS radiocarbon dating. Data are presented from two piston cores from the continental slope at the trough-mouth fan collected during the HE0006 'shakedown' cruise to Baffin Bay and from two gravity cores recovered in 2007 during MS Merian cruise MSM 05/03 to West Greenland. Slope cores contain sequences of laminated facies interpreted as fine-grained turbidites and intervals of massive, bioturbated, hemipelagic mud. The two Merian cores, contributed to this project by the Baltic Sea Research Institute, were collected from the southern entrance to Disko Bugt and the Vaigat channel north of Disko. Radiocarbon dates from the

Patterns and processes of Late Quaternary environmental change in a montane region of southwestern Europe

NASA Astrophysics Data System (ADS)

Carrión, José S.

2002-10-01

This paper examines the Late Quaternary (c. 20,300-<505 cal yr BP) environmental history of Siles, a lake situated at 1320 m in the Segura mountains of southern Spain, with the goal of establishing the mechanisms exerting control on vegetation change. Palaeoecological indicators include pollen, microcharcoal, spores of terrestrial plants, fungi, and non-siliceous algae, and other microfossils. The Siles sequence is shown to be sensitive to climatic change, although the control exerted by climate on vegetation is ultimately shaped by disturbances and species interactions, determining the occurrence of century-scale lags and threshold responses. Biotically induced changes of vegetation are also shown at the intrazonal level of variation. The new sequence is placed in the context of two previous records to postulate a picture of Holocene environmental change for the Segura region. The existence of mid-elevation glacial refugia for a number of temperate and Mediterranean trees is shown. A mid-Holocene phase (c. 7500-5200 cal yr BP) emerges regionally as the time of maximum forest development and highest lake levels. The early Holocene occurs as a generally dry, pyrophytic period of pine forests, with grassland scrub in high altitudes, and the late Holocene as a period of protracted vegetation sensitivity, with return to development of pine forests, spread of xerophytic communities, and increased fire activity, under the context of dry spells, localized anthropogenic disturbance, and shallowing and desiccation of lakes. Several events described here correlate with established times of abrupt transitions in the climates of northern Europe, the Mediterranean basin, north Africa, and the Sahel.

Late Quaternary loess in northeastern Colorado: Part I - Age and paleoclimatic significance

USGS Publications Warehouse

Muhs, D.R.; Aleinikoff, J.N.; Stafford, Thomas W.; Kihl, R.; Been, J.; Mahan, S.A.; Cowherd, S.

1999-01-01

Loess in eastern Colorado covers an estimated 14000 km2, and is the westernmost part of the North American midcontinent loess province. Stratigraphic studies indicate there were two periods of loess deposition in eastern Colorado during late Quaternary time. The first period spanned ca. 20 000 to 12 000 14C yr B.P. (ca. 20-14 ka) and correlates reasonably well with the culmination and retreat of Pinedale glaciers in the Colorado Front Range during the last glacial maximum. The second period of loess deposition occurred between ca. 11 000 and 9000 14C yr B.P. This interval may be Holocene or may correlate with a hypothesized Younger Dryas glacial advance in the Colorado Front Range. Sedimentologic, mineralogic, and geochemical data indicate that as many as three sources could have supplied loess in eastern Colorado. These sources include glaciogenic silt (derived from the Colorado Front Range) and two bedrock sources, volcaniclastic silt from the White River Group, and clays from the Pierre Shale. The sediment sources imply a generally westerly paleowind during the last glacial maximum. New carbon isotope data, combined with published faunal data, indicate that the loess was probably deposited on a cool steppe, implying a last glacial maximum July temperature depression, relative to the present, of at least 5-6??C. Overall, loess deposition in eastern Colorado occurred mostly toward the end of the last glacial maximum, under cooler and drier conditions, with generally westerly winds from more than one source.

Aridification of the Sahara desert caused by Tethys Sea shrinkage during Late Miocene

NASA Astrophysics Data System (ADS)

Zhang, Z.; Ramstein, G.; Schuster, M.; Li, C.; Contoux, C.; Yan, Q.

2014-12-01

It is widely believed that the Sahara desert is no more than ~2-3 million years (Myr) old, with geological evidence showing a remarkable aridification of north Africa at the onset of the Quaternary ice ages. Before that time, north African aridity was mainly controlled by the African summer monsoon (ASM), which oscillated with Earth's orbital precession cycles. Afterwards, the Northern Hemisphere glaciation added an ice volume forcing on the ASM, which additionally oscillated with glacial-interglacial cycles. These findings led to the idea that the Sahara desert came into existence when the Northern Hemisphere glaciated ~2-3 Myr ago. The later discovery, however, of aeolian dune deposits ~7 Myr old suggested a much older age, although this interpretation is hotly challenged and there is no clear mechanism for aridification around this time. Here we use climate model simulations to identify the Tortonian stage (~7-11 Myr ago) of the Late Miocene epoch as the pivotal period for triggering north African aridity and creating the Sahara desert. Through a set of experiments with the Norwegian Earth System Model and the Community Atmosphere Model, we demonstrate that the African summer monsoon was drastically weakened by the Tethys Sea shrinkage during the Tortonian, allowing arid, desert conditions to expand across north Africa. Not only did the Tethys shrinkage alter the mean climate of the region, it also enhanced the sensitivity of the African monsoon to orbital forcing, which subsequently became the major driver of Sahara extent fluctuations. These important climatic changes probably caused the shifts in Asian and African flora and fauna observed during the same period, with possible links to the emergence of early hominins in north Africa.

Regression-transgression cycles of paleolakes in the Fen River Graben Basin during the mid to late Quaternary and their tectonic implication

NASA Astrophysics Data System (ADS)

Chen, Meijun; Hu, Xiaomeng

2017-12-01

An investigation into lake terraces and their sedimentary features in the Fen River Graben Basin shows that several paleolake regression-transgression cycles took place during the mid to late Quaternary. The horizontal distribution of the lowest loess/paleosol unit overlying each lake terrace indicates the occurrence of four rapid lake regressions when paleosols S8, S5, S2, and S1 began to develop. The horizontal distribution of the topmost loess/ paleosol unit underlying the lacustrine sediment in each transition zone between two adjacent terraces indicates that following a lake regression, a very slow lake transgression occurred. The durations of three lake transgressions correspond to those of the deposition or development of loess/paleosols L8 to L6, L5 to L3, and L2. It is thereby inferred that regional tectonic movement is likely the primary factor resulting in the cyclical process of paleolake regressions and transgressions. Taking these findings along with published geophysical research results regarding the upper mantle movements underneath the graben basin into account, this paper deduces that a cause and effect relationship may exist between the paleolake regression-transgression cycles and the tectonic activity in the upper mantle. The occurrence of a rapid lake regression implies that the upwelling of the upper mantle underneath the graben basin may be dominant and resulting in a rapid uplifting of the basin floor. The subsequent slow lake transgression implies that the thinning of the crust and cooling of the warm mantle material underneath the graben basin may become dominant causing the basin floor to subside slowly. Four rapid paleolake regressions indicate that four episodic tectonic movements took place in the graben basin during the mid to late Quaternary.

Final closure of the Panamaian Isthmus and the onset of northern hemisphere glaciation

NASA Astrophysics Data System (ADS)

Sarnthein, M.; Bartoli, G.; Weinelt, M.; Erlenkeuser, H.; Garbe-Schoenberg, D.; Lea, D. W.

2005-12-01

The Greenland ice sheet forms a key factor controlling the Quaternary-style glacial scenario. However, origin and mechanisms of major Arctic glaciation starting at 3.15 Ma and culminating at 2.74 Ma have remained controversial. For this phase of intense cooling Ravelo et al. (2004) proposed a complex gradual forcing mechanism. In contrast, our new submillennial-scale paleoceanographic records from the Pliocene North Atlantic suggest a far more precise timing and forcing for the initiation of northern hemisphere glaciation (NHG), since it was linked to a 2-3 /degC surface water warming during warm stages from 2.95 to 2.82 Ma (until glacial stage G10). These records support previous models (Haug and Tiedemann, 1998) claiming that the final closure of the Panama Isthmus (3.0 - ~2.5 Ma; Groeneveld, 2005) induced an increased poleward salt and heat transport. Associated strengthening of North Atlantic thermohaline circulation and in turn, an intensified moisture supply to northern high latitudes resulted in the build-up of NHG, finally culminating in the great, irreversible climate crash at glacial stage G6 (2.74 Ma). In summary, we see a two-step threshold mechanism that marked the onset of NHG with glacial-to-interglacial cycles quasi-persistent until today. G r o e n e v e l d, J., The final closure of the Central American Seaway. PhD Thesis Kiel, 2005. H a u g, G. and T i e d e m a n n , R., 1 9 9 8. Nature 393, 676-678. R a v e l o , A.C., e t a l ., 2004. Nature 429, 263-267.

Late Quaternary landscape development at the margin of the Pomeranian phase (MIS 2) near Lake Wygonin (Northern Poland)

NASA Astrophysics Data System (ADS)

Hirsch, Florian; Schneider, Anna; Nicolay, Alexander; Błaszkiewicz, Mirosław; Kordowski, Jarosław; Noryskiewicz, Agnieszka M.; Tyszkowski, Sebastian; Raab, Alexandra; Raab, Thomas

2015-04-01

In Central Europe, Late Quaternary landscapes experienced multiple phases of geomorphologic activity. In this study,we used a combined geomorphological, pedological, sedimentological and palynological approach to characterize landscape development after the Last Glacial Maximum (LGM) near Lake Wygonin in Northern Poland. The pedostratigraphical findings from soil pits and drillings were extrapolated using ground-penetrating radar (GPR) and electric resistivity tomography (ERT). During the Pomeranian phase, glacial and fluvioglacial processes dominated the landscape near Lake Wygonin. At the end of the glacial period, periglacial processes became relevant and caused the formation of ventifacts and coversands containing coated sand grains. At approximately 15,290-14,800 cal yr BP, a small pond formed in a kettle hole (profile BWI2). The lacustrine sediments lack eolian sand components and therefore indicate the decline of eolian processes during that time. The increase of Juniperus and rock-rose (Helianthemum) in the pollen diagram is a prominent marker of the Younger Dryas. At the end of the Younger Dryas, a partial reshaping of the landscape is indicated by abundant charcoal fragments in disturbed lake sediments. No geomorphologic activity since the beginning of the Holocene is documented in the terrestrial and wetland archives. The anthropogenic impact is reflected in the pollen diagram by the occurrence of rye pollen grains (Cerealia type, Secale cereale) and translocated soil sediments dated to 1560-1410 cal yr BP, proving agricultural use of the immediate vicinity. With the onset of land use, gully incision and the accumulation of colluvial fans reshaped the landscape locally. Since 540-460 cal yr BP, further gully incision in the steep forest tracks has been associated with the intensification of forestry. Outside of the gully catchments, the weakly podzolized Rubic Brunic Arenosols show no features of Holocene soil erosion. Reprinted from CATENA, Volume 124

Late Quaternary paleoenvironments and paleoclimatic conditions in the distal Andean piedmont, southern Mendoza, Argentina

NASA Astrophysics Data System (ADS)

Tripaldi, Alfonsina; Zárate, Marcelo A.; Brook, George A.; Li, Guo-Qiang

2011-09-01

The Andean piedmont of Mendoza is a semiarid region covered by extensive and partially vegetated dune fields consisting of mostly inactive aeolian landforms of diverse size and morphology. This paper is focused on the San Rafael plain (SRP) environment, situated in the distal Andean piedmont of Mendoza (34° 30'S), and reports the sedimentology and OSL chronology of two representative exposures of late Quaternary deposits, including their paleoenvironmental and paleoclimatic significance. Eleven facies, including channel, floodplain, fluvio-aeolian interaction, and reworked pyroclastic and aeolian deposits, were described and grouped into two facies associations (FA1 and FA2). FA1 was formed by unconfined sheet flows, minor channelized streams and fluvial-aeolian interaction processes. FA2 was interpreted as aeolian dune and sand-sheet deposits. OSL chronology from the SRP sedimentary record indicates that between ca. 58-39 ka and ca. 36-24 ka (MIS 3), aggradation was governed by ephemeral fluvial processes (FA1) under generally semiarid conditions. During MIS 2, the last glacial maximum (ca. 24-12 ka), a major climatic shift to more arid conditions is documented by significant aeolian activity (FA2) that became the dominant sedimentation process north of the Diamante-Atuel fluvial system. The inferred paleoenvironmental conditions from the SRP sections are in broad agreement with regional evidence.

Late Quaternary Paleohydrology of Arroyo Cycles in the Mixteca Alta, Mexico: Insights from Past and Present Alluvial Stratigraphy

NASA Astrophysics Data System (ADS)

Holdridge, Geneviève; Leigh, David S.

2017-04-01

Arroyos are incised, ephemeral dryland streams that aggrade and incise on a cyclical timescale. Arroyo studies are integral to understanding landscape evolution in drylands, but the drivers and dynamics of arroyo cycles are not fully understood. This paper presents a study of arroyo stratigraphy in the semi-arid environment of the Mixteca Alta, Oaxaca, Mexico. Examination of the late Quaternary environment and geomorphology of the incised, ephemeral tributaries forming the Río Culebra watershed offered insight about the hydrological variability of the region. The characteristics and chronology of alluvium-paleosol sequences from three watersheds in the Mixteca Alta were examined along their upper, middle and downstream sections. In addition, the channel bedforms and stratigraphy of several watersheds were surveyed to evaluate the processes and morphology characterizing the present dryland stream system. Alluvium-paleosol sequences offered valuable information into the paleohydrology and dynamics of the arroyo cycles of the Mixteca Alta. Unweathered alluvium and paleosol formation in alluvium are two end members of alluvial stratigraphy. Cumulic A horizons form on floodplains when aggradation is slow enough to allow for pedogenesis. Cumulic A horizons were observed in both the Culebra and Verde watersheds from the late Pleistocene to the late Holocene, but not in the present-day arroyos, suggesting the prehistoric cumulic A horizons form in less flashy conditions than modern conditions. The geomorphic survey of present-day processes and forms included observing the bed stratigraphy associated with scouring-chains after flash floods. This examination offered insight to understanding and interpreting the alluvium-paleosol stratigraphy. For example, the present channel bed stratigraphy associated with scour-and-fill consists of poorly sorted, massive, sandy gravel deposits. Finer bedded sediments are observed in the present patchy floodplain deposits, but are

Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene

NASA Astrophysics Data System (ADS)

Zhang, Zhongshi; Ramstein, Gilles; Schuster, Mathieu; Li, Camille; Contoux, Camille; Yan, Qing

2014-09-01

It is widely believed that the Sahara desert is no more than ~2-3 million years (Myr) old, with geological evidence showing a remarkable aridification of north Africa at the onset of the Quaternary ice ages. Before that time, north African aridity was mainly controlled by the African summer monsoon (ASM), which oscillated with Earth's orbital precession cycles. Afterwards, the Northern Hemisphere glaciation added an ice volume forcing on the ASM, which additionally oscillated with glacial-interglacial cycles. These findings led to the idea that the Sahara desert came into existence when the Northern Hemisphere glaciated ~2-3 Myr ago. The later discovery, however, of aeolian dune deposits ~7 Myr old suggested a much older age, although this interpretation is hotly challenged and there is no clear mechanism for aridification around this time. Here we use climate model simulations to identify the Tortonian stage (~7-11 Myr ago) of the Late Miocene epoch as the pivotal period for triggering north African aridity and creating the Sahara desert. Through a set of experiments with the Norwegian Earth System Model and the Community Atmosphere Model, we demonstrate that the African summer monsoon was drastically weakened by the Tethys Sea shrinkage during the Tortonian, allowing arid, desert conditions to expand across north Africa. Not only did the Tethys shrinkage alter the mean climate of the region, it also enhanced the sensitivity of the African monsoon to orbital forcing, which subsequently became the major driver of Sahara extent fluctuations. These important climatic changes probably caused the shifts in Asian and African flora and fauna observed during the same period, with possible links to the emergence of early hominins in north Africa.

Late Quaternary Slip Rate Along the Selaha Fault, Central Segment of the Xianshuihe Fault System, Eastern Tibet, and Regional Paleoclimate Reconstruction

NASA Astrophysics Data System (ADS)

Chevalier, M. L.; Bai, M.; Pan, J.; Replumaz, A.; Leloup, P. H.; Li, H.

2017-12-01

The left-slip Xianshuihe fault system in E Tibet is considered as one of the most tectonically active fault system in China. Studying its activity, especially its slip rate at different time scales, is essential to evaluate regional earthquake hazards. Here, we focus on the central segment, where the Xianshuihe fault splays into three branches: the Selaha, Yalahe and Zheduotang faults. We use 10Be cosmogenic dating at 3 sites where the active Selaha fault cuts and left-laterally offsets moraine crests and levees. By matching their emplacement ages with their offsets, we obtain a conservative late Quaternary horizontal slip-rate of 5.7-12 mm/yr at TG levees and SLH moraine, or 9.6-9.9 mm/yr assuming that the slip rate should be constant between the two nearby sites. At YJG moraine, we obtain a lower slip rate of 4.4±0.5 mm/yr, most likely because the parallel Zheduotang fault shares the slip rate at this longitude, therefore suggesting a 5 mm/yr slip rate along the Zheduotang fault. A higher slip rate along the short ( 60 km) and discontinuous Selaha fault compared to that along the long ( 300 km) and linear Ganzi fault (7 mm/yr) suggests a high earthquake hazard in the densely populated city of Kangding. Using the moraine ages that we determined here in addition to our previous studies in the same region allows us to study the timing and extent of past glaciations in the Himalayan-Tibetan orogen. This is essential to reconstruct regional paleoclimate and to understand variations in the atmospheric circulation due to the high-altitude low latitude Tibetan Plateau, in order to possibly predict future climate changes. We dated 6 glacial deposits from SE Tibet using 10Be cosmogenic dating on 68 boulders and only found advances during the Last Glacial Maximum (limited) and Marine Isotope Stage-6 (extensive), with no signal in between. That the two coldest periods are LGM and MIS-6 is in agreement with the Northern hemisphere cooling cycles, suggesting that in SE Tibet

Moderate rates of late Quaternary slip along the northwestern margin of the Basin and Range Province, Surprise Valley fault, northeastern California

USGS Publications Warehouse

Personius, Stephen F.; Crone, Anthony J.; Machette, Michael N.; Mahan, Shannon; Lidke, David J.

2009-01-01

The 86-km-long Surprise Valley normal fault forms part of the active northwestern margin of the Basin and Range province in northeastern California. We use trench mapping and radiocarbon, luminescence, and tephra dating to estimate displacements and timing of the past five surface-rupturing earthquakes on the central part of the fault near Cedarville. A Bayesian OxCal analysis of timing constraints indicates earthquake times of 18.2 ± 2.6, 10.9 ± 3.2, 8.5 ± 0.5, 5.8 ± 1.5, and 1.2 ± 0.1 ka. These data yield recurrence intervals of 7.3 ± 4.1, 2.5 ± 3.2, 2.7 ± 1.6, and 4.5 ± 1.5 ka and an elapsed time of 1.2 ± 0.1 ka since the latest surface-rupturing earthquake. Our best estimate of latest Quaternary vertical slip rate is 0.6 ?? 0.1 mm/a. This late Quaternary rate is remarkably similar to long-term (8-14 Ma) minimum vertical slip rates (>0.4-0.5 ± 0.3 mm/a) calculated from recently acquired seismic reflection and chronologic and structural data in Surprise Valley and the adjacent Warner Mountains. However, our slip rate yields estimates of extension that are lower than recent campaign GPS determinations by factors of 1.5-4 unless the fault has an unusually shallow (30°-35°) dip as suggested by recently acquired seismic reflection data. Coseismic displacements of 2-4.5 ± 1 m documented in the trench and probable rupture lengths of 53-65 km indicate a history of latest Quaternary earthquakes of M 6.8-7.3 on the central part of the. Surprise Valley fault.

Geomorphology of submerged river channels indicates Late Quaternary tectonic activity in the Gulf of Trieste, Northern Adriatic

NASA Astrophysics Data System (ADS)

Vrabec, M.; Slavec, P.; Poglajen, S.; Busetti, M.

2012-04-01

channels. Sequential profiles perpendicular to the river course suggest consistent ~NE-ward lateral shifting of channels, parallel with inclination of the present-day seabed and with the present-day lateral gradient in channel depth. A longitudinal profile of the Rižana river plain revealed downstream increase in elevation of the stream bed, visible both from seabed bathymetry and from vertical position of channel lag deposits in subbottom sonar profiles. These observations suggest post-depositional tectonic tilting of the fluvial sediments that could be related either to activation of NE-dipping thrusts in the pre-Quaternary basement, or to minor anticlinal folding associated with Quaternary transpressional faulting along NW-SE-trending zones, implied from seismic profiles NW-ward of our study area. An enigmatic low-sinuosity channel feature runs along the coastline in the NE-SW direction and crosses the paleo-Rižana channel. Subbottom sonar profiles show asymmetric channel geometry and strong reflectors (channel lag deposits?) at the channel bottom, typical of other documented river channels in the area. This feature is vertically offset by a NE-SW-trending linear morphological flexure that corresponds in location and orientation to the onshore Monte Spaccato fault. Subbottom profiling revealed in several places an abrupt truncation of horizontal reflectors that could be manifestation of faulting. These indications of Late Quaternary - Holocene tectonic activity may have important implications for seismic hazard in the heavily populated coastal area of the Gulf of Trieste.

Recognition of late Precambrian glaciogenic sediments in Liberia

NASA Astrophysics Data System (ADS)

Magee, A. W.; Culver, S. J.

1986-11-01

Late Precambrian glaciation in West Africa is now suggested to have extended as far south as Gibi Mountain in west-central Liberia, 200 km farther south than previously recognized glacial deposits in central Sierra Leone. The Gibi Mountain Formation includes a basal diamictite, interpreted as a probable tillite, and overlying shallow-marine laminites containing isolated, ice-rafted dropstones and dropgrains. These rocks rest on Late Archean age gneisses and are overlain by Late Archean? age quartzite klippen emplaced during the pan-African orogeny (ca. 550 Ma). *Present address: School of Geography, University of Oxford, Mansfield Road, Oxford OKI 3TB, England

Evolution of the polar oceans: the late Quaternary palaeoceanography of the Northwest Passage

NASA Astrophysics Data System (ADS)

Pienkowski, Anna; Furze, Mark; England, John; MacLean, Brian; Bennett, Robbie; Blasco, Steve; McNeely, Morgan

2014-05-01

The marine channels of the Canadian Arctic Archipelago, collectively known as the "Northwest Passage" (= NWP), cover some 1.1 million km2 on the North American continental shelf and constitute one of two primary pathways for water and heat exchange between the Arctic and Atlantic oceans. Modern circulation is characterized by a net southeastward flow from the Arctic Ocean through Parry Channel (the main W-E axis of the NWP) towards Baffin Bay, with Arctic Ocean Surface Water primarily occupying the NWP channels. Data from recent and ongoing marine work* highlight a dynamic oceanographic environment since the last glaciation. A suite of five sediment records (piston and trigger weight cores) taken in a transect through Parry Channel provide important information on the long-term (deglacial to postglacial) environmental and oceanographic evolution of the region. The cores were studied by a multiproxy approach encompassing sedimentology, micropalaeontology, biogeochemistry, constrained by a chronological framework of 58 AMS radiocarbon dates. Our data suggest grounded glacial ice in the channels of the Canadian Arctic Archipelago, rapid deglaciation, and a characteristic progression from ice-proximal to ice-distal conditions. Age model extrapolations place deglaciation at ~13.0-10.3 cal ka BP (location dependent). Noticeable biological activity is marked by the appearance of planktonic foraminifera (Neogloboquadrina pachyderma) at ~11.0 cal ka BP - an important signal given the absence of these organisms in the modern NWP. This likely marks the penetration of Atlantic-derived water (Arctic Intermediate Water) into the central NWP following deglaciation, likely facilitated by higher deglacial sea-levels permitting increased flow across inter-channel sills. Though the route of this Atlantic-derived water is currently being resolved, it may have penetrated from Baffin Bay in the East into the NWP, contrary to the modern circulation. Subsequent (~9.7-7.0 cal ka BP

Evidence for glaciation in Elysium

NASA Technical Reports Server (NTRS)

Anderson, Duwayne M.; Brandstrom, Gary W.

1987-01-01

It is suggested that certain landforms in the Elysium region of Mars provide strong evidence for glaciation. Landscapes related to subglacial volcanism suggest that ice was a primary agent in the development of Elysium.

Deep-sea ostracode species diversity: Response to late Quaternary climate change

USGS Publications Warehouse

Cronin, T. M.; DeMartino, D.M.; Dwyer, Gary S.; Rodriguez-Lazaro, J.

1999-01-01

Late Quaternary ostracode assemblages from the North Atlantic Ocean were studied to establish the effect of climatic changes of the past 210,000 yr (marine oxygen isotope stages 7–1) on deep-sea benthic biodiversity and faunal composition. Two-hundred and twenty five samples from the Chain 82-24 Core 4PC (41°43′N, 32°51′W, 3427 m water depth) on the western Mid-Atlantic Ridge revealed high amplitude fluctuations in ostracode abundance and diversity coincident with orbital and suborbital scale climate oscillations measured by several paleoceanographic proxy records. During the past 210,000 yr, ostracode biodiversity as measured by species number (S) and the Shannon–Weaver index, H(S), oscillated from H(S)=0.4 during glacial periods (marine isotope stages 6, 5d, 5b, 4, and 2) to H(S)=1.1 during interglacial and interstadial periods (stages 7, 5e, 5c, 5a, 3 and 1). A total of 23 diversity peaks could be recognized. Eleven of these signify major periods of high diversity [H(S)>0.8, S = 10–21] occurring every 15–20 ka. Twelve were minor peaks which may represent millennial-scale diversity oscillations. The composition of ostracode assemblages varies with Krithe-dominated assemblages characterizing glacial intervals, and Argilloecia–Cytheropteron characterizing deglacials, and trachyleberid genera (Poseidonamicus, Echinocythereis, Henryhowella, Oxycythereis) abundant during interglacials. Diversity and faunal composition changes can be matched to independent deep-sea paleoceanographic tracers such as benthic foraminiferal carbon isotopes, Krithe trace elements (Mg/Ca ratios), and to North Atlantic region climate records such as Greenland ice cores. When interpreted in light of ostracode species' ecology, these faunal and diversity patterns provide evidence that deep-sea benthic ecosystems experience significant reorganization in response to climate changes over orbital to millennial timescales.

Northern Hemisphere glaciation and the evolution of Plio-Pleistocene climate noise

NASA Astrophysics Data System (ADS)

Meyers, Stephen R.; Hinnov, Linda A.

2010-08-01

Deterministic orbital controls on climate variability are commonly inferred to dominate across timescales of 104-106 years, although some studies have suggested that stochastic processes may be of equal or greater importance. Here we explicitly quantify changes in deterministic orbital processes (forcing and/or pacing) versus stochastic climate processes during the Plio-Pleistocene, via time-frequency analysis of two prominent foraminifera oxygen isotopic stacks. Our results indicate that development of the Northern Hemisphere ice sheet is paralleled by an overall amplification of both deterministic and stochastic climate energy, but their relative dominance is variable. The progression from a more stochastic early Pliocene to a strongly deterministic late Pleistocene is primarily accommodated during two transitory phases of Northern Hemisphere ice sheet growth. This long-term trend is punctuated by “stochastic events,” which we interpret as evidence for abrupt reorganization of the climate system at the initiation and termination of the mid-Pleistocene transition and at the onset of Northern Hemisphere glaciation. In addition to highlighting a complex interplay between deterministic and stochastic climate change during the Plio-Pleistocene, our results support an early onset for Northern Hemisphere glaciation (between 3.5 and 3.7 Ma) and reveal some new characteristics of the orbital signal response, such as the puzzling emergence of 100 ka and 400 ka cyclic climate variability during theoretical eccentricity nodes.

Late Quaternary Deformation and Relative Sea Level Changes in Southwest Luzon, Philippines Constrained from Emergent Coral Reef Terraces

NASA Astrophysics Data System (ADS)

Maxwell, K. V.; Ramos, N. T.; Tsutsumi, H.; Shen, C. C.

2017-12-01

Emergent coral reef terraces fringing the islands of Lubang and Cabra located offshore southwest Luzon Island, Philippines are studied to understand Late Quaternary deformation and relative sea level changes along the southern terminus of the Manila subduction zone. In both islands, the emergent coral reef platforms have two to three terrace steps with meter-scale terrace risers and often well preserved. We also observed varied elevations of emergent coral reef platforms in both localities. In the northwest portion of Lubang Island, we identified three terrace steps, which rise to about 5 m above mean sea level (amsl). Cabra Island is a coral island that is fringed by two to possibly three steps of emergent coral reef terraces rising up to 11.9 m amsl with TI measured at 3-6 m, TII: 7-8 m, and TIII: 11.9 m amsl. Age constraints are provided by Thorium-230 of fossil corals taken on terrace surfaces. Thorium-230 ages obtained from attached fossil coral samples yielded mid-Holocene ages of 5,121 ± 16 and 3,221 ± 10 years BP. Late Holocene ages of 76 ± 2, 153 ± 2, and 330 ± 3 years BP are meanwhile provided by coral boulders found on the surface of TI in Cabra Island. The two sets of Holocene ages provide interesting insights on relative sea level changes and uplift along the southern end of the Manila Trench. The mid-Holocene ages possibly account for accumulated uplift in southwest Luzon while the late Holocene ages could provide evidence for extreme wave events that occurred in the region since the 1600s.

Late Quaternary palaeoecological and palaeoclimatological reconstruction in the Gutaiului Mountains, northwest Romania

NASA Astrophysics Data System (ADS)

Feurdean, Angelica; Bennike, Ole

2004-12-01

Macrofossil, pollen, lithostratigraphy, mineral magnetic measurements (SIRM and magnetic susceptibility), loss-on-ignition, and AMS radiocarbon dating on sediments from two former crater lakes, situated at moderate altitudes in the Gutaiului Mountains of northwest Romania, allow reconstruction of Late Quaternary climate and environment. Shrubs and herbs with steppe and montane affinities along with stands of Betula and Pinus, colonised the surroundings of the sites prior to 14 700 cal. yr BP and the inferred climatic conditions were cold and dry. The gradual transition to open Pinus-Betula forests, slightly higher lake water temperatures, and higher lake productivity, indicate more stable environmental conditions between 14 700 and 14 100 cal. yr BP. This development was interrupted by cooler and drier climatic conditions between 14 100 and 13 800 cal. yr BP, as inferred from a reduction of open forests to patches, or stands, of Pinus, Betula, Larix, Salix and Populus. The expansion of a denser boreal forest, dominated by Picea, but including Pinus, Larix, Betula, Salix, and Ulmus started at 13 800 cal. yr BP, although the forest density seems to have been reduced between 13400 and 13200cal.yrBP. Air temperature and moisture availability gradually increased, but a change towards drier conditions is seen at 13400cal.yrBP. A distinct decrease in temperature and humidity between 12900 and 11500cal.yrBP led to a return of open vegetation, with patches of Betula, Larix, Salix, Pinus and Alnus and individuals of Picea. Macrofossils and pollen of aquatic plants indicate rising lake water temperatures and increased aquatic productivity already by ca. 11800cal.yrBP, 300 years earlier than documented by the terrestrial plant communities. At the onset of the Holocene, 11500cal.yrBP, forests dominated by Betula, Pinus and Larix expanded and were followed by dense Ulmus forests with Picea, Betula and Pinus at 11250cal.yrBP. Larix pollen was not found, but macrofossil evidence

Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records

PubMed Central

Storey, Michael; Roberts, Richard G.; Saidin, Mokhtar

2012-01-01

The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated 40Ar/39Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our 40Ar/39Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard–Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our 40Ar/39Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of 14C dating. PMID:23112159

Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records

NASA Astrophysics Data System (ADS)

Storey, Michael; Roberts, Richard G.; Saidin, Mokhtar

2012-11-01

The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated 40Ar/39Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our 40Ar/39Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard-Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our 40Ar/39Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of 14C dating.

Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records.

PubMed

Storey, Michael; Roberts, Richard G; Saidin, Mokhtar

2012-11-13

The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated (40)Ar/(39)Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our (40)Ar/(39)Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard-Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our (40)Ar/(39)Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of (14)C dating.

Evolution of Topography in Glaciated Mountain Ranges

NASA Technical Reports Server (NTRS)

Brocklehurst, Simon H.

2002-01-01

This thesis examines the response of alpine landscapes to the onset of glaciation. The basic approach is to compare fluvial and glacial laudscapes, since it is the change from the former to the latter that accompanies climatic cooling. This allows a detailed evaluation of hypotheses relating climate change to tectonic processes in glaciated mountain belts. Fieldwork was carried out in the eastern Sierra Nevada, California, and the Sangre de Cristo Range, Colorado, alongside digital elevation model analyses in the western US, the Southern Alps of New Zealand, and the Himalaya of northwestern Pakistan. hypothesis is overstated in its appeal to glacial erosion as a major source of relief production and subsequent peak uplift. Glaciers in the eastern Sierra Nevada and the western Sangre de Cristos have redistributed relief, but have produced only modest relief by enlarging drainage basins at the expense of low-relief topography. Glaciers have lowered valley floors and ridgelines by similar amounts, limiting the amount of "missing mass' that can be generated, and causing a decrease in drainage basin relief. The principal response of glaciated landscapes to rapid rock uplift is the development of towering cirque headwalls. This represents considerable relief production, but is not caused by glacial erosion alone. Large valley glaciers can maintain their low gradient regardless of uplift rate, which supports the "glacial buzzsaw" hypothesis. However, the inability of glaciers to erode steep hillslopes as rapidly can cause mean elevations to rise. Cosmogenic isotope dating is used to show that (i) where plucking is active, the last major glaciation removed sufficient material to reset the cosmogenic clock; and (ii) former glacial valley floors now stranded near the crest of the Sierra Nevada are at varying stages of abandonment, suggesting a cycle of drainage reorganiszation and relief inversion due to glacial erosion similar to that observed in river networks. Glaciated

Quaternary Activity of the Erciyes Fault Southeast of the Kayseri Basin, Turkey

NASA Astrophysics Data System (ADS)

Okumura, K.; Hayakawa, Y. S.; Kontani, R.; Fikri, K.

2016-12-01

The Erciyes fault in SE of the Kayseri basin is one of the most active Quaternary faults in Central Anatolia. Emre et al. (2011) mapped about 100 km long faults including a section runs across the Erciyes volcano. A M 7+ earthquake from the fault would be a big threat for the 1.5 million people in Kayseri basin, but little has been know about its activity and earthquake potential. We studied Plio-Pleistocene volacanics, Quaternary sediments, and UAV-SfM topography in southeast of the Kayseri basin and recognized significant dip-slip separation as well as sinistral slip in Late Quaternary. The Incesu ignimbrite (IC) of 2.52±0.49 Ma (Aydar et al., 2012) is a very distinctive densely welded ignimbrite layer in and around Kayseri basin. The Plinian pumice fall deposits from the Erciyes in Late Pleistocene (Sen et al. 2003) at Gesi Bagpnar (GBP) is another key-bed. There are two strands and one group of faults. The NE strike frontal strand separates the basin floor and the upland in SW extending from Kayseri city to more than 50 km NE. The Gesi Guney strand runs parallel to the frontal strand at 3 to 4 km away from the basin floor for 20 km from Ali Dag. The NS trending fault group is observed both inside and outside of the basin under IC. These NS faults are swarm of normal Pliocene faults. The Gesi Guney strand offsets IC around 120 m vertically. There is no information to infer the initiation of its activity, but the normal offset of an alluvial fan and unconsolidated fresh talus deposits indicate Late Quaternary activities. Near the SW end of the frontal strand, IC is vertically offset around 40 m. 15 km NE from the SW end, sand and gravel layers that intercalates GBP (0.11-0.14 Ma) are tilted to NW for 30 to 40 m and truncated by a sub-vertical sinistral faults. Most of frontal strand deformation occurred in Late Pleistocene because the offset of IC and GBP are similar. Estimated slip-rate of 0.3 to 0.4 mm/yr is significant for Central Anatolia.

Lake sediments documented late Quaternary humid pulses in the Gobi Desert of southern Mongolia: Vegetation, hydrologic and paleoglaciation inferences

NASA Astrophysics Data System (ADS)

Yu, Kaifeng; Lehmkuhl, Frank; Schlütz, Frank; Diekmann, Bernhard; Mischke, Steffen; Grunert, Jörg; Murad, Waheed; Nottebaum, Veit; Stauch, Georg

2016-04-01

Considerable efforts have been devoted to decipher the late Quaternary moisture and thermal history of the arid central Asia. However, an array of paramount aspects has inhibited our complete understanding of the broad pattern and underlying mechanisms: (i) Biased or even contradictory conclusions may be achieved due to the interpretations of different proxies. (ii) Most of the works poured attention into Holocene period, only few records can extend back to earlier marine isotope stages. (iii) Substantial spatial heterogeneity is noteworthy in the area. Exceeding amounts of studies were carried out in Lake Baikal catchments, northern and western Mongolia, while only two works were hitherto conducted in southern Mongolia. (iv) It remains elusive with respect to how and to what extent have East Asian Summer Monsoon and Westerlies affected the thermal and moisture signals in this spectacular arid region. To address this set of issues, two parallel cores (ONW I, 6.00 m; ONW II, 13.36 m) were retrieved from Orog Nuur, Gobi Desert of southern Mongolia. An array of multidisciplinary investigations involving geomorphologic mapping, radiocarbon dating, geochemical and biotic studies (i.e., palynological and ostracod valve analyses) provide a comprehensive data set for inferences of hydrological perturbations, vegetation development and phases of glacier expansions over the last ~50 ka. Orog Nuur catchment depicted a broadly vulnerable ecosystem that was dominated by Artemisia steppe community in the late Pleistocene, and Chenopodiaceae desert steppe in the Holocene. In addition, the Termination I is ideally documented in a complete suite of geochemical, palynological, and ostracod signatures. In general, the thermal and moisture history in the Gobi Desert were as follows: (i) MIS3 had a relatively warm temperature and sufficient moisture supply in particular between ~40 ka and ~26 ka; (ii) The MIS2 was subject to cold temperature and moisture deficit, which was interrupted

Variable impact of late-Quaternary megafaunal extinction in causing ecological state shifts in North and South America

NASA Astrophysics Data System (ADS)

Barnosky, Anthony D.; Lindsey, Emily L.; Villavicencio, Natalia A.; Bostelmann, Enrique; Hadly, Elizabeth A.; Wanket, James; Marshall, Charles R.

2016-01-01

Loss of megafauna, an aspect of defaunation, can precipitate many ecological changes over short time scales. We examine whether megafauna loss can also explain features of lasting ecological state shifts that occurred as the Pleistocene gave way to the Holocene. We compare ecological impacts of late-Quaternary megafauna extinction in five American regions: southwestern Patagonia, the Pampas, northeastern United States, northwestern United States, and Beringia. We find that major ecological state shifts were consistent with expectations of defaunation in North American sites but not in South American ones. The differential responses highlight two factors necessary for defaunation to trigger lasting ecological state shifts discernable in the fossil record: (i) lost megafauna need to have been effective ecosystem engineers, like proboscideans; and (ii) historical contingencies must have provided the ecosystem with plant species likely to respond to megafaunal loss. These findings help in identifying modern ecosystems that are most at risk for disappearing should current pressures on the ecosystems' large animals continue and highlight the critical role of both individual species ecologies and ecosystem context in predicting the lasting impacts of defaunation currently underway.

No surface breaking on the Ecemiş Fault, central Turkey, since Late Pleistocene (~ 64.5 ka); new geomorphic and geochronologic data from cosmogenic dating of offset alluvial fans

NASA Astrophysics Data System (ADS)

Sarıkaya, M. A.; Yıldırım, C.; Çiner, A.

2015-05-01

The Ecemiş Fault Zone (EF) has been recognized as a major left lateral strike-slip fault in the Central Anatolian Fault Zone (CAFZ) of Turkey. However, its Quaternary slip-rate has been challenging to determine due to the difficulty of dating offset markers. Using high-precision offset measurements and 36Cl cosmogenic nuclide dating, we present the first geochronologically determined Late Quaternary slip-rate for the EF. Our study focuses on the excellent exposures of offset alluvial fan surfaces, originating from the Aladağlar, a Late Quaternary glaciated mountain. Analysis of airborne orthophotogrametry and GNSS (Global Navigation Satellite System) surveys indicates 168 ± 2 m left lateral and 31 ± 1 m vertical displacements. In-situ terrestrial cosmogenic 36Cl geochronology obtained from eleven surface boulders provides a minimum abandonment/incision age of 104.2 ± 16.5 ka for the oldest offset alluvial fan surface. Our geomorphic observations together with Self-potential geophysical surveys revealed the presence of an unfaulted alluvial fan terrace, which allows us to constrain the timing of deformation. The abandonment/incision age of this fan is 64.5 ± 5.6 ka based on thirteen 36Cl depth profile samples. Accordingly, we obtained a geologic fault slip-rate of 4.2 ± 1.9 mm a- 1 horizontally and 0.8 ± 0.3 mm a- 1 vertically for the time frame between 104.2 ± 16.5 ka and 64.5 ± 5.6 ka. Our analysis indicates that the EF has not been producing a major surface breaking earthquake on the main strand at least since 64.5 ± 5.6 ka (mid-Late Pleistocene). This could be the result of abandonment of the main strand and accommodation of deformation by other faults within the EF. Nevertheless, a recently occurred (30 September 2011) low magnitude (ML: 4.3) left lateral strike-slip earthquake indicates recent seismic activity of the EF. Comparison of the recent GPS velocity field with the longer slip history along the CAFZ indicates a constant but low strain

First High-Resolution Record of Late Quaternary Environmental Changes in the Amundsen Sea, West Antarctica, Revealed by Multi-proxy Analysis of Drift Sediments

NASA Astrophysics Data System (ADS)

Horrocks, J.; Ó Cofaigh, C.; Lloyd, J. M.; Hillenbrand, C. D.; Kuhn, G.; Smith, J.; Ehrmann, W. U.; Esper, O.

2015-12-01

The Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) is experiencing rapid mass loss and there is a pressing need to place the contemporary ice-sheet changes into a longer term context. The continental rise in this region is characterised by large sediment mounds that are shaped by westward flowing bottom currents and that resemble contouritic drifts existing offshore from the Antarctic Peninsula. Similar to the Antarctic Peninsula drifts, marine sediment cores from the poorly studied sediment mounds in the Amundsen Sea have the potential to provide reliable records of dynamical ice-sheet behaviour in West Antarctica and palaeoceanographic changes in the Southern Ocean during the Late Quaternary that can be reconstructed from their terrestrial, biogenic and authigenic components. Here we use multi-proxy data from three sediment cores recovered from two of the Amundsen Sea mounds to present the first high-resolution study of environmental changes on this part of the West Antarctic continental margin over the glacial-interglacial cycles of the Late Quaternary. Age constraints for the records are derived from biostratigraphy, AMS 14C dates and lithostratigraphy. We focus on the investigation of processes for drift formation, thereby using grain size and sortable silt data to reconstruct changes in bottom current speed and to identify episodes of current winnowing. Data on geochemical and mineralogical sediment composition and physical properties are used to infer both changes in terrigenous sediment supply in response to the advance and retreat of the WAIS across the Amundsen Sea shelf and changes in biological productivity that are mainly controlled by the duration of annual sea-ice coverage. We compare our data sets from the Amundsen Sea mounds to those from the well-studied Antarctic Peninsula drifts, thereby highlighting similarities and discrepancies in depositional processes and climatically-driven environmental changes.

Late Quaternary history of the Atacama Desert

USGS Publications Warehouse

Latorre, Claudio; Betancourt, Julio L.; Rech, Jason A.; Quade, Jay; Holmgren, Camille; Placzek, Christa; Maldonado, Antonio; Vuille, Mathias; Rylander, Kate A.; Smith, Mike; Hesse, Paul

2005-01-01

Of the major subtropical deserts found in the Southern Hemisphere, the Atacama Desert is the driest. Throughout the Quaternary, the most pervasive climatic influence on the desert has been millennial-scale changes in the frequency and seasonality of the scant rainfall, and associated shifts in plant and animal distributions with elevation along the eastern margin of the desert. Over the past six years, we have mapped modern vegetation gradients and developed a number of palaeoenvironmental records, including vegetation histories from fossil rodent middens, groundwater levels from wetland (spring) deposits, and lake levels from shoreline evidence, along a 1200-kilometre transect (16–26°S) in the Atacama Desert. A strength of this palaeoclimate transect has been the ability to apply the same methodologies across broad elevational, latitudinal, climatic, vegetation and hydrological gradients. We are using this transect to reconstruct the histories of key components of the South American tropical (summer) and extratropical (winter) rainfall belts, precisely at those elevations where average annual rainfall wanes to zero. The focus has been on the transition from sparse, shrubby vegetation (known as the prepuna) into absolute desert, an expansive hyperarid terrain that extends from just above the coastal fog zone (approximately 800 metres) to more than 3500 metres in the most arid sectors in the southern Atacama.

A Late-Glacial sedimentary sequence at KIlkeel, Northern Ireland: implications for the glaciation of the Irish Sea Basin

NASA Astrophysics Data System (ADS)

Merritt, Jon; Roberson, Sam; Cooper, Mark

2017-04-01

of cross-trough stratified sandy gravels, with flame structures indicative of syn-depositional loading. The entire sequence is capped by loose interbedded sands and gravels (LA4) representing a Late-Glacial raised beach. Evidence of a marine terminating ice margin provides support for high relative sea levels in the north western sector of the Irish Sea during deglaciation. Forthcoming dates from shells with the rafted subaqueous fan deposits underlying LF2 provide the opportunity to constrain either: a) sea-level rise prior to the onset of Irish Sea Basin glaciation, or, b) Late-Glacial sea level rise following deglaciation of the Irish Sea and prior to the re-advance of local ice masses.

Compound-Specific Hydrogen Isotope Evidence of Late Quaternary Paleohydrologic Change from the Atlantic Coastal Plain, North Carolina, USA

NASA Astrophysics Data System (ADS)

Lane, C.; Taylor, A. K.; Spencer, J.; Jones, K.

2017-12-01

Reconstructions of late Quaternary paleohydrology are rare from the U.S. Atlantic coastal plain (ACP). Here we present compound-specific hydrogen isotope analyses of terrestrially-derived n-alkanes (δ2Halkane) from Jones Lake and Singletary Lake in eastern North Carolina spanning the last 50,000 years. Combined with prior pollen, charcoal, and bulk sediment geochemical analyses, the δ2Halkane data indicate arid conditions during the late-Pleistocene, but marked differences in edaphic conditions at the two sites likely due to differing water table depths. The Pleistocene-Holocene transition is marked by rapid fluctuations in δ2Halkane values that resemble the Bølling Allerød and Younger Dryas climatic events indicating potential sensitivity of regional hydrology to rapid climate change. The δ2Halkane data indicate a generally mesic Holocene that supported colonization by Quercus-dominated ecosystems during the early to middle Holocene. Evidence of increased aridity on the in eastern Tennessee and western North Carolina contrasts with evidence of mesic conditions in eastern North Carolina during the middle to late Holocene, a geographic pattern similar to modern teleconnected precipitation responses to the Pacific Decadal Oscillation. This pattern may be indicative of a stronger Pacific basin influence on regional paleoprecipitation patterns than the distally-closer Atlantic. A transition from Quercus-to Pinus-dominated ecosystems 5500 cal yr B.P. is accompanied by a large increase in charcoal abundance, but is not coincident with any high-amplitude changes in the δ2Halkane record, indicating that precipitation variability was not likely the mechanism responsible for this ecological transition. While further development of regional paleohydrological records is necessary, the lack of a clear change in middle Holocene precipitation dynamics and the temporally-heterogeneous nature of the Quercus-Pinus transition in the region indicate prehistoric anthropogenic

Map Showing Limits of Tahoe Glaciation in Sequoia and Kings Canyon National Parks, California

USGS Publications Warehouse

Moore, James Gregory; Mack, Gregory S.

2008-01-01

The latest periods of extensive ice cover in the Sierra Nevada include the Tahoe glaciation followed by the Tioga glaciation, and evidence for these ice ages is widespread in the Sequoia and Kings Canyon National Parks area. However, the timing of the advances and retreats of the glaciers during the periods of glaciation continues to be a matter of debate. A compilation of existing work (Clark and others, 2003) defines the Tioga glaciation at 14-25 thousand years ago and splits the Tahoe glaciation into two stages that range from 42-50 and 140-200 thousand years ago. The extent of the Tahoe ice mass shown in the map area is considered to represent the younger Tahoe stage, 42-50 thousand years ago. Evidence of glaciations older than the Tahoe is limited in the southern Sierra Nevada. After the Tioga glaciation, only minor events with considerably less ice cover occurred. The Tioga glaciation was slightly less extensive than the Tahoe glaciation, and each covered about half of the area of Sequoia and Kings Canyon National Parks. The Tahoe glaciers extended 500-1,000 ft lower and 0.5-1.2 mi farther down valleys. Evidence for the Tahoe glacial limits is not as robust as that for Tioga, but the extent of the Tahoe ice is mapped because it covered a larger area and the ice did leave prominent moraines (piles of sediment and boulders deposited by glaciers as they melted at their margins) lower on the east front of the range. Current Sierra redwood (Sequoiadendron giganteum) groves occur in a belt on the west side of the Sierra Nevada, generally west of the area of Tahoe glaciation.

The role of climate and vegetation on woolly mammoth extinction on St. Paul Island, Alaska and megafauna extinction in North America in the late Quaternary

NASA Astrophysics Data System (ADS)

Wang, Y.; Porter, W.; Miller, P. A.; Graham, R. W.; Williams, J. W.

2016-12-01

Estimate of megafauna behaviors dynamically under associated environmental factors is important to understand the mechanisms and causes of the late Quaternary megafaunal extinctions. On St. Paul Island, an isolated remnant of the Bering Land Bridge, a late-surviving population of woolly mammoth (Mammuthus primigenius) persisted until 5,600 cal BP, while 37 out of 54 megafauna species in the continent of North America, all herbivores, went extinct at the end of Pleistocene between 13,800 and 11,500 cal BP. Proposed natural drivers of the extinction events include abrupt temperature changes, food resource loss and freshwater shortage. Here we tested these three hypothesized mechanisms, using a physiological model (Niche Mapper) to estimate individual megafauna behaviors from the perspectives of metabolic rate, individual vegetation and freshwater requirement under simulated climates from Community Climate System Model version 3 (CCSM3), vegetation reconstructions based on dynamic LPJ-GUESS model and woolly mammoth and megafauna species trait data reconstructed based on mammal fossils. Preliminary simulations of woolly mammoth on St. Paul Island point to the importance of net vegetation primary productivity and freshwater availability as limits on the carrying capacity of St. Paul for mammoth populations, with a low carrying capacity in the middle Holocene making this population highly vulnerable to extinction. Results also indicate that the abrupt warming based around 14,000 cal BP in Bering land bridge on CCSM3 simulations causes woolly mammoth extinction, by driving metabolic rate high up beyond the active basic metabolic rate. Analysis suggests a positive relationship between temperature and metabolic rate, and woolly mammoth would go extinct when summer temperature is up to 12 °C or higher. However the temperature reconstructed based on regional proxies is relatively stable compared to CCSM3 simulations, and leads to stable metabolic rate of woolly mammoth and

Late-Glacial to Late-holocene Shifts in Global Precipitation Delta(sup 18)O

NASA Technical Reports Server (NTRS)

Jasechko, S.; Lechler, A.; Pausata, F.S.R.; Fawcett, P.J.; Gleeson, T.; Cendon, D.I.; Galewsky, J.; LeGrande, A. N.; Risi, C.; Sharp, Z. D.;

Insight to forcing of late Quaternary climate change from aeolian dust archives in eastern Australia

NASA Astrophysics Data System (ADS)

McGowan, H. A.; Marx, S.; Soderholm, J.; Denholm, J.; Petherick, L.

2010-12-01

The Australian continent is the largest source of dust in the Southern Hemisphere. Historical dust emissions records display inter-annual variability in response to the El Niño Southern Oscillation (ENSO) phenomenon and inter-decadal variability which has been linked to the Pacific Decadal Oscillation (PDO). These reflect change in hydrometeorology of the continents two major dust source regions, the Murray-Darling Basin and the Lake Eyre Basin. The historical records do not allow longer term variability of ENSO and the PDO and their influence on Australia to be quantified. Importantly, sub-Milankovitch centennial to multi-millennial scale climate cycles and their impacts are not represented in the historical records. In this paper we present summary results from the analysis of two aeolain dust records spanning 7 ka and 45 ka. These were developed from ombrotrophic mire and lacustrine sediment cores collected from the Australian Alps and southeast Queensland. Both sites are located in the southeast Australian dust transport pathway and provide rare insight to forcings of climate variability and its impacts on eastern Australia through the late Quaternary. Age controls for the cores were established using 14C and 210Pb dating [McGowan et al. 2008, 2010]. The cores were sliced into 2 to 5 mm segments with a sub-sample of each segment combusted at 450°C for 12 hrs to destroy organic material and allow recovery of mineral dust. Geochemical fingerprinting of the < 90 µm fraction of the dust was used to determine provenance and to account for contamination by fluvial and/or colluvial sediments [Marx et al. 2005]. Analysis of the dust records, proxy for hydrometeorology, identified tropical ocean teleconnections, variability of solar irradiance and change in ocean deep water circulation as the principal causes of inter-decadal to centennial scale climate cycles and change. Predictions of future climate must consider these forcings so that in water scarce regions of

Late Quaternary Megafaunal Extinctions in Northern Eurasia: Latest Results

NASA Astrophysics Data System (ADS)

Stuart, Anthony

2010-05-01

Anthony J. Stuart1 & Adrian M. Lister2 1 Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK. Email: tony.s@megafauna.org.uk 2 Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK. Email: a.lister@nhm.ac.uk. The global extinction of many spectacular species of megafauna (large terrestrial mammals, together with a few large reptiles and birds) within the last c. 50,000 years (Late Quaternary) has been attributed on the one hand to ‘overkill' by human hunters and on the other to environmental change. However, in spite of more than half a century of active interest and research the issue remains unresolved, largely because there are insufficient dated records of megafaunal species for most parts of the world. Northern Eurasia is an especially fruitful region in which to research megafaunal extinctions as it has a wealth of megafaunal material and crucially most extinctions occurred well within the range of radiocarbon dating. Our approach, in a series of projects over the last decade funded by the UK Natural Environment Research Council (NERC), involves amassing radiocarbon dates made directly on megafaunal material from across the entire region: a) by submitting a substantial number of samples (so far c. 500 dates) for AMS dating at Oxford (ORAU); b) obtaining AMS dates from colleagues working on aDNA projects; and c) carefully screening (‘auditing') dates from the literature. The dates (calibrated using OxCal) are plotted as time-sliced maps and as chronological/geographical charts. In our previous work we targeted a range of extinct species from Northern Eurasia: woolly mammoth, woolly rhinoceros, giant deer, cave bear (in collaboration with Martina Pacher), cave lion, and spotted hyaena (which survives today only in Sub-Saharan Africa). By this means we have established a reliable chronology for these extinctions which we are able to compare with the climatic, vegetational and

Glaciation at the Eastern Hellas Margin

NASA Image and Video Library

2014-08-13

Hellas Crater in the ancient highlands contains some of the clearest evidence on Mars for glacial processes. This image from NASA Mars Reconnaissance Orbiter shows a number of features consistent with glaciation.

Quaternary and Geomorphology.

ERIC Educational Resources Information Center

Andrews, J. T.; Graf, W. L.

1983-01-01

Highlights conferences and meetings of organizations involved with quaternary geology and geomorphology, including International Union of Quaternary Research Conference held in Moscow. The impetus of a revision of "The Quaternary of the United States" resulted from this conference. Includes activities/aims of "Friends of the…

Late quaternary slip-rate variations along the Warm Springs Valley fault system, northern Walker Lane, California-Nevada border

USGS Publications Warehouse

Gold, Ryan; dePolo, Craig; Briggs, Richard W.; Crone, Anthony

2013-01-01

The extent to which faults exhibit temporally varying slip rates has important consequences for models of fault mechanics and probabilistic seismic hazard. Here, we explore the temporal behavior of the dextral‐slip Warm Springs Valley fault system, which is part of a network of closely spaced (10–20 km) faults in the northern Walker Lane (California–Nevada border). We develop a late Quaternary slip record for the fault using Quaternary mapping and high‐resolution topographic data from airborne Light Distance and Ranging (LiDAR). The faulted Fort Sage alluvial fan (40.06° N, 119.99° W) is dextrally displaced 98+42/-43 m, and we estimate the age of the alluvial fan to be 41.4+10.0/-4.8 to 55.7±9.2  ka, based on a terrestrial cosmogenic 10Be depth profile and 36Cl analyses on basalt boulders, respectively. The displacement and age constraints for the fan yield a slip rate of 1.8 +0.8/-0.8 mm/yr to 2.4 +1.2/-1.1 mm/yr (2σ) along the northern Warm Springs Valley fault system for the past 41.4–55.7 ka. In contrast to this longer‐term slip rate, shorelines associated with the Sehoo highstand of Lake Lahontan (~15.8  ka) adjacent to the Fort Sage fan are dextrally faulted at most 3 m, which limits a maximum post‐15.8 ka slip rate to 0.2  mm/yr. These relations indicate that the post‐Lahontan slip rate on the fault is only about one‐tenth the longer‐term (41–56 ka) average slip rate. This apparent slip‐rate variation may be related to co‐dependent interaction with the nearby Honey Lake fault system, which shows evidence of an accelerated period of mid‐Holocene earthquakes.

A rock-magnetic record from Lake Baikal, Siberia: Evidence for Late Quaternary climate change

USGS Publications Warehouse

Peck, J.A.; King, J.W.; Colman, Steven M.; Kravchinsky, V.A.

1994-01-01

Rock-magnetic measurements of sediment cores from the Academician Ridge region of Lake Baikal, Siberia show variations related to Late Quaternary climate change. Based upon the well-dated last glacial-interglacial transition, variations in magnetic concentration and mineralogy are related to glacial-interglacial cycles using a conceptual model. Interglacial intervals are characterized by low magnetic concentrations and a composition that is dominated by low coercivity minerals. Glacial intervals are characterized by high magnetic concentrations and increased amounts of high coercivity minerals. The variation in magnetic concentration is consistent with dilution by diatom opal during the more productive interglacial periods. We also infer an increased contribution of eolian sediment during the colder, windier, and more arid glacial conditions when extensive loess deposits were formed throughout Europe and Asia. Eolian transport is inferred to deliver increased amounts of high coercivity minerals as staining on eolian grains during the glacial intervals. Variations in magnetic concentration and mineralogy of Lake Baikal sediment correlate to the SPECMAP marine oxygen-isotope record. The high degree of correlation between Baikal magnetic concentration/mineralogy and the SPECMAP oxygen-isotope record indicates that Lake Baikal sediment preserves a history of climate change in central Asia for the last 250 ka. This correlation provides a method of estimating the age of sediment beyond the range of the radiocarbon method. Future work must include providing better age control and additional climate proxy data, thereby strengthening the correlation of continental and marine climate records. ?? 1994.

Eolian additions to late Quaternary alpine soils, Indian Peaks Wilderness Area, Colorado Front Range

USGS Publications Warehouse

Muhs, D.R.; Benedict, J.B.

2006-01-01

Surface horizons of many alpine soils on Quaternary deposits in high-mountain settings are enriched in silt. The origin of these particles has been debated, particularly in the Rocky Mountain region of North America. The most common explanations are frost shattering of coarser particles and eolian additions from distant sources. We studied soil A horizons on alpine moraines of late-glacial (Satanta Peak) age in the Colorado Front Range. Surface horizons of soils on these moraines are enriched in silt and have a particle size distribution that resembles loess and dust deposits found elsewhere. The compositions of sand and silt fractions of the soils were compared to possible local source rocks, using immobile trace elements Ti, Nb, Zr, Ce, and Y. The sand fractions of soils have a wide range of trace element ratios, similar to the range of values in the local biotite gneiss bedrock. In contrast, silt fractions have narrower ranges of trace element ratios that do not overlap the range of these ratios in biotite gneiss. The particle size and geochemical results support an interpretation that silts in these soils are derived from airborne dust. Eolian silts were most likely derived from distant sources, such as the semiarid North Park and Middle Park basins to the west. We hypothesize that much of the eolian influx to soils of the Front Range occurred during an early to mid-Holocene warm period, when sediment availability in semiarid source basins was at a maximum.

A Million-Year Record of Glaciation in the Tropical Andes

NASA Astrophysics Data System (ADS)

Smith, J. A.; Seltzer, G. O.; Rodbell, D. T.; Farber, D. L.; Finkel, R. C.

2004-12-01

We present a longterm record of glaciation in the tropical Andes based on cosmogenic dating (10Be) of boulders on moraines. Well-preserved moraines in deglaciated valleys bordering the Junin Plain in central Peru ( ˜11° S, 76° W, 4000 m) were deposited during several glacial cycles extending back more than one million years before present (1 Myr BP). The presence of boulders with zero-erosion 10Be exposure ages >1 Myr constrains boulder erosion rates to relatively low values. For boulders at high altitudes, however, even low boulder erosion rates (0.3 to 0.5 m/Myr) make calculated old exposure ages markedly older [e.g., ˜20% older for a zero-erosion age of 400,000 10Be years (400 10Be kyr)]. Exposure ages recalculated with boulder erosion rates of 0.3 m/Myr straddle interglacial marine isotope stage (MIS) 11 ( ˜430-390 kyr BP), fall within glacial MIS 12 ( ˜480-430 kyr BP), but skip over glacial MIS 16 ( ˜670-630 kyr BP), perhaps the largest ice volume of the past 2 Myr. Increasing the erosion rate used in the calculations to 0.5 m/Myr moves ages into both MIS 11 and MIS 16. If we assume that the older Andean glaciations were indeed synchronous with global ice volume, our data suggest that boulder preservation cannot be treated as a simple linear process. Conversely, the data may be suggesting correctly that glaciation of the tropical Andes was not synchronous with the global glaciations as inferred from the marine isotope record. Our chronology for the last glacial maximum (LGM) in the region supports the idea of asynchrony between the global ice volume record and the terrestrial record of glaciation in the tropical Andes. The LGM in the Junin region of Peru and in the Cordillera Real of Bolivia (16° S 68° W) occurred ˜34 to 22 10Be kyr BP and was less extensive than older glaciations. Asynchrony between the LGM in the Northern Hemisphere ( ˜21 kyr BP) and the tropical Andes suggests that previous glaciations in the tropical Andes may have been

Quaternary glaciation and hydrologic variation in the South American tropics as reconstructed from the Lake Titicaca drilling project

NASA Astrophysics Data System (ADS)

Fritz, Sherilyn C.; Baker, Paul A.; Seltzer, Geoffrey O.; Ballantyne, Ashley; Tapia, Pedro; Cheng, Hai; Edwards, R. Lawrence

2007-11-01

A 136-m-long drill core of sediments was recovered from tropical high-altitude Lake Titicaca, Bolivia-Peru, enabling a reconstruction of past climate that spans four cycles of regional glacial advance and retreat and that is estimated to extend continuously over the last 370,000 yr. Within the errors of the age model, the periods of regional glacial advance and retreat are concordant respectively with global glacial and interglacial stages. Periods of ice advance in the southern tropical Andes generally were periods of positive water balance, as evidenced by deeper and fresher conditions in Lake Titicaca. Conversely, reduced glaciation occurred during periods of negative water balance and shallow closed-basin conditions in the lake. The apparent coincidence of positive water balance of Lake Titicaca and glacial growth in the adjacent Andes with Northern Hemisphere ice sheet expansion implies that regional water balance and glacial mass balance are strongly influenced by global-scale temperature changes, as well as by precessional forcing of the South American summer monsoon.

Phylogeographic heterogeneity of the brown macroalga Sargassum horneri (Fucaceae) in the northwestern Pacific in relation to late Pleistocene glaciation and tectonic configurations.

PubMed

Hu, Zi-Min; Uwai, Shinya; Yu, Shen-Hui; Komatsu, Teruhisa; Ajisaka, Tetsuro; Duan, De-Lin

2011-09-01

Pleistocene glacial oscillations and associated tectonic processes are believed to have influenced the historical abundances and distribution of organisms in the Asia Northwest Pacific (ANP). Accumulating evidence indicates that factors shaping tempospatial population dynamics and distribution patterns of marine taxa vary with biogeographical latitude, pelagic behaviour and oceanographic regimes. To detect what kinds of historical and contemporary factors affected genetic connectivity, phylogeographic profiles of littoral macroalga Sargassum horneri in the ANP were analysed based on mitochondrial (Cox3) and chloroplast (rbcL) data sets. Five distinct clades were recovered. A strong signature of biogeographical structure was revealed (Φ(CT) = 0.487, P < 0.0001) derived from remarkable differentiation in clade distribution, as clade I is restricted to Chinese marginal seas (Yellow-Bohai Sea, East China Sea and South China Sea), whereas clades II-V are discontinuously scattered around the main Islands of Japan. Furthermore, two secondary contact regions were identified along the south Japan-Pacific coastline. This significant differentiation between the two basins may reflect historical glacial isolation in the northwestern Pacific, which is congruent with the estimates of clade divergence and demographic expansion during the late Quaternary low sea levels. Analysis of molecular variance and the population-pair statistic F(ST) also revealed significant genetic structural differences between Chinese marginal seas and the Japanese basin. This exceptional phylogeographic architecture in S. horneri, initially shaped by historical geographic isolation during the late Pleistocene ice age and physical biogeographical barriers, can be complicated by oceanographic regimes (ocean surface currents) and relocating behaviour such as oceanic drifting. © 2011 Blackwell Publishing Ltd.

Variable impact of late-Quaternary megafaunal extinction in causing ecological state shifts in North and South America

PubMed Central

Barnosky, Anthony D.; Lindsey, Emily L.; Villavicencio, Natalia A.; Bostelmann, Enrique; Hadly, Elizabeth A.; Wanket, James; Marshall, Charles R.

2016-01-01

Loss of megafauna, an aspect of defaunation, can precipitate many ecological changes over short time scales. We examine whether megafauna loss can also explain features of lasting ecological state shifts that occurred as the Pleistocene gave way to the Holocene. We compare ecological impacts of late-Quaternary megafauna extinction in five American regions: southwestern Patagonia, the Pampas, northeastern United States, northwestern United States, and Beringia. We find that major ecological state shifts were consistent with expectations of defaunation in North American sites but not in South American ones. The differential responses highlight two factors necessary for defaunation to trigger lasting ecological state shifts discernable in the fossil record: (i) lost megafauna need to have been effective ecosystem engineers, like proboscideans; and (ii) historical contingencies must have provided the ecosystem with plant species likely to respond to megafaunal loss. These findings help in identifying modern ecosystems that are most at risk for disappearing should current pressures on the ecosystems’ large animals continue and highlight the critical role of both individual species ecologies and ecosystem context in predicting the lasting impacts of defaunation currently underway. PMID:26504219

Timing of the last glaciation and subsequent deglaciation in the Ruby Mountains, Great Basin, USA

NASA Astrophysics Data System (ADS)

Laabs, Benjamin J. C.; Munroe, Jeffrey S.; Best, Laura C.; Caffee, Marc W.

2013-01-01

The timing of the last Pleistocene glaciation in western North America is becoming increasingly well understood, largely due to improved methods of obtaining numerical ages of glacial deposits and landforms. Among these, cosmogenic radionuclide surface-exposure dating has been widely applied to moraines of mountain glaciers, providing the framework for understanding terrestrial climate change during and since the last glaciation in western North America. During the Late Pleistocene, the Great Basin of the western United States hosted numerous mountain glaciers, the deposits of which can provide valuable records of past climate changes if their ages can be precisely determined. In this study, twenty-nine cosmogenic radionuclide 10Be surface-exposure ages from a suite of moraines in Seitz Canyon, western Ruby Mountains, limit the timing of the last glacial episode in the interior Great Basin, known as the Angel Lake Glaciation. Results indicate that deposition of a terminal moraine and two recessional moraines began just prior to ˜20.5 ka and continued until ˜20.0 ka. Retreat from the next younger recessional moraine began at ˜17.2 ka, and final deglaciation began at ˜14.8 ka. These ages are broadly consistent with cosmogenic surface-exposure ages from the eastern Sierra Nevada and the western Wasatch Mountains, in the western and eastern extremes of the Great Basin respectively. Furthermore, these ages suggest that the valley glacier in Seitz Canyon was at or near its maximum extent before and during the hydrologic maxima of Pleistocene lakes in the Great Basin, supporting previous suggestions that a cool and wet climate persisted in this region during the early part of the last glacial-interglacial transition.

Arsenic stress after the Proterozoic glaciations

NASA Astrophysics Data System (ADS)

Chi Fru, Ernest; Arvestål, Emma; Callac, Nolwenn; El Albani, Abderrazak; Kilias, Stephanos; Argyraki, Ariadne; Jakobsson, Martin

2015-12-01

Protection against arsenic damage in organisms positioned deep in the tree of life points to early evolutionary sensitization. Here, marine sedimentary records reveal a Proterozoic arsenic concentration patterned to glacial-interglacial ages. The low glacial and high interglacial sedimentary arsenic concentrations, suggest deteriorating habitable marine conditions may have coincided with atmospheric oxygen decline after ~2.1 billion years ago. A similar intensification of near continental margin sedimentary arsenic levels after the Cryogenian glaciations is also associated with amplified continental weathering. However, interpreted atmospheric oxygen increase at this time, suggests that the marine biosphere had widely adapted to the reorganization of global marine elemental cycles by glaciations. Such a glacially induced biogeochemical bridge would have produced physiologically robust communities that enabled increased oxygenation of the ocean-atmosphere system and the radiation of the complex Ediacaran-Cambrian life.

Arsenic stress after the Proterozoic glaciations.

PubMed

Fru, Ernest Chi; Arvestål, Emma; Callac, Nolwenn; El Albani, Abderrazak; Kilias, Stephanos; Argyraki, Ariadne; Jakobsson, Martin

2015-12-04

Protection against arsenic damage in organisms positioned deep in the tree of life points to early evolutionary sensitization. Here, marine sedimentary records reveal a Proterozoic arsenic concentration patterned to glacial-interglacial ages. The low glacial and high interglacial sedimentary arsenic concentrations, suggest deteriorating habitable marine conditions may have coincided with atmospheric oxygen decline after ~2.1 billion years ago. A similar intensification of near continental margin sedimentary arsenic levels after the Cryogenian glaciations is also associated with amplified continental weathering. However, interpreted atmospheric oxygen increase at this time, suggests that the marine biosphere had widely adapted to the reorganization of global marine elemental cycles by glaciations. Such a glacially induced biogeochemical bridge would have produced physiologically robust communities that enabled increased oxygenation of the ocean-atmosphere system and the radiation of the complex Ediacaran-Cambrian life.

Response of the Pacific inter-tropical convergence zone to global cooling and initiation of Antarctic glaciation across the Eocene Oligocene Transition

PubMed Central

Hyeong, Kiseong; Kuroda, Junichiro; Seo, Inah; Wilson, Paul A.

2016-01-01

Approximately 34 million years ago across the Eocene–Oligocene transition (EOT), Earth’s climate tipped from a largely unglaciated state into one that sustained large ice sheets on Antarctica. Antarctic glaciation is attributed to a threshold response to slow decline in atmospheric CO2 but our understanding of the feedback processes triggered and of climate change on the other contents is limited. Here we present new geochemical records of terrigenous dust accumulating on the sea floor across the EOT from a site in the central equatorial Pacific. We report a change in dust chemistry from an Asian affinity to a Central-South American provenance that occurs geologically synchronously with the initiation of stepwise global cooling, glaciation of Antarctica and aridification on the northern continents. We infer that the inter-tropical convergence zone of intense precipitation extended to our site during late Eocene, at least four degrees latitude further south than today, but that it migrated northwards in step with global cooling and initiation of Antarctic glaciation. Our findings point to an atmospheric teleconnection between extratropical cooling and rainfall climate in the tropics and the mid-latitude belt of the westerlies operating across the most pivotal transition in climate state of the Cenozoic Era. PMID:27507793

Response of the Pacific inter-tropical convergence zone to global cooling and initiation of Antarctic glaciation across the Eocene Oligocene Transition

NASA Astrophysics Data System (ADS)

Hyeong, Kiseong; Kuroda, Junichiro; Seo, Inah; Wilson, Paul A.

2016-08-01

Approximately 34 million years ago across the Eocene-Oligocene transition (EOT), Earth’s climate tipped from a largely unglaciated state into one that sustained large ice sheets on Antarctica. Antarctic glaciation is attributed to a threshold response to slow decline in atmospheric CO2 but our understanding of the feedback processes triggered and of climate change on the other contents is limited. Here we present new geochemical records of terrigenous dust accumulating on the sea floor across the EOT from a site in the central equatorial Pacific. We report a change in dust chemistry from an Asian affinity to a Central-South American provenance that occurs geologically synchronously with the initiation of stepwise global cooling, glaciation of Antarctica and aridification on the northern continents. We infer that the inter-tropical convergence zone of intense precipitation extended to our site during late Eocene, at least four degrees latitude further south than today, but that it migrated northwards in step with global cooling and initiation of Antarctic glaciation. Our findings point to an atmospheric teleconnection between extratropical cooling and rainfall climate in the tropics and the mid-latitude belt of the westerlies operating across the most pivotal transition in climate state of the Cenozoic Era.

Late quaternary temperature record from buried soils of the North American Great Plains

USGS Publications Warehouse

Nordt, L.; Von Fischer, J.; Tieszen, L.

2007-01-01

We present the first comprehensive late Quaternary record of North American Great Plains temperature by assessing the behavior of the stable isotopic composition (δ13C) of buried soils. After examining the relationship between the δ13C of topsoil organic matter and July temperature from 61 native prairies within a latitudinal range of 46°–38°N, we applied the resulting regression equation to 64 published δ13C values from buried soils of the same region to construct a temperature curve for the past 12 k.y. Estimated temperatures from 12 to 10 ka (1 k.y. = 1000 14C yr B.P.) fluctuated with a periodicity of ∼1 k.y. with two cool excursions between −4.5 and −3.5 °C and two warmer excursions between −1 and 0 °C, relative to modern. Early Holocene temperatures from ca. 10–7.5 ka were −1.0 to −2.0 °C before rising to +1.0 °C in the middle Holocene between 6.0 and 4.5 ka. After a cool interlude from 4.2 to 2.6 ka, when temperatures dropped to slightly below modern, another warm interval ensued from 2.6 to 1 ka as temperatures increased to ∼+0.5 °C. A final decline in temperature to below modern occurred beginning ca. 0.5 ka. Cooler than present temperatures in the Great Plains indicate telecommunications with cool-water episodes in the Gulf of Mexico and North Atlantic potentially governed by a combination of glacial meltwater pulses and low solar irradiance.

Oman's low latitude "Snowball Earth" pole revisited: Late Cretaceous remagnetisation of Late Neoproterozoic carbonates in Northern Oman

NASA Astrophysics Data System (ADS)

Rowan, C. J.; Tait, J.

2010-12-01

Glaciogenic diamictites and associated ‘cap’ carbonates within the Neoproterozoic Huqf Supergroup of Oman record a period of extreme, possibly global, glaciations between 750-635 Ma (the "Snowball Earth"). We have performed high-resolution paleomagnetic sampling of two sections through ~635 Ma cap carbonates in the Jebel Akhdar region of northern Oman. Stepwise thermal demagnetisation reveals a low temperature component carried by goethite, and a high temperature component carried by haematite, that are both aligned with the modern dipole field direction. Occasional reversed polarity directions antipodal to the present day field indicate pervasive weathering of these outcrops over timescales of at least 1 Ma. Between these two overprints an intermediate component with typical unblocking temperatures of 300-550 C, probably carried by magnetite, can also be isolated in most samples. A robust fold test clearly demonstrates that this component was acquired after Paleozoic folding of the carbonates, and was most likely acquired during exhumation associated with emplacement of the Semail ophiolite during the Late Cretaceous (95-68 Ma). In geographic co-ordinates, the intermediate component has an almost horizontal NNW or SSE direction, similar to directions previously reported from outcrops of the ophiolite close to the Jebel Akhdar region, and from thermally altered basement rocks in the the Saih Hatat window further to the east [Feinberg et al. 1999]. Hints of an older, Permian, remagnetisation of the carbonates, which is also observed in the Saih Hatat basement rocks, have also produced a false polarity stratigraphy in one of the sampled sections. Our results contrast with the previously reported low latitude pole from the Huqf Supergroup [Kilner et al., 2005], which was considered to be amongst the more reliable paleomagnetic data supporting glaciations extending to low latitudes during the late Neoproterozoic. However, this interpretation was made on the basis

Linking glacial melting to Late Quaternary sedimentation in climatically sensitive mountainous catchments of the Mount Chlemos compex, Kalavryta, southern Greece

NASA Astrophysics Data System (ADS)

Pope, Richard; Hughes, Philip

2014-05-01

local last glacial maximum and are coeval with the later part of the Tymphian stage in the Pindus range. Refs: Hughes, P.D., Woodward, J.C., Gibbard, P.L., Macklin, M.G., Gilmour, M.A. & Smith G.R. (2006) The glacial history of the Pindus Mountains, Greece. Journal of Geology 114, 413-434. Hughes, P.D., Woodward, J.C., van Calsteren, P.C. and Thomas, L.E. (2011) The Glacial History of The Dinaric Alps, Montenegro. Quaternary Science Reviews 30, 3393-3412. Woodward, J.C., Hamlin, R.H.B., Macklin, M.G., Hughes, P.D. & Lewin, J. (2008) Pleistocene catchment dynamics in the Mediterranean: glaciation, fluvial geomorphology and the slackwater sediment record. Geomorphology 101, 44-67.

Late Quaternary environments and biogeography in the Great Basin

NASA Astrophysics Data System (ADS)

Thompson, R. S.; Mead, J. I.

1982-01-01

Plant and animal remains found in packrat ( Neotoma spp.) middens and cave fill from the eastern and southern Great Basin region reveal the presence of subalpine conifers and boreal mammals at relatively low elevations during the Late Wisconsin. Limber pine ( Pinus flexilis) and bristlecone pine ( P. longaeva) were important in the late Pleistocene plant communities throughout this region. Spruce ( Picea cf. engelmannii) and common juniper ( Juniperus communis) were present in some of the more northerly localities, and Douglas fir ( Pseudotsuga menziesii) and white fir ( Abies concolor) were present in southern and eastern localities. Single needle pinyon pine ( Pinus monophylla), common across this region today, was apparently not present north of the Sheep Range of southern Nevada during the Late Wisconsin. Pikas ( Ochotona cf. princeps), small boreal mammals present in only a few Great Basin mountain ranges today, were common throughout the region. Heather voles ( Phenacomys cf. intermedius) have been found in two cave fill deposits in Nevada, though they are unknown in the Great Basin today. Limber and bristlecone pines are generally restricted to rocky substrates in modern subalpine habitats in the Great Basin, and this may also have been the case when these plants grew at lower elevations during the Late Wisconsin. Subalpine conifers were present on the rock outcrops sampled by the packrat middens, but shrub communities, perhaps dominated by sagebrush ( Artemisia spp.), may have been present on alluvial valley-bottom substrates. Forested habitats would thus have been isolated habitat islands, as they are today. Boreal small mammals, including pikas and heather voles, were able to colonize the Great Basin mountain ranges during the late Pleistocene. We suggest that these mammals were able to survive in the intervening valley-bottoms under a cool-summer climatic regime, and that continuous forest or woodland corridors were not necessary for migration.

Late Quaternary activity of the Ecemiş Fault Zone, Turkey; implications from cosmogenic 36Cl dating of offset alluvial fans

NASA Astrophysics Data System (ADS)

Akif Sarıkaya, Mehmet; Yıldırım, Cengiz; Çiner, Attila

2014-05-01

The Ecemiş Fault Zone is the southernmost segment of the Central Anatolian Fault Zone. The tectonic trough of the fault zone defines the boundary between the Central and Eastern Taurides Ranges. The presence of faulted alluvial fans and colluvium within this trough provide favorable conditions to unravel the Late Quaternary slip-rate of the fault zone by cosmogenic surface exposure dating. In this context, we focused on the main strand of the fault zone and also on the Cevizlik Fault that delimits the mountain front of the Aladaǧlar, Eastern Taurides. Geomorphic mapping and topographic surveying indicate four different alluvial fan levels deposited along the main strand. Our topographic survey reveals 60±5 m horizontal and 18±2 m vertical displacement of the oldest fan surface (AF1) associated with the main strand of the fault zone. We dated the surface of the AF1 with 13 cosmogenic 36Cl samples. Our results indicate that the AF1 surface was abandoned maximum 105.3±1.5 ka ago. Accordingly, we propose 0.57±0.05 mm/yr horizontal and 0.17±0.02 mm/yr vertical mean slip-rates since 100 ka for the main strand. On the other hand, we measured 20±2 m vertical displacement on the colluvium along the Cevizlik Fault. The surface exposure age of the colluvium yielded 21.9±0.3 ka that translates to 0.91±0.09 mm/yr vertical slip-rate for the Cevizlik Fault. Our results reveal significant Quaternary deformation, and low strain rates might indicate very long earthquake recurrence intervals along the fault zone.

Accelerating late Quaternary uplift of the New Georgia Island Group (Solomon island arc) in response to subduction of the recently active Woodlark spreading center and Coleman seamount

NASA Astrophysics Data System (ADS)

Mann, Paul; Taylor, Frederick W.; Lagoe, Martin B.; Quarles, Andrew; Burr, G.

1998-10-01

The New Georgia Island Group of the Solomon Islands is one of four places where an active or recently active spreading ridge has subducted beneath an island arc. We have used coral reef terraces, paleobathymetry of Neogene sedimentary rocks, and existing marine geophysical data to constrain patterns of regional Quaternary deformation related to subduction of the recently active Woodlark spreading center and its overlying Coleman seamount. These combined data indicate the following vertical tectonic history for the central part of the New Georgia Island Group: (1) subsidence of the forearc region (Tetepare and Rendova Islands) to water depths of ˜1500 m and deposition of marine turbidites until after 270 ka; (2) late Quaternary uplift of the forearc to sea level and erosion of an unconformity; (3) subsidence of the forearc to ˜500 m BSL and deposition of bathyal sediments; and (4) uplift of the forearc above sea level with Holocene uplift rates up to at least 7.5 mm/yr on Tetepare and 5 mm/yr on Rendova. In the northeastern part of the New Georgia Island Group, our combined data indicate a slightly different tectonic history characterized by lower-amplitude vertical motions and a more recent change from subsidence to uplift. Barrier reefs formed around New Georgia and Vangunu Islands as they subsided >300 m. By 50-100 ka, subsidence was replaced by uplift that accelerated to Holocene rates of ˜1 mm/yr on the volcanic arc compared with rates up to ˜7.5 mm/yr in the forearc area of Tetepare and Rendova. Uplift mechanisms, such as thermal effects due to subduction of spreading ridges, tectonic erosion, or underplating of deeply subducted bathymetric features, are not likely to function on the 270-ka period that these uplift events have occurred in the New Georgia Island Group. A more likely uplift mechanism for the post-270-ka accelerating uplift of the forearc and volcanic arc of the New Georgia Island Group is progressive impingement of the Coleman seamount or

Discovering buried channels of the Yamuna in alluvial plains of NW India using geophysical investigations: implications for major drainage reorganization during Late Quaternary

NASA Astrophysics Data System (ADS)

Paul, D.; Khan, I.; Sinha, R.

2016-12-01

Climatic changes and active tectonic movements in the northwestern plains of India during the Late Quaternary have led to the migration and abandonment of drainage systems and formation of a large number of palaeochannels. It has been postulated by previous workers that the Yamuna was flowing along the present-day dry palaeochannels of Ghaggar-Hakra riverbed >120 Ka ago and was relocated to its current position only during the Late Quaternary. However, till date, no conclusive evidence has been provided as to when and why the Yamuna avulsion occurred. This study aims to establish sub-surface existence of buried channels of paleo-Yamuna as possible courses of the paleo-Ghaggar river. Geo-electric studies using vertical electrical resistivity soundings (1D-VES), multi electrode electrical resistivity tomography (2D-ERT) and multi probe well log surveys have been carried out in one of the paleochannels of the Yamuna to map the large-scale geometry and architecture of the palaeochannel system in the subsurface. The main objective is to reconstruct the shallow subsurface stratigraphy and alluvial architecture of the interfluve between the modern Yamuna and Sutlej Rivers, in particular the linkage of the paleocourses of the Yamuna River to the drainage network of the northwestern alluvial plains. The geophysical signatures recorded as VES on two transects trending NW-SE in Karnal and Kaithal districts of Haryana at 9 and 13 locations respectively along with continuous ERT reveals the presence of subsurface fine to coarse sand bodies (20 to 30m thick) interbedded with silty clay layers that are laterally stacked. The occurrence of thick and wide subsurface sand bodies in the subsurface implies that these are the deposits of a large river system and suggests that the Yamuna was connected to the paleo-Ghaggar River as hypothesized by earlier workers based on remote sensing techniques. However, detailed sedimentological and chronological constraints are required to establish

The SE sector of the Middle Weichselian Eurasian Ice Sheet was much smaller than assumed

NASA Astrophysics Data System (ADS)

Räsänen, Matti E.; Huitti, Janne V.; Bhattarai, Saroj; Harvey, Jerry; Huttunen, Sanna

2015-08-01

Quaternary climatic and glacial history must be known in order to understand future environments. Reconstructions of the last Weichselian glacial cycle 117,000-11,700 years (kyr) ago propose that S Finland, adjacent Russia and the Baltic countries in the SE sector of the Eurasian Ice Sheet (EIS), were glaciated during the Middle Weichselian time [marine isotope stage (MIS) 4, 71-57 kyr ago] and that this glaciation was preceded in S Finland by an Early Weichselian interstadial (MIS 5c, 105-93 kyr ago) with pine forest. We apply glacial sequence stratigraphy to isolated Late Pleistocene onshore outcrop sections and show, that these events did not take place. The one Late Weichselian glaciation (MIS 2, 29-11 kyr ago) was preceded in S Finland by a nearly 90 kyr non-glacial period, featuring tundra with permafrost and probably birch forest. Our new Middle Weichselian paleoenvironmental scenario revises the configuration and hydrology of the S part of EIS and gives new setting for the evolution of Scandinavian biota. If future development during the coming glacial cycle proves to be similar, the high-level nuclear waste stored in the bedrock of SW Finland should be located deeper than currently planned, i.e. below any possible future permafrost.

Seeking Hidden Glaciations in the Greenhouse World: A New Approach Using Nd Isotopes

NASA Astrophysics Data System (ADS)

Scher, H. D.; Bohaty, S. M.

2009-12-01

Ephemeral polar glaciations during the early Cenozoic and Cretaceous have been proposed to account for excursions to higher benthic foraminiferal δ18O values, variations in foraminiferal Sr/Ca ratios, and high-frequency eustatic sea level changes. This interpretation requires modifying the view of an “ice-free” greenhouse climate and raises new questions about how the climate system operated in a greenhouse state. However, very limited information has been gathered about these glaciations, partly because direct sedimentological evidence for ice sheets is lacking. Based on constraints from δ18O records and sea-level estimates, it appears that these glaciations were associated with the growth of small-to-medium ice sheets (5 to 15 x 106 km3) on Antarctica. If these ice sheets were confined to the Antarctic interior, they may not have left any physical evidence of their existence in proximal marine sediments. Yet, it may be possible to detect these “hidden glaciations” with proxies for continental weathering. Neodymium (Nd) isotopes have the potential to identify hidden glaciations because ancient basement rocks on Antarctica are glacially eroded during ice sheet advances. The accompanying weathering pulses contribute an extremely nonradiogenic fingerprint to the Southern Ocean. Nd isotope records derived from fossil fish teeth from circum-Antarctic sediment cores confirm that the Nd isotopic composition of Southern Ocean water masses shifted regionally toward nonradiogenic ɛNd values during the buildup of ice sheets during the Eocene-Oligocene Transition (EOT). The observed response to glacial weathering is particularly relevant to examining ephemeral glaciations because a strong Nd isotope response accompanies the first δ18O step of the EOT. This step, i.e., the precursor glaciation, most likely reflects ice sheets confined to the interior and coastal mountains of Antarctica, which represents a similar situation to the purported ephemeral glaciations

Spatial Correlation Bias in Thermochronologically Derived Late Cenozoic Erosion Histories

NASA Astrophysics Data System (ADS)

Schildgen, T. F.; van Der Beek, P.; Sinclair, H. D.; Thiede, R. C.

2017-12-01

The potential link between erosion rates at the Earth's surface and changes in global climate has intrigued geoscientists for decades, as such a coupling has implications for the influence of silicate weathering and organic-carbon burial on climate, as well as the role of Quaternary glaciations on landscape evolution. A global increase in late-Cenozoic erosion rates in response to a cooling, more variable climate has been proposed based on a compilation of deposition rates in sedimentary basins worldwide. However, it has been argued that the stratigraphic record could show an apparent increase in rates toward the present due to a preservation bias linked to stochastic erosional events, depositional hiatuses, and varying measurement intervals. More recently, a global compilation of thermochronology data has been used to infer a nearly two-fold increase in erosion rates from mountainous landscapes over the late Cenozoic. It is contended that this result is free of the biases that affect sedimentary records. Here, we test this assumption and demonstrate that in addition to the bias resulting from the relative timescales over which thermochronological data are averaged, there is a bias associated with spatial variations in exhumation rates among points that are combined to derive exhumation histories. Whether one or multiple thermochronological systems are used to reconstruct an erosion history, there is always an apparent increase in rates toward the present when combining data that have not shared a common exhumation history (e.g., samples collected from different sides of an active tectonic boundary). Such unwarranted combinations commonly arise when inversions of thermochronological data are performed using an a priori scheme that combines data points according to an assumed spatial correlation structure. We find that in nearly all cases where such inversions have been performed, spatial gradients in erosion rates are converted into apparent temporal increases. On

Glaciation and Hydrologic Variability in Tropical South America During the Last 400,000 Years

NASA Astrophysics Data System (ADS)

Fritz, S. C.; Baker, P. A.; Seltzer, G. O.; Ekdahl, E. J.; Ballantyne, A.

2005-12-01

The expansion and contraction of northern continental ice sheets is a fundamental characteristic of the Quaternary. However, the extent of tropical glaciation is poorly constrained, particularly for periods prior to the Last Glacial Maximum (LGM). Similarly, the magnitude and timing of hydrologic variation in tropical South America is not clearly defined over multiple glacial cycles. Thus, the relative roles of global temperature change and insolation control of the South American Summer Monsoon (SASM) are unclear. We have reconstructed the timing of glaciation and precipitation variability in the tropical Andes of South America from drill cores from Lake Titicaca, Bolivia/Peru. The longest core (site LT01-2B, 235 m water depth) is 136 m and consists of four major silt-dominated units with high magnetic susceptibility, low organic carbon concentration, and no carbonate, which are indicative of extensive glacial activity in the cordillera surrounding the lake. These units alternate with laminated low-susceptibility units, with high carbonate and organic carbon concentrations, which reflect times when detrital input from the watershed was low and lake-level was lowered to below the outlet threshold, driving carbonate precipitation. Thus, the stratigraphy suggests that the core spans four major periods of glaciation and the subsequent interstadials. Core chronology is based on radiocarbon in the uppermost 25m, U-series dates on aragonite laminae, and tuning of the calcium carbonate stratigraphy in the lowermost sediments to the Vostok CO2 record. High-resolution (ca. 100 yr) sampling of sediments spanning the last glacial stage shows distinct millennial-scale variability from 20 - 65 kyr BP. This variability is evident in the periodic deposition of turbidites, which are characterized by low biogenic silica concentrations, elevated benthic diatom abundances, heavy carbon isotopic values, high C/N ratios, and an increase in mean grain size - a composite signal

Paleoenvironmental Reconstruction of Late Quaternary Insect Fossils, Halashazi Site, Altai Region, China.

NASA Astrophysics Data System (ADS)

Zhang, Tianshu; Elias, Scott; Angus, Robert

2017-04-01

The Altai region northwest China, is located in the middle of arid central Asia and is therefore sensitive to climate change. However, there is a debate on the heat-moisture pattern (warm-dry pattern or cold-dry pattern) during the early Holocene in the Altai region, and a debate on the dominant atmospheric circulation (westerlies or monsoon) control for central Asian climate changes during the Holocene, and the mechanisms that cause the arid early Holocene in central Asia. Thus, the principal aim of the project is use the MCR method to produce quantified temperature and precipitation estimates, and a high-precision palaeoclimatic record for the Altai region, based on fossil beetle assemblages, to reveal the heat-moisture pattern and its mechanisms. This project will begin to fill in the blank of Quaternary beetle research in China. Using Quaternary beetles to reconstruct palaeoenvironments is a new research method for this region, and has never before been done in China, which will provide new evidence for the palaeoenvironmental study in this area. Furthermore, this project will contribute to the beetle faunal research in Eurasia. The sample site for this project - Halashazi Wetland (048°06'54"N, 088°21'48"E), is located at the crossroad of the Altai Mountains and the Dzungarian Basin, where two ecosystems meet. Thus the fossil beetle assemblages should show dramatic change in response to changes of climate. The sampled deposits are made up entirely of sedge peat. Two different profiles were sampled, with depths of 160 cm and 200 cm, respectively. Both profiles were sampled at 5 cm intervals, with approximately 2 kg of material in each unit. The results of the radiocarbon dating will be available in December 2016. Based on other previous studies, the bottom of the peat sediment is 11,500 cal yr BP, so project focuses on the Holocene period approximately from 10,000 cal yr BP. More than 80 species of Coleoptera from 55 genera, 22 families have been recognised so

Reconciliation of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep sea oxygen isotope records

NASA Astrophysics Data System (ADS)

Chappell, John; Omura, Akio; Esat, Tezer; McCulloch, Malcolm; Pandolfi, John; Ota, Yoko; Pillans, Brad

1996-06-01

A major discrepancy between the Late Quaternary sea level changes derived from raised coral reef terraces at the Huon Peninsula in Papua New Guinea and from oxygen isotopes in deep sea cores is resolved. The two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka (ka = 1000 yr before present), but between 70 and 30 ka the isotopic sea levels are 20-40 m lower than the Huon Peninsula sea levels derived in earlier studies. New, high precision U-series age measurements and revised stratigraphic data for Huon Peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic δ 18O data. Using the sea level and deep sea isotopic data, oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from Greenland ice cores. The record of ice volume changes through the last glacial cycle now appears to be reasonably complete.

Late quaternary history and uranium isotopic compositions of ground water discharge deposits, Crater Flat, Nevada

USGS Publications Warehouse

Paces, James B.; Taylor, Emily M.; Bush, Charles

1993-01-01

Three carbonate-rich spring deposits are present near the southern end of Crater Flat, NV, approximately 18 km southwest of the potential high-level waste repository at Yucca Mountain. We have analyzed five samples of carbonate-rich material from two of the deposits for U and Th isotopic compositions. Resulting U-series disequilibrium ages indicate that springs were active at 18 ?? 1, 30 ?? 3, 45 ?? 4 and >70 ka. These ages are consistent with a crude internal stratigraphy at one site. Identical ages for two samples at two separate sites suggest that springs were contemporaneous, at least in part, and were most likely part of the same hydrodynamic system. In addition, initial U isotopic compositions range from 2.8 to 3.8 and strongly suggest that ground water from the regional Tertiary-volcanic aquifer provided the source for these hydrogenic deposits. This interpretation, along with water level data from near-by wells suggest that the water table rose approximately 80 to 115 m above present levels during the late Quaternary and may have fluctuated repeatedly. Current data are insufficient to allow reconstruction of a detailed depositional history, however geochronological data are in good agreement with other paleoclimatic proxy records preserved throughout the region. Since these deposits are down gradient from the potential repository site, the possibility of higher ground water levels in the future dramatically shortens both vertical and lateral ground water pathways and reduces travel times of transported radionuclides to potential discharge sites.

Reconstructing Southern Greenland Ice Sheet History During the Plio-Pleistocene Intensification of Northern Hemisphere Glaciation: Insights from IODP Site U1307

NASA Astrophysics Data System (ADS)

Blake-Mizen, K. R.; Hatfield, R. G.; Carlson, A. E.; Walczak, M. H.; Stoner, J. S.; Xuan, C.; Lawrence, K. T.; Bailey, I.

2017-12-01

Should it melt entirely, the Greenland Ice Sheet (GrIS) has the potential to raise global sea-level by 7 metres. With the Arctic continuing to warm at a remarkable rate, to better understand how the GrIS will respond to future anthropogenically-induced climate change we must constrain its natural variability in the geological past. In this regard, much uncertainty exists surrounding its pre-Quaternary history; particularly during the mid-Piacenzian warm period (mPWP; 3.3-3.0 Ma) - widely considered an analogue for near-future equilibrium climate with modern atmospheric CO2 levels and elevated temperatures relative to today - and the late Pliocene/early Pleistocene onset of widespread Northern Hemisphere glaciation (NHG, 2.7 Ma). GrIS reconstructions for these intervals have been largely hampered by a lack of well-dated, high-resolution records from suitable sites. To address this, we present new high-resolution, multi-proxy records from IODP Site U1307, a North Atlantic marine sediment core recovered from the Eirik Drift just south of Greenland. Generation of a new high-resolution relative palaeointensity (RPI)-based age-model - representing the first of its kind for high-latitude sediments deposited during NHG - has enabled strong orbital age control. Our ice-rafted debris (IRD) record confirms a 2.72 Ma initiation of major southern GrIS marine-terminating glaciations, which appear to persist even through interglacial periods up to at least 2.24 Ma. XRF-scanning and IRD evidence suggests, however, that an ephemeral ice-cap of likely considerable size persisted on southern Greenland prior to the mPWP. These data, together with the analysed provenance of individual IRD, indicate marine-based GrIS margins extended southward over the NHG interval and only occurred on Greenland's southern tip from 2.7 Ma. Despite a large increase in the deposition of GrIS-derived IRD from this time, bulk sedimentation rates and magnetic grain-size dropped significantly, implying that

Apparent late Quaternary fault slip rate increase in the southwestern Lower Rhine Graben, central Europe

USGS Publications Warehouse

Gold, Ryan D.; Friedrich, Anke M.; Kubler, Simon; Salamon, Martin

2017-01-01

In regions of low strain, long earthquake recurrence intervals (104–106  yrs) and erosive processes limit preservation of Quaternary markers suitable for distinguishing whether faults slip at uniform or secularly varying rates. The Lower Rhine graben in the border region of Germany, The Netherlands, and Belgium provides a unique opportunity to explore Quaternary slip‐rate variations in a region of low strain using the basal (2.29±0.29  Ma) and surface (700±80  ka) contacts of the regionally extensive main terrace (“Hauptterrasse”), deposited by the Rhine and Maas Rivers. These surfaces are vertically offset 3–140 m and 0–68 m, respectively, across individual fault strands within a distributed network of northwest‐trending, slow‐slipping (<0.1  mm/yr) normal faults. In this investigation, we construct Quaternary slip histories for the southern Lower Rhine graben faults using new main terrace surface vertical offset measurements made from light detection and ranging (lidar)‐derived bare‐earth digital terrain models, which we synthesize with existing constraints on the offset basal contact of this fluvial deposit (n=91 collocated sites with displacement constraints). We find that >80% of the sites record an apparent increase in slip rate for the more recent interval from 700 ka to present, which corresponds to a period of increased uplift of the nearby Rhenish Massif and regional volcanism. However, the apparent increase in slip rate could result, in part, from erosion of the footwall surface below the main terrace, leading to an apparent displacement that is smaller than the total vertical offset since the start of the Quaternary. Prior work focused on characterization of these faults as seismic sources in the Lower Rhine graben has preferentially relied on the average fault‐slip rate constrained using the base of the main terrace. We suggest that average fault‐slip rates calculated using the ∼700  ka main terrace

Diploid hybrid origin of Ostryopsis intermedia (Betulaceae) in the Qinghai-Tibet Plateau triggered by Quaternary climate change.

PubMed

Liu, Bingbing; Abbott, Richard J; Lu, Zhiqiang; Tian, Bin; Liu, Jianquan

2014-06-01

Despite the well-known effects that Quaternary climate oscillations had on shaping intraspecific diversity, their role in driving homoploid hybrid speciation is less clear. Here, we examine their importance in the putative homoploid hybrid origin and evolution of Ostryopsis intermedia, a diploid species occurring in the Qinghai-Tibet Plateau (QTP), a biodiversity hotspot. We investigated interspecific relationships between this species and its only other congeners, O. davidiana and O. nobilis, based on four sets of nuclear and chloroplast population genetic data and tested alternative speciation hypotheses. All nuclear data distinguished the three species clearly and supported a close relationship between O. intermedia and the disjunctly distributed O. davidiana. Chloroplast DNA sequence variation identified two tentative lineages, which distinguished O. intermedia from O. davidiana; however, both were present in O. nobilis. Admixture analyses of genetic polymorphisms at 20 SSR loci and sequence variation at 11 nuclear loci and approximate Bayesian computation (ABC) tests supported the hypothesis that O. intermedia originated by homoploid hybrid speciation from O. davidiana and O. nobilis. We further estimated that O. davidiana and O. nobilis diverged 6-11 Ma, while O. intermedia originated 0.5-1.2 Ma when O. davidiana is believed to have migrated southward, contacted and hybridized with O. nobilis possibly during the largest Quaternary glaciation that occurred in this region. Our findings highlight the importance of Quaternary climate change in the QTP in causing hybrid speciation in this important biodiversity hotspot. © 2014 John Wiley & Sons Ltd.

Pleistocene glaciation of the Jackson Hole area, Wyoming

USGS Publications Warehouse

Pierce, Kenneth L.; Licciardi, Joseph M.; Good, John M.; Jaworowski, Cheryl

2018-01-24

Pleistocene glaciations and late Cenozoic offset on the Teton fault have played central roles in shaping the scenic landscapes of the Teton Range and Jackson Hole area in Wyoming. The Teton Range harbored a system of mountain-valley glaciers that produced the striking geomorphic features in these mountains. However, the comparatively much larger southern sector of the Greater Yellowstone glacial system (GYGS) is responsible for creating the more expansive glacial landforms and deposits that dominate Jackson Hole. The glacial history is also inextricably associated with the Yellowstone hotspot, which caused two conditions that have fostered extensive glaciation: (1) uplift and consequent cold temperatures in greater Yellowstone; and (2) the lowland track of the hotspot (eastern Snake River Plain) that funneled moisture to the Yellowstone Plateau and the Yellowstone Crescent of High Terrain (YCHT).The penultimate (Bull Lake) glaciation filled all of Jackson Hole with glacial ice. Granitic boulders on moraines beyond the south end of Jackson Hole have cosmogenic 10Be exposure ages of ~150 thousand years ago (ka) and correlate with Marine Isotope Stage 6. A thick loess mantle subdues the topography of Bull Lake moraines and caps Bull Lake outwash terraces with a reddish buried soil near the base of the loess having a Bk horizon that extends down into the outwash gravel. The Bull Lake glaciation of Jackson Hole extended 48 kilometers (km) farther south than the Pinedale, representing the largest separation of these two glacial positions in the Western United States. The Bull Lake is also more extensive than the Pinedale on the west (22 km) and southwest (23 km) margins of the GYGS but not on the north and east. This pattern is explained by uplift and subsidence on the leading and trailing “bow-wave” of the YCHT, respectively.During the last (Pinedale) glaciation, mountain-valley glaciers of the Teton Range extended to the western edge of Jackson Hole and built

Late Quaternary Palaeoceanographic Changes in Sea Surface Conditions in the Tropical Atlantic

NASA Astrophysics Data System (ADS)

Fischel, Andrea; Seidenkrantz, Marit-Solveig; Kuijpers, Antoon; Nürnberg, Dirk

2013-04-01

between tropical and North Atlantic Ocean variability during the Late Quaternary.

Evidence of long-term seasonal climate forcing in rhizolith isotopes during the last glaciation

USGS Publications Warehouse

Wang, Hongfang; Ambrose, S.H.; Fouke, B.W.

2004-01-01

High density carbonate rhizoliths were found from a loess-paleosol succession from the late Wisconsin period (21-11 ka) in Illinois. Their morphology shows that they formed in a close contact with living and decomposing roots, suggesting a root/microbial respiration origin. Carbon (??13C) and oxygen (??18O) isotopic analyses were performed on 36 and 37 individual rhizoliths of two separate 10 cm intervals and 98 bulk rhizoliths of all 10 cm intervals. The results of the individual rhizolith ??13C and ??18O analyses suggest that the carbon source was largely derived from respiring C3, C4 and microbial biomass, and that meteoric water was controlled mainly by warm-season precipitation. The results of bulk rhizolith ??13C and ??18O analyses show that warm-season proxies varied in phase with glacial fluctuations at submillennial scales, suggesting long-term seasonal forcing may have played an important role on climate change during the late Wisconsin glaciation in North America. Copyright 2004 by the American Geophysical Union.

Late Quaternary sediment-accumulation rates within the inner basins of the California Continental Borderland in support of geologic hazard evaluation

USGS Publications Warehouse

Normark, W.R.; McGann, M.; Sliter, R.W.

2009-01-01

An evaluation of the geologic hazards of the inner California Borderland requires determination of the timing for faulting and mass-movement episodes during the Holocene. Our effort focused on basin slopes and turbidite systems on the basin floors for the area between Santa Barbara and San Diego, California. Dating condensed sections on slopes adjacent to fault zones provides better control on fault history where high-resolution, seismic-reflection data can be used to correlate sediment between the core site and the fault zones. This study reports and interprets 147 radiocarbon dates from 43 U.S. Geological Survey piston cores as well as 11 dates from Ocean Drilling Program Site 1015 on the floor of Santa Monica Basin. One hundred nineteen dates from 39 of the piston cores have not previously been published. Core locations were selected for hazard evaluation, but despite the nonuniform distribution of sample locations, the dates obtained for the late Quaternary deposits are useful for documenting changes in sediment-accumulation rates during the past 30 ka. Cores from basins receiving substantial sediment from rivers, i.e., Santa Monica Basin and the Gulf of Santa Catalina, show a decrease in sediment supply during the middle Holocene, but during the late Holocene after sea level had reached the current highstand condition, rates then increased partly in response to an increase in El Ni??o-Southern Oscillation events during the past 3.5 ka. ?? 2009 The Geological Society of America.

Southeastward increase of the late Quaternary slip-rate of the Xianshuihe fault, eastern Tibet. Geodynamic and seismic hazard implications

NASA Astrophysics Data System (ADS)

Bai, Mingkun; Chevalier, Marie-Luce; Pan, Jiawei; Replumaz, Anne; Leloup, Philippe Hervé; Métois, Marianne; Li, Haibing

2018-03-01

The left-lateral strike-slip Xianshuihe fault system located in the eastern Tibetan Plateau is considered as one of the most tectonically active intra-continental fault system in China, along which more than 20 M > 6.5 and more than 10 M > 7 earthquakes occurred since 1700. Therefore, studying its activity, especially its slip rate at different time scales, is essential to evaluate the regional earthquake hazard. Here, we focus on the central segment of the Xianshuihe fault system, where the Xianshuihe fault near Kangding city splays into three branches: the Selaha, Yalahe and Zheduotang faults. In this paper we use precise dating together with precise field measurements of offsets to re-estimate the slip rate of the fault that was suggested without precise age constraints. We studied three sites where the active Selaha fault cuts and left-laterally offsets moraine crests and levees. We measured horizontal offsets of 96 ± 20 m at Tagong levees (TG), 240 ± 15 m at Selaha moraine (SLH) and 80 ± 5 m at Yangjiagou moraine (YJG). Using 10Be cosmogenic dating, we determined abandonment ages at Tagong, Selaha and Yangjiagou of 12.5 (+ 2.5 / - 2.2) ka, 22 ± 2 ka, and 18 ± 2 ka, respectively. By matching the emplacement age of the moraines or levees with their offsets, we obtain late Quaternary horizontal average slip-rates of 7.6 (+ 2.3 / - 1.9) mm/yr at TG and 10.7 (+ 1.3 / - 1.1) mm/yr at SLH, i.e., 5.7-12 mm/yr or between 9.6 and 9.9 mm/yr assuming that the slip rate should be constant between the nearby TG and SLH sites. At YJG, we obtain a lower slip rate of 4.4 ± 0.5 mm/yr, most likely because the parallel Zheduotang fault shares the slip rate at this longitude, therefore suggesting a ∼5 mm/yr slip rate along the Zheduotang fault. The ∼10 mm/yr late Quaternary rate along the Xianshuihe fault is higher than that along the Ganzi fault to the NW (6-8 mm/yr). This appears to be linked to the existence of the Longriba fault system that separates the Longmenshan

Late quaternary out-of-sequence deformation in the innermost Kangra Reentrant, NW Himalaya of India: Seismic potential appraisal from 10Be dated fluvial terraces

NASA Astrophysics Data System (ADS)

Cortés-Aranda, J.; Vassallo, R.; Jomard, H.; Pousse-Beltrán, L.; Astudillo, L.; Mugnier, J.-L.; Jouanne, F.; Malik, M.; Carcaillet, J.

2018-06-01

The Kangra Reentrant is a convex-to-the-northeast U-shaped structure in the NW Himalaya, where the Sub-Himalayan fold-and-thrust belt is ∼90 km wide. This region has not been struck by large earthquakes since the 1905 Mw 7.8 Kangra Earthquake. Out-of-sequence deformation has been reported at the millennial timescale along intracrustal thrusts within this reentrant, such as the Jawalamukhi Thrust. Up to now, the occurrence of out-of-sequence deformation along inner thrusts within the Kangra Reentrant, during the Late Quaternary, has not yet been addressed. In this study, the results of a neotectonic survey undertaken in this reentrant are presented; the studied zone is located between the Beas and the Neogad rivers, and encompasses from the Jawalamukhi Thrust to the Main Boundary Thrust. Two terraces that are deformed by branches of the Medlicott-Wadia Thrust, locally named the Palampur Thrust, are identified; this is evidenced in the field by metric-scale fault scarps. By using 10Be dating, the ages of these terraces were constrained to ca. 7.5 and ca. 6.2 ka. This is clear evidence of the Late Quaternary out-of-sequence deformation in the innermost part of this reentrant, implying that strain is distributed along all the arc-orthogonal extent of the local fold and thrust belt over this timespan. A cumulative slip rate of ca. 1 mm/yr along the studied thrusts, which represents 10% of the bulk-strain accommodated by the whole reentrant for this timespan, is calculated. In spite of the marginal appearance of this figure, this deformation rate is attributed to 7 < Mw < 8 earthquakes triggered along the brittle/ductile zone of Main Himalayan Thrust and emerging at the surface along crustal ramps, such as those represented by the Palampur Thrust in the study area. Earthquakes of this magnitude may severely impact the Kangra District, which currently hosts 1.5 million people.

Onset and ending of the late Palaeozoic ice age triggered by tectonically paced rock weathering

NASA Astrophysics Data System (ADS)

Goddéris, Yves; Donnadieu, Yannick; Carretier, Sébastien; Aretz, Markus; Dera, Guillaume; Macouin, Mélina; Regard, Vincent

2017-04-01

The onset of the late Palaeozoic ice age about 340 million years ago has been attributed to a decrease in atmospheric CO2 concentrations associated with expansion of land plants, as plants both enhance silicate rock weathering--which consumes CO2--and increase the storage of organic carbon on land. However, plant expansion and carbon uptake substantially predate glaciation. Here we use climate and carbon cycle simulations to investigate the potential effects of the uplift of the equatorial Hercynian mountains and the assembly of Pangaea on the late Palaeozoic carbon cycle. In our simulations, mountain uplift during the Late Carboniferous caused an increase in physical weathering that removed the thick soil cover that had inhibited silicate weathering. The resulting increase in chemical weathering was sufficient to cause atmospheric CO2 concentrations to fall below the levels required to initiate glaciation. During the Permian, the lowering of the mountains led to a re-establishment of thick soils, whilst the assembly of Pangaea promoted arid conditions in continental interiors that were unfavourable for silicate weathering. These changes allowed CO2 concentrations to rise to levels sufficient to terminate the glacial event. Based on our simulations, we suggest that tectonically influenced carbon cycle changes during the late Palaeozoic were sufficient to initiate and terminate the late Palaeozoic ice age.

Simulating the impact of glaciations on continental groundwater flow systems: 2. Model application to the Wisconsinian glaciation over the Canadian landscape

NASA Astrophysics Data System (ADS)

Lemieux, J.-M.; Sudicky, E. A.; Peltier, W. R.; Tarasov, L.

2008-09-01

A 3-D groundwater flow and brine transport numerical model of the entire Canadian landscape up to a depth of 10 km is constructed in order to capture the impacts of the Wisconsinian glaciation on the continental groundwater flow system. The numerical development of the model is presented in the companion paper of Lemieux et al. (2008b). Although the scale of the model prevents the use of a detailed geological model, commonly occurring geological materials that exhibit relatively consistent hydrogeological properties over the continent justify the simplifications while still allowing the capture of large-scale flow system trends. The model includes key processes pertaining to coupled groundwater flow and glaciation modeling, such a density-dependent (i.e., brine) flow, hydromechanical loading, subglacial infiltration, isostasy, and permafrost development. The surface boundary conditions are specified with the results of a glacial system model. The significant impact of the ice sheet on groundwater flow is evident by increases in the hydraulic head values below the ice sheet by as much as 3000 m down to a depth of 1.5 km into the subsurface. Results also indicate that the groundwater flow system after glaciation did not fully revert to its initial condition and that it is still recovering from the glaciation perturbation. This suggests that the current groundwater flow system cannot be interpreted solely on the basis of present-day boundary conditions and it is likely that several thousands of years of additional equilibration time will be necessary for the system to reach a new quasi-steady state. Finally, we find permafrost to have a large impact on the rate of dissipation of high hydraulic heads that build at depth and capturing its accurate distribution is important to explain the current hydraulic head distribution across the Canadian landscape.

Deep-sea ostracode shell chemistry (Mg:Ca ratios) and late Quaternary Arctic Ocean history

USGS Publications Warehouse

Cronin, T. M.; Dwyer, Gary S.; Baker, P.A.; Rodriguez-Lazaro, J.; Briggs, W.M.; ,

1996-01-01

The magnesium:calcium (Mg:Ca) and strontium:calcium (Sr:Ca) ratios were investigated in shells of the benthic ostracode genus Krithe obtained from 64 core-tops from water depths of 73 to 4411 m in the Arctic Ocean and Nordic seas to determine the potential of ostracode shell chemistry for palaeoceanographic study. Shells from the Polar Surface Water (−1 to −1.5°C) had Mg:Ca molar ratios of about 0.006–0.008; shells from Arctic Intermediate Water (+0.3 to +2.0°C) ranged from 0.09 to 0.013. Shells from the abyssal plain and ridges of the Nansen, Amundsen and Makarov basins and the Norwegian and Greenland seas had a wide scatter of Mg:Ca ratios ranging from 0.007 to 0.012 that may signify post-mortem chemical alteration of the shells from Arctic deep-sea environments below about 1000 m water depth. There is a positive correlation (r2 = 0.59) between Mg:Ca ratios and bottom-water temperature in Krithe shells from Arctic and Nordic seas from water depths <900 m. Late Quaternary Krithe Mg:Ca ratios were analysed downcore using material from the Gakkel Ridge (water depths 3047 and 3899 m), the Lomonosov Ridge (water depth 1051 m) and the Amundsen Basin (water depth 4226 m) to test the core-top Mg:Ca temperature calibration. Cores from the Gakkel and Lomonosov ridges display a decrease in Mg:Ca ratios during the interval spanning the last glacial/deglacial transition and the Holocene, perhaps related to a decrease in bottom water temperatures or other changes in benthic environments.

Influence of the Atlantic inflow and Mediterranean outflow currents on late Quaternary sedimentary facies of the Gulf of Cadiz continental margin

USGS Publications Warehouse

Nelson, C.H.; Baraza, J.; Maldonado, A.; Rodero, J.; Escutia, C.; Barber, J.H.

1999-01-01

The late Quaternary pattern of sedimentary facies on the Spanish Gulf of Cadiz continental shelf results from an interaction between a number of controlling factors that are dominated by the Atlantic inflow currents flowing southeastward across the Cadiz shelf toward the Strait of Gibraltar. An inner shelf shoreface sand facies formed by shoaling waves is modified by the inflow currents to form a belt of sand dunes at 10-20 m that extends deeper and obliquely down paleo-valleys as a result of southward down-valley flow. A mid-shelf Holocene mud facies progrades offshore from river mouth sources, but Atlantic inflow currents cause extensive progradation along shelf toward the southeast. Increased inflow current speeds near the Strait of Gibraltar and the strong Mediterranean outflow currents there result in lack of mud deposition and development of a reworked transgressive sand dune facies across the entire southernmost shelf. At the outer shelf edge and underlying the mid-shelf mud and inner shelf sand facies is a late Pleistocene to Holocene transgressive sand sheet formed by the eustatic shoreline advance. The late Quaternary pattern of contourite deposits on the Spanish Gulf of Cadiz continental slope results from an interaction between linear diapiric ridges that are oblique to slope contours and the Mediterranean outflow current flowing northwestward parallel to the slope contours and down valleys between the ridges. Coincident with the northwestward decrease in outflow current speeds from the Strait there is the following northwestward gradation of contourite sediment facies: (1) upper slope sand to silt bed facies, (2) sand dune facies on the upstream mid-slope terrace, (3) large mud wave facies on the lower slope, (4) sediment drift facies banked against the diapiric ridges, and (5) valley facies between the ridges. The southeastern sediment drift facies closest to Gibraltar contains medium-fine sand beds interbedded with mud. The adjacent valley floor

Seismic evidence of Quaternary faulting in the Benton Hills area, southeast Missouri

USGS Publications Warehouse

Palmer, J.R.; Shoemaker, M.; Hoffman, D.; Anderson, N.L.; Vaughn, J.D.; Harrison, R.W.

1997-01-01

Two reflection seismic profiles at English Hill, across the southern edge of the Benton Hills escarpment, southeast Missouri, establish that geologic structures at English Hill are of tectonic origin. The lowland area to the south of the escarpment is relatively undisturbed. The geology at English Hill is structurally complex, and reflection seismic and geologic data indicate extensive and episodic faulting of Paleozoic, Cretaceous, Tertiary, and Quaternary strata. The individual faults have near-vertical fault surfaces with maximum vertical separations on the order of 15 m. They appear to be clustered in north-northeast trending zones that essentially parallel one of the dominant Benton Hills structural trends. These observations suggest that previously mapped Quaternary faults at English Hill are deep-seated and tectonic in origin. This paper documents recent faulting at English Hill and is the first time late Quaternary, surface-rupture faulting has been recognized in the middle Mississippi River Valley region outside of the New Madrid seismic zone. This has important implications for earthquake assessment in the midcontinent.

Late Quaternary Arc-parallel Extension of the Kongur Extensional System (KES), Chinese Pamir

NASA Astrophysics Data System (ADS)

Chen, Jie; Schoenbohm, Lindsay M.; Yuan, Zhaode; Li, Wenqiao; Li, Tao; Owen, Lewis A.; Sobel, Edward R.; Hedrick, Kate

2015-04-01

Active deformation in the Chinese Pamir plateau is dominated by east-west extension along the active Kongur extensional system (KES). The KES lies along the northeastern margin of the Pamir at the western end of the Himalayan-Tibetan orogenic belt, and is part of a regional fault system which accommodates east-west extension in the hanging wall of the active Main Pamir Thrust (MPT). Previous work has shown that the MPT has been active since at least the Late Oligocene and accommodates northward motion of the Pamir salient over the Tarim and Tajik basins. It has been proposed that North-directed thrusting along the Main Pamir thrust has been interpreted to be related to east-west extension in the northern Pamir by either extensional collapse of over-thickened crust, or radial thrusting, or oroclinal bending along the Main Pamir Thrust. Alternatively, the east-west extension is related to northward propagation of the right-slip Karakoram fault. A newer model relates the extension to gravitational collapse of the Pamir into the Tadjik depression. Clearly the precise driver remains poorly understood. To better understand the nature of extension in the Pamir and to test the existing models, late Quaternary slip rate along the KES need to be defined using geomorphic mapping, geodetic surveying, Be-10 surface exposure and depth profile dating to quantify rates of fault slip using multiple landforms as strain markers such as offset outwash terraces, lateral moraines, and landslides at five sites, to identify spatial patterns in deformation rates. The preliminary results show that the overall extension direction is subhorizontal, is oriented E-W, and occurs at a high rate of about 7 mm/yr along the Muji and Qimugan faults to the north and deceased to about 1 mm/yr at Kuzigan to the south near Tashkurgan town, which matches the pattern of GPS data. A regional compilation from this study and existing data shows that recent extension along the KES is arc-parallel extension

Quaternary glacial geomorphosites from the Cantabrian Mountains (northern Iberian Peninsula): the Redes Natural Reservation and Picos de Europa Regional Park

NASA Astrophysics Data System (ADS)

Rodríguez-Rodríguez, Laura; Jiménez-Sánchez, Montserrat; José Domínguez-Cuesta, María

2013-04-01

The Cantabrian Mountains is a mountain range 480 km-long and up to 2,648 m altitude (Torre Cerredo Peak) trending parallel to the Cantabrian Coastline between Pyrenees and the northwest corner of the Iberian Peninsula (~43oN 5oW). This mountain range is an outstanding area to research the climatic patterns across South Europe during the Quaternary glaciations since well-preserved glacial features evidence the occurrence of past mountain glaciations in a climatic environment marked by the transition from a maritime climate (Atlantic) to Mediterranean one across the mountain range. The available studies in the Cantabrian Mountains stand that the regional glacial maximum recorded here is prior to ca 38, and that glaciers were in some locations remarkably retreated by the time of the global Last Glacial Maximum (Jiménez-Sánchez et al., in press; Serrano et al., in press). This study is focused on an area about 800 km2 that includes 36 peaks over 2,000 m (Pico Mampodre; 2,192 m) and partially covers the Redes Natural Reservation and Picos de Europa Regional Park. A geomorphologic database in ArcGIS was produced for this area as a previous step to reconstruct in detail the extent, flow pattern and chronology of the former glaciers (PhD under progress). Here we present a selection of 18 glacial geomorphosites classified according to genetic criteria in sites that show: (i) a nicely preserved moraine sequence recording the transition from glacial to periglacial conditions; (ii) glacial erosion features; (iii) glacial and ice related deposits (like moraines, ice-dammed deposits, erratic boulders or fluvio-glacial deposits); (iv) slope instability related to glacial debuttressing (complex landslides and rock avalanches); and (v) the interaction between the landscape and human activity. The interest of the geomorphosites is supported by its good quality of preservation, allowing its use as a basis to reconstruct the glacial and paraglacial processes in this region during

Subdivision of Glacial Deposits in Southeastern Peru Based on Pedogenic Development and Radiometric Ages

NASA Astrophysics Data System (ADS)

Goodman, Adam Y.; Rodbell, Donald T.; Seltzer, Geoffrey O.; Mark, Bryan G.

2001-07-01

The Cordillera Vilcanota and Quelccaya Ice Cap region of southern Peru (13°30‧-14°00‧S; 70°40‧-71°25‧W) contains a detailed record of late Quaternary glaciation in the tropical Andes. Quantification of soil development on 19 moraine crests and radiocarbon ages are used to reconstruct the glacial history. Secondary iron and clay increase linearly in Quelccaya soils and clay accumulates at a linear rate in Vilcanota soils, which may reflect the semicontinuous addition of eolian dust enriched in secondary iron to all soils. In contrast, logarithmic rates of iron buildup in soils in the Cordillera Vilcanota reflect chemical weathering; high concentrations of secondary iron in Vilcanota tills may mask the role of eolian input to these soils. Soil-age estimates from extrapolation of field and laboratory data suggest that the most extensive late Quaternary glaciation occurred >70,000 yr B.P. This provides one of the first semiquantitative age estimates for maximum ice extent in southern Peru and is supported by a minimum-limiting age of ∼41,520 14C yr B.P. A late glacial readvance culminated ∼16,650 cal yr B.P. in the Cordillera Vilcanota. Following rapid deglaciation of unknown extent, an advance of the Quelccaya Ice Cap occurred between ∼13,090 and 12,800 cal yr B.P., which coincides approximately with the onset of the Younger Dryas cooling in the North Atlantic region. Moraines deposited <394 cal yr B.P. in the Cordillera Vilcanota and <300 cal yr B.P. on the west side of the Quelccaya Ice Cap correlate with Little Ice Age moraines of other regions.

Quaternary fans and terraces in the Khumbu Himal south of Mount Everest: their characteristics, age and formation

USGS Publications Warehouse

Barnard, P.L.; Owen, L.A.; Finkel, R.C.

2006-01-01

Large fans and terraces are frequent in the Khumbu Himal within the high Himalayan valleys south of Mt. Everest. These features are composed of massive matrix- and clast-supported diamicts that were formed from both hyperconcentrated flows and coarse-grained debris flows. Cosmogenic radionuclide (CRN) exposure ages for boulders on fans and terraces indicate that periods of fan and terrace formation occurred at c. 16, c. 12, c. 8, c. 4 and c. 1.5 ka, and are broadly coincident with the timing of glaciation in the region. The dating precision is insufficient to resolve whether the surfaces formed before, during or after the correlated glacial advance. However, the sedimentology, and morphostratigraphic and geomorphological relationships suggest that fan and terrace sedimentation in this part of the Himalaya primarily occurs during glacier retreat and is thus paraglacial in origin. Furthermore, modern glacial-lake outburst floods and their associated deposits are common in the Khumbu Himal as the result of glacial retreat during historical times. We therefore suggest that Late Quaternary and Holocene fan and terrace formation and sediment transfer are probably linked to temporal changes in discharge and sediment load caused by glacier oscillations responding to climate change. The timing of major sedimentation events in this region can be correlated with fans and terraces in other parts of the Himalaya, suggesting that major sedimentation throughout the Himalaya is synchronous and tied to regional climatic oscillations. Bedrock incision rates calculated from strath terrace ages average c. 3.9 mm a−1, suggesting that the overall rate of incision is set by regional uplift.

Quaternary prevention: reviewing the concept.

PubMed

Martins, Carlos; Godycki-Cwirko, Maciek; Heleno, Bruno; Brodersen, John

2018-12-01

According to the Wonca International Dictionary for General/Family Practice Quaternary Prevention is defined as: 'Action taken to identify patient at risk of overmedicalization, to protect him from new medical invasion, and to suggest to him interventions, which are ethically acceptable.' The concept of quaternary prevention was initially proposed by Marc Jamoulle and the targets were mainly patients with illness but without a disease. The purpose of this opinion article is to open the debate around a new possible definition and a new conceptual model of quaternary prevention based on the belief that quaternary prevention should be present in physicians' minds for every intervention they suggest to a patient. The debate around quaternary prevention is vital in the context of contemporary medicine and has expanded worldwide. The human being may suffer harm from medical interventions from conception, during their childhood, during their entire healthy lifetime as well as during a self-limited disease, a chronic disease, or a terminal disease. The current definition of quaternary prevention has limitations because it excludes patients and medical interventions where a quaternary prevention perspective would be needed and useful to protect patients from harm. In this context, a new definition and conceptual model of quaternary prevention is proposed. In this new proposal, quaternary prevention is defined as an 'action taken to protect individuals (persons/patients) from medical interventions that are likely to cause more harm than good.'

Quaternary prevention: reviewing the concept

PubMed Central

Martins, Carlos; Godycki-Cwirko, Maciek; Heleno, Bruno; Brodersen, John

2018-01-01

Abstract Background: According to the Wonca International Dictionary for General/Family Practice Quaternary Prevention is defined as: ‘Action taken to identify patient at risk of overmedicalization, to protect him from new medical invasion, and to suggest to him interventions, which are ethically acceptable.’ The concept of quaternary prevention was initially proposed by Marc Jamoulle and the targets were mainly patients with illness but without a disease. Objectives: The purpose of this opinion article is to open the debate around a new possible definition and a new conceptual model of quaternary prevention based on the belief that quaternary prevention should be present in physicians’ minds for every intervention they suggest to a patient. Discussion: The debate around quaternary prevention is vital in the context of contemporary medicine and has expanded worldwide. The human being may suffer harm from medical interventions from conception, during their childhood, during their entire healthy lifetime as well as during a self-limited disease, a chronic disease, or a terminal disease. The current definition of quaternary prevention has limitations because it excludes patients and medical interventions where a quaternary prevention perspective would be needed and useful to protect patients from harm. In this context, a new definition and conceptual model of quaternary prevention is proposed. Conclusion: In this new proposal, quaternary prevention is defined as an ‘action taken to protect individuals (persons/patients) from medical interventions that are likely to cause more harm than good.’ PMID:29384397

Pollen preservation and Quaternary environmental history in the southeastern United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delcourt, P.A.; Delcourt, H.R.

Reconstructions of Quaternary environmental history based upon modern pollen/vegetation/climate calibrations are more tenable if the factors responsible for variation in pollen assemblages are evaluated. Examination of the state of preservation of Quaternary palynomorphs provides quantitative data concerning the degree of information loss due to alteration of pollen assemblages by syndepositional and post-depositional deterioration. The percentage, concentration, and influx values for total indeterminable pollen are useful criteria in providing an objective and quantitative basis for evaluating the comparability of pollen spectra within and between sites. Supporting data concerning sediment particle-size distribution, organic matter content, and concentration, influx, and taxonomic composition ofmore » both determinable pollen and plant macrofossils aid in reconstructing past depositional environments. The potential is high for deterioration of pollen in sediments from the southeastern United States, although considerable variation is found in both kind and degree of deterioration between lacustrine and alluvial sites of different ages and in different latitudes. Modern analogs are a basis for late Quaternary environmental reconstructions when pollen deterioration has not significantly biased the information content of fossil pollen assemblages.« less

Erosion and deposition on the eastern margin of the Bermuda Rise in the late Quaternary

NASA Astrophysics Data System (ADS)

McCave, I. N.; Hollister, C. D.; Laine, E. P.; Lonsdale, P. F.; Richardson, M. J.

1982-05-01

A near-bottom survey has been made on the Eastward Scarp (32°50'N, 57°30'W) of the Bermuda Rise, which rises 1150 m above the 5500-m deep Sohm Abyssal Plain in the western North Atlantic. The survey reveals evidence of erosion and deposition at present and in the late Quaternary by the deeper levels of the westward flowing Gulf Stream Return Flow. Four distinct regions of increasing bed gradient show increasing sediment smoothing and scour in the transition from plateau to abyssal plain. Bedforms observed are current crescents, crag and tail, triangular ripples, elongate mounds, transverse mud ripples, lineations, and furrows ranging from 10 to 1 m or less in depth, decreasing generally with bed gradient. Measured near-bottom current speeds are up to 20 cm s -1. Temperature structure on the lower, steep, slopes suggests that detachment of bottom mixed layers may occur there. Extensive net erosion appears to be confined to the lower steep slopes of the scarp. Reflection profiles (4 kHz) show that there has been erosion in areas thinly draped with recent sediments and in areas that show development of small scarps. The distribution of subsurface acoustic characteristics of the region corresponds broadly to the areas characterized by bed gradient and distinct sedimentation conditions. Subsurface hyperbolae, possibly caused by buried furrows, show furrow persistence through several tens of metres of deposition. Erosion occurs up to the top of the scarp during episodes of presumed stronger currents, which may correspond with intensified circulation during glacials.

Shifting sources and transport paths for the late Quaternary Escanaba Trough sediment fill (northeast Pacific)

USGS Publications Warehouse

Zuffa, G.G.; De Rosa, R.; Normark, W.R.

1997-01-01

Escanaba Trough, which forms the southernmost part of the axial valley of the actively spreading Gorda Ridge, is filled with several hundred meters of sediment of presumed late Quaternary age. Surficial sediment samples from gravity cores, deeper samples (as much as 390 m) from Site 35 of the Deep Sea Drilling Program (Leg 5), and the acoustic character of the sediment fill observed on seismic-reflection profiles indicate that much of the sediment fill is of turbidite origin. Gross composition and heavy- mineral analyses of sand samples show that two distinct petrofacies comprise the sediment fill. The lower part of the fill was derived primarily from the Klamath River source of northern California while the younger fill, including the surficial sand beds, are from the Columbia River drainage much farther north. The Escanaba Trough sediment provides an opportunity to evaluate concepts for paleogeographic and paleotectonic reconstructions that are based on facies analysis and compositional and textural data for the volcanic components because both intrabasinal and extrabasinal sources are present as well as coeval (neovolcanic) and non coeval (paleovolcanic) sourcre This study of a modern basin shows, that although the sediment sources could be identified, it was useful to have some knowledge of the sediment pathway(s), the effects of diagenesis, and the possible effects of sediment sorting as a result of long transport distances from the source area for some components. Application of these same techniques to ancient deposits without benefit of the additional parameters will face limitations.

Reconstructed glacier geometry and inferred Equilibrium Line Altitude changes during the Late Pleistocene deglaciation in the Retezat Mountains, Southern Carpathians

NASA Astrophysics Data System (ADS)

Madarász, Balázs; Ruszkiczay-Rüdiger, Zsófia; Kern, Zoltán; Urdea, Petru

2016-04-01

Quaternary glaciations had a major imprint on the landscape and topography of the Southern Carpathians. Their transitional position between continental and Mediterranean climate zones arouses special interest concerning the timing and pattern of glaciations in this area. Probably the Retezat Mts hosted the most extended glaciation during the Late Pleistocene within this range. The peak elevations of the study area reach 2500 m asl, and the most extended glaciers descended to 1040 m in the northern and to 1130 m on the southern valleys. Major cirque floors are typically situated at 2000-2100 m asl. Glacial landforms have been mapped in order to reconstruct the past ice bodies and the elevation shifts of the paleo equilibrium line altitudes (ELA) during several deglaciation phases of the Last Glacial Maximum (LGM) and Lateglacial in the Retezat Mts. On the basis of published 10Be exposure age data on the northern valleys of the study area, deglaciation of the Retezat Mts occurred at least in five phases between ~21.0 ka and 13.5 ka [1]. Various methods (THAR, AAR, AABR) have been tested using a GIS tool to estimate the ELA of the reconstructed paleoglaciers [2] and paleo ELAs were calculated for each of the deglaciation phases. Preliminary estimates of regional LGM paleoELA employing the simplest THAR method (with a ratio of 0.5) ranged from ~1670 m during the LGM to ~2210 m for the smallest cirque glacier at 13.5 ka, respectively. The AAR and AABR methods provide somewhat higher ELAs for each phase. The obtained paleoELAs were compared to ELA reconstructions available from other Carpathian ranges and also to the Alps and Dinarides. Our data will contribute to a more accurate ELA distribution during the LGM, which may be indicative of the past state of the climate system (moisture gradient, circulation regimes). Thanks to OTKA PD83610, PD104899; NKM-96/2014, NKM-31/2015; OMAA 90öu17; LP2012-27/2012. References: [1] Ruszkiczay-Rüdiger et al. 2016 Quat. Int. (in

New results on Late Quaternary stratigraphy of Manych depression

NASA Astrophysics Data System (ADS)

Kurbanov, Redzhep; Yanina, Tamara; Borisova, Olga

2017-04-01

Cardium edule, Abra ovata) and Caspian (Didacna cristata) fauna. Above lies layer with clay deposits including shells of Didacna (Didacna hyrcana, D. cristata) which symbolized Hirkanian transgression of the Caspian Sea. Upwards through the precise borderline there is silty-loam deposits with shells of freshwater mollusks genus Viviparus, Valvata, Dreissena, Lymnaea. This kind of shells attests the period of freshwater Burtass lake. Burtass lacustrine deposits are overlayed by continental loam with an abundance of carbonates and visible gypsum nodulars. This layer is covered by aqueous loam with detritus and shell fragments. On the top of the section lies the subaerial origin silty layer. The preliminary scheme of the sequence of paleogeographic events in Pleistocene is complied. The beginning of Late Pleistocene is marked by the penetration of marine water deep within the Manych Depression during the Black Sea interglacial transgression (Karangat Trangression, MIS 5e). The character trait of marine water through this period is relatively high salinity (18-20 ‰), that favors the development of Black Sea mollusks. During the transition to the glacial epoch (MIS 5d-a) the marine waters oh Karangat bay had begun retreated back into the Black Sea basin. In the end of this stage there was a strait called Hirkanian, which had desalted brackish waters (8-10 ‰) of the Caspian sea. The marine epoch in the central part of the Manych depression changed to the durable lacustrine phase of development in the second half of Late Pleistocene (MIS 4-3), Burtass lake existed there. In the beginning of its existence it was flowing through (it so because of the major of fresh- and calmwater mollusks in the base of the layer). During the continental stage there was an active erosion damage of the burtass deposits. Through this period were formed specific landscape forms - extended ridges - which finally formed in the epoch of degradation of the last glaciation and Khvalynian water

Late-Middle Quaternary lithostratigraphy and sedimentation patterns on the Alpha Ridge, central Arctic Ocean: Implications for Arctic climate variability on orbital time scales

NASA Astrophysics Data System (ADS)

Wang, Rujian; Polyak, Leonid; Xiao, Wenshen; Wu, Li; Zhang, Taoliang; Sun, Yechen; Xu, Xiaomei

2018-02-01

We use sediment cores collected by the Chinese National Arctic Research Expeditions from the Alpha Ridge to advance Quaternary stratigraphy and paleoceanographic reconstructions for the Arctic Ocean. Our cores show a good litho/biostratigraphic correlation to sedimentary records developed earlier for the central Arctic Ocean, suggesting a recovered stratigraphic range of ca. 0.6 Ma, suitable for paleoclimatic studies on orbital time scales. This stratigraphy was tested by correlating the stacked Alpha Ridge record of bulk XRF manganese, calcium and zirconium (Mn, Ca, Zr), to global stable-isotope (LR04-δ18O) and sea-level stacks and tuning to orbital parameters. Correlation results corroborate the applicability of presumed climate/sea-level controlled Mn variations in the Arctic Ocean for orbital tuning. This approach enables better understanding of the global and orbital controls on the Arctic climate. Orbital tuning experiments for our records indicate strong eccentricity (100-kyr) and precession (∼20-kyr) controls on the Arctic Ocean, probably implemented via glaciations and sea ice. Provenance proxies like Ca and Zr are shown to be unsuitable as orbital tuning tools, but useful as indicators of glacial/deglacial processes and circulation patterns in the Arctic Ocean. Their variations suggest an overall long-term persistence of the Beaufort Gyre circulation in the Alpha Ridge region. Some glacial intervals, e.g., MIS 6 and 4/3, are predominated by material presumably transported by the Transpolar Drift. These circulation shifts likely indicate major changes in the Arctic climatic regime, which yet need to be investigated. Overall, our results demonstrate applicability of XRF data to paleoclimatic studies of the Arctic Ocean.

Assessment of Late Quaternary strain partitioning in the Afar Triple Junction: Dobe and Hanle grabens, Ethiopia and Djibouti

NASA Astrophysics Data System (ADS)

Polun, S. G.; Stockman, M. B.; Hickcox, K.; Horrell, D.; Tesfaye, S.; Gomez, F. G.

2015-12-01

As the only subaerial exposure of a ridge - ridge - ridge triple junction, the Afar region of Ethiopia and Djibouti offers a rare opportunity to assess strain partitioning within this type of triple junction. Here, the plate boundaries do not link discretely, but rather the East African rift meets the Red Sea and Gulf of Aden rifts in a zone of diffuse normal faulting characterized by a lack of magmatic activity, referred to as the central Afar. An initial assessment of Late Quaternary strain partitioning is based on faulted landforms in the Dobe - Hanle graben system in Ethiopia and Djibouti. These two extensional basins are connected by an imbricated accommodation zone. Several fault scarps occur within terraces formed during the last highstand of Lake Dobe, around 5 ka - they provide a means of calibrating a numerical model of fault scarp degradation. Additional timing constraints will be provided by pending exposure ages. The spreading rates of both grabens are equivalent, however in Dobe graben, extension is partitioned 2:1 between northern, south dipping faults and the southern, north dipping fault. Extension in Hanle graben is primarily focused on the north dipping Hanle fault. On the north margin of Dobe graben, the boundary fault bifurcates, where the basin-bordering fault displays a significantly higher modeled uplift rate than the more distal fault, suggesting a basinward propagation of faulting. On the southern Dobe fault, surveyed fault scarps have ages ranging from 30 - 5 ka with uplift rates of 0.71, 0.47, and 0.68 mm/yr, suggesting no secular variation in slip rates from the late Plestocene through the Holocene. These rates are converted into horizontal stretching estimates, which are compared with regional strain estimated from velocities of relatively sparse GPS data.

Pliocene-Quaternary tectonic evolution of the Gulf of Gökova, southwest Turkey

NASA Astrophysics Data System (ADS)

Tur, Hüseyin; Yaltırak, Cenk; Elitez, İrem; Sarıkavak, Kerim Tuncer

2015-01-01

Evolution of the east-west-trending Gökova Graben structure is related to the north-south extension of the Aegean segment of the Aegean-Anatolian Microplate. The Pliocene-Quaternary successions surrounding the onland portion of the Gökova Graben as well as coeval successions within the marine portion of the graben are cut by at least three families of faults that strike northwest-southeast, east-west and east-northeast-west-southwest. These orientations are inconsistent with a simple north-south extensional regime. Interpretation of seismic reflection profiles, multibeam bathymetry and GPS vectors indicates that the Gökova Graben developed as a lazy-S-shaped graben in the back-arc setting north of the Hellenic Arc. A counterclockwise rotation of the Aegean segment of the Aegean-Anatolian Microplate is the suggested mechanism for this geometry, as subduction zone rolled back occurred during the Pliocene-Quaternary. The Gulf of Gökova is the youngest of a series of basins that developed within this large back-arc system, including the Nisyros, Karpathos, and Kamilonisi basins, collectively named to as the Gökova-Nisyros-Karpathos Graben. It is proposed that this graben experienced a scissor-like opening initiating from the west during the Pliocene and progressing eastward during the Quaternary. Faults that are seemingly un-correlated onland and in the marine areas become remarkably aligned when the Marmaris-Rhodes Block is progressively rotated by 6° counterclockwise relative to the Muğla Block using a pole position located within the Gulf of Gökova. The scissor-like opening of the westernmost regions of the Gökova Graben likely occurred during the late Pliocene, whereas the central and eastern portions of the graben developed during the early-middle Pleistocene and late Pleistocene-Holocene, respectively. The onset of the opening of the westernmost segment of the Gökova-Nisyros-Karpathos Graben occurred at a time earlier than the late Pliocene.

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects

USGS Publications Warehouse

Reynolds, R.L.; Reheis, M.C.; Neff, J.C.; Goldstein, H.; Yount, J.

2006-01-01

in these surficial deposits during the late Quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12-15 ky and because variations in fine-grained (silt) sediment, including eolian dust, influence soil-moisture capacity.

Hydromechanical effects of continental glaciation on groundwater systems

USGS Publications Warehouse

Neuzil, C.E.

2012-01-01

Hydromechanical effects of continental ice sheets may involve considerably more than the widely recognized direct compression of overridden terrains by ice load. Lithospheric flexure, which lags ice advance and retreat, appears capable of causing comparable or greater stress changes. Together, direct and flexural loading may increase fluid pressures by tens of MPa in geologic units unable to drain. If so, fluid pressures in low-permeability formations subject to glaciation may have increased and decreased repeatedly during cycles of Pleistocene glaciation and can again in the future. Being asynchronous and normally oriented, direct and flexural loading presumably cause normal and shear stresses to evolve in a complex fashion through much or all of a glacial cycle. Simulations of fractured rock predict permeability might vary by two to three orders of magnitude under similar stress changes as fractures at different orientations are subjected to changing normal and shear stresses and some become critically stressed. Uncertainties surrounding these processes and their interactions, and the confounding influences of surface hydrologic changes, make it challenging to delineate their effects on groundwater flow and pressure regimes with any specificity. To date, evidence for hydromechanical changes caused by the last glaciation is sparse and inconclusive, comprising a few pressure anomalies attributed to the removal of direct ice load. This may change as more data are gathered, and understanding of relevant processes is refined.

Response of bushy-tailed woodrats (Neotoma cinerea) to late Quaternary climatic change in the Colorado Plateau

USGS Publications Warehouse

Smith, F.A.; Betancourt, J.L.

1998-01-01

Temperature profoundly influences the physiology and life history characteristics of organisms, particularly in terms of body size. Because so many critical parameters scale with body mass, long-term temperature fluctuations can have dramatic impacts. We examined the response of a small mammalian herbivore, the bushy-tailed woodrat (Neotoma cinerea), to temperature change from 20 000 yr BP to present, at five sites within the Colorado Plateau. Our investigations focused on the relationship between temperature, plant composition and abundance, and woodrat size. Body size was estimated by measuring fossil fecal pellets, a technique validated in earlier work. We found significant and highly covariable patterns in body mass over the five locations, suggesting that responses to temperature fluctuations during the late Quaternary have been very similar. Although woodrat mass and the occurrence of several plant species in the fossil record were significantly correlated, in virtually all instances changes in woodrat size preceded changes in vegetational composition. These results may be due to the greater sensitivity of woodrats to temperature, or to the shorter generation times of woodrats as compared to most plants. An alternative hypothesis is that winter temperatures increased before summer ones. Woodrats are highly sensitive to warmer winters, whereas little response would be expected from forest/woodland plants growing at their lower limits. Our work suggests that woodrat size is a precise paleothermometer, yielding information about temperature variation over relatively short-term temporal and regional scales.

A biomarker stable isotope record of late Quaternary climate and organic matter export in Southwestern Taiwan

NASA Astrophysics Data System (ADS)

Chang, Q.; Hren, M. T.; Lin, A. T.; Eley, Y.; Yu, S. W.; Harris, G.

2017-12-01

We present new leaf wax n-alkane hydrogen (δD) and carbon (δ13C) isotopic data from a 36-m-long core from off-shore southwestern Taiwan to evaluate late Quaternary changes in climate and the source of organic matter exported from the landscape. The core (MD178-3291) is located on the flank of the Gaoping Submarine Canyon that connects with the Gaoping river catchment in southwestern Taiwan. The sediment deposition in this core spans the last 26 kyr, providing a unique record of glacial-interglacial changes in organic matter export from the Taiwan orogen. The δD and δ13C both show a shift in isotopic compositions at 15 kyr, that coincides with the shift in planktonic foraminifera δ18O record from the same core as well as the global sea level. We therefore interpret this dominant shift as affected by the global glacial to interglacial transition. Following by this transition and through the interglacial period, both biomarker δD and δ13C data record fluctuations that we suggest result from short timescale changes in the distribution of organic inputs to the offshore site. This change in source is most likely caused by increases in storm and landslide frequency or intensity during warmer intervals. This interpretation is supported by terrestrial records that show an increase in landslides in the Gaoping catchment and evidence for enhanced rainfall intensity and a corresponding increase in the frequency of turbidity currents.

Rangewide glaciation in the Sierra Nevada, California

USGS Publications Warehouse

Moore, James G.; Moring, Barry C.

2013-01-01

The 600-km-long Sierra Nevada underwent extensive Pleistocene glaciation except for its southernmost 100 km. Presently, ∼1700 small glaciers and ice masses near the crest of the range occur above 3250 m in elevation; these covered an area of ∼50 km2 in 1972. Fourteen of the largest glaciers decreased by about one half in area during the period from 1900 to 2004.Rock glaciers, generally glacial ice covered by 1–10 m of rockfall debris, occur in about the same span of the range as ice and permanent snowfields. They are, on average, lower by 200–300 m, apparently because of the insulating layer of rocky rubble that protects their internal ice from the sun’s heat and from wind.The principal Pleistocene glacial stages are the Sherwin (ca. 820 ka), Tahoe (170–130 and ca. 70 ka), Tioga (14–28 ka), and Recess Peak (13 ka). Some 7040 glacial lakes, produced primarily by quarrying from bedrock, were mostly exposed after recession of the Tioga glacial stage. The lakes largely mark the area of primary snow accumulation. Below the lower limit of the lakes, ice flowed downward into river-cut canyons, forming major trunk glaciers within the zone of ablation.The range is in general a westward-tilted block upfaulted on its east side. Therefore, the main late Pleistocene trunk glaciers (Tahoe/Tioga) west of the crest extend 25–60 km, whereas those east of the crest extend only 5–20 km. Because of higher precipitation northward, glacial features such as the toes of existing glaciers and rock glaciers, as well as the late season present-day snowline, all decrease in elevation northward. Likewise, the elevation of the lower limit of glacial lakes, an indication of the zone of snow accumulation during the late Pleistocene, decreases about the same degree. This similarity suggests that the overall climate patterns of the late Pleistocene, though cooler, were similar to those of today. The east slope glaciers show a similar northward depression, but they are ∼500�

Late quaternary evolution of the Orinoco Delta, Venezuela

USGS Publications Warehouse

Warne, A.G.; Guevara, E.H.; Aslan, A.

2002-01-01

The modern Orinoco Delta is the latest of a series of stacked deltas that have infilled the Eastern Venezuelan Basin (EVB) since the Oligocene. During the late Pleistocene sea-level lowstand (20,000 to 16,000 yrs BP), bedrock control points at the position of the present delta apex prevented the river channel from incising as deeply as many other major river systems. Shallow seismic data indicate that the late Pleistocene Orinoco incised into the present continental shelf, where it formed a braided-river complex that transported sediment to a series of shelf-edge deltas. As sea level rose from 16,000 to 9,500 yrs BP, the Orinoco shoreline shifted rapidly landward, causing shallow-marine waves and currents to form a widespread transgressive sand unit. Decelerating sea-level rise and a warmer, wetter climate during the early Holocene (9,500 to 6,000 yrs BP) induced delta development within the relatively quiet-water environment of the EVB embayment. Sea level approached its present stand in the middle Holocene (6,000 to 3,000 yrs BP), and the Orinoco coast prograded, broadening the delta plain and infilling the EVB embayment. Significant quantities of Amazon sediment began to be transported to the Orinoco coast by littoral currents. Continued progradation in the late Holocene caused the constriction at Boca de Serpientes to alter nearshore and shelf hydrodynamics and subdivide the submarine delta into two distinct areas: the Atlantic shelf and the Gulf of Paria. The increased influence of littoral currents along the coast promoted mudcape development. Because most of the water and sediment were transported across the delta plain through the Rio Grande distributary in the southern delta, much of the central and northwestern delta plain became sediment starved, promoting widespread accumulation of peat deposits. Human impacts on the delta are mostly associated with the Volca??n Dam on Can??o Manamo. However, human activities have had relatively little effect on the

Multi-scale curvature for automated identification of glaciated mountain landscapes

NASA Astrophysics Data System (ADS)

Prasicek, Günther; Otto, Jan-Christoph; Montgomery, David R.; Schrott, Lothar

2014-03-01

Erosion by glacial and fluvial processes shapes mountain landscapes in a long-recognized and characteristic way. Upland valleys incised by fluvial processes typically have a V-shaped cross-section with uniform and moderately steep slopes, whereas glacial valleys tend to have a U-shaped profile with a changing slope gradient. We present a novel regional approach to automatically differentiate between fluvial and glacial mountain landscapes based on the relation of multi-scale curvature and drainage area. Sample catchments are delineated and multiple moving window sizes are used to calculate per-cell curvature over a variety of scales ranging from the vicinity of the flow path at the valley bottom to catchment sections fully including valley sides. Single-scale curvature can take similar values for glaciated and non-glaciated catchments but a comparison of multi-scale curvature leads to different results according to the typical cross-sectional shapes. To adapt these differences for automated classification of mountain landscapes into areas with V- and U-shaped valleys, curvature values are correlated with drainage area and a new and simple morphometric parameter, the Difference of Minimum Curvature (DMC), is developed. At three study sites in the western United States the DMC thresholds determined from catchment analysis are used to automatically identify 5 × 5 km quadrats of glaciated and non-glaciated landscapes and the distinctions are validated by field-based geological and geomorphological maps. Our results demonstrate that DMC is a good predictor of glacial imprint, allowing automated delineation of glacially and fluvially incised mountain landscapes.

Multi-scale curvature for automated identification of glaciated mountain landscapes☆

PubMed Central

Prasicek, Günther; Otto, Jan-Christoph; Montgomery, David R.; Schrott, Lothar

2014-01-01

Erosion by glacial and fluvial processes shapes mountain landscapes in a long-recognized and characteristic way. Upland valleys incised by fluvial processes typically have a V-shaped cross-section with uniform and moderately steep slopes, whereas glacial valleys tend to have a U-shaped profile with a changing slope gradient. We present a novel regional approach to automatically differentiate between fluvial and glacial mountain landscapes based on the relation of multi-scale curvature and drainage area. Sample catchments are delineated and multiple moving window sizes are used to calculate per-cell curvature over a variety of scales ranging from the vicinity of the flow path at the valley bottom to catchment sections fully including valley sides. Single-scale curvature can take similar values for glaciated and non-glaciated catchments but a comparison of multi-scale curvature leads to different results according to the typical cross-sectional shapes. To adapt these differences for automated classification of mountain landscapes into areas with V- and U-shaped valleys, curvature values are correlated with drainage area and a new and simple morphometric parameter, the Difference of Minimum Curvature (DMC), is developed. At three study sites in the western United States the DMC thresholds determined from catchment analysis are used to automatically identify 5 × 5 km quadrats of glaciated and non-glaciated landscapes and the distinctions are validated by field-based geological and geomorphological maps. Our results demonstrate that DMC is a good predictor of glacial imprint, allowing automated delineation of glacially and fluvially incised mountain landscapes. PMID:24748703

Modern Climate Analogues of Late-Quaternary Paleoclimates for the Western United States.

NASA Astrophysics Data System (ADS)

Mock, Cary Jeffrey

This study examined spatial variations of modern and late-Quaternary climates for the western United States. Synoptic climatological analyses of the modern record identified the predominate climatic controls that normally produce the principal modes of spatial climatic variability. They also provided a modern standard to assess past climates. Maps of the month-to-month changes in 500 mb heights, sea-level pressure, temperature, and precipitation illustrated how different climatic controls govern the annual cycle of climatic response. The patterns of precipitation ratios, precipitation bar graphs, and the seasonal precipitation maximum provided additional insight into how different climatic controls influence spatial climatic variations. Synoptic-scale patterns from general circulation model (GCM) simulations or from analyses of climatic indices were used as the basis for finding modern climate analogues for 18 ka and 9 ka. Composite anomaly maps of atmospheric circulation, precipitation, and temperature were compared with effective moisture maps compiled from proxy data to infer how the patterns, which were evident from the proxy data, were generated. The analyses of the modern synoptic climatology indicate that smaller-scale climatic controls must be considered along with larger-scale ones in order to explain patterns of spatial climate heterogeneity. Climatic extremes indicate that changes in the spatial patterns of precipitation seasonality are the exception rather than the rule, reflecting the strong influence of smaller-scale controls. Modern climate analogues for both 18 ka and 9 ka clearly depict the dry Northwest/wet Southwest contrast that is suggested by GCM simulations and paleoclimatic evidence. 18 ka analogues also show the importance of smaller-scale climatic controls in explaining spatial climatic variation in the Northwest and northern Great Plains. 9 ka analogues provide climatological explanations for patterns of spatial heterogeneity over several

Late Quaternary climate stability and the origins and future of global grass endemism.

PubMed

Sandel, Brody; Monnet, Anne-Christine; Govaerts, Rafaël; Vorontsova, Maria

2017-01-01

Earth's climate is dynamic, with strong glacial-interglacial cycles through the Late Quaternary. These climate changes have had major consequences for the distributions of species through time, and may have produced historical legacies in modern ecological patterns. Unstable regions are expected to contain few endemic species, many species with strong dispersal abilities, and to be susceptible to the establishment of exotic species from relatively stable regions. We test these hypotheses with a global dataset of grass species distributions. We described global patterns of endemism, variation in the potential for rapid population spread, and exotic establishment in grasses. We then examined relationships of these response variables to a suite of predictor variables describing the mean, seasonality and spatial pattern of current climate and the temperature change velocity from the Last Glacial Maximum to the present. Grass endemism is strongly concentrated in regions with historically stable climates. It also depends on the spatial pattern of current climate, with many endemic species in areas with regionally unusual climates. There was no association between the proportion of annual species (representing potential population spread rates) and climate change velocity. Rather, the proportion of annual species depended very strongly on current temperature. Among relatively stable regions (<10 m year -1 ), increasing velocity decreased the proportion of species that were exotic, but this pattern reversed for higher-velocity regions (>10 m year -1 ). Exotic species were most likely to originate from relatively stable regions with climates similar to those found in their exotic range. Long-term climate stability has important influences on global endemism patterns, largely confirming previous work from other groups. Less well recognized is its role in generating patterns of exotic species establishment. This result provides an important historical context for the

Mountain glaciation and paleoclimate reconstruction in the Picos de Europa (Iberian Peninsula, SW Europe)

NASA Astrophysics Data System (ADS)

Serrano, Enrique; González-Trueba, Juan José; González-García, María

2012-09-01

Geomorphic mapping and stratigraphic analysis of a lake core document the late Quaternary glacial history of the Central and Eastern Massifs of the Picos de Europa, northwestern Spain. The distribution of glacial deposits indicates that at their most advanced positions glaciers occupied 9.1 km2, extended as far as 7 km down-valley and had an estimated equilibrium-line altitude (ELA) ranging between 1666 and 1722 m. Radiocarbon dating of sediment deposited in a lake dammed by moraines of this advance show that the maximum glacial extent was prior to 35,280 ± 440 cal yr BP. This advance was followed by two subsequent but less extensive late Pleistocene advances, recorded by multiple moraines flanking both massifs and sedimentary characteristics in the lake deposits. The last recognized glacial episode is the 19th-century maximum extent of small Little Ice Age glaciers in the highest cirques above 2200 m.

Significance of pre-Quaternary climate change for montane species diversity: insights from Asian salamanders (Salamandridae: Pachytriton).

PubMed

Wu, Yunke; Wang, Yuezhao; Jiang, Ke; Hanken, James

2013-01-01

Despite extensive focus on the genetic legacy of Pleistocene glaciation, impacts of earlier climatic change on biodiversity are poorly understood. Because amphibians are highly sensitive to variations in precipitation and temperature, we use a genus of Chinese montane salamanders (Salamandridae: Pachytriton) to study paleoclimatic change in East Asia, which experienced intensification of its monsoon circulation in the late Miocene associated with subsequent Pliocene warming. Using both nuclear and mitochondrial DNA sequences, we reconstruct the species tree under a coalescent model and demonstrate that all major lineages originated before the Quaternary. Initial speciation within the genus occurred after the summer monsoon entered a stage of substantial intensification. Heavy summer precipitation established temporary water connectivity through overflows between adjacent stream systems, which may facilitate geographic range expansion by aquatic species such as Pachytriton. Species were formed in allopatry likely through vicariant isolation during or after range expansion. To evaluate the influence of Pliocene warming on these cold-adapted salamanders, we construct a novel temperature buffer-zone model, which suggests widespread physiological stress or even extinction during the warming period. A significant deceleration of species accumulation rate is consistent with Pliocene range contraction, which affected P. granulosus and P. archospotus the most because they lack large temperature buffer zones. In contrast, demographic growth occurred in species for which refugia persist. The buffer-zone model reveals the Huangshan Mountain as a potential climatic refugium, which is similar to that found for other East Asian organisms. Our approach can incorporate future climatic data to evaluate the potential impact of ongoing global warming on montane species (particularly amphibians) and to predict possible population declines. Copyright © 2012 Elsevier Inc. All rights

Stable isotopes in yellow-bellied marmot (Marmota flaviventris) fossils reveal environmental stability in the late Quaternary of the Colorado Rocky Mountains

NASA Astrophysics Data System (ADS)

Reynard, Linda M.; Meltzer, David J.; Emslie, Steven D.; Tuross, Noreen

2015-03-01

High elevation plant and animal communities are considered extremely sensitive to environmental change. We investigated an exceptional fossil record of yellow-bellied marmot (Marmota flaviventris) specimens that was recovered from Cement Creek Cave (elev. 2860 m) and ranged in age from radiocarbon background circa 49.8 cal ka BP to ~ 1 cal ka BP. We coupled isotopic and radiocarbon measurements (δ18O, δD, δ15N, δ13C, and 14C) of bone collagen from individually-AMS dated specimens of marmots to assess ecological responses by this species to environmental change over time in a high elevation basin in the Rocky Mountains of southwestern Colorado, USA. We find little change in all four isotope ratios over time, demonstrating considerable environmental stability during periods when the marmots were present. The stable ecology and the apparent persistence of the small mammal community in the cave fauna throughout the late Quaternary are in marked contrast to the changes that occurred in the large mammal community, including local extirpation and extinction, at the end of the Pleistocene.

Late Quaternary sedimentation on the Leidy Creek fan, Nevada-California: Geomorphic responses to climate change

USGS Publications Warehouse

Reheis, M.C.; Slate, J.L.; Throckmorton, C.K.; McGeehin, J.P.; Sarna-Wojcicki, A. M.; Dengler, L.

1996-01-01

Well-dated surface and subsurface deposits in semiarid Fish Lake Valley, Nevada and California, demonstrate that alluvial-fan deposition is strongly associated with the warm dry climate of the last two interglacial intervals, and that fans were stable and (or) incised during the last glaciation. Fan deposition was probably triggered by a change from relatively moist to arid conditions causing a decrease in vegetation cover and increases in flash floods and sediment yield. We think that this scenario applies to most of the other valleys in the southern Basin and Range. Radiocarbon, tephra, and a few thermoluminescence and cosmogenic ages from outcrops throughout Fish Lake Valley and from cores on the Leidy Creek fan yield ages of > 100-50 ka and 11-0 ka for the last two periods of alluvial-fan deposition. Mapping, coring and shallow seismic profiling indicate that these periods were synchronous throughout the valley and on the proximal and distal parts of the fans. From 50 to 11 ka, fan deposition ceased, a soil formed on the older alluvium and the axial drainage became active as runoff and stream competence increased. Slow deposition due to sheet flow or aeolian processes locally continued during this interval, producing cumulic soil profiles. The soil was buried by debris-flow sediment beginning at about 11 ka, coincident with the onset of relatively dry and warm conditions in the region. However, ground-water discharge maintained a large freshwater marsh on the valley floor throughout the Holocene. Pulses of deposition during the Holocene are recorded in the marsh and fan deposits; some pulses coincided with periods of or transitions to warm, dry climate indicated by proxy climate records, whereas others may reflect local disturbances associated with volcanism and fires. Within the marsh deposits, much of the clastic material is probably desert loess. In addition, the deposition of coppice dunes within the fan deposits coincides with two dry periods during the

Congruence between distribution modelling and phylogeographical analyses reveals Quaternary survival of a toadflax species (Linaria elegans) in oceanic climate areas of a mountain ring range.

PubMed

Fernández-Mazuecos, Mario; Vargas, Pablo

2013-06-01

· The role of Quaternary climatic shifts in shaping the distribution of Linaria elegans, an Iberian annual plant, was investigated using species distribution modelling and molecular phylogeographical analyses. Three hypotheses are proposed to explain the Quaternary history of its mountain ring range. · The distribution of L. elegans was modelled using the maximum entropy method and projected to the last interglacial and to the last glacial maximum (LGM) using two different paleoclimatic models: the Community Climate System Model (CCSM) and the Model for Interdisciplinary Research on Climate (MIROC). Two nuclear and three plastid DNA regions were sequenced for 24 populations (119 individuals sampled). Bayesian phylogenetic, phylogeographical, dating and coalescent-based population genetic analyses were conducted. · Molecular analyses indicated the existence of northern and southern glacial refugia and supported two routes of post-glacial recolonization. These results were consistent with the LGM distribution as inferred under the CCSM paleoclimatic model (but not under the MIROC model). Isolation between two major refugia was dated back to the Riss or Mindel glaciations, > 100 kyr before present (bp). · The Atlantic distribution of inferred refugia suggests that the oceanic (buffered)-continental (harsh) gradient may have played a key and previously unrecognized role in determining Quaternary distribution shifts of Mediterranean plants. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Quaternary tectonic evolution of the Pamir-Tian Shan convergence zone, Northwest China

NASA Astrophysics Data System (ADS)

Thompson Jobe, Jessica Ann; Li, Tao; Chen, Jie; Burbank, Douglas W.; Bufe, Aaron

2017-12-01

The Pamir-Tian Shan collision zone in the western Tarim Basin, northwest China, formed from rapid and ongoing convergence in response to the Indo-Eurasian collision. The arid landscape preserves suites of fluvial terraces crossing structures active since the late Neogene that create fault and fold scarps recording Quaternary deformation. Using geologic and geomorphic mapping, differential GPS surveys of deformed terraces, and optically stimulated luminescence dating, we create a synthesis of the active structures that delineate the timing, rate, and migration of Quaternary deformation during ongoing convergence. New deformation rates on eight faults and folds, when combined with previous studies, highlight the spatial and temporal patterns of deformation within the Pamir-Tian Shan convergence zone during the Quaternary. Terraces spanning 130 to 8 ka record deformation rates between 0.1 and 5.6 mm/yr on individual structures. In the westernmost Tarim Basin, where the Pamir and Tian Shan are already juxtaposed, the fastest rates occur on actively deforming structures at the interface of the Pamir-Tian Shan orogens. Farther east, as the separation between the Pamir-Tian Shan orogens increases, the deformation has not been concentrated on a single structure, but rather has been concurrently distributed across a zone of faults and folds in the Kashi-Atushi fold-and-thrust belt and along the NE Pamir margin, where shortening rates vary on individual structures during the Quaternary. Although numerous structures accommodate the shortening and the locus of deformation shifts during the Quaternary, the total shortening across the western Tarim Basin has remained steady and approximately matches the current geodetic rate of 6-9 mm/yr.

Present and past glaciation on Pluto

NASA Astrophysics Data System (ADS)

Howard, Alan D.; Moore, Jeffrey M.; Umurhan, Orkan M.; White, Oliver L.; Anderson, Robert S.; McKinnon, William B.; Spencer, John R.; Schenk, Paul M.; Beyer, Ross A.; Stern, S. Alan; Ennico, Kimberly; Olkin, Cathy B.; Weaver, Harold A.; Young, Leslie A.; New Horizons Science Team

2017-05-01

Modern N2 ice glaciers flow from highlands to the east of the 750 × 1400 km2 lowland of Sputnik Planum [SP] and merge with the ices of similar composition on SP. We explore the possibility that glaciation may be fed by N2 sublimation from SP followed by redeposition on the highlands. The uplands to the northeast, north, and west of SP have been erosionally sculpted into a variety of dissected terrains that feature linear depressions (valleys), locally in dendritic networks. We interpret these dissected terrains to have been carved by N2 glaciers formerly covering the uplands. Depositional glacial landforms (moraines, eskers, outwash) have not been identified, however. N2 glaciation would have a different erosional manifestation because the substrate (porous water ice and CH4-rich mantles) probably has lower density than N2, and also because of the lack of freeze-thaw weathering. If sufficiently thick (1-4 km), N2 glaciers might have experienced basal melting. Past flow of N2 glaciers from the highlands into SP may have detached and transported the prominent mountainous water ice mountains along the western border of SP.

Late to middle Pleistocene Arctic glacial history implied from a sedimentary record from the Northwind Ridge

NASA Astrophysics Data System (ADS)

Liu, Y.; Dong, L.; Shi, X.; Zhu, A.

2017-12-01

Abstract: Sediment core ARC6-C21 collected from the Northwind Ridge, western Arctic Ocean, covers the late to middle Quaternary (Marine Isotope Stages (MIS) 1-11), as estimated by correlation to earlier proposed Arctic Ocean stratigraphies and AMS14C dating of the youngest sediments. Detailed examination of the elemental composition of sediment along with grain size in core ARC6-C21 provides important new information about sedimentary environments and provenance. We use increased contents of coarse debris as an indicator of glacier collapse events at the margins of the western Arctic Ocean, and identify the provenance of these events from geochemical composition. Notably, peaks of MgO and CaO, including large dropstones, presumably track the Laurentide Ice Sheet (LIS) discharge events to the Arctic Ocean. Major LIS inputs occurred during the stratigraphic intervals estimated as MIS 3, intra-MIS 5 and 7 events, MIS 8, and MIS 10. Inputs from the East Siberian Ice Sheet (ESIS) and/or Eurasia Ice Sheet (EIS)are inferred from peaks of SiO2, K2O and Na2O associated with coarse sediment. Major ESIS and/or EIS sedimentary events occurred in the intervals estimated as MIS 2, MIS 4, MIS 6, MIS 8 and MIS 10. Keywords: Sediment core, Pleistocene, western Arctic Ocean, geochemistry, grain size, sediment provenance, glaciations

Micropaleontologic record of Quaternary paleoenvironments in the Central Albemarle Embayment, North Carolina, U.S.A.

USGS Publications Warehouse

Culver, Stephen J.; Farrell, Kathleen M.; Mallinson, David J.; Willard, Debra A.; Horton, Benjamin P.; Riggs, Stanley R.; Thieler, E. Robert; Wehmiller, John F.; Parham, Peter; Snyder, Scott W.; Hillier, Caroline

2011-01-01

To understand the temporal and spatial variation of eustatic sea-level fluctuations, glacio-hydro-isostacy, tectonics, subsidence, geologic environments and sedimentation patterns for the Quaternary of a passive continental margin, a nearly complete stratigraphic record that is fully integrated with a three dimensional chronostratigraphic framework, and paleoenvironmental information are necessary. The Albemarle Embayment, a Cenozoic regional depositional basin in eastern North Carolina located on the southeast Atlantic coast of the USA, is an ideal setting to unravel these dynamic, interrelated processes.Micropaleontological data, coupled with sedimentologic, chronostratigraphic and seismic data provide the bases for detailed interpretations of paleoenvironmental evolution and paleoclimates in the 90. m thick Quaternary record of the Albemarle Embayment. The data presented here come from a transect of cores drilled through a barrier island complex in the central Albemarle Embayment. This area sits in a ramp-like setting between late Pleistocene incised valleys.The data document the episodic infilling of the Albemarle Embayment throughout the Quaternary as a series of transgressive-regressive (T-R) cycles, characterized by inner shelf, midshelf, and shoreface assemblages, that overlie remnants of fluvial to estuarine valley-fill. Barrier island and marginal marine deposits have a low preservation potential. Inner to mid-shelf deposits of the early Pleistocene are overlain by similar middle Pleistocene shelf sediments in the south of the study area but entirely by inner shelf deposits in the north. Late Pleistocene marine sediments are of inner shelf origin and Holocene deposits are marginal marine in nature. Pleistocene marine sediments are incised, particularly in the northern half of the embayment by lowstand paleovalleys, partly filled by fluvial/floodplain deposits and in some cases, overlain by remnants of transgressive estuarine sediments. The shallowing

Quantifying strain partitioning between magmatic and amagmatic portions of the Afar triple junction of Ethiopia and Djibouti through use of contemporary and late Quaternary extension rates

NASA Astrophysics Data System (ADS)

Polun, S. G.; Hickcox, K.; Tesfaye, S.; Gomez, F. G.

2016-12-01

The central Afar rift in Ethiopia and Djibouti is a zone of accommodation between the onshore propagations of the Gulf of Aden and Red Sea oceanic spreading centers forming part of the Afar triple junction that divides the Arabia, Nubia, and Somalia plates. While extension in the onshore magmatic propagators is accommodated through magmatism and associated faulting, extension in the central Afar is accommodated solely by large and small faults. The contributions of these major faults to the overall strain budget can be well characterized, but smaller faults are more difficult to quantify. Sparse GPS data covering the region constrain the total extension budget across the diffuse triple junction zone. Late Quaternary slip rates for major faults in Hanle, Dobe, Guma, and Immino grabens were estimated using the quantitative analysis of faulted landforms. This forms a nearly complete transect from the onshore propagation of the Red Sea rift in Tendaho graben and the onshore propagation of the Gulf of Aden rift at Manda Inakir. Field surveying was accomplished using a combination of electronic distance measurer profiling and low altitude aerial surveying. Age constraints are provided from the Holocene lacustrine history or through terrestrial cosmogenic nuclide (TCN) dating of the faulted geomorphic surface. Along this transect, late Quaternary slip rates of major faults appear to accommodate 25% of the total horizontal stretching rate between the southern margin of Tendaho graben and the Red Sea coast, as determined from published GPS velocities. This constrains the proportion of total extension between Nubia and Arabia that is accommodated through major faulting in the central Afar, compared to the magmatism and associated faulting of the magmatic propagators elsewhere in the triple junction. Along the transect, individual fault slip rates decrease from the southeast to the northwest, suggesting a `Crank-Arm' model may be more applicable to explain the regional

Wetlands and Paleolakes in the Hyperarid Atacama Desert During the Late Quaternary and Their Implications for Early Human Occupation of South America

NASA Astrophysics Data System (ADS)

Pfeiffer, M.; Latorre Hidalgo, C.; Santoro, C.; Gayo, E.; McRostie, V.; Finstad, K. M.; Amundson, R.

2016-12-01

The hyperarid Atacama Desert has long been considered a natural barrier to human dispersal. However, several archaeological sites dating from the late Pleistocene have been recently reported on, and other as yet unpublished evidence is rapidly accumulating. It has been established that these occupations were facilitated by increased fluvial activity and biologically productive riparian ecosystems along the western slope of the Andes, and that the presence of humans disappeared with declines in this water flow. The considerable evidence for regional stream flow suggests that basins and lowlands should have contained lakes or wetlands contemporaneous with the ages of the fluvial activity, but there has been no published data on late Quaternary lakes in the region. Here, we report on our observations that possibly many present day salars (salt covered basins) were fresh water lakes and marshlands during the Central Andean Pluvial Event (CAPE) that occurred during the late Pleistocene and early Holocene. We performed radiocarbon analysis of described stratigraphic profiles on paleo-shorelines or in paleo-lake basins that lie within the Pampa del Tamarugal (PDT) basin. We additionally described gastropods, plant remnants, phytoliths and diatomea, which provide a reliable source for paleoenvironmental facies interpretation. These data indicate that a paleolake existed at the location of the present-day Salar de Bellavista, and that wetlands (and possibly lakes) were present at the Salar de Llamara and Pintados. These past aquatic systems are coeval with the activation of the riparian systems of the PDT reported by previous studies. Furthermore, they would have contributed to a starkly different set of resource constraints for early inhabitants than the inhospitable conditions existing today. Additionally, the presence of these water sources provides guidance in the search for additional evidence of human occupation in the region, and for understanding the geographical

Cornulitids (tubeworms) from the Late Ordovician Hirnantia fauna of Morocco

NASA Astrophysics Data System (ADS)

Gutiérrez-Marco, Juan Carlos; Vinn, Olev

2018-01-01

Two species of cornulitids, Cornulites gondwanensis sp. nov. and C. aff. shallochensis Reed are described from the Hirnantian of Morocco, within an assemblage representative of the Hirnantia brachiopod fauna occurring near the Ordovician South Pole. The dominance of aggregated and solitary free forms could be explained by particular sedimentary environments preceding the Hirnantian glaciation and the latest Ordovician Extinction Event. The diversity of cornulitids in the Late Ordovician of Gondwana and related terranes was relatively low, and less diverse than the cornulitids of Laurentia and Baltica. Hirnantian cornulitids from Morocco do not resemble Late Ordovician cornulitids of Baltica and Laurentia. Moroccan cornulitids seem to be closely allied to some older Gondwanan cornulitids, especially Sardinian ones. They resemble species described from the Late Ordovician and Llandovery of Scotland suggesting a palaeobiogeographic link.

Evaluating the reliability of Late Quaternary landform ages: Integrating 10Be cosmogenic surface exposure dating with U-series dating of pedogenic carbonate on alluvial and fluvial deposits, Sonoran desert, California

NASA Astrophysics Data System (ADS)

Blisniuk, K.; Sharp, W. D.

2015-12-01

To assess the reliability of Quaternary age determinations of alluvial and fluvial deposits across the Sonoran Desert (Coachella Valley and Anza Borrego) in southern California, we applied both 10Be exposure age dating of surface clasts and U-series dating of pedogenic carbonate from subsurface clast-coatings to the same deposits. We consider agreement between dates from the two techniques to indicate reliable age estimates because each technique is subject to distinct assumptions and therefore their systematic uncertainties are largely independent. 10Be exposure dates should yield maximum ages when no correction is made for inheritance and post-depositional erosion is negligible. U-series dating, in contrast, provides minimum dates because pedogenic carbonate forms after deposition. Our results show that: (1) For deposits ca. 70 ka or younger, 10Be and U-series dates were generally concordant. We note, however, that in most cases U-series soil dates exceed 10Be exposure dates that are corrected for inheritance when using 10Be in modern alluvium. This suggests that 10Be concentrations of modern alluvium may exceed the 10Be acquired by late Pleistocene deposits during fluvial transport and hillslope residence (i.e., Pleistocene inherited 10Be). (2) For deposits older than ~70 ka, U-series dates are significantly younger than the 10Be dates. This implies that U-series dates in this region may significantly underestimate the depositional age of older alluvium, probably because of delayed onset of deposition, slow accumulation, or poor preservation of secondary carbonate in response to climatic controls. Thus, whenever possible, multiple dating methods should be applied to obtain reliable ages for late Quaternary deposits.

Coastal tectonics on the eastern margin of the Pacific Rim: Late Quaternary sea-level history and uplift rates, Channel Islands National Park, California, USA

USGS Publications Warehouse

Muhs, Daniel R.; Simmons, Kathleen R.; Schumann, R. Randall; Groves, Lindsey T.; DeVogel, Stephen B.; Minor, Scott A.; Laurel, Deanna

2014-01-01

The Pacific Rim is a region where tectonic processes play a significant role in coastal landscape evolution. Coastal California, on the eastern margin of the Pacific Rm, is very active tectonically and geomorphic expressions of this include uplifted marine terraces. There have been, however, conflicting estimates of the rate of late Quaternary uplift of marine terraces in coastal California, particularly for the orthern Channel Islands. In the present study, the terraces on San Miguel Island and Santa Rosa Island were mapped and new age estimates were generated using uranium-series dating of fossil corals and amino acid geochronology of fossil mollusks. Results indicate that the 2nd terrace on both islands is ~120 ka and the 1st terrace on Santa Rosa Island is ~80 ka. These ages correspond to two global high-sea stands of the Last Interglacial complex, marine isotope stages (MIS) 5.5 and 51, respectively. The age estimates indicate that San Miguel Island and Santa Rosa Island have been tectonically uplifted at rates of 0.12e0.20 m/ka in the late Quaternary, similar to uplift rates inferred from previous studies on neighboring San Cruz Island. The newly estimated uplift rates for the northern Channel Islands are, however, an order of magnitude lower than a recent study that generated uplift rates from an offshore terrace dating to the Last Glacial period. The differences between the estimated uplift rates in the present study and the offshore study are explained by the magnitude of glacial isostatic adjustment (GIA) effects that were not known at the time of the earlier study. Set in the larger context of northeastern Pacific Rim tectonics, Channel Islands uplift rates are higher than those coastal localities on the margin of the East Pacific Rise spreading center, but slightly lower than those of most localities adjacent to the Cascadia subduction zone. The uplift rates reported here for the northern Channel Islands are similar to those reported for most other

Late Wisconsinan glaciation and postglacial relative sea-level change on western Banks Island, Canadian Arctic Archipelago

NASA Astrophysics Data System (ADS)

Lakeman, Thomas R.; England, John H.

2013-07-01

The study revises the maximum extent of the northwest Laurentide Ice Sheet (LIS) in the western Canadian Arctic Archipelago (CAA) during the last glaciation and documents subsequent ice sheet retreat and glacioisostatic adjustments across western Banks Island. New geomorphological mapping and maximum-limiting radiocarbon ages indicate that the northwest LIS inundated western Banks Island after ~ 31 14C ka BP and reached a terminal ice margin west of the present coastline. The onset of deglaciation and the age of the marine limit (22-40 m asl) are unresolved. Ice sheet retreat across western Banks Island was characterized by the withdrawal of a thin, cold-based ice margin that reached the central interior of the island by ~ 14 cal ka BP. The elevation of the marine limit is greater than previously recognized and consistent with greater glacioisostatic crustal unloading by a more expansive LIS. These results complement emerging bathymetric observations from the Arctic Ocean, which indicate glacial erosion during the Last Glacial Maximum (LGM) to depths of up to 450 m.

Modelling the Gaskiers glaciation, the role of the rapid movement of continents during the Ediacaran

NASA Astrophysics Data System (ADS)

Fluteau, Frédéric; Robert, Boris; Le Hir, Guillaume; Dumas, Christophe; Besse, Jean; Greff-Lefftz, Marianne

2017-04-01

The Ediacaran period (635-542 Ma) is a key period in the Earth's history. It is marked by the oxygenation of ocean bottom water, the development of marine fauna, a major negative anomaly in δ13C (Shuram-Wonoka event) and the last glacial event of the Neoproterozoic. Although recorded on several continents, the Gaskiers glaciation is not considered as a global glaciation, unlike the Marinoan ( 635Ma) and Sturtian ( 720Ma) glaciations. The peculiarity of the Gaskiers glaciation lies in the temporal distribution of the glacial sediments. The Gaskiers glaciation has been dated at 583±2 Ma on several cratons but there are also evidences of glaciation prior to and after 583Ma. The aim of the study is to better understand the reasons of heterochrony observed in the glacial deposits during the Ediacaran. The Gaskiers glaciation took place over a period marked by major paleogeographic changes potentially linked to rapid movements of the Earth's rotation axis (i.e. true polar wander) occurring between 620 and 560 Ma. This period was also characterized by the formation of the Gondwana continent and mountain uplift. These events lead to a rapid change of continent's position and the development of huge mountain ranges during the Ediacaran. In this work, we investigated the impact of paleogeographic changes on climate and in particular on the development of ice-sheet. To this end, we simulated the climate at 615Ma, 580 Ma and 565Ma using the atmosphere-ocean coupled model FOAM. We tested different scenarios of CO2 atmospheric partial pressure, due to the lack of constraints, to estimate the sensitivity of Ediacaran climate to this parameter. Finally climate model outputs were used to force the ice-sheet model GRISLI to calculate the ice-sheet extent, and compare to paleoclimate indicators.

Novel Quaternary Quantum Decoder, Multiplexer and Demultiplexer Circuits

NASA Astrophysics Data System (ADS)

Haghparast, Majid; Monfared, Asma Taheri

2017-05-01

Multiple valued logic is a promising approach to reduce the width of the reversible or quantum circuits, moreover, quaternary logic is considered as being a good choice for future quantum computing technology hence it is very suitable for the encoded realization of binary logic functions through its grouping of 2-bits together into quaternary values. The Quaternary decoder, multiplexer, and demultiplexer are essential units of quaternary digital systems. In this paper, we have initially designed a quantum realization of the quaternary decoder circuit using quaternary 1-qudit gates and quaternary Muthukrishnan-Stroud gates. Then we have presented quantum realization of quaternary multiplexer and demultiplexer circuits using the constructed quaternary decoder circuit and quaternary controlled Feynman gates. The suggested circuits in this paper have a lower quantum cost and hardware complexity than the existing designs that are currently used in quaternary digital systems. All the scales applied in this paper are based on Nanometric area.

Weak hydrothermal carbonation of the Ongeluk volcanics: evidence for low CO2 concentrations in seawater and atmosphere during the Paleoproterozoic global glaciation

NASA Astrophysics Data System (ADS)

Shibuya, Takazo; Komiya, Tsuyoshi; Takai, Ken; Maruyama, Shigenori; Russell, Michael J.

2017-12-01

It was previously revealed that the total CO2 concentration in seawater decreased during the Late Archean. In this paper, to assess the secular change of total CO2 concentration in seawater, we focused on the Paleoproterozoic era when the Earth experienced its first recorded global glaciation. The 2.4 Ga Ongeluk Formation outcrops in the Kaapvaal Craton, South Africa. The formation consists mainly of submarine volcanic rocks that have erupted during the global glaciation. The undeformed lavas are mostly carbonate-free but contain rare disseminated calcites. The carbon isotope ratio of the disseminated calcite (δ13Ccc vs. VPDB) ranges from - 31.9 to - 13.2 ‰. The relatively low δ13Ccc values clearly indicate that the carbonation was partially contributed by 13C-depleted CO2 derived from decomposition of organic matter beneath the seafloor. The absence of δ13Ccc higher than - 13.2‰ is consistent with the exceptionally 13C-depleted CO2 in the Ongeluk seawater during glaciation. The results suggest that carbonation occurred during subseafloor hydrothermal circulation just after the eruption of the lavas. Previously, it was reported that the carbonate content in the uppermost subseafloor crust decreased from 3.2 to 2.6 Ga, indicating a decrease in total CO2 concentration in seawater during that time. However, the average CO2 (as carbonate) content in the Ongeluk lavas (< 0.001 wt%) is much lower than those of 2.6 Ga representatives and even of modern equivalents. This finding suggests that the total CO2 concentration in seawater further decreased during the period between 2.6 and 2.4 Ga. Thus, the very low content of carbonate in the Ongeluk lavas is probable evidence for the extremely low CO2 concentration in seawater during the global glaciation. Considering that the carbonate content of the subseafloor crusts also shows a good correlation with independently estimated atmospheric pCO2 levels through the Earth history, it seem highly likely that the low

Emergent Marine Terraces in Cebu Island, Philippines and Their Implications for Relative Sea Level Changes in the Late Quaternary

NASA Astrophysics Data System (ADS)

Ramos, N. T.; Sarmiento, K. J. S.; Maxwell, K. V.; Soberano, O. B.; Dimalanta, C. B.

2017-12-01

The remarkable preservation and extensive distribution of emergent marine terraces in the Philippines allow us to study relative sea level changes and tectonic processes during the Late Quaternary. While higher uplift rates and possible prehistoric coseismic events are recorded by emergent coral reefs facing subduction zones, the central Philippine islands are reported to reflect vertical tectonic stability as they are distant from trenches. To constrain the coastal tectonics of the central Philippine region, we studied emergent sea level indicators along the coasts of northern Cebu Island in Tabuelan, San Remigio, and Bogo City. Upper steps of marine terraces were interpreted from IFSAR-derived DEMs, in which at least two and seven steps were identified along the west (Tabuelan) and east (Bogo) coasts, respectively. In Tabuelan, two extensive terrace steps (TPT) were interpreted with TPT1 at 5-13 m above mean sea level (amsl) and TPT2 at 27-44 m amsl. Five to possibly seven terrace steps (BPT) were delineated in Bogo City with elevations from lowest (BPT1) to highest (BPT7) at BPT1: 4-6 m, BPT2: 12-18 m, BPT3: 27-33 m, BPT4: 39-46 m, BPT5: 59-71 m, BPT6: 80-92 m, and BPT7: 103-108 m amsl. These upper terraces are inferred to be Late Pleistocene in age based on an initial MIS 5e age reported for a 5-m-high terrace in Mactan Island. At some sites, even lower and narrower terrace surfaces were observed, consisting of cemented coral rubble that surround eroded and attached corals. These lower carbonate steps, with elevations ranging from 1 to 3 m amsl, further provide clues on relative sea level changes and long-term tectonic deformation across Cebu Island.

Late Quaternary paleohydrology deduced from new marine sediment cores taken on the proximal Amazon continental margin

NASA Astrophysics Data System (ADS)

Nace, T.; Baker, P. A.; Dwyer, G. S.; Hollander, D. J.; Silva, C. G.

2010-12-01

Throughout the late Quaternary the Amazon Basin has been influenced by abrupt North-South climate forcing and has undergone several large climate variations as recorded in previously reported speleothem records. Despite its importance in the global carbon cycle there are few continuous, high-resolution records of the Amazon Basin that date back to and beyond the last glacial period. In this study, we report the first results of a marine geological expedition to the Amazon continental shelf and fan region. During this expedition we collected eight ~30 meter piston cores along with gravity, box and multicores. At both sites we undertook complementary multibeam and high resolution seismic reflection profiling. Analyses will be presented from two sets of box/gravity/piston cores. One core (32m) is from a high sedimentation site on the northern flank of the main submarine canyon within the Amazon Fan complex at 1700m water depth. The other core (30m) is located on a seamount to the south of the Amazon Fan complex at 3100m water depth. A mixed assemblage of foraminifera is used for 14C dating to obtain an age model and bulk organic geochemistry is analyzed to determine percent organic carbon, C/N ratios, δ13C and δ15N. The cores were continuously measured shipboard for magnetic susceptibility and gamma density using a GEOTEK logger. These findings uncover the contribution of pelagic and terrestrial organic matter, whether the terrigenous carbon is derived from C3 versus C4 vegetation, and whether the marine organic matter is composed of phytoplankton or marine algae.

Quaternary geology of the Rhode Island inner shelf

USGS Publications Warehouse

Needell, S. W.; O'Hara, C. J.; Knebel, H.J.

1983-01-01

Five sedimentary units and three erosional unconformities identified in high-resolution seismic-reflection profiles reveal the stratigraphic framework and Quaternary history of the inner continental shelf south of Narragansett Bay, Rhode Island. Late Tertiary to early Pleistocene rivers eroded the pre-Mesozoic bedrock and the Upper Cretaceous to lower Tertiary coastal plain and continental shelf strata to form a lowland and cuesta having a north-facing escarpment. The lowland and landward flanks of the cuesta were modified by glaciers during Pleistocene time and subsequently were overlain by drift and end moraine deposits of the late Wisconsinan ice advance. During deglaciation, freshwater lakes formed between the retreating ice and end moraines. Prior to sea-level rise, the drift and older deposits were cut by streams flowing south and southwestward toward Block Island Sound. As sea level rose, postglacial valleys were partly filled by fluvial, freshwater-peat, estuarine and salt-marsh deposits. Transgressing seas eroded the sea floor, exposing bedrock and coastal plain outcrops, and deposited marine sediments. ?? 1983.

Geochronology and Equilibrium Line Altitudes of LLGM through Holocene Glaciations from the Tropical Cordillera Huayhuash, Peru

NASA Astrophysics Data System (ADS)

Hall, S. R.; Ramage, J. M.; Rodbell, D. T.; Finkel, R. C.; Smith, J. A.; Mark, B. G.; Farber, D. L.

2006-12-01

Geomorphologic relationships and cosmogenic 10Be ages from the Central Peruvian Andes reveal a rich record of glaciations from at least the late Holocene, Late Glacial, Last Local Glacial Maximum (LLGM), and older more extensive glaciations - dated between 50ka and 440ka in both the Cordillera Blanca, to the north and the Junin Region to the south. The Cordillera Huayhuash (10.3°S, 76.9°W) is located between these two well-studied regions. The spine of the range trends nearly north-south and contains a substantial east-west spur which together can be used to evaluate the spatial variation in paleo-ELAs. The range is thus a key location to study changes in ice extent and equilibrium line altitudes (ELAs) between the LLGM and modern periods. Modern glaciers are confined to altitudes >4800 m and the present (1997) ELA is 4800- 5100m. In order to determine the paleo-ice positions of glaciers in different valleys we have developed a new chronology from cosmogenic 10Be ages of moraine boulder and 14C basal bog core ages. Through field mapping of glacial features, analysis of satellite imagery, digital elevation models (DEMs), and geochronology, we have delineated the ice limits associated with the LLGM, Late Glacial, and Late Holocene advances. Ages in the three valleys we have studied cluster at ~29ka, ~13ka, and ~9ka and overall we have identified surfaces with ages that range from 39.9±1.4ka to 0.2ka±0.05ka. Based on these data, we have mapped the extent of the correlative paleo-glaciers in these three drainages and extracted the modern hypsometry for each paleo-glacier from the DEMs. From this data set, we have generated paleo- ELAs using a range of methods: Toe-to-Headwall-Altitude Ratio (THAR), the Accumulation Area Ratio (AAR), and Accumulation Area Balance Ratio (AABR). For each of the LLGM, Late Glacial and Holocene stages, we have calculated both: (1) the temperature depression assuming no moisture variations, and (2) the potential relative moisture

Late Quaternary history of contourite drifts and variations in Labrador Current flow, Flemish Pass, offshore eastern Canada

NASA Astrophysics Data System (ADS)

Marshall, Nicole R.; Piper, David J. W.; Saint-Ange, Francky; Campbell, D. Calvin

2014-10-01

Contourite drifts of alternating sand and mud, shaped by the Labrador Current, formed during the late Quaternary in Flemish Pass seaward of the Grand Banks of Newfoundland, Canada. The drifts preserve a record of Labrador Current flow variations through the last glacial maximum. A high-resolution seismic profile and a transect of four cores were collected across Beothuk drift on the southeast side of Flemish Pass. Downcore and lateral trends in grain size and sedimentation rate provide evidence that, between 16 and 13 ka, sediment was partitioned across Beothuk drift and the adjacent Flemish Pass floor by a strong current flow but, from 29 to 16 ka, sedimentation was more of a blanketing style, represented by draped reflections interpreted as being due to a weaker current. The data poorly resolve the low sedimentation rates since 13 ka, but the modern Labrador Current in Flemish Pass is the strongest it has been in at least the past 29 ka. Pre-29 ka current flow is interpreted based on reflection architecture in seismic profiles. A prominent drift on the southwestern side of Flemish Pass formed above a mid-Miocene erosion surface, but was buried by a mass-transport deposit after the penultimate glacial maximum and after drift deposition switched to eastern Flemish Pass. These findings illustrate the temporal complexity of drift sedimentation and provide the first detailed proxy for Labrador Current flow since the last glacial maximum.

A stacked Late Quaternary fluvio-periglacial sequence from the Axe valley, southern England with implications for landscape evolution and Palaeolithic archaeology

NASA Astrophysics Data System (ADS)

Brown, A. G.; Basell, L. S.; Toms, P. S.

2015-05-01

The current model of mid-latitude late Quaternary terrace sequences, is that they are uplift-driven but climatically controlled terrace staircases, relating to both regional-scale crustal and tectonic factors, and palaeohydrological variations forced by quasi-cyclic climatic conditions in the 100 K world (post Mid Pleistocene Transition). This model appears to hold for the majority of the river valleys draining into the English Channel which exhibit 8-15 terrace levels over approximately 60-100 m of altitudinal elevation. However, one valley, the Axe, has only one major morphological terrace and has long-been regarded as anomalous. This paper uses both conventional and novel stratigraphical methods (digital granulometry and terrestrial laser scanning) to show that this terrace is a stacked sedimentary sequence of 20-30 m thickness with a quasi-continuous (i.e. with hiatuses) pulsed, record of fluvial and periglacial sedimentation over at least the last 300-400 K yrs as determined principally by OSL dating of the upper two thirds of the sequence. Since uplift has been regional, there is no evidence of anomalous neotectonics, and climatic history must be comparable to the adjacent catchments (both of which have staircase sequences) a catchment-specific mechanism is required. The Axe is the only valley in North West Europe incised entirely into the near-horizontally bedded chert (crypto-crystalline quartz) and sand-rich Lower Cretaceous rocks creating a buried valley. Mapping of the valley slopes has identified many large landslide scars associated with past and present springs. It is proposed that these are thaw-slump scars and represent large hill-slope failures caused by Vauclausian water pressures and hydraulic fracturing of the chert during rapid permafrost melting. A simple 1D model of this thermokarstic process is used to explore this mechanism, and it is proposed that the resultant anomalously high input of chert and sand into the valley during terminations

Late Cenozoic surficial deposits and valley evolution of unglaciated northern New Jersey

USGS Publications Warehouse

Stanford, S.D.

1993-01-01

Multiple alluvial, colluvial, and eolian deposits in unglaciated northern New Jersey, and the eroded bedrock surfaces on which they rest, provide evidence of both long-term valley evolution driven by sustained eustatic baselevel lowering and short-term filling and excavation of valleys during glacial and interglacial climate cycles. The long-term changes occur over durations of 106 years, the short-term features evolve over durations of 104 to 105 years. Direct glacial effects, including blockage of valleys by glacial ice and sediment, and valley gradient reversals induced by crustal depression, are relatively sudden changes that account for several major Pleistocene drainage shifts. After deposition of the Beacon Hill fluvial gravel in the Late Miocene, lowering of sea level, perhaps in response to growth of the Antarctic ice sheet, led to almost complete dissection of the gravel. A suite of alluvial, colluvial, and eolian sediments was deposited in the dissected landscape. The fluvial Bridgeton Formation was deposited in the Raritan lowland, in the Amboy-Trenton lowland, and in the Delaware valley. Following southeastward diversion of the main Bridgeton river, perhaps during Late Pliocene or Early Pleistocene glaciation, northeastward drainage was established on the inactive Bridgeton fluvial plain. About 30 to 45 m of entrenchment followed, forming narrow, incised valleys within which Late Pleistocene deposits rest. This entrenchment may have occurred in response to lowered sea level caused by growth of ice sheets in the northern hemisphere. Under periglacial conditions in the Middle and Late Pleistocene, valleys were partially filled with alluvium and colluvium. During interglacials slopes were stabilized by vegetation and the alluvial and colluvial valley-fill was excavated by gullying, bank erosion, and spring sapping. During Illinoian and late Wisconsinan glaciation, the lower Raritan River was diverted when glacial deposits blocked its valley, and the

Can we apply the 10Be/9Be flux tracer to marine sediments along glaciated margins?

NASA Astrophysics Data System (ADS)

Valletta, R. D.; Willenbring, J. K.; Passchier, S.; Elmi, C.

2016-12-01

Radioactive cosmogenic 10Be normalized to its stable isotope 9Be is proposed as a tracer of continental deposition into the marine basins throughout the Late Cenozoic. Close to glaciated margins, 10Be/9Be may reflect shifts in ice sheet dynamics whereby ice sheet retraction is accompanied by increases in freshwater discharge and terrestrial weathering, which may both increase 10Be and 9Be delivery to the continental shelf. However, this signal is complicated by boundary scavenging during periods of warmth and increased productivity. To disentangle the environmental and biological imprint on the 10Be/9Be isotope record, we sampled extensively characterized marine sedimentary packages offshore the Wilkes Subglacial Basin in an area where East Antarctic Ice Sheet (EAIS) retraction and advance is well-established (IODP U1361A). Combining this existing data with our new measurements creates a uniquely large, multi-proxy dataset for geochemical reconstructions along a glaciated margin. We measured 10Be, 9Be and a suite of bio-reactive transition metals from alternating diatom-rich and diatom-poor clay units 1) adsorbed to authigenic clays and 2) contained within diatom frustules, making this the first dataset of its kind. Diatom-rich clay sediments mark abrupt periods of Pliocene warming and a retracted EAIS. Beryllium co-varies with diatom-rich units: maximum 10Be ( 1.3 x 109 atoms g-1) and 9Be ( 300 ng g-1) peak during warmer intervals. These data mimic patterns observed in the nearby Ross Sea (Yokoyama et al., 2016), suggesting that interglacials are marked along glaciated margins by sudden pulses in Be delivery. By accounting for the Be inventory within diatoms, we have allowed for the exciting pairing of 10Be with 26Al to obtain 1) particle flux and 2) freshwater volume discharged from the EAIS during melting events. These values may offer an approach to constraining changes in two elusive parameters: subglacial erosion and ice sheet melt.

Late Quaternary slip rate determination by CRN dating on the Haiyuan fault, China, and implication for complex geometry fault systems

NASA Astrophysics Data System (ADS)

Matrau, Rémi; Klinger, Yann; Van der Woerd, Jérôme; Liu-Zeng, Jing; Li, Zhanfei; Xu, Xiwei

2017-04-01

Late Quaternary slip rate determination by CRN dating on the Haiyuan fault, China, and implication for complex geometry fault systems Matrau Rémi, Klinger Yann, Van der Woerd Jérôme, Liu-Zeng Jing, Li Zhanfei, Xu Xiwei The Haiyuan fault in Gansu Province, China, is a major left-lateral strike-slip fault forming the northeastern boundary of the Tibetan plateau and accommodating part of the deformation from the India-Asia collision. Geomorphic and geodetic studies of the Haiyuan fault show slip rates ranging from 4 mm/yr to 19 mm/yr from east to west along 500 km of the fault. Such discrepancy could be explained by the complex geometry of the fault system, leading to slip distribution on multiple branches. Combining displacement measurements of alluvial terraces from high-resolution Pléiades images and 10Be - 26Al cosmogenic radionuclides (CRN) dating, we bracket the late Quaternary slip rate along the Hasi Shan fault segment (37°00' N, 104°25' E). At our calibration site, terrace riser offsets for 5 terraces ranging from 6 m to 227 m and CRN ages ranging from 6.5±0.6 kyr to 41±4 kyr - yield geological left-lateral slip rates from 2.0 mm/yr to 4.4 mm/yr. We measured consistent terrace riser offset values along the entire 25 km-long segment, which suggests that some external forcing controls the regional river-terrace emplacement, regardless of each specific catchment. Hence, we extend our slip rate determination to the entire Hasi Shan fault segment to be 4.0±1.0 mm/yr since the last 40 kyr. This rate is consistent with other long-term rates of 4 mm/yr to 5 mm/yr east and west of Hasi Shan - as well as geodetic rates of 4 mm/yr to 6 mm/yr west of Hasi Shan. However, Holocene terraces and moraines offsets have suggested higher rates of 15 to 20 mm/yr further west. Such disparate rates may be explained by slip distribution on multiple branches. In particular, the Zhongwei fault splay in the central part of the Haiyuan fault, with a slip rate of 4-5 mm/yr could

Lateral weathering gradients in glaciated catchments

NASA Astrophysics Data System (ADS)

McGuire, K. J.; Bailey, S. W.; Ross, D. S.; Strahm, B. D.; Schreiber, M. E.

2016-12-01

Mineral dissolution and the distribution of weathering products are fundamental processes that drive development and habitability of the Earth's critical zone; yet, the spatial configuration of these processes in some systems is not well understood. Feedbacks between hydrologic flows and weathering fluxes are necessary to understanding how the critical zone develops. In upland glaciated catchments of the northeastern USA, primary mineral dissolution and the distribution of weathering products are spatially distinct and predictable over short distances. Hillslopes, where shallow soils force lateral hydrologic fluxes through accumulated organic matter, produce downslope gradients in mineral depletion, weathering product accumulation, soil development, and solute chemistry. We propose that linked gradients in hydrologic flow paths, soil depth, and vegetation lead to predictable differences in the location and extent of mineral dissolution in regolith (soil, subsoil, and rock fragments) and bedrock, and that headwater catchments within the upland glaciated northeast show a common architecture across hillslopes as a result. Examples of these patterns and processes will be illustrated using observations from the Hubbard Brook Experimental Forest in New Hampshire where laterally distinct soils with strong morphological and biogeochemical gradients have been documented. Patterns in mineral depletion and product accumulation are essential in predicting how ecosystems will respond to stresses, disturbance, and management.

Glaciations, gradients, and geography: multiple drivers of diversification of bush frogs in the Western Ghats Escarpment

PubMed Central

Menezes, Riya C.; Jayarajan, Aditi; Shanker, Kartik

2016-01-01

The historical processes underlying high diversity in tropical biodiversity hotspots like the Western Ghats of Peninsular India remain poorly understood. We sampled bush frogs on 13 massifs across the Western Ghats Escarpment and examined the relative influence of Quaternary glaciations, ecological gradients and geological processes on the spatial patterns of lineage and clade diversification. The results reveal a large in situ radiation (more than 60 lineages), exhibiting geographical structure and clade-level endemism, with two deeply divergent sister clades, North and South, highlighting the biogeographic significance of an ancient valley, the Palghat Gap. A majority of the bush frog sister lineages were isolated on adjacent massifs, and signatures of range stasis provide support for the dominance of geological processes in allopatric speciation. In situ diversification events within the montane zones (more than 1800 m) of the two highest massifs suggest a role for climate-mediated forest-grassland persistence. Independent transitions along elevational gradients among sub-clades during the Miocene point to diversification along the elevational gradient. The study highlights the evolutionary significance of massifs in the Western Ghats with the high elevations acting as centres of lineage diversification and the low- and mid-elevations of the southern regions, with deeply divergent lineages, serving as museums. PMID:27534957

Glaciations, gradients, and geography: multiple drivers of diversification of bush frogs in the Western Ghats Escarpment.

PubMed

Vijayakumar, S P; Menezes, Riya C; Jayarajan, Aditi; Shanker, Kartik

2016-08-17

The historical processes underlying high diversity in tropical biodiversity hotspots like the Western Ghats of Peninsular India remain poorly understood. We sampled bush frogs on 13 massifs across the Western Ghats Escarpment and examined the relative influence of Quaternary glaciations, ecological gradients and geological processes on the spatial patterns of lineage and clade diversification. The results reveal a large in situ radiation (more than 60 lineages), exhibiting geographical structure and clade-level endemism, with two deeply divergent sister clades, North and South, highlighting the biogeographic significance of an ancient valley, the Palghat Gap. A majority of the bush frog sister lineages were isolated on adjacent massifs, and signatures of range stasis provide support for the dominance of geological processes in allopatric speciation. In situ diversification events within the montane zones (more than 1800 m) of the two highest massifs suggest a role for climate-mediated forest-grassland persistence. Independent transitions along elevational gradients among sub-clades during the Miocene point to diversification along the elevational gradient. The study highlights the evolutionary significance of massifs in the Western Ghats with the high elevations acting as centres of lineage diversification and the low- and mid-elevations of the southern regions, with deeply divergent lineages, serving as museums. © 2016 The Author(s).

Linking Quaternary Climate Changes to Mountain Building in Southeastern Alaska

NASA Astrophysics Data System (ADS)

Dunn, C. A.; Enkelmann, E.; Allen, W. K.; Ridgway, K.

2015-12-01

The Chugach-St. Elias Mountains in southeastern Alaska exhibit extreme topography as a result of the subduction and collision of the Yakutat microplate with the North American plate. Extensive glaciation in the area, coupled with the active tectonics, makes the Chugach-St. Elias Mountains the ideal site to investigate the resulting spatial and temporal variations in exhumation. The St. Elias Mountains have experienced three major climate changes including the start of regional glaciation at ~5.5 Ma, the onset of glaciation in the Northern Hemisphere during the Plio-Pleistocene Transition to colder temperatures at 2.5 Ma, and a change in global climate cyclicity during the mid-Pleistocene Transition from 1.2-0.7 Ma. Our goal is to determine whether these climate changes result in shifts in the rates and patterns of regional exhumation due to the intensification of glacial erosion. We investigate the late Cenozoic sediments from five boreholes that were drilled by IODP Expedition 341 along a transect crossing the Yakutat shelf (offshore Bering glacier) and into the deep-sea Surveyor Fan in the Gulf of Alaska. Magnetostratigraphy and biostratigraphy on these sediments establish an up to 10 Ma depositional history in the boreholes. To study rock exhumation of the sediment source over time, 17 detrital samples from various depths in the cores were dated using zircon fission track thermochronology. Single grain cooling ages range from 302.8 Ma to 0.2 Ma, and contain composite age populations with peaks coinciding with major regional tectonic events providing information on sediment provenance and exhumation. All single grains were also double dated using U-Pb dating to identify and eliminate volcanic grains from the sample. Common U-Pb age populations are 53, 62, 70, and 98 Ma with minor populations of 117, 154, and 170 Ma. These ages are being used to better constrain sediment provenance and reconstruct past glacial catchments.

Genetic structure and demographic inference of the regular sea urchin Sterechinus neumayeri (Meissner, 1900) in the Southern Ocean: The role of the last glaciation.

PubMed

Díaz, Angie; Gérard, Karin; González-Wevar, Claudio; Maturana, Claudia; Féral, Jean-Pierre; David, Bruno; Saucède, Thomas; Poulin, Elie

2018-01-01

One of the most relevant characteristics of the extant Southern Ocean fauna is its resiliency to survive glacial processes of the Quaternary. These climatic events produced catastrophic habitat reductions and forced some marine benthic species to move, adapt or go extinct. The marine benthic species inhabiting the Antarctic upper continental shelf faced the Quaternary glaciations with different strategies that drastically modified population sizes and thus affected the amount and distribution of intraspecific genetic variation. Here we present new genetic information for the most conspicuous regular sea urchin of the Antarctic continental shelf, Sterechinus neumayeri. We studied the patterns of genetic diversity and structure in this broadcast-spawner across three Antarctic regions: Antarctic Peninsula, the Weddell Sea and Adélie Land in East Antarctica. Genetic analyses based on mitochondrial and nuclear markers suggested that S. neumayeri is a single genetic unit around the Antarctic continent. The species is characterized by low levels of genetic diversity and exhibits a typical star-like haplotype genealogy that supports the hypothesis of a single in situ refugium. Based on two mutation rates standardized for this genus, the Bayesian Skyline plot analyses detected a rapid demographic expansion after the Last Glacial Maximum. We propose a scenario of rapid postglacial expansion and recolonization of Antarctic shallow areas from a less ice-impacted refugium where the species survived the LGM. Considering the patterns of genetic diversity and structure recorded in the species, this refugium was probably located in East Antarctica.

Genetic structure and demographic inference of the regular sea urchin Sterechinus neumayeri (Meissner, 1900) in the Southern Ocean: The role of the last glaciation

PubMed Central

Gérard, Karin; González-Wevar, Claudio; Maturana, Claudia; Féral, Jean-Pierre; David, Bruno; Saucède, Thomas; Poulin, Elie

2018-01-01

One of the most relevant characteristics of the extant Southern Ocean fauna is its resiliency to survive glacial processes of the Quaternary. These climatic events produced catastrophic habitat reductions and forced some marine benthic species to move, adapt or go extinct. The marine benthic species inhabiting the Antarctic upper continental shelf faced the Quaternary glaciations with different strategies that drastically modified population sizes and thus affected the amount and distribution of intraspecific genetic variation. Here we present new genetic information for the most conspicuous regular sea urchin of the Antarctic continental shelf, Sterechinus neumayeri. We studied the patterns of genetic diversity and structure in this broadcast-spawner across three Antarctic regions: Antarctic Peninsula, the Weddell Sea and Adélie Land in East Antarctica. Genetic analyses based on mitochondrial and nuclear markers suggested that S. neumayeri is a single genetic unit around the Antarctic continent. The species is characterized by low levels of genetic diversity and exhibits a typical star-like haplotype genealogy that supports the hypothesis of a single in situ refugium. Based on two mutation rates standardized for this genus, the Bayesian Skyline plot analyses detected a rapid demographic expansion after the Last Glacial Maximum. We propose a scenario of rapid postglacial expansion and recolonization of Antarctic shallow areas from a less ice-impacted refugium where the species survived the LGM. Considering the patterns of genetic diversity and structure recorded in the species, this refugium was probably located in East Antarctica. PMID:29874287

Reconstruction and paleoclimatic significance of Late Pleistocene niche glaciation at Mt Aston, Tararua Range, North Island, New Zealand

NASA Astrophysics Data System (ADS)

Brook, Martin

2017-04-01

Evidence for the timing of inter-hemispheric climate fluctuations during the Pleistocene is important, with reconstructed mountain glacier extents routinely used as a proxy for climate. While valley glaciers extended out from an ice sheet centred on New Zealand's Southern Alps during Pleistocene climate cooling to below present-day sea level, evidence of former glacial activity on the North Island of New Zealand is rare, in comparison. A newly-identified glaciated site is Mt Aston, an isolated cirque-like basin within the Tararua Range on New Zealand's North Island. Previously published cosmogenic isotope ages and paleo-glacier reconstructions of a 3 km-long valley glacier 30 km to the north show that paleo-equilibrium line altitudes (ELAs) increased northwards across New Zealand during the regional last glacial maximum (LGM). Hence, at this latitude (41˚ 00' S), only topography >1300 m above present day sea-level was of feasible elevation to intersect the prevailing south-westerly airflow and to allow niche glaciers to form. In the basin below Mt Aston, a c. 0.38 km2 cirque glacier existed with ELA of c. 1290 ± 10 m above present-day sea level. This paleo-ELA closely approximates the extrapolated ELA trend surface for the regional LGM. The mean glacier thickness of 35 m gives a maximum basal shear stress of c. 102 kPa-1, with a mean January temperature at the ELA of c. 5.5 ˚ C. It is well-established that present-day glaciers in New Zealand are particularly sensitive to climate change, manifested by glacial advances and retreats in response to simple mass balance dynamics. Consistent with this, the paleo-glacier reconstruction implies that rather than simple temperature decreases driving paleo-ELA depression, changes in south-westerly airflow over New Zealand, bringing moisture-laden but cool air, maximized snowfall and minimised winter melt. The corollary is that (1) patterns of Pleistocene glacier fluctuations may be interpreted as responses, in-part, to

Constraining fault activity by investigating tectonically-deformed Quaternary palaeoshorelines using a synchronous correlation method: the Capo D'Orlando Fault as a case study (NE Sicily, Italy)

NASA Astrophysics Data System (ADS)

Meschis, Marco; Roberts, Gerald P.; Robertson, Jennifer

2016-04-01

Long-term curstal extension rates, accommodated by active normal faults, can be constrained by investigating Late Quaternary vertical movements. Sequences of marine terraces tectonically deformed by active faults mark the interaction between tectonic activity, sea-level changes and active faulting throughout the Quaternary (e.g. Armijo et al., 1996, Giunta et al, 2011, Roberts et al., 2013). Crustal deformation can be calculated over multiple seismic cycles by mapping Quaternary tectonically-deformed palaeoshorelines, both in the hangingwall and footwall of active normal faults (Roberts et al., 2013). Here we use a synchronous correlation method between palaeoshorelines elevations and the ages of sea-level highstands (see Roberts et al., 2013 for further details) which takes advantage of the facts that (i) sea-level highstands are not evenly-spaced in time, yet must correlate with palaeoshorelines that are commonly not evenly-spaced in elevation, and (ii) that older terraces may be destroyed and/or overprinted by younger highstands, so that the next higher or lower paleoshoreline does not necessarily correlate with the next older or younger sea-level highstand. We investigated a flight of Late Quaternary marine terraces deformed by normal faulting as a result of the Capo D'Orlando Fault in NE Sicily (e.g. Giunta et al., 2011). This fault lies within the Calabrian Arc which has experienced damaging seismic events such as the 1908 Messina Straits earthquake ~ Mw 7. Our mapping and previous mapping (Giunta et al. (2011) demonstrate that the elevations of marine terraces inner edges change along the strike the NE - SW oriented normal fault. This confirms active deformation on the Capo D'Orlando Fault, strongly suggesting that it should be added into the Database of Individual Seismogenic Sources (DISS, Basili et al., 2008). Giunta et al. (2011) suggested that uplift rates and hence faults lip-rates vary through time for this examples. We update the ages assigned to

Comparison of GPS and Quaternary slip rates: Insights from a new Quaternary fault database for Central Asia

NASA Astrophysics Data System (ADS)

Mohadjer, Solmaz; Ehlers, Todd; Bendick, Rebecca; Mutz, Sebastian

2016-04-01

Previous studies related to the kinematics of deformation within the India-Asia collision zone have relied on slip rate data for major active faults to test kinematic models that explain the deformation of the region. The slip rate data, however, are generally disputed for many of the first-order faults in the region (e.g., Altyn Tagh and Karakorum faults). Several studies have also challenged the common assumption that geodetic slip rates are representative of Quaternary slip rates. What has received little attention is the degree to which geodetic slip rates relate to Quaternary slip rates for active faults in the India-Asia collision zone. In this study, we utilize slip rate data from a new Quaternary fault database for Central Asia to determine the overall relationship between Quaternary and GPS-derived slip rates for 18 faults. The preliminary analysis investigating this relationship uses weighted least squares and a re-sampling analysis to test the sensitivity of this relationship to different data point attributes (e.g., faults associated with data points and dating methods used for estimating Quaternary slip rates). The resulting sample subsets of data points yield a maximum possible Pearson correlation coefficient of ~0.6, suggesting moderate correlation between Quaternary and GPS-derived slip rates for some faults (e.g., Kunlun and Longmen Shan faults). Faults with poorly correlated Quaternary and GPS-derived slip rates were identified and dating methods used for the Quaternary slip rates were examined. Results indicate that a poor correlation between Quaternary and GPS-derived slip rates exist for the Karakorum and Chaman faults. Large differences between Quaternary and GPS slip rates for these faults appear to be connected to qualitative dating of landforms used in the estimation of the Quaternary slip rates and errors in the geomorphic and structural reconstruction of offset landforms (e.g., offset terrace riser reconstructions for Altyn Tagh fault

Unravelling Younger Dryas glaciation in the Tweedsmuir Hills, Southern Uplands, Scotland.

NASA Astrophysics Data System (ADS)

Pearce, Danni; Rea, Brice; Barr, Iesytn; Everest, Jeremy; Primmer, Nick; Langdon, Pete; Edwards, Mary; McDougall, Des

2013-04-01

In Britain, the glacial geomorphological record has been widely utilised to infer palaeo-glacier geometries and ice dynamics with much of this work focussing on the Scottish Highlands during the Last Glacial Interglacial Transition (LGIT), in particular the Younger Dryas (YD; c. 12.9 - 11.7 ka BP). The Southern Uplands represents the largest upland area south of the Highlands but have received limited research attention over the last century. The Tweedsmuir Hills are located in the central Southern Uplands, which form an area of dissected plateau approximately 320 km2. Early research in the 1800s identified a range of glacial landforms thought to be associated with the YD. The majority of previous work has focussed on isolated valleys and ignored the potential for plateau icefield glaciation, which has significant implications for understanding of the dynamics and geometries of the YD ice masses. Recent numerical modelling experiments covering the period 38 - 10.4 ka BP (Hubbard et al., 2008 cf. E109B8 and E102b2) have predicted a significant body of ice for the Southern Uplands at the onset of and throughout the YD, which cannot be verified at present due to a lack of empirical data. This research aims to provide the first systematic mapping and climate reconstruction for the Tweedsmuir Hills. The results of air-photo interpretation and field mapping, which utilised a morphostratigraphic approach, has demonstrated a more extensive glaciation than previously mapped. This consists of two separate icefields over the southern and northern Tweedsmuir Hills which cover an area c. 45 km2 and 25 km2 respectively with Equilibrium Line Altitudes (ELAs) calculated to have ranged from c. 419 m to 634 m. For both icefields ELAs of individual outlets reflect topographic controls rather than steep precipitation gradients like those derived for other icefields in Scotland (e.g., the Monadhliath Mountains and Beinn Dearg). New radiocarbon dating of basal stratigraphies and

Glaciomarine sedimentation and bottom current activity on the north-western and northern continental margins of Svalbard during the late Quaternary

NASA Astrophysics Data System (ADS)

Chauhan, Teena; Noormets, Riko; Rasmussen, Tine L.

2016-04-01

Palaeo-bottom current strength of the West Spitsbergen Current (WSC) and the influence of the Svalbard-Barents Sea Ice Sheet (SBIS) on the depositional environment along the northern Svalbard margins are poorly known. Two gravity cores from the southern Yermak Plateau and the upper slope north of Nordaustlandet, covering marine isotope stage (MIS) 1 to MIS 5, are investigated. Five lithofacies, based on grain size distribution, silt/clay ratio, content and mean of sortable silt (SS), are distinguished to characterise the contourite-dominated sedimentary environments. In addition, depositional environments are described using total organic carbon (TOC), total sulphur (TS) and calcium carbonate (CaCO3) contents of sediments. Facies A, containing coarse SS, suggests strong bottom current activity and good bottom water ventilation conditions as inferred from low TOC content. This facies was deposited during the glacial periods MIS 4, MIS 2 and during the late Holocene. Facies B is dominated by fine SS indicating weak bottom current and poor ventilation (cf. high TOC content of 1.2-1.6%), and correlates with the MIS 4/3 and MIS 2/1 transition periods. With an equal amount of clay and sand, fine SS and high content of TOC, facies C indicates reduced bottom current strength for intervals with sediment supply from proximal sources such as icebergs, sea ice or meltwater discharge. This facies was deposited during the last glacial maximum. Facies D represents mass-flow deposits on the northern Svalbard margin attributed to the SBIS advance at or near the shelf edge. Facies E sediments indicating moderate bottom current strength were deposited during MIS 5 and MIS 3, and during parts of MIS 2. This first late Quaternary proxy record of the WSC flow and sedimentation history from the northern Svalbard margin suggests that the oceanographic conditions and ice sheet processes have exerted first-order control on sediment properties.

Radiocarbon dating of individual lignin phenols: a new approach for establishing chronology of late quaternary lake sediments.

PubMed

Hou, Juzhi; Huang, Yongsong; Brodsky, Corynn; Alexandre, Marcelo R; McNichol, Ann P; King, John W; Hu, Feng Sheng; Shen, Ji

2010-09-01

The reliability of chronology is a prerequisite for meaningful paleoclimate reconstructions from sedimentary archives. The conventional approach of radiocarbon dating bulk organic carbon in lake sediments is often hampered by the old carbon effect, i.e., the assimilation of ancient dissolved inorganic carbon (DIC) derived from carbonate bedrocks or other sources. Therefore, radiocarbon dating is ideally performed on organic compounds derived from land plants that use atmospheric CO(2) and rapidly delivered to sediments. We demonstrate that lignin phenols isolated from lake sediments using reversed phase high performance liquid chromatography (HPLC) can serve as effective (14)C dating materials for establishing chronology during the late Quaternary. We developed a procedure to purify lignin phenols, building upon a published method. By isolating lignin from standard wood reference substances, we show that our method yields pure lignin phenols and consistent ages as the consensus ages and that our procedure does not introduce radiocarbon contamination. We further demonstrate that lignin phenol ages are compatible with varve counted and macrofossil dated sediment horizons in Steel Lake and Fayetteville Green Lake. Applying the new method to lake sediment cores from Lake Qinghai demonstrates that lignin phenol ages in Lake Qinghai are consistently younger than bulk total organic carbon (TOC) ages which are contaminated by old carbon effect. We also show that the age offset between lignin and bulk organic carbon differs at different Lake Qinghai sedimentary horizons, suggesting a variable hard water effect at different times and that a uniform age correction throughout the core is inappropriate.

A species-level phylogeny of all extant and late Quaternary extinct mammals using a novel heuristic-hierarchical Bayesian approach.

PubMed

Faurby, Søren; Svenning, Jens-Christian

2015-03-01

Across large clades, two problems are generally encountered in the estimation of species-level phylogenies: (a) the number of taxa involved is generally so high that computation-intensive approaches cannot readily be utilized and (b) even for clades that have received intense study (e.g., mammals), attention has been centered on relatively few selected species, and most taxa must therefore be positioned on the basis of very limited genetic data. Here, we describe a new heuristic-hierarchical Bayesian approach and use it to construct a species-level phylogeny for all extant and late Quaternary extinct mammals. In this approach, species with large quantities of genetic data are placed nearly freely in the mammalian phylogeny according to these data, whereas the placement of species with lower quantities of data is performed with steadily stricter restrictions for decreasing data quantities. The advantages of the proposed method include (a) an improved ability to incorporate phylogenetic uncertainty in downstream analyses based on the resulting phylogeny, (b) a reduced potential for long-branch attraction or other types of errors that place low-data taxa far from their true position, while maintaining minimal restrictions for better-studied taxa, and (c) likely improved placement of low-data taxa due to the use of closer outgroups. Copyright © 2014 Elsevier Inc. All rights reserved.

Changes in Sediment Provenance to the Southeast Newfoundland Ridge from the late Eocene to the Early Oligocene; Northern Hemisphere Glaciation or Deep Water Circulation?

NASA Astrophysics Data System (ADS)

Scher, H. D.; Romans, B.; Moffett, Z. J.; Buckley, W. P.; Gibson, K.

2013-12-01

continents. There is not a long term trend nor prominent inflections in the fossil fish tooth ɛNd record that are associated with terrigenous ɛNd values so it does not appear likely that changes in sediment provenance were accompanied by a reorganization of deep water masses. Thus the preliminary results are cautiously interpreted as reflecting a sedimentological response to an overall increase in weathering/erosion of ancient continental crust, possibly on Greenland, over the investigated interval. In this context these results may reflect the emplacement of northern hemisphere ice sheets in the latest Eocene, preceded by prominent short-lived glacial events in the Eocene. The first short-lived event falls within polarity chron C17n.1n, which corresponds with the timing of a known Eocene glaciation on Antarctica and suggests that the greenhouse climate in the late Eocene supported a bipolar glacial event. We are currently generating a record of relative paleo-bottom current intensity from U1411 using the sortable silt proxy to further evaluate the role of bottom currents in terrigenous sediment provenance on the SENR.

Cosmic Reason of Great Glaciation

NASA Astrophysics Data System (ADS)

Bagrov, Alexander; Murtazov, Andrey

The origin of long-time and global glaciations in the past of our planet, which have been named «great», is still not clear. Both the advance of glaciers and their subsequent melting must be connected with some energy consuming processes. There is a powerful energy source permanently functioning throughout the Earth’s history - the solar radiation. The equality of the incoming shortwave solar energy and the transformed long-wave energy emitted by the Earth provides for the whole ecosphere’s sustainable evolution. Great glaciations might be caused by space body falls into the world oceans. If the body is large enough, it can stir waters down to the bottom. The world waters are part of the global heat transfer from the planet’s equator to its poles (nowadays, mostly to the North Pole). The mixing of the bottom and surface waters breaks the circulation of flows and they stop. The termination of heat transfer to the poles will result in an icecap at high latitudes which in its turn will decrease the total solar heat inflow to the planet and shift the pole ice boarder to the equator. This positive feedback may last long and result in long-time glaciations. The oceanic currents will remain only near the equator. The factor obstructing the global cooling is the greenhouse effect. Volcanic eruptions supply a lot of carbon dioxide into the atmosphere. When due to the increased albedo the planet receives less solar heat, plants bind less carbon oxide into biomass and more of it retains in the atmosphere. Therefore, the outflow of heat from the planet decreases and glaciations does not involve the whole planet. The balance established between the heat inflow and heat losses is unstable. Any imbalance acts as a positive feed-back factor. If the volcanic activity grows, the inflow of the carbon dioxide into the atmosphere will cause its heating-up (plants will fail to reproduce themselves quickly enough to utilize the carbonic acid). The temperature growth will lead to

Uncertainties in the Modelled CO2 Threshold for Antarctic Glaciation

NASA Technical Reports Server (NTRS)

Gasson, E.; Lunt, D. J.; DeConto, R.; Goldner, A.; Heinemann, M.; Huber, M.; LeGrande, A. N.; Pollard, D.; Sagoo, N.; Siddall, M.;

Implications of Climate Change for Glaciated Watersheds in western Canada

NASA Astrophysics Data System (ADS)

Schnorbus, M.; Menounos, B.; Schoeneberg (Werner), A. T.; Anslow, F. S.; Jost, G.; Moore, R. D.

2017-12-01

The cryosphere is particularly vulnerable to changes in climate. For many catchments, glaciers provide water to streams, especially during summer and early autumn when seasonal snow packs have been depleted. Increased concentrations of greenhouse gasses will promote further warming in the decades ahead leading to strong mass loss and a continuation of the rapid retreat of alpine glaciers. Understanding how the contribution of glacier runoff may change in future has important implications for a variety of water resources issues ranging from the impacts of higher water temperatures and lower summer flows on aquatic habitat to the effects of seasonal changes in runoff on hydropower generation. Consequently, there is a need to increase understanding of the influence of glacier storage changes on runoff and streamflow in mountainous watersheds. We developed a modeling system that explicitly simulates ice dynamics, glacier mass balance and runoff. The modelling system employs an upgraded version of the Variable Infiltration Capacity (VIC) hydrology model (which now includes glacier mass balance) coupled to a glacier dynamics model (UBC Regional Glaciation Model) that will be used to assess potential future hydrologic changes in glaciated drainages throughout western Canada. Our presentation will focus on the application of this new model to simulate climate change effects on inflows for several hydropower reservoirs located in heavily glaciated basins in British Columbia, Canada.

Designing Novel Quaternary Quantum Reversible Subtractor Circuits

NASA Astrophysics Data System (ADS)

Haghparast, Majid; Monfared, Asma Taheri

2018-01-01

Reversible logic synthesis is an important area of current research because of its ability to reduce energy dissipation. In recent years, multiple valued logic has received great attention due to its ability to reduce the width of the reversible circuit which is a main requirement in quantum technology. Subtractor circuits are between major components used in quantum computers. In this paper, we will discuss the design of a quaternary quantum reversible half subtractor circuit using quaternary 1-qudit, 2-qudit Muthukrishnan-Stroud and 3-qudit controlled gates and a 2-qudit Generalized quaternary gate. Then a design of a quaternary quantum reversible full subtractor circuit based on the quaternary half subtractor will be presenting. The designs shall then be evaluated in terms of quantum cost, constant input, garbage output, and hardware complexity. The proposed quaternary quantum reversible circuits are the first attempt in the designing of the aforementioned subtractor.

Regional mid-Pleistocene glaciation in central Patagonia

NASA Astrophysics Data System (ADS)

Hein, Andrew S.; Cogez, Antoine; Darvill, Christopher M.; Mendelova, Monika; Kaplan, Michael R.; Herman, Frédéric; Dunai, Tibor J.; Norton, Kevin; Xu, Sheng; Christl, Marcus; Rodés, Ángel

2017-05-01

Southern South America contains a glacial geomorphological record that spans the past million years and has the potential to provide palaeoclimate information for several glacial periods in Earth's history. In central Patagonia, two major outlet glaciers of the former Patagonian Ice Sheet carved deep basins ∼50 km wide and extending over 100 km into the Andean plain east of the mountain front. A succession of nested glacial moraines offers the possibility of determining when the ice lobes advanced and whether such advances occurred synchronously. The existing chronology, which was obtained using different methods in each valley, indicates the penultimate moraines differ in age by a full glacial cycle. Here, we test this hypothesis further using a uniform methodology that combines cosmogenic nuclide ages from moraine boulders, moraine cobbles and outwash cobbles. 10Be concentrations in eighteen outwash cobbles from the Moreno outwash terrace in the Lago Buenos Aires valley yield surface exposure ages of 169-269 ka. We find 10Be inheritance is low and therefore use the oldest surface cobbles to date the deposit at 260-270 ka, which is indistinguishable from the age obtained in the neighbouring Lago Pueyrredón valley. This suggests a regionally significant glaciation during Marine Isotope Stage 8, and broad interhemispheric synchrony of glacial maxima during the mid to late Pleistocene. Finally, we find the dated outwash terrace is 70-100 ka older than the associated moraines. On the basis of geomorphological observations, we suggest this difference can be explained by exhumation of moraine boulders.

Canyon Creek: A late Pleistocene vertebrate locality in interior Alaska

NASA Astrophysics Data System (ADS)

Weber, Florence R.; Hamilton, Thomas D.; Hopkins, David M.; Repenning, Charles A.; Haas, Herbert

1981-09-01

The Canyon Creek vertebrate-fossil locality is an extensive road cut near Fairbanks that exposes sediments that range in age from early Wisconsin to late Holocene. Tanana River gravel at the base of the section evidently formed during the Delta Glaciation of the north-central Alaska Range. Younger layers and lenses of fluvial sand are interbedded with arkosic gravel from Canyon Creek that contains tephra as well as fossil bones of an interstadial fauna about 40,000 years old. Solifluction deposits containing ventifacts, wedge casts, and rodent burrows formed during a subsequent period of periglacial activity that took place during the maximum phase of Donnelly Glaciation about 25,000-17,000 years ago. Overlying sheets of eolian sand are separated by a 9500-year-old paleosol that may correlate with a phase of early Holocene spruce expansion through central Alaska. The Pleistocene fauna from Canyon Creek consists of rodents (indicated by burrows), Mammuthus primigenius (woolly mammoth), Equus lambei (Yukon wild ass), Camelops hesternus (western camel), Bison sp. cf. B. crassicornis (large-horned bison), Ovis sp. cf. O. dalli (mountain sheep), Canis sp. cf. C. lupus (wolf), Lepus sp. cf. L. othus or L. arcticus (tundra hare), and Rangifer sp. (caribou). This assemblage suggests an open landscape in which trees and tall shrubs were either absent or confined to sheltered and moist sites. Camelops evidently was present in eastern Beringia during the middle Wisconsin interstadial interval but may have disappeared during the following glacial episode. The stratigraphic section at Canyon Creek appears to demonstrate that the Delta Glaciation of the north-central Alaska Range is at least in part of early Wisconsin age and was separated from the succeeding Donnelly Glaciation by an interstadial rather than interglacial episode.

Canyon Creek: A late Pleistocene vertebrate locality in interior Alaska

USGS Publications Warehouse

Weber, F.R.; Hamilton, T.D.; Hopkins, D.M.; Repenning, C.A.; Haas, H.

1981-01-01

The Canyon Creek vertebrate-fossil locality is an extensive road cut near Fairbanks that exposes sediments that range in age from early Wisconsin to late Holocene. Tanana River gravel at the base of the section evidently formed during the Delta Glaciation of the north-central Alaska Range. Younger layers and lenses of fluvial sand are interbedded with arkosic gravel from Canyon Creek that contains tephra as well as fossil bones of an interstadial fauna about 40,000 years old. Solifluction deposits containing ventifacts, wedge casts, and rodent burrows formed during a subsequent period of periglacial activity that took place during the maximum phase of Donnelly Glaciation about 25,000-17,000 years ago. Overlying sheets of eolian sand are separated by a 9500-year-old paleosol that may correlate with a phase of early Holocene spruce expansion through central Alaska. The Pleistocene fauna from Canyon Creek consists of rodents (indicated by burrows), Mammuthus primigenius (woolly mammoth), Equus lambei (Yukon wild ass), Camelops hesternus (western camel), Bison sp. cf. B. crassicornis (large-horned bison), Ovis sp. cf. O. dalli (mountain sheep), Canis sp. cf. C. lupus (wolf), Lepus sp. cf. L. othus or L. arcticus (tundra hare), and Rangifer sp. (caribou). This assemblage suggests an open landscape in which trees and tall shrubs were either absent or confined to sheltered and moist sites. Camelops evidently was present in eastern Beringia during the middle Wisconsin interstadial interval but may have disappeared during the following glacial episode. The stratigraphic section at Canyon Creek appears to demonstrate that the Delta Glaciation of the north-central Alaska Range is at least in part of early Wisconsin age and was separated from the succeeding Donnelly Glaciation by an interstadial rather than interglacial episode. ?? 1981.

Tertiary and Quaternary tectonic faulting in southernmost Illinois

USGS Publications Warehouse

Nelson, W.J.; Denny, F.B.; Devera, J.A.; Follmer, L.R.; Masters, J.M.

1997-01-01

Tertiary and/or Quaternary tectonic faulting is documented in three areas of southernmost Illinois: the Fluorspar Area Fault Complex (FAFC) in Pope and Massac Counties, the Ste. Genevieve Fault Zone (SGFZ) in Alexander and Union Counties, and the Commerce Fault Zone (CFZ) in Alexander County. In the FAFC, faults that strike NE and NNE displace Mounds Gravel (late Miocene to early Pleistocene) and, locally, the Metropolis terrace gravel (Pleistocene; pre-Woodfordian). No Woodfordian or younger deposits are deformed. Faults typically outline narrow, linear grabens that formed under tension with a component of strike slip. North-south to NW-trending vertical faults near the southeast end of the SGFZ displace Eocene sediments. Again, faults outline narrow grabens and show indications of strike slip. Deformed Quaternary sediments have not been observed. The CFZ, which trends northeast, displaces Mounds Gravel in Illinois and units as young as Peoria Silt (Woodfordian) in Missouri. Quaternary movement has been interpreted as right-lateral strike-slip. The CFZ coincides with a subtle gravity and magnetic lineament and seems to reflect a major feature in the basement. Surface expression in Illinois is subtle, but mafic and ultramafic intrusions, hydrothermal alteration and small faults align with the Commerce geophysical lineament. Earthquake foci in Missouri and Illinois lie on or close to the CFZ; some focal mechanisms fit the fault trend. Among these structures, only the CFZ exhibits slip that conforms to the current stress field (principal compressive stress axis E-W to ENE-WSW). Possibly, the stress field changed during Neogene time. Alternatively, high fluid pressures or local stress concentrations may have induced slip on less favorably oriented fractures. Tighter constraints are needed on timing, magnitude, and direction of Neogene displacement. ?? 1997 Elsevier Science B.V.

Sensitivity of glaciation in the arid subtropical Andes to changes in temperature, precipitation, and solar radiation

NASA Astrophysics Data System (ADS)

Vargo, L. J.; Galewsky, J.; Rupper, S.; Ward, D. J.

2018-04-01

The subtropical Andes (18.5-27 °S) have been glaciated in the past, but are presently glacier-free. We use idealized model experiments to quantify glacier sensitivity to changes in climate in order to investigate the climatic drivers of past glaciations. We quantify the equilibrium line altitude (ELA) sensitivity (the change in ELA per change in climate) to temperature, precipitation, and shortwave radiation for three distinct climatic regions in the subtropical Andes. We find that in the western cordillera, where conditions are hyper-arid with the highest solar radiation on Earth, ELA sensitivity is as high as 34 m per % increase in precipitation, and 70 m per % decrease in shortwave radiation. This is compared with the eastern cordillera, where precipitation is the highest of the three regions, and ELA sensitivity is only 10 m per % increase in precipitation, and 25 m per % decrease in shortwave radiation. The high ELA sensitivity to shortwave radiation highlights the influence of radiation on mass balance of high elevation and low-latitude glaciers. We also consider these quantified ELA sensitivities in context of previously dated glacial deposits from the regions. Our results suggest that glaciation of the humid eastern cordillera was driven primarily by lower temperatures, while glaciations of the arid Altiplano and western cordillera were also influenced by increases in precipitation and decreases in shortwave radiation. Using paleoclimate records from the timing of glaciation, we find that glaciation of the hyper-arid western cordillera can be explained by precipitation increases of 90-160% (1.9-2.6× higher than modern), in conjunction with associated decreases in shortwave radiation of 7-12% and in temperature of 3.5 °C.

Do cosmogenic nuclides (10Be, 14C , 21Ne, 26Al) track late Quaternary climate changes on the Altiplano?

NASA Astrophysics Data System (ADS)

Hippe, K.; Kober, F.; Zeilinger, G.; Ivy-Ochs, S.; Kubik, P.; Maden, C.; Wieler, R.

2010-12-01

The high Altiplano plateau is the most prominent element of the Central Andes, separating the Andean Cordilleras between 15° to 22° S. It represents a tectonically quiet, intramontane basin with arid to semi-arid climate, low relief and internal drainage. Throughout the late Quaternary regional climate on the Altiplano repeatedly changed between wet and dry conditions [1]. The influence of climate on the plateau evolution during the Pleistocene/Holocene is unclear, however, as data on erosion processes and rates on the Altiplano are sparse. Here, we present a multiple-nuclide study investigating surface denudation at the eastern Altiplano of Bolivia (16°-17° S) on millennial and longer timescales. The aim is a better understanding of the complex feedback between climate, tectonics and geomorphology on the topographic evolution of the Andes. Catchment-wide denudation (CWD) rates are provided for a 150 km NW-SE transect along the Altiplano edge based on the analyses of cosmogenic 10Be, 26Al, 21Ne and in-situ 14C in river-borne sediment. Single nuclide CWD rates obtained for 10Be, 26Al and 21Ne are similar for all three nuclides and on the order of 3-37 mm/ka. Thus, the calculated denudation rates provide an averaged denudation history dating back at least to the middle Pleistocene. Denudation rates correlate positively with the mean basin hillslope, which is mainly controlled by basin lithology. For most catchments both, the 26Al/10Be ratios and the 21Ne/10Be ratios indicate a complex erosion/exposure history with probably several periods of sediment storage and burial/shielding totalling ~0.5 - 1.2 Ma. Local geomorphology featuring low slopes and low relief, small terraces and local floodplains also suggests that sediment transport might have been periodically ineffective. Concentrations of in-situ produced short-lived 14C are significantly lower than expected from the concentrations of the long-lived and stable cosmogenic nuclides. This would indicate a 30

Late Frasnian mass extinction: Conodont event stratigraphy, global changes, and possible causes

NASA Technical Reports Server (NTRS)

Sandberg, Charles A.; Ziegler, Willi; Dreesen, Roland; Butler, Jamie L.

1988-01-01

Several abrupt changes in conodont biofacies are documented to occur synchronously at six primary control sections across the Frasnian-Famennian boundary in Euramerica. These changes occurred within a time-span of only about 100,000 years near the end of the latest Frasnian linguiformis Zone, which is formally named to replace the Uppermost gigas Zone. The conodont-biofacies changes are interpreted to reflect a eustatic rise followed by an abrupt eustatic fall immediately preceding the late Frasnian mass extinction. Two new conodont species are named and described. Ancyrognathus ubiquitus n.sp. is recorded only just below and above the level of late Frasnian extinction and hence is a global marker for that event. Palmatolepispraetriangularis n.sp. is the long-sought Frasnian ancestor of the formerly cryptogenic species, Pa. triangularis, indicator of the earliest Famennian Lower triangularis Zone. The actual extinction event occurred entirely within the Frasnian and is interpreted to have been of brief duration-from as long as 20,000 years to as short as several days. The eustatic rise-and-fall couplet associated with the late Frasnian mass extinction is similar to eustatic couplets associated with the demise of most Frasnian (F2h) reefs worldwide about 1 m.y. earlier and with a latest Famennian mass extinction about 9.5 m.y. later. All these events may be directly or indirectly attributable to extraterrestrial triggering mechanisms. An impact of a small bolide or a near miss of a larger bolide may have caused the earlier demise of Frasnian reefs. An impact of possibly the same larger bolide in the Southern Hemisphere would explain the late Frasnian mass extinction. Global regression during the Famennian probably resulted from Southern-Hemisphere glaciation triggered by the latest Frasnian impact. Glaciation probably was the indirect cause of the latest Famennian mass extinction.

Quaternary Geochronology, Paleontology, and Archaeology of the Upper San Pedro River Valley, Sonora, Mexico

NASA Astrophysics Data System (ADS)

Gaines, E. P.

2013-12-01

This poster presents the results of multi-disciplinary investigations of the preservation and extent of Quaternary fossil-bearing strata in the San Pedro River Valley in Sonora, Mexico. Geologic deposits in the portions of the San Pedro Valley in southern Arizona contain one of the best late Cenozoic fossil records known in North America and the best record of early humans and extinct mammals on the continent. The basin in the U.S. is one of the type locations for the Blancan Land Mammal Age. Hemiphilian and Irvingtonian fossils are common. Rancholabrean remains are widespread. Strata in the valley adjacent to the international border with Mexico have yielded the densest concentration of archaeological mammoth-kill sites known in the western hemisphere. Despite more than 60 years of research in the U.S., however, and the fact that over one third of the San Pedro River lies south of the international boundary, little has been known about the late Cenozoic geology of the valley in Mexico. The study reported here utilized extensive field survey, archaeological documentation, paleontological excavations, stratigraphic mapping and alluvial geochronology to determine the nature and extent of Quaternary fossil-bearing deposits in the portions of the San Pedro Valley in Sonora, Mexico. The results demonstrate that the Plio-Pleistocene fossil -bearing formations known from the valley in Arizona extend into the uppermost reaches of the valley in Mexico. Several new fossil sites were discovered that yielded the remains of Camelids, Equus, Mammuthus, and other Proboscidean species. Late Pleistocene archaeological remains were found on the surface of the surrounding uplands. AMS radiocarbon dating demonstrates the widespread preservation of middle- to late- Holocene deposits. However, the late Pleistocene deposits that contain the archaeological mammoth-kill sites in Arizona are absent in the valley in Mexico, and are now known to be restricted to relatively small portions of

Late-Quaternary recharge determined from chloride in shallow groundwater in the central Great Plains

USGS Publications Warehouse

Macfarlane, P.A.; Clark, J.F.; Davisson, M.L.; Hudson, G.B.; Whittemore, Donald O.

2000-01-01

An extensive suite of isotopic and geochemical tracers in groundwater has been used to provide hydrologic assessments of the hierarchy of flow systems in aquifers underlying the central Great Plains (southeastern Colorado and western Kansas) of the United States and to determine the late Pleistocene and Holocene paleotemperature and paleorecharge record. Hydrogeologic and geochemical tracer data permit classification of the samples into late Holocene, late Pleistocene-early Holocene, and much older Pleistocene groups. Paleorecharge rates calculated from the Cl concentration in the samples show that recharge rates were at least twice the late Holocene rate during late Pleistocene-early Holocene time, which is consistent with their relative depletion in 16O and D. Noble gas (Ne, Ar, Kr, Xe) temperature calculations confirm that these older samples represent a recharge environment approximately 5??C cooler than late Holocene values. These results are consistent with the global climate models that show a trend toward a warmer, more arid climate during the Holocene. (C) 2000 University of Washington.

Mass wasting deposits in the upper Sehonghong valley, eastern Lesotho: Late Pleistocene climate implications

NASA Astrophysics Data System (ADS)

Mills, S. C.; Grab, S. W.

2009-04-01

Despite considerable research attention on apparent periglacial, glacial and sedimentary phenomena in the Maluti-Drakensberg alpine environment, knowledge on the Quaternary environmental history of this important watershed and climate-divide is still rather rudimentary. The dearth of Quaternary environmental indicators (proxy data) in the high Drakensberg is partly owing to the harsh climate (e.g. high wind speeds and high seasonal precipitation), which offers a poor preservation of past biological remains (e.g. bones, dung, middens, pollen). Possibly the best opportunity to reconstruct high Drakensberg palaeoenvironments is from sedimentary sequences exposed along fluvially-incised valley fills. The upper Sehonghong River (3000 to 3200 m a.s.l.) flows in a westerly direction and is flanked by north- and south-facing slopes reaching 3465 m a.s.l. Sediment is exposed on both the north- and south-facing slopes along the river. Despite uniform regional environmental conditions (geology, topography, climate, vegetation), there is a notable absence of similar north-facing deposits in adjacent upper valley catchments to the north and south of Sehonghong Valley. The upper Sehonghong Valley thus presents somewhat ‘unique' evidence for palaeo-slope mass movement in this alpine region. Thick colluvial deposits are most prominent on the south-facing slopes along the Sehonghong River and occur at altitudes between 3100 m a.s.l. and 3150 m a.s.l. The colluvial mantles are approximately 7 m in thickness, however reach up to 13 m in some areas. Although the north-facing lower valley side-slopes are generally absent of deposits, the notable exception is the thick stratified deposit located a few kilometres upstream. Whilst the south-facing deposits are relatively uniform in nature, the north-facing deposits consist of alternating units of gravel and organic sediment, dated to 36 600 ± 1400 14C yrs BP, and reflecting environmental changes during the Late Pleistocene. Mass

Late Pliocene and Quaternary Eurasian locust infestations in the Canary Archipelago

USGS Publications Warehouse

Meco, J.; Muhs, D.R.; Fontugne, M.; Ramos, A.J.; Lomoschitz, A.; Patterson, D.

2011-01-01

The Canary Archipelago has long been a sensitive location to record climate changes of the past. Interbedded with its basalt lavas are marine deposits from the principal Pleistocene interglacials, as well as aeolian sands with intercalated palaeosols. The palaeosols contain African dust and innumerable relict egg pods of a temperate-region locust (cf. Dociostaurus maroccanusThunberg 1815). New ecological and stratigraphical information reveals the geological history of locust plagues (or infestations) and their palaeoclimatic significance. Here, we show that the first arrival of the plagues to the Canary Islands from Africa took place near the end of the Pliocene, ca. 3Ma, and reappeared with immense strength during the middle Late Pleistocene preceding MIS (marine isotope stage) 11 (ca. 420ka), MIS 5.5 (ca. 125ka) and probably during other warm interglacials of the late Middle Pleistocene and the Late Pleistocene. During the Early Holocene, locust plagues may have coincided with a brief cool period in the current interglacial. Climatically, locust plagues on the Canaries are a link in the chain of full-glacial arid-cold climate (calcareous dunes), early interglacial arid-sub-humid climate (African dust inputs and locust plagues), peak interglacial warm-humid climate (marine deposits with Senegalese fauna), transitional arid-temperate climate (pedogenic calcretes), and again full-glacial arid-cold climate (calcareous dunes) oscillations. During the principal interglacials of the Pleistocene, the Canary Islands recorded the migrations of warm Senegalese marine faunas to the north, crossing latitudes in the Euro-African Atlantic. However, this northward marine faunal migration was preceded in the terrestrial realm by interglacial infestations of locusts. ??? Locust plagues, Canary Islands, Late Pliocene, Pleistocene, Holocene, palaeoclimatology. ?? 2010 The Authors, Lethaia ?? 2010 The Lethaia Foundation.

Glaciation in the Andes during the Lateglacial and Holocene

NASA Astrophysics Data System (ADS)

Rodbell, Donald T.; Smith, Jacqueline A.; Mark, Bryan G.

2009-10-01

This review updates the chronology of Andean glaciation during the Lateglacial and the Holocene from the numerous articles and reviews published over the past three decades. The Andes, which include some of the world's wettest and driest mountainous regions, offer an unparalleled opportunity to elucidate spatial and temporal patterns of glaciation along a continuous 68-degree meridional transect. The geographic and altitudinal extent of modern glaciers and the sensitivity of both modern and former glaciers to respond to changes in specific climatic variables reflect broad-scale atmospheric circulation and consequent regional moisture patterns. Glaciers in the tropical Andes and in the mid-latitude Andes are likely to have been far more sensitive to changes in temperature than glaciers in the dry subtropical Andes. Broad-scale temporal and spatial patterns of glaciation during the Lateglacial are apparent. In the southernmost Andes, the Lateglacial chronology appears to have a strong Antarctic signature with the best-dated moraines correlating closely with the Antarctic Cold Reversal. The southernmost Andes do not appear to have experienced a significant ice advance coeval with the Younger Dryas (YD) climatic reversal. At the other end of the Andes, from ˜0 to 9°N, a stronger YD connection may exist, but critical stratigraphic and geochronologic work is required before a YD ice advance can be fully demonstrated. In the central Andes of Peru, well-dated moraines record a significant ice readvance at the onset of the YD, but ice was retreating during much of the remaining YD interval. The spatial-temporal pattern of Holocene glaciation exhibits tantalizing but incomplete evidence for an Early to Mid-Holocene ice advance(s) in many regions, but not in the arid subtropical Andes, where moraines deposited during or slightly prior to the Little Ice Age (LIA) record the most extensive advance of the Holocene. In many regions, there is strong evidence for Neoglacial

Partitioning the Quaternary

NASA Astrophysics Data System (ADS)

Gibbard, Philip L.; Lewin, John

2016-11-01

We review the historical purposes and procedures for stratigraphical division and naming within the Quaternary, and summarize the current requirements for formal partitioning through the International Commission on Stratigraphy (ICS). A raft of new data and evidence has impacted traditional approaches: quasi-continuous records from ocean sediments and ice cores, new numerical dating techniques, and alternative macro-models, such as those provided through Sequence Stratigraphy and Earth-System Science. The practical usefulness of division remains, but there is now greater appreciation of complex Quaternary detail and the modelling of time continua, the latter also extending into the future. There are problems both of commission (what is done, but could be done better) and of omission (what gets left out) in partitioning the Quaternary. These include the challenge set by the use of unconformities as stage boundaries, how to deal with multiphase records in ocean and terrestrial sediments, what happened at the 'Early-Mid- (Middle) Pleistocene Transition', dealing with trends that cross phase boundaries, and the current controversial focus on how to subdivide the Holocene and formally define an 'Anthropocene'.

Influence of the Amlia fracture zone on the evolution of the Aleutian Terrace forearc basin, central Aleutian subduction zone

USGS Publications Warehouse

Ryan, Holly F.; Draut, Amy E.; Keranen, Katie M.; Scholl, David W.

2012-01-01

During Pliocene to Quaternary time, the central Aleutian forearc basin evolved in response to a combination of tectonic and climatic factors. Initially, along-trench transport of sediment and accretion of a frontal prism created the accommodation space to allow forearc basin deposition. Transport of sufficient sediment to overtop the bathymetrically high Amlia fracture zone and reach the central Aleutian arc began with glaciation of continental Alaska in the Pliocene. As the obliquely subducting Amlia fracture zone swept along the central Aleutian arc, it further affected the structural evolution of the forearc basins. The subduction of the Amlia fracture zone resulted in basin inversion and loss of accommodation space east of the migrating fracture zone. Conversely, west of Amlia fracture zone, accommodation space increased arcward of a large outer-arc high that formed, in part, by a thickening of arc basement. This difference in deformation is interpreted to be the result of a variation in interplate coupling across the Amlia fracture zone that was facilitated by increasing subduction obliquity, a change in orientation of the subducting Amlia fracture zone, and late Quaternary intensification of glaciation. The change in coupling is manifested by a possible tear in the subducting slab along the Amlia fracture zone. Differences in coupling across the Amlia fracture zone have important implications for the location of maximum slip during future great earthquakes. In addition, shaking during a great earthquake could trigger large mass failures of the summit platform, as evidenced by the presence of thick mass transport deposits of primarily Quaternary age that are found in the forearc basin west of the Amlia fracture zone.

Spatiotemporal analysis of Quaternary normal faults in the Northern Rocky Mountains, USA

NASA Astrophysics Data System (ADS)

Davarpanah, A.; Babaie, H. A.; Reed, P.

2010-12-01

The mid-Tertiary Basin-and-Range extensional tectonic event developed most of the normal faults that bound the ranges in the northern Rocky Mountains within Montana, Wyoming, and Idaho. The interaction of the thermally induced stress field of the Yellowstone hot spot with the existing Basin-and-Range fault blocks, during the last 15 my, has produced a new, spatially and temporally variable system of normal faults in these areas. The orientation and spatial distribution of the trace of these hot-spot induced normal faults, relative to earlier Basin-and-Range faults, have significant implications for the effect of the temporally varying and spatially propagating thermal dome on the growth of new hot spot related normal faults and reactivation of existing Basin-and-Range faults. Digitally enhanced LANDSAT 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 4 and 5 Thematic Mapper (TM) bands, with spatial resolution of 30 m, combined with analytical GIS and geological techniques helped in determining and analyzing the lineaments and traces of the Quaternary, thermally-induced normal faults in the study area. Applying the color composite (CC) image enhancement technique, the combination of bands 3, 2 and 1 of the ETM+ and TM images was chosen as the best statistical choice to create a color composite for lineament identification. The spatiotemporal analysis of the Quaternary normal faults produces significant information on the structural style, timing, spatial variation, spatial density, and frequency of the faults. The seismic Quaternary normal faults, in the whole study area, are divided, based on their age, into four specific sets, which from oldest to youngest include: Quaternary (>1.6 Ma), middle and late Quaternary (>750 ka), latest Quaternary (>15 ka), and the last 150 years. A density map for the Quaternary faults reveals that most active faults are near the current Yellowstone National Park area (YNP), where most seismically active faults, in the past 1.6 my

Acceleration of thaw slump activity in glaciated landscapes of the Western Canadian Arctic

NASA Astrophysics Data System (ADS)

Segal, Rebecca A.; Lantz, Trevor C.; Kokelj, Steven V.

2016-03-01

Climate change is increasing the frequency and intensity of thermokarst, but the influences of regional climate and physiography remain poorly understood. Retrogressive thaw slumping is one of the most dynamic forms of thermokarst and affects many areas of glaciated terrain across northwestern Canada. In this study, we used airphotos and satellite imagery to investigate the influence of climate and landscape factors on thaw slump dynamics. We assessed slump size, density, and growth rates in four regions of ice-rich terrain with contrasting climate and physiographic conditions: the Jesse Moraine, the Tuktoyaktuk Coastlands, the Bluenose Moraine, and the Peel Plateau. Observed increases in: (1) the area impacted by slumps (+2 to +407%), (2) average slump sizes (+0.31 to +1.82 ha), and (3) slump growth rates (+169 to +465 m2 yr-1) showed that thermokarst activity is rapidly accelerating in ice-rich morainal landscapes in the western Canadian Arctic, where slumping has become a dominant driver of geomorphic change. Differences in slump characteristics among regions indicate that slump development is strongly influenced by topography, ground ice conditions, and Quaternary history. Observed increases in slump activity occurred in conjunction with increases in air temperature and precipitation, but variation in slump activity among the four regions suggests that increased precipitation has been an important driver of change. Our observation that the most rapid intensification of slump activity occurred in the coldest environment (the Jesse Moraine on Banks Island) indicates that ice-cored landscapes in cold permafrost environments are highly vulnerable to climate change.

Mineral magnetic characteristics of the late Quaternary coastal red sands of Bheemuni, East Coast (India)

NASA Astrophysics Data System (ADS)

Srivastava, Priyeshu; Sangode, S. J.; Parmar, Nikita; Meshram, D. C.; Jadhav, Priyanka; Singhvi, A. K.

2016-11-01

The voluminous red sand deposits of Bheemuni in the east coast of India provide record of coastal land-sea interaction during the late Quaternary climatic and eustatic oscillations. Limited information on the origin and depositional environments of these red sands and their chronology is available. We studied two inland to coast cross profiles from Bheemuni red sand deposits using mineral magnetism, color characteristics and Citrate-bicarbonate-dithionite (CBD) extractable pedogenic iron oxides over 23 horizons along with optically stimulated luminescence (OSL) chronology at 6 horizons. The oldest exposed bed had an optical age of 48.9 ± 1.7 ka. Differential ages between the two parallel sections (SOS = 48.9 ± 1.7 to 12.1 ± 0.3 ka and IMD = 29.3 ± 3.5 ka) suggest laterally shifting fluvial sedimentation. Both the profiles show significant amount of antiferromagnetic oxide (hematite) along with ferrimagnetic (magnetite/maghemite) mineral composition. The granulometric (/domain-) sensitive parameters (χFD, χARM, SIRM/χLF and χARM/χLF) indicate variable concentration of superparamagnetic (SP) and single domain (SD) particles between the two profiles. The higher frequency dependent and pedogenic magnetic susceptibilities (χFD and χpedo) in the younger (IMD) profile suggest enhanced pedogenesis under a warm-wet climate post 29.3 ka and also during Holocene. A combination of hard isothermal remanent magnetization (HIRM) and redness rating (RR) index indicates distinct but variable concentration of a) crystalline and b) poorly crystalline (pigmentary) hematites in both the profiles. We consider that the former (#a) is derived from hinterland red soils and possibly due to post-depositional diagenesis, and the latter (#b) precipitated from the dissolved iron under fluvial regime imparting the unique red coloration to Bheemuni sands. Partial to complete alteration of ferromagnesian minerals due to pedogenesis in hinterlands under warm-wet climate was therefore the

From middle Miocene to late Quaternary spatial and temporal evolution of Cappadocian Volcanism

NASA Astrophysics Data System (ADS)

Aydar, E.; Cubukcu, E.; Ersoy, O.; Kabadayı, E.; Duncan, R.

2009-04-01

Cappadocian Volcanism, Central Turkey was active from Miocene to upper Holocene, originating from varying sources and presents various dynamics. Central Anatolia constitutes a plateau reaching to 1100-1200 meters from the sea level. From Miocene to Quaternary, the volcanism and/or its relationships with local tectonic targeted in numerous works. Those works can be classified as follows: (i) volcanism-tectonic relationship (Pasquare et al, 1988; Toprak and Goncuoglu, 1993; Toprak, 1998, Dhont et al, 1998; Froger et al, 1998), (ii) volcanological, petrological, geochemical works on stratovolcanoes, monogenetic vents, ignimbrites (Batum, 1978; Ercan, 1985; Aydar, 1992; Aydar and Gourgaud, 1993; Aydar et al, 1994; Aydar et al, 1995; Le Pennec et al, 1994; Druitt et al, 1995; Aydar and Gourgaud, 1998; Deniel et al, 1998, Temel, 1998; Kuzucuoglu et al, 1998; Mouralis et al, 2002; Sen et al, 2003) (iii) Geophysical works on the missing calderas (Ongur, 1978; Ekingen, 1982; Froger et al,1998). Cappadocian landscape is made principally of eroded ignimbirites forming fair chimneys. Apart from the ignimbrites, Cappadocia bears several stratovolcanoes (Mt Erciyes, Mt. Hasan) and numerous monogenetic vents (cinder cones, maars, domes) and some andesitic dacitic relicts of lava fields intercalated within the ignimbritic sequence. Although the stratovolcanoes have some historical activities, their initial eruptions occured in Miocene (Kecikalesi stage of Mt Hasan- 13 My), Pliocene (Kocdag stage of Mt Erciyes). The monogenetic vents demonstrate interestingly bi-modal character which is typically found in rifted regions of the world. Origin of this young volcanism is proposed as collision related transitional alkaline-calcalkaline association (Aydar, 1992, Deniel et al, 1998), is also linked to the subduction (Olanca, 1994). Our preliminary data on the Quaternary rhyolitic glass combined with chemical analysis of the Miocene volcanics exhibit that a slight transition from

Evolution of ice sheets in the early Quaternary of the central North Sea: 2.58 Ma to 0.78 Ma

NASA Astrophysics Data System (ADS)

Lamb, R.; Huuse, M.; Stewart, M.; Brocklehurst, S. H.

2016-12-01

Integration of chronostratigraphic proxies with 3D seismic and well-log data has allowed for a basin-wide re-interpretation of the onset of glaciation in the central North Sea during the Quaternary. Mapping of seismic geomorphology, calculations of water depth and sediment accumulation rates, and other basin analysis techniques unravel the evolution of the North Sea basin during the early Pleistocene, a period of dramatic global cooling and rapid 41 kyr glacial-interglacial cycles, identifying a system which is increasingly dominated by large, continental-scale ice sheets. Prior to this study continental-scale ice sheets were generally not considered able to grow in a 41 kyr cycle and the earliest date for such an ice sheet in the North Sea was identified at the onset of tunnel valley formation in the Elsterian (0.48 Ma; MIS 12) which forms a large regional-scale glacial unconformity. At the onset of the Pleistocene at 2.58 Ma the North Sea basin was an elongate `mega-fjord' with water depths of up to 350 m, infilling rapidly as the European river systems deposited a large clinoform complex in the southern end of the basin. This period corresponds to the preservation of large scale ice-berg scouring on clinoform topsets, suggesting the presence of marine-terminating ice sheets with repeated calving events. As the Pleistocene progressed and global climate became increasingly colder the North Sea became smaller and shallower due to the continual infill of the basin. At 1.72 Ma the basin reached a critical point between the cold climate and the shallowing of the basin and the first evidence for grounded glaciation in the form of mega-scale glacial lineations is seen at this level. Between 1.72 and 0.48 Ma there is evidence for ice-streaming in the form of multiple MSGL flow sets re-occupying the central North Sea, as well as a large glaciotectonic complex. The glacial geomorphological evidence presented pushes back the date of grounded glaciation in the central North

Application of Thermoluminescence dating to Sambagawa metamorphic rocks for evaluation of the late Quaternary uprifting of Central Shikoku, Japan

NASA Astrophysics Data System (ADS)

Nishikawa, O.

2016-12-01

Thermoluminescence (TL) dating is one of the geochronometry with a low closure temperature, which covers a wide range of younger ages from 1k to 1m yrs, and used to be applied to young volcanics and archeological burnt materials. These materials experienced an instant temperature drop under the closure temperature just after they are generated. If crust is rapidly uplifting, it may possible to apply TL dating even for basement rocks to reconstruct a young history of orogeny. TL age applied to basement is not the age of rock itself, but the age since the rock rising from the deeper part crossed the depth of the closure temperature. Therefore TL age of basement rock is the function of both uplifting rate and geothermal gradient. In this study, in order to evaluation of the late Quaternary uplifting of the central Shikoku, Japan, TL dating of quartz grain derived from the Sambagawa metamorphic rocks has been performed. The ages are in 100-1000 kyr orders and much older than TL ages obtained from the hanging wall of Alpine fault, New Zealand (Nishikawa et al., 2015; AGU Fall meeting). This can be due to the difference of geothermal gradient and uplifting rate between two orogenic belts, and interpreted that the hanging wall of the Alpine fault has been rapidly lifted up from the shallower closure temperature depth, while the rocks in central Shikoku have been rising slowly from deeper part.

Unraveling tectonics and climate forcing in the late-Neogene exhumation history of South Alaska

NASA Astrophysics Data System (ADS)

Valla, Pierre; Champagnac, Jean-Daniel; Shuster, David; Herman, Frédéric; Giuditta Fellin, Maria

2015-04-01

The southern Alaska range presents an ideal setting to study the complex interactions between tectonics, climate and surface processes in landscape evolution. It exhibits active tectonics with the ongoing subduction/collision between Pacific and North America, and major active seismogenic reverse and strike-slip faults. The alpine landscape, rugged topography and the important ice-coverage at present reveal a strong glacial imprint associated with high erosion and sediment transport rates. Therefore, the relative importance of climatically-driven glacial erosion and tectonics for the observed late-exhumation history appears to be quite complex to decipher. Here, we first perform a formal inversion of an extensive bedrock thermochronological dataset from the literature to quantify the large-scale 20-Myr exhumation history over the entire southern Alaska. We show that almost half of the variability within the thermochronological record can be explained by modern annual precipitations spatial distribution, the residuals clearly evidencing localized exhumation along major tectonic structures of the frontal fold and thrust belt. Our results confirm high exhumation rates in the St Elias "syntaxis" and frontal zones for the last 0-2 Myr, where major ice fields and high precipitation rates likely sustained high exhumation rates; however the impact of late Cenozoic glaciations is difficult to constrain because of the low resolution on the exhumation history older than ~2 Myr. On the contrary, our inversion outcomes highlight that north of the Bagley Icefield the long-term exhumation has remained quite slow and continuous over the last ~20 Myr, with no late-stage signal of exhumation change since the onset of glaciations despite a clear glacial imprint on the landscape. We thus focus on the Granite Range (Wrangell-St Elias National Park, Alaska), an area presenting a strong glacial imprint but minor tectonic activity with only localized brittle deformation. We sampled four

Late Quaternary sea-ice history of northern Fram Strait/Arctic Ocean

NASA Astrophysics Data System (ADS)

Kremer, Anne; Stein, Rüdiger; Fahl, Kirsten; Matthießen, Jens; Forwick, Matthias; O'Regan, Matt

2016-04-01

One of the main characteristics of the Arctic Ocean is its seasonal to perennial sea-ice cover. Variations of sea-ice conditions affect the Earth's albedo, primary production, rate of deep-water etc.. During the last decades, a drastic decrease in sea ice has been recorded, and the causes of which, i.e., natural vs. anthropogenic forcings, and their relevance within the global climate system, are subject of intense scientific and societal debate. In this context, records of past sea-ice conditions going beyond instrumental records are of major significance. These records may help to better understand the processes controlling natural sea-ice variability and to improve models for forecasts of future climatic conditions. During RV Polarstern Cruise PS92 in summer 2015, a 860 cm long sediment core (PS92/039-2) was recovered from the eastern flank of Yermak Plateau north of the Svalbard archipelago (Peeken, 2015). Based on a preliminary age model, this sediment core probably represents the time interval from MIS 6 to MIS 1. This core, located close to the modern summer ice edge, has been selected for reconstruction of past Arctic sea-ice variability based on specific biomarkers. In this context, we have determined the ice-algae-derived sea-ice proxy IP25 (Belt et al., 2007), in combination with other biomarkers indicative for open-water conditions (cf., Müller et al., 2009, 2011). Furthermore, organic carbon fluxes were differentiated using specific biomarkers indicative for marine primary production (brassicasterol, dinosterol) and terrigenous input (campesterol, β-sitosterol). In this poster, preliminary results of our organic-geochemical and sedimentological investigations are presented. Distinct fluctuations of these biomarkers indicate several major, partly abrupt changes in sea-ice cover in the Yermak Plateau area during the late Quaternary. These changes are probably linked to changes in the inflow of Atlantic Water along the western coastline of Svalbard into

Quaternary geology of the Bellevue area in Blaine and Camas Counties, Idaho

USGS Publications Warehouse

Schmidt, Dwight Lyman

1962-01-01

The Bellevue area covers about 350 square miles of a foothill belt between the Rocky Mountains to the north and the Snake River plains to the south. Complexly deformed impure quartzites and limestones of the Mississippian Milligen and Pennsylvanian-Permian Wood River formations were intruded by large bodies of quartz diorite and granodiorite along regional structures trending northwesterly; the intrusions are part of the Cretaceous Idaho batholith. Erosional remnants of the Challis volcanics, dominantly latitic to andesitic in composition and early(?) to middle Tertiary in age, rest unconformably on the older rocks. A sequence of Pliocene Rhyolitic ash flows and basaltic lava flows unconformably overlies the Challis and older rocks and is in turn unconformably overlain by olivine basalt of late Pliocene or early Quaternary age. The main valleys of the area, partly Erosional and partly structural in origin, are underlaind by late Quaternary olivine basalt flows (Snake River basalt) and intercalated lacustrine, fluvial, proglacial sediments. The Big Wood River, the master stream of the area, flows southward through a narrow steep-sided valley in the mountainous country north of the Bellevue area and debouches into a broad alluvial valley, the Wood River Valley, in the foothill belt. The valley has the shape of an isosceles triangle with a ten mile long, east-west base consisting of a ridge of Pliocene volcanics which separates the valley from the Snake River Plains to the south. The river now flows through a narrow gap in the southwest corner of the triangle. A similar, but wider, gap around the east end of the ridge was formerly occupied by the river. The river has been shifted back and forth between these two gaps at least four times during an interval in which six late Quaternary basalt flows erupted in the Bellevue area. Two of the flows caused direct diversion of the river and another was influential in bringing about a diversion on an aggradational fan upstream

Late Quaternary activity of the Grote Brogel fault, NE Belgium

NASA Astrophysics Data System (ADS)

Vanneste, Kris; Deckers, Jef; Van Noten, Koen; Schiltz, Marco; Lecocq, Thomas

2017-04-01

The Grote Brogel fault (GBF) is a WNW-ESE striking normal fault that is part of the western border fault system of the Roer Valley Graben in NE Belgium. It is one of three faults branching NW-ward from the main border fault (Geleen fault) near Bree, but its orientation diverges 22° from the general NW-SE orientation of the graben, causing a wide left step. Unlike the Geleen fault, the surface expression of the GBF has not been investigated in detail so far. We studied the Quaternary activity of the GBF and its effects on the local hydrology based on a high-resolution LiDAR digital terrain model (DTM), and geophysical and geological surveying at two sites, combining Electrical Resistivity Tomography (ERT), Cone Penetration Tests (CPTs) and boreholes. The GBF defines the northern edge of the Campine Plateau, an elevated area covered by the late Early to Middle Pleistocene Main Terrace of the Meuse River. Cumulative vertical offset since deposition of this terrace has resulted in a distinct 10-km-long fault scarp, the height of which decreases from 11 m near Bree in the east to less than 5 m near Grote Brogel in the west. The along-strike evolution of offset suggests that the GBF does not define an individual rupture segment, but is likely contiguous with the Geleen fault. DTM analysis indicates that scarps are only preserved in a few isolated places, and that the surface trace is rather complex, consisting of a series of short, relatively straight sections with strikes varying between 255° and 310°, arranged in a generally left-stepping pattern. At both investigated sites, ERT profiles clearly demonstrate the presence of fault splays in the shallow subsurface (< 50 m) underneath the identified scarps evidenced by a sudden increase in depth and thickness of a high-resistivity unit on top of a lower-resistivity unit. Boreholes and CPTs allow correlating the high-resistivity unit with the medium to coarse gravel-bearing sands of the Meuse Group, and the lower

Did intense volcanism trigger the first Late Ordovician icehouse?

USGS Publications Warehouse

Buggisch, Werner; Joachimski, Michael M.; Lehnert, Oliver; Bergstrom, S. M.; Repetski, John E.

2009-01-01

Oxygen isotopes measured on Late Ordovician conodonts from Minnesota and Kentucky (United States) were studied to reconstruct the paleotemperature history during late Sandbian to Katian (Mohawkian–Cincinnatian) time. This time interval was characterized by intense volcanism, as shown by the prominent Deicke, Millbrig, and other K-bentonite beds. A prominent carbon isotope excursion (Guttenberg δ13C excursion, GICE) postdates the Millbrig volcanic eruptions, and has been interpreted to reflect a drawdown of atmospheric carbon dioxide and climatic cooling. The oxygen isotope record in conodont apatite contradicts this earlier interpretation. An increase in δ18O of 1.5‰ (Vienna standard mean ocean water) just above the Deicke K-bentonite suggests an abrupt and short-lived cooling that possibly initiated a first short-term glacial episode well before the major Hirnantian glaciation. The decrease in δ18O immediately after the mega-eruptions indicates warming before the GICE, and no cooling is shown in the GICE interval. The coincidence of the Deicke mega-eruption with a cooling event suggests that this major volcanic event had a profound effect on Late Ordovician (late Mohawkian) climate.

Did intense volcanism trigger the first Late Ordovician icehouse?

USGS Publications Warehouse

Buggisch, Werner; Joachimski, Michael M.; Lehnert, Oliver; Bergström, Stig M.; Repetski, John E.; Webers, Gerald F.

2010-01-01

Oxygen isotopes measured on Late Ordovician conodonts from Minnesota and Kentucky (United States) were studied to reconstruct the paleotemperature history during late Sandbian to Katian (Mohawkian–Cincinnatian) time. This time interval was characterized by intense volcanism, as shown by the prominent Deicke, Millbrig, and other K-bentonite beds. A prominent carbon isotope excursion (Guttenberg δ13C excursion, GICE) postdates the Millbrig volcanic eruptions, and has been interpreted to reflect a drawdown of atmospheric carbon dioxide and climatic cooling. The oxygen isotope record in conodont apatite contradicts this earlier interpretation. An increase in δ18O of 1.5‰ (Vienna standard mean ocean water) just above the Deicke K-bentonite suggests an abrupt and short-lived cooling that possibly initiated a first short-term glacial episode well before the major Hirnantian glaciation. The decrease in δ18O immediately after the mega-eruptions indicates warming before the GICE, and no cooling is shown in the GICE interval. The coincidence of the Deicke mega-eruption with a cooling event suggests that this major volcanic event had a profound effect on Late Ordovician (late Mohawkian) climate.

Quaternary geologic map of the Winnipeg 4 degrees x 6 degrees quadrangle, United States and Canada

USGS Publications Warehouse

Fullerton, D. S.; Ringrose, S.M.; Clayton, Lee; Schreiner, B.T.; Goebel, J.E.

2000-01-01

The Quaternary Geologic Map of the Winnipeg 4? ? 6? Quadrangle, United States and Canada, is a component of the U.S. Geological Survey Quaternary Geologic Atlas of the United States map series (Miscellaneous Investigations Series I-1420), an effort to produce 4? ? 6? Quaternary geologic maps, at 1:1 million scale, of the entire conterminous United States and adjacent Canada. The map and the accompanying text and supplemental illustrations provide a regional overview of the areal distributions and characteristics of surficial deposits and materials of Quaternary age (~1.8 Ma to present) in parts of North Dakota, Minnesota, Manitoba, and Saskatchewan. The map is not a map of soils as soils are recognized in agriculture. Rather, it is a map of soils as recognized in engineering geology, or of substrata or parent materials in which agricultural soils are formed. The map units are distinguished chiefly on the basis of (1)genesis (processes of origin) or environments of deposition: for example, sediments deposited primarily by glacial ice (glacial deposits or till), sediments deposited in lakes (lacustrine deposits), or sediments deposited by wind (eolian deposits); (2) age: for example, how long ago the deposits accumulated; (3) texture (grain size)of the deposits or materials; (4) composition (particle lithology) of the deposits or materials; (5) thickness; and (6) other physical, chemical, and engineering properties. Supplemental illustrations show (1) temporal correlation of the map units, (2) the areal relationships of late Wisconsin glacial ice lobes and sublobes, (3) temporal and spatial correlation of late Wisconsin glacial phases, readvance limits, and ice margin stillstands, (4) temporal and stratigraphic correlation of surface and subsurface glacial deposits in the Winnipeg quadrangle and in adjacent 4? ? 6? quadrangles, and (5) responsibility for state and province compilations. The database provides information related to geologic hazards (for example

The Quaternary Silver Creek Fault Beneath the Santa Clara Valley, California

USGS Publications Warehouse

Wentworth, Carl M.; Williams, Robert A.; Jachens, Robert C.; Graymer, Russell W.; Stephenson, William J.

2010-01-01

The northwest-trending Silver Creek Fault is a 40-km-long strike-slip fault in the eastern Santa Clara Valley, California, that has exhibited different behaviors within a changing San Andreas Fault system over the past 10-15 Ma. Quaternary alluvium several hundred meters thick that buries the northern half of the Silver Creek Fault, and that has been sampled by drilling and imaged in a detailed seismic reflection profile, provides a record of the Quaternary history of the fault. We assemble evidence from areal geology, stratigraphy, paleomagnetics, ground-water hydrology, potential-field geophysics, and reflection and earthquake seismology to determine the long history of the fault in order to evaluate its current behavior. The fault formed in the Miocene more than 100 km to the southeast, as the southwestern fault in a 5-km-wide right step to the Hayward Fault, within which the 40-km-long Evergreen pull-apart basin formed. Later, this basin was obliquely cut by the newly recognized Mt. Misery Fault to form a more direct connection to the Hayward Fault, although continued growth of the basin was sufficient to accommodate at least some late Pliocene alluvium. Large offset along the San Andreas-Calaveras-Mt Misery-Hayward Faults carried the basin northwestward almost to its present position when, about 2 Ma, the fault system was reorganized. This led to near abandonment of the faults bounding the pull-apart basin in favor of right slip extending the Calaveras Fault farther north before stepping west to the Hayward Fault, as it does today. Despite these changes, the Silver Creek Fault experienced a further 200 m of dip slip in the early Quaternary, from which we infer an associated 1.6 km or so of right slip, based on the ratio of the 40-km length of the strike-slip fault to a 5-km depth of the Evergreen Basin. This dip slip ends at a mid-Quaternary unconformity, above which the upper 300 m of alluvial cover exhibits a structural sag at the fault that we interpret as

Sedimentary development and correlation of Late Quaternary terraces in the Kyrenia Range, northern Cyprus, using a combination of sedimentology and optical luminescence data

NASA Astrophysics Data System (ADS)

Palamakumbura, Romesh N.; Robertson, Alastair H. F.; Kinnaird, Tim C.; Sanderson, David C. W.

2016-01-01

use of the portable OSL reader is therefore an effective means of correlating Late Quaternary terrace deposits in northern Cyprus and probably also elsewhere.

Ambient and Dosed Exposure to Quaternary Ammonium Disinfectants Causes Neural Tube Defects in Rodents

PubMed Central

Hrubec, Terry C.; Melin, Vanessa E.; Shea, Caroline S.; Ferguson, Elizabeth E.; Garofola, Craig; Repine, Claire M.; Chapman, Tyler W.; Patel, Hiral R.; Razvi, Reza M.; Sugrue, Jesse E.; Potineni, Haritha; Magnin-Bissel, Geraldine; Hunt, Patricia A.

2018-01-01

Background Quaternary ammonium compounds are a large class of chemicals used for their antimicrobial and antistatic properties. Two common quaternary ammonium compounds, alkyldimethylbenzyl ammonium chloride (ADBAC) and didecyldimethyl ammonium chloride (DDAC), are combined in common cleaners and disinfectants. Introduction of a cleaner containing ADBAC+DDAC in the vivarium caused neural tube defects (NTDs) in mice and rats. Methods To further evaluate this finding, male and female mice were dosed in the feed at 60 or 120 mg/kg/day, or by oral gavage at 7.5, 15, or 30 mg/kg ADBAC+DDAC. Mice also received ambient exposure to ADBAC+DDAC from the disinfectant used in the mouse room. Embryos were evaluated on gestational day 10 for NTDs, and fetuses were evaluated on gestational day 18 for gross and skeletal malformations. Results We found increased NTDs with exposure to ADBAC+DDAC in both rats and mice. The NTDs persisted for two generations after cessation of exposure. Notably, male exposure alone was sufficient to cause NTDs. Equally significant, ambient exposure from disinfectant use in the vivarium, influenced the levels of NTDs to a greater extent than oral dosing. No gross or significant axial skeletal malformations were observed in late gestation fetuses. Placental abnormalities and late gestation fetal deaths were increased at 120 mg/kg/day, which might explain the lack of malformations observed in late gestation fetuses. Conclusion These results demonstrate that ADBAC+DDAC in combination are teratogenic to rodents. Given the increased use of these disinfectants, further evaluation of their safety in humans and their contribution to health and disease is essential. PMID:28618200

Glaciated valleys in Europe and western Asia

PubMed Central

Prasicek, Günther; Otto, Jan-Christoph; Montgomery, David R.; Schrott, Lothar

2015-01-01

In recent years, remote sensing, morphometric analysis, and other computational concepts and tools have invigorated the field of geomorphological mapping. Automated interpretation of digital terrain data based on impartial rules holds substantial promise for large dataset processing and objective landscape classification. However, the geomorphological realm presents tremendous complexity and challenges in the translation of qualitative descriptions into geomorphometric semantics. Here, the simple, conventional distinction of V-shaped fluvial and U-shaped glacial valleys was analyzed quantitatively using multi-scale curvature and a novel morphometric variable termed Difference of Minimum Curvature (DMC). We used this automated terrain analysis approach to produce a raster map at a scale of 1:6,000,000 showing the distribution of glaciated valleys across Europe and western Asia. The data set has a cell size of 3 arc seconds and consists of more than 40 billion grid cells. Glaciated U-shaped valleys commonly associated with erosion by warm-based glaciers are abundant in the alpine regions of mid Europe and western Asia but also occur at the margins of mountain ice sheets in Scandinavia. The high-level correspondence with field mapping and the fully transferable semantics validate this approach for automated analysis of yet unexplored terrain around the globe and qualify for potential applications on other planetary bodies like Mars. PMID:27019665

Inferences about winter temperatures and summer rains from the late Quaternary record of C4 perennial grasses and C3 desert shrubs in the northern Chihuahuan Desert

USGS Publications Warehouse

Holmgren, Camille A.; Norris, Jodi; Betancourt, Julio L.

2007-01-01

Late Quaternary histories of two North American desert biomes—C4 grasslands and C3 shrublands—are poorly known despite their sensitivity and potential value in reconstructing summer rains and winter temperatures. Plant macrofossil assemblages from packrat midden series in the northern Chihuahuan Desert show that C4 grasses and annuals typical of desert grassland persisted near their present northern limits throughout the last glacial-interglacial cycle. By contrast, key C3 desert shrubs appeared somewhat abruptly after 5000cal.yrBP. Bioclimatic envelopes for select C4 and C3 species are mapped to interpret the glacial-interglacial persistence of desert grassland and the mid-to-late Holocene expansion of desert shrublands. The envelopes suggest relatively warm Pleistocene temperatures with moist summers allowed for persistence of C4 grasses, whereas winters were probably too cold (or too wet) for C3 desert shrubs. Contrary to climate model results, core processes associated with the North American Monsoon and moisture transport to the northern Chihuahuan Desert remained intact throughout the last glacial-interglacial cycle. Mid-latitude effects, however, truncated midsummer (July-August) moisture transport north of 35° N. The sudden expansion of desert shrublands after 5000cal.yrBP may be a threshold response to warmer winters associated with increasing boreal winter insolation, and enhanced El Niño-Southern Oscillation variability.

21 CFR 172.165 - Quaternary ammonium chloride combination.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Quaternary ammonium chloride combination. 172.165... HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used in food in accordance with the...

Simulating the impact of glaciations on continental groundwater flow systems: 1. Relevant processes and model formulation

NASA Astrophysics Data System (ADS)

Lemieux, J.-M.; Sudicky, E. A.; Peltier, W. R.; Tarasov, L.

2008-09-01

In the recent literature, it has been shown that Pleistocene glaciations had a large impact on North American regional groundwater flow systems. Because of the myriad of complex processes and large spatial scales involved during periods of glaciation, numerical models have become powerful tools to examine how ice sheets control subsurface flow systems. In this paper, the key processes that must be represented in a continental-scale 3-D numerical model of groundwater flow during a glaciation are reviewed, including subglacial infiltration, density-dependent (i.e., high-salinity) groundwater flow, permafrost evolution, isostasy, sea level changes, and ice sheet loading. One-dimensional hydromechanical coupling associated with ice loading and brine generation were included in the numerical model HydroGeoSphere and tested against newly developed exact analytical solutions to verify their implementation. Other processes such as subglacial infiltration, permafrost evolution, and isostasy were explicitly added to HydroGeoSphere. A specified flux constrained by the ice sheet thickness was found to be the most appropriate boundary condition in the subglacial environment. For the permafrost, frozen and unfrozen elements can be selected at every time step with specified hydraulic conductivities. For the isostatic adjustment, the elevations of all the grid nodes in each vertical grid column below the ice sheet are adjusted uniformly to account for the Earth's crust depression and rebound. In a companion paper, the model is applied to the Wisconsinian glaciation over the Canadian landscape in order to illustrate the concepts developed in this paper and to better understand the impact of glaciation on 3-D continental groundwater flow systems.

10Be dating of late-glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap, Peru

NASA Astrophysics Data System (ADS)

Kelly, M. A.; Thompson, L. G.

2004-12-01

The surface exposure method, based on the measurement of cosmogenic 10Be produced in quartz, is applied to determine the age of deposition of glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap (about 13° S, 70° W) in southeastern Peru. These data are useful for examining the timing of past glaciation in the tropical Andes and for comparison with chronologies of glaciation at higher latitudes. The preliminary data set consists of more than ten surface exposure ages. Samples used for dating are from the surfaces of boulders on a set of prominent moraines about four kilometers away from the present ice margins. The age of the moraine set was previously bracketed by radiocarbon dating of peat associated with the glacial deposits. Based on radiocarbon ages, these moraines were formed during the late-glacial period, just prior to the last glacial-interglacial transition. The surface exposure dating method enables the direct dating of the moraines. Surface exposure dates are cross-checked with the previously existing radiocarbon dates and provide a means to improve the chronology of past glaciation in the tropical Andes.

Late Quaternary paleoearthquakes along the northern segment of the Nantinghe fault on the southeastern margin of the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Sun, Haoyue; He, Honglin; Wei, Zhanyu; Shi, Feng; Gao, Wei

2017-05-01

The strong earthquake behaviors of faults are significant for learning crustal deformation mechanisms and for assessing regional seismic risk. To date, faults that bound tectonic blocks have attracted considerable concern and many studies; however, scant attention has been paid to faults within blocks that can also host devastating earthquakes. The Nantinghe fault is a left-lateral strike-slip fault within the Southwestern Yunnan Block, and it slips at ∼4 mm/yr suggesting strong activity in the late Quaternary. Nevertheless, no earthquake greater than 6 has ever been recorded along it, except for the 1941 M ∼7 earthquake near the Myanmar-China border region. In contrast, many earthquakes have occurred in the near region, delineating a seismic gap near the Nantinghe fault. Although several studies have been conducted upon it, the activity of its northern segment is confusing, and whether this fault segment has loaded sufficient stress to fail remains debatable. Furthermore, previous work failed to conduct any paleoseismological studies bringing out great uncertainty in learning its activity and faulting behavior, as well as in assessing the regional seismic risk. To solve these problems, we mapped the fault traces utilizing high-resolution satellite images and aerial photographs, and conducted three paleoseismological trenches along the northern segment of the Nantinghe fault. The trench excavations revealed a ∼45,000-year incomplete paleoearthquake history and confirmed that this fault segment has been active since the late Pleistocene but was not ruptured during the 1941 earthquake. Additionally, at least five paleoearthquakes are identified with their respective age ranges of before 39,030 BCE; 38,500-37,220 BCE; 28,475-5445 BCE; 3535 BCE-800 CE; and 1320-1435 CE based on radiocarbon dating. Among the paleoearthquakes, the latest is suggested to have generated a surface rupture much longer than 14 km with a magnitude likely up to Ms 7.0. Furthermore, based

High-resolution seismic sequence stratigraphy and history of relative sea level changes since the Late Miocene, northern continental margin, South China Sea

NASA Astrophysics Data System (ADS)

Zhong, G.; Wang, L.

2013-12-01

The northern South China Sea (SCS) margin is suggested as one of the ideal sites for documenting the late Cenozoic sea level changes for its characteristics of rapid sedimentation and relatively stable structural subsidence since the Late Miocene. In this study, high-resolution seismic profiles acquired by the Guangzhou Marine Geological Survey, calibrated by well control from the ODP sites 1146 and 1148, were utilized to construct a time-significant sequence stratigraphic framework, from which the history of relative sea level changes since the Late Miocene on the northern SCS margin was derived. Our study area is situated in the middle segment of the margin, between the Hainan Island to the west and the Dongsha Islands to the east. This region is to a certain degree far away from the active structural zones and is suggested as the most stable region in the margin. Totally 4000 km seismic profiles were used, which controls an area of about 6×104 km2. The seismic data have a vertical resolution of 5 to 15 m for the Upper Miocene to Quaternary interval. Three regional seismic sequence boundaries were identified. They subdivide the Late Miocene to Quaternary into three mega-sequences, which correspond to the Quaternary, Pliocene and Late Miocene, respectively by tying to well control. The Late Miocene mega-sequence, including 13 component sequences, is characterized with a basal incised canyon-developed interval overlain by three sets of progradational sequences formed in deep-water slope environments. The Pliocene mega-sequence consists of four sets of progradational sequences. Each sequence set contains one to three component sequences. At least 7 component sequences can be identified. The Quaternary mega-sequence consists of five sets of progradational sequences, in which the lower two constitute a retrogressive sequence set and the upper three a progradational sequence set. At least 9 component sequences can be recognized. Most of the component sequences within

Late quaternary geologic framework, north-central Gulf of Mexico

USGS Publications Warehouse

Kindinger, Jack G.; Penland, Shea; Williams, S. Jeffress; Brooks, Gregg R.; Suter, John R.; McBride, Randolph A.

1991-01-01

The geologic framework of the north-central Gulf of Mexico shelf is composed of multiple, stacked, delta systems. Shelf and nearshore sedimentary facies were deposited by deltaic progradation, followed by shoreface erosion and submergence. A variety of sedimentary facies has been identified, including prodelta, delta fringe, distributary, lagoonal, barrier island, and shelf sand sheet. This study is based on the interpretation and the synthesis of > 6,700 km of high-resolution seismic profiles, 75 grab samples, and 77 vibracores. The nearshore morphology, shallow stratigraphy, and sediment distribution of the eastern Louisiana shelf are the products of transgressive sedimentary processes reworking the abandoned St. Bernard delta complex. Relatively recent Mississippi delta lobe consists primarily of fine sand, silt, and clay. In the southern portion of the St. Bernard delta complex, asymmetrical sand ridges (>5 m relief) have formed as the result of marine reworking of distributary mouth-bar sands. Silty sediments from the modern Mississippi Birdsfoot delta onlap the St. Bernard delta complex along the southern edge. The distal margin of the St. Bernard complex is distinct and has a sharp contact on the north near the Mississippi Sound barrier island coastline and a late Wisconsinan delta to the south. The Chandeleur Islands and the barrier islands of Mississippi Sound have been formed by a combination of Holocene and Pleistocene fluvial processes, shoreface erosion, and ravinement of the exposed shelf. Sediments underlying the relatively thin Holocene sediment cover are relict fluvial sands, deposited during the late Wisconsinan lowstand. Subsequent relative sea-level rise allowed marine processes to rework and redistribute sediments that formed the nearshore fine-grained facies and the shelf sand sheet.

Late Quaternary sea-level history and the antiquity of mammoths (Mammuthus exilis and Mammuthus columbi), Channel Islands NationalPark, California, USA

USGS Publications Warehouse

Muhs, Daniel R.; Simmons, Kathleen R.; Groves, Lindsey T.; McGeehin, John P.; Schumann, R. Randall; Agenbroad, Larry D.

2015-01-01

Fossils of Columbian mammoths (Mammuthus columbi) and pygmy mammoths (Mammuthus exilis) have been reported from Channel Islands National Park, California. Most date to the last glacial period (Marine Isotope Stage [MIS] 2), but a tusk of M. exilis (or immature M. columbi) was found in the lowest marine terrace of Santa Rosa Island. Uranium-series dating of corals yielded ages from 83.8 ± 0.6 ka to 78.6 ± 0.5 ka, correlating the terrace with MIS 5.1, a time of relatively high sea level. Mammoths likely immigrated to the islands by swimming during the glacial periods MIS 6 (~ 150 ka) or MIS 8 (~ 250 ka), when sea level was low and the island–mainland distance was minimal, as during MIS 2. Earliest mammoth immigration to the islands likely occurred late enough in the Quaternary that uplift of the islands and the mainland decreased the swimming distance to a range that could be accomplished by mammoths. Results challenge the hypothesis that climate change, vegetation change, and decreased land area from sea-level rise were the causes of mammoth extinction at the Pleistocene/Holocene boundary on the Channel Islands. Pre-MIS 2 mammoth populations would have experienced similar or even more dramatic changes at the MIS 6/5.5 transition.

Quaternary deformation of the Mushi thrust-related fold, northeastern margin of the Pamir

NASA Astrophysics Data System (ADS)

Li, T.; Chen, J.; Huang, D. M.; Thompson, J.; Xiao, P. W.; Yuan, D. Z.; Burbank, D. W.

2010-12-01

The Pamir salient defines the northwestern end of the Himalayan-Tibetan orogen and has overthrust the Tajik-Tarim basin to the north by ~300km along a late Cenozoic, south-dipping intracontinental subduction zone (Burtman and Molnar, 1993). The Quaternary deformation of the salient are concentrated on the outer margins: the sinistral Darvaz fault on the northwestern margin, the Trans-Alai thrust on the north margin and the northeast margin. The GPS-based plate tectonic model indicates the convergence rate is of 8-12mm/a in an N-S direction, nearly 1/4 of that between the Indian plate and the Eurasian plate (DeMets et al., 1990; Reigber et al., 2001; Yang et al., 2008). Previous studies focused on the northwestern margin and the north margin revel their spatial distribution, temporal evolution and kinematic patterns (Burtman and Molnar, 1993; Strecker et al., 1995; Arrowsmith and Strecker, 1999; Coutand et al., 2002). Deformed strata and GPS data indicate Quaternary deformations on the northeastern margin are concentrated on the PFT (the Pamir Front Thrust), the foreland thrust system generated by the latest advancing migration of the Pamir salient, whose kinematic patterns are still poor understood. Integrated by the Mushi thrust and the Mushi anticline, the Mushi thrust-related fold located at eastern end of the PFT. Simple structure, well outcrops and evident deformed terraces make it an excellent place to recognize deformation characters and kinematic patterns of the PFT. The Mushi thrust is north-vergent, roughly parallel with the anticline axis, and west part forming several subparallel fault scarps on the terrace surface and east part buried under the late-Quaternary deposits. The Mushi thrust is north-plunging, with a gentle south limb and a steep north limb. Combining field mapping data and neighboring seismic reflection profiles, following the cross-section balance principle, we can confine the Mushi thrust-related fold is a fault propagation fold

NW-SE Pliocene-Quaternary extension in the Apan-Acoculco region, eastern Trans-Mexican Volcanic Belt

NASA Astrophysics Data System (ADS)

García-Palomo, Armando; Macías, José Luis; Jiménez, Adrián; Tolson, Gustavo; Mena, Manuel; Sánchez-Núñez, Juan Manuel; Arce, José Luis; Layer, Paul W.; Santoyo, Miguel Ángel; Lermo-Samaniego, Javier

2018-01-01

The Apan-Acoculco area is located in the eastern portion of the Mexico basin and the Trans-Mexican Volcanic Belt. The area is transected by right-stepping variably dipping NE-SW normal faults. The Apan-Tlaloc Fault System is a major discontinuity that divides the region into two contrasting areas with different structural and volcanic styles. a) The western area is characterized by a horst-graben geometry with widespread Quaternary monogenetic volcanism and scattered outcrops of Miocene and Pliocene rocks. b) The eastern area is dominated by tilted horsts with a domino-like geometry with widespread Miocene and Pliocene rocks, scattered Quaternary monogenetic volcanoes and the Acoculco Caldera. Gravity data suggest that this structural geometry continues into the Mesozoic limestones. Normal faulting was active since the Pliocene with three stages of extension. One of them, an intense dilatational event began during late Pliocene and continues nowadays, contemporaneously with the emplacement of the Apan-Tezontepec Volcanic Field and the Acoculco caldera. Statistical analysis of cone elongation, cone instability, and the kinematic analysis of faults attest for a NW50°SE ± 7° extensional regime in the Apan-Acoculco area. The activity in some portions of the Apan-Tlaloc Fault System continues today as indicated by earthquake swarms recorded in 1992 and 1996, that disrupted late Holocene paleosols, and Holocene volcanism.

Mapping process and age of Quaternary deposits on Santa Rosa Island, Channel Islands National Park, California

NASA Astrophysics Data System (ADS)

Schmidt, K. M.; Minor, S. A.; Bedford, D.

2016-12-01

Employing a geomorphic process-age classification scheme, we mapped the Quaternary surficial geology of Santa Rosa (SRI) within the Channel Islands National Park. This detailed (1:12,000 scale) map represents upland erosional transport processes and alluvial, fluvial, eolian, beach, marine terrace, mass wasting, and mixed depositional processes. Mapping was motivated through an agreement with the National Park Service and is intended to aid natural resource assessments, including post-grazing disturbance recovery and identification of mass wasting and tectonic hazards. We obtained numerous detailed geologic field observations, fossils for faunal identification as age control, and materials for numeric dating. This GPS-located field information provides ground truth for delineating map units and faults using GIS-based datasets- high-resolution (sub-meter) aerial imagery, LiDAR-based DEMs and derivative raster products. Mapped geologic units denote surface processes and Quaternary faults constrain deformation kinematics and rates, which inform models of landscape change. Significant findings include: 1) Flights of older Pleistocene (>120 ka) and possibly Pliocene marine terraces were identified beneath younger alluvial and eolian deposits at elevations as much as 275 m above modern sea level. Such elevated terraces suggest that SRI was a smaller, more submerged island in the late Neogene and (or) early Pleistocene prior to tectonic uplift. 2) Structural and geomorphic observations made along the potentially seismogenic SRI fault indicate a protracted slip history during the late Neogene and Quaternary involving early normal slip, later strike slip, and recent reverse slip. These changes in slip mode explain a marked contrast in island physiography across the fault. 3) Many of the steeper slopes are dramatically stripped of regolith, with exposed bedrock and deeply incised gullies, presumably due effects related to past grazing practices. 4) Surface water presence is

Reconstructing transport pathways for late Quaternary dust from eastern Australia using the composition of trace elements of long traveled dusts

NASA Astrophysics Data System (ADS)

Petherick, Lynda M.; McGowan, Hamish A.; Kamber, Balz S.

2009-04-01

The southeast Australian dust transport corridor is the principal pathway through which continental emissions of dust from central and eastern Australia are carried to the oceans by the prevailing mid-latitude westerly circulation. The analysis of trace elements of aeolian dust, preserved in lake sediment on North Stradbroke Island, southeast Queensland, is used to reconstruct variation in the intensity and position of dust transport to the island over the past 25,000 yrs. Separation of local and long traveled dust content of lake sediments is achieved using a unique, four-element (Ga, Ni, Tl and Sc) separation method. The local and continental chronologies of aeolian deposition developed by this study show markedly different records, and indicate varied responses to climate variability on North Stradbroke Island (local aeolian sediment component) and in eastern and central Australia (long traveled dust component). The provenance of the continental component of the record to sub-geologic catchment scales was accomplished using a ternary mixing model in which the chemical identification of dusts extracted, from the lake sediments, was compared to potential chemical characteristics of surface dust from the source areas using 16 trace elements. The results indicate that the position and intensity of dust transport pathways during the late Quaternary varied considerably in response to changing atmospheric circulation patterns as well as to variations in sediment supply to dust source areas, which include the large anabranching river systems of the Lake Eyre and Murray-Darling Basins.

Oysters, estuaries, and Late Pleistocene-Holocene sea level, northeastern Gulf of Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroeder, W.W.; Shultz, A.W.

1993-03-01

The timing and magnitude of global sea level fluctuations over the past 35 kyr remain nondum ostenduntur after three decades of study. The construction of local relative sea level histories is often complicated by the need to assess regional tectonic and climatic components together. The authors attempt to contribute to an understanding of sea level fluctuations in the northeastern Gulf of Mexico through the application of faunal tracking, using fossil oyster shells as indicators of paleoestuarine environments. They assume that sites on the continental shelf where oysters have been collected were coastal and therefore are reasonable approximations of past shorelinemore » locations and sea-level elevations. They acknowledge that this assumption is a leap of faith for some observers, but is justified as a provisional step toward an independent determination. Insights into Quaternary coastal paleogeography are gathered from locations and radiocarbon ages of American oyster (Crassostrea virginica) shells collected from the Alabama continental shelf. Prior to the onset of the last Wisconsinan glaciation (35 to 26 kyr BP), estuaries occupied a zone 20 to 25 km seaward of today's coastline. As glaciation increased and sea level was lowered (23 to 21 kyr BP), open coastal estuarine conditions developed southward. Oysters dating from the lowstand period (20 to 16 kyr BP) have not been collected. As sea level rose over the next 10 kyr (16 to 6 kyr BP), estuaries were displaced northward in steps. This data on depths and ages can be viewed as supporting an interpretation of fluctuating Holocene sea level, rather than a steady sea-level rise.« less

Surficial deposits in the Bear Lake Basin

USGS Publications Warehouse

Reheis, Marith C.; Laabs, Benjamin J.C.; Forester, Richard M.; McGeehin, John P.; Kaufman, Darrell S.; Bright, Jordon

2005-01-01

Mapping and dating of surficial deposits in the Bear Lake drainage basin were undertaken to provide a geologic context for interpretation of cores taken from deposits beneath Bear Lake, which sometimes receives water and sediment from the glaciated Bear River and sometimes only from the small drainage basin of Bear Lake itself. Analyses of core sediments by others are directed at (1) constructing a high-resolution climate record for the Bear Lake area during the late Pleistocene and Holocene, and (2) investigating the sources and weathering history of sediments in the drainage basin. Surficial deposits in the upper Bear River and Bear Lake drainage basins are different in their overall compositions, although they do overlap. In the upper Bear River drainage, Quaternary deposits derived from glaciation of the Uinta Range contain abundant detritus weathered from Precambrian quartzite, whereas unglaciated tributaries downstream mainly contribute finer sediment weathered from much younger, more friable sedimentary rocks. In contrast, carbonate rocks capped by a carapace of Tertiary sediments dominate the Bear Lake drainage basin.

Late Cenozoic sea-level changes and the onset of glaciation: impact on continental slope progradation off eastern Canada

USGS Publications Warehouse

Piper, D.J.W.; Normark, W.R.

1989-01-01

Late Cenozoic sedimentation from four varied sites on the continental slopes off southeastern Canada has been analysed using high-resolution airgun multichannel seismic profiles, supplemented with some single channel data. Biostratigraphic ties are available to exploratory wells at three of the sites. Uniform, slow accumulation of hemipelagic sediments was locally terminated by the late Miocene sea-level lowering, which is also reflected in changes in foraminiferan faunas on the continental shelf. Data are very limited for the early Pliocene but suggest a return to slow hemipelagic sedimentation. At the beginning of the late Pliocene, there was a change in sedimentation style marked by a several-fold increase in accumulation rates and cutting of slope valleys. This late Pliocene cutting of slope valleys corresponds to the onset of late Cenozoic growth of the Laurentian Fan and the initiation of turbidite sedimentation on the Sohm Abyssal Plain. Although it corresponds to a time of sea-level lowering, the contrast with the late Miocene lowstand indicates that there must also have been a change in sediment delivery to the coastline, perhaps as a result of increased rainfall or development of valley glaciers. High sedimentation rates continued into the early Pleistocene, but the extent of slope dissection by gullies increased. Gully-cutting episodes alternated with sediment-draping episodes. Throughout the southeastern Canadian continental margin, there was a change in sedimentation style in the middle Pleistocene that resulted from extensive ice sheets crossing the continental shelf and delivering coarse sediment directly to the continental slope. ?? 1989.

Sedimentologic and Stratigraphic Aspects of Late Quaternary (<14 cal. ka?) Valley Fill (Paleo-Roanoke River) Beneath the Barrier Islands of the Outer Banks, North Carolina, USA

NASA Astrophysics Data System (ADS)

Farrell, K. M.; Brooks, R. W.

2002-12-01

Provided here is a preliminary interpretation of the late Pleistocene (<14 cal. ka) facies succession that infilled the paleo-Roanoke River valley, and its transition into the overlying barrier island complex beneath the Outer Banks of North Carolina. Previous work (e.g. Riggs and others, 1992) reported that the Albemarle Embayment of eastern N.C. is underlain by a series of Pleistocene paleovalley complexes and provided hypotheses to test regarding valley distribution, sea level changes, and the ages of facies and sequences generated in response to coastal evolution. This report provides stratigraphic and sedimentologic criteria to support collaborative interpretations of eight cores acquired by a coastal geology cooperative research program on the Outer Banks to test these hypotheses. In cores OBX-02, 03, and 05, the late Quaternary (<14 cal. ka) fill is about 41 m thick. Here it erosionally overlies a bioturbated marine shelf deposit (OBX-2, 3, 5) that Wehmiller (personal communication) correlated (at OBX-05, depth -41 m) with the early/middle Pleistocene aminozone, AZ-4 (see Riggs and others, 1992). Above this, the late Quaternary fill (in cores OBX-02, 03, 05, 06) includes a succession of four facies units: 1) a basal sandy gravel (<6 m), 2) a dark gray complexly interbedded mud and gravel (<9 m), 3) bioturbated muddy sand (<15 m), and 4) an upward fining sand, with a basal gravel (<15 m). (Dimensional aspects of these units remain undefined until integration with GPR and seismic profiles). Six radiocarbon dates (from Thieler, personal communication) on samples from unit 2 (OBX-05: from -32.3, -33.6 and -35 m; OBX-02: from -27.7, -33.0, and -33.0 m) fall within the range 10 to 14 cal. ka. These were deposited during the Younger Dryas (Mallinson and others, Thieler, personal communications). Stratigraphic relations suggest that unit 1, although not dated, was deposited at the onset of this phase of global cooling. Unit 1, interpreted as fluvial thalweg and

Late Neogene and Quaternary evolution of the northern Albemarle Embayment (mid-Atlantic continental margin, USA)

USGS Publications Warehouse

Mallinson, D.; Riggs, S.; Thieler, E.R.; Culver, S.; Farrell, K.; Foster, D.S.; Corbett, D.R.; Horton, B.; Wehmiller, J.F.

2005-01-01

Seismic surveys in the eastern Albemarle Sound, adjacent tributaries and the inner continental shelf define the regional geologic framework and provide insight into the sedimentary evolution of the northern North Carolina coastal system. Litho- and chronostratigraphic data are derived from eight drill sites on the Outer Banks barrier islands, and the Mobil #1 well in eastern Albemarle Sound. Within the study area, parallel-bedded, gently dipping Miocene beds occur at 95 to > 160 m below sea level (m bsl), and are overlain by a southward-thickening Pliocene unit characterized by steeply inclined, southward-prograding beds. The lower Pliocene unit consists of three seismic sequences. The 55–60 m thick Quaternary section unconformably overlies the Pliocene unit, and consists of 18 seismic sequences exhibiting numerous incised channel-fill facies. Shallow stratigraphy (< 40 m bsl) is dominated by complex fill patterns within the incised paleo-Roanoke River valley. Radiocarbon and amino-acid racemization (AAR) ages indicate that the valley-fill is latest Pleistocene to Holocene in age. At least six distinct valley-fill units are identified in the seismic data. Cores in the valley-fill contain a 3–6 m thick basal fluvial channel deposit that is overlain by a 15 m thick unit of interlaminated muds and sands of brackish water origin that exhibit increasing marine influence upwards. Organic materials within the interlaminated deposits have ages of 13–11 cal. ka. The interlaminated deposits within the valley are overlain by several units that comprise shallow marine sediments (bay-mouth and shoreface environments) that consist of silty, fine- to medium-grained sands containing open neritic foraminifera, suggesting that this area lacked a fronting barrier island system and was an open embayment from ∼10 ka to ∼4.5 ka. Seismic data show that initial infilling of the paleo-Roanoke River valley occurred from the north and west during the late Pleistocene and early

Ottawa, Quebec Province, Canada and Glaciated Landscape

NASA Image and Video Library

1973-06-22

SL2-05-380 (22 June 1973) --- Ottawa, in the province of Ontario, (46.5N, 75.5W) is the capital of Canada and can be seen near the bottom of this scene on the Ottawa River. The region shown lies within the Canadian Shield. The glaciated surface of the land is underlain by lower Precambrian granite and sedimentary rock. Long fractures within these crystalline rocks have, in places, been carved out by glacial action. The resultant depressions are often water filled bogs and lakes. Photo credit: NASA

Can dryland geoproxy data generate Quaternary palaeoclimate and palaeoenvironmental records?

NASA Astrophysics Data System (ADS)

Thomas, David S. G.

2017-04-01

Dryland regions present many challenges for robustly reconstructing late Quaternary palaeoenvironments and palaeoclimates, not least a common deficit, or considerable spatial variability, in the availability of high resolution biological proxy data sources. Substantial advances have been made in some regions in recent years, through the exploitation of new high resolution biomarker and isotope records, for example from hyrax middens (e.g. Chase et al., 2012) and from offshore sediments (e.g. Collins et al., 2014). In others however, suitable data sources for these approaches are absent, so these approaches are not available or if data are applied from distant sources, subject to risks of excessive spatial extrapolation of records in environmental contexts where environmental gradients are steep and variability is common (Thomas and Burrough, 2012, Thomas et al., 2013). In these contexts, geoproxy records, derived from the analysis of landforms and their associated sediments, are often utilised in dryland Quaternary research (e.g. Burrough and Thomas 2009, Stone and Thomas, 2013, Thomas, 2013, Lancaster et al., 2015), but with a number of associated difficulties (e.g. Chase, 2009). This paper examines these difficulties and then explores different approaches to the analysis of Quaternary landform records. It is argued that geoproxies with chronometric control, usually provided by OSL dating, have considerable potential to improve data on Quaternary environmental and climate dynamics, if records are interpreted effectively and appropriately (e.g. Bailey and Thomas, 2014, Thomas and Burrough, 2016). Examples of challenges and new approaches will be drawn from aeolian and fluvial domains, and from research in Africa, Australia and Arabia. Bailey RM, Thomas DSG 2014 Earth Surf. Proc. Landf. 39, 614-631. Burrough SL, Thomas DSG 2009. Geomorphology 103, 285-298. Chase, B 2009. Earth-Sci Rev. 93, 31-45. Chase BM et al. 2010 Quat. Sci. Rev. 56, 107-125. Collins JA et al

Late Pleistocene glacial stratigraphy of the Kumara-Moana region, West Coast of South Island, New Zealand

NASA Astrophysics Data System (ADS)

Barrows, Timothy T.; Almond, Peter; Rose, Robert; Keith Fifield, L.; Mills, Stephanie C.; Tims, Stephen G.

2013-08-01

On the South Island of New Zealand, large piedmont glaciers descended from an ice cap on the Southern Alps onto the coastal plain of the West Coast during the late Pleistocene. The series of moraine belts and outwash plains left by the Taramakau glacier are used as a type section for interpreting the glacial geology and timing of major climatic events of New Zealand and also as a benchmark for comparison with the wider Southern Hemisphere. In this paper we review the chronology of advances by the Taramakau glacier during the last or Otira Glaciation using a combination of exposure dating using the cosmogenic nuclides 10Be and 36Cl, and tephrochronology. We document three distinct glacial maxima, represented by the Loopline, Larrikins and Moana Formations, separated by brief interstadials. We find that the Loopline Formation, originally attributed to Oxygen Isotope Chronozone 4, is much younger than previously thought, with an advance culminating around 24,900 ± 800 yr. The widespread late Pleistocene Kawakawa/Oruanui tephra stratigraphically lies immediately above it. This Formation has the same age previously attributed to the older part of the Larrikins Formation. Dating of the Larrikins Formation demonstrates there is no longer a basis for subdividing it into older and younger phases with an advance lasting about 1000 years between 20,800 ± 500 to 20,000 ± 400 yr. The Moana Formation represents the deposits of the last major advance of ice at 17,300 ± 500 yr and is younger than expected based on limited previous dating. The timing of major piedmont glaciation is restricted to between ˜25,000 and 17,000 yr and this interval corresponds to a time of regionally cold sea surface temperatures, expansion of grasslands at the expense of forest on South Island, and hemisphere wide glaciation.

Subsurface stratigraphy and geochemistry of late Quaternary evaporites, Searles Lake, California, with a section on radiocarbon ages of stratigraphic units

USGS Publications Warehouse

Smith, George I.; Stuiver, Minze

1979-01-01

Searles Lake is a dry salt pan, about 100 km 2 in area, that lies on the floor of Searles Valley, in the desert of southeast California. Several salt bodies of late Quaternary age lie beneath the surface, mostly composed of sodium and potassium carbonate, sulfate, chloride, and borate minerals. Mud layers separate the salt bodies, which contain interstitial brine that is the source of large quantities of industrial chemicals. The value of annual production from the deposit exceeds $30 million; total production to date exceeds $1 billion. The salts and muds were deposited during Pleistocene and Holocene times by a series of large lakes (200 m maximum depth, 1,000 km 2 maximum area) that fluctuated in size in response to climatic change. Salts were deposited during major dry (interpluvial) episodes, muds during wet (pluvial) episodes that correlate with glacial advances in other parts of North America and the world. Data based on cores from the deposit are used in this paper to establish the stratigraphy of the deposit, the chemical and mineral compositions of successive units, and the total quantities of components contained by them. These parameters are then used to determine the geochemical evolution of the sedimentary layers. The results provide a refined basis for reconstructing the limnology of Searles Lake and the regional climate during late Quaternary time. Six main stratigraphic units were distinguished and informally named earlier on the basis of their dominant composition: Unit Typical thickness 14C age, uncorrected (in meters) (years B.P.) Overburden Mud 7 0 to >3,500 Upper Salt 15 >3,500 to 10,500 Parting Mud 4 10,500 to 24,000 Lower Salt 12 24,000 to 32,500 Bottom Mud 30 32,500 to 130,000 Mixed Layer 200+ > 130,000 (The age of 130,000 years for the Mixed Layer is based on extrapolated sedimentation rates.) The Lower Salt is subdivided into seven salt units (S-l to S-7) and six mud units (M-2 to M-7), the Mixed Layer into six units (A to F). For each

Time scale bias in erosion rates of glaciated landscapes

PubMed Central

Ganti, Vamsi; von Hagke, Christoph; Scherler, Dirk; Lamb, Michael P.; Fischer, Woodward W.; Avouac, Jean-Philippe

2016-01-01

Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time. PMID:27713925

Time scale bias in erosion rates of glaciated landscapes.

PubMed

Ganti, Vamsi; von Hagke, Christoph; Scherler, Dirk; Lamb, Michael P; Fischer, Woodward W; Avouac, Jean-Philippe

2016-10-01

Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time.

Onset and Multiple Fluctuations of Holocene Glaciation in the Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Bowerman, N. D.; Clark, D. H.

2004-12-01

Multiple sediment cores from two paternoster tarns (First and Second lakes) in North Fork Big Pine Creek, Sierra Nevada, preserve the most detailed and complete record of Holocene glaciation yet recovered in the range; they indicate that the glacier was absent during the early Holocene, reformed in the late Holocene, and experienced several expansions and contractions, culminating with the Matthes maximum during the last ˜200 years. The lakes are fed by outwash from the Palisade Glacier, the largest ( ˜1.3 km2) and presumably longest-lived glacier in the Sierra Nevada, and capture essentially all of the rock flour produced by the glacier. Distinct late-Holocene (Matthes) and late-Pleistocene (Recess Peak) moraines lie between the modern glacier and the lakes. Thus, the lakes have received continuous sedimentation since the retreat of the Tioga glacier ( ˜15,000 yr B.P.), and therefore capture rock flour related to all subsequent advances. First and Second lakes occupy relatively deep bedrock basins at 3036 m and 3066 m asl., respectively. Third Lake, a shallow (<3 m deep), moraine-dammed lake that lies directly above Second Lake, is the only lake between the Palisade Glacier and the lower lakes. As such, it captures the coarsest (sand/gravel bedload) outwash, but abundant suspended sediment (silt/clay) continues to the lower lakes. We cored the lakes using both Reasoner and Livingston corers, to sediment depths of up to ˜5 m. The deepest cores bottomed in coarse, inorganic sand and silt that we interpret as outwash or slopewash related to Tioga deglaciation. Magnetic susceptibility (MS) analyses of the sediment cores indicate that both lakes record multiple late-Holocene peaks in MS, with the most recent peak being the largest. They also retain outwash near the base related to the more extensive Recess Peak advance. MS peaks in Sierran lakes typically indicate greater abundances of clastic (vs. organic) sediment. The peaks in our cores thus imply 4-5 periods of

Quaternary volcanic evolution in the continental back-arc of southern Mendoza, Argentina

NASA Astrophysics Data System (ADS)

May, Venera R.; Chivas, Allan R.; Dosseto, Anthony; Honda, Masahiko; Matchan, Erin L.; Phillips, David; Price, David M.

2018-07-01

The Payenia Basaltic Province (PBP) is the largest and the northernmost of the Quaternary back-arc Patagonian basaltic provinces in South America. In the last 10 years, several studies have investigated either, the geochemistry or the geochronology of this basaltic province. However, only a few investigations have focused on the two aspects simultaneously in order to reconstruct its Quaternary volcanic history. Consequently, this study aims to provide new Quaternary ages and to contribute in understanding how its geochemistry evolved though time. In the current study nine basaltic flows from the PBP in central west Argentina were dated using a combination of cosmogenic surface exposure, 40Ar/39Ar, and thermoluminescence dating methods. Seven flows have Middle to Late Pleistocene ages and two erupted in the Holocene. Using the new ages here inferred and the previously published Quaternary geochronology, together with the available geochemical data, maps of Pleistocene geochemical evolution have been generated. These maps indicate that two geochemically distinct magma types erupted over the same time interval (ca. 1.5 Ma) within the PBP: In the north-eastern part (Nevado volcanic field) of the province, an arc-like signature is distinguishable, whereas the southern part of the PBP (Río Colorado volcanic field) exhibits an intraplate, Ocean Island Basalt (OIB)-like signature. The arc-like signature decreases in the Early to Middle Pleistocene as indicated by a reduction in Ba/La and La/Ta values in the Nevado volcanic field. At ca. 0.25 Ma a similar disparity has been inferred between two volcanic fields on the western part of the PBP, one erupting lavas with arc-like characteristics and the other with OIB-like signatures, despite being only tens of kilometres apart. Holocene volcanism is restricted to the western side of the Payún Matrú volcanic field and is dominated by OIB-like signatures, notably high Ta/Hf and low Ba/La and La/Ta values.

Microfaunal analysis of late Quaternary deposits of the northern Bering Sea.

USGS Publications Warehouse

McDougall, K.

1982-01-01

Holocene microfaunal associations and distribution patterns define three inner-shelf (1-20m) biofacies in Norton Sound, northern Bering Sea. The Holocene facies relations are the basis for interpreting early Holocene and late Pleistocene environmental conditions in the NE Bering Sea area. Norton Sound cores provide evidence of two marine transgressions and a varying river input.-from Author

Export of nutrient rich Northern Component Water preceded early Oligocene Antarctic glaciation

NASA Astrophysics Data System (ADS)

Coxall, Helen K.; Huck, Claire E.; Huber, Matthew; Lear, Caroline H.; Legarda-Lisarri, Alba; O'Regan, Matt; Sliwinska, Kasia K.; van de Flierdt, Tina; de Boer, Agatha M.; Zachos, James C.; Backman, Jan

2018-03-01

The onset of the North Atlantic Deep Water formation is thought to have coincided with Antarctic ice-sheet growth about 34 million years ago (Ma). However, this timing is debated, in part due to questions over the geochemical signature of the ancient Northern Component Water (NCW) formed in the deep North Atlantic. Here we present detailed geochemical records from North Atlantic sediment cores located close to sites of deep-water formation. We find that prior to 36 Ma, the northwestern Atlantic was stratified, with nutrient-rich, low-salinity bottom waters. This restricted basin transitioned into a conduit for NCW that began flowing southwards approximately one million years before the initial Antarctic glaciation. The probable trigger was tectonic adjustments in subarctic seas that enabled an increased exchange across the Greenland-Scotland Ridge. The increasing surface salinity and density strengthened the production of NCW. The late Eocene deep-water mass differed in its carbon isotopic signature from modern values as a result of the leakage of fossil carbon from the Arctic Ocean. Export of this nutrient-laden water provided a transient pulse of CO2 to the Earth system, which perhaps caused short-term warming, whereas the long-term effect of enhanced NCW formation was a greater northward heat transport that cooled Antarctica.

Late Quaternary climatic vegetational shifts in an ecological transition zone of northern Madagascar: insights from genetic analyses of two endemic rodent species.

PubMed

Rakotoarisoa, J-E; Raheriarisena, M; Goodman, S M

2013-05-01

The Loky-Manambato region, located in northern Madagascar, is a biotically rich contact zone between different forest biomes. Local current forest cover is composed of both humid and dry formations, which show elevational stratification. A recent phylogeographical study of a regional dry forest rodent, Eliurus carletoni (subfamily Nesomyinae), found genetic evidence of forest contractions between 18 750 and 7500 years BP, which based on extrapolation of the pollen subfossil record, was thought to be associated with an expansion of local humid forests. Herein, we conduct a genetic test of this hypothesis and focused on populations on two neighbouring massifs of forest-dependent rodent species, one associated with low-elevation dry forests (E. carletoni) and the other with higher elevation humid forests (Eliurus tanala). Using mitochondrial markers and a combination of traditional and coalescent-based phylogeographical, historical demographic and population genetic methods, we found evidence of historical connections between populations of E. tanala. Adjacent populations of E. carletoni and E. tanala exhibit opposite historical demographic patterns, and for both, evidence suggests that historical demographic events occurred within the last 25 000 years BP. These findings strongly support the proposed late Quaternary shifts in the floristic composition of the Loky-Manambato region. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

Surface exposure chronology of the Waimakariri glacial sequence in the Southern Alps of New Zealand: Implications for MIS-2 ice extent and LGM glacial mass balance

NASA Astrophysics Data System (ADS)

Rother, Henrik; Shulmeister, James; Fink, David; Alexander, David; Bell, David

2015-11-01

During the late Quaternary, the Southern Alps of New Zealand experienced multiple episodes of glaciation with large piedmont glaciers reaching the coastal plains in the west and expanding into the eastern alpine forelands. Here, we present a new 10Be exposure age chronology for a moraine sequence in the Waimakariri Valley (N-Canterbury), which has long been used as a reference record for correlating glacial events across New Zealand and the wider Southern Hemisphere. Our data indicate that the Waimakariri glacier reached its maximum last glaciation extent prior to ∼26 ka well before the global last glaciation maximum (LGM). This was followed by a gradual reduction in ice volume and the abandonment of the innermost LGM moraines at about 17.5 ka. Significantly, we find that during its maximum extent, the Waimakariri glacier overflowed the Avoca Plateau, previously believed to represent a mid-Pleistocene glacial surface (i.e. MIS 8). At the same time, the glacier extended to a position downstream of the Waimakariri Gorge, some 15 km beyond the previously mapped LGM ice limit. We use a simple steady-state mass balance model to test the sensitivity of past glacial accumulation to various climatic parameters, and to evaluate possible climate scenarios capable of generating the ice volume required to reach the full local-LGM extent. Model outcomes indicate that under New Zealand's oceanic setting, a cooling of 5 °C, assuming modern precipitation levels, or a cooling of 6.5 °C, assuming a one third reduction in precipitation, would suffice to drive the Waimakariri glacier to the eastern alpine forelands (Canterbury Plains). Our findings demonstrate that the scale of LGM glaciation in the Waimakariri Valley and adjacent major catchments, both in terms of ice volume and downvalley ice extent, has been significantly underestimated. Our observation that high-lying glacial surfaces, so far believed to represent much older glacial episodes, were glaciated during the LGM

Stable isotopes in collagen and Late Quaternary carnivore palaeoecology

NASA Astrophysics Data System (ADS)

Bocherens, Hervé

2010-05-01

Several taxa of large carnivores co-occurred during the late Pleistocene in the steppe-tundra ecosystem, such as wolf Canis lupus, cave lion Panthera leo spelaea, cave hyaena Crocuta crocuta spelaea, brown bear Ursus arctos and cave bear Ursus spelaeus and Ursus ingressus. This abundance of taxa belonging to the same guild raises questions about niche partitioning, especially in terms of dietary specialization and prey selection. Observations of the dietary ecology of the extant relatives of these late Pleistocene carnivores does not provide unambiguous answers as these populations live under very different environmental conditions where other potential prey species are present, but it appears that most of these modern large carnivores are relatively flexible in their prey selection. Palaeontological investigations dealing with faunal associations and activity marks on fossil bones also have their limitations, such as taphonomic biases (palimpsests rather than biological associations) and do not allow the quantification of consumption of various preys. In contrast, carbon and nitrogen isotopic signatures of bone collagen depend directly on those of the average diet. Since different potential prey species occurring in the steppe-tundra exhibit consistent isotopic differences for these chemical elements, it is possible to relate the carbon and nitrogen isotopic signatures measured in fossil carnivores with the preferential consumption of some prey species. Some amount of quantification can be provided using modified versions of mixing models developed for modern ecosystems. In addition, this isotopic approach is individual-based and it is therefore possible to investigate intra- and inter-population differences in prey selection, as well as possible chronological trends and differences linked to genetic differences by combining isotopic and ancient DNA studies on the same material. The isotopic approach has already shown that among the tested large carnivores, cave

Origin, Extent, and Thickness of Quaternary Geologic Units in the Willamette Valley, Oregon

USGS Publications Warehouse

O'Connor, Jim E.; Sarna-Wojcicki, Andrei M.; Wozniak, Karl C.; Polette, Danial J.; Fleck, Robert J.

2001-01-01

Stratigraphic and chronologic information collected for Quaternary deposits in the Willamette Valley, Oregon, provides a revised stratigraphic framework that serves as a basis for a 1:250,000-scale map, as well as for thickness estimates of widespread Quaternary geologic units. We have mapped 11 separate Quaternary units that are differentiated on the basis of stratigraphic, topographic, pedogenic, and hydrogeologic properties. In summation, these units reflect four distinct episodes in the Quaternary geologic development of the Willamette Valley: 1) Fluvial sands and gravels that underlie terraces flanking lowland margins and tributary valleys were probably deposited between 2.5 and 0.5 million years ago. They are the oldest widespread surficial Quaternary deposits in the valley. Their present positions and preservation are undoubtedly due to postdepositional tectonic deformation - either by direct tectonic uplift of valley margins, or by regional tectonic controls on local base level. 2) Tertiary and Quaternary excavation or tectonic lowering of the Willamette Valley accommodated as much as 500 m (meters) of lacustrine and fluvial fill. Beneath the lowland floor, much of the upper 10 to 50 m of fill is Quaternary sand and gravel deposited by braided channel systems in subhorizontal sheets 2 to 10 m thick. These deposits grade to gravel fans 40 to 100 m thick where major Cascade Range rivers enter the valley and are traced farther upstream as much thinner valley trains of coarse gravel. The sand and gravel deposits have ages that range from greater than 420,000 to about 12,000 years old. A widely distributed layer of sand and gravel deposited at about 12 ka (kiloannum, thousands of years before the present) is looser and probably more permeable than older sand and gravel. Stratigraphic exposures and drillers' logs indicate that this late Pleistocene unit is mostly between 5 and 20 m thick where it has not been subsequently eroded by the Willamette River and its

Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation

PubMed Central

Graham, Alastair G. C.; Kuhn, Gerhard; Meisel, Ove; Hillenbrand, Claus-Dieter; Hodgson, Dominic A.; Ehrmann, Werner; Wacker, Lukas; Wintersteller, Paul; dos Santos Ferreira, Christian; Römer, Miriam; White, Duanne; Bohrmann, Gerhard

2017-01-01

The history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies. PMID:28303885

Response of surface processes to climatic change in the dunefields and Loess Plateau of North China during the late Quaternary

USGS Publications Warehouse

Lu, H.; Mason, J.A.; Stevens, T.; Zhou, Y.; Yi, S.; Miao, X.

2011-01-01

This paper draws on recent optically stimulated luminescence (OSL) dating to evaluate the long-held assumption that dust accumulation rates in the Loess Plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time, because both are controlled by the strength of the Asian monsoons and also possibly because the dunefields are proximal loess sources. The results show there is little evidence that high rates of loess accumulation coincided with well-dated episodes of extensive dune activity in the Mu Us, Otindag, and Horqin dunefields, at 11-8ka and 1-0ka. Explanations for the apparent lack of coupling include local variation in the trapping of dust and post-depositional preservation of the loess and dune sediments, in response to varying local environmental conditions. In addition, a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields. The results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale. The dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale, but the timing of late Quaternary dune activity, along with a variety of other evidence, indicates that moisture changes in many of the drylands of northern China may not be in phase with precipitation in core regions of the Asian monsoons. ?? 2011 John Wiley & Sons, Ltd.

Stratigraphical evidence of late Amazonian periglaciation and glaciation in the Astapus Colles region of Mars

NASA Astrophysics Data System (ADS)

Soare, Richard J.; Osinski, Gordon R.

2009-07-01

Recent modeling of the meteorological conditions during and following times of high obliquity suggests that an icy mantle could have been emplaced in western Utopia Planitia by atmospheric deposition during the late Amazonian period [Costard, F.M., Forget, F., Madeleine, J.B., Soare, R.J., Kargel, J.S., 2008. Lunar Planet. Sci. 39. Abstract 1274; Madeleine, B., Forget, F., Head, J.W., Levrard, B., Montmessin, F., 2007. Lunar Planet. Sci. 38. Abstract 1778]. Astapus Colles (ABa) is a late Amazonian geological unit - located in this hypothesized area of accumulation - that comprises an icy mantle tens of meters thick [Tanaka, K.L., Skinner, J.A., Hare, T.M., 2005. US Geol. Surv. Sci. Invest., Map 2888]. For the most part, this unit drapes the early Amazonian Vastitas Borealis interior unit (ABvi); to a lesser degree it overlies the early Amazonian Vastitas Borealis marginal unit (ABvm) and the early to late Hesperian UP plains unit HBu2 [Tanaka, K.L., Skinner, J.A., Hare, T.M., 2005. US Geol. Surv. Sci. Invest., Map 2888]. Landscapes possibly modified by late-Amazonian periglacial processes [Costard, F.M., Kargel, J.S., 1995. Icarus 114, 93-112; McBride, S.A., Allen, C.C., Bell, M.S., 2005. Lunar Planet. Sci. 36. Abstract 1090; Morgenstern, A., Hauber, E., Reiss, D., van Gasselt, S., Grosse, G., Schirrmeister, L., 2007. J. Geophys. Res. 112, doi:10.1029/2006JE002869. E06010; Seibert, N.M., Kargel, J.S., 2001. Geophys. Res. Lett. 28, 899-902; Soare, R.J., Kargel, J.S., Osinski, G.R., Costard, F., 2007. Icarus 191, 95-112; Soare, R.J., Osinski, G.R., Roehm, C.L., 2008. Earth Planet. Sci. Lett. 272, 382-393] and glacial processes [Milliken, R.E., Mustard, J.F., Goldsby, D.L., 2003. J. Geophys. Res. 108 (E6), doi:10.1029/2002JE002005. 5057; Mustard, J.F., Cooper, C.D., Rifkin, M.K., 2001. Nature 412, 411-414; Tanaka, K.L., Skinner, J.A., Hare, T.M., 2005. US Geol. Surv. Sci. Invest., Map 2888] have been reported within the region. Researchers have assumed that the

Evaluation of simple geochemical indicators of aeolian sand provenance: Late Quaternary dune fields of North America revisited

USGS Publications Warehouse

Muhs, Daniel

2017-01-01

Dune fields of Quaternary age occupy large areas of the world's arid and semiarid regions. Despite this, there has been surprisingly little work done on understanding dune sediment provenance, in part because many techniques are time-consuming, prone to operator error, experimental, highly specialized, expensive, or require sophisticated instrumentation. Provenance of dune sand using K/Rb and K/Ba values in K-feldspar in aeolian sands of the arid and semiarid regions of North America is tested here. Results indicate that K/Rb and K/Ba can distinguish different river sands that are sediment sources for dunes and dune fields themselves have distinctive K/Rb and K/Ba compositions. Over the Basin and Range and Great Plains regions of North America, the hypothesized sediment sources of dune fields are reviewed and assessed using K/Rb and K/Ba values in dune sands and in hypothesized source sediments. In some cases, the origins of dunes assessed in this manner are consistent with previous studies and in others, dune fields are found to have a more complex origin than previously thought. Use of K/Rb and K/Ba for provenance studies is a robust method that is inexpensive, rapid, and highly reproducible. It exploits one of the most common minerals found in dune sand, K-feldspar. The method avoids the problem of using simple concentrations of key elements that may be subject to interpretative bias due to changes in mineralogical maturity of Quaternary dune fields that occur over time.

Aminostratigraphy of surface and subsurface Quaternary sediments, North Carolina coastal plain, USA

USGS Publications Warehouse

Wehmiller, John F.; Thieler, E. Robert; Miller, D.; Pellerito, V.; Bakeman, Keeney V.; Riggs, S.R.; Culver, S.; Mallinson, D.; Farrell, K.M.; York, L.L.; Pierson, J.; Parham, P.R.

2010-01-01

, yielding a total of at least eight stratigraphically and statistically distinct aminozones. Kinetic modeling, supplemented with local calibration, indicates that these aminozones represent depositional events ranging from ∼80 ka to nearly 2 Ma. Three prominent seismic reflections are interpreted to represent the base of the early, middle, and late Pleistocene, respectively, roughly 2 Ma, 800 ka, and 130 ka. The large number of samples and the available stratigraphic control provide new insights into the capabilities and limitations of aminostratigraphic methods in assessing relative and numerical ages of Atlantic Coastal Plain Quaternary deposits.

Timing and process of river and lake terrace formation in the Kyrgyz Tien Shan

NASA Astrophysics Data System (ADS)

Burgette, Reed J.; Weldon, Ray J.; Abdrakhmatov, Kanatbek Ye.; Ormukov, Cholponbek; Owen, Lewis A.; Thompson, Stephen C.

2017-03-01

Well-preserved flights of river and lake terraces traverse an actively deforming rangefront, and form a link between glaciated mountains and a large intermontane lake in the Issyk-Kul basin of the Kyrgyz Tien Shan. We investigated the history and geometry of these lake and river terraces using geologic mapping, surveying, and radiocarbon and terrestrial cosmogenic nuclide dating. A prominent late Pleistocene highstand of the lake occurred over at least the period of 43-25 ka, followed by a period of deep regression and subsequent rise of the lake to the modern sill level in the late Holocene. Major aggradation of the most prominent latest Quaternary river terrace along the Ak-Terek and Barskaun rivers likely started at ∼70-60 ka, coincident to the local last glacial maximum in this region. In contrast to some models of aggradation and incision, the rivers appear to have stayed near the top of the fill for >20 ka, incising subtly below the top of this fill by ∼37 ka, locally. Deep incision likely did not occur until the peak deglaciation in the latest Pleistocene. Older dated terrace surfaces are consistent with one major terrace-forming event per glacial, constant deformation and incision rates, and typical fluvial gradients lower than the modern incising streams. The dating confirms regional terrace correlations for the most prominent late Quaternary terraces, but correlating higher terraces is complicated by spatially varying uplift rates and preferential terrace preservation between basins in the Tien Shan.

Late Quaternary vegetational and climate dynamics in northeastern Brazil, inferences from marine core GeoB 3104-1

NASA Astrophysics Data System (ADS)

Behling, Hermann; W. Arz, Helge; Pätzold, Jürgen; Wefer, Gerold

2000-06-01

Late Quaternary paleoenvironments from northeastern (NE) Brazil have been studied by pollen analysis of marine sediment. The studied core GeoB 3104-1 (3°40' S, 37°43' W, 767 m b.s.l.) from the upper continental slope off NE Brazil is 517 cm long and >42,000 14C yr BP old. Chronological control was obtained by 12 radiocarbon (AMS) dates from individuals of the foraminiferal species Globigerinoides sacculifer. Modern pollen analogs were received from 15 river, lake and forest soil surface samples from NE Brazil. Marine pollen dates indicate the predominance of semi-arid caatinga vegetation in NE Brazil during the recorded period between >42,000 and 8500 14C yr BP. The increased fluvial input of terrigenous material, with high concentrations of pollen and specially fern spores, into the marine deposits, about 40,000, 33,000 and 24,000 14C yr BP and between 15,500 and 11,800 14C yr BP, indicate short-term periods of strong rainfall on the NE Brazilian continent. The expansion of mountain, floodplain and gallery forests characterize the interval between 15,500 and 11,800 14C yr BP as the wettest recorded period in NE Brazil, which allowed floristic exchanges between Atlantic rain forest and Amazonian rain forest, and vice versa. The paleodata from core GeoB 3104-1 confirm the, in general, dry pre-Last Glacial Maximum (LGM) and LGM conditions and the change to wet Lateglacial environments in tropical South America. The annual movement of the intertropical convergence zone over NE Brazil, the strong influence of the Antarctic cold fronts and changes of the high-pressure cell over the southern Atlantic, may explain the very wet Lateglacial period in NE Brazil. The documented NE Brazilian short-term signals correlate with the documented Dansgaard-Oeschger cycles and Heinrich events from the northern Hemisphere and suggest strong teleconnections.

Late Quaternary Paleoclimatic History of Tropical South America From Drilling Lake Titicaca and the Salar de Uyuni

NASA Astrophysics Data System (ADS)

Baker, P. A.; Fritz, S. C.; Seltzer, G. O.; Rigsby, C. A.; Lowenstein, T. K.; Ku, R.

2003-12-01

Seven drill cores were recovered from Lake Titicaca during the NSF/ICDP/DOSECC drilling expedition of 2001. Sub-lake floor drilling depths ranged from 53 to 139 m; water depths ranged from 40 to 232 m; recoveries ranged from 75 to 112 percent. Our most detailed multi-proxy analyses to date have been done on Core 2B raised from the central basin of the lake from 232 m water depth, drilled to 139.26 m sub-lakefloor with 140.61 m of total sediment recovered (101 percent). A basal age of 200 Ka is estimated by linear extrapolation from radiocarbon measurements in the upper 25 m of core; Ar-Ar dating of interbedded ashes and U/Th dating of abiogenic aragonites are underway. The volume and lake level of Lake Titicaca have undergone large changes several times during the late Quaternary. Proxies for these water level changes (each of different fidelity) include the ratio of planktonic-to-benthic diatoms, sedimentary carbonate content, and stable isotopic content of organic carbon. The most recent of these changes, has been described previously from earlier piston cores. In the early and middle Holocene the lake fell below its outlet to 85 m below modern level, lake salinity increased several-fold, and the Salar de Uyuni, which receives overflow from Titicaca, dessicated. In contrast, Lake Titicaca was deep, fresh, and overflowing (southward to the Salar de Uyuni) throughout the last glacial maximum from prior to 25,000 BP to at least 15,000 BP. According to extrapolated ages, the penultimate major lowstand of Lake Titicaca occurred prior to 60,000 BP, when seismic evidence indicates that lake level was about 200 m lower than present. Near the end of this lowstand, the lake also became quite saline. There are at least three, and possibly more, older lowstands, each separated temporally by periods in which the lake freshened dramatically and overflowed. These results will be compared with results from previous drilling in the Salar de Uyuni.

A New age Constraint on Sturtian Glaciation: SHRIMP U-Pb zircon geochronology of Neoproterozoic Altungol Formation in Tarim Basin, NW China

NASA Astrophysics Data System (ADS)

Zhou, X.; Li, J.; Li, W.; Wang, H.

2013-12-01

Neoproterozoic glaciations with a wide distribution, punctuated the largely ice-free Precambrian world within tropical latitudes, interpreted as evidence record the cold paleoclimate intervals which made a Snowball Earth with the frozen ocean. More recently, Quruqtagh of Northeast Tarim Basin, Northwest China, catches the increasing eyes, not only because of its three or four Neoproterzoic glacial periods in China, but also its tectonic significance for breakup of Rodinia supercontinent. There are many Neoproterozoic glaciation strata exposures in Quruqtagh. The Nanhua System is divided into the Bayisi, Zhaobishan (absent in south aera), Altungol and Tereeken formations. Thick tillites were found in Bayisi, Tereeken and Hankalchough formations, while minor was found in Altungol Formation. After the field investigation of the south Yaerdang Mountain in the South aera, it is suggested that the Altungol Formation in the South aera differs from that the North aera. In the North, it is a set of littoral-neritic clastic facies sediment with few volcanic rocks and marine tillites in the bottom. In South Quruqtagh, it consists of 45m-thick gray-green tillites in the bottom with different size and complex components gravels, volcanic interbed near the top of tillites, overlying strata is cap dolomite of 15m thickness, with abundant drop-stones, the upper is black shales and gray to black thin-interbeded siliceous rock. The reported ages without Altungol glaciation age are all focused on the north Quruqtagh and conversely in South Quruqtagh without reported glaciation age. Based on field investigation of Nanhua System (Cryogenian) in NE Tarim Basin, we offer the first set of Sturtian glaciation age 729.4×6.6Ma, in the form of SHRIMP(sensitive high-resolution ion microprobe) U-Pb zircon age dating of volcanic interbedded near the top of Altungol Formation tillites, South Quruqtagh, which provides a new constraint on the Sturtian glaciation from global perspective. It is a

The interaction between surface processes and tectonics during the late Quaternary in the Middle Volturno River valley (southern Italy): new morpho-stratigraphic constraints from fluvial terraces

NASA Astrophysics Data System (ADS)

Amato, Vincenzo; Patrizio Ciro Aucelli, Pietro; Cesarano, Massimo; Filocamo, Francesca; Giralt, Santiago; Leone, Natalia; Rosskopf, Carmen Maria; Scorpio, Vittoria

2017-04-01

The Middle Volturno River valley is located in the inner part of the Southern Apennines of Italy, between the SW slope of the Matese Massif and the NE slopes of the Caserta mountains and is underlain by Meso-Cenozoic carbonate rocks and Miocene Flysch deposits. The study sector includes the lower Calore River valley and, below the Calore-Volturno confluence, the valley portion that extends until the Triflisco gorge, from Telese village to the Volturno dam. It is generally E-W, NW-SE and NE-SW elongated and characterized by rectilinear and meandering fluvial patterns. The main infilling of the two valley portions is locally preserved as remnants of fluvial terraces hanging over the local base level up to ca. 30-40 m. It is generally interfingered with and covered by several generations of alluvial fan and travertine deposits. New Ar/Ar datings on tephra layers interbedded in the oldest generations of the alluvial fan deposits and new U/Th datings on travertine deposits, allowed to constrain the main infilling to the late Middle and the early Upper Pleistocene. Both deposits are locally covered by the Campanian Ignimbrite Formation (CI, 39 ky BP) and are interested by high-angle faults generated during extensional tectonic phases that affected this sector of the Apennine chain since the Middle Pleistocene. Furthermore, the geomorphological analyses of aerial photos and topographic maps (1:5000 in scale) highlight the presence of a flight of fluvial terraces younger than the CI deposits that can be grouped into four orders. The stratigraphical data, based on field surveys and boreholes analyses, supported by new tephrostratigraphical constraints and literature data, allow to refer the older orders (I and II) to the late Upper Pleistocene. The III and IV orders, instead, can be referred to the early Holocene and historical times, respectively. These chronological constraints allow to hypothesize that the genesis of the I and II orders seem to be driven by late

Multiple states in the late Eocene ocean circulation

NASA Astrophysics Data System (ADS)

Baatsen, M. L. J.; von der Heydt, A. S.; Kliphuis, M.; Viebahn, J.; Dijkstra, H. A.

2018-04-01

The Eocene-Oligocene Transition (EOT) marks a major step within the Cenozoic climate in going from a greenhouse into an icehouse state, with the formation of a continental-scale Antarctic ice sheet. The roles of steadily decreasing CO2 concentrations versus changes in ocean circulation at the EOT are still debated and the threshold for Antarctic glaciation is obscured by uncertainties in global geometry. Here, a detailed study of the late Eocene ocean circulation is carried out using an ocean general circulation model under two slightly different geography reconstructions of the middle-to-late Eocene (38 Ma). Using the same atmospheric forcing, both geographies give a profoundly different equilibrium ocean circulation state. The underlying reason for this sensitivity is the presence of multiple equilibria characterised by either North or South Pacific deep water formation. A possible shift from a southern towards a northern overturning circulation would result in significant changes in the global heat distribution and consequently make the Southern Hemisphere climate more susceptible for significant cooling and ice sheet formation on Antarctica.

Late quaternary geomorphology of the Great Salt Lake region, Utah, and other hydrographically closed basins in the western United States: A summary of observations

NASA Technical Reports Server (NTRS)

Currey, Donald R.

1989-01-01

Attributes of Quaternary lakes and lake basins which are often important in the environmental prehistory of semideserts are discussed. Basin-floor and basin-closure morphometry have set limits on paleolake sizes; lake morphometry and basin drainage patterns have influenced lacustrine processes; and water and sediment loads have influenced basin neotectonics. Information regarding inundated, runoff-producing, and extra-basin spatial domains is acquired directly from the paleolake record, including the littoral morphostratigraphic record, and indirectly by reconstruction. Increasingly detailed hypotheses regarding Lake Bonneville, the largest late Pleistocene paleolake in the Great Basin, are subjects for further testing and refinement. Oscillating transgression of Lake Bonneville began about 28,000 yr B.P.; the highest stage occurred about 15,000 yr B.P., and termination occurred abruptly about 13,000 yr B.P. A final resurgence of perennial lakes probably occurred in many subbasins of the Great Basin between 11,000 and 10,000 yr B.P., when the highest stage of Great Salt Lake (successor to Lake Bonneville) developed the Gilbert shoreline. The highest post-Gilbert stage of Great Salt Lake, which has been one of the few permanent lakes in the Great Basin during Holocene time, probably occurred between 3,000 and 2,000 yr B.P.

Sedimentological controls on gold in a late Pleistocene glacial placer deposit, Cariboo Mining District, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Eyles, Nicholas; Kocsis, Stephen P.

1989-11-01

It is a widely perceived notion that glaciation results in dispersal of mineralized bedrock and that sedimentary concentrates of economic minerals (placers) rarely occur in glaciated basins. This paper describes economic gold placers within late Pleistocene glacial and related fluvial sediments of the Cariboo Mining District in central British Columbia, Canada. The area has been defined as a "giant" gold placer; total production since 1858 is over 93,000 kg. The oldest and volumetrically largest placers occur in fluvial gravels and valley-side fan deposits deposited during a long non-glacial interval from as early as 125,000 to 30,000years B.P. The richest placers are found along bedrock "gutters" in the deepest parts of valleys, indicating repeated fluvial reworking of the valley infills. Braided and "wandering gravel bed" fluvial facies can be identified. Glacial placers, that overlie the fluvial placers, occur within lodgement till complexes deposited below the late Wisconsin Cordilleran ice sheet after 30,000 years B.P. The basal portions of lodgement tills are commonly enriched in gold as a result of incorporation from older gravels. Subglacial meltwaters created a highly effective sluicing system and left lucrative pay zones along meltwater-cut channels on bedrock benches, within intraformational gravels in lodgement till and within "lee-side" deposits down-ice of bedrock highs. "Lee-side" deposits are essentially water-worked talus slopes that accumulated in subglacial cavities. Finally, postglacial "wandering gravel-bed rivers" have repeatedly reworked older placers resulting in rich pay zones at the base of extensive bar platform deposits. Similar sedimentological controls on gold distribution can be identified in other glacial placers of late Cenozoic and Paleozoic age in North America, southern Africa and Australia. A distinction is drawn between these placers, all characterized by coarse-grained, nuggety gold, and the more well-known Precambrian and

Reconstructing late Quaternary palaeosol development and landscape connectivity from combined soil magnetic, geochemical and micromorphological analyses: insights from the Wilgerbosch River, Great Karoo, South Africa.

NASA Astrophysics Data System (ADS)

Oldknow, Chris; Hooke, Janet; Oldfield, Frank

2017-04-01

The characteristics, spatial and temporal patterns and drivers of Quaternary climate change across South Africa remain contentious principally due to the paucity of dated proxy records. River and fan terrace palaeosols may offer an important addition to analysis of spatially pervasive geomorphological landforms (palaeolake shorelines, terraces, dunes) conventionally used to reconstruct patterns of palaeoenvironmental change. In the Great Karoo, alluvial and colluvial exposures in the Wilgerbosch River and several of its tributaries have revealed up to five late Quaternary terraces of varying thickness, extent and pedogenic overprinting which may be of palaeoenvironmental significance. A combination of geochronology (OSL and radiocarbon), soil micromorphology, geochemistry (XRF, XRD) and soil magnetic proxies on both bulk (0-63 μm) and particle size extracts (0-4 and 32-63 μm) from major terrace palaeosols was used in order to establish: 1) changing sediment fluxes and pathways; 2) the characteristics and drivers of palaeosol formation; and 3) evaluate the suitability of these terrace palaeosols as indicators of palaeoenvironmental change. The results are used to test a conceptual model of landscape connectivity. Colluvial (slopewash, head deposits) sedimentation on the valley floors occurred around the time of the LGM due to enhanced regolith production through physical weathering. Soils overprinting these deposits (T1) are goethite-rich attesting to reducing conditions. Incision into T1 resulted in an extensive channel network forming. High concentrations of mafic minerals (Fe, Cr, Ca, Ti) and enhanced ferrimagnetism (XLF > 80) in the 32-63 μm fraction indicated connectivity with slope colluvium proximal to weathering dolerite tors. Fluvial aggradation (T2) occurred as a complex response to this phase of connectivity and terminated in the Late Glacial period (around 17±2.5 ka). The development of a rhizogenic calcrete overprinting T2 indicated an elevated

Synchronous genetic turnovers across Western Eurasia in Late Pleistocene collared lemmings.

PubMed

Palkopoulou, Eleftheria; Baca, Mateusz; Abramson, Natalia I; Sablin, Mikhail; Socha, Paweł; Nadachowski, Adam; Prost, Stefan; Germonpré, Mietje; Kosintsev, Pavel; Smirnov, Nickolay G; Vartanyan, Sergey; Ponomarev, Dmitry; Nyström, Johanna; Nikolskiy, Pavel; Jass, Christopher N; Litvinov, Yuriy N; Kalthoff, Daniela C; Grigoriev, Semyon; Fadeeva, Tatyana; Douka, Aikaterini; Higham, Thomas F G; Ersmark, Erik; Pitulko, Vladimir; Pavlova, Elena; Stewart, John R; Węgleński, Piotr; Stankovic, Anna; Dalén, Love

2016-05-01

Recent palaeogenetic studies indicate a highly dynamic history in collared lemmings (Dicrostonyx spp.), with several demographical changes linked to climatic fluctuations that took place during the last glaciation. At the western range margin of D. torquatus, these changes were characterized by a series of local extinctions and recolonizations. However, it is unclear whether this pattern represents a local phenomenon, possibly driven by ecological edge effects, or a global phenomenon that took place across large geographical scales. To address this, we explored the palaeogenetic history of the collared lemming using a next-generation sequencing approach for pooled mitochondrial DNA amplicons. Sequences were obtained from over 300 fossil remains sampled across Eurasia and two sites in North America. We identified five mitochondrial lineages of D. torquatus that succeeded each other through time across Europe and western Russia, indicating a history of repeated population extinctions and recolonizations, most likely from eastern Russia, during the last 50 000 years. The observation of repeated extinctions across such a vast geographical range indicates large-scale changes in the steppe-tundra environment in western Eurasia during the last glaciation. All Holocene samples, from across the species' entire range, belonged to only one of the five mitochondrial lineages. Thus, extant D. torquatus populations only harbour a small fraction of the total genetic diversity that existed across different stages of the Late Pleistocene. In North American samples, haplotypes belonging to both D. groenlandicus and D. richardsoni were recovered from a Late Pleistocene site in south-western Canada. This suggests that D. groenlandicus had a more southern and D. richardsoni a more northern glacial distribution than previously thought. This study provides significant insights into the population dynamics of a small mammal at a large geographical scale and reveals a rather complex

Paleohydrology of Late Quaternary floods in the Atacama Desert and their paleoclimate implications

NASA Astrophysics Data System (ADS)

Izquierdo, Tatiana; Abad, Manuel; Larrondo, Lidisy

2017-04-01

The Quaternary fluvial succession in the Copiapó Valley (northern Chile) have not been deeply studied even though they record a large amount of palaeoenvironmental and paleoclimate information in an area of great interest as the Atacama Desert. The city of Copiapó is located at the confluence between Quebrada Paipote (the most important tributary of the middle course) and Copiapó River which has been dry during the last decades due to the surface and groundwater exploitation for agricultural and mining activity purposes upstream. Despite that, historical chronicles describe numerous flooding events in the city during the last 400 years due to snowmelt during the summer months or unusually intense rains during any time of the year. The most recent event occurred on March 25, 2015 when 70% of the city flooded and more than 2.2 million m3 of sediment accumulated, mostly coming from Quebrada Paipote. The sedimentological analysis of the lower fluvial terrace of the Copiapó River has allowed us to identify a fluvial system that abruptly changes upward to paleoflood and aeolian deposits. The latter constitute the top of the lower fluvial terraces on which the city of Copiapó is built. The fluvial facies are mainly formed by imbricated to massive conglomerates and poorly sorted pebble and cobble sized conglomerates with laminated sandstones that probably were deposited in a braided gravel-bed river. The overlying deposits are constituted by several levels of massive sandy siltstones and well sorted fine sands of aeolian origin that are interpreted as overbank flood events linked to flooding episodes that alternate with long episodes of eolian dunes and sand sheets development that buried almost the entire alluvial plain. This sharp change in the facies association record an abrupt climate change in the southern Atacama Desert during the recent Quaternary towards more arid conditions, with a dominance of floods and aeolian morphogenesis over the typical fluvial system

Ice-free summers predominant in the late Miocene central Arctic Ocean - New insights from a proxy-modeling approach

NASA Astrophysics Data System (ADS)

Stein, Ruediger; Fahl, Kirsten; Schreck, Michael; Knorr, Gregor; Forwick, Matthias; Lohmann, Gerrit; Niessen, Frank

2016-04-01

During Polarstern Expedition PS87/2014, we discovered multiple submarine landslides over a distance of >350 km along Lomonosov Ridge between about 81°N and 84°N (Stein, 2015). The load and erosional behaviour of an extended ice sheet/shelf that probably occurred during major Quaternary glaciations, may have caused physical conditions that triggered these landslides and major down-slope transport of sediments at this part of Lomonosov Ridge (Stein et al., 2016 and further references therein). The removal of younger sediments from steep headwalls has led to exhumation of Miocene to early Quaternary sediments close to the seafloor, allowing the retrieval of such old sediments by gravity coring and multi-proxy studies of theses sediments. Within one of these studies (Stein et al., 2016), we used for the first time the sea-ice biomarker IP25 (for background of approach see Belt et al., 2007; Müller et al., 2009, 2011) together with alkenone-based sea-surface temperatures (SST) to reconstruct upper Miocene Arctic Ocean sea-ice and SST conditions. The presence of IP25 as proxy for spring sea-ice cover and alkenone-based relatively warm summer SST of >4 °C support a seasonal sea-ice cover with an ice-free summer season being dominant during (most of) the late Miocene central Arctic Ocean. A comparison of our proxy data with Miocene climate simulations seems to favour either relatively high late Miocene atmospheric CO2 concentrations and/or an overly weak sensitivity of the model to simulate the magnitude of high-latitude warming in a warmer than modern climate. References: Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, and C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25, Organic Geochemistry 38, 16-27. Müller, J., Massé, G., Stein, R., and Belt, S., 2009. Extreme variations in sea ice cover for Fram Strait during the past 30 ka. Nature Geoscience, DOI: 10.1038/NGEO665. Müller, J., Wagner, A., Fahl, K., Stein, R., Prange, M., and

PRN 88-2: Clustering of Quaternary Ammonium Compounds

EPA Pesticide Factsheets

This Notice announces that EPA has clustered the Quaternary Ammonium Compounds into four groups for the purpose of testing chemicals to build a database that will support continued registration of the entire family of quaternary ammonium compounds

Late Quaternary high resolution micropaleontological and sedimentological records in the Gulf of Cadiz.

NASA Astrophysics Data System (ADS)

Balestra, B.; Ducassou, E.; Zarikian, C.; Bout-Roumazeilles, V.; Flores, J. A.; Paytan, A.

2017-12-01

We present preliminary micropaleontological and sedimentological data from IODP Site U1390 (Expedition 339), located in the central middle slope of the Gulf of Cadiz, since the last glaciation. This site has been targeted for reconstruction of regional paleo-circulation as it shows particularly high sedimentation rates, throughout the Holocene and the Last Glacial Maximum (LGM). We use micropaleontological and sedimentological proxies to understand the bottom current variations through time and the ecological conditions at the sea surface (planktonic foraminifer, pteropod and nannofossil assemblages), and the sea bottom (ostracod assemblages). Eleven samples, chosen at transitions of planktonic foraminifer assemblages, have been dated by AMS radiocarbon analyses. Preliminary results from benthic ostracod assemblages show variations in bottom water ventilation and food supply. Planktonic foraminifer assemblages clearly show the well-known cold events of this period such as the Younger Dryas and Heinrich stadial associated to coarser sediment, and warmer phases such as the Bölling-Allerød associated to muddy sediment. Other bio-events within the Holocene period are also recorded. The preservation of the coccolithophore assemblages is good to moderate. Coccolith abundances (expressed in coccoliths/gr of sediment) show higher values during the Holocene and generally are like assemblages previously reported for the same area. Implications for characterization of the Holocene, the last termination and LGM ecological conditions at high resolution and their potential fluctuations (i.e. amplitude and magnitude) under the influence of the lower core of the Mediterranean Outflow Water (MOW), with this multi proxy approach based on sedimentological, and paleontological data will be discussed.

Cyclostratigraphic constraints on the duration of the Datangpo Formation and the onset age of the Nantuo (Marinoan) glaciation in South China

NASA Astrophysics Data System (ADS)

Bao, Xiujuan; Zhang, Shihong; Jiang, Ganqing; Wu, Huaichun; Li, Haiyan; Wang, Xinqiang; An, Zhengze; Yang, Tianshui

2018-02-01

Constructing an accurate timeline is critical for reconstructing the Earth systems through critical transitions in climate, geochemistry, and life. Existing dates constrain synchronous initiation (ca. 717 Ma) and termination (ca. 660 Ma) of the Sturtian glaciation from multiple continents. The termination of the younger Marinoan glaciation is also well dated at ca. 635 Ma, but the onset of this glaciation is only roughly constrained as ≤ ca. 654 Ma (South China) and ≥ ca. 639 Ma (Namibia). To test if the Marinoan glaciation started close to ca. 654 Ma or ca. 639 Ma, we have conducted a cyclostratigraphic study on the Cryogenian non-glacial Datangpo Formation that conformably overlies and underlies Sturtian and Marinoan glacial diamictites, respectively, in a deep-water basin section in South China. A total of 28,765 magnetic susceptibility (MS) measurements from a drillcore of the 292-m-thick, muddy siltstone- and shale-dominated Datangpo Formation are used for cyclostratigraphic analysis. The results reveal significant decameter- to meter-scale sedimentary cycles of 16-12 m, 3.6-3.0 m, 1.0-0.8 m, and 0.6-0.4 m. The ratios of these cycle wavelengths match well with those of the Milankovitch cycles calibrated for the Cryogenian Period. The established astrochronologic time scale suggests that the duration of the Datangpo Formation is about 9.8 million years. Together with the radiometric age of ca. 660 Ma for the termination of the Sturtian glaciation, the cyclostratigraphic data suggest that the Nantuo (Marinoan) glaciation in South China initiated at ca. 650 Ma, which is slightly younger than but consistent with the ca. 654 Ma U-Pb age from the top of the Datangpo Formation in shelf sections. This age, however, is significantly older than the ages obtained from Marinoan-age glacial diamictites in South China (ca. 636 Ma) and Namibia (ca. 639 Ma). Given that most of the shelf sections may have suffered from glacial erosion, obtaining the onset age of the

Late Quaternary stream piracy and strath terrace formation along the Belle Fourche and lower Cheyenne Rivers, South Dakota and Wyoming

USGS Publications Warehouse

Stamm, John F.; Hendricks, Robert R.; Sawyer, J. Foster; Mahan, Shannon; Zaprowski, Brent J.; Geibel, Nicholas M.; Azzolini, David C.

2013-01-01

Stream piracy substantially affected the geomorphic evolution of the Missouri River watershed and drainages within, including the Little Missouri, Cheyenne, Belle Fourche, Bad, and White Rivers. The ancestral Cheyenne River eroded headward in an annular pattern around the eastern and southern Black Hills and pirated the headwaters of the ancestral Bad and White Rivers after ~ 660 ka. The headwaters of the ancestral Little Missouri River were pirated by the ancestral Belle Fourche River, a tributary to the Cheyenne River that currently drains much of the northern Black Hills. Optically stimulated luminescence (OSL) dating techniques were used to estimate the timing of this piracy event at ~ 22–21 ka. The geomorphic evolution of the Cheyenne and Belle Fourche Rivers is also expressed by regionally recognized strath terraces that include (from oldest to youngest) the Sturgis, Bear Butte, and Farmingdale terraces. Radiocarbon and OSL dates from fluvial deposits on these terraces indicate incision to the level of the Bear Butte terrace by ~ 63 ka, incision to the level of the Farmingdale terrace at ~ 40 ka, and incision to the level of the modern channel after ~ 12–9 ka. Similar dates of terrace incision have been reported for the Laramie and Wind River Ranges. Hypothesized causes of incision are the onset of colder climate during the middle Wisconsinan and the transition to the full-glacial climate of the late-Wisconsinan/Pinedale glaciation. Incision during the Holocene of the lower Cheyenne River is as much as ~ 80 m and is 3 to 4 times the magnitude of incision at ~ 63 ka and ~ 40 ka. The magnitude of incision during the Holocene might be due to a combined effect of three geomorphic processes acting in concert: glacial isostatic rebound in lower reaches (~ 40 m), a change from glacial to interglacial climate, and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the Little Missouri River.

Late Quaternary stream piracy and strath terrace formation along the Belle Fourche and lower Cheyenne Rivers, South Dakota and Wyoming

NASA Astrophysics Data System (ADS)

Stamm, John F.; Hendricks, Robert R.; Sawyer, J. Foster; Mahan, Shannon A.; Zaprowski, Brent J.; Geibel, Nicholas M.; Azzolini, David C.

2013-09-01

Stream piracy substantially affected the geomorphic evolution of the Missouri River watershed and drainages within, including the Little Missouri, Cheyenne, Belle Fourche, Bad, and White Rivers. The ancestral Cheyenne River eroded headward in an annular pattern around the eastern and southern Black Hills and pirated the headwaters of the ancestral Bad and White Rivers after ~ 660 ka. The headwaters of the ancestral Little Missouri River were pirated by the ancestral Belle Fourche River, a tributary to the Cheyenne River that currently drains much of the northern Black Hills. Optically stimulated luminescence (OSL) dating techniques were used to estimate the timing of this piracy event at ~ 22-21 ka. The geomorphic evolution of the Cheyenne and Belle Fourche Rivers is also expressed by regionally recognized strath terraces that include (from oldest to youngest) the Sturgis, Bear Butte, and Farmingdale terraces. Radiocarbon and OSL dates from fluvial deposits on these terraces indicate incision to the level of the Bear Butte terrace by ~ 63 ka, incision to the level of the Farmingdale terrace at ~ 40 ka, and incision to the level of the modern channel after ~ 12-9 ka. Similar dates of terrace incision have been reported for the Laramie and Wind River Ranges. Hypothesized causes of incision are the onset of colder climate during the middle Wisconsinan and the transition to the full-glacial climate of the late-Wisconsinan/Pinedale glaciation. Incision during the Holocene of the lower Cheyenne River is as much as ~ 80 m and is 3 to 4 times the magnitude of incision at ~ 63 ka and ~ 40 ka. The magnitude of incision during the Holocene might be due to a combined effect of three geomorphic processes acting in concert: glacial isostatic rebound in lower reaches (~ 40 m), a change from glacial to interglacial climate, and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the Little Missouri River.

Comparative analyses of quaternary arrangements in homo-oligomeric proteins in superfamilies: Functional implications.

PubMed

Sudha, Govindarajan; Srinivasan, Narayanaswamy

2016-09-01

A comprehensive analysis of the quaternary features of distantly related homo-oligomeric proteins is the focus of the current study. This study has been performed at the levels of quaternary state, symmetry, and quaternary structure. Quaternary state and quaternary structure refers to the number of subunits and spatial arrangements of subunits, respectively. Using a large dataset of available 3D structures of biologically relevant assemblies, we show that only 53% of the distantly related homo-oligomeric proteins have the same quaternary state. Considering these homologous homo-oligomers with the same quaternary state, conservation of quaternary structures is observed only in 38% of the pairs. In 36% of the pairs of distantly related homo-oligomers with different quaternary states the larger assembly in a pair shows high structural similarity with the entire quaternary structure of the related protein with lower quaternary state and it is referred as "Russian doll effect." The differences in quaternary state and structure have been suggested to contribute to the functional diversity. Detailed investigations show that even though the gross functions of many distantly related homo-oligomers are the same, finer level differences in molecular functions are manifested by differences in quaternary states and structures. Comparison of structures of biological assemblies in distantly and closely related homo-oligomeric proteins throughout the study differentiates the effects of sequence divergence on the quaternary structures and function. Knowledge inferred from this study can provide insights for improved protein structure classification and function prediction of homo-oligomers. Proteins 2016; 84:1190-1202. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Mapping the North Sea base-Quaternary: using 3D seismic to fill a gap in the geological record

NASA Astrophysics Data System (ADS)

Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

2014-05-01

water currents. This has strong implications for both the Quaternary climate archive and petroleum systems in the North Sea. Key Words: base-Quaternary; chronostratigraphy: seismic interpretation; paleoenvironments References Buckley, F.A., (2012) 'An Early Pleistocene grounded ice sheet in the Central North Sea' From: Huuse, M., Redfern, J., Le Heron, D.P., Dixon, R.J., Moscariello, A., Craig, J. (eds) 'Glaciogenic reservoirs and Hydrocarbon Systems' Geological Society, London, Special Publications, 368 Cameron, T.D.J., Stoker, M.S., Long, D., (1987) 'The history of Quaternary sedimentation in the UK sector of the North Sea Basin' Journal of the Geological Society, 144, 43-58 Gatliff, R.W, Richards, P.C, Smith, K, Graham, C.C, McCormac, M, Smith, N.J.P, Long, D, Cameron, T.D.J, Evans, D, Stevenson, A.G, Bulat, J, Ritchie, J.D, (1994) 'United Kingdom offshore regional report: the geology of the central North Sea.' London: HMSO for the British Geological Survey Kulhmann, G., Langereis C.G., Munsterman, D., van Leeuwen, R.-J., Verreussel, R., Meulenkamp, J.E., Wong, Th.E., 2006 'Intergrated chronostratigraphy of the Pliocene-Pliestocene interval and its relation to the regional stratigraphical stages in the Southern North Sea region' Netherlands Journal of Geosciences 85(1), 29-45 Rasmussen, E.A., Vejb?k O.V., Bidstrup, T., Piasecki, S., Dybkj?r, K., 2005 'Late Cenozoic depositional history of the Danish North Sea Basin: implications for the petroleum systems in the Kraka, Halfdan, Siri and Nini fields', Petroleum Geology Conference series 6, 1347-1358 Sejrup, H.P., Aareseth, I., Haflidason, H., 1991 'The Quaternary succession in the northern North Sea' Marine Geology 101 103-111

Insights into the Quaternary tectonics of the Yellowstone hotspot from a terrace record along the Hoback and Snake rivers.

NASA Astrophysics Data System (ADS)

Bufe, A.; Pederson, J. L.; Tuzlak, D.

2016-12-01

One of Earth's largest active supervolcanos and one of the most dynamically deforming areas in North America is located above the Yellowstone mantle plume. A pulse of dynamically supported uplift and extension of the upper crust has been moving northeastward as the North American plate migrated across the hotspot. This pules of uplift is complicated by subsidence of the Snake River Plain in the wake of the plume, due to a combination of crustal loading by intrusive and extrusive magmas, and by densification of igneous and volcanic rocks. Understanding the geodynamics as well as the seismic hazard of this region relies on studying the distribution and timing of active uplift, subsidence, and faulting across timescales. Here, we present preliminary results from a study of river terraces along the Hoback and upper Snake rivers that flow from the flanks of the Yellowstone plateau into the subsiding Snake River Plain. Combining terrace surveys with optically stimulated luminescence ages, we calculate incision rates of 0.1 - 0.3 mm/y along the deeply incised canyons of the Hoback and Snake rivers upstream of Alpine, WY. Rather than steadily decreasing away from the Yellowstone plume-head, the pattern of incision rates seems to be mostly affected by the distribution of normal faults - including the Alpine section of the Grand Valley Fault that has been reported to be inactive throughout the Quaternary. Downstream of Alpine and approaching the Snake River Plain, late Quaternary fill-terraces show much slower incision rates which might be consistent with a broad flexure of the region toward the subsiding Snake River Plain. Future studies of the Snake and Hoback rivers and additional streams around the Yellowstone hotspot will further illuminate the pattern of late Quaternary uplift in the region.

An aminostratigraphy for the British Quaternary based on Bithynia opercula

PubMed Central

Penkman, Kirsty E.H.; Preece, Richard C.; Bridgland, David R.; Keen, David H.; Meijer, Tom; Parfitt, Simon A.; White, Tom S.; Collins, Matthew J.

2013-01-01

Aminostratigraphies of Quaternary non-marine deposits in Europe have been previously based on the racemization of a single amino acid in aragonitic shells from land and freshwater molluscs. The value of analysing multiple amino acids from the opercula of the freshwater gastropod Bithynia, which are composed of calcite, has been demonstrated. The protocol used for the isolation of intra-crystalline proteins from shells has been applied to these calcitic opercula, which have been shown to more closely approximate a closed system for indigenous protein residues. Original amino acids are even preserved in bithyniid opercula from the Eocene, showing persistence of indigenous organics for over 30 million years. Geochronological data from opercula are superior to those from shells in two respects: first, in showing less natural variability, and second, in the far better preservation of the intra-crystalline proteins, possibly resulting from the greater stability of calcite. These features allow greater temporal resolution and an extension of the dating range beyond the early Middle Pleistocene. Here we provide full details of the analyses for 480 samples from 100 horizons (75 sites), ranging from Late Pliocene to modern. These show that the dating technique is applicable to the entire Quaternary. Data are provided from all the stratotypes from British stages to have yielded opercula, which are shown to be clearly separable using this revised method. Further checks on the data are provided by reference to other type-sites for different stages (including some not formally defined). Additional tests are provided by sites with independent geochronology, or which can be associated with a terrace stratigraphy or biostratigraphy. This new aminostratigraphy for the non-marine Quaternary deposits of southern Britain provides a framework for understanding the regional geological and archaeological record. Comparison with reference to sites yielding independent geochronology, in

Quaternary incised valleys in southern Brazil coastal zone

NASA Astrophysics Data System (ADS)

Weschenfelder, Jair; Baitelli, Ricardo; Corrêa, Iran C. S.; Bortolin, Eduardo C.; dos Santos, Cristiane B.

2014-11-01

High-resolution seismic records obtained in the Rio Grande do Sul coastal zone, southern Brazil, revealed that prominent valleys and channels developed in the area before the installation of actual coastal plain. Landwards, the paleoincisions can be linked with the present courses of the main river dissecting the area. Oceanwards, they can be linked with related features previously recognized in the continental shelf and slope by means of seismic and morphostructural studies. Based mainly on seismic, core data and geologic reasoning, it can be inferred that the coastal valleys were incised during forced regression events into the coastal prism deposited during previous sea level highstand events of the Quaternary. Seismic data has revealed paleovalleys up to 10 km wide and, in some places, infilled with up to 40 m thick of sediments. The results indicated two distinct periods of cut-and-fill events in the Patos Lagoon area. The filling of the younger incision system is mainly Holocene and its onset is related to the last main regressive event of the Pleistocene, when the sea level fell about 130 m below the actual position. The older incision and filling event is related to the previous regressive-transgressive events of the Middle and Late Pleistocene. The fluvial discharge fed delta systems on the shelf edge during the sea level lowstands. The subsequent transgressions drowned the incised drainage, infilling it and closing the inlets formerly connecting the coastal river to the ocean. The incised features may have played a significant role on the basin-margin architecture, facies distribution and accommodation space during the multitude of up and down sea level events of the Quaternary.

ODP Sites 967 and 968 (eastern Mediterranean) revisited and implications for the global oxygen stable isotope chronology of the late Pleistocene

NASA Astrophysics Data System (ADS)

Konijnendijk, Tiuri; Lourens, Lucas; Ziegler, Martin

2013-04-01

terminations and onset of glaciation for several isotope stages prior to MIS 11 of up to 10,000 years. The direct comparison of our stable isotope record to insolation appears to suggest a dominant role of obliquity forcing in ice volume behavior for much further into the Pleistocene than generally assumed. References Lourens, L.J., J. Becker, R. Bintanja et al. (2010), Linear and non-linear response of late Neogene glacial cycles to obliquity forcing and implications for the Milankovitch theory. Quaternary Science Reviews 29(1-2), pp.352-365. Ziegler, M., E. Tuenter & L.J. Lourens. (2010), The precession phase of the boreal summer monsoon as viewed from the eastern Mediterranean (ODP Site 968). Quaternary Science Reviews 29(11-12), pp.1481-1490.

Sedimentologic and paleoclimatic reconstructions of carbonate factory evolution in the Alborz Basin (northern Iran) indicate a global response to Early Carboniferous (Tournaisian) glaciations

NASA Astrophysics Data System (ADS)

Sardar Abadi, Mehrdad; Kulagina, Elena I.; Voeten, Dennis F. A. E.; Boulvain, Frédéric; Da Silva, Anne-Christine

2017-03-01

The Lower Carboniferous Mobarak Formation records the development of a storm-sensitive pervasive carbonate factory on the southern Paleo-Tethyan passive margin following the opening of the Paleo-Tethys Ocean into the Alborz Basin along the northern margin of Gondwana. Its depositional facies encompass inner ramp peritidal environments, peloidal to crinoidal shoals, storm to fair-weather influenced mid-ramps, proximal to distal shell beds and low energy outer ramps. Sedimentological analyses and foraminiferal biostratigraphy reveal four events affecting carbonate platform evolution in the Alborz Basin during the Lower Carboniferous: (1) A transgression following global temperature rise in the Early Tournaisian (middle Hastarian) caused the formation of thick-bedded argillaceous limestones. This interval correlates with Early Tournaisian nodular to argillaceous limestones in the Moravia Basin (Lisen Formation, Czech Republic), the Dinant Basin (Pont d'Arcole Formation, Belgium), and at the Rhenish Slate Mountains (Lower Alum shale, Germany). (2) Late Hastarian-early Ivorian glaciations previously identified in Southern Gondwana but had not yet recognized in Northern Gondwana were recorded through a sequence boundary. (3) During the Late Tournaisian-Early Visean?, a differential block faulting regime along the basin's margin caused uplift of the westernmost parts of the Alborz Basin and resulted in subsidence in the eastern part of the central basin. This tectonically controlled shift in depositional regime caused vast sub-aerial exposure and brecciation preserved in the top of the Mobarak Formation in the western portion of the Central Alborz Basin. (4) Tectonic activity coinciding with a progressive, multiphase sea level drop caused indirectly by the Viséan and Serpukhovian glaciations phases ultimately led to the stagnation of the carbonate factory. Paleothermometry proxies, the presence of foraminiferal taxa with a northern Paleo-Tethyan affinity and evidence for

Flower-strucutre deformation pattern of theTian Shan mountains as revealed by Late Quaternary geological and modern Geodesy slip rates

NASA Astrophysics Data System (ADS)

Wu, C.; Zhang, P.; Zheng, W.; Wang, H.; Zhang, Z.; Ren, Z.; Zheng, D.; Yu, J.; Wu, G.

2017-12-01

The deformation pattern and strain distribution of the Tian Shan is a hot issue.Previous studies mainly focus on the thrust-fold systems on both sides of Tian Shan, the strike-slip faults within the mountains are rarely reported. The understanding about the deformation characteristics of Tian Shan is not complete for lacking information of these strike-slip faults.Our studies show the NEE trending structures of Maidan fault and Nalati fault in the southwestern Tian Shan are all active during the Holence. These faults are characterized by sinistral strike-slip and thrust movement. The minimum average sinistral strike-slip rate of the Maidan fault is 1.07 ± 0.13 mm/yr. During the late Quaternary, the average shortening rate and sinistral strike-slip rate of the Nalati fault are 2.1 ±0.4 mm/yr and 2.56 ±0.25 mm/yr, respectively . In the interior of the Tian Shan area, two groups of strike-slip faults were developed. The NEE trending faults with sinistral strike-slipmovement, and the NWW trending faults with dextral strike-slip movement show the shape of "X"in geometrical structure. The piedmont thrust faults and the thrust strike-slip faults in the interior mountain constitute the tectonic framework of Tian Shan. Threegroups of active fault systems are the main seismogenic and geological structures, which control the current tectonic deformation pattern of Tian Shan (Figure 1). GPS observation data also showthe similar deformation characteristics with the geological results (Figures 2, 3). In addition to the crustal shortening, there is a certain strike-slip shear movement in the interior of the Tian Shan.The strike-slip rate defined by the geological and GPS data is approximately consistent with each other near the same longitude. We suggest the two groups of strike-slip faults in the interior of mountains is a set of conjugate structures. The whole Tian Shan forms a large flower-structure in a profile view. The complete tectonic deformation of the Tian Shan

Regionally coherent, downstream propagating trends of river bed incision and aggradation in glaciated basins of western Washington, USA

NASA Astrophysics Data System (ADS)

Anderson, S. W.; Konrad, C. P.

2016-12-01

Understanding the connections between climate and river bed morphology is relevant both for interpreting the geologic record and understanding modern channel change. Here, we use changing stage-discharge relations at USGS stream-gage sites in western Washington State to infer local bed-elevation changes over the past 50 to 90 years. A network of gages in a large, unregulated basin with active glaciation show decadal periods of aggradation and incision that are strongly correlated when lagged. Best-fit lag times indicate the downstream propagation of single coherent signal at a slope-dependent velocity of 1-4 km/yr. This same pattern of change is observed at the outlets of regional rivers with glaciated headwaters but is absent in unglaciated river systems. Sites high in glaciated river systems also show coherency across basins, suggesting that the similarity in the downstream trends across glaciated basins is the result of the downstream propagation of a regionally coherent headwater signal. Incisional trends emanating from headwaters between 1950 and 1980 match a period when regional glaciers were stable or advancing, but assigning causation is complicated by hydroclimatic trends with similar temporal patterns. The recent trend is aggradational, though current bed elevations are generally similar to those prior to 1950, and are consistent with regional data indicating that sediment production in glaciated basins from 1950 to 1980 was anomalously low relative to conditions over the past several hundred years. Regionally, our results suggest the possibility of forecasting periods of aggradation and increased flood hazards several years to decades in advance in populated downstream settings. More broadly, the methods used in this analysis involve simple calculations on publically available data and provide a low-cost means of assessing local channel change wherever USGS stream-gages have been operated.

Extensive MIS 3 glaciation in southernmost Patagonia revealed by cosmogenic nuclide dating of outwash sediments

NASA Astrophysics Data System (ADS)

Darvill, Christopher M.; Bentley, Michael J.; Stokes, Chris R.; Hein, Andrew S.; Rodés, Ángel

2015-11-01

The timing and extent of former glacial advances can demonstrate leads and lags during periods of climatic change and their forcing, but this requires robust glacial chronologies. In parts of southernmost Patagonia, dating pre-global Last Glacial Maximum (gLGM) ice limits has proven difficult due to post-deposition processes affecting the build-up of cosmogenic nuclides in moraine boulders. Here we provide ages for the Río Cullen and San Sebastián glacial limits of the former Bahía Inútil-San Sebastián (BI-SSb) ice lobe on Tierra del Fuego (53-54°S), previously hypothesised to represent advances during Marine Isotope Stages (MIS) 12 and 10, respectively. Our approach uses cosmogenic 10Be and 26Al exposure dating, but targets glacial outwash associated with these limits and uses depth-profiles and surface cobble samples, thereby accounting for surface deflation and inheritance. The data reveal that the limits formed more recently than previously thought, giving ages of 45.6 ka (+139.9/-14.3) for the Río Cullen, and 30.1 ka (+45.6/-23.1) for the San Sebastián limits. These dates indicate extensive glaciation in southern Patagonia during MIS 3, prior to the well-constrained, but much less extensive MIS 2 (gLGM) limit. This suggests the pattern of ice advances in the region was different to northern Patagonia, with the terrestrial limits relating to the last glacial cycle, rather than progressively less extensive glaciations over hundreds of thousands of years. However, the dates are consistent with MIS 3 glaciation elsewhere in the southern mid-latitudes, and the combination of cooler summers and warmer winters with increased precipitation, may have caused extensive glaciation prior to the gLGM.

Late Neogene and Active Tectonics along the Northern Margin of the Central Anatolian Plateau,TURKEY

NASA Astrophysics Data System (ADS)

Yildirim, C.; Schildgen, T. F.; Melnick, D.; Echtler, H. P.; Strecker, M. R.

2009-12-01

Margins of orogenic plateaus are conspicuous geomorphic provinces that archive tectonic and climatic variations related to surface uplift. Their growth is associated with spatial and temporal variations of mode and rate of tectonics and surface processes. Those processes can be strongly linked to the evolution of margins and plateaus thorough time. As one of the major morpho-tectonic provinces of Turkey, the Central Pontides (coinciding with the northern margin of the Central Anatolian Plateau (CAP)) display a remarkable topography and present valuable geologic and geomorphic indicators to identify active tectonics. Morpho-tectonic analysis, geological cross-sections, seismic profiles, and geodetic analysis reveal continuous deformation characterized by brittle faults from Late Miocene to recent across the northern margin of the CAP. In the Sinop Peninsula and offshore in the southern Black Sea, pervasive faulting and folding and uplift of Late Miocene to Quaternary marine deposits is related to active margin tectonics of the offshore southern Black Sea thrust and the onshore Balifaki and Erikli faults. In the Kastamonu-Boyabat sedimentary basin, the Late Miocene to Quaternary continental equivalents are strongly deformed by the Ekinveren Fault. This vergent inverse and thrust fault with overstepping en echelon segments deforms not only Quaternary travertines and conglomerates, but also patterns of the Pleistocene to Holocene drainage systems. In the southern Kastamonu-Boyabat basin, an antithetic thrust fault of the Ekinveren Fault system deformed also Quaternary fluviatile terrace deposits. Farther south, a dextral transpressive splay of the North Anatolian Fault (NAF) deforms pediment surfaces and forms the northern flank of the Ilgaz active mountain range. The Ilgaz Range rises up to 2587 m.a.s.l and is delimited by active segments of the NAF.The Central Pontides are located at the apex of northward convex arc of the NAF. Geodetic analysis indicate a deviation

Episode of intense chemical weathering during the termination of the 635 Ma Marinoan glaciation.

PubMed

Huang, Kang-Jun; Teng, Fang-Zhen; Shen, Bing; Xiao, Shuhai; Lang, Xianguo; Ma, Hao-Ran; Fu, Yong; Peng, Yongbo

2016-12-27

Cryogenian (∼720-635 Ma) global glaciations (the snowball Earth) represent the most extreme ice ages in Earth's history. The termination of these snowball Earth glaciations is marked by the global precipitation of cap carbonates, which are interpreted to have been driven by intense chemical weathering on continents. However, direct geochemical evidence for the intense chemical weathering in the aftermath of snowball glaciations is lacking. Here, we report Mg isotopic data from the terminal Cryogenian or Marinoan-age Nantuo Formation and the overlying cap carbonate of the basal Doushantuo Formation in South China. A positive excursion of extremely high δ 26 Mg values (+0.56 to +0.95)-indicative of an episode of intense chemical weathering-occurs in the top Nantuo Formation, whereas the siliciclastic component of the overlying Doushantuo cap carbonate has significantly lower δ 26 Mg values (<+0.40), suggesting moderate to low intensity of chemical weathering during cap carbonate deposition. These observations suggest that cap carbonate deposition postdates the climax of chemical weathering, probably because of the suppression of carbonate precipitation in an acidified ocean when atmospheric CO 2 concentration was high. Cap carbonate deposition did not occur until chemical weathering had consumed substantial amounts of atmospheric CO 2 and accumulated high levels of oceanic alkalinity. Our finding confirms intense chemical weathering at the onset of deglaciation but indicates that the maximum weathering predated cap carbonate deposition.

Displacement rates on the Toroweap and Hurricane faults: implications for Quaternary downcutting in the Grand Canyon, Arizona

USGS Publications Warehouse

Fenton, Cassandra R.; Webb, Robert H.; Pearthree, Philip A.; Cerling, Thure E.; Poreda, Robert J.

2001-01-01

The Toroweap and Hurricane faults, considered to be the most active in Arizona, cross the Uinkaret volcanic field in the western Grand Canyon. These normal faults are downthrown to the west, and the Colorado River crosses these faults as it flows west in the Grand Canyon. Cosmogenic 3He (3Hec) dates on basalt flows and related landforms are used to calculate vertical displacement rates for these faults. The two faults cross unruptured alluvial fans dated as 3 ka (Toroweap) and 8 ka (Hurricane), and 10 other landforms that range in age from 30 to 400 ka are displaced. Middle and late Quaternary displacement rates of the Toroweap and Hurricane faults are 70–180 and 70–170 m/m.y., respectively. On the basis of these rates, the combined displacement of 580 m on these faults could have occurred in the past 3 to 5 m.y. All 3Hec dates are younger than existing K- Ar dates and are consistent with new 40Ar/39Ar dates and existing thermoluminescence (TL) dates on basalt flows. These different dating techniques may be combined in an analysis of displacement rates. Downcutting rates for the Colorado River in the eastern Grand Canyon (400 m/m.y.) are at least double the downcutting rates west of the faults (70–160 m/m.y.). Faulting probably increased downcutting in the eastern Grand Canyon relative to downcutting in the western Grand Canyon during the late Quaternary.

Pedo-sedimentary constituents as paleoenvironmental proxies in the Sudano-Sahelian belt during the Late Quaternary (southwestern Chad Basin)

NASA Astrophysics Data System (ADS)

Diaz, Nathalie; Dietrich, Fabienne; Sebag, David; King, Georgina E.; Valla, Pierre G.; Durand, Alain; Garcin, Yannick; de Saulieu, Geoffroy; Deschamps, Pierre; Herman, Frédéric; Verrecchia, Eric P.

2018-07-01

Climate and environmental changes since the Last Glacial Maximum in the tropical zone of West Africa are usually inferred from marine and continental records. In this study, the potential of carbonate pedo-sedimentary geosystems, i.e. Vertisol relics, to record paleoenvironmental changes in the southwestern part of Chad Basin are investigated. A multi-dating approach was applied on different pedogenic organo-mineral constituents. Optically stimulated luminescence (OSL) dating was performed on the soil K-rich feldspars and was combined with radiocarbon dating on both the inorganic (14Cinorg) and organic carbon (14Corg) soil fractions. Three main pedo-sedimentary processes were assessed over the last 20 ka BP: 1) the soil parent material deposition, from 18 ka to 12 ka BP (OSL), 2) the soil organic matter integration, from 11 cal ka to 8 cal ka BP (14Corg), and 3) the pedogenic carbonate nodule precipitation, from 7 cal ka to 5 cal ka BP (14Cinorg). These processes correlate well with the Chad Basin stratigraphy and West African records and are shown to be related to significant changes in the soil water balance responding to the evolution of continental hydrology during the Late Quaternary. The last phase affecting the Vertisol relics is the increase of erosion, which is hypothesized to be due to a decrease of the vegetation cover triggered by (i) the onset of drier conditions, possibly strengthened by (ii) anthropogenic pressure. Archaeological data from Far North Cameroon and northern Nigeria, as well as sedimentation times in Lake Tilla (northeastern Nigeria), were used to test these relationships. The increase of erosion is suggested to possibly occur between c. 3 cal ka and 1 cal ka BP. Finally, satellite images revealed similar geosystems all along the Sudano-Sahelian belt, and initial 14Cinorg ages of the samples collected in four sites gave similar ages to those reported in this study. Consequently, the carbonate pedo-sedimentary geosystems are valuable

New Evidence For A Late Miocene Onset Of The Amazon River Following Andean Tectonics And Quaternary Climate Change

NASA Astrophysics Data System (ADS)

Hoorn, M. C.; Bogota-Angel, G.; Romero-Baez, M.; Lammertsma, E.; Flantua, S. G. A.; Dantas, E. L.; Dino, R.; do Carmo, D.; Chemale, F., Jr.

2017-12-01

The Amazon River influenced biotic evolution on land and at sea, but its onset and development are still debated. Terrestrial sedimentary records are sparse, far apart, and do not present a continuous stratigraphy and thus greatly complicate the reconstruction of the history of this river system. At sea the stratigraphic record is better known thanks to hydrocarbon exploration efforts, but these data are not in the public domain. Renewed exploration in the Amazon submarine fan (Brazilian Equatorial Margin) has provided novel data and materials from wells drilled along the slope of the Amazon submarine fan, that are now partially available for scientific research. Here we report on the results of a geochemical and palynological study of `Well 2' based on which we determined the age and provenance of early Miocene to Pleistocene sediments. The palynological data were also used to reconstruct past biomes on land, which ranged from mangrove and lowland forest to alpine vegetation. A distinct change in provenance was observed between 9.4 Ma and 9 Ma, which represented a change from Amazonian to Andean sediment source. This signal is replicated in the palynological record, which shows a shift from lowland to high-mountain taxa. Furthermore, we observed a very large increase of grass pollen from the Pliocene onwards with a further rise in the Pleistocene. These changes coincide with a rise in sedimentation rates. We interpret these results as following: a) the arrival of Andean sediments is related to the onset of the transcontinental river, b) the two-step rise of grass pollen and manifold increase in sediment discharge are related to Quaternary climatic change. These results agree with earlier and recent findings on the Ceara Rise and firmly place the birth of this river in the late Miocene. This study exemplifies the continental scale of tectonic changes on fluvial environments and biota across a W-E transect of South America. The study of this well is continued and we

Geographic and stratigraphic distribution of coastal Quaternary aminozones across the Cape Fear Arch, U. S. Atlantic Geology Coastal Plain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wehmiller, J.F.; York, L.L.; Krantz, D.E.

1992-01-01

The interpretation of the regional aminostratigraphy of Coastal Plain Quaternary units from North and South Carolina is potentially affected by sampling biases, variable preservation of coastal records, reoccupation of coastal environments by multiple transgressions, geochemical alteration of samples, variable thermal histories of specific samples, and intergeneric and interlaboratory differences in analytical results.Two primary models for the correlation of emergent Coastal Plain units diverge significantly in southeastern North Carolina. New data from fresh exposure (1990--1991) at emergent sites between Wilmington, NC and Charleston, SC, from previous onshore collections in this region, and from submergent samples between Cape Lookout, NC and Capemore » Romain, SC provide insight into the nature of these correlation issues. Although sampling of the area is not uniform, these results fill a major gap between regions of previous aminostratigraphy study. Inferred early-to-middle Pleistocene aminozones dominate the emergent coastal region between Cape Lookout and Romain, and late Pleistocene aminozones in this area are represented by subsurface samples beneath barrier islands or in shallow inner shelf cores, but have not been found onshore. A map view of the distribution of aminozones along the coast between northeastern NC and central SC mimics that of pre-Quaternary units that thin or disappear over the axis of the Cape Fear Arch, suggesting that the sampled Quaternary record reflects the combination of processes responsible for the preservation of the pre-Quaternary record. This perspective should provide a model for resolution of various geochronological controversies that have arisen because of limited stratigraphic or geochemical data.« less

A novel route to recognizing quaternary ammonium cations using electrospray mass spectrometry.

PubMed

Shackman, Holly M; Ding, Wei; Bolgar, Mark S

2015-01-01

Characterizing and elucidating structures is a commonplace and necessary activity in the pharmaceutical industry with mass spectrometry and NMR being the primary tools for analysis. Although many functional groups are readily identifiable, quaternary ammonium cations have proven to be difficult to unequivocally identify using these techniques. Due to the lack of an N-H bond, quaternary ammonium groups can only be detected in the (1)H NMR spectra by weak signals generated from long-range (14)N-H coupling, which by themselves are inconclusive evidence of a quaternary ammonium functional group. Due to their low intensity, these signals are frequently not detected. Additionally, ions cannot be differentiated in a mass spectrum as an M(+) or [M + H](+) ion without prior knowledge of the compound's structure. In order to utilize mass spectrometry as a tool for determining this functionality, ion cluster formation of quaternary ammonium cations and non-quaternary amines was studied using electrospray ionization. Several mobile phase modifiers were compared; however, the addition of small amounts of trifluoroacetic acid proved superior in producing characteristic and intense [M +2TFA](-) clusters for compounds containing quaternary ammonium cations when using negative electrospray. By fragmenting this characteristic ion using CID, nearly all compounds studied could be unambiguously identified as containing a quaternary ammonium cation or a non-quaternary amine attributable to the presence (non-quaternary amine) or absence (quaternary ammonium cation) of the resulting [2TFA + H](-) ion in the product spectra. This method of analysis provides a rapid, novel, and reliable technique for indicating the presence of quaternary ammonium cations in order to aid in structural elucidation.

3D seismic evidence of buried iceberg ploughmarks from the mid-Norwegian continental margin reveals largely persistent North Atlantic Current through the Quaternary.

PubMed

Montelli, A; Dowdeswell, J A; Ottesen, D; Johansen, S E

2018-05-01

Over 7500 buried linear and curvilinear depressions interpreted as iceberg ploughmarks were identified within the Quaternary Naust Formation from an extensive three-dimensional seismic dataset that covers ~ 40,000 km 2 of the mid-Norwegian continental margin. The morphology and net orientation of ploughmarks were mapped and analysed. These features are up to 28 km long, 700 m wide and are incised up to 31 m deep. On average, ploughmarks are incised 5 m deep, with median width of 185 m and median lengths ranging from 1.2 to 2.7 km for individual palaeo-surfaces. Width to depth ratio ranges from 8:1 to 400:1 and is on average 36:1. The presence of ploughmarks buried deeply within some palaeo-slope surfaces implies the occasional presence of very large icebergs since the middle Quaternary, suggesting that thick ice-sheet margins with fast-flowing ice streams were present in order to calve icebergs of such dimensions into the Norwegian Sea. The wide geographical distribution of ploughmarks suggests unrestricted iceberg drift and an open Norwegian Sea during the periods of iceberg calving since the early Quaternary. Ploughmark trajectory analysis demonstrates that the ocean current circulation, now dominated by the northeasterly flowing Norwegian Atlantic Current (NwAC), has largely persisted throughout the Quaternary. Despite the overall strikingly consistent pattern of iceberg drift, ploughmark mapping also shows evidence for short-lived NwAC reductions possibly related to major phases of iceberg discharge and/or meltwater pulses from the Fennoscandian Ice Sheet during the middle and late Quaternary.

Active tectonics of the Binalud Mountains, a key puzzle segment to describe Quaternary deformations at the northeastern boundary of the Arabia-Eurasia collision

NASA Astrophysics Data System (ADS)

Shabanian, Esmaeil; Bellier, Olivier; Siame, Lionel L.; Abbassi, Mohammad R.; Leanni, Laetitia; Braucher, Régis; Farbod, Yassaman; Bourlès, Didier L.

2010-05-01

In northeast Iran, the Binalud Mountains accommodate part of active convergence between the Arabian and Eurasian plates. This fault-bounded mountain range has been considered a key region to describe Quaternary deformations at the northeastern boundary of the Arabia-Eurasia collision. But, the lack of knowledge on active faulting hampered evaluating the geological reliability of tectonic models describing the kinematics of deformation in northeast Iran. Morphotectonic investigations along both sides of the Binalud Mountains allowed us to characterize the structural and active faulting patterns along the Neyshabur and Mashhad fault systems on the southwest and northeast sides of the mountain range, respectively. We applied combined approaches of morphotectonic analyses based on satellite imageries (SPOT5 and Landsat ETM+), STRM and site-scale digital topographic data, and field surveys complemented with in situ-produced 10Be exposure dating to determine the kinematics and rate of active faulting. Three regional episodes of alluvial surface abandonments were dated at 5.3±1.1 kyr (Q1), 94±5 kyr (Q3), and 200±14 kyr (S3). The geomorphic reconstruction of both vertical and right-lateral fault offsets postdating these surface abandonment episodes yielded Quaternary fault slip rates on both sides of the Binalud Mountains. On the Neyshabur Fault System, thanks to geomorphic reconstructions of cumulative offsets recorded by Q3 fan surfaces, slip rates of 2.7±0.8 mm/yr and 2.4±0.2 mm/yr are estimated for right-lateral and reverse components of active faulting, respectively. Those indicate a total slip rate of 3.6±1.2 mm/yr for the late Quaternary deformation on the southwest flank of the Binalud Mountains. Reconstructing the cumulative right-lateral offset recorded by S3 surfaces, a middle-late Quaternary slip rate of 1.6±0.1 mm/yr is determined for the Mashhad Fault System. Altogether, our geomorphic observations reveal that, on both sides of the Binalud Mountains

Newport-Inglewood-Carlsbad-Coronado Bank Fault System Nearshore Southern California: Testing models for Quaternary deformation

NASA Astrophysics Data System (ADS)

Bennett, J. T.; Sorlien, C. C.; Cormier, M.; Bauer, R. L.

2011-12-01

The San Andreas fault system is distributed across hundreds of kilometers in southern California. This transform system includes offshore faults along the shelf, slope and basin- comprising part of the Inner California Continental Borderland. Previously, offshore faults have been interpreted as being discontinuous and striking parallel to the coast between Long Beach and San Diego. Our recent work, based on several thousand kilometers of deep-penetration industry multi-channel seismic reflection data (MCS) as well as high resolution U.S. Geological Survey MCS, indicates that many of the offshore faults are more geometrically continuous than previously reported. Stratigraphic interpretations of MCS profiles included the ca. 1.8 Ma Top Lower Pico, which was correlated from wells located offshore Long Beach (Sorlien et. al. 2010). Based on this age constraint, four younger (Late) Quaternary unconformities are interpreted through the slope and basin. The right-lateral Newport-Inglewood fault continues offshore near Newport Beach. We map a single fault for 25 kilometers that continues to the southeast along the base of the slope. There, the Newport-Inglewood fault splits into the San Mateo-Carlsbad fault, which is mapped for 55 kilometers along the base of the slope to a sharp bend. This bend is the northern end of a right step-over of 10 kilometers to the Descanso fault and about 17 km to the Coronado Bank fault. We map these faults for 50 kilometers as they continue over the Mexican border. Both the San Mateo - Carlsbad with the Newport-Inglewood fault and the Coronado Bank with the Descanso fault are paired faults that form flower structures (positive and negative, respectively) in cross section. Preliminary kinematic models indicate ~1km of right-lateral slip since ~1.8 Ma at the north end of the step-over. We are modeling the slip on the southern segment to test our hypothesis for a kinematically continuous right-lateral fault system. We are correlating four

Variations in Mediterranean-Atlantic exchange across the late Pliocene climate transition

NASA Astrophysics Data System (ADS)

García-Gallardo, Ángela; Grunert, Patrick; Piller, Werner E.

2018-03-01

Mediterranean-Atlantic exchange through the Strait of Gibraltar plays a significant role in the global ocean-climate dynamics in two ways. On one side, the injection of the saline and warm Mediterranean Outflow Water (MOW) contributes to North Atlantic deep-water formation. In return, the Atlantic inflow is considered a sink of less saline water for the North Atlantic Ocean. However, while the history of MOW is the focus of numerous studies, the Pliocene Atlantic inflow has received little attention so far. The present study provides an assessment of the Mediterranean-Atlantic exchange with a focus on the Atlantic inflow strength and its response to regional and global climate from 3.33 to 2.60 Ma. This time interval comprises the mid-Pliocene warm period (MPWP; 3.29-2.97 Ma) and the onset of the Northern Hemisphere glaciation (NHG). For this purpose, gradients in surface δ18O records of the planktonic foraminifer Globigerinoides ruber between the Integrated Ocean Drilling Program (IODP) Hole U1389E (Gulf of Cádiz) and Ocean Drilling Program (ODP) Hole 978A (Alboran Sea) have been evaluated. Interglacial stages and warm glacials of the MPWP revealed steep and reversed (relative to the present) W-E δ18O gradients suggesting a weakening of Mediterranean-Atlantic exchange likely caused by high levels of relative humidity in the Mediterranean region. In contrast, periods of stronger inflow are indicated by flat δ18O gradients due to more intense arid conditions during the severe glacial Marine Isotope Stage (MIS) M2 and the initiation of NHG (MIS G22, G14, G6-104). Intensified Mediterranean-Atlantic exchange in cold periods is linked to the occurrence of ice-rafted debris (IRD) at low latitudes and a weakening of the Atlantic Meridional Overturning Circulation (AMOC). Our results thus suggest the development of a negative feedback between AMOC and exchange rates at the Strait of Gibraltar in the latest Pliocene as it has been proposed for the late Quaternary.

The comparative phylogeography of east coast estuarine fishes in formerly glaciated sites: Persistence versus recolonization in Cyprinodon variegatus ovinus and Fundulus heteroclitus macrolepidotus.

PubMed

Haney, Robert A; Dionne, Michelle; Puritz, Jon; Rand, David M

2009-01-01

Species distributions may be dramatically affected by climatic variability, such as occurred during Pleistocene glaciation. Populations of coastal organisms could have been affected directly by ice movement or through sea level change. Response could involve shifts in distribution southwards or persistence through the full range or in limited high-latitude refugia. Comparative studies of the response of ecologically similar species can provide a useful complement to those examining response across disparate species in defining what parameters influence persistence. Patterns of mitochondrial genetic variation in 2 estuarine fish subspecies from the Northwest Atlantic, Fundulus heteroclitus macrolepidotus and Cyprinodon variegatus ovinus, indicate that ecological similarity does not necessarily predict propensity for glacial persistence. Fundulus heteroclitus macrolepidotus is highly diverse in glaciated regions, with isolated populations whose origins predate the last glacial maximum and may have recently expanded it's range to the south from New England. However, within glaciated regions, signals of population growth and distributional shifts indicate a dynamic Pleistocene history for F. h. macrolepidotus, in contrast with recent studies involving microsatellites. A different pattern is found in C. v. ovinus, which is depauperate in formerly glaciated sites, with a clear signal of recent recolonization of glaciated regions from the south. Genetic differentiation in glaciated areas is consistent with isolation after glacial withdrawal. In C. v. ovinus, rapidly evolving microsatellite loci show a similar pattern to mitochondrial DNA but may be reaching equilibrium on small spatial scales. These contrasting patterns of variation illustrate how ecologically similar species can respond to large-scale environmental change in distinct ways.

Antimicrobial Polymeric Materials with Quaternary Ammonium and Phosphonium Salts

PubMed Central

Xue, Yan; Xiao, Huining; Zhang, Yi

2015-01-01

Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers. PMID:25667977

Summary of Quaternary geology of the Municipality of Anchorage, Alaska

USGS Publications Warehouse

Schmoll, H.R.; Yehle, L.A.; Updike, R.G.

1999-01-01

Quaternary geology of the Upper Cook Inlet region is dominated by deposits of glacier retreats that followed repeated advances from both adjacent and more distant mountains. At several levels high on the mountains, there are remnant glacial deposits and other features of middle or older Pleistocene age. Late Pleistocene lateral moraines along the Chugach Mountain front represent successively younger positions of ice retreat from the last glacial maximum. As the trunk glacier retreated northeastward up the Anchorage lowland, Cook Inlet transgressed the area, depositing the Bootlegger Cove Formation and Tudor Road deposits. The glacier then readvanced to form the latest Pleistocene Elmendorf Moraine, a prominent feature that trends across the Anchorage lowland. Extensive alluvium was deposited both concurrently and somewhat later as Cook Inlet regressed. Mountain valleys contain (1) locally preserved moraines possibly of early Holocene age; (2) poorly preserved moraine remnants of older late Holocene age; and (3) well-preserved moraines formed mainly during the Little Ice Age. Glaciers still occupy large parts of the mountains, the upper ends of some mountain valleys, and small cirques. Holocene landslide deposits, including those formed during the great Alaska earthquake of 1964, occur throughout the area, especially along bluffs containing the Bootlegger Cove Formation.

Late quaternary paleoseismology of the southern Steens fault zone, northern Nevada

USGS Publications Warehouse

Personius, S.F.; Crone, A.J.; Machette, M.N.; Mahan, S.A.; Kyung, J.B.; Cisneros, H.; Lidke, D.J.

2007-01-01

The 192-km-long Steens fault zone is the most prominent normal fault system in the northern Basin and Range province of western North America. We use trench mapping and radiometric dating to estimate displacements and timing of the last three surface-rupturing earthquakes (E1-E3) on the southern part of the fault south of Denio, Nevada. Coseismic displacements range from 1.1 to 2.2 ?? 0.5 m, and radiometric ages indicate earthquake times of 11.5 ?? 2.0 ka (E3), 6.1 ?? 0.5 ka (E2), and 4.6 ?? 1.0 ka (E1). These data yield recurrence intervals of 5.4 ?? 2.1 k.y. between E3 and E2, 1.5 ?? 1.1 k.y. between E2 and E1, and an elapsed time of 4.6 ?? 1.0 k.y. since E1. The recurrence data yield variable interval slip rates (between 0.2 ?? 0.22 and 1.5 ?? 2.3 mm/yr), but slip rates averaged over the past ???18 k.y. (0.24 ?? 0.06 mm/year) are similar to long-term (8.5-12.5 Ma) slip rates (0.2 ?? 0.1 mm /yr) measured a few kilometers to the north. We infer from the lack of significant topographic relief across the fault in Bog Hot Valley that the fault zone is propagating southward and may now be connected with a fault at the northwestern end of the Pine Forest Range. Displacements documented in the trench and a rupture length of 37 km indicate a history of three latest Quaternary earthquakes with magnitudes of M 6.6-7.1 on the southern part of the Steens fault zone.

Palaeohydrological evolution of the late Cenozoic saline lake in the Qaidam Basin, NE Tibetan Plateau: Tectonic vs. climatic control

NASA Astrophysics Data System (ADS)

Guo, Pei; Liu, Chiyang; Huang, Lei; Yu, Mengli; Wang, Peng; Zhang, Guoqing

2018-06-01

As the largest Cenozoic terrestrial intermountain basin on the Tibetan Plateau, the Qaidam Basin is an ideal setting to understand the coupled controls of tectonics and climate on hydrological evolution. In this study, we used 47,846 data of carbonate and chloride contents from 146 boreholes to reconstruct the Neogene-Quaternary basin-wide hydrological evolution of the Qaidam Basin. Our results show that during the early Miocene (22-15 Ma), the palaeolake in the Qaidam Basin was mainly situated in the southwestern part of the basin, and its water was mostly brackish. From then on, this palaeolake progressively migrated southeastward, and its salinity increased from late Miocene saline water to Quaternary brines. This generally increasing trend of the water palaeosalinity during the late Cenozoic corresponded with regional and global climate changes at that time, suggesting the dominance of climatic control. However, the paces of the salinity increase from sediments in front of the three basin-bounding ranges were not the same, indicating that extra tectonic controls occurred. Sediments in front of the Eastern Kunlun Shan to the southwest and the Altyn Shan to the northwest showed an abrupt, dramatic increase in salinity at 15 Ma and 8 Ma, respectively; sediments in front of the Qilian Shan to the northeast showed steady increase without prominent, abrupt changes, indicating the occurrence of asynchronous tectonic controls from the basin-bounding ranges. The late Miocene depocentre migration was synchronous with the hydrological changes in front of the Altyn Shan, while the more significant migration during the Quaternary was consistent with the pulsing, intense extrabasinal and intrabasinal tectonic movements along the Tibetan Plateau.

Faulted terrace risers place new constraints on the late Quaternary slip rate for the central Altyn Tagh fault, northwest Tibet

USGS Publications Warehouse

Gold, R.D.; Cowgill, E.; Arrowsmith, J.R.; Chen, X.; Sharp, W.D.; Cooper, K.M.; Wang, X.-F.

2011-01-01

The active, left-lateral Altyn Tagh fault defines the northwestern margin of the Tibetan Plateau in western China. To clarify late Quaternary temporal and spatial variations in slip rate along the central portion of this fault system (85??-90??E), we have more than doubled the number of dated offset markers along the central Altyn Tagh fault. In particular, we determined offset-age relations for seven left-laterally faulted terrace risers at three sites (Kelutelage, Yukuang, and Keke Qiapu) spanning a 140-km-long fault reach by integrating surficial geologic mapping, topographic surveys (total station and tripod-light detection and ranging [T-LiDAR]), and geochronology (radiocarbon dating of organic samples, 230Th/U dating of pedogenic carbonate coatings on buried clasts, and terrestrial cosmogenic radionuclide exposure age dating applied to quartz-rich gravels). At Kelutelage, which is the westernmost site (37.72??N, 86.67??E), two faulted terrace risers are offset 58 ?? 3 m and 48 ?? 4 m, and formed at 6.2-6.1 ka and 5.9-3.7 ka, respectively. At the Yukuang site (38.00??N, 87.87??E), four faulted terrace risers are offset 92 ?? 12 m, 68 ?? 6 m, 55 ?? 13 m, and 59 ?? 9 m and formed at 24.2-9.5 ka, 6.4-5.0 ka, 5.1-3.9 ka, and 24.2-6.4 ka, respectively. At the easternmost site, Keke Qiapu (38.08??N, 88.12??E), a faulted terrace riser is offset 33 ?? 6 m and has an age of 17.1-2.2 ka. The displacement-age relationships derived from these markers can be satisfied by an approximately uniform slip rate of 8-12 mm/yr. However, additional analysis is required to test how much temporal variability in slip rate is permitted by this data set. ?? 2011 Geological Society of America.

The Terrestrial Paleoclimatic Record of the Late Quaternary as Revealed by Drilling Lake Titicaca, Peru/Bolivia

NASA Astrophysics Data System (ADS)

Baker, P. A.; Fritz, S. C.; Seltzer, G. O.; Ballantyne, A. P.; Rigsby, C. A.

2004-12-01

Seven drill cores were recovered from Lake Titicaca during the NSF/ICDP/DOSECC drilling expedition of 2001; our most detailed multi-proxy analyses have been done on Core 2B raised from 232 m water depth in the central basin of the lake. This site was drilled to 139 mblf with 141 m of total sediment recovered (101%). The recovered sediments consist of two main lithologies, organic- and inorganic-carbon-rich (often-laminated) muds that alternate with detrital-rich muds. These lithologies represent respectively low and high lakestand deposits. Proxies for water level include planktic-to-benthic diatom ratio, sedimentary carbonate content, and stable isotopic ratio of organic carbon. There are six highstand intervals separated by five lowstand intervals indicating that the level and volume of Lake Titicaca underwent several large changes during the late Quaternary. We infer from high values of magnetic susceptibility in most highstand muds that glacial advances in the surrounding Andes coincided with periods of relative wetness. During the most recent lowstand, in the early and middle Holocene, Lake Titicaca fell to 85 m below its modern level, salinity increased several-fold, and the downstream Salar de Uyuni desiccated. By contrast, throughout the LGM from ca. 25,000 cal BP to 15,000 cal BP, Lake Titicaca was deep and fresh, and overflowed southward to the Salar de Uyuni. Prior to the LGM, back to ca. 53,000 BP, the lake was predominantly fresh and overflowing. Pulses of increased benthic diatom abundance and inorganic carbon concentration during that time were likely due to episodes of downslope transport. We believe (based on U-Th dates of authigenic carbonate layers) that the penultimate lowstand of Lake Titicaca (seismic evidence indicates a lake level 200 m lower than today) was coincident with MIS 5. We recovered sediments recording three older lowstands, each separated by periods in which the lake freshened dramatically and when glaciers apparently advanced in

Consistent role of Quaternary climate change in shaping current plant functional diversity patterns across European plant orders.

PubMed

Ordonez, Alejandro; Svenning, Jens-Christian

2017-02-23

Current and historical environmental conditions are known to determine jointly contemporary species distributions and richness patterns. However, whether historical dynamics in species distributions and richness translate to functional diversity patterns remains, for the most part, unknown. The geographic patterns of plant functional space size (richness) and packing (dispersion) for six widely distributed orders of European angiosperms were estimated using atlas distribution data and trait information. Then the relative importance of late-Quaternary glacial-interglacial climate change and contemporary environmental factors (climate, productivity, and topography) as determinants of functional diversity of evaluated orders was assesed. Functional diversity patterns of all evaluated orders exhibited prominent glacial-interglacial climate change imprints, complementing the influence of contemporary environmental conditions. The importance of Quaternary glacial-interglacial climate change factors was comparable to that of contemporary environmental factors across evaluated orders. Therefore, high long-term paleoclimate variability has imposed consistent supplementary constraints on functional diversity of multiple plant groups, a legacy that may permeate to ecosystem functioning and resilience. These findings suggest that strong near-future anthropogenic climate change may elicit long-term functional disequilibria in plant functional diversity.

Episode of intense chemical weathering during the termination of the 635 Ma Marinoan glaciation

PubMed Central

Huang, Kang-Jun; Teng, Fang-Zhen; Shen, Bing; Xiao, Shuhai; Lang, Xianguo; Ma, Hao-Ran; Fu, Yong; Peng, Yongbo

2016-01-01

Cryogenian (∼720–635 Ma) global glaciations (the snowball Earth) represent the most extreme ice ages in Earth’s history. The termination of these snowball Earth glaciations is marked by the global precipitation of cap carbonates, which are interpreted to have been driven by intense chemical weathering on continents. However, direct geochemical evidence for the intense chemical weathering in the aftermath of snowball glaciations is lacking. Here, we report Mg isotopic data from the terminal Cryogenian or Marinoan-age Nantuo Formation and the overlying cap carbonate of the basal Doushantuo Formation in South China. A positive excursion of extremely high δ26Mg values (+0.56 to +0.95)—indicative of an episode of intense chemical weathering—occurs in the top Nantuo Formation, whereas the siliciclastic component of the overlying Doushantuo cap carbonate has significantly lower δ26Mg values (<+0.40), suggesting moderate to low intensity of chemical weathering during cap carbonate deposition. These observations suggest that cap carbonate deposition postdates the climax of chemical weathering, probably because of the suppression of carbonate precipitation in an acidified ocean when atmospheric CO2 concentration was high. Cap carbonate deposition did not occur until chemical weathering had consumed substantial amounts of atmospheric CO2 and accumulated high levels of oceanic alkalinity. Our finding confirms intense chemical weathering at the onset of deglaciation but indicates that the maximum weathering predated cap carbonate deposition. PMID:27956606

Synthesis and anticoagulant activity of the quaternary ammonium chitosan sulfates.

PubMed

Fan, Lihong; Wu, Penghui; Zhang, Jinrong; Gao, Song; Wang, Libo; Li, Mingjia; Sha, Mingming; Xie, Weiguo; Nie, Min

2012-01-01

Quaternary ammonium chitosan sulfates with diverse degrees of substitution (DS) ascribed to sulfate groups between 0.52 and 1.55 were synthesized by reacting quaternary ammonium chitosan with an uncommon sulfating agent (N(SO(3)Na)(3)) that was prepared from sodium bisulfite (NaHSO(3)) through reaction with sodium nitrite (NaNO(2)) in the aqueous system homogeneous. The structures of the derivatives were characterized by FTIR, (1)H NMR and (13)C NMR. The factors affecting DS of quaternary ammonium chitosan sulfates which included the molar ratio of NaNO(2) to quaternary ammonium chitosan, sulfated temperature, sulfated time and pH of sulfated reaction solution were investigated in detail. Its anticoagulation activity in vitro was determined by an activated partial thromboplastin time (APTT) assay, a thrombin time (TT) assay and a prothrombin time (PT) assay. Results of anticoagulation assays showed quaternary ammonium chitosan sulfates significantly prolonged APTT and TT, but not PT, and demonstrated that the introduction of sulfate groups into the quaternary ammonium chitosan structure improved its anticoagulant activity obviously. The study showed its anticoagulant properties strongly depended on its DS, concentration and molecular weight. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

Quaternary Sea-ice history in the Arctic Ocean based on a new Ostracode sea-ice proxy

USGS Publications Warehouse

Cronin, T. M.; Gemery, L.; Briggs, W.M.; Jakobsson, M.; Polyak, L.; Brouwers, E.M.

2010-01-01

Paleo-sea-ice history in the Arctic Ocean was reconstructed using the sea-ice dwelling ostracode Acetabulastoma arcticum from late Quaternary sediments from the Mendeleyev, Lomonosov, and Gakkel Ridges, the Morris Jesup Rise and the Yermak Plateau. Results suggest intermittently high levels of perennial sea ice in the central Arctic Ocean during Marine Isotope Stage (MIS) 3 (25-45 ka), minimal sea ice during the last deglacial (16-11 ka) and early Holocene thermal maximum (11-5 ka) and increasing sea ice during the mid-to-late Holocene (5-0 ka). Sediment core records from the Iceland and Rockall Plateaus show that perennial sea ice existed in these regions only during glacial intervals MIS 2, 4, and 6. These results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon. ?? 2010.

Quaternary fossil fish from the Kibish Formation, Omo Valley, Ethiopia.

PubMed

Trapani, Josh

2008-09-01

The late Quaternary Kibish Formation of the Omo Valley, southwestern Ethiopia, preserves environments reflecting a history of fluctuations in the level of nearby Lake Turkana over the past 200,000 years. The Kibish Formation has yielded a diverse mammalian fauna (as well as birds and crocodiles), stone tools, and the oldest anatomically modern Homo sapiens. Fish, the most common vertebrate fossils in this unit, are reported in this study. Catfish (especially clariids and Synodontis) and Nile perch (Lates niloticus) predominate, but the gymnarchid Gymnarchus, a cyprinid (Barbus), tigerfish (Hydrocynus), pufferfish (Tetraodon), and other catfish are also present. In total, nine teleost genera are found in the Kibish Formation, representing a subset of the 37 genera that constitute the modern Omo-Turkana ichthyofauna. Several taxa present in the modern fauna, including Polypterus and members of the family Cichlidae, are not found in the Kibish deposits. Most specimens are preserved as disarticulated or broken skeletal elements, but some preservation of articulated elements (e.g., sets of vertebrae, crania with lower jaws or cleithra) also occurs. Many of the catfish and Nile perch specimens are larger than the largest reported from the modern river or lake. Faunas of Kibish Members I and III closely resemble one another; the fauna from Member IV contains only the three most common taxa (Clarias, Synodontis, Lates), though this may result from insufficient sampling. Barbed bone points have been collected from the upper part of the formation, indicating a long association between the human inhabitants and the fish fauna of the Omo Valley.

Drifting propagules and receding swamps: genetic footprints of mangrove recolonization and dispersal along tropical coasts.

PubMed

Nettel, Alejandro; Dodd, Richard S

2007-04-01

Two issues that have captured the attention of tropical plant evolutionary biologists in recent years are the relative role of long distance dispersal (LDD) over vicariance in determining plant distributions and debate about the extent that Quaternary climatic changes affected tropical species. Propagules of some mangrove species are assumed to be capable of LDD due to their ability to float and survive for long periods of time in salt water. Mangrove species responded to glaciations with a contraction of their range. Thus, widespread mangrove species are an ideal system to study LDD and recolonization in the tropics. We present phylogenetic and phylogeographic analyses based on internal transcribed spacers region (ITS) sequences, chloroplast DNA (cpDNA), and amplified fragment length polymorphisms (AFLPs) of genomic DNA that demonstrate recent LDD across the Atlantic, rejecting the hypothesis of vicariance for the widespread distribution of the black mangrove (Avicennia germinans). Northern latitude populations likely became extinct during the late Quaternary due to frosts and aridification; these locations were recolonized afterward from southern populations. In some low latitude regions populations went extinct or were drastically reduced during the Quaternary because of lack of suitable habitat as sea levels changed. Our analyses show that low latitude Pacific populations of A. germinans harbor more diversity and reveal deeper divergence than Atlantic populations. Implications for our understanding of phylogeography of tropical species are discussed.