Science.gov

Sample records for early holocene site

  1. Record of the early Holocene deglaciation from the East Antarctic Adélie Land margin: IODP Site U1357

    NASA Astrophysics Data System (ADS)

    Escutia, Carlota; Jimenez-Espejo, Francisco; Salabarnada, Ariadna; Gitiérrez-Pastor, Julia

    2015-04-01

    Drilling at Site U1357 yielded a 185.6 m section of Holocene continuously laminated diatom ooze as well as a portion of an underlying Last Glacial Maximum diamict. We present sedimentological and geochemical data of the time of the first Holocene deglaciation. The use of CT-Scanner has allowed us to characterize in detail sedimentary facies dominated by iceberg rafted debris, silt layers and biogenic laminations. In addition, geochemical studies have been conducted at ultra-high (seasonal to decadal) resolution using X-Ray Fluorescence scanning, allowing to reconstruct detrital input, paleoproducitivity and redox conditions. Comparison between CT-Scan images and geochemical data show that the intervals with high Ba/Al and Si/Al are associated to poor detrital levels allowing to use these ratios along the entire core as detrital/paleoproductivity proxies. Detrital proxies (e.g., Zr content) anticorrelate with bottom redox conditions proxies (U/Th) pointing to well oxygenated deep waters as generator for silt layers. These preliminary observations point to an unprecedented high resolution ice fjord-like sequence in the studied region with strong water column stratification and pulsational detrital input acting as a main forcing for environmental variations. Ongoing radiocarbon analysis, performed in the bulk fraction and also in compound-specific, will allow us to recognize timing, cylces and if major variations occurred in the reservoir age during the deglaciation.

  2. Late Pleistocene and Early Holocene lake-level fluctuations in the Lahontan Basin, Nevada: Implications for the distribution of archaeological sites

    USGS Publications Warehouse

    Adams, K.D.; Goebel, Thomas; Graf, K.; Smith, G.M.; Camp, A.J.; Briggs, R.W.; Rhode, D.

    2008-01-01

    The Great Basin of the western U.S. contains a rich record of late Pleistocene and Holocene lake-level fluctuations as well as an extensive record of human occupation during the same time frame. We compare spatial-temporal relationships between these records in the Lahontan basin to consider whether lake-level fluctuations across the Pleistocene-Holocene transition controlled distribution of archaeological sites. We use the reasonably well-dated archaeological record from caves and rockshelters as well as results from new pedestrian surveys to investigate this problem. Although lake levels probably reached maximum elevations of about 1230-1235 m in the different subbasins of Lahontan during the Younger Dryas (YD) period, the duration that the lakes occupied the highest levels was brief Paleoindian and early Archaic archaeological sites are concentrated on somewhat lower and slightly younger shorelines (???1220-1225 in) that also date from the Younger Dryas period. This study suggests that Paleoindians often concentrated their activities adjacent to large lakes and wetland resources soon after they first entered the Great Basin. ?? 2008 Wiley Periodicals, Inc.

  3. Paleoparasitological finding of eggs of nematodes in rodent coprolites dated at the early Holocene from the archaeological site Cerro Casa de Piedra 7, Santa Cruz, Argentina.

    PubMed

    Sardella, N H; Fugassa, M H

    2011-12-01

    The aim of the present study was to examine the parasite remains present in rodent coprolites collected from the archaeological site Cerro Casa de Piedra 7 (CCP7), located in the Perito Moreno National Park (47°57'S, 72°05'W), Santa Cruz Province, Argentina. Eight coprolites obtained from the layer 17, dated at 10,620 ± 40 to 9,390 ± 40 yr B.P., were examined for parasites. Feces were processed whole, rehydrated, homogenized, subjected to spontaneous sedimentation, and examined via light microscopy. Eggs of parasites were measured and photographed. Seven of 8 coprolites possessed 199 eggs of 2, probably new, species of nematodes, including 43 eggs of Heteroxynema sp. Hall, 1916 (Cavioxyura sp. Quentin, 1975) (Oxyurida, Heteroxynematidae), and 156 eggs of Trichuris sp. Roederer, 1761 (Trichinellida, Trichuridae). Heteroxynema sp. is cited for the first time from ancient material worldwide. The finding of Trichuris spp. in both rodents and other host samples from the area under study is indicative of the stability of the biological and environmental conditions for this nematode genus to establish in the Patagonian Early Holocene. The rodent host was assigned to an unknown species of Caviomorpha (Hystricognathi) that lived during the Pleistocenic transition in Patagonia. PMID:21671716

  4. Early Holocene glacier advance, southern Coast Mountains, British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Koch, Johannes; Osborn, Gerald; Clague, John J.; Mazzucchi, David

    2004-07-01

    Terrestrial and lake sediment records from several sites in the southern Coast Mountains, British Columbia, provide evidence for an advance of alpine glaciers during the early Holocene. Silty intervals within organic sediments recovered from two proglacial lakes are bracketed by AMS 14C-dated terrestrial macrofossils and Mazama tephra to 8780-6730 and 7940- 6730 14C yr BP [10,150-7510 and 8990- 7510 cal yr BP]. Radiocarbon ages ranging from 7720 to 7380 14C yr BP [8630- 8020 cal yr BP] were obtained from detrital wood in recently deglaciated forefields of Sphinx and Sentinel glaciers. These data, together with previously published data from proglacial lakes in the Canadian Rockies, imply that glaciers in western Canada advanced during the early Holocene. The advance coincides with the well-documented 8200-yr cold event identified in climate proxy data sets in the North Atlantic region and elsewhere.

  5. Early Holocene hydrology and environments of the Ner River (Poland)

    NASA Astrophysics Data System (ADS)

    Kittel, Piotr; Płóciennik, Mateusz; Borówka, Ryszard K.; Okupny, Daniel; Pawłowski, Dominik; Peyron, Odille; Stachowicz-Rybka, Renata; Obremska, Milena; Cywa, Katarzyna

    2016-03-01

    The Ner River valley (central Poland) underwent substantial transformation during the Weichselian-Holocene transition as a result of fluvial processes and climate changes, resulting in the establishment of its present shape in the Holocene. A multiproxy study based on organic deposits from a palaeochannel fill (Lutomiersk-Koziówki) shows that after the channel was cut off during the late glacial termination, it became a shallow oxbow, fed by local springs. In the Boreal period, the oxbow lake was also fed by precipitation and became a telmatic environment overgrown by rush and swamp vegetation. Finally, it was covered by overbank deposits. The first flooding phase (9900-9600 cal. BP) was followed by the accumulation of overbank sediments (after 9500 cal. BP) and flooding increased after ca. 9300-9000 cal. BP. Pollen data provide information on the regional vegetation context for local and regional changes. In the Atlantic period, an increase in both summer and winter temperatures is inferred from the pollen data, corresponding to an expansion of thermophilous deciduous forests. While in general, flooding phases of the Early Holocene are poorly recognised in Eastern Europe, the Lutomiersk-Koziówki site may be considered as one of the reference points for this phenomenon in the region.

  6. Technological Analysis of the World’s Earliest Shamanic Costume: A Multi-Scalar, Experimental Study of a Red Deer Headdress from the Early Holocene Site of Star Carr, North Yorkshire, UK

    PubMed Central

    Little, Aimée; Elliott, Benjamin; Conneller, Chantal; Pomstra, Diederik; Evans, Adrian A.; Fitton, Laura C.; Holland, Andrew; Davis, Robert; Kershaw, Rachel; O’Connor, Sonia; O’Connor, Terry; Sparrow, Thomas; Wilson, Andrew S.; Jordan, Peter; Collins, Matthew J.; Colonese, André Carlo; Craig, Oliver E.; Knight, Rebecca; Lucquin, Alexandre J. A.; Taylor, Barry; Milner, Nicky

    2016-01-01

    Shamanic belief systems represent the first form of religious practice visible within the global archaeological record. Here we report on the earliest known evidence of shamanic costume: modified red deer crania headdresses from the Early Holocene site of Star Carr (c. 11 kya). More than 90% of the examples from prehistoric Europe come from this one site, establishing it as a place of outstanding shamanistic/cosmological significance. Our work, involving a programme of experimental replication, analysis of macroscopic traces, organic residue analysis and 3D image acquisition, metrology and visualisation, represents the first attempt to understand the manufacturing processes used to create these artefacts. The results produced were unexpected—rather than being carefully crafted objects, elements of their production can only be described as expedient. PMID:27073850

  7. Early and Middle Holocene Hunter-Gatherer Occupations in Western Amazonia: The Hidden Shell Middens

    PubMed Central

    Lombardo, Umberto; Szabo, Katherine; Capriles, José M.; May, Jan-Hendrik; Amelung, Wulf; Hutterer, Rainer; Lehndorff, Eva; Plotzki, Anna; Veit, Heinz

    2013-01-01

    We report on previously unknown early archaeological sites in the Bolivian lowlands, demonstrating for the first time early and middle Holocene human presence in western Amazonia. Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region. The absence of stone resources and partial burial by recent alluvial sediments has meant that these kinds of deposits have, until now, remained unidentified. We conducted core sampling, archaeological excavations and an interdisciplinary study of the stratigraphy and recovered materials from three shell midden mounds. Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites. In a tropical and geomorphologically active landscape often considered challenging both for early human occupation and for the preservation of hunter-gatherer sites, the newly discovered shell middens provide evidence for early to middle Holocene occupation and illustrate the potential for identifying and interpreting early open-air archaeological sites in western Amazonia. The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region’s past and offers a new context within which the late Holocene “Earthmovers” of the Llanos de Moxos could have emerged. PMID:24013964

  8. Rapid deglacial and early Holocene expansion of peatlands in Alaska

    PubMed Central

    Jones, Miriam C.; Yu, Zicheng

    2010-01-01

    Northern peatlands represent one of the largest biospheric carbon (C) reservoirs; however, the role of peatlands in the global carbon cycle remains intensely debated, owing in part to the paucity of detailed regional datasets and the complexity of the role of climate, ecosystem processes, and environmental factors in controlling peatland C dynamics. Here we used detailed C accumulation data from four peatlands and a compilation of peatland initiation ages across Alaska to examine Holocene peatland dynamics and climate sensitivity. We find that 75% of dated peatlands in Alaska initiated before 8,600 years ago and that early Holocene C accumulation rates were four times higher than the rest of the Holocene. Similar rapid peatland expansion occurred in West Siberia during the Holocene thermal maximum (HTM). Our results suggest that high summer temperature and strong seasonality during the HTM in Alaska might have played a major role in causing the highest rates of C accumulation and peatland expansion. The rapid peatland expansion and C accumulation in these vast regions contributed significantly to the peak of atmospheric methane concentrations in the early Holocene. Furthermore, we find that Alaskan peatlands began expanding much earlier than peatlands in other regions, indicating an important contribution of these peatlands to the pre-Holocene increase in atmospheric methane concentrations. PMID:20368451

  9. Plant macrofossil evidence for an early onset of the Holocene summer thermal maximum in northernmost Europe

    PubMed Central

    Väliranta, M.; Salonen, J. S.; Heikkilä, M.; Amon, L.; Helmens, K.; Klimaschewski, A.; Kuhry, P.; Kultti, S.; Poska, A.; Shala, S.; Veski, S.; Birks, H. H.

    2015-01-01

    Holocene summer temperature reconstructions from northern Europe based on sedimentary pollen records suggest an onset of peak summer warmth around 9,000 years ago. However, pollen-based temperature reconstructions are largely driven by changes in the proportions of tree taxa, and thus the early-Holocene warming signal may be delayed due to the geographical disequilibrium between climate and tree populations. Here we show that quantitative summer-temperature estimates in northern Europe based on macrofossils of aquatic plants are in many cases ca. 2 °C warmer in the early Holocene (11,700–7,500 years ago) than reconstructions based on pollen data. When the lag in potential tree establishment becomes imperceptible in the mid-Holocene (7,500 years ago), the reconstructed temperatures converge at all study sites. We demonstrate that aquatic plant macrofossil records can provide additional and informative insights into early-Holocene temperature evolution in northernmost Europe and suggest further validation of early post-glacial climate development based on multi-proxy data syntheses. PMID:25858780

  10. Early- to mid-Holocene vegetation development in northern Iceland: project outline and preliminary results

    NASA Astrophysics Data System (ADS)

    Eddudóttir, S.; Erlendsson, E.; Gísladóttir, G.

    2013-12-01

    Iceland is a key site for the study of Holocene vegetation and climate variations due to its location in the North Atlantic. The aim of the project is to reconstruct the history of Holocene vegetation development in Austur-Húnavatnssýsla, northern Iceland. Using pollen and macrofossils, patterns of vegetation change in three locations will be reconstructed, forming a transect from coastal extremes to the highland margin. The palynological and macrofossil data will be combined with a robust regional chronology, constructed by combining tephra layers with radiocarbon-dated macrofossils. Available data covering the vegetation history of Iceland are scarce. This study will improve the understanding of how environmental factors have driven vegetation development during the Holocene. Pollen analysis has been carried out on a section of a lacustrine core from the first study site of this project, a lowland site in Svínadalur valley. The analysed section of the core covers the period from Younger Dryas to the mid-Holocene. The results show a transition from pioneering vegetation during the cold period of Younger Dryas to the birch forests of the Holocene Thermal Maximum. An initial expansion of birch and gradual closing of vegetation cover was halted during early-Holocene, probably due to a period of cooling climate. An age model for the core has yet to be constructed, however this change in vegetation may be the result of cooling during the 8.2 ka event that has previously been recorded in proxies from Icelandic lakes. This cooling event has however not been seen in Icelandic terrestrial biotic palaeorecords before. The impact of this event seen in the Svínadalur core may underscore a vulnerability of the early-Holocene terrestrial ecosystem to climatic fluctuations. The study is funded by the Eimskip University fund, University of Iceland Research Fund and Landsvirkjun's Energy Research Fund, the study is also supported by the INTIMATE EU COST action in the form of a

  11. Early Holocene chicken domestication in northern China

    PubMed Central

    Xiang, Hai; Gao, Jianqiang; Yu, Baoquan; Zhou, Hui; Cai, Dawei; Zhang, Youwen; Chen, Xiaoyong; Wang, Xi; Hofreiter, Michael; Zhao, Xingbo

    2014-01-01

    Chickens represent by far the most important poultry species, yet the number, locations, and timings of their domestication have remained controversial for more than a century. Here we report ancient mitochondrial DNA sequences from the earliest archaeological chicken bones from China, dating back to ∼10,000 B.P. The results clearly show that all investigated bones, including the oldest from the Nanzhuangtou site, are derived from the genus Gallus, rather than any other related genus, such as Phasianus. Our analyses also suggest that northern China represents one region of the earliest chicken domestication, possibly dating as early as 10,000 y B.P. Similar to the evidence from pig domestication, our results suggest that these early domesticated chickens contributed to the gene pool of modern chicken populations. Moreover, our results support the idea that multiple members of the genus Gallus, specifically Gallus gallus and Gallus sonneratii contributed to the gene pool of the modern domestic chicken. Our results provide further support for the growing evidence of an early mixed agricultural complex in northern China. PMID:25422439

  12. Early Holocene pecan, Carya illinoensis, in the Mississippi River Valley near Muscatine, Iowa

    USGS Publications Warehouse

    Bettis, E. Arthur, III; Baker, R.G.; Nations, B.K.; Benn, D.W.

    1990-01-01

    A fossil pecan, Carya illinoensis (Wang.) K. Koch, from floodplain sediments of the Mississippi River near Muscatine, Iowa, was accelerator-dated at 7280 ?? 120 yr B.P. This discovery indicates that pecan was at or near its present northern limit by that time. Carya pollen profiles from the Mississippi River Trench indicate that hickory pollen percentages were much higher in the valley than at upland locations during the early Holocene. Pecan, the hickory with the most restricted riparian habitat, is the likely candidate for producing these peaks in Carya pollen percentages. Therefore, pecan may have reached its northern limit as early as 10,300 yr B.P. Its abundance in Early Archaic archaeological sites and the co-occurrence of early Holocene Carya pollen peaks with the arrival of the Dalton artifact complex in the Upper Mississippi Valley suggest that humans may have played a role in the early dispersal of pecan. ?? 1990.

  13. Early Holocene pecan, Carya illinoensis, in the Mississippi River Valley near Muscatine, Iowa*1

    NASA Astrophysics Data System (ADS)

    Bettis, E. Arthur; Baker, Richard G.; Nations, Brenda K.; Benn, David W.

    1990-01-01

    A fossil pecan, Carya illinoensis (Wang.) K. Koch, from floodplain sediments of the Mississippi River near Muscatine, Iowa, was accelerator-dated at 7280 ± 120 yr B.P. This discovery indicates that pecan was at or near its present northern limit by that time. Carya pollen profiles from the Mississippi River Trench indicate that hickory pollen percentages were much higher in the valley than at upland locations during the early Holocene. Pecan, the hickory with the most restricted riparian habitat, is the likely candidate for producing these peaks in Carya pollen percentages. Therefore, pecan may have reached its northern limit as early as 10,300 yr B.P. Its abundance in Early Archaic archaeological sites and the co-occurrence of early Holocene Carya pollen peaks with the arrival of the Dalton artifact complex in the Upper Mississippi Valley suggest that humans may have played a role in the early dispersal of pecan.

  14. Early and late Holocene glacial fluctuations and tephrostratigraphy, Cabin Lake, Alaska

    USGS Publications Warehouse

    Zander, Paul D.; Kaufman, Darrell S.; Kuehn, Stephen C.; Wallace, Kristi L.; Anderson, R. Scott

    2013-01-01

    Marked changes in sediment types deposited in Cabin Lake, near Cordova, Alaska, represent environmental shifts during the early and late Holocene, including fluctuations in the terminal position of Sheridan Glacier. Cabin Lake is situated to receive meltwater during periods when the outwash plain of the advancing Sheridan Glacier had aggraded. A brief early Holocene advance from 11.2 to 11.0 cal ka is represented by glacial rock flour near the base of the sediment core. Non-glacial lake conditions were restored for about 1000 years before the water level in Cabin Lake lowered and the core site became a fen. The fen indicates drier-than-present conditions leading up to the Holocene thermal maximum. An unconformity spanning 5400 years during the mid-Holocene is overlain by peat until 1110 CE when meltwater from Sheridan Glacier returned to the basin. Three intervals of an advanced Sheridan Glacier are recorded in the Cabin Lake sediments during the late Holocene: 1110–1180, 1260–1540 and 1610–1780 CE. The sedimentary sequence also contains the first five reported tephra deposits from the Copper River delta region, and their geochemical signatures suggest that the sources are the Cook Inlet volcanoes Redoubt, Augustine and Crater Peak, and possibly Mt Churchill in the Wrangell Volcanic field.

  15. Reorganization of the North Atlantic Oscillation during early Holocene deglaciation

    NASA Astrophysics Data System (ADS)

    Wassenburg, Jasper A.; Dietrich, Stephan; Fietzke, Jan; Fohlmeister, Jens; Jochum, Klaus Peter; Scholz, Denis; Richter, Detlev K.; Sabaoui, Abdellah; Spötl, Christoph; Lohmann, Gerrit; Andreae, Meinrat O.; Immenhauser, Adrian

    2016-08-01

    The North Atlantic Oscillation is the dominant atmospheric pressure mode in the North Atlantic region and affects winter temperature and precipitation in the Mediterranean, northwest Europe, Greenland, and Asia. The index that describes the sea-level pressure difference between Iceland and the Azores is correlated with a dipole precipitation pattern over northwest Europe and northwest Africa. How the North Atlantic Oscillation will develop as the Greenland ice sheet melts is unclear. A potential past analogue is the early Holocene, during which melting ice sheets around the North Atlantic freshened surface waters, affecting the strength of the meridional overturning circulation. Here we present a Holocene rainfall record from northwest Africa based on speleothem δ18O and compare it against a speleothem-based rainfall record from Europe. The two records are positively correlated during the early Holocene, followed by a shift to an anti-correlation, similar to the modern record, during the mid-Holocene. On the basis of our simulations with an Earth system model, we suggest the shift to the anti-correlation reflects a large-scale atmospheric and oceanic reorganization in response to the demise of the Laurentide ice sheet and a strong reduction of meltwater flux to the North Atlantic, pointing to a potential sensitivity of the North Atlantic Oscillation to the melting of ice sheets.

  16. Cold Water Coral Mounds and Early Holocene Climate Change

    NASA Astrophysics Data System (ADS)

    Readman, P. W.; O'Reilly, B. M.; Shannon, P. M.

    2003-12-01

    Cold-water coral mounds occur in discrete clustered populations over a broad region from the glaciated Norwegian continental margins to the non-glaciated margins of Iberia and northwest Africa. They are potentially sensitive indicators of change in oceanic circulation, coupled to past climate change. Here we report on an interesting correlation between the Holocene growth of a mound population west of Ireland and early Holocene palaeoclimatic variations in the North Atlantic region, notably the well documented 8.2 kyr cold event. An accurate age structure for the mound population is calculated using recent growth rate estimates for the main coral framework constructor L. pertusa and a previously formulated population growth model. The calculated curve for the Holocene period fits the observed population data well, except for a pronounced and significant deflection in the data trend beginning at about 8500 calendar years (cal. yr) ago in the early Holocene. This date corresponds to the time (~8470 cal. yr) that the glacial lakes Agassiz and Ojibway, which were once dammed by a remnant of the Laurentide ice sheet, drained catastrophically into the Labrador sea releasing >1014 m3 of fresh water. The 8.2 kyr event had as much a global effect on the large-scale structure of deep-water aphotic ecosystems as it did on continental shelf and terrestrial ecosystems.

  17. Early Holocene Great Salt Lake, USA

    NASA Astrophysics Data System (ADS)

    Oviatt, Charles G.; Madsen, David B.; Miller, David M.; Thompson, Robert S.; McGeehin, John P.

    2015-07-01

    Shorelines and surficial deposits (including buried forest-floor mats and organic-rich wetland sediments) show that Great Salt Lake did not rise higher than modern lake levels during the earliest Holocene (11.5-10.2 cal ka BP; 10-9 14C ka BP). During that period, finely laminated, organic-rich muds (sapropel) containing brine-shrimp cysts and pellets and interbedded sodium-sulfate salts were deposited on the lake floor. Sapropel deposition was probably caused by stratification of the water column - a freshwater cap possibly was formed by groundwater, which had been stored in upland aquifers during the immediately preceding late-Pleistocene deep-lake cycle (Lake Bonneville), and was actively discharging on the basin floor. A climate characterized by low precipitation and runoff, combined with local areas of groundwater discharge in piedmont settings, could explain the apparent conflict between evidence for a shallow lake (a dry climate) and previously published interpretations for a moist climate in the Great Salt Lake basin of the eastern Great Basin.

  18. Biogeochemical inferences of mobility of early Holocene fisher-foragers from the Southern Sahara Desert.

    PubMed

    Stojanowski, Christopher M; Knudson, Kelly J

    2011-09-01

    North Africa is increasingly seen as an important context for understanding modern human evolution and reconstructing biocultural adaptations. The Sahara, in particular, witnessed a fluorescence of hunter-gatherer settlement at the onset of the Holocene after an extended occupational hiatus. Subsequent subsistence changes through the Holocene are contrary to those documented in other areas where mobile foraging gave way to settled agricultural village life. In North Africa, extractive fishing and hunting was supplanted by cattle and caprine pastoralism under deteriorating climatic conditions. Therefore, the initial stage of food production in North Africa witnessed a likely increase in mobility. However, there are few studies of paleomobility in Early Holocene hunter-gatherer Saharan populations and the degree of mobility is generally assumed. Here, we present radiogenic strontium isotope ratios from Early Holocene fisher-forager peoples from the site of Gobero, central Niger, southern Sahara Desert. Data indicate a relatively homogeneous radiogenic strontium isotope signature for this hunter-gather population with limited variability exhibited throughout the life course or among different individuals. Although the overall signature was local, some variation in the radiogenic strontium isotope data likely reflects transhumance into the nearby Aïr Massif. Data from Gobero were significantly less variable than in other worldwide hunter-gatherer populations, including those thought to be fairly sedentary. Strontium data from Gobero were also significantly different from contemporaneous sites in southwestern Libya. These patterns are discussed with respect to archaeological models of community organization and technological evolution. PMID:21766285

  19. Early Holocene meltwater events in the Labrador Sea

    NASA Astrophysics Data System (ADS)

    Pearce, Christof; Jennings, Anne; Andrews, John; Hillaire-Marcel, Claude; Seidenkrantz, Marit-Solveig; Lewis, Mike

    2016-04-01

    During the early Holocene, the Labrador Sea was strongly influenced by the presence of the remainder of the Laurentide Ice Sheet and its active eastern margin. Glacial advances and retreats lead to episodic release of meltwater and icebergs with potential impact on ocean circulation and climate during the deglaciation. The purpose of this study is to use detrital carbonate (DC) records in the Labrador Sea to study the spatial variability of the carbonate events and inferred sources and routing of glacial meltwater originating from Hudson Strait (HS) as well as potential contributions from Northern Baffin Bay (NBB) ice sheet margins. We use DC in sediment cores as a proxy for glacial meltwater and ice berg drift from these areas. More than 20 sediment cores with published DC, stable oxygen isotope, and radiocarbon stratigraphies provide the data for this study. Our hypothesis is that the complex interplay of current systems, shelf and slope bathymetry and location of meltwater and ice berg injection points will affect the spatial distribution of the DC events. In addition, differences in local ocean reservoir age for shelf, slope and open ocean sites may also contribute to offsets in the apparent ages of DC events. Identification of DC peaks also is influenced by sedimentation rates and sampling resolution. To objectively correlate DC events, we study mostly published core data, removing all earlier assumptions about marine reservoir ages and assess all core chronologies with their associated errors. Our results show that none of the DC events is found in all sites and no record captures all of the DC events. Despite this, some of the larger events occur in several records and allow robust temporal and spatial mapping of the meltwater pathways. Besides the meltwater route due south along the Labrador margin on the shelf, some events show a clear signal in deeper Labrador Sea sites pointing at a more direct injection of freshwater in the subpolar gyre.

  20. What happened to El Nino during the early Holocene?

    NASA Astrophysics Data System (ADS)

    Philander, S. G.

    2002-12-01

    Coral records from the tropical Pacific indicate that interannual fluctuations associated with El Nino today were absent during the early Holocene until approximately 5000 years ago. Some authors claim that, at that time, the waters off Ecuador and northern Peru were permanently warm, but explaining the persistence of arid conditions along the coast is then a problem. Another ossibility, supported by some measurements, is that El Nino occurred less often, every decade or so. To theoreticians, these findings raise two sets of questions. First, El Nino can be regarded as part of a natural mode of oscillation that depends on background conditions such as H the mean depth of the thermocline, TX the intensity of the mean winds etc. What changes in the background conditions, in values of H, TX etc, will result in either permanently warm conditions, or El Nino with a very low frequency? Stability analyses of ocean-atmosphere interactions indicate that if the thermocline was deeper than today, then weak winds would have resulted in permanently warm conditions, but strong trades would have resulted in infrequent El Nino episodes. Next we have to ask why the background conditions changed. During the Holocene precession of the Earth¡s axis caused first the northern hemisphere, then the southern hemisphere to experience warmer summers, colder winters. As a result the Sahara had lakes, Lake Titicaca was dry, and apparently the trade winds were strong during the early Holocene. To test the inference that El Nino became a very low frequency phenomenon during the early Holocene requires information about the depth of the thermocline and the intensity of the trades at that time.

  1. Patterns and drivers of Early Holocene vegetation dynamics in Central Europe

    NASA Astrophysics Data System (ADS)

    Theuerkauf, Martin

    2015-04-01

    The rapid warming of the Holocene induced the rearrangement of vegetation across Europe, including the widely synchronous and rapid expansion of hazel (Corylus avellana) at around 10.6 ka BP (Giesecke et al., 2011). The simultaneity of the hazel expansion across large parts of Europe suggests that a climate shift has triggered that expansion. However, it remains poorly understood, which climate parameter has been effective (Huntley, 1993) because hazel expanded simultaneously in areas that today clearly differ in climate. To better understand the causes we studied Early Holocene vegetation dynamics in NE Germany in high temporal and spatial resolution. Analysis combines pollen data from 60 sites, including high resolution data sets, with present-day site patterns of soil and relief using the extended downscaling approach. Using forward modeling of pollen deposition in each sample site the method seeks that vegetation composition on each site type that produces modeled pollen deposition most similar to empiric pollen deposition. The results (Theuerkauf et al., 2014) indicate that first populations of hazel established soon after the Holocene warming at 11.2 ka. These populations were still small and possibly restricted to warm loving slopes, indicating that low summer warmth was the limiting factor. The widespread expansion of hazel started only after 10.8 ka, possibly following a shift to greater summer warmth. Hazel primarily expanded on sites that are today covered by gleyic soils, from which it largely expelled tree birch. Hazel thus obviously could only expand on sites that received additional wetness from ground- and stagnant water. Giesecke T., Bennett K.D., Birks H.J.B., Bjune A.E., Bozilova E., Feurdean A., Finsinger W., Froyd C., Pokorný P., Rösch M., Seppä H., Tonkov S., Valsecchi V., & Wolters S. (2011) The pace of Holocene vegetation change - testing for synchronous developments. Quaternary Science Reviews, 30, 2805-2814. Huntley B. (1993) Rapid

  2. Not Just the 8.2 event: Dynamic Early Holocene Climate in Arctic Canada

    NASA Astrophysics Data System (ADS)

    Axford, Y.; Briner, J. P.; Miller, G. H.; Francis, D. R.

    2006-12-01

    Temperature reconstructions from a lake in the eastern Canadian Arctic indicate that peak warmth in the early Holocene was interrupted by two abrupt, short-lived temperature reversals at ~9.l and ~8.5 ka. Summer temperatures at Lake CF8, Baffin Island (~500 km west of Greenland) are inferred from subfossil midge (Chironomidae) assemblages. Our results indicate that the site, like others on Baffin Island, experienced exceptionally warm summers (almost 5°C warmer than present) through much of the early Holocene, presumably in response to enhanced summer insolation. After 1000 years of very warm, stable climate, warmth was interrupted by two discrete cold reversals at ~9.1 and ~8.5 ka, during which multiple cold-stenothermous midge taxa appeared in the lake and summer temperatures dropped more than 3°C. These two clearly-defined reversals, well beyond the range of background variability, were of similar amplitude and duration, and were separated by several centuries of near-peak warmth. The only Holocene events of comparable amplitude at this site are the rapid onset of Holocene warmth, and the more gradual Neoglacial cooling after 8 ka. Abrupt cooling events over the Baffin region are consistent with model simulations of the impacts of freshwater outbursts into the Labrador Sea, such as the Lake Agassiz outburst flood that occurred ~8.4 ka. That there are two discrete events recorded at this site indicates that the "8.2 event" was not uniquely significant in this region; rather, the period between approximately ~9.2 and 8 ka was characterized by repeated climate fluctuations forced by multiple outburst floods or other mechanisms. Thus global correlations among paleoclimate records need not assume that climate perturbations during this time period necessarily correlate with the draining of Lake Agassiz or the 8.2 ka cooling in central Greenland.

  3. Early Holocene lake ecosystem development in the southern Baltic lowlands

    NASA Astrophysics Data System (ADS)

    Słowiński, Michał; Ott, Florian; Kramkowski, Mateusz; Noryśkiewicz, Agnieszka M.; Zawiska, Izabela; Dräger, Nadine; Theuerkauf, Martin; Hass, Christoph; Obremska, Milena; Błaszkiewicz, Mirosław; Kordowski, Jarosław; Tjallingii, Rik; Rzodkiewicz, Monika; Schwab, Markus; Brauer, Achim

    2016-04-01

    The first millennia of the Holocene are characterized by gradual and rapid environmental changes following the warming at the beginning of the Holocene superimposed by short-term climatic instability. Landscape evolution during this period occurred at different time scales due to specific response times of landscape compartments like vegetation succession, soil formation and permafrost thawing. As a consequence, a spatiotemporally heterogeneous pattern of changes occurred particularly in regions close to the margins of the continental ice sheets like the Baltic region. Regional atmospheric circulation patterns were affected by cold catabatic winds from the remains of the Fennoscandian ice sheet. The ongoing deglaciation further influenced the regional climate through meltwater release and related changes in the North Atlantic thermohaline circulation. Both effects declined with the progressive ice sheet melt down. Additionally, the land-sea distribution in the North Sea changed drastically during the final melting phase of the glacial ice sheets. The Baltic Sea development is even more complex due to the strong glacio-isostatic adjustments effects that resulted in open and closed water stages affecting the entire Baltic realm. Consequently, the early Holocene interval of sediment records from the southern Baltic lowlands are not considered as straightforward palaeoclimate archives but need to be interpreted in a broader context. We present five partly varved lake records from northern Poland all including an intriguing highly organic-rich interval interrupting biochemical calcite precipitation at about the same time between 10.5 and 10.2 cal kyr BP. These sediment records have been correlated by independent age models based on varve counting, AMS 14C dating, biostratigraphy and tephrochronology. We present multi-proxy records of early Holocene sediments and our preliminary interpretation suggests hydrological processes as the main reason for the intriguing shifts

  4. Early Holocene turnover, followed by stability, in a Caribbean lizard assemblage

    NASA Astrophysics Data System (ADS)

    Kemp, Melissa E.; Hadly, Elizabeth A.

    2016-03-01

    Understanding how communities are impacted by environmental perturbations is integral for addressing the ongoing biodiversity crisis that impacts ecosystems worldwide. The fossil record serves as a window into ancient interactions and the responses of communities to past perturbations. Here, we re-examine paleontological data from Katouche Bay, Anguilla, a Holocene site in the Lesser Antilles. We reveal that the site was more diverse than previously indicated, with long-term, continuous records of three genera of extant lizards (Anolis, Ameiva, and Thecadactylus), and the early Holocene presence of Leiocephalus, a large ground-dwelling lizard that has since been completely extirpated from the Lesser Antilles. The disappearance of Leiocephalus from Katouche Bay resulted in high turnover, decreased evenness, and decreased species richness-a trend that continues to the present day. Our body size reconstructions for the most abundant genus, Anolis, are consistent with the presence of only one species, Anolis cf. gingivinus, at Katouche Bay throughout the Holocene, contrary to previously published studies. Additionally, we find no evidence of dwarfism in A. cf. gingivinus, which contrasts with a global study of contemporary insular lizards. Our data reveal that the impacts of diversity loss on lizard communities are long lasting and irreversible over millennia.

  5. Rapid thinning of Pine Island Glacier in the early Holocene.

    PubMed

    Johnson, J S; Bentley, M J; Smith, J A; Finkel, R C; Rood, D H; Gohl, K; Balco, G; Larter, R D; Schaefer, J M

    2014-02-28

    Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet, has been undergoing rapid thinning and retreat for the past two decades. We demonstrate, using glacial-geological and geochronological data, that Pine Island Glacier (PIG) also experienced rapid thinning during the early Holocene, around 8000 years ago. Cosmogenic (10)Be concentrations in glacially transported rocks show that this thinning was sustained for decades to centuries at an average rate of more than 100 centimeters per year, which is comparable with contemporary thinning rates. The most likely mechanism was a reduction in ice shelf buttressing. Our findings reveal that PIG has experienced rapid thinning at least once in the past and that, once set in motion, rapid ice sheet changes in this region can persist for centuries. PMID:24557837

  6. From Early Holocene to Neoglacial conditions - Multiproxy evidence for stepwise cooling in the Arctic Gateway

    NASA Astrophysics Data System (ADS)

    Werner, K.; Müller, J.; Hass, H.; Spielhagen, R. F.

    2012-12-01

    Two high-resolution sediment sequences from the Western Svalbard margin covering the last ca. 10.000 years were studied in order to derive information on the Holocene variability of heat transport to the Arctic Ocean and fluctuations in the position of the marginal ice zone. The Fram Strait, often referred to as the Arctic Gateway, is the only deep-water passage for Atlantic-derived water masses to enter the Arctic Ocean. Northward advection of relatively warm and saline Atlantic Water masses keeps the eastern Fram Strait ice-free all year and controls the Arctic Ocean's heat budget. We investigated geochemical, micropaleontological, and sedimentological parameters with centennial to multidecadal time resolution at two sites which are located today beneath the Atlantic Water-bearing inner and outer West Spitsbergen Current. Records of planktic and benthic foraminiferal stable isotopes and planktic foraminifer assemblages clearly reveal distinct variations between climatically warmer and colder intervals throughout this period. Strong fluctuations in stable isotope data of the subpolar planktic foraminifer species Turborotalita quinqueloba infer strong variability of summer sea surface conditions probably caused by variable extent of the upper mixed layer and the sea ice margin. Planktic foraminifer fauna imply a stepwise transition from deglacial/Early Holocene to modern-like conditions. Superimposed on the generally strong heat transport to the Arctic Ocean during the Early to Mid-Holocene are repeated short-term coolings such as the 8.2 ka event. Past sea ice conditions were studied by means of the sea ice proxy IP25 and ice rafted detritus and document increasing occurrence of sea ice and/or icebergs since the Mid-Holocene, culminating in the so-called 'neoglaciation' trend. The Late Holocene Neoglacial phase was in particular characterized by the dominance of the cold water-indicating planktic foraminifer species Neogloboquadrina pachyderma. Consistent with the

  7. Rapid responses of the prairie-forest ecotone to early Holocene aridity in mid-continental North America

    NASA Astrophysics Data System (ADS)

    Williams, John W.; Shuman, Bryan; Bartlein, Patrick J.

    2009-04-01

    The prairie-forest transition in midcontinental North America is a major physiognomic boundary, and its shifts during the Holocene are a classic example of climate-driven ecotonal dynamics. Recent work suggests asymmetrical Holocene behavior, with a relatively rapid early Holocene deforestation and more gradual reforestation later in the Holocene. This paper presents a new synthesis of the Holocene history of the Great Plains prairie-forest ecotone in the north-central US and central Canada that updates prior mapping efforts and systematically assesses rates of change. Changes in percent woody cover (%WC) are inferred from fossil pollen records, using the modern analog technique and surface-sediment pollen samples cross-referenced against remotely sensed observations. For contemporary pollen samples from the Great Plains, %WC linearly correlates to percent arboreal pollen (%AP), but regression parameters vary interregionally. At present, %AP is consistently higher than %WC, because of high background levels of arboreal pollen. Holocene maps of the eastern prairie-forest ecotone agree with prior maps, showing a rapid decrease in %WC and eastward prairie advance between 10,000 and 8000 ka (1 ka = 1000 calibrated years before present), a maximum eastward position of the ecotone from 7 to 6 ka, and increased %WC and westward prairie retreat after 6 ka. Ecotone position is ambiguous in Iowa and southeastern Minnesota, due to a scarcity of modern analogs for early-Holocene samples with high Ulmus abundances and for samples from alluvial sediments. The northern prairie-forest ecotone was positioned in central Saskatchewan between 12 and 10 ka, stabilized from 10 to 6 ka despite decreases in %WC at some sites, then moved south after 6 ka. In both east and north, ecotonal movements are consistent with a dry early Holocene and increasing moisture availability after 6 ka. Sites near the ecotone consistently show an asymmetric pattern of abrupt early Holocene deforestation

  8. Foraminiferal stable isotope constraints on salinity changes in the deglacial and early Holocene Baltic Sea region

    NASA Astrophysics Data System (ADS)

    Quintana Krupinski, Nadine; Filipsson, Helena; Bokhari-Friberg, Yasmin; Knudsen, Karen-Luise; Mackensen, Andreas; Groeneveld, Jeroen; Austin, William

    2015-04-01

    The northern European Baltic Sea shows evidence of strong coupling with North Atlantic climate over recent glacial-interglacial cycles, but existing climate proxy evidence from regional sediment records suggest that the coupling may occur through non-linear processes. High-resolution regional climate records in Europe and from the Baltic Sea are critical for evaluating this coupling and the regional sensitivity to North Atlantic and global climate signals. However, evaluating the drivers and mechanisms of proposed links between the North Atlantic and Baltic Sea climate has often been hampered by a lack of long, continuous, high-resolution climate records from this area. New high-resolution sediment cores collected by IODP/ECORD Expedition 347 (Baltic Sea Paleoenvironment) allow such records to be generated, including foraminiferal geochemistry records of Baltic Sea hydrographic conditions during the most recent deglaciation and early Holocene (~19-7 cal. ka). The dramatic changes in salinity, sea level, circulation, temperature, and oxygenation during this period, e.g. through massive meltwater release from proglacial lakes and the early Holocene inundation of the Baltic by seawater highlight these non-linear links between the Baltic and North Atlantic. This work uses benthic foraminiferal stable isotope records (δ18O and δ13C) from sites in the western Baltic (M0059, Lillebælt, early Holocene marine stage (Littorina Sea)) and Kattegat (M0060, Anholt, deglaciation) to constrain salinity changes during these intervals. Because of the dramatic changes in salinity this region experiences today and during the study periods, oxygen isotope records (δ18O) here primarily reflect a signal of changing salinity, with a reduced temperature effect. Early δ18O results from the western Baltic (M0059) show a trend of declining δ18O/salinity during the first several kyr of the Littorina Sea stage, in agreement with previous work indicating declining salinity due to gradual

  9. Century-scale shifts in early holocene atmospheric CO2 concentration

    PubMed

    Wagner; Bohncke; Dilcher; Kurschner; van Geel B; Visscher

    1999-06-18

    The inverse relation between atmospheric carbon dioxide concentration and stomatal frequency in tree leaves provides an accurate method for detecting and quantifying century-scale carbon dioxide fluctuations. Stomatal frequency signatures of fossil birch leaves reflect an abrupt carbon dioxide increase at the beginning of the Holocene. A succeeding carbon dioxide decline matches the Preboreal Oscillation, a 150-year cooling pulse that occurred about 300 years after the onset of the Holocene. In contrast to conventional ice core estimates of 270 to 280 parts per million by volume (ppmv), the stomatal frequency signal suggests that early Holocene carbon dioxide concentrations were well above 300 ppmv. PMID:10373111

  10. Early and Mid-Holocene Climate Variability - A Multi-Proxy Approach from Multi-Millennial Tree Ring Records

    NASA Astrophysics Data System (ADS)

    Ziehmer, Malin Michelle; Nicolussi, Kurt; Schlüchter, Christian; Leuenberger, Markus

    2016-04-01

    Most reconstructions of Holocene climate variability in the Alps are based on low-frequency archives such as glacier and tree line fluctuations. However; recent finds of wood remains in glacier forefields in the Alps reveal a unique high-frequency archive allowing climate reconstruction over the entire Holocene. The evolution of Holocene climate can be reconstructed by using a multi-proxy approach combining tree ring width and multiple stable isotope chronologies by establishing highly resolved stable isotope records from calendar-dated wood which covers the past 9000 years b2k. Therefore, we collected samples in the Alps covering a large SW-NE transect, primarily in glacier forefields but also in peat bogs and small lakes. The multiple sample locations allow the analysis of climatic conditions along a climatic gradient characterized by the change from an Atlantic to a more continental climate. Subsequently, tree ring widths are measured and samples are calendrically dated by means of tree ring analysis. Due to the large amount of samples for stable isotope analysis (> 8000 samples to cover the entire Holocene by guaranteeing a sample replication of 4 samples per time unit of 5 years), dated wood samples are separated into 5-year tree ring blocks. These blocks are sliced and the cellulose is extracted after a standardized procedure and crushed by ultrasonic homogenization. In order to establish multi-proxy records, the stable isotopes of carbon, oxygen and hydrogen are simultaneously measured. Both the 5-year tree ring width and multiple stable isotope series offer new insights into the Early and Mid-Holocene climate and its variability in the Alps. The stable isotope records reveal interesting low-frequency variability. But they also display expected offsets caused by the measurement of individual trees revealing effects of sampling site, tree species and growth trend. These effects offer an additional insight into the tree growth and stand behavior of single

  11. Major hydrological regime change along the semiarid western coast of South America during the early Holocene

    NASA Astrophysics Data System (ADS)

    Ortega, Cristina; Vargas, Gabriel; Rutllant, José A.; Jackson, Donald; Méndez, César

    2012-11-01

    Water availability in the semiarid western coast of Chile (30-32°S) is conditioned by high interannual precipitation variability, reflecting the transition between arid subtropical and moist mid-latitude climates in the Southeastern Pacific Ocean. A paleoclimate reconstruction based on the latest Pleistocene-Holocene geological record from the Quebrada Santa Julia archeological site in Chile (31°50'S) and on modern meteorological mechanisms producing alluvial episodes in this region indicates a major change in the rainfall regime shortly after 8600 cal yr BP. This, together with other paleoclimate proxies along the west coast of South America (34°-14°S), suggests La Niña-like conditions 13,000-8600 cal yr BP. Based on sedimentological and geomorphologic evidence, we hypothesized that the absence of heavy rainfall events in northern Chile and the new hydrological regime that prevailed ca. 8600-5700 cal yr BP in north-central Chile resulted from an increase in the large-scale westerly flow over central Chile, as expected in near-neutral ENSO conditions. This atmospheric circulation anomaly is compatible with an equatorward shift of the influence of the Southeast Pacific Subtropical Anticyclone relative to the early Holocene, prior to the onset of modern ENSO variability.

  12. The Drangajökull ice cap, northwest Iceland, persisted into the early-mid Holocene

    NASA Astrophysics Data System (ADS)

    Schomacker, Anders; Brynjólfsson, Skafti; Andreassen, Julie M.; Gudmundsdóttir, Esther Ruth; Olsen, Jesper; Odgaard, Bent V.; Håkansson, Lena; Ingólfsson, Ólafur; Larsen, Nicolaj K.

    2016-09-01

    Most glaciers and ice caps in Iceland experienced rapid deglaciation in the early Holocene, reaching a minimum extent during the Holocene Thermal Maximum. Here we present evidence of the Holocene glacial history from lake sediment cores retrieved from seven threshold lakes around the Drangajökull ice cap in the Vestfirðir peninsula, NW Iceland. The sediment cores show on/off signals of glacial meltwater activity, as minerogenic material deposited from glacial meltwater alternates with organic-rich material (gyttja) deposited without glacial meltwater. We base the chronology of the sediment cores on 14C ages and geochemical identification of key tephra layers with known ages. A 25-cm thick layer of the Saksunarvatn tephra in Lake Skorarvatn indicates that the northern part of the ice cap had reached a similar size as today or was smaller already by 10.2 cal kyr BP. However, 14C ages of lake sediment cores from the highlands southeast of Drangajökull suggest that this part of the ice cap was larger than today until 7.8-7.2 cal kyr BP. Even today, the Drangajökull ice cap has a different behavior than the main ice caps in Iceland, characterized by a very low glaciation limit. Because palaeoclimatic proxies show an early-mid Holocene temperature optimum in this part of Iceland, we suggest that the persistence of Drangajökull into the early Holocene and, possibly, also the entire Holocene was due to high winter precipitation.

  13. Subsistence strategies in Argentina during the late Pleistocene and early Holocene

    NASA Astrophysics Data System (ADS)

    Martínez, Gustavo; Gutiérrez, María A.; Messineo, Pablo G.; Kaufmann, Cristian A.; Rafuse, Daniel J.

    2016-07-01

    This paper highlights regional and temporal variation in the presence and exploitation of faunal resources from different regions of Argentina during the late Pleistocene and early Holocene. Specifically, the faunal analysis considered here includes the zooarchaeological remains from all sites older than 7500 14C years BP. We include quantitative information for each reported species (genus, family, or order) and we use the number of identified specimens (NISP per taxon and the NISPtotal by sites) as the quantitative measure of taxonomic abundance. The taxonomic richness (Ntaxatotal and Ntaxaexploited) and the taxonomic heterogeneity or Shannon-Wiener index are estimated in order to consider dietary generalization or specialization, and ternary diagrams are used to categorize subsistence patterns of particular sites and regions. The archaeological database is composed of 78 sites which are represented by 110 stratigraphic contexts. Our results demonstrate that although some quantitative differences between regions are observed, artiodactyls (camelids and deer) were the most frequently consumed animal resource in Argentina. Early hunter-gatherers did not follow a specialized predation strategy in megamammals. A variety in subsistence systems, operating in parallel with a strong regional emphasis is shown, according to specific environmental conditions and cultural trajectories.

  14. Holocene vegetation histories from three sites in the Tundra of Northwestern Quebec, Canada

    SciTech Connect

    Gajewski, K. ); Garralla, S.

    1992-11-01

    Two pollen diagrams from lakes north of treeline in northwestern Quebec indicate that Picea never extended north of its present-day limit during the past 6000 yr BP. Alnus crispa was slightly more abundant around 5000 BP, but there are few major changes in the vegetation of the region during the Holocene. A third site in the tundra along Hudson Bay has a slightly longer sequence (7000 yr BP) which indicates more open conditions in the early and recent part of the record. Picea may have been more abundant locally around 3000 BP. Few major changes in these diagrams can be unequivocally attributed to local changes in plant abundance; changes in tree and shrub pollen abundance parallel those seen south of treeline.

  15. Early Late Cretaceous to Holocene seismic stratigraphy and geologic history of southeastern Gulf of Mexico

    SciTech Connect

    Angstadt, D.M.; Austin, J.A.; Buffler, R.T.

    1985-06-01

    Multifold seismic reflection profiles were used in conjunction with results from Deep Sea Drilling Project (DSDP) Leg 77 to interpret the early Late Cretaceous to Holocene geologic history of the southeastern Gulf of Mexico. During the mid-Cenomanian(.) to early Paleocene(.), this region began to record the effects of a collision between a northward-migrating island arc (now part of Cuba) and a salient of the North American plate. More than 2 km (6,560 ft) of gravity-flow deposits accumulated in an elongate structural corridor or foredeep along the base of the modern Cuban slope, while the slope itself was the site of both folding and overthrusting. Clastics continued to dominate the depositional regime until the late Eocene, at which time the Cuban arc had been firmly welded to North America. A late middle to early late Eocene hiatus in Site 540, which coincides with a prominent regional seismic unconformity, marks the transition from predominantly terrigenous input to pelagic/hemipelagic deposition. Since the late Eocene, the southeastern gulf has recorded multiple cycles of deposition and erosion. Unconformities displayed on seismic profiles are numerous. Erosional agents have included the Gulf Stream system, and turbidity currents and debris flows concentrated in the vicinity of submarine canyons. Continuing slope instability is indicated by slide/slump planes along canyon walls.

  16. Early Holocene human remains from the Argentinean Pampas: additional evidence for distinctive cranial morphology of early South Americans.

    PubMed

    Pucciarelli, Héctor M; Perez, S Ivan; Politis, Gustavo G

    2010-10-01

    The cranial morphology of Early Holocene American human samples is characterized by a long and narrow cranial vault, whereas more recent samples exhibit a shorter and wider cranial vault. Two hypotheses have been proposed to account for the morphological differences between early and late-American samples: (a) the migratory hypothesis that suggests that the morphological variation between early and late American samples was the result of a variable number of migratory waves; and (b) the local diversification hypothesis, that is, the morphological differences between early and late American samples were mainly generated by local, random (genetic drift), and nonrandom factors (selection and phenotypic plasticity). We present the first craniometric study of three early skulls from the Argentinean Pampas, dated ∼8,000 cal. years BP (Arroyo Seco 2, Chocorí, and La Tigra), and one associated with mega-faunal remains (Fontezuelas skull). In addition, we studied several Late Holocene samples. We show that the skulls from the Argentinean Pampas are morphologically similar to other Early Holocene American skulls (i.e., Lagoa Santa from Brazil, Tequendama, Checua, and Aguazuque from Colombia, Lauricocha from Peru, and early Mexicans) that exhibit long and narrow cranial vaults. These samples differ from the Late Holocene American samples that exhibit a shorter and wider cranial vault. Our results underscore the important differences in cranial morphology between early and late-American samples. However, we emphasize the need for further studies to discuss alternative hypotheses regarding such differences. PMID:20623674

  17. Oceanic and atmospheric forcing of early Holocene ice shelf retreat, George VI Ice Shelf, Antarctica Peninsula

    NASA Astrophysics Data System (ADS)

    Smith, James A.; Bentley, Michael J.; Hodgson, Dominic A.; Roberts, Stephen J.; Leng, Melanie J.; Lloyd, Jeremy M.; Barrett, Melissa S.; Bryant, Charlotte; Sugden, David E.

    2007-02-01

    We use lake sediment records from an epishelf lake on Alexander Island to provide a detailed picture of the Holocene history of George VI Ice Shelf (GVI-IS). Core analyses included; micropaleontology (diatoms/foraminifera), stable isotope (δ18O, δ13C), geochemistry (total organic carbon (TOC), total nitrogen (TN), C/N ratios) and grain-size analyses. These data provide robust evidence for one period of past ice shelf absence during the early Holocene. The timing of this period has been constrained by 10 AMS 14C dates performed on mono-specific foraminifera samples. These dates suggest that GVI-IS was absent between c 9600 cal yr BP and c 7730 cal yr BP. This early Holocene collapse immediately followed a period of maximum Holocene warmth that is recorded in some Antarctic ice cores and coincides with an influx of warmer ocean water onto the western Antarctic Peninsula (AP) shelf at c 9000 cal yr BP. The absence of a currently extant ice shelf during this time interval suggests that early Holocene ocean-atmosphere variability in the AP was greater than that measured in recent decades.

  18. Solar forcing of Florida Straits surface salinity during the early Holocene

    NASA Astrophysics Data System (ADS)

    Schmidt, Matthew W.; Weinlein, William A.; Marcantonio, Franco; Lynch-Stieglitz, Jean

    2012-09-01

    Previous studies showed that sea surface salinity (SSS) in the Florida Straits as well as Florida Current transport covaried with changes in North Atlantic climate over the past two millennia. However, little is known about earlier Holocene hydrographic variability in the Florida Straits. Here, we combine Mg/Ca-paleothermometry and stable oxygen isotope measurements on the planktonic foraminifera Globigerinoides ruber (white variety) from Florida Straits sediment core KNR166-2 JPC 51 (24° 24.70' N, 83° 13.14' W, 198 m deep) to reconstruct a high-resolution (˜25 yr/sample) early to mid Holocene record of sea surface temperature and δ18OSW (a proxy for SSS) variability. After removing the influence of global δ18OSW change due to continental ice volume variability, we find that early Holocene SSS enrichments are associated with increased evaporation/precipitation ratios in the Florida Straits during periods of reduced solar forcing, increased ice rafted debris in the North Atlantic and the development of more permanent El Niño-like conditions in the eastern equatorial Pacific. When considered with previous high-resolution reconstructions of Holocene tropical atmospheric circulation changes, our results provide evidence that variations in solar forcing over the early Holocene had a significant impact on the global tropical hydrologic cycle.

  19. On the occurrence of annual layers in Dome Fuji ice core early Holocene ice

    NASA Astrophysics Data System (ADS)

    Svensson, A.; Fujita, S.; Bigler, M.; Braun, M.; Dallmayr, R.; Gkinis, V.; Goto-Azuma, K.; Hirabayashi, M.; Kawamura, K.; Kipfstuhl, S.; Kjær, H. A.; Popp, T.; Simonsen, M.; Steffensen, J. P.; Vallelonga, P.; Vinther, B. M.

    2015-09-01

    Whereas ice cores from high-accumulation sites in coastal Antarctica clearly demonstrate annual layering, it is debated whether a seasonal signal is also preserved in ice cores from lower-accumulation sites further inland and particularly on the East Antarctic Plateau. In this study, we examine 5 m of early Holocene ice from the Dome Fuji (DF) ice core at a high temporal resolution by continuous flow analysis. The ice was continuously analysed for concentrations of dust, sodium, ammonium, liquid conductivity, and water isotopic composition. Furthermore, a dielectric profiling was performed on the solid ice. In most of the analysed ice, the multi-parameter impurity data set appears to resolve the seasonal variability although the identification of annual layers is not always unambiguous. The study thus provides information on the snow accumulation process in central East Antarctica. A layer counting based on the same principles as those previously applied to the NGRIP (North Greenland Ice core Project) and the Antarctic EPICA (European Project for Ice Coring in Antarctica) Dronning Maud Land (EDML) ice cores leads to a mean annual layer thickness for the DF ice of 3.0 ± 0.3 cm that compares well to existing estimates. The measured DF section is linked to the EDML ice core through a characteristic pattern of three significant acidity peaks that are present in both cores. The corresponding section of the EDML ice core has recently been dated by annual layer counting and the number of years identified independently in the two cores agree within error estimates. We therefore conclude that, to first order, the annual signal is preserved in this section of the DF core. This case study demonstrates the feasibility of determining annually deposited strata on the central East Antarctic Plateau. It also opens the possibility of resolving annual layers in the Eemian section of Antarctic ice cores where the accumulation is estimated to have been greater than in the Holocene.

  20. Dynamical response of the tropical Pacific Ocean to solar forcing during the early Holocene.

    PubMed

    Marchitto, Thomas M; Muscheler, Raimund; Ortiz, Joseph D; Carriquiry, Jose D; van Geen, Alexander

    2010-12-01

    We present a high-resolution magnesium/calcium proxy record of Holocene sea surface temperature (SST) from off the west coast of Baja California Sur, Mexico, a region where interannual SST variability is dominated today by the influence of the El Niño-Southern Oscillation (ENSO). Temperatures were lowest during the early to middle Holocene, consistent with documented eastern equatorial Pacific cooling and numerical model simulations of orbital forcing into a La Niña-like state at that time. The early Holocene SSTs were also characterized by millennial-scale fluctuations that correlate with cosmogenic nuclide proxies of solar variability, with inferred solar minima corresponding to El Niño-like (warm) conditions, in apparent agreement with the theoretical "ocean dynamical thermostat" response of ENSO to exogenous radiative forcing. PMID:21127251

  1. Dynamical Response of the Tropical Pacific Ocean to Solar Forcing During the Early Holocene

    NASA Astrophysics Data System (ADS)

    Marchitto, Thomas M.; Muscheler, Raimund; Ortiz, Joseph D.; Carriquiry, Jose D.; van Geen, Alexander

    2010-12-01

    We present a high-resolution magnesium/calcium proxy record of Holocene sea surface temperature (SST) from off the west coast of Baja California Sur, Mexico, a region where interannual SST variability is dominated today by the influence of the El Niño-Southern Oscillation (ENSO). Temperatures were lowest during the early to middle Holocene, consistent with documented eastern equatorial Pacific cooling and numerical model simulations of orbital forcing into a La Niña-like state at that time. The early Holocene SSTs were also characterized by millennial-scale fluctuations that correlate with cosmogenic nuclide proxies of solar variability, with inferred solar minima corresponding to El Niño-like (warm) conditions, in apparent agreement with the theoretical “ocean dynamical thermostat” response of ENSO to exogenous radiative forcing.

  2. Late Pleistocene-early Holocene karst features, Laguna Madre, south Texas: A record of climate change

    SciTech Connect

    Prouty, J.S.

    1996-09-01

    A Pleistocene coquina bordering Laguna Madre, south Texas, contains well-developed late Pleistocene-early Holocene karst features (solution pipes and caliche crusts) unknown elsewhere from coastal Texas. The coquina accumulated in a localized zone of converging longshore Gulf currents along a Gulf beach. The crusts yield {sup 14}C dates of 16,660 to 7630 B.P., with dates of individual crust horizons becoming younger upwards. The karst features provide evidence of regional late Pleistocene-early Holocene climate changes. Following the latest Wisconsinan lowstand 18,000 B.P. the regional climate was more humid and promoted karst weathering. Partial dissolution and reprecipitation of the coquina formed initial caliche crust horizons; the crust later thickened through accretion of additional carbonate laminae. With the commencement of the Holocene approximately 11,000 B.P. the regional climate became more arid. This inhibited karstification of the coquina, and caliche crust formation finally ceased about 7000 B.P.

  3. Mid-depth ventilation of western North Atlantic during Younger Dryas and Early Holocene

    NASA Astrophysics Data System (ADS)

    Zhao, N.; Keigwin, L. D.

    2012-12-01

    We investigated the mid-depth ventilation of western North Atlantic during Younger Dryas (YD) and Early Holocene. The method we use to get the ventilation age is radiocarbon dating planktonic and benthic foraminifera (PF and BF) pairs in the same sample. Combining our new data (New England Slope, within the depth range 1500-1900 m) and data from Blake & Bahama Outer Ridge (BBOR, Keigwin 2004), we show that there was a front between mid-depth and deep ocean during YD, generally between 2 and 2.5 km. Ventilation of mid-depth water (<=500 years) was much better than deep water (>900 years). Separating the data into three periods (12.4-12.5 ka, 12.7-12.8 ka, and 13.0-13.1 ka), we find the Meridional Overturning Circulation (MOC) became more sluggish within YD for both mid-depth and deep water. Extending our observations into the Early Holocene, we noticed that the mid-depth ventilation age recorded by NE Slope cores increased significantly from about 450 years at 12.4 ka to about 2150 years at 9.6 ka. This suggests that deep water ventilation increased after YD, which leads to the replacement of Glacial NAIW by NADW. Since the slope of the ventilation age vs. calendar age curve is close to -1, this indicates that there may have been very little renewal of mid-depth water along NE Slope during Early Holocene. However, the ventilation age of mid-depth water at BBOR did not have an obvious change from YD to Early Holocene. This possibly means that different parts of mid-depth western North Atlantic were ventilated differently during Early Holocene.

  4. Lateglacial and early Holocene climates of the Atlantic margins of Europe: Stable isotope, mollusc and pollen records from Orkney, Scotland

    NASA Astrophysics Data System (ADS)

    Whittington, Graeme; Edwards, Kevin J.; Zanchetta, Giovanni; Keen, David H.; Bunting, M. Jane; Fallick, Anthony E.; Bryant, Charlotte L.

    2015-08-01

    The margins of mainland Europe, and especially those areas coming under the influence of North Atlantic weather systems, are ideally placed to record changing palaeoclimates. Cores from an infilled lake basin at Crudale Meadow in Mainland, Orkney, revealed basal deposits of calcareous mud ('marl') beneath sedge peat. Stable isotope, palynological and molluscan analyses allowed the establishment of palaeoenvironmental changes through the Devensian Lateglacial and the early Holocene. The δ18Omarl record exhibited the existence of possibly four climatic oscillations in the Lateglacial (one of which, within event cf. GI-1c, is not often commented upon), as well as the Preboreal Oscillation and other Holocene perturbations. The cold episodes succeeding the Preboreal Oscillation were demarcated conservatively and one of these (event C5, ∼11.0 ka) may have previously been unremarked, while the putative 9.3 and 8.2 ka events seem not to produce corresponding palynologically visible floristic changes. The events at Crudale Meadow are consistent with those recorded at other sites from Britain, Ireland and elsewhere, and can be correlated with isotopic changes shown by the Greenland ice cores. The multi-proxy approach enriches the environmental reconstructions from the site, although the synchronicity of the response of the various proxies is sometimes equivocal, depending upon the time period concerned, taphonomy, and the nature of the deposits. The site may contain the most northerly Lateglacial isotope record from northwest Europe, and it has yielded one of the best archives for the demonstration of abrupt early Holocene events within Britain.

  5. Early to Mid-Holocene climate variability from multi-millennial tree ring isotope records

    NASA Astrophysics Data System (ADS)

    Ziehmer, Malin Michelle; Nicolussi, Kurt; Schlüchter, Christian; Leuenberger, Markus

    2015-04-01

    The evolution of Holocene climate and its variability in the Alps has been principally investigated by analyzing low-frequency archives. The environment of the Alps is known to react sensitively to changes in environmental conditions such as variations of precipitation and temperature, which can be observed in the current retreat of glaciers as a result of global warming in the course of global climate change. The mentioned low- frequency records such as glacier and tree line fluctuations reveal an evolution of Holocene climate from a generally warm Early and Mid to a relatively cool Late Holocene, whereas the rare high resolution records often do not indicate such a general long-term trend. The causes and mechanisms behind are not fully understood yet. Recent finds of wood remains of long-lived trees in Alpine glacier forefields changed the concept of Holocene glacier variability and therefore, the present understanding of Holocene climate dynamics as they prove that glaciers in the Alps were usually relatively small and short in their extension during the Early and Mid-Holocene (Joerin et al., 2008; Nicolussi, Schlüchter, 2012). Those findings of wood remains further prove that the natural variability of postglacial climate is still not sufficiently known. However; such knowledge is essential for climate model input and the ability to disentangle natural from anthropogenic influences on the Earth's climate. The aim of our study is to establish highly resolved isotope records from calendar-dated wood remains covering the past 9000 years. Samples are collected in glacier forefields in the Alps, thereby covering a large SW- NE transect. Wood samples are separated into 5-year tree ring blocks from which cellulose is extracted and is crushed by ultrasonic homogenization (Boettger et al., 2007; Laumer et al., 2009). As the amount of samples (>7000 samples to cover the whole Holocene) is immense, the improved preparation procedure shortens the time for each single

  6. Centennial to millennial variations of atmospheric methane during the early Holocene

    NASA Astrophysics Data System (ADS)

    Yang, Ji-Woong; Ahn, Jinho; Brook, Edward

    2015-04-01

    Atmospheric CH4 is one of the most important greenhouse gases. Ice core studies revealed strong correlations between millennial CH4 variations and Greenland climate during the last glacial period. However, millennial to sub-millennial CH4 variations during interglacial periods are not well studied. Recently, several high-resolution data sets have been produced for the late Holocene, but it is difficult to distinguish natural- from anthropogenic changes. In contrast, the methane budget of the early Holocene is not affected by anthropogenic disturbances, thus may help us better understand natural CH4 control mechanisms under interglacial climate boundary conditions. Here we present our new high-precision and high-resolution atmospheric CH4 record from Siple Dome ice core, Antarctica that covers the early Holocene. We used our new wet extraction system at Seoul National University that shows a good precision of ~1 ppb. Our data show several tens of ppb of centennial- to millennial CH4 variations and an anti-correlative evolution with Greenland climate on the millennial time scale. The CH4 record could have been affected by many different types of forcing, including temperature, precipitation (monsoon intensity), biomass burning, sea surface temperature, and solar activity. According to our data, early Holocene CH4 is well correlated with records of hematite stained grains (HSG) in North Atlantic sediment records, within age uncertainties. A red-noise spectral analysis yields peaks at frequencies of ~1270 and ~80 years, which are similar to solar frequencies, but further investigations are needed to determine major controlling factor of atmospheric CH4during the early Holocene.

  7. The cultural and chronological context of early Holocene maize and squash domestication in the Central Balsas River Valley, Mexico

    PubMed Central

    Ranere, Anthony J.; Piperno, Dolores R.; Holst, Irene; Dickau, Ruth; Iriarte, José

    2009-01-01

    Molecular evidence indicates that the wild ancestor of maize is presently native to the seasonally dry tropical forest of the Central Balsas watershed in southwestern Mexico. We report here on archaeological investigations in a region of the Central Balsas located near the Iguala Valley in Guerrero state that show for the first time a long sequence of human occupation and plant exploitation reaching back to the early Holocene. One of the sites excavated, the Xihuatoxtla Shelter, contains well-stratified deposits and a stone tool assemblage of bifacially flaked points, simple flake tools, and numerous handstones and milling stone bases radiocarbon dated to at least 8700 calendrical years B.P. As reported in a companion paper (Piperno DR, et al., in this issue of PNAS), starch grain and phytolith residues from the ground and chipped stone tools, plus phytoliths from directly associated sediments, provide evidence for maize (Zea mays L.) and domesticated squash (Cucurbita spp.) in contexts contemporaneous with and stratigraphically below the 8700 calendrical years B.P. date. The radiocarbon determinations, stratigraphic integrity of Xihuatoxtla's deposits, and characteristics of the stone tool assemblages associated with the maize and squash remains all indicate that these plants were early Holocene domesticates. Early agriculture in this region of Mexico appears to have involved small groups of cultivators who were shifting their settlements seasonally and engaging in a variety of subsistence pursuits. PMID:19307573

  8. The cultural and chronological context of early Holocene maize and squash domestication in the Central Balsas River Valley, Mexico.

    PubMed

    Ranere, Anthony J; Piperno, Dolores R; Holst, Irene; Dickau, Ruth; Iriarte, José

    2009-03-31

    Molecular evidence indicates that the wild ancestor of maize is presently native to the seasonally dry tropical forest of the Central Balsas watershed in southwestern Mexico. We report here on archaeological investigations in a region of the Central Balsas located near the Iguala Valley in Guerrero state that show for the first time a long sequence of human occupation and plant exploitation reaching back to the early Holocene. One of the sites excavated, the Xihuatoxtla Shelter, contains well-stratified deposits and a stone tool assemblage of bifacially flaked points, simple flake tools, and numerous handstones and milling stone bases radiocarbon dated to at least 8700 calendrical years B.P. As reported in a companion paper (Piperno DR, et al., in this issue of PNAS), starch grain and phytolith residues from the ground and chipped stone tools, plus phytoliths from directly associated sediments, provide evidence for maize (Zea mays L.) and domesticated squash (Cucurbita spp.) in contexts contemporaneous with and stratigraphically below the 8700 calendrical years B.P. date. The radiocarbon determinations, stratigraphic integrity of Xihuatoxtla's deposits, and characteristics of the stone tool assemblages associated with the maize and squash remains all indicate that these plants were early Holocene domesticates. Early agriculture in this region of Mexico appears to have involved small groups of cultivators who were shifting their settlements seasonally and engaging in a variety of subsistence pursuits. PMID:19307573

  9. Late-Glacial to Early Holocene Climate Changes from a Central Appalachians Pollen and Macrofossil Record

    NASA Technical Reports Server (NTRS)

    Kneller, Margaret; Peteet, Dorothy

    1997-01-01

    A Late-glacial to early Holocene record of pollen, plant macrofossils and charcoal, based on two cores, is presented for Browns Pond in the central Appalachians of Virginia. An AMS radiocarbon chronology defines the timing of moist and cold excursions, superimposed upon the overall warming trend from 14,200 to 7,500 C-14 yr B.P. This site shows cold, moist conditions from approximately 14,200 to 12,700 C-14 yr B.P., with warming at 12,730, 11,280 and 10,050 C-14 yr B.P. A decrease in deciduous broad-leaved tree taxa and Pinus strobus (haploxylon) pollen, simultaneous with a re-expansion of Abies denotes a brief, cold reversal from 12,260 to 12,200 C-14 yr B.P. A second cold reversal, inferred from increases in montane conifers, is centered at 7,500 C-14 yr B.P. The cold reversals at Browns Pond may be synchronous with climate change in Greenland, and northwestern Europe. Warming at 11,280 C-14 yr B.P. shows the complexity of regional climate responses during the Younger Dryas chronozone.

  10. Vegetation changes during the last deglacial and early Holocene: a record from Little Salt Spring Florida

    NASA Astrophysics Data System (ADS)

    Bernhardt, C. E.; Willard, D. A.; Landacre, B.; Gifford, J.

    2010-12-01

    We present a high-resolution, 7000 year long pollen record of vegetation change that spans the Younger Dryas and Early Holocene. An 8.2 m sediment core was collected from Little Salt Spring (LSS), FL, which is an hourglass-shaped karst sinkhole lake with a water depth of 72 m. Previous paleohydrological reconstructions based on carbon and oxygen isotopes indicate that LSS is sensitive to past deglacial climate and sea-level changes. Distinct changes in pollen assemblages from the LSS core correspond to well-documented climatic events. For example, cooler climate during the Younger Dryas is characterized by an abrupt increase in Carya pollen. This change in pollen assemblages corresponds to estimates of cooler temperatures from ostracode isotopic records from LSS. In addition, precipitation and temperature in the early Holocene is relatively invariate as reflected in the development of a comparatively stable bayhead hammock plant community. In general, the vegetation response at LSS indicates an abrupt onset of a cooler Younger Dryas followed by, based ostracode isotopic records, a warmer and a relatively stable Early Holocene. The LSS record has potential to examine human response to abrupt climate variability because recent archeological finds indicate Early Native Americans were present there at least 10,000 years ago.

  11. Coevolution of farming and private property during the early Holocene.

    PubMed

    Bowles, Samuel; Choi, Jung-Kyoo

    2013-05-28

    The advent of farming around 12 millennia ago was a cultural as well as technological revolution, requiring a new system of property rights. Among mobile hunter-gatherers during the late Pleistocene, food was almost certainly widely shared as it was acquired. If a harvested crop or the meat of a domesticated animal were to have been distributed to other group members, a late Pleistocene would-be farmer would have had little incentive to engage in the required investments in clearing, cultivation, animal tending, and storage. However, the new property rights that farming required--secure individual claims to the products of one's labor--were infeasible because most of the mobile and dispersed resources of a forager economy could not cost-effectively be delimited and defended. The resulting chicken-and-egg puzzle might be resolved if farming had been much more productive than foraging, but initially it was not. Our model and simulations explain how, despite being an unlikely event, farming and a new system of farming-friendly property rights nonetheless jointly emerged when they did. This Holocene revolution was not sparked by a superior technology. It occurred because possession of the wealth of farmers--crops, dwellings, and animals--could be unambiguously demarcated and defended. This facilitated the spread of new property rights that were advantageous to the groups adopting them. Our results thus challenge unicausal models of historical dynamics driven by advances in technology, population pressure, or other exogenous changes. Our approach may be applied to other technological and institutional revolutions such as the 18th- and 19th-century industrial revolution and the information revolution today. PMID:23671111

  12. Coevolution of farming and private property during the early Holocene

    PubMed Central

    Bowles, Samuel; Choi, Jung-Kyoo

    2013-01-01

    The advent of farming around 12 millennia ago was a cultural as well as technological revolution, requiring a new system of property rights. Among mobile hunter–gatherers during the late Pleistocene, food was almost certainly widely shared as it was acquired. If a harvested crop or the meat of a domesticated animal were to have been distributed to other group members, a late Pleistocene would-be farmer would have had little incentive to engage in the required investments in clearing, cultivation, animal tending, and storage. However, the new property rights that farming required—secure individual claims to the products of one’s labor—were infeasible because most of the mobile and dispersed resources of a forager economy could not cost-effectively be delimited and defended. The resulting chicken-and-egg puzzle might be resolved if farming had been much more productive than foraging, but initially it was not. Our model and simulations explain how, despite being an unlikely event, farming and a new system of farming-friendly property rights nonetheless jointly emerged when they did. This Holocene revolution was not sparked by a superior technology. It occurred because possession of the wealth of farmers—crops, dwellings, and animals—could be unambiguously demarcated and defended. This facilitated the spread of new property rights that were advantageous to the groups adopting them. Our results thus challenge unicausal models of historical dynamics driven by advances in technology, population pressure, or other exogenous changes. Our approach may be applied to other technological and institutional revolutions such as the 18th- and 19th-century industrial revolution and the information revolution today. PMID:23671111

  13. Early Holocene basinal sediments of the Dakhleh Oasis region, south central Egypt

    NASA Astrophysics Data System (ADS)

    Brookes, Ian A.

    1989-09-01

    Twenty samples of artifactual ostrich eggshell and hearth charcoal, firmly to loosely associated with basinal lacustrine, playa, and sand sheet sediments in the Dakhleh Oasis region of south-central Egypt, yield radiocarbon ages between ca. 8800 and ca. 4700 yr B.P. The sediments record variable sedimentary responses to an early Holocene pluvial interval in this virtually rainless region. Differences of hydrogeology and morphometry among and within basin types complicate paleoclimatic interpretation.

  14. On the influence of land cover on early Holocene climate in northern latitudes

    NASA Astrophysics Data System (ADS)

    Rivers, Aaron R.; Lynch, Amanda H.

    2004-11-01

    This study presents a factorial experimental strategy for assessing the effects of the changing land surface on early Holocene (˜11 ka) climate in Beringia. The strategy uses a coupled land-atmosphere single column model in a series of perturbation experiments that vary the vegetation type, lake cover, and soil specification simultaneously. Two sites and eight years of model forcing are chosen to determine the importance of differing terrestrial histories, local climate, and interannual variability. Eastern Beringia is represented by Fairbanks, Alaska, and western Beringia is represented by Elikchan Lake, Siberia. Evaluations of model response are performed using metrics important for vegetation growth, such as growing degree days and moisture availability. For both sites, large-scale interannual variability has a greater impact on the local climate than changes in the land surface specification for temperature-based responses, but not for moisture availability. Of the three land surface parameters tested, vegetation type is most influential. Vegetation transitions from tundra to boreal forest leads to increased precipitation, winter snow depth, and low cloud, leading to a delayed snowmelt in forested regions. This is in contrast to expectations based on albedo arguments alone. In western Beringia, a positive feedback is suggested in warming due to the presence of boreal forest, consistent with some observations that Siberian deciduous forest persisted longer than Alaskan deciduous forest in the context of large-scale cooling of the climate. The reverse was found to be true in eastern Beringia, where deciduous forests exhibited a cooling effect due to increases in albedo. The response to soil variations was relatively small, but the inclusion of inland lakes tends in general to cool the surface, although in some years a warming is evident due to the surface energy balance shifting in favor of downwelling longwave heating over evaporative cooling.

  15. Stable-Isotope Perspectives on Holocene Environmental Change at Archaeological Sites in the Middle Tanana Valley, Interior Alaska

    NASA Astrophysics Data System (ADS)

    Johnson, W. C.; Gaines, E. P.

    2010-12-01

    Summer of 2009, Colorado State University Center for Environmental Management of Military Lands conducted test excavations of 29 prehistoric archaeological sites situated on a loess-mantled morainal ridge complex within the Jarvis Creek valley of the Tanana River system at Fort Wainwright in Interior Alaska. Initial loess deposition on the moraines began about 13,000 cal yr BP, with subsequent long-term, nomadic occupation of the area occurring from 9,500 to 1,060 cal yr BP. An array of data were extracted from bulk-sediment samples and used to assess past environmental conditions. Parameters and approaches used to generate these data included stable carbon isotope ratios, magnetic susceptibility, biogenic opal analysis, detrital charcoal content, quantitative color (L*a*b), and particle-size distribution. Stable carbon isotope trends, in combination with the other environmental proxy data, document major environmental changes. Data from the glacial till-loess transition and lower silt mantle indicate that the area was cold and slightly mesic, and dominated by treeless C3-dominated grassland immediately after the terminal Pleistocene glacial retreat (~12,700 cal yr BP). A dearth of particulate charcoal and charred phytoliths from sediments of this period suggests a minor role for fire, e.g., only localized, small fires. Cold, treeless environmental conditions continued throughout the Early Holocene (~12,000-7,000 cal yr BP), though it was more mesic than earlier. Middle Holocene (~7000-5000 cal yr BP) data display a shift in C3 grass species (increased δ13C values), the appearance of a shrub component to the plant community, significant surface stability, and more widespread fire occurrence. Picea glauca (white spruce) and Alnus sp. (alder) appear in the later parts of the Middle Holocene, and charcoal concentration increases. The Late Holocene (since ~5,000 cal yr BP) witnessed a decline in P. glauca by about 50%, a tenfold increase in Alnus, and the appearance

  16. Reconstruction of early Holocene paleoclimate and environment in the SW Kola region, Russian Arctic

    NASA Astrophysics Data System (ADS)

    Grekov, Ivan; Kolka, Vasiliy; Syrykh, Liudmila; Nazarova, Larisa

    2016-04-01

    In the current period of the global climate change it becomes necessary to have a clear understanding of not only the changes taking place in the components of the natural environment, but also to understand development of all interactions between those components. Quaternary terrigenic sediments and lakes of the Kola Peninsula store information about the development of the region in the Late Glacial and Holocene: movements of the glacier, neotectonic activity, post-glacial rebound, formation and development of natural environments after deglaciation. Multi-proxy study of landscapes evolution of the Kola Peninsula in the Late Quaternary will help to establish a detailed reconstruction of climatic and environmental changes of this poor studied sector of the Arctic. Quaternary history on the Kola Peninsula is represented mainly by Late Pleistocene and Holocene sediments covering the Baltic Shield (Lavrova, 1960; Evzerov, 2015). Several palaeolimnological investigations in the Baltic Shield area have been performed earlier (Donner et al., 1977; Anundsen, 1985; Berglund, 2004). Studies of the southern coast of the Kola Peninsula have shown that marine transgression took place in the Late Pleistocene that was then replaced by a regression with variable speed. The slowdown of the uplift of the area took place between 8800 - 6800 BP (cal. years) and corresponded to the time of the Tapes transgression of the Arctic Ocean (Evzerov et al. 2010; Kolka, et al., 2013). Palaeoclimatic studies based on micro-paleontological analyzes indicate uneven development of the Kola Peninsula landscapes in the Late Glacial and Early Holocene. The northern coast of the Peninsula became free of ice first. In this area tundra-steppe vegetation was established for a short time and was later replaced by tundra (Snyder et al, 2000). Southern part of the Kola Peninsula was dependent on the conditions of deglaciation of the White Sea basin and cleared of ice much later (Evzerov et al., 2010; Kolka

  17. Late Wisconsin and Early Holocene runoff through the upper Ohio River basin

    SciTech Connect

    Kite, J.S. . Dept. of Geology and Geography)

    1992-01-01

    A tentative absolute chronology is emerging from radiocarbon dates on glacial, alluvial and colluvial sediments in the upper Ohio River basin. Radiocarbon dates for Gallipolis Lock and Dam indicate the river eroded down to its present bedrock floor before 22,400 yr B.P. Data from several sites indicate aggradation began soon after 22,400 yr B.P., coincident with, or just before, a glacier advance into the upper Ohio basin. Sand and gravel aggraded in glaciated tributaries and the main valley, whereas silt, fine sand, and clay accumulated in unglaciated tributaries. Slope instability and colluvial deposition were extensive at this time. Aggradation continued until 25 to 40 m of sediments filled the Ohio River Valley. The paucity of radiocarbon dates prohibits precise determination of when peak aggradation occurred and how that peak related to glacial and climatic events. Although the Laurentide Ice Sheet retreated out of the basin by about 14,000 yr B.P., the river remained braided until at least 13,000 yr B.P., possibly because of slope instability in a cold late Wisconsin climate or the time required for the river to adjust to reduced outwash sediment supply. Coarse late-glacial channel deposits may reflect increased flood discharges after 13,000 B.P. and onset of the transition from a braided system to a meandering channel. However, the upper Ohio River seems not to have taken on its modern morphology until the early Holocene. Most dated overbank deposits on tributaries are younger than 10,000 yr B.P.; most on the Ohio River are younger than 8,500 yr B.P.

  18. Brief communication: DNA from early Holocene American dog.

    PubMed

    Tito, Raul Y; Belknap, Samuel L; Sobolik, Kristin D; Ingraham, Robert C; Cleeland, Lauren M; Lewis, Cecil M

    2011-08-01

    We present the oldest genetically identified dog in the Americas, directly dated to 9,260 ± 170 Cal. B.P. The DNA was extracted from an occipital condyle imbedded in a human paleofecal sample from Hinds Cave in southwest Texas. A 368 base pair fragment of the mitochondrial genome control region was sequenced. These data were analyzed with comparable data, which included other ancient dogs and extant dogs, wolves and coyotes from around the world. Compiled with published data, our results characterize ancient American dogs within clades rooted by Eurasian wolves. In the Americas, these data provide no evidence of local interbreeding with wolves. This is a departure from the genetic pattern in other areas of the world where interbreeding with local wolf populations is apparent. Our discovery of domestic dog bone in a human paleofecal sample provides the earliest direct evidence for human consumption of dogs in the New World. These data support the hypothesis that dogs were a food source for early Paleoamericans. PMID:21541929

  19. Climate Change in Lowland Central America During the Late Deglacial and Early Holocene

    SciTech Connect

    Hillesheim, M B; Hodell, D A; Leyden, B W; Brenner, M; Curtis, J H; Anselmetti, F S; Ariztegui, D; Buck, D G; Guilderson, T P; Rosenmeier, M F; Schnurrenberger, D W

    2005-02-08

    The transition from arid glacial to moist early Holocene conditions represented a profound change in northern lowland Neotropical climate. Here we report a detailed record of changes in moisture availability during the latter part of this transition ({approx}11,250 to 7,500 cal yr BP) inferred from sediment cores retrieved in Lake Peten Itza, northern Guatemala. Pollen assemblages demonstrate that a mesic forest had been largely established by {approx}11,250 cal yr BP, but sediment properties indicate that lake level was more than 35 m below modern stage. From 11,250 to 10,350 cal yr BP, during the Preboreal period, lithologic changes in sediments from deep-water cores (>50 m below modern water level) indicate several wet-dry cycles that suggest distinct changes in effective moisture. Four dry events (designated PBE1-4) occurred at 11,200, 10,900, 10,700, and 10,400 cal yr BP and correlate with similar variability observed in the Cariaco Basin titanium record and glacial meltwater pulses into the Gulf of Mexico. After 10,350 cal yr BP, multiple sediment proxies suggest a shift to a more persistently moist early Holocene climate. Comparison of results from Lake Peten Itza with other records from the circum-Caribbean demonstrates a coherent climate response during the entire span of our record. Furthermore, lowland Neotropical climate during the late deglacial and early Holocene period appears to be tightly linked to climate change in the high-latitude North Atlantic. We speculate that the observed changes in lowland Neotropical precipitation were related to the intensity of the annual cycle and associated displacements in the mean latitudinal position of the Intertropical Convergence Zone and Azores-Bermuda high-pressure system. This mechanism operated on millennial-to-submillennial timescales and may have responded to changes in solar radiation, glacial meltwater, North Atlantic sea ice, and the Atlantic meridional overturning circulation (MOC).

  20. Early Holocene Sediment Discharge from Taiwanese Rivers: Intensified Asian Monsoon and Climate Change

    NASA Astrophysics Data System (ADS)

    Hsu, Ho-Han; Liu, Char-Shine; Milliman, John; Chen, Tzu-Ting; Chang, Jih-Hsin; Wang, Yunshuen

    2016-04-01

    Temporal variations of fluvial sediment discharge can reflect the significant climatic variation. In this study, high-resolution sedimentary records - on the millennial scale - from onshore wells, offshore cores and seismic profiles are used to quantify sediment discharge from small mountainous rivers around Taiwan since the last glacial maximum. While significantly high sediment accumulation rates have been observed in the modern flood plain, shelf and deep-sea basins during the late Pleistocene and Holocene, early Holocene rates are unusually high. In northeast Taiwan, for example, sediment flux from the Lanyang River between 10-12 ka BP appears to have been 10 mt/yr, about 4 fold greater than measured annual discharge prior to 1960. In the southwest Taiwan, the highest sedimentation rate happened during 10-12 ka BP. Long-term average discharge since 8 ka BP has been ~12 mt/yr), less than half the 29 mt/yr that was deposited on the Kaohsiung-Pingtung Plain. These and other sedimentation histories around Taiwan as well as in the South China Sea and the Bay of Bengal indicate that the occurrence of high sediment load cannot be explained solely by general circulation model of sea-level change; climate and climatic change also should be taken into account. We suggest that the intensification of the Asian monsoon, particularly in the case of Taiwan, typhoons, which occurred during the early Holocene may have been the root cause of the increased rainfall and thus increased erosion and sediment delivery. This study reconstructs the long-term sedimentary history of the region since the late Quaternary, especially focuses on the increased sediment discharges during the particularly warm and humid paleo-climatic period in NE and SW Taiwan. Moreover, it could help to better understand and predict fluvial sediment fluxes and their geological and societal impacts in response to future global warming.

  1. Regional significance of an early Holocene moraine in Enchantment Lakes basin, North Cascade Range, Washington

    USGS Publications Warehouse

    Waitt, R.B., Jr.; Yount, J.C.; Davis, P.T.

    1982-01-01

    The upper Enchantment Lakes basin in the North Cascade Range of Washington displays two moraine belts, each recording an episode of glacier advance after the end of the last glaciation. The inner belt, the Brynhild, 0.1 to 0.5 km beyond existing glaciers, postdates Mount St. Helens Wn tephra (???450 yr old), which lies only beyond the moraines. The morainal surface is only slightly weathered, is almost barren of lichens, and is devoid of soil, evidence suggesting that the Brynhild moraines are no more than a century old. The outer moraine, the Brisingamen, 0.3 to 0.7 km beyond existing glaciers, is weathered and is covered with large lichens. On and behind the Brisingamen moraine the Mazama ash (6900 yr old) is present beneath the Mount St. Helens Yn and Wn tephras. Despite more than 7 millennia of weathering, the rock surface behind the Brisingamen moraine is measurably less weathered than the surface beyond, which was last glaciated during the Rat Creek advance about 13,000 yr ago. The age of the Brisingamen moraine therefore is probably early Holocene. The Brisingamen moraine evidently correlates with moraines near Glacier Peak, near Mount Rainier, in northeastern and central Oregon, in the southern Canadian Rockies, and in the northern U.S. Rocky Mountains. These regional effects suggest that a climatic episode of cooling or increased snowfall affected the entire region some time during the early Holocene. ?? 1982.

  2. The influence of obliquity in the early Holocene Asian summer monsoon

    NASA Astrophysics Data System (ADS)

    Wu, Chi-Hua; Lee, Shih-Yu; Chiang, John C. H.; Hsu, Huang-Hsiung

    2016-05-01

    The early Holocene climatic optimum is associated with perihelion precession and high obliquity, though most studies emphasize the former over the latter. Asian monsoon proxy records only decisively show the precessional impact. To explore the obliquity effect, four climate simulations are conducted by fixing orbital parameters of present-day (0K), early Holocene (11K), the lowest obliquity (31K), and 11K's precession and eccentricity with 31K's obliquity (11Kp31Ko). We show that high obliquity significantly augments the precessional impact by shifting the Asian monsoon farther north than present. By contrast, the present-day monsoon seasonality can still be identified in the simulations with low obliquity. We argue that the upper tropospheric (South Asian) and lower tropospheric (North Pacific) high-pressure systems are affected by the subtropical atmospheric heating changes responding to obliquity. As a consequence, associated with the changes in meridional gradients of geopotential height and temperature made by the heating, midlatitude transient eddies and monsoon-midlatitude interactions are modulated.

  3. Early-Holocene Fire, Vegetation, and Climate Linkages in the Mid-Latitudes of Western North and South America

    NASA Astrophysics Data System (ADS)

    Whitlock, C.; Bartlein, P.; Markgraf, V.; Bianchi, M.

    2005-12-01

    High-resolution fire history data from temperate forests of western North and South America permit examination of regional and hemispheric linkages between Holocene climate, fire, and ecosystem response. Both regions show striking differences in the seasonality of precipitation that influence fire regimes at present, and evidence from the paleorecord suggests that the intensity of these precipitation regimes was affected by large-scale changes in the climate system. At present, summer-dry areas in both hemispheres are dominated by subtropical high pressure systems, and subsidence in these areas suppresses summer precipitation. Summer-wet areas are influenced by onshore flow of moisture from the subtropical Pacific and Atlantic, and monsoonal precipitation increases convectional activity and fire activity east of the Rockies and Andes. In the western U.S., paleoenvironmental data, including vegetation, fire, and lake-level records, suggest that the summer-dry area became drier in the early Holocene with the expansion of the subtropical high-pressure system. Fire and pollen records from summer-wet areas, in contrast, are consistent with wetter-than-present conditions, presumably because summer insolation strengthened summer monsoonal circulation. The network of South American fire records show: (1) an abrupt increase in fire activity at the Pleistocene/Holocene transition at high-latitudes; (2) widespread fire activity and drought in the early Holocene despite the summer-insolation minimum; (3) north-south differences in fire activity in the mid-Holocene suggesting the onset of the current dipole climate, and (4) locally variable fire signals and a shift to smaller surface fires in the late Holocene consistent with cooler conditions and greater interannual variability. Widespread fire activity in southern South America in the early Holocene is consistent with recent model simulations that suggest warmer SSTs, a weakened pole-to-equator temperature gradient, and a

  4. Early Holocene Centennial-Scale Sea Surface Temperature and Salinity Variability in the Florida Straits

    NASA Astrophysics Data System (ADS)

    Weinlein, W. A.; Schmidt, M. W.; Lynch-Stieglitz, J. M.

    2009-12-01

    Paleoproxy data and modeling studies suggest that Early Holocene (10.5 - 7 kyr BP) climate in the western tropical North Atlantic (TNA) was warmer and wetter than today. Perihelion occurred during boreal summer, resulting in an amplified Early Holocene seasonal cycle and a reorganization of the tropical climate system (Oppo et al., 2007). Trace metal records from the Cariaco Basin (Haug et al., 2001) and ostracod δ18O records from Haiti (Hodell, 1991) suggest a northward shift in the Intertropical Convergence Zone (ITCZ) resulted in decreased evaporation-precipitation values in the western TNA. In addition, the final drainage of large pro-glacial lakes into the North Atlantic at 8.2 kyr BP is thought to have resulted in a meltwater-induced reduction in Atlantic meridional overturning circulation that caused widespread cooling in the circum-Atlantic region (Barber et al., 1999; Clarke et al., 2004; Ellison et al., 2006). In order to reconstruct centennial-scale records of Early Holocene sea surface temperature (SST) and salinity (SSS) variability in the Florida Straits, we will measure δ18O values as well as Mg/Ca and Ba/Ca ratios in the planktonic foraminifera Globigerinoides ruber from two sediment cores recovered from the Florida Straits: KNR166-2 JPC-51 (24°24.70’N, 83°13.14’W, 198 m; ~60-100 cm/kyr sedimentation rate) and KNR166-2 GGC-7 (24°21.50’N, 83°20.90’N, 535 m; ~55 cm/kyr sedimentation rate). SSTs are calculated from Mg/Ca ratios based on a published sediment trap calibration (Anand et al., 2003). Initial measurements of Mg/Ca ratios suggest centennial-scale SST oscillations during the Early Holocene. Calculated SSTs vary from 26.3 to 29.8°C and are within the range of modern seasonal variability for our core locations (25-30°C). Calculated Mg/Ca-SSTs will be combined with G. ruber δ18O values to calculate past δ18Oseawater values (a proxy for SSS) using a laboratory calibrated relationship (Bemis et al., 1998). In addition, Ba

  5. Dust deposition during the Early Holocene on the loess plateaus of the Vojvodina region in Northern Serbia

    NASA Astrophysics Data System (ADS)

    Markovic, Slobodan; Timar-Gabor, Alida; Stevens, Thomas; Guo, Zhengtang; Hao, Qingzhen; Song, Yang; Hambach, Ulrich; Lehmkuhl, Frank; Peric, Zoran; Obreht, Igor; Zeeden, Christian; Veres, Daniel; Gavrilov, Milivoj

    2015-04-01

    The Northern Serbian province of Vojvodina is a lowland area encompassing the confluence of the Danube, Sava, Tisa (Tisza), Drava, Morava and Tamiš (Temes, Timiş) rivers, which separate several remnant loess plateaus. Loess sediments in the Vojvodina region are among the oldest and most complete loess-paleosol formations in Europe. These thick sequences contain a detailed paleoclimatic record since the Early Pleistocene. The better preservation of Serbian loess-paleosol sequences compared to other European loess records is most likely related to the persistence of much drier conditions in the region, coupled with "plateau-like" dust accumulation style. Recently and through detailed luminescence-based chronological investigations of accumulation derived from several loess sections we aimed at addressing the timing of the onset of Holocene soil (S0) formation in the wider region. So far, the chronological results demonstrate a lack of intensive pedogenesis coeval with the postulated Holocene onset (ie., 11.7 ka BP), and continuation of Aeolian dust deposition during the Early Holocene in some of the investigated sections. Lake sediment and speleothem records from the wider area also suggest that, at least regionally, the hydroclimatic characteristics of the Early Holocene differed markedly. This evidence leads to an important question about the validity of previously generalized direct stratigraphic correlations between regional terrestrial environmental archives and global marine and ice core records (direct synchronization of records vs. acknowledging leads/lags), that employ the Late Pleistocene/Holocene boundary at 11.7 as an absolute tie point.

  6. High resolution Lateglacial and early-Holocene summer air temperature records from Scotland inferred from chironomid assemblages

    NASA Astrophysics Data System (ADS)

    Brooks, Stephen J.; Matthews, Ian P.; Birks, Hilary H.; Birks, H. John B.

    2012-05-01

    Lateglacial and early-Holocene mean July air temperatures have been reconstructed, using a chironomid-based inference model, from lake-sediment sequences from Abernethy Forest, in the eastern Highlands of Scotland, and Loch Ashik, on the Isle of Skye in north-west Scotland. Chronology for Abernethy Forest was derived from radiocarbon dates of terrestrial plant macrofossils deposited in the lake sediments. Chronology for Loch Ashik was derived from tephra layers of known ages, the first age-depth model of this kind. Chironomid-inferred temperatures peak early in the Lateglacial Interstadial and then gradually decline by about 1 °C to the beginning of the Younger Dryas (YD). At Abernethy Forest, the Lateglacial Interstadial is punctuated by three centennial-scale cold oscillations which appear to be synchronous with the Greenland Interstadial events GI-1d, when temperatures at Abernethy fell by 5.9 °C, GI-1c, when temperatures fell by 2.3 °C, and GI-1b, when temperatures fell by 2.8 °C. At Loch Ashik only the oscillation correlated with GI-1d is clearly defined, when temperatures fell by 3.8 °C. The start of the YD is clearly marked at both sites when temperatures fell by 5.5 °C at Abernethy Forest and 2.8 °C at Loch Ashik. A warming trend is apparent during the late-YD at Abernethy Forest but at Loch Ashik late-YD temperatures became very cold, possibly influenced by its close proximity to the Skye ice-field. The rapidly rising temperatures at the YD - Holocene transition occur about 300 years earlier at both sites than changes in sediment lithology and loss-on-ignition. The temperature trends at both sites are broadly similar, although between-site differences may result from the influence of local factors. Similar climate trends are found at other sites in the northern British Isles. However, the British summer temperature records differ in detail from trends in the oxygen-isotope records from the Greenland ice-cores and from other chironomid

  7. Early Holocene variability in the Arctic Gateway - High-resolution records reflecting Atlantic Water advection and ice coverage

    NASA Astrophysics Data System (ADS)

    Spielhagen, Robert F.; Bauch, Henning A.; Maudrich, Martin; Not, Christelle; Telesinski, Maciej M.; Werner, Kirstin

    2015-04-01

    The Arctic Gateway between Greenland and Svalbard is the main passage for the advection of Atlantic Water to the Arctic Ocean. Water temperature and intensity of this advection largely determine the degree of ice coverage which is fed by sea ice export from the north. Supported by a maximum in insolation, the Early Holocene was a period of extraordinarily strong advection and relatively high near-surface water temperatures in the eastern Nordic Seas (cf. Risebrobakken et al., 2011, Paleoceanography v. 26). Here we present a synthesis of radiocarbon-dated records from the northern and western part of this area, reaching from the SW Greenland Sea (73°N) to the Yermak Plateau (81°N) and revealing temporal and spatial differences in the development of the so-called Holocene Thermal Maximum (HTM). In the northern part of this region, the HTM started ca. 11-10.5 ka as indicated by rapidly increasing amounts of subpolar planktic foraminifers in the sediments. In the eastern Fram Strait and on the Yermak Plateau, our records of (sub)millennial scale resolution show that the maximum influx terminated already 2,000 years later (9-8 ka). Most likely, this development went along with a N-S relocation of the sea ice margin. According to the current stratigraphic model for a core with submillennial-scale resolution from Vesterisbanken seamount (73°N) in the Greenland Sea, the timing was different there. Increasing total amounts of planktic foraminifers in the sediment indicate an early (11-10 ka) reduction in sea ice coverage also in this region. However, evidence from subpolar planktic foraminifers for maximum Atlantic Water advection is younger (9-6 ka) than in the north. Apparently, the site in the SW Greenland Sea was affected by Atlantic Water in the Greenland Gyre that decoupled from the northward flowing Norwegian Atlantic Current/Westspitsbergen Current south of the Fram Strait. Thus, in a suite of events, strong Atlantic Water advection first affected the

  8. Holocene accumulation and ice flow near the West Antarctic Ice Sheet Divide ice core site

    NASA Astrophysics Data System (ADS)

    Koutnik, Michelle R.; Fudge, T. J.; Conway, Howard; Waddington, Edwin D.; Neumann, Thomas A.; Cuffey, Kurt M.; Buizert, Christo; Taylor, Kendrick C.

    2016-05-01

    The West Antarctic Ice Sheet Divide Core (WDC) provided a high-resolution climate record from near the Ross-Amundsen Divide in Central West Antarctica. In addition, radar-detected internal layers in the vicinity of the WDC site have been dated directly from the ice core to provide spatial variations in the age structure of the region. Using these two data sets together, we first infer a high-resolution Holocene accumulation-rate history from 9.2 kyr of the ice-core timescale and then confirm that this climate history is consistent with internal layers upstream of the core site. Even though the WDC was drilled only 24 km from the modern ice divide, advection of ice from upstream must be taken into account. We evaluate histories of accumulation rate by using a flowband model to generate internal layers that we compare to observed layers. Results show that the centennially averaged accumulation rate was over 20% lower than modern at 9.2 kyr before present (B.P.), increased by 40% from 9.2 to 2.3 kyr B.P., and decreased by at least 10% over the past 2 kyr B.P. to the modern values; these Holocene accumulation-rate changes in Central West Antarctica are larger than changes inferred from East Antarctic ice-core records. Despite significant changes in accumulation rate, throughout the Holocene the regional accumulation pattern has likely remained similar to today, and the ice-divide position has likely remained on average within 5 km of its modern position. Continent-scale ice-sheet models used for reconstructions of West Antarctic ice volume should incorporate this accumulation history.

  9. Effects of melting ice sheets and orbital forcing on the early Holocene warming in the extratropical Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Zhang, Yurui; Renssen, Hans; Seppä, Heikki

    2016-05-01

    The early Holocene is marked by the final transition from the last deglaciation to the relatively warm Holocene. Proxy-based temperature reconstructions suggest a Northern Hemisphere warming, but also indicate important regional differences. Model studies have analyzed the influence of diminishing ice sheets and other forcings on the climate system during the Holocene. The climate response to forcings before 9 kyr BP (referred to hereafter as kyr), however, remains not fully comprehended. We therefore studied, by employing the LOVECLIM climate model, how orbital and ice-sheet forcings contributed to climate change and to these regional differences during the earliest part of the Holocene (11.5-7 kyr). Our equilibrium experiment for 11.5 kyr suggests lower annual mean temperatures at the onset of the Holocene than in the preindustrial era with the exception of Alaska. The magnitude of this cool anomaly varied regionally, and these spatial patterns are broadly consistent with proxy-based reconstructions. Temperatures throughout the whole year in northern Canada and northwestern Europe for 11.5 kyr were 2-5 °C lower than those of the preindustrial era as the climate was strongly influenced by the cooling effect of the ice sheets, which was caused by enhanced surface albedo and ice-sheet orography. In contrast, temperatures in Alaska for all seasons for the same period were 0.5-3 °C higher than the control run, which were caused by a combination of orbital forcing and stronger southerly winds that advected warm air from the south in response to prevailing high air pressure over the Laurentide Ice Sheet (LIS). The transient experiments indicate a highly inhomogeneous early Holocene temperature warming over different regions. The climate in Alaska was constantly cooling over the whole Holocene, whereas there was an overall fast early Holocene warming in northern Canada by more than 1 °C kyr-1 as a consequence of progressive LIS decay. Comparisons of simulated

  10. Exceptional preservation of children's footprints from a Holocene footprint site in Namibia

    NASA Astrophysics Data System (ADS)

    Bennett, Matthew R.; Morse, Sarita A.; Liutkus-Pierce, Cynthia; McClymont, Juliet; Evans, Mary; Crompton, Robin H.; Francis Thackeray, J.

    2014-09-01

    Here we report on a Holocene inter-dune site close to Walvis Bay (Namibia) which contains exceptionally well-preserved children's footprints. The footprint surface is dated using Optically Stimulated Luminescence (OSL) methods to approximately 1.5 ka. These dates are compared to those obtained at nearby footprint sites and used to verify a model of diachronous footprint surfaces and also add to the archaeological data available for the communities that occupied these near-coastal areas during the Holocene. This model of diachronous footprint surfaces has implications for other soft-sediment footprint sites such as the 1.5 Ma old footprints at Ileret (Kenya). The distribution of both human and animal tracks, is consistent with the passage of small flock of small ungulates (probably sheep/goats) followed by a group of approximately 9 ± 2 individuals (children or young adults). Age estimates from the tracks suggest that some of the individuals may have been as young as five years old. Variation in track topology across this sedimentologically uniform surface is explained in terms of variations in gait and weight/stature of the individual print makers and is used to corroborate a model of footprint morphology developed at a nearby site. The significance of the site within the literature on human footprints lies in the quality of the track preservation, their topological variability despite a potentially uniform substrate, and the small size of the tracks, and therefore the inferred young age of the track-makers. The site provides an emotive insight into the life of the track-makers.

  11. Holocene temperature variations at a high-altitude site in the Eastern Alps: a chironomid record from Schwarzsee ob Sölden, Austria

    PubMed Central

    Ilyashuk, Elena A.; Koinig, Karin A.; Heiri, Oliver; Ilyashuk, Boris P.; Psenner, Roland

    2011-01-01

    Few well-dated, quantitative Holocene temperature reconstructions exist from high-altitude sites in the Central Eastern Alps. Here, we present a chironomid-based quantitative reconstruction of mean July air temperatures (TJuly) throughout the Holocene for a remote high-mountain lake, Schwarzsee ob Sölden, situated above the treeline at 2796 m a.s.l. in the Austrian Alps. Applying a chironomid-temperature inference model developed from lakes of the Alpine region to a high-resolution chironomid record from the lake provides evidence for early Holocene (ca 10000–8600 cal yr BP) TJuly of up to 8.5 °C, i.e. >4 °C above the modern (1977–2006) mean July temperature. The reconstruction reveals the so-called ‘8.2-ka cold event’ centered at ca 8250–8000 cal yr BP with temperatures ca 3 °C below the early-Holocene thermal maximum. Rather warm (ca 6 °C) and productive conditions prevailed during ca 7900–4500 cal yr BP. The chironomid record suggests a climate transition between ca 5200 and 4500 cal yr BP to cooler TJuly. A distinct cooling trend is evident from ca 4500 until ca 2500 cal yr BP. Thereafter, the study site experienced its coldest conditions (around 4 °C or less) throughout the rest of the Holocene, with the exception of the warming trend during the late 20th century. Beside other factors, the Northern Hemisphere summer insolation seems to be the major driving force for the long-term trends in TJuly at high altitudes in the Eastern Alps. Due to the extreme location of the lake and the limited temperature range represented by the applied calibration data set, the chironomid-based temperature reconstruction fails to track phases of the late-Holocene climatic history with TJuly cooler than 4 °C. Further chironomid-based palaeoclimate model and down-core studies are required to address this problem, provide more realistic TJuly estimates from undisturbed high-altitude lakes in the Alps, and extract a reliable regional

  12. Pollen from accurately dated speleothems supports alpine glacier low-stands during the early Holocene

    NASA Astrophysics Data System (ADS)

    Festi, Daniela; Hoffmann, Dirk L.; Luetscher, Marc

    2016-07-01

    Deciphering pollen assemblages from alpine speleothems holds potential to provide unique information about past vegetation in rapidly changing environments. Here, we reconstruct subsurface aerosol transport at Milchbach cave (Switzerland, 1840 m asl) based on the pollen content of two Holocene stalagmites. We demonstrate that pollen is chiefly associated with bacterially mediated calcite fabrics, typical of a well-ventilated cave system. In contrast, pollen is absent from columnar calcite fabrics confirming that hydrological transport is not a significant process for the incorporation of pollen into speleothems at Milchbach cave. Our results support significant changes in the subsurface ventilation regime, which can be associated with the waxing and waning of Upper Grindelwald glacier. Pollen assemblages obtained from six carbonate sub-samples attest the presence of a mixed deciduous forest in the Grindelwald valley during the early and middle Holocene, in agreement with coeval regional pollen records. This study demonstrates that even small amounts of calcite (0.3-2.8 cm3) are capable of delivering pollen spectra representative of the original vegetation if sufficiently elevated deposition fluxes are provided.

  13. Holocene Core Logs and Site Statistics for Modern Patch-Reef Cores: Biscayne National Park, Florida

    USGS Publications Warehouse

    Reich, Christopher D.; Hickey, T. Don; DeLong, Kristine L.; Poore, Richard Z.; Brock, John C.

    2009-01-01

    ; however, their shapes may be due to a slightly lowered sea level or a stillstand in the middle-Holocene around 4 ka that caused erosion of the shallower reefs and allowed the deeper reefs to remain unaffected. Lidz and others (2006) have suggested a stillstand around 4 ka that carved a 2.5-kilometer (km)-wide nearshore rock ledge into the seaward side of every island in the Florida Keys. The objectives of this study were to sample living corals to understand the more recent (<200 years) changes in climate and environmental conditions of the area and to investigate the Holocene (in this case, <8,000 years in the Florida Keys) depositional history at progressively deeper patch-reef sites. This report provides statistics for the cores and core sites and a basic lithologic description of these Holocene cores.

  14. Precise Surface Exposure Dating of Early Holocene and Little Ice Age Moraines in the Cordillera Vilcabamba of Southern Peru

    NASA Astrophysics Data System (ADS)

    Licciardi, J. M.; Schaefer, J. M.; Lund, D. C.; Taggart, J. R.

    2008-12-01

    We have established precise ages of two glacial events in the tropical Andean highlands of southern Peru. The field site is located on the flanks of Nevado Salcantay (6271 m asl; 13°20'S latitude), the highest peak in the Cordillera Vilcabamba. A two-fold sequence of nested lateral and end moraines was mapped in a glacial trough emanating from the south face of Salcantay. Well-defined outer and inner moraines were deposited by valley glaciers that terminated 5 km and 3 km, respectively, from their head on the Salcantay massif. Cosmogenic 10Be surface exposure dating of boulders on the outer (n = 7) and inner (n = 7) moraine crests expands upon initial age control for these deposits and improves substantially on the precision of earlier 10Be measurements. The new results yield mean ages of 9.0 ± 0.3 ka for the outer moraine and 195 ± 24 years for the inner moraine, corresponding to glacial events during the early and latest Holocene. These ages are derived using the CRONUS-Earth 10Be exposure age calculator with Lal-Stone production rate scaling and the default height-pressure relationship. The inner moraine age correlates with the timing of the Little Ice Age as defined from northern mid- and high latitude records, and indicates considerable expansion of glaciers heading on Nevado Salcantay during this climatic minimum. Recent geomorphic mapping has identified similar sequences of moraines in adjacent drainages on and near Salcantay, suggesting a broader regional signal of two prominent Holocene glacial events in this segment of the southern Peruvian Andes; 10Be dating of these additional moraines is underway. Our new glacier chronologies complement ice core and lacustrine paleoclimate records in the vicinity, thereby increasing spatial and temporal coverage for identifying patterns of climate change in the tropical Andes during the Holocene. Apart from their paleoclimatic significance, the results also demonstrate a newly- developed capability of 10Be exposure

  15. Inter-group violence among early Holocene hunter-gatherers of West Turkana, Kenya.

    PubMed

    Mirazón Lahr, M; Rivera, F; Power, R K; Mounier, A; Copsey, B; Crivellaro, F; Edung, J E; Maillo Fernandez, J M; Kiarie, C; Lawrence, J; Leakey, A; Mbua, E; Miller, H; Muigai, A; Mukhongo, D M; Van Baelen, A; Wood, R; Schwenninger, J-L; Grün, R; Achyuthan, H; Wilshaw, A; Foley, R A

    2016-01-21

    The nature of inter-group relations among prehistoric hunter-gatherers remains disputed, with arguments in favour and against the existence of warfare before the development of sedentary societies. Here we report on a case of inter-group violence towards a group of hunter-gatherers from Nataruk, west of Lake Turkana, which during the late Pleistocene/early Holocene period extended about 30 km beyond its present-day shore. Ten of the twelve articulated skeletons found at Nataruk show evidence of having died violently at the edge of a lagoon, into which some of the bodies fell. The remains from Nataruk are unique, preserved by the particular conditions of the lagoon with no evidence of deliberate burial. They offer a rare glimpse into the life and death of past foraging people, and evidence that warfare was part of the repertoire of inter-group relations among prehistoric hunter-gatherers. PMID:26791728

  16. Late-Glacial to early Holocene basin development of annually laminated Lake Tiefer See

    NASA Astrophysics Data System (ADS)

    Theuerkauf, Martin; Lorenz, Sebastian; Schult, Manuela; Lampe, Reinhard; Dräger, Nadine; Wulf, Sabine; Brauer, Achim

    2014-05-01

    Lake Tiefer See (N 53.59°, E 12.53°) is one of the rare lakes with a long sequence of annually laminated Holocene sediments in northern Central Europe. The lake is thus of great potential for past climate, vegetation and human land use studies. It furthermore provides a valuable link between laminated lakes in more oceanic climates of the Eifel region and NW Germany and laminated lakes in the more continental climate of Poland. The sediments of Lake Tiefer See are not uniform but show repeated changes in varve composition and include several non-varved sequences. Interpreting these changes requires a sound understanding of the deposition processes in the lake and the development of the lake basin itself. While modern sediment deposition is studied in an extensive monitoring program, we explore lake basin development using numerous cores from the lake margins down to the bottom of the lake. The lake is exceptionally deep (62 m) with steep slopes and may thus be susceptible to sediment re-deposition and focusing. Most marginal cores, which reach down to 10 m water depth, show a prominent basal peat layer. This peat layer indicates that basin development started by paludification of an originally flat surface following dead-ice melting. However, even in neighboring cores the timing of the onset of peat formation appears to differ substantially. While in some cores, the prominent Laacher See Tephra (12.880 cal. BP) is found at the bottom of the peat layer, it is found well above the peat basis in other cores. Dead-ice melting may thus initially have produced a pattern of shallow depressions with ongoing peat formation within a still terrestrial surface. The formation of the deep lake is than indicated by an abrupt shift to calcareous gyttjas, which show an initially increased silicate content. The lake obviously only developed long after first peat deposition, possibly in the early Holocene. Further dates to verify this hypothesis are expected. In several marginal

  17. Micro-facies analyses of late Holocene sediments from the Ein Gedi site (Dead Sea)

    NASA Astrophysics Data System (ADS)

    Neugebauer, I.; Brauer, A.; Schwab, M. J.; Frank, U.; Dulski, P.

    2012-04-01

    Late Holocene Dead Sea sediments of the Ein Gedi profile at the western Dead Sea shore provide high-resolution information about small-scale climatic variations in the Levant. Earlier investigations by Migowski et al. (2004, 2006) demonstrated the high potential of the Ein Gedi site for reconstructing the paleoenvironment of this climate-sensitive region, but also the need for high-resolution analyses. In the study presented here, a multi-proxy approach of micro-facies analyses from thin sections, µXRF element scanning and further magnetic susceptibility measurements allowed detailed analyses of a 2.75m long section from the DSEn composite profile spanning the time from approximately 2 to 4 ka BP. The analysed DSEn sequence of the Dead Sea margin is characterised by a continuous succession of evaporitic varves, composed of alternating detrital and aragonite and/or gypsum layers with intercalated earthquake-induced mixed layers (Marco et al., 1996). In the lower part of the investigated interval a sand deposit is associated to lake-level decline around 3.3 ka BP (Bookman (Ken-Tor) et al., 2004) in the Late Bronze Age. The aim of this study is to establish a detailed high-resolution time series of extreme events and decadal-scale variations in the eastern Mediterranean climate system. Using this data set will further enable determining the influence of the North Atlantic Oscillation and solar irradiation changes on that region. Another objective will be to synchronise the DSEn interval with the new ICDP Dead Sea Deep Drilling Project (DSDDP) cores from the northern deep basin in order to compare sedimentation processes at the Dead Sea shore with those from the deep basin. Bookman (Ken-Tor), R., Enzel, Y., Agnon, A., Stein, M., 2004. Late Holocene lake levels of the Dead Sea. Geological Society of America Bulletin, May/June, 555-571. Marco, S., Stein, M., Agnon, A., 1996. Long-term earthquake clustering: A 50,000-year paleoseismic record in the Dead Sea Graben

  18. Early and Middle Holocene evidence for plant use and cultivation in the Middle Cauca River Basin, Cordillera Central (Colombia)

    NASA Astrophysics Data System (ADS)

    Aceituno, Francisco J.; Loaiza, Nicolás

    2014-02-01

    This paper presents the latest results of research done in the Colombian Andean region known as Middle Cauca River Basin, an important location for the study of the origins of plant use and the dispersal of domesticates throughout the Americas due to its geographical position in northwest South America. We discuss human-environment interactions during Pleistocene/Holocene transition to middle Holocene (ca 10,000-4000 BP), specifically human-plant interaction and environmental factors that led to the adoption of horticultural practices. Three lines of evidence are analyzed: archaeological stratigraphy, lithic technology, and microbotanical remains. Our results suggest that early Holocene environmental stability allowed Middle Cauca settlers to use the diverse local resources for several millennia, altering the local vegetation, and leading to the development of horticultural practices that included the use of both local and foreign plants. These results inform the ongoing debate about the antiquity and nature of plant domestication and dispersals in the Americas.

  19. Lateglacial and early-Holocene climate variability reconstructed from multi-proxy records on Andøya, northern Norway

    NASA Astrophysics Data System (ADS)

    Birks, Hilary H.; Aarnes, Ingelinn; Bjune, Anne E.; Brooks, Stephen J.; Bakke, Jostein; Kühl, Norbert; Birks, H. John B.

    2014-04-01

    We reconstruct mean July temperature (Tjul) from three sites on the island of Andøya, northern Norway for the period 15 000-9000 cal yr BP using three biotic proxies. A probabilistic indicator species approach (pdf method) was used for plant macrofossil data from all sites (M-Tjul). Reconstructions based on pollen (P-Tjul) (2 sites) and chironomids C-Tjul) (1 site) were done using weighted averaging and weighted-averaging partial least-squares, respectively. A sediment proxy for catchment glacier development was measured at the main site, Lusvatnet. The July temperature reconstructions from all the sites show a similar development through the deglaciation. An initial July temperature of 4 °C increased to a maximum of 7-8 °C during the Allerød at c.13 200 cal yr BP. There was no marked cooling at the start of the Younger Dryas (YD) chronozone, at Lusvatnet, C-Tjul decreased after 12 700 cal yr BP to a low of 6 °C at about 12 550 cal yr BP before increasing markedly around 12 400 cal yr BP. Conversely, P-Tjul rose slowly through the early YD. Both proxies exceeded the Allerød temperatures for around 300 years before decreasing towards a minimum of 6 °C at c. 12 000 cal yr BP. M-Tjul maintained a mean of c. 8 °C throughout the YD. Different sensitivities of proxies are discussed. Their different responses during the YD at the three sites, along with the glacial evidence, highlight the role of aridity. At c. 11 500 cal yr BP, July temperatures increased rapidly over Andøya to about 10 °C, and then rose gradually to maximum values of 12 °C at c. 9700 cal yr BP. The temperature reconstructions are consistent with the flow of Atlantic water into the Nordic Seas except during the YD, when variability in sea ice may have been more important. During the early Holocene there are some differences between sites, resulting from local site factors such as altitude and exposure, soil development, and catchment instability.

  20. Early to Middle Holocene landscape exploitation in a drying environment: Two case studies compared from the central Sahara (SW Fezzan, Libya)

    NASA Astrophysics Data System (ADS)

    Cremaschi, Mauro; Zerboni, Andrea

    2009-08-01

    The erg Uan Kasa and the wadi Tanezzuft (Libyan Sahara) reacted in different ways to Holocene climatic changes. Consequently, the human groups settled there responded with different ways of adaptation to the drying environment. In the erg Uan Kasa, shallow lakes were formed from the Early to the Mid-Holocene, and their shores were densely inhabited from the Epipalaeolithic to the Pastoral-Neolithic periods. The erg dried out at c. 5000 years BP, but the area was not completely abandoned, as indicated by minor Late Pastoral-Neolithic sites composed of scattered fireplaces. During the wet Holocene, the wadi Tanezzuft was a large meandering river, and its banks were densely settled. At c. 5000 years BP, the stream was not completely dried out, but it changed its pattern, originating an alluvial plain. A large oasis was formed between c. 4000 and 2000 years BP, exploited by Late Pastoral-Neolithic pastoral communities, and later by Garamantians, which introduced soil management and agricultural practices. The Tanezzuft oasis suffered a drastic reduction in size during the first centuries AD, at the time of the abandonment of the Garamantian settlements.

  1. Lateglacial/early Holocene fluvial reactions of the Jeetzel river (Elbe valley, northern Germany) to abrupt climatic and environmental changes

    NASA Astrophysics Data System (ADS)

    Turner, Falko; Tolksdorf, Johann Friedrich; Viehberg, Finn; Schwalb, Antje; Kaiser, Knut; Bittmann, Felix; von Bramann, Ullrich; Pott, Richard; Staesche, Ulrich; Breest, Klaus; Veil, Stephan

    2013-01-01

    Mechanisms of climatic control on river system development are still only partially known. Palaeohydrological investigations from river valleys often lack a precise chronological control of climatic processes and fluvial dynamics, which is why their specific forces remain unclear. In this multidisciplinary case study from the middle Elbe river valley (northern Germany) multiple dating of sites (palynostratigraphy, radiocarbon- and OSL-dating) and high-resolution analyses of environmental and climatological proxies (pollen, plant macro-remains and ostracods) reveal a continuous record of the environmental and fluvial history from the Lateglacial to the early Holocene. Biostratigraphical correlation to northwest European key sites shows that river system development was partially out of phase with the main climatic shifts. The transition from a braided to an incised channel system predated the main phase of Lateglacial warming (˜14.6 ka BP), and the meandering river did not change its drainage pattern during the cooling of the Younger-Dryas period. Environmental reconstructions suggest that river dynamics were largely affected by vegetation cover, as a vegetation cover consisting of herbs, dwarf-shrubs and a few larger shrubs seems to have developed before the onset of the main Lateglacial warming, and pine forests appear to have persisted in the river valley during the Younger Dryas. In addition, two phases of high fluvial activity and new channel incision during the middle part of the Younger Dryas and during the Boreal were correlated with changes from dry towards wet climatic conditions, as indicated by evident lake level rises. Lateglacial human occupation in the river valley, which is shown by numerous Palaeolithic sites, forming one of the largest settlement areas of that period known in the European Plain, is assigned to the specific fluvial and environmental conditions of the early Allerød.

  2. Links between early Holocene ice-sheet decay, sea-level rise and abrupt climate change

    NASA Astrophysics Data System (ADS)

    Törnqvist, Torbjörn E.; Hijma, Marc P.

    2012-09-01

    The beginning of the current interglacial period, the Holocene epoch, was a critical part of the transition from glacial to interglacial climate conditions. This period, between about 12,000 and 7,000 years ago, was marked by the continued retreat of the ice sheets that had expanded through polar and temperate regions during the preceding glacial. This meltdown led to a dramatic rise in sea level, punctuated by short-lived jumps associated with catastrophic ice-sheet collapses. Tracking down which ice sheet produced specific sea-level jumps has been challenging, but two events between 8,500 and 8,200 years ago have been linked to the final drainage of glacial Lake Agassiz in north-central North America. The release of the water from this ice-dammed lake into the ocean is recorded by sea-level jumps in the Mississippi and Rhine-Meuse deltas of approximately 0.4 and 2.1 metres, respectively. These sea-level jumps can be related to an abrupt cooling in the Northern Hemisphere known as the 8.2 kyr event, and it has been suggested that the freshwater release from Lake Agassiz into the North Atlantic was sufficient to perturb the North Atlantic meridional overturning circulation. As sea-level rise on the order of decimetres to metres can now be detected with confidence and linked to climate records, it is becoming apparent that abrupt climate change during the early Holocene associated with perturbations in North Atlantic circulation required sustained freshwater release into the ocean.

  3. Evidence of Early Holocene Glacial Advances in Southern South America from Cosmogenic Surface Exposure Dating

    NASA Astrophysics Data System (ADS)

    Douglass, D. C.; Singer, B. S.; Kaplan, M. R.; Ackert, R. P.; Mickelson, D. M.; Caffee, M. W.

    2004-12-01

    10Be and 36Cl cosmogenic nuclide surface exposure dating of erratic boulders reveal two glacier advances in southern South America (46°S) during the Early Holocene. Seven of ten boulders from the outer moraine yield a weighted mean of 8.5±0.7 ka and five of six boulders from the inner moraine yield a weighted mean age of 6.2±0.8 ka (2σ uncertainties). The four outliers are anomalously old (interpreted to contain inherited cosmogenic isotopes from prior exposure) and are identified on the basis of Chi-Squared statistics and bi-modal probability distribution curves. These glacial advances are likely the result of a northward migration of the southern westerlies causing an increase in precipitation and/or a decrease in temperature at this latitude. Reconstructions of equilibrium line altitudes (ELA) at the times of moraine deposition based on Accumulation Area Rations (AARs) are about 300 m lower than modern. This ELA depression is not particularly sensitive to the AAR used, and corresponds to conditions 2.4° C cooler (if no change in precipitation), or 1000 mm/a wetter (if no change in temperature) than the modern climate. The older advance precedes the currently accepted initiation of Holocene glacial activity in southern South America by about 3000 years, and appears to be temporally synchronous with the "8.2 ka event" recorded in Greenland and many other parts of the world. The younger advance is slightly older than, but indistinguishable from, documented neoglacial advances and climate changes in southern South America and four other continents. If there are causal links between these temporally synchronous, globally distributed events, then millennial scale climate changes appear to involve reorganization of global weather systems (such as migration of the southern westerlies), or may be externally forced (e.g. solar variability).

  4. A Record of Early to Middle Holocene Hydroclimate Variability from the West African Sahel

    NASA Astrophysics Data System (ADS)

    McIntosh, R.; Douglas, P. M.; Warren, C.; Meyers, S. R.; Coutros, P.; Park, D. P.

    2011-12-01

    The African Humid Period (ca. 14.8 to 5.5 ka) is an interval of wet climates across northwest Africa, with evidence for widespread lake basins and savannah vegetation in areas that are now desert. There are few high-resolution continental records of hydrologic variability during the African humid period however. In particular, it remains uncertain how periods of north Atlantic climate variability were expressed in northwest Africa. We present results from a 5.4 meter sediment core from Lake Fati in northern Mali (16.29° N, 3.71° W), which represents the first lake sediment core from the western Sahel. The Lake Fati core contains a continuous record of lake mud from 10.43 to 4.66 kyr BP. Centimeter scale XRF scanning indicates strong covariation between iron, calcium, manganese and phosphorous abundance due to enrichment of these elements during periods of enhanced deposition of authigenic siderite. Preliminary oxygen isotope measurements indicate that authigenic siderite δ18O values are positively correlated with Fe counts, suggesting that siderite deposition increased during drier periods with greater evaporation of lake waters. These drying events occurred on decadal to centennial time scales, with higher-frequency variability during the early Holocene. Peaks in zirconium and titanium abundance coincide with some of the inferred dry periods, suggesting that deposition of aeolian silt coincided with periods of increased evaporation of lake water. A roughly 30 year interval of sand deposition at ~8.33 kyr BP suggests major drying and activation of aeolian sand deposition. This abrupt climate change could be related to the 8.2 ka event in the North Atlantic; further efforts to refine the sediment core age model will constrain the relationship of this rapid drying to abrupt climate change in the North Atlantic. Aluminum and silicon counts co-vary for much of the lake Fati record, and are related to input of terrigenous sediment, primarily during seasonal flooding

  5. Erosion modelling and sedimentary balance in an early anthropised watershed during the Holocene

    NASA Astrophysics Data System (ADS)

    Vella, C.; Canut, V.; Parisot, J.-C.; Hermitte, D.; Fleury, J.; Dussouillez, P.; Pailles, C.; Duval, S.; Chausserie-Laprée, J.

    2009-04-01

    The ria of Renaïres, on the western part of a small calcareous range between Marseilles and the Rhône delta, is a natural, elongated and narrow calanque drained by only one stream, the Reraille. The reduced size of its catchment (12km2) enables the easy identification of the local influence of climate and sea level fluctuations on sedimentation rythms. The relative sea level rise was revealed by peat deposits located only 10 kilometers away from the ria (Vella et al., 2005). Human occupation is deduced by archaeological data on the catchment area (Martigues Local council Services) allowing comparison between diachronic maps of human occupation from the Neolitic to medieval period. As such, the watershed of Reraille is the perfect site to study influences of human impact on erosion and sedimentation during the Holocene. Sedimentation in the upper part of the basin has been completely excavated by recent archaelogical works prior to urban development. Sediment accumulation is totaly quantified and dated by archaelogical remains and radiocarbon datings. In the bottom of the basin, erosional products are measured from the sedimentation trapped in the highly protected ria. Quantification of the trapped sediment was determined from 10 geotechnical drillholes, 5 cored holes of 10m length, and an electrical resistivity survey comprising a longitudinal profile and 4 cross-sections. The data sets were integrated into a GIS program and allowed a 3D reconstruction of volumes trapped at the exit of the system. Although the outgoing volumes are considered as unimportant, an offshore seismic reflection survey is planned for september 2009 to establish baseline data. The results indicate that the sedimentation speed increased in the upper part of the catchment : sedimentation was low before VIth century BC, it increased for 1500 years and was highest during the modern period. This sedimentation dynamic could suggest an increased destabilization of hillsides particularly during

  6. Pedogenic calcite as evidence for an early Holocene dry period in the San Francisco Bay area, California

    USGS Publications Warehouse

    Borchardt, G.; Lienkaemper, J.J.

    1999-01-01

    Rainfall at the site of Union City, California, during early Holocene time appears to have been about half that of today, 470 mm/yr. We base this conclusion on detailed descriptions and particle-size analyses of 12 soil profiles and 1:20 scale logs of the fluvial stratigraphy in two 100-m-long, 5-m-deep excavations dug perpendicular to the axis of an alluvial fan along the Hayward fault. Subsidence and right-lateral movement along the fault allowed an offset stream to produce a nearly continuous alluvial record documented by 35 14C ages on detrital charcoal. Bk (calcitic) horizons in paleosols developed in the fan suggest that a relatively dry climatic period occurred from 10 to 7 ka (calendar-corrected ages). The pedogenic calcite exists primarily as vertically oriented filaments and fine, cavernous nodules formed at ped intersections. Soils and paleosols formed before 10 ka or since 7 ka did not have Bk horizons. Bk horizons that were buried suddenly at 7 ka were overlain by leached zones averaging 41 ?? 3 cm thick - about half the current depth of leaching.

  7. Palaeoenvironmental and cultural dynamics of the coast of Málaga (Andalusia, Spain) during the Upper Pleistocene and early Holocene

    NASA Astrophysics Data System (ADS)

    Cortés-Sánchez, Miguel; Morales-Muñiz, Arturo; Simón-Vallejo, María D.; Bergadà-Zapata, M. Mercè; Delgado-Huertas, Antonio; López-García, Pilar; López-Sáez, José A.; Lozano-Francisco, M. Carmen; Riquelme-Cantal, José A.; Roselló-Izquierdo, Eufrasia; Sánchez-Marco, Antonio; Vera-Peláez, José L.

    2008-11-01

    The impact of late Upper Pleistocene climate change in the western Mediterranean region has been mainly documented through marine records. Archaeological and geomorphological continental records now available for the coast of Málaga complement these records for the second part of the last major glacial episode and the early stages of the Holocene. This paper provides an overview of the archaeological, chronological and palaeoenvironmental data from the end of the Middle Palaeolithic period to the Epipalaeolithic. Sequences from the two major sites, Nerja and Bajondillo, indicate a mosaic-type response of ecosystems to the rapidly shifting conditions of the Last Glacial episode. Terrestrial mammals, for example, show no major variations from present-day communities. Plant remains in contrast, demonstrates the existence of localised refuge areas for species that would not otherwise have survived in the more widely prevailing climatic conditions of the time, whereas remains of fish and, secondarily, birds demonstrate the existence of communities without any present-day analogues combining Mediterranean and Boreal (i.e., northern Atlantic) taxa. From an archaeological standpoint, the major cultural shift is the onset of marine fishing, beginning in the Solutrean. This coincided with the end of the Last Glacial Maximum (LGM) episode. The faunal record also testifies to the rising importance of marine resources more generally. Although the data have not been used systematically to test the validity of the Broad Spectrum Revolution (BSR) hypothesis, the hints for it in the area seem compelling from the start of the Solutrean onwards.

  8. Human impact and Holocene climatic change in the archaeological site 'Piani della Corona

    NASA Astrophysics Data System (ADS)

    Pelle, Teresa; Scarciglia, Fabio; La Russa, Mauro F.; Natali, Elena; Tinè, Vincenzo

    2010-05-01

    A pedoarchaeological study was carried out in the archaeological site "Piani della Corona", located on a wide terrace at 500 m a.s.l. along the southwestern coast of Calabria, in southern Italy. The archaeological excavations exhumed an extensive settlement related to old to medium Bronze Age phases and traces of late Neolithic human colonization. On the basis of archaeological finds the pedostratigraphic succession can be partly dated. It consists of soils with variable features and andic properties, which include yellowish-brown (in places more reddish), deep argillic (Bt) horizons with variable amounts of clay coatings in pores and dark brown infillings of soil material rich in organic matter, in places overlaid by thin, severely truncated, brown to dark brown, organic-mineral (A) horizons. These layers include late Neolithic ceramic artefacts (Diana style facies) and typical incineration burials found in biconical vases, that can be referred to 6500-5000 years BP. The prehistoric layers are widely overlaid and strongly superimposed by a paleosurface of the early to medium Bronze age. This surface is affected by many pole holes left by large rectangular, apsidal wooden huts (not preserved), ploughed furrows, excavated cisterns, ditches and trenches, often filled by organic-rich dark brown material. Also hearths with charcoal remains, burials, vases and other diagnostic ceramic fragments occur. The upper portion of the pedostratigraphic succession consists of thicker brown A horizons, that appear cyclically ploughed during historical times (archaeologically not well dated as a consequence of their reworking for agricultural practices), with abrupt irregular boundaries often entering the underlying horizons. Micromorphological observations confirmed the presence of clay coatings within pores of Bt horizons, showing that they represent relict features (i.e. related to inactive illuvial processes, at present), as often fragmented and with smooth-banded to grainy

  9. North African vegetation-precipitation feedback in early and mid-Holocene climate simulations with CCSM3-DGVM

    NASA Astrophysics Data System (ADS)

    Rachmayani, R.; Prange, M.; Schulz, M.

    2015-02-01

    The present study analyses the sign, strength, and working mechanism of the vegetation-precipitation feedback over North Africa in middle (6 ka BP) and early Holocene (9 ka BP) simulations using the comprehensive coupled climate-vegetation model CCSM3-DGVM (Community Climate System Model version 3 and a dynamic global vegetation model). The coupled model simulates enhanced summer rainfall and a northward migration of the West African monsoon trough along with an expansion of the vegetation cover for the early and middle Holocene compared to the pre-industrial period. It is shown that dynamic vegetation enhances the orbitally triggered summer precipitation anomaly by approximately 20% in the Sahara-Sahel region (10-25° N, 20° W-30° E) in both the early and mid-Holocene experiments compared to their fixed-vegetation counterparts. The primary vegetation-rainfall feedback identified here operates through surface latent heat flux anomalies by canopy evaporation and transpiration and their effect on the mid-tropospheric African easterly jet, whereas the effects of vegetation changes on surface albedo and local water recycling play a negligible role. Even though CCSM3-DGVM simulates a positive vegetation-precipitation feedback in the North African region, this feedback is not strong enough to produce multiple equilibrium climate-ecosystem states on a regional scale.

  10. North African vegetation-precipitation feedback in early and mid-Holocene climate simulations with CCSM3-DGVM

    NASA Astrophysics Data System (ADS)

    Rachmayani, R.; Prange, M.; Schulz, M.

    2014-05-01

    The present study analyses the sign, strength and working mechanism of the vegetation-precipitation feedback over North Africa in middle (6 ka BP) and early Holocene (9 ka BP) simulations using the comprehensive coupled climate-vegetation model CCSM3-DGVM. The coupled model simulates enhanced summer rainfall and a northward migration of the West African monsoon trough along with an expansion of the vegetation cover for the early and middle Holocene compared to pre-industrial. It is shown that dynamic vegetation enhances the orbitally triggered summer precipitation anomaly by approximately 20% in the Sahara/Sahel region (10° N-25° N, 20° W-30° E) in both the early and mid-Holocene experiments compared to their fixed-vegetation counterparts. The primary vegetation-rainfall feedback identified here operates through surface latent heat flux anomalies by canopy evaporation and transpiration and their effect on the mid-tropospheric African Easterly Jet, whereas the effects of vegetation changes on surface albedo and local water recycling play a negligible role. Even though CCSM3-DGVM simulates a positive vegetation-precipitation feedback in the North African region, this feedback is not strong enough to produce multiple equilibrium climate-ecosystem states on a regional scale.

  11. Carbon storage increases by major forest ecosystems in tropical South America since the Last Glacial Maximum and the early Holocene

    NASA Astrophysics Data System (ADS)

    Behling, Hermann

    2002-06-01

    To study the carbon storage increase of major forest ecosystems in tropical South America, such as Amazon rain forest, Atlantic rain forest, semideciduous forest, and Araucaria forest, the Last Glacial Maximum (LGM) and the early Holocene vegetation cover were reconstructed by pollen records. Marked forest expansion points to a significant total carbon storage increase by tropical forests in South America since the LGM and the early Holocene. The Amazon rain forest expansion, about 39% in area, had 28.3×10 9 tC (+20%), the highest carbon storage increase since the LGM. The expansion of the other much smaller forest areas also had a significant carbon storage increase since the LGM, the Atlantic rain forest with 4.9×10 9 tC (+55%), the semideciduous forest of eastern Brazil with 6.3×10 9 tC (+46%), the Araucaria forest with 3.4×10 9 tC (+108%). The estimated carbon storage increase of the four forest biomes since the early Holocene is also remarkable. The extensive deforestation in the last century strongly affected the carbon storage by tropical forests.

  12. Effects of melting ice sheets and orbital forcing on the early Holocene warming in extratropical Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Renssen, H.; Seppä, H.

    2015-11-01

    The early Holocene is a critical period for climate change, as it marked the final transition from the last deglaciation to the relatively warm and stable Holocene. It is characterized by a warming trend that has been registered in numerous proxy records. This climatic warming was accompanied by major adjustments in different climate components, including the decaying of ice sheets in cryosphere, the perturbation of circulation in the ocean, the expansion of vegetation (over the high latitude) in biosphere. Previous studies have analyzed the influence of the demise of the ice sheets and other forcings on climate system. However, the climate response to the forcings together with the internal feedbacks before 9 ka remains not fully comprehended. In this study, we therefore disentangle how these forcings contributed to climate change during the earliest part of Holocene (11.5-7 ka) by employing the LOVECLIM climate model for both equilibrium and transient experiments. The results of our equilibrium experiments for 11.5 ka reveal that the annual mean temperature at the onset of the Holocene was lower than in the preindustrial era in the Northern extratropics, except in Alaska. The magnitude of this cool anomaly varies regionally as a response to varying climate forcings and diverse mechanisms. In eastern N America and NW Europe the temperatures throughout the whole year were 2-5 °C lower than in the preindustrial control, reaching the maximum cooling as here the climate was strongly influenced by the cooling effects of the ice sheets. This cooling of the ice-sheet surface was caused both by the enhanced surface albedo and by the orography of the ice sheets. For Siberia, a small deviation (-0.5-1.5 °C) in summer temperature and 0.5-1.5 °C cooler annual climate compared to the preindustrial run were caused by the counteraction of the high albedo associated with the tundra vegetation which was more southward extended at 11.5 ka than in the preindustrial period and the

  13. Abrupt changes in early Holocene tropical sea surface temperature derived from coral records

    NASA Astrophysics Data System (ADS)

    Beck, J. Warren; Récy, Jacques; Taylor, Fred; Edwards, R. Lawrence; Cabioch, Guy

    1997-02-01

    For many high-latitude regions of the globe, it is now clear that the transition to modern climate following the Last Glacial Maximum was punctuated by a number of rapid and substantial climate oscillations1,2. In contrast, relatively little is known about how the tropics responded to the deglaciation, because few high-resolution records are available from lower latitudes. Corals have recently been shown to provide an important source of tropical climate records because they can be easily and accurately dated, using either 14C or 230Th, and because past sea surface temperatures can be recovered from the Sr/Ca ratios in coral skeletons. Here we use this technique to derive several early Holocene sea surface temperature records from a coral drill core recovered from Espiritu Santo, Vanuatu in the tropical southwest Pacific Ocean. These records indicate that sea surface temperatures in this region were depressed by as much as 6.5 °C below modern values at ~ 10,350 calendar years BP, but rose very abruptly during the following 1,500 years. This temperature increase lags the post-Younger Dryas increase observed in a coral record from the tropical Atlantic Ocean3by about 3,000 years, an unexpected phase-shift that may ultimately shed light on the mechanisms of deglacial climate change.

  14. Accelerating sea-level rise and coastal marsh stability: Insights from an early Holocene stratigraphic record

    NASA Astrophysics Data System (ADS)

    Li, Y.; Tornqvist, T. E.; Kohl, B.; Kuykendall, J.

    2011-12-01

    The increasingly recognized economic and ecologic value of coastal ecosystems and growing concerns about the fate of coastal wetlands in the face of anticipated accelerating sea-level rise in the next century provide the impetus to understand coastal marsh stability under climate warming conditions. This problem is strikingly exemplified by the Mississippi Delta, where wetland loss rates are among the highest in the world. Direct field observations of marsh responses to rising seas are helpful to understand marsh stability over short (annual to decadal) timescales. However, knowledge about marsh stability over longer timescales is largely lacking. Here we present an early Holocene stratigraphic and foraminiferal record from the Mississippi Delta to examine marsh responses to relative sea-level (RSL) rise at rates within the range of what is commonly predicted for the latter portion of the 21st century. While field monitoring of modern marshes has suggested that they may survive rates of RSL rise on the order of 1 cm/yr, our results show that marshes can persist only for up to a century, and often much shorter, with rates of RSL rise of ~0.7 cm/yr. We therefore conclude that the tipping point beyond which coastal marshes in this region become unsustainable may be reached earlier than what previous studies have suggested. These findings may be instrumental in long-term planning and mitigating impacts of anticipated sea-level rise on coastal ecosystems.

  15. Holocene Climate Change in Arctic Canada and Greenland

    NASA Astrophysics Data System (ADS)

    Briner, J. P.; McKay, N.; Axford, Y.; Bennike, O.; Bradley, R. S.; de Vernal, A.; Fisher, D. A.; Francus, P.; Fréchette, B.; Gajewski, K. J.; Jennings, A. E.; Kaufman, D. S.; Miller, G. H.; Rouston, C.; Wagner, B.

    2015-12-01

    We summarize the spatial and temporal pattern of climate change through the Holocene in Arctic Canada and Greenland. Our synthesis includes 47 records from a recent database of highly resolved, quantitative Holocene climate records from the Arctic (Sundqvist et al., 2014). We plot the temperature histories represented by the records in the database and compare them with paleoclimate information based on 53 additional records. Combined, the records include a variety of climate proxy types that range from ice (ice cores), land (lake and peat sequences) and marine (ocean sediment cores and coastal sediments) environments. The temperature-sensitive records indicate more consistent and earlier Holocene warmth in the north and east, and a more diffuse and later Holocene thermal maximum in the south and west. Principal components analysis reveals two dominant Holocene trends, one with early Holocene warmth followed by cooling in the middle Holocene, the other with a broader period of warmth in the middle Holocene followed by cooling in the late Holocene. The temperature decrease from the warmest to the coolest portions of the Holocene is 3.0±1.0°C on average (n=11 records). The Greenland Ice Sheet retracted to its minimum extent between 5 and 3 ka, consistent with many sites from around Greenland depicting a switch from warm to cool conditions around that time. The spatial pattern of temperature change through the Holocene was likely driven by the decrease in northern latitude summer insolation through the Holocene, the varied influence of waning ice sheets in the early Holocene, and the variable influx of Atlantic Water into the study region.

  16. Mapping the unseen: geoarchaeological prospection to the Stone Age heritage in the early Holocene delta deposits of the Rotterdam harbor area (the Netherlands)

    NASA Astrophysics Data System (ADS)

    Vos, Peter

    2013-04-01

    Mapping the unseen: geoarchaeological prospection to the Stone Age heritage in the early Holocene delta deposits of the Rotterdam harbor area (the Netherlands) Peter C. Vos1 & Dimitri Schiltmans2 1) Deltares, PO Box 85467, 3508 AL Utrecht, The Netherlands E-mail: peter.vos@deltares.nl 2) Bureau Oudheidkundig Onderzoek Rotterdam, Ceintuurbaan 213b, 3051 KC Rotterdam, The Netherlands E-mail: dea.schiltmans@Rotterdam.nl The Port of Rotterdam (PoR) is expanding the Rotterdam harbor area into the sea. A new channel, the Yangtze harbor, will be dug out to a depth of 20 m below sea level in order to connect the existing Maasvlakte harbor area with the new harbor area under construction. The upper part of the sediment, which was dredged out in order to create the new channel, consisted mainly of marine offshore sands. In the lower part, at a depth of about 17-22 m below the Dutch Ordnance Datum (NAP), Late Weichselian fluvial and aeolian sands and Early Holocene deltaic deposits of the Rhine - Meuse were present. From earlier dredging activities in the Maasvlakte area it was known that the Late Weichselian / Early Holocene deposits contain Late Paleolithic and Early Mesolithic artefacts. The deepening of the Yangtze harbor would affect the Late-Weichselian / Early Holocene deposits and destroy the archaeologically valuable objects in these layers. The aim of the archaeological Yangtze harbor project was to predict those locations where archaeological heritage from the Stone Age could be found. A geological-geogenetic approach was applied in order to determine the optimal palaeo-environmental locations for man to settle. A 3D palaeolandscape model was constructed of the harbor area; an area which was about 0.5 km wide and 3 km long. Given this palaeolandscape model, the potential archaeological sites were selected. The multidisciplinary prospection research was carried out in several steps. After each research step the strategy of the following research phase was determined

  17. Evidence for an early Holocene climate optimum in the Antarctic deep ice-core record

    SciTech Connect

    Ciais, P.; Lipenkov, V.; Nicolaiev, V.

    1992-01-01

    In the interpretation of the Antarctic deep ice-core data, little attention has been given to the Holocene part of the records. As far as translation of the stable isotope content in terms of temperature is concerned, this can be understood because expected temperature changes may be obscured by isotopic noise of various origins and because no {sup 14}C dating has yet been available for this type of sequence. In this article, we focus on the Dome C and Vostok cores and on a new 850-m long ice core drilled out at Komsomolskaia by the Soviet Antarctic Expeditions. These three sites are located in East Antarctica, on the Antarctic plateau, in a region essentially undisturbed by ice-flow conditions, so that their detailed intercomparison may allow us to identify the climatically significant isotopic signal. Our results compare well with the proximal records of Southern Hemisphere high latitudes and support the existence of a warmer {open_quotes}climatic optimum{close_quotes} between 10 and 6 ka y BP. Maximum temperatures are reached just at the end of the last deglaciation, which confirms previous observations at high latitudes, in contrast with later dates for the Atlantic and hypsithermal optima in Europe and North America. 60 refs., 6 figs.

  18. The sensitivity of Arctic sea ice production to shelf flooding during the early Holocene: a modelling study

    NASA Astrophysics Data System (ADS)

    Blaschek, M.; Renssen, H.

    2012-04-01

    During the last deglaciation, the global sea-level started rising, changing the coastlines from an early Holocene stand (40 m lower than today at approximately 10 kyr BP, Siddall et al., 2003) to modern day coastlines. Proxy evidence shows that this transgression occurred non-uniformly over the globe. For instance, Bauch et al. (2001) report for the Laptev Sea (Arctic Ocean), that the modern coastline was only established at 5 kyr BP after a fast transgression from the early Holocene, leading to a flooding of the extensive shelf area. This shelf area is presently regarded to be an important production zone of Arctic sea ice, playing an important role in the dynamics of sea ice in the Arctic, as well as its export to the Nordic Seas along the East Greenland Current (EGC). Through this sea ice export, changes in the Laptev Sea shelf area during the Holocene could potentially have had a substantial impact on the sea surface conditions of the EGC, and the Denmark Strait, which is known to be sensitive to sea ice. This is consistent with a rapid increase in sea ice export through the EGC around 5 kyr BP as reported by Jennings et al. (2002). In this study we investigate the impact of this Arctic shelf flooding on sea ice production in the Holocene, and on the climate of the Nordic Seas in the LOVECLIM1.2 global ocean-atmosphere-vegetation model. We present results of several experiments in which we study the sensitivity of Arctic sea ice production to various Arctic shelf areas under early Holocene conditions (9 kyr BP). We approach this by changing the land-sea mask to represent different lower-than-present sea-level coastlines. For example, we perform experiments with the Last Glacial Maximum (LGM) land-sea mask, representing a lowering of the sea-level by 120 m, while keeping other forcings at 9 kyr BP. A further step is to modify selected areas in the Arctic, such as the Laptev Sea area, to examine the importance of different areas. Our results help to explain long

  19. Environmental, depositional and cultural changes in the upper Pleistocene and early Holocene; the Cinglera del Capello Sequence (Capellades, Spain)

    USGS Publications Warehouse

    Vaquero, Manuel; Allue, Ethel; Bischoff, James L.; Burjachs, Francesc; Vallverdu, Josep

    2013-01-01

    The correlation between environmental and cultural changes is one of the primary archeological and paleoanthropological research topics. Analysis of ice and marine cores has yielded a high-resolution record of millennial-scale changes during the Late Pleistocene and Holocene eras. However, cultural changes are documented in low-resolution continental deposits; thus, their correlation with the millennial-scale climatic sequence is often difficult. In this paper, we present a rare occurrence in which a thick archeological sequence is associated with a high-resolution environmental record. The Cinglera del Capello is a tufa-draped cliff located in the northeastern Iberian Peninsula, 50 km west of Barcelona. This cliff harbors several rock-shelters with Late Pleistocene and Early Holocene deposits. Together, the deposits of four rock-shelters span from 7000 to 70,000 years ago and provide a high-resolution record of the environmental and human dynamics during this timespan. This record allows the correlation of the cultural and environmental changes. The multiproxy approach to the Cinglera evidence indicates that the main cultural stages of the Late Pleistocene and Early Holocene (Middle Paleolithic, Upper Paleolithic and Mesolithic) are associated with significant changes in the environmental and depositional contexts.

  20. Paleomagnetic constraints on the timing and duration of latest Pleistocene to early Holocene eruptions at Mount Shasta volcano, California, USA

    NASA Astrophysics Data System (ADS)

    Gardner, C. A.; Champion, D. E.; Christiansen, R. L.; Calvert, A. T.; Mosbrucker, A. R.

    2013-12-01

    Mount Shasta in northern California, USA, has among the highest late Pleistocene to early Holocene eruptive rates in the Cascades arc (Hildreth, 2007, USGS Prof Paper 1744). Paleomagnetic data from over 50 sites help constrain the timing and durations of these events. In late glacial times, lithic pyroclastic flows of unknown volume and age swept down all flanks of the volcano, followed, after a period of quiescence, by Shasta's largest known explosive event-- the pumiceous Red Banks tephra fall and pyroclastic flows at ~11 ka. The Red Banks tephra fall was closely followed by growth of the Shastina and Black Butte edifices on the west side of the volcano with the volume of the Shastina deposits alone estimated to be about 30 km3. Since cessation of activity at Shastina and Black Butte, a series of lava domes and flows built the summit Hotlum cone and inundated the N and E flanks of the volcano. Paleomagnetic secular-variation data show that the events described above have well-grouped and distinct remanence directions suggesting that individual pulses of activity occurred within short time intervals (days to decades), with periods of quiescence between them lasting longer than the eruptive activity. The total interval of time suggested by the movement of the magnetic field from pre-Red Banks through Hotlum activity is likely within 5-10 kyr. The pre-Redbanks pyroclastic flows exposed on at least three flanks of the volcano have essentially the same paleomagnetic direction of ~ D=350°, I=60° with a site mean α95of 1.8° (7/7 sites). The Red Banks eruptive products have a more easterly and shallower (~ D=2°, I=53°) remanent direction. The prominent Shastina cone on the NW flank of the volcano produced lava flows to the NW and SW of the cone and an apron of pyroclastic material to the west. Shastina pyroclastic flows and lava flows have a similar direction of ~ D=8°, I=56 (α95 from 15 sites is 1.4°) suggesting that the Shastina eruptive period lasted a

  1. Vegetation response to early holocene warming as an analog for current and future changes.

    PubMed

    Cole, Kenneth L

    2010-02-01

    Temperatures in southwestern North America are projected to increase 3.5-4 degrees C over the next 60-90 years. This will precipitate ecological shifts as the ranges of species change in response to new climates. During this shift, rapid-colonizing species should increase, whereas slow-colonizing species will at first decrease, but eventually become reestablished in their new range. This successional process has been estimated to require from 100 to over 300 years in small areas, under a stable climate, with a nearby seed source. How much longer will it require on a continental scale, under a changing climate, without a nearby seed source? I considered this question through an examination of the response of fossil plant assemblages from the Grand Canyon, Arizona, to the most recent rapid warming of similar magnitude that occurred at the start of the Holocene, 11,700 years ago. At that time, temperatures in southwestern North America increased about 4 degrees C over less than a century. Grand Canyon plant species responded at different rates to this warming climate. Early-successional species rapidly increased, whereas late-successional species decreased. This shift persisted throughout the next 2700 years. I found two earlier, less-extreme species shifts following rapid warming events around 14,700 and 16,800 years ago. Late-successional species predominated only after 4000 years or more of relatively stable temperature. These results suggest the potential magnitude, duration, and nature of future ecological changes and have implications for conservation plans, especially those incorporating equilibrium assumptions or reconstituting past conditions. When these concepts are extended to include the most rapid early-successional colonizers, they imply that the recent increases in invasive exotics may be only the most noticeable part of a new resurgence of early-successional vegetation. Additionally, my results challenge the reliability of models of future vegetation

  2. Charcoal reflectance reveals early holocene boreal deciduous forests burned at high intensities.

    PubMed

    Hudspith, Victoria A; Belcher, Claire M; Kelly, Ryan; Hu, Feng Sheng

    2015-01-01

    Wildfire size, frequency, and severity are increasing in the Alaskan boreal forest in response to climate warming. One of the potential impacts of this changing fire regime is the alteration of successional trajectories, from black spruce to mixed stands dominated by aspen, a vegetation composition not experienced since the early Holocene. Such changes in vegetation composition may consequently alter the intensity of fires, influencing fire feedbacks to the ecosystem. Paleorecords document past wildfire-vegetation dynamics and as such, are imperative for our understanding of how these ecosystems will respond to future climate warming. For the first time, we have used reflectance measurements of macroscopic charcoal particles (>180μm) from an Alaskan lake-sediment record to estimate ancient charring temperatures (termed pyrolysis intensity). We demonstrate that pyrolysis intensity increased markedly from an interval of birch tundra 11 ky ago (mean 1.52%Ro; 485°C), to the expansion of trees on the landscape ~10.5 ky ago, remaining high to the present (mean 3.54%Ro; 640°C) irrespective of stand composition. Despite differing flammabilities and adaptations to fire, the highest pyrolysis intensities derive from two intervals with distinct vegetation compositions. 1) the expansion of mixed aspen and spruce woodland at 10 cal. kyr BP, and 2) the establishment of black spruce, and the modern boreal forest at 4 cal. kyr BP. Based on our analysis, we infer that predicted expansion of deciduous trees into the boreal forest in the future could lead to high intensity, but low severity fires, potentially moderating future climate-fire feedbacks. PMID:25853712

  3. Charcoal Reflectance Reveals Early Holocene Boreal Deciduous Forests Burned at High Intensities

    PubMed Central

    Hudspith, Victoria A.; Belcher, Claire M.; Kelly, Ryan; Hu, Feng Sheng

    2015-01-01

    Wildfire size, frequency, and severity are increasing in the Alaskan boreal forest in response to climate warming. One of the potential impacts of this changing fire regime is the alteration of successional trajectories, from black spruce to mixed stands dominated by aspen, a vegetation composition not experienced since the early Holocene. Such changes in vegetation composition may consequently alter the intensity of fires, influencing fire feedbacks to the ecosystem. Paleorecords document past wildfire-vegetation dynamics and as such, are imperative for our understanding of how these ecosystems will respond to future climate warming. For the first time, we have used reflectance measurements of macroscopic charcoal particles (>180μm) from an Alaskan lake-sediment record to estimate ancient charring temperatures (termed pyrolysis intensity). We demonstrate that pyrolysis intensity increased markedly from an interval of birch tundra 11 ky ago (mean 1.52%Ro; 485°C), to the expansion of trees on the landscape ∼10.5 ky ago, remaining high to the present (mean 3.54%Ro; 640°C) irrespective of stand composition. Despite differing flammabilities and adaptations to fire, the highest pyrolysis intensities derive from two intervals with distinct vegetation compositions. 1) the expansion of mixed aspen and spruce woodland at 10 cal. kyr BP, and 2) the establishment of black spruce, and the modern boreal forest at 4 cal. kyr BP. Based on our analysis, we infer that predicted expansion of deciduous trees into the boreal forest in the future could lead to high intensity, but low severity fires, potentially moderating future climate-fire feedbacks. PMID:25853712

  4. Rapid early Holocene sea-level rise in Prydz Bay, East Antarctica

    NASA Astrophysics Data System (ADS)

    Hodgson, Dominic A.; Whitehouse, Pippa L.; De Cort, Gijs; Berg, Sonja; Verleyen, Elie; Tavernier, Ines; Roberts, Stephen J.; Vyverman, Wim; Sabbe, Koen; O'Brien, Philip

    2016-04-01

    Prydz Bay is one of the largest embayments on the East Antarctic coast and it is the discharge point for approximately 16% of the East Antarctic Ice Sheet. Geological constraints on the regional ice sheet history include evidence of past relative sea-level change at three sites; the Vestfold Hills, Rauer Islands and Larsemann Hills. In this paper we compile updated regional relative sea-level data from these sites. We compare these with a suite of relative sea-level predictions derived from glacial isostatic adjustment models and discuss the significance of departures between the models and the field evidence. The compiled geological data extend the relative sea-level curve for this region to 11,258 cal yr BP and include new constraints based on abandoned penguin colonies, new isolation basin data in the Vestfold Hills, validation of a submarine relative sea-level constraint in the Rauer Islands and recalibrated radiocarbon ages at all sites dating from 12,728 cal yr BP. The field data show rapid increases in rates of relative sea level rise of 12-48 mm/yr between 10,473 (or 9678) and 9411 cal yr BP in the Vestfold Hills and of 8.8 mm/yr between 8882 and 8563 cal yr BP in the Larsemann Hills. The relative sea-level high stands of ≥ 8.8 m from 9411 to after 7564 cal yr BP (Vestfold Hills) and ≥ 8 m at 8563 and 7066 cal yr BP (Larsemann Hills) are over-predicted by some of the glacial isostatic adjustment models considered here, suggesting that assumptions relating to the magnitude and timing of regional ice loss since the Last Glacial Maximum may need revising. In the Vestfold Hills and Rauer Islands the final deglacial sea-level rise was almost exactly cancelled out by local rebound between 9411 and 5967 cal yr BP and this was followed by a near exponential decay in relative sea-level. In the Larsemann Hills the sea-level data suggest that the rate of ice retreat in this region was not uniform throughout the Holocene. Swath bathymetric surveys of the benthic

  5. The Brazilian megamastofauna of the Pleistocene/Holocene transition and its relationship with the early human settlement of the continent

    NASA Astrophysics Data System (ADS)

    Hubbe, Alex; Hubbe, Mark; Neves, Walter A.

    2013-03-01

    One of the most intriguing questions regarding the Brazilian Late Quaternary extinct megafauna and Homo sapiens is to what extent they coexisted and how humans could have contributed to the former's extinction. The aim of this article is to review the chronological and archaeological evidences of their coexistence in Brazil and to evaluate the degree of direct interaction between them. Critical assessment of the Brazilian megafauna chronological data shows that several of the late Pleistoscene/early Holocene dates available so far cannot be considered reliable, but the few that do suggest that at least two species (Catonyx cuvieri, ground sloth; Smilodon populator, saber-toothed cat) survived until the beginning of the Holocene in Southeast Brazil. Archaeological data indicates that the first human groups arrived in Brazil and were inhabiting this region during the last millennia of the Pleistocene and, consequently, they coexisted with the extinct fauna in some parts of Brazil for at least one thousand years. There is no robust evidence favoring any kind of direct interaction between humans and megafauna prior to their extinction. To date, it is not possible to properly judge the indirect influence of humans (landscape transformation, introduction of predators, among others) in this extinction event. Intense and to some extent unique climate changes between the Last Glacial Maximum and the Holocene favors the interpretation that they had a major contribution to the megafauna extinction, although the scarcity of data impedes the proper testing of this hypothesis.

  6. Evolution of habitat and environment of deer during the Late-glacial and early Holocene: the case of red deer in French Jura.

    NASA Astrophysics Data System (ADS)

    Drucker, Dorothée.; Bridault, Anne; Hujic, Alisa; Bocherens, Hervé

    2010-05-01

    The Late-glacial and early Holocene transition is a key period of environmental changes in a context of to a global warming. In northwestern Europe, extensive studies have documented the vegetation and faunal recomposition with the replacement of the cold steppe-tundra ecosystem by the forested temperate ecosystem we can still observe. Paleoecological interest focused on the extinct large mammals species like the Mammoth. In comparison, little has been done to decipher the ecological adaptation of the surviving species, especially those that are still present in the very same region than in the past. A better knowledge of the impact of changing environmental conditions on the ecology would be useful to define the degree of selective pressure. Thus, we have studied the habitat and environment evolution of red deer (Cervus elaphus) during the Late-glacial and early Holocene using stable isotopes and radiocarbon investigations. The analyzed bone material was selected from archaeological sites in French Jura. Performing direct radiocarbon dating on the bone collagen of the selected remains solved the problem of possible chronological uncertainties of the stratigraphical record of the sites. The same bone collagen samples were used for stable isotope measurements. We investigated the relative abundances in 13C to examine changes in habitat closure (canopy effect), in 15N to decipher changes in pedogenic activities (soil maturation) of the animals dwelling, and in 18O to track changes in altitude and/or local temperatures of the occupied territories. The results demonstrate that the stable isotopic composition of red deer bone collagen can be a valuable and sensitive indicator of habitat use and environmental conditions. The associated direct dating allows us to reconstruct the chronology of ecological changes. The combined chronological and ecological results evidence local differences in red deer adaptation at a small geographical scale.

  7. Spatial and temporal variations and controlling factors of sediment accumulation in the Yangtze River estuary and its adjacent sea area in the Holocene, especially in the Early Holocene

    NASA Astrophysics Data System (ADS)

    Feng, Zhibing; Liu, Baohua; Zhao, Yuexia; Li, Xishuang; Jiang, Li; Si, Shaokun

    2016-08-01

    The sub-bottom and collected borehole data provide insight into the transport and accumulation processes of the Yangtze-derived sediment in the study area since ~11 kyr BP. Five seismic units were identified according to six major acoustic surfaces. The sedimentary strata consist of fluvial, estuarine and deltaic systems from the bottom up, characterized by two different trends in sediment accumulation rates, i.e., low-high-low, and high-low-high. On the inner shelf of the East China Sea, the terrain with trough and ridge was formed by the Early Holocene transgression strata (formed in ~10 to 12 kyr BP) scoured by the later rectilinear tidal current due to postglacial sea-level transgression, and the sharply protruding seismic units are interpreted to be bedrocks outcropping on the seafloor. An analysis of the sedimentary characteristics in the boreholes and such factors as difference in accumulation rates, and tectonic subsidence led us to conclude that the paleo-coastline was located not far away from and to the east of Core ZK09 at ~9 kyr BP, and the southern bank of the Yangtze River estuary was located to the south of Core ZK09. At ~9 kyr BP, the Yangtze-derived sediments were transported eastwards along the southern bank of the Yangtze River and the barrier due to the influence of the paleo-coastal current from the north, the direction of the Yangtze-derived sediment transport was split on the northeast of the Zhoushan archipelago, and the sediments covered the terrain with trough and ridge. During the high sea level period (7 kyr BP-present), the eastward migration of paleo-coastline had resulted in the increase in accumulation rate. We also conclude that the sharp increase in accumulation rate near the Yangtze River estuary after ~2 kyr BP was not primarily caused by human activities. The position shifts of the estuary caused by the paleo-coastline migration and sea level oscillations since the Holocene is the main cause controlling the Yangtze

  8. Spatial and temporal variations and controlling factors of sediment accumulation in the Yangtze River estuary and its adjacent sea area in the Holocene, especially in the Early Holocene

    NASA Astrophysics Data System (ADS)

    Feng, Zhibing; Liu, Baohua; Zhao, Yuexia; Li, Xishuang; Jiang, Li; Si, Shaokun

    2016-08-01

    The sub-bottom and collected borehole data provide insight into the transport and accumulation processes of the Yangtze-derived sediment in the study area since ~11 kyr BP. Five seismic units were identified according to six major acoustic surfaces. The sedimentary strata consist of fluvial, estuarine and deltaic systems from the bottom up, characterized by two different trends in sediment accumulation rates, i.e., low-high-low, and high-low-high. On the inner shelf of the East China Sea, the terrain with trough and ridge was formed by the Early Holocene transgression strata (formed in ~10 to 12 kyr BP) scoured by the later rectilinear tidal current due to postglacial sea-level transgression, and the sharply protruding seismic units are interpreted to be bedrocks outcropping on the seafloor. An analysis of the sedimentary characteristics in the boreholes and such factors as difference in accumulation rates, and tectonic subsidence led us to conclude that the paleo-coastline was located not far away from and to the east of Core ZK09 at ~9 kyr BP, and the southern bank of the Yangtze River estuary was located to the south of Core ZK09. At ~9 kyr, large volume of sediments was deposited in the northern isles of the Zhoushan archipelago and their adjacent bedrocks, forming a barrier effect on later sediment transport. During 7.5-8 kyr BP, the Yangtze-derived sediments were transported eastwards along the southern bank of the Yangtze River and the barrier due to the influence of the paleo-coastal current from the north, the direction of the Yangtze-derived sediment transport was split on the northeast of the Zhoushan archipelago, and the sediments covered the terrain with trough and ridge. During the high sea level period (7 kyr BP-present), the eastward migration of paleo-coastline had resulted in the increase in accumulation rate. We also conclude that the sharp increase in accumulation rate near the Yangtze River estuary after ~2 kyr BP was not primarily caused by

  9. Abundant C4 plants on the Tibetan Plateau during the Lateglacial and early Holocene

    NASA Astrophysics Data System (ADS)

    Thomas, Elizabeth K.; Huang, Yongsong; Morrill, Carrie; Zhao, Jiangtao; Wegener, Pamela; Clemens, Steven C.; Colman, Steven M.; Gao, Li

    2014-03-01

    Plants using the C4 (Hatch-Slack) photosynthetic pathway are key for global food production and account for ca 25% of terrestrial primary productivity, mostly in relatively warm, dry regions. The discovery of modern naturally-occurring C4 plant species at elevations up to 4500 m in Tibet and 3000 m in Africa and South America, however, suggests that C4 plants are present in a wider range of environments than previously thought. Environmental conditions on the Tibetan Plateau, including high irradiance, rainfall focused in summer, and saline soils, can favor C4 plants by offsetting the deleterious effects of low growing season temperature. We present evidence based on leaf wax carbon isotope ratios from Lake Qinghai that C4 plants accounted for 50% of terrestrial primary productivity on the northeastern Tibetan Plateau throughout the Lateglacial and early Holocene. Despite cold conditions, C4 plants flourished due to a combination of factors, including maximum summer insolation, pCO2 ca 250 ppmv, and sufficient summer precipitation. The modern C3 plant-dominated ecosystem around Lake Qinghai was established ca 6 thousand years ago as pCO2 increased and summer temperature and precipitation decreased. C4 plants were also intermittently abundant during the Last Glacial period; we propose that C4 plants contributed a significant portion of local primary productivity by colonizing the exposed, saline Qinghai Lake bed during low stands. Our results contrast with state-of-the-art ecosystem models that simulate <0.5% C4 plant abundance on the Tibetan Plateau in modern and past environments. The past abundance of C4 plants on the Tibetan Plateau suggests a wider temperature range for C4 plants than can be inferred from modern distributions and model simulations, and provides paleoecological evidence to support recent findings that C4 plant evolution and distribution was determined by a combination of climatic and environmental factors (temperature, irradiance, precipitation

  10. Lithostratigraphy and microfacies analyses of the Lateglacial and early Holocene sediment record from Lake Haemelsee (Germany)

    NASA Astrophysics Data System (ADS)

    Haliuc, Aritina; Brauer, Achim; Dulski, Peter; Engels, Stefan; Lane, Christine

    2015-04-01

    Annually laminated sediments are unique continental archives holding essential paleoenvironmental and paleoclimatic information providing the opportunity (i) to evaluate the climate variability at inter-annual to decadal scale and (ii) to construct independent and reliable chronologies. Lake Haemelsee in northern Germany (19.5 m a.s.l) is a key site for tracing high-resolution climatic and environmental evolution in W Europe because of its partly varved sediments. Here, we apply lithostratigraphical, geochemical and micro-facies analyses for the bottom sediments (~1700 to 1300 cm sediment depth) in order to investigate the driving mechanisms, timing and amplitude of Lateglacial abrupt climate changes to the onset of the Holocene warming. Detailed investigation includes micro-facies analyses on petrographic thin sections combined with high-resolution µ-XRF element scanning on both fresh sediment core halves (200 µm resolution) and impregnated sediment blocks (50µm resolution). Based on these analyses, the sediment composite profile (378 cm) has been divided in ten lithozones, each exhibiting different sedimentation modes in response to regional and local climatic and environmental changes. Micro-facies analyses revealed that sediments consist of organic matter, siderite, calcite, clay/silt and sand. The basal sediments consist of glacio-fluvial material. Fine laminations are best preserved in lithozone 5 (1522-1573 cm), where minima in element proxies for detrital sediments (Ti, K, Si) and maxima in Fe and Mn indicate the prevalence of anoxic meromictic conditions. Three different varve facies types were distinguished: i) the clastic-organic varves are specific for the intervals 1571-1573 cm and 1536-1541 cm; ii) calcite/siderite-organic varves appear between 1568-1571 and 1541-1545 cm; iii) the siderite-organic varves are characteristic for the middle of the lithozone 5 spanning from 1545-1568 cm. These changes in varve facies reflect the complex answer of

  11. Glacial inception during the late Holocene without carbon emissions from early agriculture: lessons from the stage-19 glacial inception

    NASA Astrophysics Data System (ADS)

    He, F.; Vavrus, S. J.; Kutzbach, J. E.; Ruddiman, W. F.; Tzedakis, P. C.

    2013-12-01

    Decreases in orbitally-forced summer insolation along with downward trends in greenhouse gases (GHG) have been precursors to incipient glaciation in the past. In the last several thousand years of the current interglacial, while summer insolation has decreased, there was a reversal of the downward trends in CH4 and CO2 concentration within the Holocene around 5,000 and 7,000 years ago. While the cause of this reversal remains unresolved, a leading hypothesis is Ruddiman's Early Anthropogenic Hypothesis that early agriculture, starting several thousand years ago, caused emissions of GHG large enough to reverse natural downward trends in CO2 and CH4 and kept Earth's climate anomalously warm, with the corollary that this may have prevented incipient glaciation during the late Holocene. Here we use the 1-degree, fully coupled Community Climate System Model version 4 (CCSM4) with climate forcings (orbital parameters and GHG) of a previous glacial inception to investigate whether glacial inception should have occurred prior to the industrial revolution if the concentrations of CH4 and CO2 had followed their natural downward trends throughout the Holocene. Tzedakis et al. [2012] show that for the previous eight interglacials, Stage 11 and Stage 19 are the best analogs of the Holocene because of their low eccentricities, and Stage 19 is a better analog than Stage 11 for the Holocene due to the in-phase relationship between obliquity and precession. Furthermore, their study suggests that 777 ka BP (777,000 years before present) is the timing of glacial inception for Stage 19, based on the occurrence of the earliest bipolar seesaw event associated with glacial melting. Not only do the orbital parameters at 777 ka BP resemble pre-industrial conditions, but the concentrations of CO2 at that time were essentially the same as their expected 'natural' pre-industrial values in the absence of anthropogenic greenhouse emissions. Our multi-millennial coupled CCSM4 simulations show

  12. Small-Mammal Data on Early and Middle Holocene Climates and Biotic Communities in the Bonneville Basin, USA

    NASA Astrophysics Data System (ADS)

    Schmitt, Dave N.; Madsen, David B.; Lupo, Karen D.

    2002-11-01

    Archaeological investigations in Camels Back Cave, western Utah, recovered a series of small-mammal bone assemblages from stratified deposits dating between ca. 12,000 and 500 14C yr B.P. The cave's early Holocene fauna includes a number of species adapted to montane or mesic habitats containing grasses and/or sagebrush (e.g., Lepus townsendii, Marmota flaviventris, Reithrodontomys megalotis, and Brachylagus idahoensis) which suggest that the region was relatively cool and moist until after 8800 14C yr B.P. Between ca. 8600 and 8100 14C yr B.P. these mammals became locally extinct, taxonomic diversity declined, and there was an increase in species well-adapted to xeric, low-elevation habitats, including ground squirrels, Lepus californicus and Neotoma lepida. The early small-mammal record from Camels Back Cave is similar to the 11,300-6000 14C yr B.P. mammalian sequence from Homestead Cave, northwestern Utah, and provides corroborative data on Bonneville Basin paleoenvironments and mammalian responses to middle Holocene desertification.

  13. Small-mammal data on early and middle Holocene climates and biotic communities in the Bonneville Basin, USA

    USGS Publications Warehouse

    Schmitt, D.N.; Madsen, D.B.; Lupo, K.D.

    2002-01-01

    Archaeological investigations in Camels Back Cave, western Utah, recovered a series of small-mammal bone assemblages from stratified deposits dating between ca. 12,000 and 500 14C yr B.P. The cave's early Holocene fauna includes a number of species adapted to montane or mesic habitats containing grasses and/or sagebrush (e.g., Lepus townsendii, Marmota flaviventris, Reithrodontomys megalotis, and Brachylagus idahoensis) which suggest that the region was relatively cool and moist until after 8800 14C yr B.P. Between ca. 8600 and 8100 14C yr B.P. these mammals became locally extinct, taxonomic diversity declined, and there was an increase in species well-adapted to xeric, low-elevation habitats, including ground squirrels, Lepus californicus and Neotoma lepida. The early small-mammal record from Camels Back Cave is similar to the 11,300-6000 14C yr B.P. mammalian sequence from Homestead Cave, northwestern Utah, and provides corroborative data on Bonneville Basin paleoenvironments and mammalian responses to middle Holocene desertification. ?? 2002 University of Washington.

  14. Early-Holocene warming in Beringia and its mediation by sea-level and vegetation changes

    NASA Astrophysics Data System (ADS)

    Bartlein, P. J.; Edwards, M. E.; Hostetler, S. W.; Shafer, S. L.; Anderson, P. M.; Brubaker, L. B.; Lozhkin, A. V.

    2015-09-01

    Arctic land-cover changes induced by recent global climate change (e.g., expansion of woody vegetation into tundra and effects of permafrost degradation) are expected to generate further feedbacks to the climate system. Past changes can be used to assess our understanding of feedback mechanisms through a combination of process modeling and paleo-observations. The subcontinental region of Beringia (northeastern Siberia, Alaska, and northwestern Canada) was largely ice-free at the peak of deglacial warming and experienced both major vegetation change and loss of permafrost when many arctic regions were still ice covered. The evolution of Beringian climate at this time was largely driven by global features, such as the amplified seasonal cycle of Northern Hemisphere insolation and changes in global ice volume and atmospheric composition, but changes in regional land-surface controls, such as the widespread development of thaw lakes, the replacement of tundra by deciduous forest or woodland, and the flooding of the Bering-Chukchi land bridge, were probably also important. We examined the sensitivity of Beringia's early Holocene climate to these regional-scale controls using a regional climate model (RegCM). Lateral and oceanic boundary conditions were provided by global climate simulations conducted using the GENESIS V2.01 atmospheric general circulation model (AGCM) with a mixed-layer ocean. We carried out two present-day simulations of regional climate - one with modern and one with 11 ka geography - plus another simulation for 6 ka. In addition, we performed five ~ 11 ka climate simulations, each driven by the same global AGCM boundary conditions: (i) 11 ka Control, which represents conditions just prior to the major transitions (exposed land bridge, no thaw lakes or wetlands, widespread tundra vegetation), (ii) sea-level rise, which employed present-day continental outlines, (iii) vegetation change, with deciduous needleleaf and deciduous broadleaf boreal

  15. Early-Holocene warming in Beringia and its mediation by sea-level and vegetation changes

    NASA Astrophysics Data System (ADS)

    Bartlein, P. J.; Edwards, M. E.; Hostetler, S. W.; Shafer, S. L.; Anderson, P. M.; Brubaker, L. B.; Lozhkin, A. V.

    2015-03-01

    Arctic land-cover changes (e.g., expansion of woody vegetation into tundra and effects of permafrost degradation) that have been induced by recent global climate change are expected to generate further feedbacks to the climate system. Past changes can be used to assess our understanding of feedback mechanisms through a combination of process modelling and paleo-observations. The sub-continental region of Beringia (Northeast Siberia, Alaska, and northwestern Canada) was largely ice-free at the peak of deglacial warming and experienced both major vegetation change and loss of permafrost when many arctic regions were still ice covered. The evolution of Beringian climate at this time was largely driven by global features, such as the amplified seasonal cycle of Northern Hemisphere insolation and changes in global ice volume and atmospheric composition, but changes in regional land-surface controls, such as the widespread development of thaw lakes, the replacement of tundra by deciduous forest or woodland, and the flooding of the Bering-Chukchi land bridge, were probably also important. We examined the sensitivity of Beringia's early Holocene climate to these regional-scale controls using a regional climate model (RegCM). Lateral and oceanic boundary conditions were provided by global climate simulations conducted using the GENESIS V2.01 atmospheric general circulation model (AGCM) with a mixed-layer ocean. We carried out two present day simulations of regional climate, one with modern and one with 11 ka geography, plus another simulation for 6 ka. In addition, we performed five ∼11 ka climate simulations, each driven by the same global AGCM boundary conditions: (i) 11 ka "Control", which represents conditions just prior to the major transitions (exposed land bridge, no thaw lakes or wetlands, widespread tundra vegetation), (ii) sea-level rise, which employed present day continental outlines, (iii) vegetation change, with deciduous needleleaf and deciduous broadleaf

  16. Early-Holocene warming in Beringia and its mediation by sea-level and vegetation changes

    USGS Publications Warehouse

    Bartlein, P.J.; Edwards, M.E.; Hostetler, Steven W.; Shafer, Sarah; Anderson, P.M.; Brubaker, L. B; Lozhkin, A. V

    2015-01-01

    Arctic land-cover changes induced by recent global climate change (e.g., expansion of woody vegetation into tundra and effects of permafrost degradation) are expected to generate further feedbacks to the climate system. Past changes can be used to assess our understanding of feedback mechanisms through a combination of process modeling and paleo-observations. The subcontinental region of Beringia (northeastern Siberia, Alaska, and northwestern Canada) was largely ice-free at the peak of deglacial warming and experienced both major vegetation change and loss of permafrost when many arctic regions were still ice covered. The evolution of Beringian climate at this time was largely driven by global features, such as the amplified seasonal cycle of Northern Hemisphere insolation and changes in global ice volume and atmospheric composition, but changes in regional land-surface controls, such as the widespread development of thaw lakes, the replacement of tundra by deciduous forest or woodland, and the flooding of the Bering–Chukchi land bridge, were probably also important. We examined the sensitivity of Beringia's early Holocene climate to these regional-scale controls using a regional climate model (RegCM). Lateral and oceanic boundary conditions were provided by global climate simulations conducted using the GENESIS V2.01 atmospheric general circulation model (AGCM) with a mixed-layer ocean. We carried out two present-day simulations of regional climate – one with modern and one with 11 ka geography – plus another simulation for 6 ka. In addition, we performed five ~ 11 ka climate simulations, each driven by the same global AGCM boundary conditions: (i) 11 ka Control, which represents conditions just prior to the major transitions (exposed land bridge, no thaw lakes or wetlands, widespread tundra vegetation), (ii) sea-level rise, which employed present-day continental outlines, (iii) vegetation change, with deciduous needleleaf and deciduous broadleaf boreal

  17. The coupled δ 13C-radiocarbon systematics of three Late Glacial/early Holocene speleothems; insights into soil and cave processes at climatic transitions

    NASA Astrophysics Data System (ADS)

    Rudzka, D.; McDermott, F.; Baldini, L. M.; Fleitmann, D.; Moreno, A.; Stoll, H.

    2011-08-01

    The coupled δ 13C-radiocarbon systematics of three European stalagmites deposited during the Late Glacial and early Holocene were investigated to understand better how the carbon isotope systematics of speleothems respond to climate transitions. The emphasis is on understanding how speleothems may record climate-driven changes in the proportions of biogenic (soil carbon) and limestone bedrock derived carbon. At two of the three sites, the combined δ 13C and 14C data argue against greater inputs of limestone carbon as the sole cause of the observed shift to higher δ 13C during the cold Younger Dryas. In these stalagmites (GAR-01 from La Garma cave, N. Spain and So-1 from Sofular cave, Turkey), the combined changes in δ 13C and initial 14C activities suggest enhanced decomposition of old stored, more recalcitrant, soil carbon at the onset of the warmer early Holocene. Alternative explanations involving gradual temporal changes between open- and closed-system behaviour during the Late Glacial are difficult to reconcile with observed changes in speleothem δ 13C and the growth rates. In contrast, a stalagmite from Pindal cave (N. Spain) indicates an abrupt change in carbon inputs linked to local hydrological and disequilibrium isotope fractionation effects, rather than climate change. For the first time, it is shown that while the initial 14C activities of all three stalagmites broadly follow the contemporaneous atmospheric 14C trends (the Younger Dryas atmospheric 14C anomaly can be clearly discerned), subtle changes in speleothem initial 14C activities are linked to climate-driven changes in soil carbon turnover at a climate transition.

  18. Holocene-aged sedimentary records of environmental changes and early agriculture in the lower Yangtze, China

    NASA Astrophysics Data System (ADS)

    Atahan, P.; Itzstein-Davey, F.; Taylor, D.; Dodson, J.; Qin, J.; Zheng, H.; Brooks, A.

    2008-03-01

    Sedimentary evidence from a total of 21 AMS 14C dates and 192 pollen and charcoal and 181 phytolith samples from three study sites in the archaeologically rich lower Yangtze in China provides an indication of interactions between early agriculturalists and generally highly dynamic environmental conditions. Results suggest that environmental changes influenced agricultural development, and attest the localised environmental impacts of incipient agriculture. Evidence of human activity, in the form of indicators of deforestation and possibly food production, is apparent by ca 7000 BP (early Neolithic or Majiabang). Clearer evidence of human activity dates to ca 4700 BP (late Neolithic or Liangzhu). Extensive, profound and apparently widespread human impacts do not appear until the Eastern Zhou (Iron Age, ca 2800-2200 BP), however, which in the lower Yangtze was a period associated with technological advances in agriculture, increased urbanisation and relatively stable hydro-geomorphological conditions.

  19. Late Holocene stratigraphy of the Tetimpa archaeological sites, northeast flank of Popocatepetl volcano, central Mexico

    USGS Publications Warehouse

    Panfil, M.S.; Gardner, T.W.; Hirth, K.G.

    1999-01-01

    Late Holocene (240 km2 on the east side of the volcano with >25 cm of tephra. Lavas from eruptive sequence I dammed drainage in the lowland area near the town of San Nicolas and caused local upstream deposition of as much as 30 m of lacustrine silts, clays, and sands. These lacustrine deposits record an eruptive hiatus for the Tetimpa area of about 750 14C yr: between ca. 2100 and ca. 1350 yr B.P., no major tephras were deposited in the Tetimpa area. In upland areas, this time period is represented by an unconformity and by Entisols formed in the top of pumice deposits and lavas from eruptive sequence I. Artifacts, agricultural furrows, and dwellings record human reoccupation of this surface. At the end of this hiatus, several lahars were deposited above the lacustrine sequence and locally above the Entisol in upland positions adjacent to streams. Between ca. 1350 and ca. 1200 yr B.P., tephras from eruptive sequence II buried these paleosols, occupation sites, lacustrine sediments, and lahars. Andesitic (~62% SiO2) pumice lapilli deposits in the Tetimpa area record three pumice-fall eruptions directed northeast and east of the crater. The first and smallest of these (maximum Tetimpa area thickness = 12 cm; >52 km2 covered by >25 cm) took place at ca. 1350 yr B.P. and was accompanied by pyroclastic surge events preserved in the Tetimpa area by charcoal, sand waves, and cross-stratified sand-sized tephra. At ca. 1200 yr B.P., the products of two Plinian-style events and additional pyroclastic surges reached the Tetimpa area. The largest of these tephra-fall events covered the Tetimpa area with 0.5-1 m of tephra and blanketed an area of >230 km2 with a thickness of >25 cm. The Tetimpa record confirms two of the four periods of explosive volcanism recognized by studies conducted around Popocatepetl in the past 30 yr. Eruptive sequence I corresponds to the explosive period between 2100 and 2500 yr B.P., and eruptive sequence II corresponds to the period between 900 and

  20. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 2 2012-01-01 2012-01-01 false Transfer of early site permit. 52.28 Section 52.28 Energy... Early Site Permits § 52.28 Transfer of early site permit. An application to transfer an early site permit will be processed under 10 CFR 50.80....

  1. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 2 2014-01-01 2014-01-01 false Transfer of early site permit. 52.28 Section 52.28 Energy... Early Site Permits § 52.28 Transfer of early site permit. An application to transfer an early site permit will be processed under 10 CFR 50.80....

  2. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 2 2013-01-01 2013-01-01 false Transfer of early site permit. 52.28 Section 52.28 Energy... Early Site Permits § 52.28 Transfer of early site permit. An application to transfer an early site permit will be processed under 10 CFR 50.80....

  3. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 2 2010-01-01 2010-01-01 false Transfer of early site permit. 52.28 Section 52.28 Energy... Early Site Permits § 52.28 Transfer of early site permit. An application to transfer an early site permit will be processed under 10 CFR 50.80....

  4. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 2 2011-01-01 2011-01-01 false Transfer of early site permit. 52.28 Section 52.28 Energy... Early Site Permits § 52.28 Transfer of early site permit. An application to transfer an early site permit will be processed under 10 CFR 50.80....

  5. Holocene temperature history of northern Iceland inferred from subfossil midges

    NASA Astrophysics Data System (ADS)

    Axford, Yarrow; Miller, Gifford H.; Geirsdóttir, Áslaug; Langdon, Peter G.

    2007-12-01

    The Holocene temperature history of Iceland is not well known, despite Iceland's climatically strategic location at the intersection of major surface currents in the high-latitude North Atlantic. Existing terrestrial records reveal spatially heterogeneous changes in Iceland's glacier extent, vegetation cover, and climate over the Holocene, but these records are temporally discontinuous and mostly qualitative. This paper presents the first quantitative estimates of temperatures throughout the entire Holocene on Iceland. Mean July temperatures are inferred based upon subfossil midge (Chironomidae) assemblages from three coastal lakes in northern Iceland. Midge data from each of the three lakes indicate broadly similar temperature trends, and suggest that the North Icelandic coast experienced relatively cool early Holocene summers and gradual warming throughout the Holocene until after 3 ka. This contrasts with many sites on Iceland and around the high-latitude Northern Hemisphere that experienced an early to mid-Holocene "thermal maximum" in response to enhanced summer insolation forcing. Our results suggest a heightened temperature gradient across Iceland in the early Holocene, with suppressed terrestrial temperatures along the northern coastal fringe, possibly as a result of sea surface conditions on the North Iceland shelf.

  6. Long-term stabilization of deep soil carbon by fire and burial during early Holocene climate change

    NASA Astrophysics Data System (ADS)

    Marin-Spiotta, Erika; Chaopricha, Nina T.; Plante, Alain F.; Diefendorf, Aaron F.; Mueller, Carsten W.; Grandy, A. Stuart; Mason, Joseph A.

    2014-06-01

    Buried soils contain large reservoirs of organic carbon at depths that are not typically included in regional and global soil carbon inventories. One such palaeosol, the Brady soil of southwestern Nebraska, USA, is buried under six metres of loess. The Brady soil developed at the land surface on the late-Pleistocene-aged Peoria Loess in a period of warmth and wetness during which dunefields and dust sources across the region were stabilized. Abrupt climate change in the early Holocene led to increased loess deposition that buried the soil. Here, we used spectroscopic and isotopic analyses to determine the composition and stability of organic carbon in the Brady soil. We identify high levels of black carbon, indicating extensive biomass burning. In addition, we found intact vascular plant lipids in soil organic matter with radiocarbon ages ranging from 10,500 to 12,400 cal yr BP, indicating decomposition was slowed by rapid burial at the start of the Holocene. We conclude that landscape disturbance caused by abrupt climate change, fire and the loss of vegetative cover contributed to deep carbon sequestration as the soil was quickly buried under accumulating loess. We suggest that terrestrial soil carbon storage in arid and semi-arid environments could undergo landscape-scale shifts in response to rising temperatures, increased fire activity or drought.

  7. Enhanced algal abundance in northwest Ontario (Canada) lakes during the warmer early-to mid-Holocene period

    NASA Astrophysics Data System (ADS)

    Karmakar, Moumita; Leavitt, Peter R.; Cumming, Brian F.

    2015-09-01

    This study investigates regional changes in primary producers in boreal head-water lakes during the warmer early-to-mid-Holocene (EMH) period, across the present-day boreal forest in northwest Ontario, a region that is adjacent to the prairie-forest ecotone. We quantified changes in algal abundance and composition over the Holocene period using pigments, spectrally-inferred chlorophyll a and diatom assemblages in well-dated sediment cores from three lakes. All three indicators showed a coherent pattern of enhanced primary producers in two of the study lakes (Gall Lake and Lake 239) during the EMH, whereas only diatom assemblages suggested higher levels of nutrients in Meekin Lake. Overall, this study supports a regional pattern of enhanced primary producers during the EMH, likely as a function of lower water-levels and warmer temperatures. Elevated concentrations of cyanobacterial pigments also occurred in two of the three lakes during the EMH, whereas pigments from purple-sulphur bacteria provide evidence of enhanced deep-water anoxia in one lake. These findings suggest that future climatic warming in boreal regions could include regional eutrophication and associated increases in cyanobacteria.

  8. Estimating the regional climate signal in a late Pleistocene and early Holocene lake-sediment δ18O record from Vermont, USA.

    NASA Astrophysics Data System (ADS)

    Mandl, Maximilian Benedict; Shuman, Bryan Nolan; Marsicek, Jeremiah; Grigg, Laurie

    2016-07-01

    We present a new oxygen isotope (δ18O) record from carbonate-rich lake sediments from central Vermont. The record from Twin Ponds spans from 13.5 cal ka BP (1950 AD) to present, but contains a 6 ka long hiatus starting shortly after 7.5 cal ka BP. We compare the record for ca. 13.5-7.5 cal ka BP with published δ18O data from the region after using a Bayesian approach to produce many possible chronologies for each site. Principal component analysis then identified chronologically-robust, multi-site oxygen isotope signals, including negative values during the Younger Dryas, but no significant deviations from the early Holocene mean of the regional records. However, differences among sites indicate significant trends that likely relate to interacting changes in the regional gradients of seasonal temperatures and precipitation as well as moisture sources, moisture pathways, and aridity that were controlled by large-scale climatic controls such as insolation, the progressive decline of the Laurentide Ice Sheet, and changes in oceanic circulation. Centennial shifts punctuate these trends at ca. 9.3 and 8.2 cal ka BP, and reveal that the local character of these short-lived features requires a detailed understanding of lake hydrology and regional isotopic gradients to yield reliable information for regional climate reconstructions.

  9. Early Site Permit Demonstration Program: Siting Guide, Site selection and evaluation criteria for an early site permit application. Revision 1

    SciTech Connect

    Not Available

    1993-03-24

    In August 1991, the Joint Contractors came to agreement with Sandia National Laboratories (SNL) and the Department of Energy (DOE) on a workscope for the cost-shared Early Site Permit Demonstration Program. One task within the scope was the development of a guide for site selection criteria and procedures. A generic Siting Guide his been prepared that is a roadmap and tool for applicants to use developing detailed siting plans for their specific region of the country. The guide presents three fundamental principles that, if used, ensure a high degree of success for an ESP applicant. First, the site selection process should take into consideration environmentally diverse site locations within a given region of interest. Second, the process should contain appropriate opportunities for input from the public. Third, the process should be applied so that it is clearly reasonable to an impartial observer, based on appropriately selected criteria, including criteria which demonstrate that the site can host an advanced light water reactor (ALWR). The Siting Guide provides for a systematic, comprehensive site selection process in which three basic types of criteria (exclusionary, avoidance, and suitability) are presented via a four-step procedure. It provides a check list of the criteria for each one of these steps. Criteria are applied qualitatively, as well as presented numerically, within the guide. The applicant should use the generic guide as an exhaustive checklist, customizing the guide to his individual situation.

  10. Early Site Permit Demonstration Program: Nuclear Power Plant Siting Database

    Energy Science and Technology Software Center (ESTSC)

    1994-01-28

    This database is a repository of comprehensive licensing and technical reviews of siting regulatory processes and acceptance criteria for advanced light water reactor (ALWR) nuclear power plants. The program is designed to be used by applicants for an early site permit or combined construction permit/operating license (10CFRR522, Subparts A and C) as input for the development of the application. The database is a complete, menu-driven, self-contained package that can search and sort the supplied datamore » by topic, keyword, or other input. The software is designed for operation on IBM compatible computers with DOS.« less

  11. Chironomid-inferred air temperatures from Lateglacial and Holocene sites in north-west Europe: progress and problems

    NASA Astrophysics Data System (ADS)

    Brooks, Stephen J.; Birks, H. J. B.

    2001-10-01

    Non-biting midges (Insecta: Diptera: Chironomidae) are now widely recognised as powerful biological proxies for inferring past climatic change. In this paper the response of chironomid assemblages to Lateglacial and Holocene climatic change from sites in Scotland and Norway is discussed. Analyses have shown that midge assemblages have responded to major and minor climatic fluctuations during the last 15,000 yr, such as the Aegelsee Oscillation, Gerzensee Oscillation and Younger Dryas in the Lateglacial, and the thermal optimum, "Little Ice Age" and cooling events at 8.2 and 2.0 cal ka BP in the Holocene. In an attempt to quantify these and other climatic fluctuations a chironomid-mean July air temperature inference model, based on a modern calibration set of 109 lakes in Norway and Svalbard, has been developed. The 3-component weighted averaging partial least squares inference model performs well with a root mean squared error of prediction of 0.90°C and a maximum bias of 0.59°C (both based on leave-one-out cross-validation) which is lower than chironomid-temperature inference models developed in Canada, Switzerland and Finland. However, while temperature-inference models perform well in the Lateglacial, the more subtle climatic changes of the Holocene are more difficult to reconstruct because the likely temperature changes are close to the limits of the prediction errors of the existing models. To address this problem, future work is required to refine and develop the calibration set by further improving taxonomic resolution, by adding more lakes to the calibration set and by investigating the influence of other environmental variables on chironomid distributions and abundances.

  12. Early Holocene change in atmospheric circulation in the Northern great plains: An upstream view of the 8.2 ka cold event

    USGS Publications Warehouse

    Dean, W.E.; Forester, R.M.; Bradbury, J.P.

    2002-01-01

    Elk Lake, in northwestern Minnesota, contains numerous proxy records of climatic and environmental change contained in varved sediments with annual resolution for the last 10,000 years. These proxies show that about 8200 calendar years ago (8.2 cal. ka; 7300 radiocarbon years) Elk Lake went from a well-stratified lake that was wind-protected in a boreal forest to a well-mixed lake in open prairie savanna receiving northwesterly wind-blown dust, probably from the dry floor of Lake Agassiz. This change in climate marks the initiation of the widely recognized mid-Holocene "altithermal" in central North America. The coincidence of this change with the so-called 8.2 cal. ka cold event, recognized in ice-core and other records from the circum-North Atlantic, and thought by some to be caused by catastrophic discharge of freshwater from proglacial lakes Agassiz and Ojibway, suggests that the two "events" might be related. Our interpretation of the Elk Lake proxy records, and of other records from less accurately dated sites, suggests that change in climate over North America was the result of a fundamental change in atmospheric circulation in response to marked changes in the relative proportions of land, water, and, especially, glacial ice in North America during the early Holocene. This change in circulation probably post-dates the final drainage of proglacial lakes along the southern margin of the Laurentide ice sheet, and may have produced a minor perturbation in climate over Greenland that resulted in a brief cold pulse detected in ice cores. ?? 2002 Elsevier Science Ltd. All rights reserved.

  13. Evidence for a stronger oxygen-minimum zone off central California during late Pleistocene to early Holocene.

    USGS Publications Warehouse

    Gardner, J.V.; Hemphill-Haley, E.

    1986-01-01

    Of 31 deep-sea cores collected along the central California continental slope, 18 have distinctly laminated sediment at depth. The cores with laminated facies are restricted to water depths between 508 and 1508 m. 14C dates yield an extrapolated age of 4700 B.P. for the top of the uppermost laminated unit. Comparisons of the diatom flora in the laminated couplets with diatom floras in a 13-month sediment-trap record suggest that the laminations are varvelike couplets of seasonal sedimentation. The laminated facies represent a period from the last global deglaciaton to early Holocene when the oxygen-minimum zone along the northeastern Pacific Ocean was stronger than at present. A stronger oxygen-minimum zone during this time is inferred to be the result of intensified upwelling. -from Authors

  14. A first Late Glacial and Early Holocene coupled 18O and 2H biomarker isotope record from Gemuendener Maar, Germany

    NASA Astrophysics Data System (ADS)

    Zech, Michael; Bromm, Tobias; Hepp, Johannes; Benesch, Marianne; Sirocko, Frank; Glaser, Bruno; Zech, Roland

    2015-04-01

    During the last years, we developed a method for compound-specific d18O analyses of hemicellulose-derived sugars from plants, soils and sediment archives (Zech and Glaser, 2009; Zech et al., 2014). The coupling of respective d18O sugar results with d2H alkane results from paleosol and sediment climate archives proved to be a valuable innovative approach towards quantitative paleoclimate reconstruction (Hepp et al., 2014; Zech et al., 2013). Here we present a first coupled d18O sugar and d2H alkane biomarker record obtained for Late Glacial and Early Holocene sediments from the Gemuendener Maar in the Eifel, Germany. The d18O sugar biomarker record resembles the d18O ice core records of Greenland. The coupling with the d2H alkane biomarker results allows drawing further more quantitative paleocimate information in terms of (i) paleohumidity and (ii) d18O of paleoprecipitation.

  15. Early- to Mid-Holocene environmental and climate changes in the southern Baltic lowland using XRF scanning data

    NASA Astrophysics Data System (ADS)

    Tjallingii, Rik; Ott, Florian; Dräger, Nadine; Kramkowski, Mateusz; Slowinski, Michal; Brauer, Achim

    2016-04-01

    The ICLEA project includes several annually laminated (varved) lake records from the southern Baltic lowlands for detailed climatic and environmental reconstructions. Continuous geochemical records have been obtained by XRF scanning and reveal the dominant depositional processes of the German lake Tiefer See and the Polish lakes Głęboczek, Czechowskie and Jelonek. Each lake record has been independently dated by means of varve counting, AMS 14C dating and tephrochronology. The unprecedented age control allows accurate age correlation of individual lake records even over large distances. The detailed stratigraphy is used in combination with micro-XRF core scanning records to link depositional variability with past environmental and climatic changes. However, in each lake the major sedimentological transitions are reflected by different geochemical elements due to the different depositional conditions. Here we present a statistical concept for XRF core scanning data to evaluate the timing and frequency of the most prominent sedimentological transitions of the Early to Mid Holocene. Preliminary results reveal that depositional conditions prevail over relatively long periods (102-103 yrs) between the Younger Dryas and ~6000 yrs. The sedimentological transitions during this period are associated to regional climatic changes in the southern Baltic lowlands during this period. After ~6000 yrs BP, depositional conditions vary at a much higher frequency (10-102 yrs), which are associated with a stronger local and lake internal environmental variability. Ongoing research focuses on a multi-proxy approach to further constrain possible links between depositional changes recorded in these varved lacustrine sediments with Early- to Mid-Holocene climatic and environmental variations. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis - ICLEA - of the Helmholtz Association.

  16. European bison as a refugee species? Evidence from isotopic data on Early Holocene bison and other large herbivores in northern Europe.

    PubMed

    Bocherens, Hervé; Hofman-Kamińska, Emilia; Drucker, Dorothée G; Schmölcke, Ulrich; Kowalczyk, Rafał

    2015-01-01

    According to the refugee species concept, increasing replacement of open steppe by forest cover after the last glacial period and human pressure had together forced European bison (Bison bonasus)--the largest extant terrestrial mammal of Europe--into forests as a refuge habitat. The consequent decreased fitness and population density led to the gradual extinction of the species. Understanding the pre-refugee ecology of the species may help its conservation management and ensure its long time survival. In view of this, we investigated the abundance of stable isotopes (δ13C and δ15N) in radiocarbon dated skeletal remains of European bison and other large herbivores--aurochs (Bos primigenius), moose (Alces alces), and reindeer (Rangifer tarandus)--from the Early Holocene of northern Europe to reconstruct their dietary habits and pattern of habitat use in conditions of low human influence. Carbon and nitrogen isotopic compositions in collagen of the ungulate species in northern central Europe during the Early Holocene showed significant differences in the habitat use and the diet of these herbivores. The values of the δ13C and δ15N isotopes reflected the use of open habitats by bison, with their diet intermediate between that of aurochs (grazer) and of moose (browser). Our results show that, despite the partial overlap in carbon and nitrogen isotopic values of some species, Early Holocene large ungulates avoided competition by selection of different habitats or different food sources within similar environments. Although Early Holocene bison and Late Pleistocene steppe bison utilized open habitats, their diets were significantly different, as reflected by their δ15N values. Additional isotopic analyses show that modern populations of European bison utilize much more forested habitats than Early Holocene bison, which supports the refugee status of the species. PMID:25671634

  17. European Bison as a Refugee Species? Evidence from Isotopic Data on Early Holocene Bison and Other Large Herbivores in Northern Europe

    PubMed Central

    Bocherens, Hervé; Hofman-Kamińska, Emilia; Drucker, Dorothée G.; Schmölcke, Ulrich; Kowalczyk, Rafał

    2015-01-01

    According to the refugee species concept, increasing replacement of open steppe by forest cover after the last glacial period and human pressure had together forced European bison (Bison bonasus)—the largest extant terrestrial mammal of Europe—into forests as a refuge habitat. The consequent decreased fitness and population density led to the gradual extinction of the species. Understanding the pre-refugee ecology of the species may help its conservation management and ensure its long time survival. In view of this, we investigated the abundance of stable isotopes (δ13C and δ15N) in radiocarbon dated skeletal remains of European bison and other large herbivores—aurochs (Bos primigenius), moose (Alces alces), and reindeer (Rangifer tarandus)—from the Early Holocene of northern Europe to reconstruct their dietary habits and pattern of habitat use in conditions of low human influence. Carbon and nitrogen isotopic compositions in collagen of the ungulate species in northern central Europe during the Early Holocene showed significant differences in the habitat use and the diet of these herbivores. The values of the δ13C and δ15N isotopes reflected the use of open habitats by bison, with their diet intermediate between that of aurochs (grazer) and of moose (browser). Our results show that, despite the partial overlap in carbon and nitrogen isotopic values of some species, Early Holocene large ungulates avoided competition by selection of different habitats or different food sources within similar environments. Although Early Holocene bison and Late Pleistocene steppe bison utilized open habitats, their diets were significantly different, as reflected by their δ15N values. Additional isotopic analyses show that modern populations of European bison utilize much more forested habitats than Early Holocene bison, which supports the refugee status of the species. PMID:25671634

  18. Late Pleistocene/Early Holocene Migratory Behavior of Ungulates Using Isotopic Analysis of Tooth Enamel and Its Effects on Forager Mobility.

    PubMed

    Pilaar Birch, Suzanne E; Miracle, Preston T; Stevens, Rhiannon E; O'Connell, Tamsin C

    2016-01-01

    Zooarchaeological and paleoecological investigations have traditionally been unable to reconstruct the ethology of herd animals, which likely had a significant influence on the mobility and subsistence strategies of prehistoric humans. In this paper, we reconstruct the migratory behavior of red deer (Cervus elaphus) and caprids at the Pleistocene-Holocene transition in the northeastern Adriatic region using stable oxygen isotope analysis of tooth enamel. The data show a significant change in δ18O values from the Pleistocene into the Holocene, as well as isotopic variation between taxa, the case study sites, and through time. We then discuss the implications of seasonal faunal availability as determining factors in human mobility patterns. PMID:27275784

  19. Late Pleistocene/Early Holocene Migratory Behavior of Ungulates Using Isotopic Analysis of Tooth Enamel and Its Effects on Forager Mobility

    PubMed Central

    Pilaar Birch, Suzanne E.; Miracle, Preston T.; Stevens, Rhiannon E.; O’Connell, Tamsin C.

    2016-01-01

    Zooarchaeological and paleoecological investigations have traditionally been unable to reconstruct the ethology of herd animals, which likely had a significant influence on the mobility and subsistence strategies of prehistoric humans. In this paper, we reconstruct the migratory behavior of red deer (Cervus elaphus) and caprids at the Pleistocene-Holocene transition in the northeastern Adriatic region using stable oxygen isotope analysis of tooth enamel. The data show a significant change in δ18O values from the Pleistocene into the Holocene, as well as isotopic variation between taxa, the case study sites, and through time. We then discuss the implications of seasonal faunal availability as determining factors in human mobility patterns. PMID:27275784

  20. Robust Patterns and Process Insight from Multi-Site, Multi-Proxy, Multi-Region Holocene Paleohydrologic Reconstructions

    NASA Astrophysics Data System (ADS)

    Shuman, B. N.; Serravezza, M.; Marsicek, J.

    2014-12-01

    Holocene moisture trends provide a useful context for historic hydrologic variations and potential future changes, and serve as key benchmarks for assessing paleoclimate dynamics. Many different approaches exist for paleohydrologic reconstruction, and comparisons offer an opportunity to validate key patterns and gain information based on differences. We consider multiple datasets from two mid-latitude regions of North America to evaluate centennial-to-millennial hydrologic variability during the Holocene. Comparisons of proxies at individual sites (i.e., pollen-inferred precipitation, reconstructed lake levels, hydrogen isotope ratios of biomarkers) and comparisons of proxies across sites in different hydrologic settings (i.e., closed vrs open lakes) provide insight into regional changes, while differences between the semi-arid (Wyoming) and humid (New England) regions reveal shifts in continental-scale moisture gradients. Pollen-inferred precipitation records were developed using the modern analog technique, which matches fossil pollen data to the climates of equivalent modern pollen assemblages. Lake moisture budgets were quantified in terms of mm/yr of precipitation minus evapotranspiration based on water-level histories systematically reconstructed from transects of sediment cores and geophysical data. Comparisons of the budgets for open and closed lakes, which have modern lake water isotopic values consistent with no or substantial evaporative losses respectively, were used to differentiate precipitation and evapotranspiration trends. Hydrogen isotopic values of aquatic versus terrestrial biomarkers, as well as comparisons with oxygen isotopic values of carbonate sediment, provide additional constrains on the magnitude of past evaporation trends that enrich the heavy isotope composition of lake water and thus aquatic substrates. In New England, pollen-inferred precipitation trends closely agree (Adj. R2 = 0.80) with replicated lake-level reconstructions, which

  1. Cyclic changes of Asian monsoon intensity during the early mid-Holocene from annually-laminated stalagmites, central China

    NASA Astrophysics Data System (ADS)

    Liu, Dianbing; Wang, Yongjin; Cheng, Hai; Edwards, R. L.; Kong, Xinggong

    2015-08-01

    Climate during the early Holocene was highly variable due to the complex interplay of external and internal forcing mechanisms. The relative importance for them on the Asian monsoon (AM) evolution yet remains to be resolved. Here we present two-to six-yr-resolution oxygen isotope (δ18O) records of five stalagmites, four of which are annually-laminated, from Qingtian Cave, central China, revealing detailed AM variability between 10.9 and 6.1 ka BP. Over the contemporaneous periods, the δ18O records agree well with each other at multi-decadal to centennial timescales. When pieced together with the previously published isotopic data from the same cave, the final δ18O record reveals detailed AM variability from the last deglaciation to the mid-Holocene, consistent with other cave records. The most striking feature of the δ18O record is the recurrence of centennial-scale oscillations, especially during the annually-counted period (8.8-6.1 ka BP). Cross-wavelet analyses between the δ18O record and solar proxies show strong coherence at 200-yr cycle, suggesting that solar output was actively involved as a primary contributor. The AM depression at 8.2 ka BP is indistinguishable in amplitude and pattern from a series of weak AM events after 8 ka BP. We speculate that these centennial-scale AM changes might be regulated by the positive feedbacks of oceanic/atmospheric interactions to the solar activity under the condition of the retreat of continental ice-sheets.

  2. New cosmogenic exposure dates from Sermilik Fjord, southeast Greenland document rapid early Holocene retreat of Helheim Glacier

    NASA Astrophysics Data System (ADS)

    Hughes, A. L.; Rainsley, E.; Murray, T.; Fogwill, C. J.

    2010-12-01

    Marine-terminating glaciers are currently the dominant route for mass loss from the Greenland Ice Sheet (GrIS). Over the last decade Helheim Glacier, in concert with the majority of marine-terminating glaciers of the southeast sector of the GrIS, has exhibited dramatic changes in speed, thinning and retreat rates. The Holocene retreat history of the outlet glaciers of southeast Greenland is, however, largely unconstrained. Without detailed records of retreat over longer-time scales recent changes cannot be placed in context, nor is there sufficient evidence to constrain ice sheet models for improved estimates of future sea level rise. We present the first direct chronological constraint on the retreat of ice from Sermilik Fjord in southeast Greenland, the former drainage route of Helheim Glacier. Samples spanning the full length of the 80 km fjord were collected from erratics and streamlined bedrock in July 2009-10 and analysed for terrestrial cosmogenic nuclide (10Be) dating. Overlapping exposure ages indicate rapid evacuation of ice from much of the fjord at around 10.5 ka BP. Such substantial early Holocene retreat coincides with establishment of the local marine limit at c. 11 ka BP (Long et al. 2008). The new dates extend and confirm results from a tributary valley close to the fjord mouth that placed retreat from the present day coastline at c. 11.5 ka (Roberts et al. 2008). References: Roberts, D.H., Long, A.J., Schnabel, C., Freeman, S. and Simpson, M.J.R. 2008. The deglacial history of southeast sector of the Greenland Ice Sheet during the Last Glacial Maximum. Quaternary Science Reviews, 27, 1505-1516. Long, A.J., Roberts, R.H., Simpson, M.J.R., Dawson, S., Milne, G.A. and Huybrechts, P. 2008. Late Weichselian relative sea-level changes and ice sheet history in southeast Greenland. Earth and Planetary Science Letters, 272, 8-18.

  3. History of late Holocene earthquakes at the Willow Creek site on the Nephi segment, Wasatch fault zone, Utah

    USGS Publications Warehouse

    Crone, Anthony J.; Personius, Stephen F.; Duross, Christopher; Machette, Michael N.; Mahan, Shannon

    2014-01-01

    This 43-page report presents new data from the Willow Creek site that provides well-defined and narrow bounds on the times of the three youngest earthquakes on the southern strand of the Nephi segment, Wasatch Fault zone, and refines the time of the youngest earthquake to about 200 years ago. This is the youngest surface rupture on the entire Wasatch fault zone, which occurred about a century or less before European settles arrived in Utah. Two trenches at the Willow Creek site exposed three scarp-derived colluvial wedges that are evidence of three paleoearthquakes. OxCal modeling of ages from Willow Creek indicate that paleoearthquake WC1 occurred at 0.2 ± 0.1 ka, WC2 occurred at 1.2 ± 0.1 ka, and WC3 occurred at 1.9 ± 0.6 ka. Stratigraphic constraints on the time of paleoearthquake WC4 are extremely poor, so OxCal modeling only yields a broadly constrained age of 4.7 ± 1.8 ka. Results from the Willow Creek site significantly refine the times of late Holocene earthquakes on the Southern strand of the Nephi segment, and this result, when combined with a reanalysis of the stratigraphic and chronologic information from previous investigations at North Creek and Red Canyon, yield a stronger basis of correlating individual earthquakes between all three sites.

  4. Late Wisconsin and early holocene glacial history, inner Ross Embayment, Antarctica

    NASA Technical Reports Server (NTRS)

    Denton, George H.; Bockheim, James G.; Wilson, Scott C.; Stuiver, Minze

    1991-01-01

    Lateral drift sheets of outlet glaciers that pass through the Transantarctic Mountains constrain past changes of the huge Ross ice drainage system of the Antarctic Ice Sheet. Drift stratigraphy suggests correlation of Reedy III (Reedy Glacier), Beardmore, Britannia (Hatherton/Darwin Glaciers), Ross Sea (McMurdo Sound), and younger (Terra Nova Bay) drifts; radiocarbon dates place the outer limits of Ross Sea drift in late Wisconsin time at 24,000 to 13,000 yr B.P. Outlet glacier profiles from these drifts constrain late Wisconsin ice sheet surface elevations. Within these constraint, two extreme late Wisconsin reconstructions are given of the Ross ice drainage system. Both show little elevation change of the polar plateau coincident with extensive ice shelf grounding along the inner Ross Embayment. However, in the central Ross Embayment, one reconstruction shows floating shelf ice, where as the other shows a grounded ice sheet. Massive late Wisconsin/Holocene recession of grounded ice from the western Ross Embayment, which was underway at 13,040 yr B.P. and completed by 6600 to 6020 yr B.P., was accompanied by little change in plateau ice levels inland of the Transantarctic Mountains.

  5. Climate impact on the Trzechowskie paleolake ecosystem during the Late Glacial and early Holocene in the light of multiproxy analysis

    NASA Astrophysics Data System (ADS)

    Słowiński, M.; Zawiska, I.; Noryśkiewicz, A. M.; Apolinarska, K.; Lutyńska, M.; Skubała, P.; Ott, F.; Wulf, S.; Brauer, A.

    2012-04-01

    The aim of the research was to reconstruct climate fluctuations during LG and early Holocene and their influence on the development of Trzechowskie paleolake. The paleolake is located in the eastern part of the Pomeranian Lakeland northern Poland (Tuchola Pinewoods). Its genesis is associated with the melting of a buried ice block. Trzechowskie paleolake is about 1.5 km long and the average width is 450 m (area ~ 28 ha). In our research we focused on the bottom sediments and multiproxy high resolution analysis were carryied out. We were able to reconstract local environment changes (plant and animal macrofossils, Cladocera, Diatom, Oribatidae mite, δ13C stable isotope, LOI, carbonate content - CaCO3), and the regional changes (pollen analysis and δ18O stable isotope). The chronology was based on palynological analysis, but also on the age-depth model, developed from five radiocarbon dates AMS14C. It clearly shows that the biogenic accumulation in the Trzechowskie paleolake started during Bølling-Allerød warmer period. The preliminary results of all analysis indicate that climate was the main factor responsible for Trzechowskie paleolake development during LG and early Holocane period. The environmental changes influenced sediment formation process and are marked in the lithology and chemistry but also had a strong effect on water plants, fito and zooplankton.

  6. Climate and vegetation changes during the Lateglacial and early-middle Holocene at Lake Ledro (southern Alps, Italy)

    NASA Astrophysics Data System (ADS)

    Joannin, S.; Vannière, B.; Galop, D.; Peyron, O.; Haas, J. N.; Gilli, A.; Chapron, E.; Wirth, S. B.; Anselmetti, F.; Desmet, M.; Magny, M.

    2013-04-01

    Adding to the on-going debate regarding vegetation recolonisation (more particularly the timing) in Europe and climate change since the Lateglacial, this study investigates a long sediment core (LL081) from Lake Ledro (652 m a.s.l., southern Alps, Italy). Environmental changes were reconstructed using multiproxy analysis (pollen-based vegetation and climate reconstruction, lake levels, magnetic susceptibility and X-ray fluorescence (XRF) measurements) recorded climate and land-use changes during the Lateglacial and early-middle Holocene. The well-dated and high-resolution pollen record of Lake Ledro is compared with vegetation records from the southern and northern Alps to trace the history of tree species distribution. An altitude-dependent progressive time delay of the first continuous occurrence of Abies (fir) and of the Larix (larch) development has been observed since the Lateglacial in the southern Alps. This pattern suggests that the mid-altitude Lake Ledro area was not a refuge and that trees originated from lowlands or hilly areas (e.g. Euganean Hills) in northern Italy. Preboreal oscillations (ca. 11 000 cal BP), Boreal oscillations (ca. 10 200, 9300 cal BP) and the 8.2 kyr cold event suggest a centennial-scale climate forcing in the studied area. Picea (spruce) expansion occurred preferentially around 10 200 and 8200 cal BP in the south-eastern Alps, and therefore reflects the long-lasting cumulative effects of successive boreal and the 8.2 kyr cold event. The extension of Abies is contemporaneous with the 8.2 kyr event, but its development in the southern Alps benefits from the wettest interval 8200-7300 cal BP evidenced in high lake levels, flood activity and pollen-based climate reconstructions. Since ca. 7500 cal BP, a weak signal of pollen-based anthropogenic activities suggest weak human impact. The period between ca. 5700 and ca. 4100 cal BP is considered as a transition period to colder and wetter conditions (particularly during summers) that

  7. Sub-Millennial Scale Climatic and Hydrologic Variability in the Gulf of Mexico during the Early Holocene

    NASA Astrophysics Data System (ADS)

    Lodico, J. M.; Flower, B. P.; Quinn, T. M.

    2005-12-01

    Sediment core MD02-2550 from Orca Basin located in the northern Gulf of Mexico (GOM) provides a high-resolution early Holocene record of climatic and hydrologic changes from ~10.5 to 7 thousand calendar years before present (ka). Paired analyses of Mg/Ca and δ18O on the planktonic foraminifer Globigerinoides ruber (white variety, 250-355 μm) sampled at ~ 20 year resolution were used to generate proxy records of sea surface temperature (SST) and the δ18O of seawater in the GOM (δ18OGOM). The Mg/Ca-SST record contains an overall ~(~1.5 °C warming trend from 10.5 to 7 ka that appears to track the intensity of the annual insolation cycle and six temperature oscillations (~0.5-2 °C), the frequency of which are consistent with those found in records of solar variability. The δ18OGOM record contains five ~0.5 ‰ oscillations from 10.5 to 7 ka that bear some resemblance to regional hydrologic records from Haiti and the Cariaco Basin, plus a ~ -0.8 ‰ excursion that may be associated with the "8.2 ka event" recorded in Greenland air temperatures. The δ18OGOM record, if interpreted as a salinity proxy, suggest large salinity fluctuations (> 2 ‰) reflecting changes in evaporation-precipitation (E-P) and Mississippi River input to the GOM. Percent Globigerinoides sacculifer records from three cores in the GOM exhibit remarkably coherent changes, suggesting episodic centennial-scale incursions of Caribbean waters. Spectral analysis of the Mg/Ca-SST and the δ18OGOM time series indicate that surface water conditions may be influenced by solar variations because they share significant periods of variability with atmospheric Δ14C near 700, 200, and 80-70 years. Our results add to the growing body of evidence that the sub-tropics were characterized by significant decadal to centennial-scale climatic and hydrologic variability during the early Holocene.

  8. Constant wind regimes during the Last Glacial Maximum and early Holocene: evidence from Little Llangothlin Lagoon, New England Tablelands, eastern Australia

    NASA Astrophysics Data System (ADS)

    Shulmeister, James; Kemp, Justine; Fitzsimmons, Kathryn E.; Gontz, Allen

    2016-07-01

    Here we present the results of a multi-proxy investigation - integrating geomorphology, ground-penetrating radar, and luminescence dating - of a high-elevation lunette and beach berm in northern New South Wales, eastern Australia. The lunette occurs on the eastern shore of Little Llangothlin Lagoon and provides evidence for a lake high stand combined with persistent westerly winds at the Last Glacial Maximum (LGM - centring on 21.5 ka) and during the early Holocene (ca. 9 and 6 ka). The reconstructed atmospheric circulation is similar to the present-day conditions, and we infer no significant changes in circulation at those times, as compared to the present day. Our results suggest that the Southern Hemisphere westerlies were minimally displaced in this sector of Australasia during the latter part of the last ice age. Our observations also support evidence for a more positive water balance at the LGM and early Holocene in this part of the Australian sub-tropics.

  9. Late-Holocene climate evolution at the WAIS Divide site, West Antarctica: Bubble number-density estimates

    USGS Publications Warehouse

    Fegyveresi, John M.; Alley, R.B.; Spencer, M.K.; Fitzpatrick, J.J.; Steig, E.J.; White, J.W.C.; McConnell, J.R.; Taylor, K.C.

    2011-01-01

    A surface cooling of ???1.7??C occurred over the ???two millennia prior to ???1700 CE at the West Antarctic ice sheet (WAIS) Divide site, based on trends in observed bubble number-density of samples from the WDC06A ice core, and on an independently constructed accumulation-rate history using annual-layer dating corrected for density variations and thinning from ice flow. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. Numberdensity is conserved in bubbly ice following pore close-off, allowing reconstruction of either paleotemperature or paleo-accumulation rate if the other is known. A quantitative late-Holocene paleoclimate reconstruction is presented for West Antarctica using data obtained from the WAIS Divide WDC06A ice core and a steady-state bubble number-density model. The resultant temperature history agrees closely with independent reconstructions based on stable-isotopic ratios of ice. The ???1.7??C cooling trend observed is consistent with a decrease in Antarctic summer duration from changing orbital obliquity, although it remains possible that elevation change at the site contributed part of the signal. Accumulation rate and temperature dropped together, broadly consistent with control by saturation vapor pressure.

  10. The PUFA-Enriched Fatty Acid Profiles of some Frozen Bison from the Early Holocene found in the Siberian Permafrost

    PubMed Central

    Guil-Guerrero, José L.; Rodríguez-García, Ignacio; Kirillova, Irina; Shidlovskiy, Fedor; Ramos-Bueno, Rebeca P.; Savvinov, Grigoryi; Tikhonov, Alexei

    2015-01-01

    Knowledge concerning the availability of n-3 fatty acids for humans in prehistoric times is highly relevant in order to draw useful conclusions on the healthy dietary habits for present-day humans. To this end, we have analysed fat from several frozen bison found in the permafrost of Siberia (Russia). A total of 3 bison were included in this study, all them very close to the early Holocene (8,000; 8,200; and 9,300 years BP). All samples were analysed by gas-liquid chromatography-mass spectrometry (GLC-MS) and GLC flame-ionization detection (GLC-FID). Fat samples from two bison showed two well-differenced areas, i.e. brown and white, the latter being saturated fatty acid enriched, corresponding to an intermediate stage of adipocere formation, while the brown ones yielded α-linolenic acid in higher percentages than found in present-day bison. As demonstrated in this work, the subcutaneous fat of bison consumed by Mesolithic hunters contained amounts of n-3 fatty acids in higher quantities than those found in current bison; thus, the subcutaneous fat of bison could have contributed to meet today's recommended daily intake of essential fatty acids for good health in the Mesolithic to a greater extent than previously thought. PMID:25604079

  11. Vegetation responses to the last glacial and early Holocene environmental changes in the northern Leizhou Peninsula, south China

    NASA Astrophysics Data System (ADS)

    Xue, Jibin; Zhong, Wei; Xie, Lichun; Unkel, Ingmar

    2015-09-01

    A well-dated palynological record spanning the interval ~ 40,500-7060 cal yr BP, retrieved from a peatland on the Leizhou Peninsula in south China, clearly shows regional vegetation and climate changes during the last glacial period. Pollen data showed that the study region was mainly covered by subtropical evergreen trees during Marine Isotope Stage 3 (MIS 3), indicating a subtropical climate with relatively high temperature and precipitation. During MIS 2, subtropical evergreen-deciduous forest with large areas of grassland occurred, implying cooler and drier conditions. Some tropical forest elements increased during the early Holocene, indicating a warm and wet trend. Several millennial-scale oscillations of the pollen records appeared to correlate with the cold anomalies in the North Atlantic region. Our records agree well with many records from other regions, but they are a bit different than that inferred from the neighboring Huguang Maar Lake. Furthermore, our results suggest that the vegetation surrounding Xialu peatland was strongly influenced by the migration of the intertropical convergence zone (ITCZ) and variability in the East Asian summer monsoon (EASM). Changes of atmospheric CO2 concentration (pCO2) levels may have also affected the long-term vegetation changes in the study region.

  12. 10 CFR 52.24 - Issuance of early site permit.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS... required by subpart A of 10 CFR part 51 have been made. (b) The early site permit must specify the site... construction permit or combined license. (c) The early site permit shall specify those 10 CFR 50.10...

  13. 10 CFR 52.24 - Issuance of early site permit.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS... required by subpart A of 10 CFR part 51 have been made. (b) The early site permit must specify the site... construction permit or combined license. (c) The early site permit shall specify those 10 CFR 50.10...

  14. 10 CFR 52.24 - Issuance of early site permit.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS... required by subpart A of 10 CFR part 51 have been made. (b) The early site permit must specify the site... construction permit or combined license. (c) The early site permit shall specify those 10 CFR 50.10...

  15. Paleoecological evidence for abrupt cold reversals during peak Holocene warmth on Baffin Island, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Axford, Yarrow; Briner, Jason P.; Miller, Gifford H.; Francis, Donna R.

    2009-03-01

    A continuous record of insect (Chironomidae) remains preserved in lake sediments is used to infer temperature changes at a small lake in Arctic Canada through the Holocene. Early Holocene summers at the study site were characterized by more thermophilous assemblages and warmer inferred temperatures than today, presumably in response to the positive anomaly in Northern Hemisphere summer insolation. Peak early Holocene warmth was interrupted by two cold reversals between 9.5 and 8 cal ka BP, during which multiple cold-stenothermous chironomid taxa appeared in the lake. The earlier reversal appears to correlate with widespread climate anomalies around 9.2 cal ka BP; the age of the younger reversal is equivocal but it may correlate with the 8.2 cal ka BP cold event documented elsewhere. Widespread, abrupt climate shifts in the early Holocene illustrate the susceptibility of the climate system to perturbations, even during periods of enhanced warmth in the Northern Hemisphere.

  16. Antarctic marine ice sheet retreat in the Ross Sea during the early Holocene

    NASA Astrophysics Data System (ADS)

    Mckay, R. M.; Golledge, N.; Naish, T.; Maas, S.; Levy, R. H.; Kuhn, G.; Lee, J. I.; Dunbar, G. B.

    2015-12-01

    Geological constraints on the timing of the retreat of the Last Glacial Maximum (LGM) Antarctic Ice Sheets provide critical insights into the processes controlling marine-based ice sheet stability. The over-deepened, seaward shallowing bathymetry of Antarctica's continental shelves is ideally configured to promote past, and potentially future, marine ice-sheet instability. The retreat history of the LGM ice sheet in the Ross Sea region is primarily constrained by C-14 ages on coastal beach ridges and relict penguin colonies along the Transantarctic Mountain front in the Western Ross Sea. Although these terrestrial sites offer more reliable dates than imprecise C-14 chronologies derived from bulk marine sediments, they may reflect retreat of local piedmont glaciers derived from East Antarctic outlet glaciers rather than representing the timing of retreat of the ice sheet in the central Ross Embayment. We present a sedimentary facies succession and foraminifera-based C-14 chronology from a core collected beneath the Ross Ice Shelf via a hot water drill access hole used for the ANDRILL Coulman High site survey. The site is to the east of Ross Island and distal from the coast, and yields a minimum age for glacial retreat that is approximately 1000 yrs earlier than suggested by coastal records along the nearby Victoria Land coast. We examine the implications of this constraint on the timing of ice sheet retreat in the context of model simulations and new multi-beam bathymetry data acquired in the Western Ross Sea. On the basis of these data we hypothesize that marine-based ice sheet retreat was triggered by oceanic forcings along most of the Pacific Ocean coastline of Antarctica simultaneously, but continued retreat in the Ross Sea occurred primarily as a consequence of marine ice sheet instability.

  17. Early Holocenic and Historic mtDNA African Signatures in the Iberian Peninsula: The Andalusian Region as a Paradigm

    PubMed Central

    Hernández, Candela L.; Soares, Pedro; Dugoujon, Jean M.; Novelletto, Andrea; Rodríguez, Juan N.; Rito, Teresa; Oliveira, Marisa; Melhaoui, Mohammed; Baali, Abdellatif; Pereira, Luisa; Calderón, Rosario

    2015-01-01

    Determining the timing, identity and direction of migrations in the Mediterranean Basin, the role of “migratory routes” in and among regions of Africa, Europe and Asia, and the effects of sex-specific behaviors of population movements have important implications for our understanding of the present human genetic diversity. A crucial component of the Mediterranean world is its westernmost region. Clear features of transcontinental ancient contacts between North African and Iberian populations surrounding the maritime region of Gibraltar Strait have been identified from archeological data. The attempt to discern origin and dates of migration between close geographically related regions has been a challenge in the field of uniparental-based population genetics. Mitochondrial DNA (mtDNA) studies have been focused on surveying the H1, H3 and V lineages when trying to ascertain north-south migrations, and U6 and L in the opposite direction, assuming that those lineages are good proxies for the ancestry of each side of the Mediterranean. To this end, in the present work we have screened entire mtDNA sequences belonging to U6, M1 and L haplogroups in Andalusians—from Huelva and Granada provinces—and Moroccan Berbers. We present here pioneer data and interpretations on the role of NW Africa and the Iberian Peninsula regarding the time of origin, number of founders and expansion directions of these specific markers. The estimated entrance of the North African U6 lineages into Iberia at 10 ky correlates well with other L African clades, indicating that U6 and some L lineages moved together from Africa to Iberia in the Early Holocene. Still, founder analysis highlights that the high sharing of lineages between North Africa and Iberia results from a complex process continued through time, impairing simplistic interpretations. In particular, our work supports the existence of an ancient, frequently denied, bridge connecting the Maghreb and Andalusia. PMID:26509580

  18. Analysis and Characterization of Organic Carbon in Early Holocene Wetland Paleosols using Ramped Pyrolysis 14C and Biomarkers

    NASA Astrophysics Data System (ADS)

    Vetter, L.; Schreiner, K. M.; Fernandez, A.; Rosenheim, B. E.; Tornqvist, T. E.

    2014-12-01

    Radiocarbon analyses are a key tool for quantifying the dynamics of carbon cycling and storage in both modern soils and Quaternary paleosols. Frequently, bulk 14C dates of paleosol organic carbon provide ages older than the time of soil burial, and 14C dates of geochemical fractions such as alkali and acid extracts (operationally defined as humic acids) can provide anomalously old ages when compared to coeval plant macrofossil dates. Ramped pyrolysis radiocarbon analysis of sedimentary organic material has been employed as a tool for investigating 14C age spectra in sediments with multiple organic carbon sources. Here we combine ramped pyrolysis 14C analysis and biomarker analysis (lignin-phenols and other cupric oxide products) to provide information on the source and diagenetic state of the paleosol organic carbon. We apply these techniques to immature early Holocene brackish wetland entisols from three sediment cores in southeastern Louisiana, along with overlying basal peats. Surprisingly, we find narrow 14C age spectra across all thermal aliquots from both paleosols and peats. The weighted bulk 14C ages from paleosols and overlying peats are within analytical error, and are comparable to independently analyzed 14C AMS dates from charcoal fragments and other plant macrofossils from each peat bed. Our results suggest high turnover rates of carbon in soils relative to input of exogenous carbon sources. These data raise broader questions about processes within the active soil and during pedogenesis and burial of paleosols that can effectively homogenize radiocarbon content in soils across the thermochemical spectrum. The concurrence of paleosol and peat 14C ages also suggests that, in the absence of peats with identifiable plant macrofossils, ramped pyrolysis 14C analyses of paleosols may be used to provide ages for sea-level indicators.

  19. Early Holocenic and Historic mtDNA African Signatures in the Iberian Peninsula: The Andalusian Region as a Paradigm.

    PubMed

    Hernández, Candela L; Soares, Pedro; Dugoujon, Jean M; Novelletto, Andrea; Rodríguez, Juan N; Rito, Teresa; Oliveira, Marisa; Melhaoui, Mohammed; Baali, Abdellatif; Pereira, Luisa; Calderón, Rosario

    2015-01-01

    Determining the timing, identity and direction of migrations in the Mediterranean Basin, the role of "migratory routes" in and among regions of Africa, Europe and Asia, and the effects of sex-specific behaviors of population movements have important implications for our understanding of the present human genetic diversity. A crucial component of the Mediterranean world is its westernmost region. Clear features of transcontinental ancient contacts between North African and Iberian populations surrounding the maritime region of Gibraltar Strait have been identified from archeological data. The attempt to discern origin and dates of migration between close geographically related regions has been a challenge in the field of uniparental-based population genetics. Mitochondrial DNA (mtDNA) studies have been focused on surveying the H1, H3 and V lineages when trying to ascertain north-south migrations, and U6 and L in the opposite direction, assuming that those lineages are good proxies for the ancestry of each side of the Mediterranean. To this end, in the present work we have screened entire mtDNA sequences belonging to U6, M1 and L haplogroups in Andalusians--from Huelva and Granada provinces--and Moroccan Berbers. We present here pioneer data and interpretations on the role of NW Africa and the Iberian Peninsula regarding the time of origin, number of founders and expansion directions of these specific markers. The estimated entrance of the North African U6 lineages into Iberia at 10 ky correlates well with other L African clades, indicating that U6 and some L lineages moved together from Africa to Iberia in the Early Holocene. Still, founder analysis highlights that the high sharing of lineages between North Africa and Iberia results from a complex process continued through time, impairing simplistic interpretations. In particular, our work supports the existence of an ancient, frequently denied, bridge connecting the Maghreb and Andalusia. PMID:26509580

  20. Testing a new temperature proxy using the late-glacial and early Holocene chironomid record of Rotsee, Switzerland

    NASA Astrophysics Data System (ADS)

    Verbruggen, F.; Heiri, O.; Reichart, G.-J.; Lotter, A. F.

    2009-04-01

    High concentrations of chironomid head capsules in late-glacial and early Holocene sediments from Rotsee, a lake in Central Switzerland, provide an excellent opportunity to study past climatic change and its effects on biota. Chironomids (non-biting midges) have been widely used as palaeoecological indicators of environmental change. In this study, we are testing the potential of these chitinous microfossils as a proxy to produce d18O records. Background information on the Rotsee record is provided by high-resolution records of organic matter and carbonate content. Periods of rapid climatic change are reflected by variations in stable oxygen isotope concentrations analyzed on bulk carbonates. For this record a high-resolution age model is based on wiggle-match dating using over 60 AMS radiocarbon dates on terrestrial plant macrofossils. In addition, changes in bulk carbonate d18O are correlated to similar variations observed in the Greenland ice core records to obtain an independent age control, which is additionally supported by pollen analysis and tephrochronology. Shifts in taxonomic composition of chironomid assemblages are apparent throughout the record. They coincide with changes in bulk carbonate d18O and are, therefore, thought to be related to climatic changes. Carbonate particles adhering to chironomid head capsules caused a noisy d18O record. After adequate carbonate removal a reliable d18O record based on chironomid head capsules was produced, which agrees well with the bulk carbonate record. The close agreement between variations in d18O of bulk carbonates and d18O in chironomid head capsules indicates that chironomid d18O can provide reliable reconstructions of past changes in lake water d18O, and indirectly climate, also in lakes where carbonates are absent. In future studies analyses of fossil chironomids can therefore produce reconstructions based on past assemblage changes and chironomid-temperature transfer functions, while at the same time

  1. Making Connections: Navigate the Internet for Early Childhood Sites.

    ERIC Educational Resources Information Center

    Larson, Jeanette

    1998-01-01

    Explains terminology related to the use of the Internet, describes how to find Web sites, and explains some of the sites designed for child-care professionals. The sites included are those related to health and nutrition, early-childhood and parenting organizations, children's television, reading and literature, sites for children, and regional…

  2. A High-Resolution Multi-Proxy Lake Sediment Record from Torfdalsvatn Suggests an Enhanced Temperature Gradient Between North and South Iceland During the Early Holocene

    NASA Astrophysics Data System (ADS)

    Florian, Christopher; Geirsdóttir, Áslaug; Miller, Gifford; Axford, Yarrow

    2015-04-01

    Torfdalsvatn (66° 3'41.73"N, 20°23'14.26"W) is a relatively small (0.4 km2) and shallow (z=5.8 m) lake on the Skagi Peninsula of northern Iceland approximately 0.5 km from the modern coastline. This location is ideal for comparison with the many marine core records from the North Iceland Shelf that record variability in the northern extent of the warm Irminger Current, one of the primary controls on regional climate. To develop a record of north Iceland Holocene terrestrial climate, we analyzed a 8.4 m sediment core at 15-30 year resolution from approximately 12 ka to present using multiple proxies including sedimentary pigments, organic carbon flux, carbon to nitrogen ratio and stable isotopes, as well as biogenic silica measured by Fourier Transform Infrared Spectroscopy (FTIR-S). Results show gradual warming during the early Holocene, with stable soil development and peak aquatic productivity not occurring until after 8 ka. Increased aquatic productivity and a stable terrestrial environment between 6 and 2 ka indicate peak Holocene warmth in this interval. Aquatic productivity abruptly decreases at 1.8 ka associated with an increase in minerogenic material from landscape destabilization in the catchment with the onset of late Holocene cooling. At 1ka, the proportion of terrestrially-derived organic matter deposited in the lake sediment increases, indicating significant destabilization of soil horizons due to continued cooling and potential human settlement. This record is in good agreement with composite north Iceland chironomid-inferred July air temperatures from Axford et al. (2007), which show peak summer temperatures occurring between approximately 5 and 2 ka. The time of peak warmth at Torfdalsvatn is associated with peak biogenic carbonate concentration in the marine core MD99-2269, indicating an influx of warm Irminger waters. This is in contrast with Holocene climate records obtained from lakes in south and west Iceland, implying that there was an

  3. Ecosystem response to Lateglacial and early Holocene climate oscillations in the Great Lakes region of North America

    NASA Astrophysics Data System (ADS)

    Yu, Zicheng

    2000-12-01

    Fossil pollen, plant macrofossils, gastropods, and elemental and stable-isotope geochemistry in a sediment core from Twiss Marl Pond, southern Ontario, Canada, were used to document climate oscillations during the Last Glacial-Interglacial transition (˜13,000-8500 14C BP) and understand their ecological effects. Chronology was provided by AMS 14C dating and regional pollen correlation. Oxygen isotope ( δ18O) results from mollusc shells, Chara-encrustations and bulk carbonates show a classic climate sequence of a warm Bølling-Allerød (BOA) at ˜12,500-10,920 14C BP, a cold Younger Dryas (YD) at 10,920-10,000 14C BP, the Holocene warming at 10,000 14C BP, a brief Preboreal Oscillation (PB) at 9650 14C BP, and a possible Gerzensee/Killarney (G/K) cooling shortly before 11,000 14C BP. Clay sediments at the base of the core contain high herb and shrub pollen and abundant arctic/alpine plant macrofossils, indicating a treeless tundra with severe soil erosion in watershed. During the BOA warm period, authigenic marl began to be deposited, and Picea woodland became established. The establishment of Picea woodland after peaks of δ18O and of carbonate accumulation suggests a lagged response of upland vegetation to BOA warming. In contrast, the occurrence of warmth-loving aquatics Najas flexilis and Typha latifolia at that time indicates sensitive responses of aquatic plants. The YD cooling is indicated by a ˜1.5‰ negative excursion in δ18O, an increase in minerogenic matter and higher concentrations of erosion-derived elements (Al, Na, K, Ti and V). Pollen data show no forest transformation in response to YD cooling, which is attributed to the insensitive nonecotonal vegetation at that time. However, more openings in the forests and increased erosion in the watershed are indicated by a slight increase of herb pollen, high concentrations of erosion elements and a Pediastrum peak. The onset of the Holocene was marked by an abrupt increase of 2‰ in δ18O and the

  4. Late Pleistocene to early Holocene lake level and paleoclimate insights from Stansbury Island, Bonneville basin, Utah

    NASA Astrophysics Data System (ADS)

    Patrickson, Shela J.; Sack, Dorothy; Brunelle, Andrea R.; Moser, Katrina A.

    2010-03-01

    This paper reports on recent multiproxy research conducted to determine the chronology of lake-level fluctuations recorded in sediments from a natural exposure at a classic Bonneville basin site. Grain size, carbonate percentage, magnetic susceptibility, amount of charcoal, and diatom community composition data were collected from the 16 lacustrine units that compose the 122 cm stratigraphic column in Stansbury Gulch. Trends observed in the measured proxies reveal several significant changes in lake level, and thereby effective moisture, over the approximately 14,500 yr time span represented by the sediments. Results (1) verify the effectiveness of the multiproxy approach in Bonneville basin studies, which has been underutilized in this region, (2) reaffirm the double nature of Lake Bonneville's Stansbury oscillation, (3) suggest a previously undocumented post-Gilbert highstand of Great Salt Lake, and (4) identify possible teleconnections between climate events in the Bonneville basin and events in the North Atlantic at about 20,500 and 7500 14C yr BP.

  5. Paleoecology of an early Holocene faunal and floral assemblage from the Dows Local Biota of north-central Iowa

    NASA Astrophysics Data System (ADS)

    Hudak, Curtis M.

    1984-05-01

    The faunas and floras from the Dows Local Biota provide an opportunity to compare Holocene taxa without a cultural bias. The Dows Local Biota is located in a large depression on the back side (north) of the Altamont I Moraine complex within the Des Moines Lobe. The Dows Silt Fauna/Flora ( = DSF; ca. 9380 ± 130 yr B.P.), one horizon of the Dows Local Biota, was collected for plant macrofossils, mollusks, and micromammals. DSF terrestrial gastropods are upland mesic forest dwellers although one species, Strobilops affinis, is characteristic of more xeric forests and may represent open woods. The aquatic gastropods reflect both permanent and periodic waters. DSF micromammals prefer an open, mesic, deciduous forest. The micromammal sympatry is restricted to a small area within the tension zone and deciduous forest belt of west-central Wisconsin. DSF plants are characteristic of upland forests, moist meadowlands or disturbed areas, and aquatic habitats. The DSF plant sympatry is large but restricted to the conifer-hardwood and deciduous forests along the Great Lakes-New England regions. Quantitative climatic data for the combined DSF sympatries suggest that Dows (ca. 9380 yr B.P.) was cooler than at present, and is nearly identical to that achieved by pollen analyses at the Cherokee Sewer-Lake West Okoboji sites (ca. 9000 yr B.P.) in northwest Iowa. Based on common habitat interpretations and sympatries, about 9380 yr B.P. north-central Iowa was cooler and moister than at present and was occupied by an open deciduous forest.

  6. The Holocene temperature conundrum

    PubMed Central

    Liu, Zhengyu; Zhu, Jiang; Rosenthal, Yair; Zhang, Xu; Otto-Bliesner, Bette L.; Timmermann, Axel; Smith, Robin S.; Lohmann, Gerrit; Zheng, Weipeng; Elison Timm, Oliver

    2014-01-01

    A recent temperature reconstruction of global annual temperature shows Early Holocene warmth followed by a cooling trend through the Middle to Late Holocene [Marcott SA, et al., 2013, Science 339(6124):1198–1201]. This global cooling is puzzling because it is opposite from the expected and simulated global warming trend due to the retreating ice sheets and rising atmospheric greenhouse gases. Our critical reexamination of this contradiction between the reconstructed cooling and the simulated warming points to potentially significant biases in both the seasonality of the proxy reconstruction and the climate sensitivity of current climate models. PMID:25114253

  7. Holocene paleoenviroments of northwest Iowa

    SciTech Connect

    Baker, R.G.; Bettis, E.A. III; Schwert, D.P.

    1996-05-01

    This paper presents the biotic, sedimentary, geomorphic, and climatic history of the upper part of the Roberts Creek Basin, northeastern Iowa for the late-glacial and Holocene, and compares these records with a C-O isotopic sequence from Coldwater Cave, 60 km northwest of Roberts Creek. the biotic record (pollen, vascular plant and bryophyte macrofossils, and insects) is preserved in floodplain alluvium that underlies three constructional surfaces separated by low scarps. Each surface is underlain by a lithologically and temporally distinct alluvial fill. The highest surface is underlain by the Gunder Member of the Deforest Formation, dating from 11,000 to 4000 yr BP; beneath the intermediate level is the Roberts Creek Member, dating from 4000 to 400 yr BP; and the lowest level is underlain by the Camp Creek Member, deposited during the last 380 yr. Pollen and plant macrofossils in the alluvial fill show that a typical late-glacial spruce forest was replaced by Quercus and Ulmus in the early Holocene. This early-to-middle Holocene forest became dominated by medic elements such as Acer saccharum, Tila americana, Ostyra virginiana, and Carpinus caroliniana as late as 5500 yr BP; in contrast, the closest sites to the west and north were at their warmest and driest were covered by prairie vegetation between 6500 and 5500 yr BP. After 5500 yr BP, the forest in the roberts Creek area was replaced by prairie, as indicated by a rich assemblage of plant macrofossils, although only Ambrosia and Poaceae became abundant in the pollen record. The return of Quercus {approx} 3000 BP (while nonarboreal pollen percentages remained relatively high) indicates the oak savanna prevailed with little change until settlement time. 83 refs., 17 figs., 5 tabs.

  8. Paired charcoal and tree-ring records of high-frequency Holocene fire from two New Mexico bog sites

    USGS Publications Warehouse

    Allen, C.D.; Anderson, R. Scott; Jass, R.B.; Toney, J.L.; Baisan, C.H.

    2008-01-01

    Two primary methods for reconstructing paleofire occurrence include dendrochronological dating of fire scars and stand ages from live or dead trees (extending back centuries into the past) and sedimentary records of charcoal particles from lakes and bogs, providing perspectives on fire history that can extend back for many thousands of years. Studies using both proxies have become more common in regions where lakes are present and fire frequencies are low, but are rare where high-frequency surface fires dominate and sedimentary deposits are primarily bogs and wetlands. Here we investigate sedimentary and fire-scar records of fire in two small watersheds in northern New Mexico, in settings recently characterised by relatively high-frequency fire where bogs and wetlands (Chihuahuen??os Bog and Alamo Bog) are more common than lakes. Our research demonstrates that: (1) essential features of the sedimentary charcoal record can be reproduced between multiple cores within a bog deposit; (2) evidence from both fire-scarred trees and charcoal deposits documents an anomalous lack of fire since ???1900, compared with the remainder of the Holocene; (3) sedimentary charcoal records probably underestimate the recurrence of fire events at these high-frequency fire sites; and (4) the sedimentary records from these bogs are complicated by factors such as burning and oxidation of these organic deposits, diversity of vegetation patterns within watersheds, and potential bioturbation by ungulates. We consider a suite of particular challenges in developing and interpreting fire histories from bog and wetland settings in the Southwest. The identification of these issues and constraints with interpretation of sedimentary charcoal fire records does not diminish their essential utility in assessing millennial-scale patterns of fire activity in this dry part of North America. ?? IAWF 2008.

  9. Formation of the modern current system in the East China Sea since the early Holocene and its relationship with sea level and the monsoon system

    NASA Astrophysics Data System (ADS)

    Zheng, Xufeng; Li, Anchun; Wan, Shiming; Jiang, Fuqing; Yin, Xueming; Lu, Jian

    2015-07-01

    The Okinawa Trough is a natural laboratory for the study of air-sea interaction and paleoenvironmental change. It has been demonstrated that present offshore export of particles in the bottom nepheloid layer occur primarily with downwelling from the northeast winter monsoon, which is inhibited by a transverse circulation pattern in summer. This current system was very different during the Last Glacial Maximum owing to low sea level (-120 m) and exposure of a large shelf area. We collected sediment core Oki01 from the middle Okinawa Trough during 2012 using R/V Kexue No. 1 to elucidate the timing and cause of the current system transition in the East China Sea. Clay mineral, dry density, and elemental (Ti, Ca) composition of core Oki01 was analyzed. The results indicate that clay minerals derived mainly from the Huanghe (Yellow) and the Changjiang (Yangtze) Rivers during 16.0-11.6 ka, and the modern current system in the East China Sea formed beginning in the early Holocene. Therefore, mixing of East China Sea continental shelf, Changjiang River and partially Taiwan Island sediment are the major contributors. The decrease of log(Ti/Ca) and alternating provenance since the early Holocene indicate less sediment from the East China in summer because of resistance of the modern current system, i.e., a "water barrier" and upwelling. Conversely, sediment delivery persists in winter and log(Ti/Ca) indicates the winter monsoon signal since the early Holocene. Our evidence also suggests that sediment from Taiwan Island could be transported by the Kuroshio Current to the middle Okinawa Trough, where it mingles with winter monsoon-induced export of sediment from the Changjiang River and East China Sea continental shelf. Although the present research advances understanding of the evolutionary history of paleoenvironmental change in the Okinawa Trough, more sediment cores should be retrieved over wide areas to construct a larger scenario.

  10. Holocene geomagnetic field variations from low latitude site: contribution from the Canary Islands

    NASA Astrophysics Data System (ADS)

    Kissel, Catherine; Laj, Carlo; Rodriguez-Gonzalez, Alejandro; Perez-Torrado, Francisco; Carrracedo, Juan-Carlos; Wandres, Camille

    2016-04-01

    Full geomagnetic vector information was retrieved from 37 lava flows (corresponding to 38 sites because one flow was sampled at two different localities) located in Tenerife and Gran Canaria (Canary Islands). Twenty-eight flows are dated between 1706 AD and about 13200 BC and one is historical. Eight other non-dated flows have stratigraphic links with the dated flows and at the end, our study allowed us to attribute to them archeomagnetic ages based on their paleomagnetic characteristics. Various mineralogical analyses were conducted, giving access to the nature and grain size of the magnetic minerals. Full stepwise (about 13 steps) thermal and AF demagnetizations were conducted on more than 400 samples to determine the paleomagnetic directions. The individual MAD values are on the average about 2° and the mean precision parameter at the flow scale (alpha95) is 4.2°. For paleointensities (PI), we performed the original Thellier and Thellier experiments with a success rate of about 65%, coupling it with the strict set of selection criteria PICRIT-03. The mean PIs at the flow level are based on 3 to 12 independent PI determinations except for one site in which only one reliable determination could be obtained. The obtained data are unique in this area over the 1000-14000 BC period and they are complementary to the dataset obtained in the Canary Islands for the last 500 years. Over the last 3 kyr, they indicate some variability in the local field intensity with a prominent PI peak centered around 600 BC and reaching 80 μT (VADM 16 x 10 ^22 Am ^2), documented by four different flows and associated to significantly easterly deviated declinations. The directional data are rather consistent with the most recent models proposed for that area but the obtained PI indicate that models largely underestimate the paleointensities. Combined with published data obtained from western Africa, Spain, Portugal, Morocco and the Azores within a 2000 km-radius around the Canary

  11. Holocene geomagnetic field intensity variations: Contribution from the low latitude Canary Islands site

    NASA Astrophysics Data System (ADS)

    Kissel, C.; Laj, C.; Rodriguez-Gonzalez, A.; Perez-Torrado, F.; Carracedo, J. C.; Wandres, C.

    2015-11-01

    New absolute paleomagnetic intensity (PI) are investigated from 37 lava flows located at Tenerife and Gran Canaria (Canary Islands). They complete previously published directional results from the same flows and therefore allow to examine the time variations of the full geomagnetic vector. Twenty-eight flows are radiocarbon dated between 1706 AD and about 13 200 BC and one is historical. Eight other flows are not dated but they have stratigraphic links with the dated flows and archeomagnetic ages had been attributed to them based on their paleomagnetic directions. Various mineralogical analyses were conducted, giving access to the nature of the magnetic minerals and to their grain size. We performed the original Thellier and Thellier paleointensity (PI) experiments with a success rate of about 65% coupling this experiment with the strict set of selection criteria PICRIT-03. The mean PIs at the flow level are based on 3 to 12 independent PI determinations except for one site in which only one reliable determination could be obtained. The data indicate some variability in the local field intensity with a prominent PI peak centered around 600 BC and reaching 80 μT (VADM 16 ×1022 Am2), documented for the first time in this region. Combined with the published data obtained from western Africa, Spain, Portugal, Morocco and the Azores within a 2000 km-radius around the Canary Islands, our data allow to construct a curve illustrating the Earth magnetic field intensity fluctuations for Southwestern Europe/Western Africa. This curve, compared to the one produced for the Middle East and one calculated for Central Asia shows that maximum intensity patches have a very large geographical extent. They do not yet appear clearly in the models of variations of the dipolar field intensity.

  12. Lake Store Finnsjøen - a key for understanding Lateglacial/early Holocene vegetation and ice sheet dynamics in the central Scandes Mountains

    NASA Astrophysics Data System (ADS)

    Paus, Aage; Boessenkool, Sanne; Brochmann, Christian; Epp, Laura Saskia; Fabel, Derek; Haflidason, Haflidi; Linge, Henriette

    2015-08-01

    The Lateglacial (LG) deglaciation and vegetation development in the Scandes Mountains has been debated for a century. Here we present new evidence from microfossils, radiocarbon dated plant macrofossils and sedimentary ancient DNA from laminated sediments in Lake Store Finnsjøen (1260 m a.s.l.) at Dovre, Central Norway. Combined with previous results from three other Dovre lakes, this allows for new interpretations of events during and immediately after the LG deglaciation. The Finnsjøen sediments present the first uninterrupted record of local vegetation development in the Scandes Mountains from the late Younger Dryas (YD), ca 12,000 cal years BP, to the early Holocene around 9700 cal years BP. The local vegetation in late YD/early Holocene was extremely sparse with pioneer herbs (e.g. Artemisia norvegica, Beckwithia, Campanula cf. uniflora, Koenigia, Oxyria, Papaver, Saxifraga spp.) and dwarf-shrubs (Betula nana, Salix including Salix polaris). From 11,300 cal years BP, local vegetation rapidly closed with dominant Dryas, Saxifraga spp., and Silene acaulis. From ca 10,700 cal years BP, open birch-forests with juniper, Empetrum nigrum and other dwarf-shrubs developed. Pine forests established within the area from 10,300 cal years BP. We identified the cold Preboreal Oscillation (PBO), not earlier described from pollen data in South Norway, around 11,400 cal years BP by a regional pollen signal. Distinct local vegetation changes were not detected until the post-PBO warming around 11,300 cal years BP. Apparently, the earlier warming at the YD/Holocene transition at 11,650 cal years BP was too weak and short-lived for vegetation closure at high altitudes at Dovre. For the first time, we demonstrate a regional glacier readvance and local ice cap formations during the YD in the Scandes Mountains. In two of the deep lakes with small catchments, YD glaciation blocked sedimentation without removing old sediments and caused a hiatus separating sediments of the ice

  13. Assessment of quantitative Holocene temperature reconstructions based on multiple proxies from the sediment record of Lake Loitsana, Sokli, NE Finland

    NASA Astrophysics Data System (ADS)

    Shala, S.; Helmens, K. F.; Luoto, T. P.; Salonen, J. S.; Väliranta, M.; Weckström, J.

    2014-12-01

    Four biotic proxies (pollen, plant macrofossils chironomids and diatoms) are employed to quantitatively reconstruct variations in mean July air temperatures (Tjul) at Lake Loitsana, NE Finland, during the Holocene. The aim: assessing the reliability of these temperature reconstructions and the timing of highest Tjul. The reconstructed Tjul values are evaluated in relation to local-scale/site-specific processes associated to the Holocene lake development at Loitsana, as these factors have been shown to significantly influence the fossil assemblages found in the Lake Loitsana sediments. Our study shows that the reconstructions are influenced, at least to some extent, by local factors, and highlights the benefit of using multi-proxy data in Holocene climate reconstructions. While pollen-based temperatures follow the classical trend of gradually increasing early Holocene Tjul with a mid-Holocene maximum July warming, the aquatic/wetland assemblages reconstruct higher than present Tjul already during the early Holocene, i.e. at the peak of summer insolation. We conclude that the relatively low early Holocene July temperatures recorded by the terrestrial pollen are the result of site-specific factors possibly combined with a delayed response of the terrestrial ecosystem compared to the aquatic ecosystem.

  14. The Hanford Site: An anthology of early histories

    SciTech Connect

    Gerber, M.S.

    1993-10-01

    This report discusses the following topics: Memories of War: Pearl Harbor and the Genesis of the Hanford Site; safety has always been promoted at the Hanford Site; women have an important place in Hanford Site history; the boom and bust cycle: A 50-year historical overview of the economic impacts of Hanford Site Operations on the Tri-Cities, Washington; Hanford`s early reactors were crucial to the sites`s history; T-Plant made chemical engineering history; the UO{sub 3} plant has a long history of service. PUREX Plant: the Hanford Site`s Historic Workhorse. PUREX Plant Waste Management was a complex challenge; and early Hanford Site codes and jargon.

  15. A revised Holocene geochronology for the Lower Mississippi Valley

    NASA Astrophysics Data System (ADS)

    Kesel, Richard H.

    2008-10-01

    Data from two locations, 1) a hydrodam site at the Old River Diversion structure south of the latitude of Natchez MS and 2) eight water wells from the latitude of Baton Rouge, LA, are the basis for a revised Holocene geochronology of the Lower Mississippi River floodplain based on 84 radiocarbon dates, analyses of 64 borehole logs, and 75 grain-size analyses, which together provide major insight into questions concerning the complexity of meander belt movement, the influence of the Younger Dryas on the lower valley, and on the Pleistocene/Holocene interface. Following the Younger Dryas, the early Holocene was characterized by periodic flooding and deposition separated by times of little or no deposition.

  16. Late Holocene climate and chemical change at high latitudes: case studies from contaminated sites in subarctic and arctic Canada

    NASA Astrophysics Data System (ADS)

    Galloway, Jennifer M.; Cooney, Darryl; Crann, Carley; Falck, Hendrik; Howell, Dana; Jamieson, Heather; Macumber, Andrew; Nasser, Nawaf; Palmer, Michael; Patterson, R. Timothy; Parsons, Michael; Roe, Helen M.; Sanei, Hamed; Spence, Christopher; Stavinga, Drew; Swindles, Graeme T.

    2015-04-01

    preserved in the lake sediment cores are informed by our characterization of sediments from over 50 lakes in the region. In the longer record obtained from the Giant Mine area we show that the concentration of aqua regia leached As increases prior to resource development and that concentrations are variable over millennia. Lowest concentrations of As in the ~3500 cal yr BP record are coincident with regional Neoglacial cooling. As concentrations begin to increase from concentrations near 100 ppm to over 1000 ppm in the lastest Holocene, coincident with a period of regional warming associated with the Medieval Warm period, although at this point we cannot rule out post-depositional remobilization of As from higher in the sediment column. Concentrations in excess of 10,000 ppm at the top of the sediment core are likely associated with anthropogenic release of this contaminant. At the more northern Courageous Lake site, the sediment record extends back about a hundred years, and reveals that concentrations of As in lake sediments prior to development of the area were about 40 ppm. Increases in As are associated with drilling and mine production but continued increases after 1999 may be due to remobilization of As due to on-going climate warming, recent remediation efforts, or vertical movement of this element in the sediment column.

  17. The early Holocene humid period in the Tayma palaeolake, NW Arabian Peninsula -- A high-resolution micro-facies and geochemical approach

    NASA Astrophysics Data System (ADS)

    Neugebauer, Ina; Plessen, Birgit; Dinies, Michèle; Engel, Max; Tjallingii, Rik; Brauer, Achim

    2016-04-01

    The Tayma palaeolake is a rare archive of the early Holocene humid period in northern Arabia (Dinies et al. 2015; Engel et al. 2012). Here we present a ca. 1 m thick and 500 years spanning annually laminated sediment section that was deposited in the centre of the former lake from ca. 8500 to 8000 calibrated years (cal. yrs) BP, as determined by AMS 14C dating of pollen concentrates (Dinies et al. 2015). High-resolution micro-facies analyses based on thin section microscopy, μXRF element scanning, δ18Ocarb and δ13Ccarb measurements on single carbonate laminae, as well as geochemical measurements on bulk samples for TOC, CaCO3, C/N ratio, δ18Ocarb, δ13Ccarb, δ13Corg and δ15N determination were performed in order to investigate the sedimentological and geochemical changes along the varved sequence in great detail. The finely laminated marl sediments are mainly composed of sub-mm thick laminae of endogenic aragonite, organic matter and diatoms, as well as occasional, often graded silt-clay layers. Following an early lake phase from ca. 8700 to 8500 cal. yrs BP characterized by coarsely laminated, presumably non-annual marl sediments that are rich in ostracods, three main varved phases can be distinguished within the investigated section: (1) aragonitic-organic varves from ca. 8500 to 8300 cal. yrs BP, (2) diatom-organic varves from ca. 8300 to 8100 cal. yrs BP that frequently include aragonite laminae and occasionally gastropod and ostracod shells, and (3) organic varves from ca. 8100 to 8000 cal. yrs BP with decreasing diatom and aragonite laminae and an increasing frequency of gypsum layers. After this period, gypsum becomes abundant and fine lamination appears only sporadically. In addition, we observe increasing trends of TOC, C/N and δ13Ccarb and decreasing δ18Ocarb during phase 1 and excess δ18Ocarb, δ13Ccarb and TOC values during phase 2, pointing towards the maximum lake productivity and increased seasonal precipitation. We interpret this

  18. Early- to Mid-Holocene hydroclimate shifts in tropical East Africa: the multi-proxy sediment record from Lake Rutundu, Kenya

    NASA Astrophysics Data System (ADS)

    De Cort, Gijs; Creutz, Mike; Barao, Lucia; Conley, Daniel; Haug, Gerald; Bodé, Samuel; Blaauw, Maarten; Engstrom, Dan; Verschuren, Dirk

    2015-04-01

    Following the generally arid conditions of the Last Glacial Maximum (LGM), a large part of the African continent experienced the Early to Mid-Holocene as a much more humid period than today. This so-called African Humid Period (AHP) coincided with high summertime insolation over the Northern Hemisphere subtropics, causing invigorated monsoons to create moist conditions over the northern parts of the continent. Similarly, equatorial and even low-latitude southeastern Africa experienced a wetter climate due to the post-glacial increase in atmospheric greenhouse gasses ultimately leading to altered Atlantic and Indian Ocean monsoon dynamics. The timing and abruptness of the onset and ending of the AHP in the different regions of the continent have been the subject of major discussion. On the other hand, shorter-lived climate fluctuations within the AHP have received much less attention, due to a scarcity of well-dated, high-resolution African paleoclimate records spanning the entire Holocene. In this study we used the sediment record of Lake Rutundu, a high-altitude crater lake on Mount Kenya, to document multidecadal to millennial-scale hydroclimate variability on the East African equator from the LGM to the present. A multiproxy approach combining core-surface scanning techniques (magnetic susceptibility, X-ray fluorescence) and close-interval bulk-sediment analyses (organic matter and biogenic Si content, grain size, organic δ15N and δ13C) resulted in a high-resolution record firmly anchored in time by an age model based on 210Pb dating and sixteen calibrated radiocarbon ages. This new Lake Rutundu hydroclimate record confirms that moister conditions following the LGM returned to East Africa ca.16 kyr BP, and it contains a perfectly timed Younger Dryas episode (12.8-11.5 kyr BP) of intermittent drought. We find that the Early- to Mid-Holocene period, which in African records is often described as uniformly wet, was in fact punctuated by three distinct, century

  19. Holocene fire dynamics in Fennoscandia

    NASA Astrophysics Data System (ADS)

    Clear, Jennifer; Seppa, Heikki; Kuosmanen, Niina; Molinari, Chiara; Lehsten, Veiko; Allen, Katherine; Bradshaw, Richard

    2015-04-01

    Prescribed burning is advocated in Fennoscandia to promote regeneration and to encourage biodiversity. This method of forest management is based on the perception that fire was much more frequent in the recent past and over a century of active fire suppression has created a boreal forest ecosystem almost free of natural fire. The absence of fire is thought to have contributed to the widespread dominance of Picea abies (Norway spruce) with the successive spruce dominated forest further reducing fire ignition potential. However, humans have altered the natural fire dynamics of Fennoscandia since the early- to mid-Holocene and disentangling the anthropogenic driven fire dynamics from the natural fire dynamics is challenging. Through palaeoecology and sedimentary charcoal deposits we are able to explore the Holocene spatial and temporal variability and changing drivers of fire and vegetation dynamics in Fennoscandia. At the local-scale, two forest hollow environments (<20km apart) were analysed for high resolution macroscopic charcoal and pollen analysis and their fire and vegetation history are compared to identify unique and mutual changes in disturbance history. Pollen derived quantitative reconstruction of vegetation at both the local- and regional-scale identifies local-scale disturbance dynamics and large-scale ecosystem response. Spatio-temporal heterogeneity and variability in biomass burning is explored throughout Fennoscandia and Denmark to identify the changing drives of fire dynamics throughout the Holocene. Palaeo-vegetation reconstructions are compared to process-based, climate driven dynamic vegetation model output to test the significance of fire frequency as a driver of vegetation composition and dynamics. Early-Holocene fire regimes in Fennoscandia are driven by natural climate variations and fuel availability. The establishment and spread of Norway spruce is driven by an increase in continentality of climate, but local natural and anthropogenic

  20. Holocene Palaeoenvironment on Kamchatka

    NASA Astrophysics Data System (ADS)

    Diekmann, B.; Chapligin, B.; Dirksen, O.; Dirksen, V.; Hoff, U.; Meyer, H.; Nazarova, L.

    2013-12-01

    In the scope of the German-Russian research programme KALMAR (Kurile-Kamchatka and Aleutean Marginal Sea-Island Arc Systems: Geodynamics and Climate Interaction in Space and Time), Holocene lake-sediment records and peat sections were investigated on Kamchatka, to infer environmental changes related to subpolar climatic processes in the northwestern Pacific realm at the eastern Siberian margin. The research strategy followed a multi-proxy approach, using fossil bioindicators (diatoms, chironomids, pollen), stable-isotope geochemistry of diatoms, sedimentology, tephra chronology, and radiocarbon dating. The oldest sediments were retrieved from former proglacial Lake Sokoch, situated at the treeline at 495 m a.s.l. in the Ganalsky Ridge of southern central Kamchatka. Lacustrine sediment records and peat sections of mid- to late Holocene age were recovered from the up to 25 m deep Two-Yurts Lake and neighbouring smaller forest lakes and onshore areas, situated in a former proglacial basin at 275 m a.s.l. at the eastern flank of the Central Kamchatka Mountain Chain, the Sredinny Ridge. Our findings give evidence of longterm climate changes that suggest the existence of a warm and humid early Holocene climate optimum between roughly 9.0 and 4.5 ka BP, followed by climate deterioration of the neoglacial epoch in concert with summer cooling, glacial advances, and enhanced continentality. Two strong cooling episodes punctuated late Holocene climate development between 4.5 and 3.5 ka BP and during the last millennium, marking the prelude of neoglacial cooling and the Little Ice Age. This general development of Holocene climate on Kamchatka is in line with environmental changes in the neighbouring Sea of Okhotsk, where the pattern of sea-ice dynamics is consistent with early Holocene warmth and Neoglacial climate cooling. While the marine records from the Sea of Okhotsk mainly reflect winter conditions, our findings show that summer climate on Kamchatka shows a similar trend

  1. Early evaluation of the suitability of the Yucca Mountain site

    SciTech Connect

    Younker, J.L.; Rickertsen, L.D.; Judd, B.R.

    1992-10-01

    This paper evaluates the technical suitability of Yucca Mountain, Nevada, as a potential site for a geologic repository for radioactive waste. The result of this early site-suitability evaluation is that, in the judgment of the Evaluation Team that conducted the evaluation, the evidence supports a conclusion that the site is not unsuitable. Additional information is needed, however, in specific areas before a recommendation on repository development can be made.

  2. Holocene and latest Pleistocene paleoseismology of the Salt Lake City segment of the Wasatch Fault Zone, Utah, at the Penrose Drive Trench Site

    USGS Publications Warehouse

    DuRoss, Christopher B.; Hylland, Michael D.; McDonald, Greg N.; Crone, Anthony J.; Personius, Stephen F.; Gold, Ryan D.; Mahan, Shannon

    2014-01-01

    The Salt Lake City segment (SLCS) of the Wasatch fault zone (WFZ) and the West Valley fault zone (WVFZ) compromise Holocene-active normal faults that bound a large intrabasin graben in northern Salt Lake Valley and have evidence of recurrent, large-magnitude (M ~6-7) surface-faulting earthquakes. However, at the time of this investigation, questions remained regarding the timing, displacement, and recurrence of latest Pleistocene and Holocene earthquakes on the northern SLCS and WVFZ , and whether the WVFZ is seismically independent of, or moves coseismically with, the SLCS. To improve paleoseismic data for the SLCS, we conducted a fault-trench investigation at the Penrose Drive site on the northern SLCS. Two trenches, excavated across an 11-m-high scarp near the northern end of the East Bench fault, exposed colluvial-wedge evidence for fize of six (preferred) surface-faulting earthquakes postdating to Provo-phase shoreline of Lake Bonneville (~14-18 ka). Radiocarbon and luminescence ages support earthquake times at 4.0 ± 0.5 ka (2σ) (PD1), 5.9 ± 0.7 ka (PD2), 7.5 ± 0.8 ka (PD3a), 9.7 ± 1.1 ka (PD3b), 10.9 ± 0.2 ka (PD4), and 12.1 ± 1.6 ka (PD5). At least one additional earthquake occurred at 16.5 ± 1.9 ka (PD6) based on an erosional unconformity that separates deformed Lake Bonneville sily and flat-lying Provo-phase shoreline gravel. Earthquakes PD5-PD1 yield latest Pleistocene (post-Provo) and Holocene mean recurrence intervals of ~1.6 kyr and ~1.7-1.9 kyr, respectively. Using 1.0-1.4 m of per-event vertical displacement for PD5-PD3b corroborate previously identified SLCS earthquakes at 4-10 ka. PD4 and PD5 occurred within an ~8-kyr *17-9 ka) time interval on the SLCS previously interpreted as a period of seismic quiescence, and PD6 possibly corresponds with a previously identified earthquake at ~17 ka (although both events have large timing uncertainties). The Penrose data, when combined with previous paleoseismic results, improve the latest Pleistocene-Holocene

  3. Climate Controls on Last Glacial Maximum to Early Holocene Glacier Extents in the Rwenzori Mountains, Uganda-Democratic Republic of Congo

    NASA Astrophysics Data System (ADS)

    Jackson, M. S.; Kelly, M. A.; Russell, J. M.; Baber, M.; Loomis, S. E.

    2014-12-01

    The climate controls on past and present tropical glacier fluctuations are unclear. Here we present a chronology of past glacial extents in the Rwenzori Mountains (~1ºN, 30ºE), on the border of Uganda and the Democratic Republic of Congo, and compare this with local and regional paleoclimate records to infer the climate controls on glaciation. The Rwenzori Mountains host the most extensive glacial system in Africa and are composed of quartz-rich bedrock lithologies, enabling 10Be dating. Our dataset includes thirty 10Be ages of boulders on moraines estimated to have been deposited between the end of the last glacial period and early Holocene time. In the Mubuku Valley, eight 10Be ages of large (~50-150 m relief) lateral moraines that extend down to ~2000 m asl indicate that deposition occurred at ~23.4 ka (n=4) and ~20.1 ka (n=4), contemporaneously with the global Last Glacial Maximum (LGM). Local and regional paleoclimate records document dry, cool conditions in East Africa during this time. Therefore, we suggest that cooler temperatures were a primary influence on the LGM glacial extents. Upvalley from these samples, six 10Be ages of boulders on moraines (between 3450 and 3720 m asl) document stillstands or readvances of glacier ice at ~14.3 ka (n=2), ~13.2 ka (n=2), and ~11.1 ka (n=2). In the nearby Nyagumasani Valley sixteen 10Be ages of boulders on moraines at similar elevations (3870-4020 m asl) indicate stillstands or readvances at ~11.5 ka (n=4), ~10.6 ka (n=4), and ~10.5 ka (n=4). Local and regional paleoclimate records indicate dry conditions during Younger Dryas time, wet conditions during early Holocene time, and no significant late-glacial temperature reversal. Thus, the relationship between glacier advance and climate conditions during late-glacial time remains enigmatic. We continue to develop the moraine chronology in order to improve our interpretations of climate controls on glacier fluctuations during late-glacial to early Holocene time.

  4. Refining the time span between the early Holocene Askja-S and Hässeldalen tephras through differential dating based on varve counting from Lake Czechowskie (N Poland)

    NASA Astrophysics Data System (ADS)

    Ott, Florian; Wulf, Sabine; Serb, Johanna; Słowiński, Michał; Obremska, Milena; Tjallingii, Rik; Błaszkiewicz, Mirosław; Brauer, Achim

    2016-04-01

    Robust chronological framework is a crucial necessity for palaeoclimate reconstructions and especially for synchronizing records to decipher climatic teleconnections. Volcanic ash deposits (tephra) provide isochronous time marker that can be utilized as tie-lines to synchronize sedimentary archives. Advances in the detection and identification of non-visible (crypto-) tephra, often transported over thousands of kilometers, also allows identifying ash deposits even in distal records. We report the first findings of co-existing early Holocene Hässeldalen and Askja-S cryptotephras in a varved sediment record in Lake Czechowskie (JC, northern Poland). Annual layer counting was used to establish a varve chronology and micro-facies analyses, relative calcium (Ca) and titanium (Ti) concentrations were used to decipher between lake productivity and detrital flux. Here we focus (i) on the determination of the time span between both tephras, (ii) revised age estimates for the Askja-S tephra and (iii) the sedimentological response of the JC record to the Preboreal Oscillation (PBO), a short lived cold episode during the early Holocene. A differential dating approach revealed a time span of 152 +11/-8 varve years counted in the JC sediment record between both tephras. Since the varved interval of the JC sediment record comprising the tephras is floating, we anchored the floating varve chronology to an absolute timescale by using the radiocarbon-dated Hässeldalen Tephra (11,380 ± 216 cal a BP, Wohlfarth et al, 2006). The resulting age for the Askja-S of 11,454-11,002 cal a BP is, even considering the rather large uncertainties, a few decades to several hundred years older than most radiocarbon based age models, but it supports the original age model from Hässseldala port. The sediment response to the PBO cold period is seen only in a slight decrease in titanium, a proxy for detrital matter flux. Varve micro-facies did not change during this interval confirming a weak impact

  5. Late Pleistocene and early Holocene change in the Weddell Sea: a new climate record from the Patriot Hills, Ellsworth Mountains, West Antarctica

    NASA Astrophysics Data System (ADS)

    Turney, C. S.; Fogwill, C. J.; Rubino, M.; Etheridge, D. M.; van Ommen, T. D.; Moy, A. D.; Curran, M. A.

    2014-12-01

    The transition from the late Pleistocene to the Holocene (30 000-5000 years ago) was a period of considerable climate variability, which has been associated with changes in deep water formation and the intensity of the Meridional Overturning Circulation. Although numerous records exist across the North Atlantic region, few Antarctic ice core records have been obtained from the south. Here we exploit the potential of upwelling ancient ice - so-called blue ice areas (BIAs) - from the Patriot Hills in the Ellsworth Mountains to derive the first deuterium isotope record (dD) from continental Antarctica south of the Weddell Sea. Gas analysis and glaciological considerations provide a first relative chronology and provide new constraints on ice sheet dynamics in the region. Inferred temperature trends from the Patriot Hills BIA and snow pit suggest changing climate influences during the transition between the last glacial period and Holocene. Our results demonstrate the considerable potential of the Patriot Hills site for reconstructing past climate change in the south Atlantic region.

  6. Coeval fluctuations of the Greenland ice sheet and a local glacier, central East Greenland, during late glacial and early Holocene time

    NASA Astrophysics Data System (ADS)

    Levy, Laura B.; Kelly, Meredith A.; Lowell, Thomas V.; Hall, Brenda L.; Howley, Jennifer A.; Smith, Colby A.

    2016-02-01

    We present a 10Be chronology of late glacial to early Holocene fluctuations of a Greenland ice sheet outlet glacier and the adjacent Milne Land ice cap in central East Greenland. Ages of boulders on bedrock indicate that both ice masses receded during the Younger Dryas (YD), likely due to rising summer temperatures. Since Greenland ice core records register cold mean annual temperatures throughout the YD, these ice-marginal data support climate conditions characterized by strong seasonality. The ice sheet outlet glacier and ice cap deposited inner Milne Land Stade moraines at 11.4 ± 0.8 ka and 11.4 ± 0.6 ka, respectively (mean moraine ages and 1σ uncertainties). Based on the coeval moraine ages, we suggest that both ice masses responded to climate conditions acting on the ice margins, specifically ablation. Moreover, the ice sheet responded sensitively (i.e., on the same time scale as a small ice cap) to climate conditions.

  7. Report of early site suitability evaluation of the potential repository site at Yucca Mountain, Nevada; Yucca Mountain Site Characterization Project

    SciTech Connect

    Younker, J.L.; Andrews, W.B.; Fasano, G.A.; Herrington, C.C.; Mattson, S.R.; Murray, R.C.; Ballou, L.B.; Revelli, M.A.; Ducharme, A.R.; Shephard, L.E.; Dudley, W.W.; Hoxie, D.T.; Herbst, R.J.; Patera, E.A.; Judd, B.R.; Docka, J.A.; Rickertsen, L.D.

    1992-01-01

    This study evaluated the technical suitability of Yucca Mountain, Nevada, as a potential site for a mined geologic repository for the permanent disposal of radioactive waste. The evaluation was conducted primarily to determine early in the site characterization program if there are any features or conditions at the site that indicate it is unsuitable for repository development. A secondary purpose was to determine the status of knowledge in the major technical areas that affect the suitability of the site. This early site suitability evaluation (ESSE) was conducted by a team of technical personnel at the request of the Associate Director of the US Department of Energy (DOE) Office of Geologic Disposal, a unit within the DOE`s Office of Civilian Radioactive Waste Management. The Yucca Mountain site has been the subject of such evaluations for over a decade. In 1983, the site was evaluated as part of a screening process to identify potentially acceptable sites. The site was evaluated in greater detail and found suitable for site characterization as part of the Environmental Assessment (EA) (DOE, 1986) required by the Nuclear Waste Policy Act of 1982 (NWPA). Additional site data were compiled during the preparation of the Site Characterization Plan (SCP) (DOE, 1988a). This early site suitability evaluation has considered information that was used in preparing both-documents, along with recent information obtained since the EA and SCP were published. This body of information is referred to in this report as ``current information`` or ``available evidence.``

  8. 10 CFR 52.24 - Issuance of early site permit.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS... the common defense and security or to the health and safety of the public; (7) Any significant adverse... required by subpart A of 10 CFR part 51 have been made. (b) The early site permit must specify the...

  9. Systematic Mn fluctuations in laminated rock varnish developed on coeval early Holocene flint artifacts along a climatic transect, Negev desert, Israel

    NASA Astrophysics Data System (ADS)

    Goldsmith, Yonaton; Enzel, Yehouda; Stein, Mordechai

    2012-11-01

    This study presents an assessment of the potential application of Mn content in rock varnish laminae as a paleoclimate indicator. To investigate the environmental controls on varnish formation, we determined Mn composition in rock varnish formed on flint artifacts produced during the earliest Holocene from eight coeval prehistoric sites in the Negev desert, Israel. These sites lie along a north-south annual rainfall transect ranging between 120 and 30 mm yr- 1. The varnish is ~ 100 times enriched in Mn relative to the content in the desert dust source material. Chemical profiles across the varnish display 4-6 distinct Mn peaks in all sampled sites, pointing to systematic fluctuations within the varnish along a wide range of environmental settings. The mean Mn contents in the various sites range between 10.7 and 15.6 at.%, yet within this range, the Mn content in the Negev varnish does not show a correlation with mean annual rainfall. As moisture is needed for Mn mobility, wetting cycles by dew or light rain, which are not adequately represented by the mean annual rainfall amounts but control the number of wetting-drying cycles may explain the variance within the results from the arid and hyperarid Negev varnish.

  10. Geology of the dry creek site; a stratified early man site in Interior Alaska

    USGS Publications Warehouse

    Thorson, R.M.; Hamilton, T.D.

    1977-01-01

    The Dry Creek archeologic site contains a stratified record of late Pleistocene human occupation in central Alaska. Four archeologic components occur within a sequence of multiple loess and sand layers which together form a 2-m cap above weathered glacial outwash. The two oldest components appear to be of late Pleistocene age and occur with the bones of extinct game animals. Geologic mapping, stratigraphic correlations, radiocarbon dating, and sediment analyses indicate that the basal loess units formed part of a widespread blanket that was associated with an arctic steppe environment and with stream aggradation during waning phases of the last major glaciation of the Alaska Range. These basal loess beds contain artifacts for which radiocarbon dates and typologic correlations suggest a time range of perhaps 12,000-9000 yr ago. A long subsequent episode of cultural sterility was associated with waning loess deposition and development of a cryoturbated tundra soil above shallow permafrost. Sand deposition from local source areas predominated during the middle and late Holocene, and buried Subarctic Brown Soils indicate that a forest fringe developed on bluff-edge sand sheets along Dry Creek. The youngest archeologic component, which is associated with the deepest forest soil, indicates intermittent human occupation of the site between about 4700 and 3400 14C yr BP. ?? 1977.

  11. Pollen and Phytolith Evidence for Rice Cultivation and Vegetation Change during the Mid-Late Holocene at the Jiangli Site, Suzhou, East China

    PubMed Central

    Qiu, Zhenwei; Jiang, Hongen; Ding, Jinlong; Hu, Yaowu; Shang, Xue

    2014-01-01

    Pollen and phytolith analyses were undertaken at the Jiangli site in Suzhou, Jiangsu Province, combined with studies on macrofossils by flotation. The concentration of pollen decreased while the percentage of Poaceae pollen in the profile increased from the late phase of the Majiabang Culture to the Songze Culture suggesting that human impact on the local environment intensified gradually. The discovery of rice paddy implies a relatively advanced rice cultivation in this area during the middle-late Holocene. Other than phytoliths, the high percentage of Oryza-type Poaceae pollen (larger than 40 µm) supplied robust evidence for the existence of rice paddy. Moreover, the fact that the farther from the rice paddy, the lower the concentration and percentage of Poaceae pollen also proves that the dispersal and deposition of pollen is inversely proportional to the distance. PMID:24466254

  12. Early Site Permit Demonstration Program: Recommendations for communication activities and public participation in the Early Site Permit Demonstration Program

    SciTech Connect

    Not Available

    1993-01-27

    On October 24, 1992, President Bush signed into law the National Energy Policy Act of 1992. The bill is a sweeping, comprehensive overhaul of the Nation`s energy laws, the first in more than a decade. Among other provisions, the National Energy Policy Act reforms the licensing process for new nuclear power plants by adopting a new approach developed by the US Nuclear Regulatory Commission (NRC) in 1989, and upheld in court in 1992. The NRC 10 CFR Part 52 rule is a three-step process that guarantees public participation at each step. The steps are: early site permit approval; standard design certifications; and, combined construction/operating licenses for nuclear power reactors. Licensing reform increases an organization`s ability to respond to future baseload electricity generation needs with less financial risk for ratepayers and the organization. Costly delays can be avoided because design, safety and siting issues will be resolved before a company starts to build a plant. Specifically, early site permit approval allows for site suitability and acceptability issues to be addressed prior to an organization`s commitment to build a plant. Responsibility for site-specific activities, including communications and public participation, rests with those organizations selected to try out early site approval. This plan has been prepared to assist those companies (referred to as sponsoring organizations) in planning their communications and public involvement programs. It provides research findings, information and recommendations to be used by organizations as a resource and starting point in developing their own plans.

  13. The influence of high-latitude flux lobes on the Holocene paleomagnetic record of IODP Site U1305 and the northern North Atlantic

    NASA Astrophysics Data System (ADS)

    Stoner, Joseph S.; Channell, James E. T.; Mazaud, Alain; Strano, Sarah E.; Xuan, Chuang

    2013-10-01

    Paleomagnetic analysis and radiocarbon dating of an expanded Holocene deep-sea sediment sequence recovered by Integrated Ocean Drilling Program (IODP) Expedition 303 from Labrador Sea Site U1305 (Lat.: 57°28.5 N, Long.: 48°31.8 W, water depth 3459 m) provides insights into mechanisms that drive both paleomagnetic secular variation (PSV) and magnetization acquisition in deep-sea sediments. Seventeen radiocarbon dates on planktonic foraminifera define postglacial (ca. 8 ka) sedimentation rates as ranging from 35 to > 90 cm/kyr. Alternating field (AF) demagnetization of u-channel samples show that these homogeneous sediments preserve a strong, stable, and consistently well-defined component magnetization. Normalized remanence records pass reliability criteria for relative paleointensity (RPI) estimates. Assuming that the age of magnetization is most accurately defined by well dated PSV records with the highest sedimentation rates, allows us to estimate and correct for temporal offsets at Site U1305 interpreted to result from postdepositional remanence acquisition at a depth of ˜20 cm. Comparisons indicate that the northern North Atlantic PSV and RPI records are more consistent with European than North American records, and the evolution of virtual geomagnetic poles (VGP) are temporally and longitudinally similar to global reconstructions, though with much larger latitudinal variation. The largest deviations from a geocentric axial dipole (GAD) are observed during times of the highest intensities, in contrast to the usual assumption. These observations are consistent with the idea that PSV in the North Atlantic and elsewhere during the Holocene results from temporal oscillations of high-latitude flux concentrations at a few recurrent locations.

  14. Human Y chromosome haplogroup R-V88: a paternal genetic record of early mid Holocene trans-Saharan connections and the spread of Chadic languages

    PubMed Central

    Cruciani, Fulvio; Trombetta, Beniamino; Sellitto, Daniele; Massaia, Andrea; Destro-Bisol, Giovanni; Watson, Elizabeth; Beraud Colomb, Eliane; Dugoujon, Jean-Michel; Moral, Pedro; Scozzari, Rosaria

    2010-01-01

    Although human Y chromosomes belonging to haplogroup R1b are quite rare in Africa, being found mainly in Asia and Europe, a group of chromosomes within the paragroup R-P25* are found concentrated in the central-western part of the African continent, where they can be detected at frequencies as high as 95%. Phylogenetic evidence and coalescence time estimates suggest that R-P25* chromosomes (or their phylogenetic ancestor) may have been carried to Africa by an Asia-to-Africa back migration in prehistoric times. Here, we describe six new mutations that define the relationships among the African R-P25* Y chromosomes and between these African chromosomes and earlier reported R-P25 Eurasian sub-lineages. The incorporation of these new mutations into a phylogeny of the R1b haplogroup led to the identification of a new clade (R1b1a or R-V88) encompassing all the African R-P25* and about half of the few European/west Asian R-P25* chromosomes. A worldwide phylogeographic analysis of the R1b haplogroup provided strong support to the Asia-to-Africa back-migration hypothesis. The analysis of the distribution of the R-V88 haplogroup in >1800 males from 69 African populations revealed a striking genetic contiguity between the Chadic-speaking peoples from the central Sahel and several other Afroasiatic-speaking groups from North Africa. The R-V88 coalescence time was estimated at 9200–5600 kya, in the early mid Holocene. We suggest that R-V88 is a paternal genetic record of the proposed mid-Holocene migration of proto-Chadic Afroasiatic speakers through the Central Sahara into the Lake Chad Basin, and geomorphological evidence is consistent with this view. PMID:20051990

  15. Holocene core logs and site methods for modern reef and head-coral cores - Dry Tortugas National Park, Florida

    USGS Publications Warehouse

    Hickey, Todd D.; Reich, Christopher D.; DeLong, Kristine L.; Poore, Richard Z.; Brock, John C.

    2013-01-01

    The Dry Tortugas are a series of islands, banks, and channels on a carbonate platform off the west end of the Florida Keys. Antecedent topography of the Dry Tortugas reflects carbonate accumulations of the last interglacial (marine isotope substage 5e, ~ 125,000 years ago, ka) when sea level was ~ 6 to 7 meters (m) higher than present (Schrag and others, 2002). The substage 5e surface was subsequently lithified and modified during subaerial exposure associated with lower sea level from ~ 120 ka to 8 ka. The lithified late Pleistocene carbonates are known as the Key Largo Limestone, a coral reef (Hoffmeister and Multer, 1964; Multer and others, 2002), and the Miami Limestone, a tidal-bar oolite (Sanford, 1909; Hoffmeister, 1974). The Holocene and modern sediments and reefs of the Dry Tortugas then accreted during the rise of sea level associated with the end of the last glacial and the start of the current interglacial (marine isotope Stage 1). With the exception of a half dozen or so islands, the Dry Tortugas region has been submerged for approximately 8,000 years, allowing conditions suitable for coral reef formation once again. The Holocene reef accumulation varies in thickness due to the antecedent topography. The reefs are composed of massive head corals such as species of Montastraea, Siderastrea, and Diploria (Swart and others, 1996; Cohen and McConnaughey, 2003) and rest atop the Pleistocene Key Largo Limestone high (Shinn and others, 1977). The coral reefs within the Dry Tortugas represent a windward reef margin relative to dominant wind and wave energies (Hine and Mullins, 1983; Mallinson and others, 1997; Mallinson and others, 2003).

  16. Slipstream: an early Holocene slump and turbidite record from the frontal ridge of the Cascadia accretionary wedge off western Canada and paleoseismic implications

    USGS Publications Warehouse

    Hamilton, T. S.; Enkin, Randolph J.; Riedel, Michael; Rogers, Gary C.; Pohlman, John W.; Benway, Heather M.

    2015-01-01

    800 years (marine reservoir correction ΔR= 400 years). Rather, the top of the core appears to be 400 years in the future. A younger marine reservoir age of 400 years (ΔR = 0 years) brings the top to the present and produces better correlations with the nearby Effingham Inlet paleo-earthquake chronology based only on terrestrial carbon requiring no reservoir correction. The high-resolution dating and facies analysis of Slipstream Slump in this isolated slope basin setting demonstrates that this is also a useful type of sedimentary target for sampling the paleoseismic record in addition to the more studied turbidites from submarine canyon and channel systems. The first 10 turbidites at Slipstream Slump were deposited between 10.8 and 6.6 ka BP, after which the system became sediment starved and only two more turbidites were deposited. The recurrence interval for the inferred frequent early Holocene megathrust earthquakes is 460 ± 140 years, compatible with other estimates of paleoseismic megathrust earthquake occurrence rates along the subduction zone.

  17. Holocene local forest history at two sites in Småland, southern Sweden - insights from quantitative reconstructions using the Landscape Reconstruction Algorithm

    NASA Astrophysics Data System (ADS)

    Cui, Qiaoyu; Gaillard, Marie-José; Lemdahl, Geoffrey; Olsson, Fredrik; Sugita, Shinya

    2010-05-01

    Quantitative reconstruction of past vegetation using fossil pollen was long very problematic. It is well known that pollen percentages and pollen accumulation rates do not represent vegetation abundance properly because pollen values are influenced by many factors of which inter-taxonomic differences in pollen productivity and vegetation structure are the most important ones. It is also recognized that pollen assemblages from large sites (lakes or bogs) record the characteristics of the regional vegetation, while pollen assemblages from small sites record local features. Based on the theoretical understanding of the factors and mechanisms that affect pollen representation of vegetation, Sugita (2007a and b) proposed the Landscape Reconstruction Algorithm (LRA) to estimate vegetation abundance in percentage cover for well defined spatial scales. The LRA includes two models, REVEALS and LOVE. REVEALS estimates regional vegetation abundance at a spatial scale of 100 km x 100 km. LOVE estimates local vegetation abundance at the spatial scale of the relevant source area of pollen (RSAP sensu Sugita 1993) of the pollen site. REVEALS estimates are needed to apply LOVE in order to calculate the RSAP and the vegetation cover within the RSAP. The two models were validated theoretically and empirically. Two small bogs in southern Sweden were studied for pollen, plant macrofossil, charcoal, and coleoptera in order to reconstruct the local Holocene forest and fire history (e.g. Greisman and Gaillard 2009; Olsson et al. 2009). We applied the LOVE model in order to 1) compare the LOVE estimates with pollen percentages for a better understanding of the local forest history; 2) obtain more precise information on the local vegetation to explain between-sites differences in fire history. We used pollen records from two large lakes in Småland to obtain REVEALS estimates for twelve continuous 500-yrs time windows. Following the strategy of the Swedish VR LANDCLIM project (see Gaillard

  18. Lakeside Cemeteries in the Sahara: 5000 Years of Holocene Population and Environmental Change

    PubMed Central

    Sereno, Paul C.; Garcea, Elena A. A.; Jousse, Hélène; Stojanowski, Christopher M.; Saliège, Jean-François; Maga, Abdoulaye; Ide, Oumarou A.; Knudson, Kelly J.; Mercuri, Anna Maria; Stafford, Thomas W.; Kaye, Thomas G.; Giraudi, Carlo; N'siala, Isabella Massamba; Cocca, Enzo; Moots, Hannah M.; Dutheil, Didier B.; Stivers, Jeffrey P.

    2008-01-01

    Background Approximately two hundred human burials were discovered on the edge of a paleolake in Niger that provide a uniquely preserved record of human occupation in the Sahara during the Holocene (∼8000 B.C.E. to the present). Called Gobero, this suite of closely spaced sites chronicles the rapid pace of biosocial change in the southern Sahara in response to severe climatic fluctuation. Methodology/Principal Findings Two main occupational phases are identified that correspond with humid intervals in the early and mid-Holocene, based on 78 direct AMS radiocarbon dates on human remains, fauna and artifacts, as well as 9 OSL dates on paleodune sand. The older occupants have craniofacial dimensions that demonstrate similarities with mid-Holocene occupants of the southern Sahara and Late Pleistocene to early Holocene inhabitants of the Maghreb. Their hyperflexed burials compose the earliest cemetery in the Sahara dating to ∼7500 B.C.E. These early occupants abandon the area under arid conditions and, when humid conditions return ∼4600 B.C.E., are replaced by a more gracile people with elaborated grave goods including animal bone and ivory ornaments. Conclusions/Significance The principal significance of Gobero lies in its extraordinary human, faunal, and archaeological record, from which we conclude the following: The early Holocene occupants at Gobero (7700–6200 B.C.E.) were largely sedentary hunter-fisher-gatherers with lakeside funerary sites that include the earliest recorded cemetery in the Sahara.Principal components analysis of craniometric variables closely allies the early Holocene occupants at Gobero with a skeletally robust, trans-Saharan assemblage of Late Pleistocene to mid-Holocene human populations from the Maghreb and southern Sahara.Gobero was abandoned during a period of severe aridification possibly as long as one millennium (6200–5200 B.C.E).More gracile humans arrived in the mid-Holocene (5200–2500 B.C.E.) employing a diversified

  19. Assessing the Timing and Magnitude of the Holocene Thermal Maximum (HTM) Using Temperature Reconstructions from Chironomids

    NASA Astrophysics Data System (ADS)

    Langdon, P. G.; Brooks, S. J.; Massaferro, J.; Gilchrist, S.

    2005-12-01

    The magnitude and timing of Holocene maximum warmth has been the subject of considerable recent interest, particularly in the context of future climate change. Recent data syntheses from the Western Hemisphere of the Arctic (0-180 deg W; north of c.60 deg N) indicate that the HTM was time-transgressive over this region, with warming being particularly delayed in the vicinity of residual Laurentide ice, although the primary forcing was governed by orbital variations that scaled with latitude (Kaufman et al. 2004). Over 140 sites were used for this study, mainly relying on pollen and plant macrofossil reconstructions, with only 16 terrestrial sites providing quantitative reconstructions. Here, we present syntheses of HTM temperature reconstructions from chironomid stratigraphies using transfer functions based on modern calibration. Chironomids have been shown to be particularly sensitive indicators of summer temperatures especially during the early Holocene, where as well as indicating the timing and magnitude of peak warmth, they are also able to pick out minor climatic oscillations across a broad European transect (e.g. Caseldine et al., submitted; Brooks et al., in prep). The northern European chironomid reconstructions indicate HTM conditions from relatively high latitudes occurred around 10k cal. BP. Reconstructions from relatively lower latitudes, however, clearly demonstrate a relatively cool, unstable early Holocene that eventually leads to an HTM of conditions warmer than today after about 8k cal. yr BP that lasted for about 1.5-2.0k years, at least 2k years later than HTM conditions at higher Arctic latitudes. Some Holocene chironomid reconstructions have been undertaken from the southern hemisphere (e.g. Massaferro and Brooks, 2002), notably around central and southern Chile, although as yet no temperature-inference transfer functions exist for these regions. Preliminary comparisons will, however, be made between the different hemispheric chironomid

  20. Asynchronous neoglaciation and holocene climatic change reconstructed from Norwegian glaciolacustrine sedimentary sequences

    SciTech Connect

    Matthews, J.A. ); Karlen, W. )

    1992-11-01

    Sedimentary sequences from glacial lakes in southern Norway provide a new approach to the reconstruction of a relatively complete record of Holocene glacier and climatic variations. The data show that, following the [open quotes]Climatic Optimum[close quotes] of the early Holocene, neoglaciation was asynchronous: glaciers formed at different times at different sites, depending on critical altitudinal thresholds in relation to the scale of climatic variations. Neoglaciation began as early as ca. 6400 yr B.P. at Gjuvvatnet, ca. 3400 yr B.P. at Midtivatnet, and later than ca. 1000 yr B.P. at Storevatnet. These differences in glacierization provide a key to reconstructing the fluctuating decline in mean summer temperature (relative to the present) from at least +1 [degrees]C during the mid-Holocene to below -2 [degrees]C in the [open quotes]Little Ice Age[close quotes]. 34 refs., 4 figs.

  1. Late Glacial and Early Holocene Climatic Changes Based on a Multiproxy Lacustrine Sediment Record from Northeast Siberia

    SciTech Connect

    Kokorowski, H D; Anderson, P M; Sletten, R S; Lozhkin, A V; Brown, T A

    2008-05-20

    Palynological (species assemblage, pollen accumulation rate), geochemical (carbon to nitrogen ratios, organic carbon and biogenic silica content), and sedimentological (particle size, magnetic susceptibility) data combined with improved chronology and greater sampling resolution from a new core from Elikchan 4 Lake provide a stronger basis for defining paleoenvironmental changes than was previously possible. Persistence of herb-dominated tundra, slow expansion of Betula and Alnus shrubs, and low percentages of organic carbon and biogenic silica suggest that the Late-Glacial transition (ca. 16,000-11,000 cal. yr BP) was a period of gradual rather than abrupt vegetation and climatic change. Consistency of all Late-Glacial data indicates no Younger Dryas climatic oscillation. A dramatic peak in pollen accumulation rates (ca. 11,000-9800 cal. yr BP) suggests a possible summer temperature optimum, but finer grain-sizes, low magnetic susceptibility, and greater organic carbon and biogenic silica, while showing significant warming at ca. 11,000 cal. yr BP, offer no evidence of a Holocene thermal maximum. When compared to trends in other paleo-records, the new Elikchan data underscore the apparent spatial complexity of climatic responses in Northeast Siberia to global forcings between ca. 16,000-9000 cal. yr BP.

  2. New data on avifauna of the Ustyurt plateau in the Holocene.

    PubMed

    Nekrasov, A E; Kosintsev, P A; Samashev, Z; Ongar, A; Loshakova, T N; Bolshakov, V N

    2016-07-01

    Bone remains of birds from a location of the middle Subboreal period and from three locations of the early Subatlantic period were studied on the Ustyurt plateau (Kazakhstan). Three out of 17 avian species that have been identified (Phalacrocorax pygmaeus, Falco peregrinus, and Nyctea scandiaca) proved to be absent in the modern fauna of the region. Our data on the bird fauna of the Ustyurt Plateau in the second half of the Middle Holocene and at the beginning of the Late Holocene indicate that, in that time, the migration routes of the little cormorant, peregrine, and snowy owl passed across the Ustyurt territory and the wintering sites of peregrine and snowy owl were more extensive and were also situated in Ustyurt. In the second half of the Late Holocene, the number of wintering sites of these species diminished and their migration routes have been altered. PMID:27595824

  3. Fluvial development of the Nete valley during the Late Weichselian and early Holocene: new data from a cross-section south of Kasterlee (NE-Belgium)

    NASA Astrophysics Data System (ADS)

    Beerten, Koen; Van Nieuland, Jasper; Vandenberghe, Dimitri; Deforce, Koen; Rogiers, Bart

    2014-05-01

    The Late Quaternary geomorphology and stratigraphy of the fluvial deposits in the Kleine Nete valley is poorly documented, apart from the classic paper by Munaut and Paulissen (1973) on the palaeo-ecology of this river valley. A good description of the fluvial development within this catchment over longer timescales would help to understand palaeohydrological conditions, as it may give insight into changes in river bed elevation and palaeo-channel morphology. As such, existing hydrological models can be tested for conditions that are different than today, by unlocking the palaeohydrological archive. During road construction works, a cross-section through the Kleine Nete alluvium could be observed, directly (tens of meters) south of the present river course and underneath an abandoned channel that is traceable on historical maps and still visible in the landscape today. The river's alluvium is very thin - the sediment thickness usually does not exceed 2-3 m - while the composition is monotonous, either sand or peat with at a thin loamy layer at the top. Different fluvial facies, including horizontally laminated and cross-bedded sands, channel-fill sands, in-situ (?) peat layers, reworked peat mixed with sand, and loamy alluvium were encountered and sampled for grain-size analysis, palynological analysis and optically stimulated luminescence (OSL) dating. The preliminary results show that vertical aggradation took place during the late Pleniglacial (between ca. 20-16 ka) over a large area (probably by a braided river). This aggradation phase was followed by incision and the development of confined channels that subsequently were filled with basal peat and channel sands during the Late Glacial (ca. 15-12 ka) and the early Holocene (ca. 11 ka). The different dimensions of the observed channels (cross-section and river bed elevation), in comparison with those of the present-day river, suggest that large parts of the alluvial plain were experiencing different

  4. Late glacial and Early Holocene climatic conditions along the margin of the Greenland Ice Sheet, registered by glacial extents in Milne Land, east Greenland

    NASA Astrophysics Data System (ADS)

    Levy, L.; Kelly, M. A.; Lowell, T. V.

    2010-12-01

    to 10,410 yr, indicating that glacial advances occurred during the late Younger Dryas and early Holocene time. The ELA depression of 3-4°C associated with these advances indicates strong seasonality during this time period. These new ages do not show an influence of 10Be inherited from prior periods of exposure, an issue that has hindered applications of 10Be dating in the region in the past. Thus, these ages demonstrate clear evidence for advances of late glacial and early Holocene cooling that must have also influenced the margin of the Greenland Ice Sheet.

  5. Using Detrital Zircon (U-Th)/He Thermochronology From the Sutlej River Valley in the NW Indian Himalaya to Examine Erosion Distribution During the Early Holocene Monsoon

    NASA Astrophysics Data System (ADS)

    Michalak, M.; Hourigan, J.; Bookhagen, B.

    2008-12-01

    The Himalaya and Tibet are an unrivaled example of continent-continent collision. This extensive orogenic system influences regional climate and is characterized by rapid erosion and exhumation. The interplay between climate-driven erosion and rock uplift is key in understanding the geomorphic evolution of the orogen. Recent studies using detrital zircon fission track data, combined with geomorphic models informed by Tropical Rainfall Measurement Mission (TRMM) [Bookhagen et al. 2005] data and thermal-kinematic models [Brewer and Burbank 2006] show a strong correlation between regions of high precipitation rates and rapid erosion in the modern. However, paleoclimate records indicate evidence for a strengthened monsoon during the early Holocene [e.g., Fleitmann et al. 2003, Gupta et al. 2003]. It is believed that in addition to an increase of the monsoon's intensity precipitation penetrated farther into the Himalayan valleys [Bookhagen et al. 2005; Goodbred and Kuehl, 2000]. This study examines this correlation using detrital (U-Th)/He analyses in both modern and paleo-fluvial fill terrace sediments. A preliminary data set of sixty (U-Th)/He zircon grain-ages show the modern and paleo-fluvial terrace sediments reflect different population distributions, or probability density functions (PDF), of grain-ages. The slightly older (3 Ma higher) peak age of the paleo-fluvial terrace sample grain-age population is interpreted to correlate with a northward shift in spatial erosion, due to a strengthened early Holocene monsoon. Eighty more (U-Th)/He zircon grain-ages are presently being analyzed in order to achieve two statistically significant (n= 70) PDFs to make the comparison between modern-day and paleo-fluvial fill populations more robust. In addition, this study synthesizes TRMM-imaged precipitation and geomorphic and thermal-kinematic models to yield a synthetic, 'predicted' detrital grain-age population; a PDF for the modern-day fluvial system. This approach allows

  6. DISTRIBUTION COEFFICIENTS FOR THE VOGTLE EARLY SITE PERMIT

    SciTech Connect

    Kaplan, D; Margaret Millings, M

    2006-07-18

    A series of sediment distribution coefficients, Kd values, measurements were conducted for Southern Nuclear Company, Inc. in support of their Early Site Permit application at Plant Vogtle, Georgia. Nineteen sediment and a representative groundwater samples from the Vogtle site were provided for the Savannah River National Laboratory to conducted site-specific Co, Cs, and Sr Kd measurements. The median Kd values of Co was 6.5 mL/g, for Sr was 10.0 mL/g, and for Cs was 18.8 mL/g. Cation exchange capacity (6.8 to 33.6 meq/100 g), particle size distribution (70 to 94% sand) and pH (4.7 to 5.2) were also measured in five sediments. The Kd values and the sediment properties values measured in these sediments were consistent with those measured in this region of the country.

  7. The Holocene History of Placentia Bay, Newfoundland

    NASA Astrophysics Data System (ADS)

    Sheldon, Christina; Seidenkrantz, Marit-Solveig; Reynisson, Njáll; Juncker Hansen, Mette; Zilmer Christensen, Eva; Kuijpers, Antoon

    2013-04-01

    Marine sediments analyzed from cores taken in Placentia Bay, Newfoundland, located in the Labrador Sea, captured oceanographic and climatic changes from the end of the Younger Dryas through the Holocene. Placentia Bay is an ideal site to capture changes in both the south-flowing Labrador Current and the north-flowing Gulf Stream, currents which are closely tied to the strength of the North Atlantic sub-polar gyre and the North Atlantic Oscillation. Changes in the atmospheric and oceanographic circulation patterns in the North Atlantic after the last glacial period are inferred from faunal assemblages, mineralogy and dinoflagellate analyses. During the 2007 Akademik Ioffe cruise, three cores were taken from Placentia Bay: AI07-14G, representing the time period 12.7 to 9.8 cal kyr BP, AI07-10G, covering the period ca. 10.4 cal kya BP to the present, and AI07-12G, representing the last 5.7 cal kya. These cores have been analyzed using several climate proxies, including benthic foraminifera, diatoms, IP25, dinoflagellate cysts and XRF. Together, these cores provide high-resolution records of the changes in climatic conditions over the last ca. 13,000 years in the southern Labrador Sea. After the Younger Dryas ended, the beginning of the warmer early Holocene was recorded by an increase in productivity-linked foraminiferal and diatom assemblages, as well as a drop in the presence of the sea-ice indicator IP25 in core 14G (Pearce et al., 2012). Variability in atmospheric circulation during the Holocene was analyzed in core 12G and used to reconstruct changes in the mode of the North Atlantic Oscillation during the late Holocene by analysis of exotic pollen grains. Sea-surface conditions during the late Holocene in Placentia Bay reflect a decrease in the strength of the Labrador Current, based on warmer sea-surface temperatures and a simultaneous decline in Arctic water export, from ~4000 cal years to ~3000 cal years BP, which falls into the overall large-scale trend of

  8. Holocene Sea-Level Database For The Caribbean Region

    NASA Astrophysics Data System (ADS)

    Khan, N. S.; Horton, B.; Engelhart, S. E.; Peltier, W. R.; Scatena, F. N.; Vane, C. H.; Liu, S.

    2013-12-01

    Holocene relative sea-level (RSL) records from far-field locations are important for understanding the driving mechanisms controlling the nature and timing of the mid-late Holocene reduction in global meltwaters and providing background rates of late Holocene RSL change with which to compare the magnitude of 20th century RSL rise. The Caribbean region has traditionally been considered far-field (i.e., with negligible glacio-isostatic adjustment (GIA) influence), although recent investigations indicate otherwise. Here, we consider the spatial variability in glacio-isostatic, tectonic and local contributions on RSL records from the circum-Caribbean region to infer a Holocene eustatic sea-level signal. We have constructed a database of quality-controlled, spatially comprehensive, Holocene RSL observations for the circum-Caribbean region. The database contains over 500 index points, which locate the position of RSL in time and space. The database incorporates sea-level observations from a latitudinal range of 5°N to 25°N and longitudinal range of 55°W to 90°W. We include sea-level observations from 11 ka BP to present, although the majority of the index points in the database are younger than 8 ka BP. The database is sub-divided into 13 regions based on the distance from the former Laurentide Ice Sheet and regional tectonic setting. The index points were primarily derived from mangrove peat deposits, which in the Caribbean form in the upper half of the tidal range, and corals (predominantly Acropora palmata), the growth of which is constrained to the upper 5 m of water depth. The index points are classified on the basis of their susceptibility to compaction (e.g., intercalated, basal). The influence of temporal changes in tidal range on index points is also considered. The sea-level reconstructions demonstrate that RSL did not exceed the present height (0 m) during the Holocene in the majority of locations, except at sites in Suriname/Guayana and possibly Trinidad

  9. The origin and disappearance of the late Pleistocene-early Holocene short-lived coastal wetlands along the Carmel coast, Israel

    NASA Astrophysics Data System (ADS)

    Sivan, Dorit; Greenbaum, Noam; Cohen-Seffer, Ronit; Sisma-Ventura, Guy; Almogi-Labin, Ahuva

    The formation of short-lived backswamps along the Carmel coast of Israel coincides with the rapid global sea-level rise during the late Pleistocene-early Holocene transition. The current study shows that the wetland phenomena originated around 10,000 yr ago and dried up shortly before the local Pre-Pottery Neolithic humans settled on the wetland dark clay sediments 9430 cal yr BP. Palaeontological and stable-isotope data were used in this study to elucidate previously published sedimentological reconstruction obtained from a core drilled into the western trough of the Carmel coastal plain. The water body contained typical brackish calcareous fauna, with variable numerical abundance and low species richness of ostracods and foraminifera. The δ 18O and δ 13C of the ostracod Cyprideis torosa show close similarity to the present Pleistocene coastal aquifer isotopic values. This study therefore concludes that the wetlands were shallow-water bodies fed by groundwater, with no evidence of sea-water mixing. It seems that they developed as the result of high groundwater levels, transportation of sediments landward, and deposition of sand bars at the paleo-river mouths. It is still not fully understood why these wetlands deteriorated abruptly and disappeared within less than 1000 yr.

  10. Atmospheric production signal in 10Be from varved sediments of Lake Meerfelder Maar during the late glacial-early Holocene transition

    NASA Astrophysics Data System (ADS)

    Czymzik, Markus; Adolphi, Florian; Muscheler, Raimund; Brauer, Achim; Mekhaldi, Florian; Martin-Puertas, Celia; Tjallingii, Rik; Aldahan, Ala; Possnert, Göran

    2016-04-01

    Beryllium 10 concentrations (10Becon) were measured at 20-year resolution in annually laminated (varved) sediments of Lake Meerfelder Maar (western Germany) covering the late glacial-early Holocene transition 11310-13130 varve years before present. Comparing the 10Becon record to environmental proxy records from the same archive indicates that varying sediment accumulation and composition only slightly modify trends, but do not substantially influence multi-decadal to centennial 10Becon excursions. Corrected for potential environmental biases using multiple-regression analysis, the resulting 10Beatmosphere time-series likely represents an alternative mid-latitude 10Be production record, exhibiting broad similarities but also some differences to radionuclide records as 14C in tree rings and 10Be in polar ice cores. The preservation of the globally common atmospheric production signal in 10Be from varved lake sediments indicates the, to date, largely unexplored potential of these archives for the synchronization to other radionuclide records around the globe, complementing existing solar activity reconstructions and Sun-climate studies.

  11. Human used upper montane ecosystem in the Horton Plains, central Sri Lanka - a link to Lateglacial and early Holocene climate and environmental changes

    NASA Astrophysics Data System (ADS)

    Premathilake, Rathnasiri

    2012-09-01

    This study utilizes radiocarbon-dated pollen, spores, Sphagnum spp. macrofossils and total organic carbon proxies to examine variability of past climate, environment and human activity in montane rainforest, grassland and wetland of the Horton Plains (HP), central Sri Lanka since the Last Glacial Maximum (LGM). The LGM is largely characterized by grasslands and xerophytic herbs dominated open habitats. Arid-LGM punctuated climatic ameliorations, which took place in short episodes. Humans appear to have reached the HP ecosystem after 18,000 cal yrs BP occasionally. The first Intertropical Convergence Zone (ITCZ) induced changes in South West Monsoon (SWM) rains occurred at low latitudes between 16,200 and 15,900 cal yrs BP suggesting an onset of monsoon rains. After this event, monsoon rains weakened for several millennia except the period 13,700-13,000 cal yrs BP, but human activity seems to have continued with biomass burning and clearances by slash and burn. Very large size grass pollen grains, which are morphologically similar to pollen from closer forms of Oryza nivara, were found after 13,800 cal yrs BP. Early Holocene extreme and abrupt climate changes seem to have promoted the forms of O. nivara populations in association with humans. New data from the HP would therefore be most interesting to investigate the dispersal and use of domesticated rice in South Asia.

  12. Site correction of earthquake early warning system in Ilan, Taiwan

    NASA Astrophysics Data System (ADS)

    Chiao Chu, Hsu; Liang, Wen Kuo; Jyun Yan, Huang

    2015-04-01

    When large earthquake occurs, earthquake early warning (EEW) provides alerts to urban areas of the forthcoming strong ground shaking. Depending on the specific geometry of the epicenter and the strong motion network used in EEW, the warning time can be a few seconds to tens of seconds. This warning time can be extremely important since even a few seconds can be sufficient for pre-programmed systems to have emergency response. The Central Weather Bureau (CWB) had already used network EEW system to predict intensity map. Due to leveling of intensity was roughly divided into seven grades according to peak acceleration (PGA) in Taiwan, the warning message is not cautious for company, home and school use, the accuracy of predicted PGA were discuss for our result. A practical site correction approach for EEW was constructed in this study. Period parameter (τc) and an amplitude parameter (Pd)from the initial 3 seconds of P waves were calculated after Wu et al.(2005) first for each site of Taiwan Strong-Motion Instrumentation Program (TSMIP) in Ilan, Taiwan for focal depths less than 35 km and magnitude Mw>=5.0. Two pairs of linear relations had showed in each station between τc, magnitude (Mw) and Pd, hypocenter distance (R) that could be corrected individually. Prediction results of PGA from site correction based ground motion prediction equation (Jean et al. 2006) indicated that the corrected parameters of EEW in this study had improved the accuracy of ground motion prediction. Which means reasonable site correction of each station was needed for EEW system. Key works: earthquake early warning, P wave, site correction

  13. Vegetation response to Holocene climate change in monsoon-influenced region of China

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Yu, Zicheng; Chen, Fahu; Zhang, Jiawu; Yang, Bao

    2009-12-01

    Fossil pollen records from 31 sites with reliable chronologies and high-resolution data in the monsoonal region of China were synthesized to document Holocene vegetation and climate change and to understand the large-scale controls on these changes. The reconstruction of moisture histories was based on a four-class ordinal wetness index at 200-year time slices at individual sites. The vegetation experienced diverse changes over the Holocene in different regions: (1) between tropical seasonal rain forest and more open forest in tropical seasonal rain forest region; (2) from mixed evergreen and deciduous broadleaved forest to more deciduous or Pinus-dominated forest in subtropical region; (3) from mixed evergreen and deciduous broadleaved forest to deciduous forest in temperate deciduous forest region; (4) from deciduous broadleaved forest to conifer-deciduous forest in conifer-deciduous mixed forest region; (5) from steppe forest to steppe in temperate steppe region; and (6) from steppe forest/meadow to meadow/steppe in highland meadow/steppe region. Despite various vegetation sequences in different regions, our synthesis results show that a humid climate generally characterized the early and middle Holocene, and a drier climate prevailed during the late Holocene, with an abrupt shift at ca. 4.5 ka (1 ka = 1000 cal yr BP). Abrupt palynological changes based on a squared-chord distance of pollen assemblages occurred at 11-10, 6-5 and 2-1 ka from most sites. The synthesized pattern of moisture change is similar to the ones inferred from other independent climate proxies; however, gradual vegetation changes in the early Holocene lagged about 1000 yr behind the summer monsoon maximum as indicated by speleothem isotope records from Dongge and Sanbao caves. Human activities likely affected vegetation change greatly during the late Holocene, but the magnitude and precise timing are less clear and require further investigation.

  14. Remote Correlation of Paleoceanographic Events in the Northern Parts of Bering and Barents Seas during the Termination I and Early Holocene

    NASA Astrophysics Data System (ADS)

    Ivanova, E. V.; Ovsepyan, E.; Murdmaa, I.; de Vernal, A.; Risebrobakken, B.; Seitkalieva, E.; Radionova, E.; Alekhina, G.

    2014-12-01

    The Barents and Bering seas are closely linked to the High Arctic and to the THC by marine gateways as well as by land-sea and ocean-atmosphere interactions. Our multi-proxy time series demonstrate that these remote seas exhibited dramatic changes during the deglaciation through a succession of global and regional paleoceanographic events including the beginning of Termination I (BT1), Heinrich-1 or Oldest Dryas (OD), Bølling-Allerød (B/A), Younger Dryas (YD) and early Holocene (EH). In the NW Barents Sea, the increased subsurface-to-bottom Atlantic water inflow via the Kvitøya-Erik Eriksen trough (cores S 2519 and S 2528) is inferred at the late OD, late B/A and late YD/EH transition. These events are generally coupled with the strengthened AMOC. A remarkable sea surface warming and sea ice retreat are documented at ~ 13 ka BP. Surface warming and strong Atlantic water inflow were followed by intense iceberg calving in the Erik Eriksen Trough as indicated by the high IRD content of Core S-2519. The rock fragments are unsorted and mainly angular suggesting their ice-rafted (likely iceberg-rafted) origin. Svalbard glaciers apparently derived the material dominated by black schistous mudstones, hard limestones with coral remains, fine-grained sandstones from nearby islands, and icebergs spread it in the Kvitøya-Erik Eriksen Trough during the early deglaciation. The ice rafted coarse terrigenous material supply during the BT1 is also suggested for the NW Bering Sea. In the NW Pacific, NW Bering Sea and Sea of Okhotsk, surface bioproductivity peaked at B/A and EH mainly due to the global warming, enhanced nutrient supply by surface currents from the flooded northeastern shelf, intensified vertical mixing and water exchange through the opened straits. Oxygen-depleted bottom water at intermediate depths characterized several locations including the NW Bering Sea (Core SO201-2-85KL).

  15. Mapping Layer Sequence and Folds of Pre-Holocene Ice at the Pakitsoq "Horizontal Ice Coring"-Site, West Greenland.

    NASA Astrophysics Data System (ADS)

    Reeh, N.; Severinghaus, J.; Ahlstrom, A.; Brook, E.; Petrenko, V.

    2005-12-01

    Since 1985, the δ18O content of the surface ice has been studied at several ice-margin locations in Greenland. A provisional chronology for the ice margin records was established by correlating characteristic δ18O-features in the ice margin records with similar features in dated Greenland deep ice core records. This demonstrated that, at many ice-margin locations, a several hundred metre wide band of ice pre-dating the present warm interglacial occurs adjacent to the ice edge. A main concern with utilizing this aincient ice for studies of the past has been the fear of likely disturbances of the layer sequence by folds and faults. Recent trace element analyses of ice samples from the ice-sheet margin at Pakitsoq, 50 km northeast of Ilulissat/Jakobshavn, West Greenland have unambiguously demonstrated the occurrence of ice from the transition from the Last Glacial Maximum to the Holocene including ice from the Bølling-Allerød and Younger Dryas intervals. Thus large amounts of well-dated old ice with intact content of trace constituents are available at the Pakitsoq ice-margin. However, analysis of the trace constituents as well as visual inspection also demonstrated the occurrence of a large-scale fold in ice representing the Allerød/Younger Dryas/Pre-Boreal climate oscillation. Moreover, observations of ice ablation and dynamics clearly showed that the Pakitsoq ice-margin sector is presently far from a balanced state, stressing the need for developing a model for the evolution of the ice margin in order to support future ice-mining activities. Here, we report on the development of such a model based on mapping of the large-scale structures on the ice margin by using GPS, ground-penetrating radar (GPR), and trace element geo-chemical analysis (mainly δ18O-analysis of ice samples). Samples for δ18O-analysis were collected each year in the period 2001 - 2005 in several profiles across the large scale fold in order to document the time evolution. Altogether more

  16. Assessing bioturbation using micromorphology and biosilicate evidence: A case study of the early-Holocene Brady Soil, central Great Plains, USA

    NASA Astrophysics Data System (ADS)

    Woodburn, T. L.; Hasiotis, S. T.; Johnson, W. C.

    2012-12-01

    The Old Wauneta Roadcut site in southwestern Nebraska exhibits a 1.2 meter-thick exposure of the Brady Soil, a buried paleosol which formed within loess during the Pleistocene-Holocene transition. Excavation of the loess-paleosol sequence has revealed considerable bioturbation by plant roots, invertebrates, and small vertebrates. Bioturbation was not restricted to a single time period, but occurred continually throughout soil development, as evidenced by differing sediment fills and crosscutting relationships. The Brady Soil is an accretionary soil within the uppermost part of the Last Glacial Maximum Peoria Loess. At the base of the solum, the Bkb horizon exhibits an increased illuvial clay and carbonate content, and contains extensive, small (~2cm width), backfilled burrows typically produced by cicada nymphs (Cicadidae) or beetle larvae. The most stable period of the Brady Soil is expressed by the dark (9.8 YR 4/1), thick Ab horizon. This is overlain by an ACb horizon, where soil formation was being extinguished by the onset of Holocene-age Bignell Loess deposition. Within the upper solum and Bignell Loess, a shift in biota activity occurs as indicated by the large burrow (6-12 cm width) and chamber (30-40 cm width) systems observed. Trace sizes suggest that a burrowing rodent, such as the prairie dog (Cynomys sp.) or ground squirrel (Spermophilus sp.), was responsible for their creation. Soil micromorphology was used to distinguish sediment-size classes, mineralogy, and clay morphology of specific loess deposits and soil horizons in order to track displacement of sediment through the profile due to bioturbation. Five block samples were taken in undisturbed sediment and soil horizons for thin-section analysis. Twelve additional samples of burrow cross-sections or bioturbated sediment were analyzed for comparison. Soil features produced by faunal and floral activity were differentiated from features produced by pedologic processes through the identification and

  17. Midwestern Holocene paleoenvironments revealed by floodplain deposits in northeastern Iowa

    SciTech Connect

    Chumbley, C.A.; Baker, R.G. ); Bettis, E.A. III )

    1990-07-20

    Pollen analysis of pond deposits in the upper reaches of a stream from northeastern Iowa, an area beyond the last glacial margin, provides a nearly complete record of vegetational changes during the last 12.5 thousand years. Sixty-one radiocarbon dates provides good chronological control. Spruce forest was replaced by deciduous forest before 9.1 thousand years ago, followed by prairie from 5.4 to 3.5 thousand years ago, and oak savanna from 3.5 thousand years ago until presettlement times. The prairie invasion was nearly 3 thousand years later here than at other sites in Iowa and Minnesota, documenting a late Holocene, rather than an early-middle Holocene, period of maximum warmth and dryness for the southern part of the upper Midwest.

  18. Lagoonal reef accretion and holocene sea-level history from three atolls in the Cook Islands, Central South Pacific

    USGS Publications Warehouse

    Gray, S.C.; Hein, J.R.

    2005-01-01

    Radiocarbon ages of corals from cores collected at nine drill sites in the lagoons of three atolls (Pukapuka, Rakahanga, Aitutaki, Cook Islands) provide a history of lagoon sedimentation in response to Holocene sea-level rise and stabilization. Holocene lagoonal reefs were established between 8700 and 7800 years B.P. on 130,000-200,000 year-old reef platforms that are presently 7 to 22 m below the floor of the lagoons. Comparison of radiocarbon ages of the deepest corals to published sea-level curves indicate that Holocene reefs colonized these substrates rapidly (Holocene in the lagoons varied by location (83 ?? 2 to 278 ?? 8 cm/ka) and decreased through the Holocene in six of seven drill holes as the lagoons shallowed and became enclosed by the outer reef. A sample from an emergent (<0.5 m above present mean tide) reef on Rakahanga is 4610 ?? 100 years old, which may indicate a higher middle Holocene relative sea level on Rakahanga. Coral growth in Rakahanga lagoon ceased less than 2000 years ago, but was prolific in the early to middle Holocene. The timing and pattern of Holocene reef development exhibited in the Cook Islands is consistent with other oceanic islands. An assessment of the response of reef development to sea-level change during the Holocene provides a baseline to predict how future sea-level changes may affect the morphology of modern reefs.

  19. Site characterization using a portable optically stimulated luminescence reader: delineating disrupted stratigraphy in Holocene eolian deposits on the Canadian Great Plains

    NASA Astrophysics Data System (ADS)

    Munyikwa, K.; Gilliland, K.; Gibson, T.; Plumb, E.

    2012-12-01

    The use of portable optically stimulated luminescence (POSL) readers to elucidate on complex depositional sequences has been demonstrated in a number of recent studies. POSL readers are robust versions of the traditional lab-bound luminescence readers and they can be used in the field, allowing for rapid decisions to be made when collecting samples for dating. Furthermore, in contrast with lab-bound readers, POSL readers can perform measurements on bulk samples, negating the need to carry out time-intensive mineralogical separations. The POSL reader is equipped with both infra-red and blue light (OSL) stimulating sources such that signal separation during measurement can be carried out by selectively exciting feldspar using the IR source (IRSL) after which a quartz dominant signal is obtained from the same sample using post-IR blue OSL. The signals obtained are then plotted to give luminescence profiles that depict the variation of the luminescence signal with depth. Signal intensities depend on mineralogical concentrations, grain luminescence sensitivities, dose rates as well as on burial ages of the grains. Where all these variables, apart from the burial age, are held constant up the depositional sequence the luminescence profile serves as a proxy for the chronostratigraphy. As a contribution to a growing archive of studies that have employed POSL readers to unravel complex depositional sequences, this study uses a POSL system developed by the Scottish Universities Environmental Research Centre to characterize the stratigraphy at an archaeological site that lies next to an oilfield plant located on a Holocene fossil dune landscape in southern Alberta, Canada. Oilfield activity was initiated at the site several decades ago and it involved the laying of pipelines below ground which disturbed considerable archaeological deposits. Subsequent work led to the discovery of the archeological site which was previously occupied by ancestral indigenous peoples at various

  20. Holocene multidecadal and multicentennial droughts affecting Northern California and Nevada

    USGS Publications Warehouse

    Benson, L.; Kashgarian, Michaele; Rye, R.; Lund, S.; Paillet, F.; Smoot, J.; Kester, C.; Mensing, S.; Meko, D.; Lindstrom, S.

    2002-01-01

    Continuous, high-resolution ??18O records from cored sediments of Pyramid Lake, Nevada, indicate that oscillations in the hydrologic balance occurred, on average, about every 150 years (yr) during the past 7630 calendar years (cal yr). The records are not stationary; during the past 2740 yr, drought durations ranged from 20 to 100 yr and intervals between droughts ranged from 80 to 230 yr. Comparison of tree-ring-based reconstructions of climate change for the past 1200 yr from the Sierra Nevada and the El alpais region of northwest New Mexico indicates that severe droughts associated with Anasazi withdrawal from Chaco Canyon at 820 cal yr BP (calendar years before present) and final abandonment of Chaco Canyon, Mesa Verde, and the Kayenta area at 650 cal yr BP may have impacted much of the western United States.During the middle Holocene (informally defined in this paper as extending from 8000 to 3000 cal yr BP), magnetic susceptibility values of sediments deposited in Pyramid Lake's deep basin were much larger than late-Holocene (3000-0 cal yr BP) values, indicating the presence of a shallow lake. In addition, the mean ?? 18O value of CaCO3 precipitated between 6500 and 3430 cal yr BP was 1.6??? less than the mean value of CaCO3 precipitated after 2740 cal yr BP. Numerical calculations indicate that the shift in the ??18O baseline probably resulted from a transition to a wetter (> 30%) and cooler (3-5??C) climate. The existence of a relatively dry and warm middle-Holocene climate in the Truckee River - Pyramid Lake system is generally consistent with archeological, sedimentological, chemical, physical, and biological records from various sites within the Great Basin of the western United States. Two high-resolution Holocene-climate records are now available from the Pyramid and Owens lake basins which suggest that the Holocene was characterized by five climatic intervals. TIC and ??18O records from Owens Lake indicate that the first interval in the early Holocene

  1. Deglaciation and latest Pleistocene and early Holocene glacier readvances on the Alaska Peninsula: Records of rapid climate change due to transient changes in solar intensity and atmospheric CO sub 2 content

    SciTech Connect

    Pinney, D.S.; Beget, J.E.

    1992-03-01

    Geologic mapping near Windy Creek, Katmai National Park, identified two sets of glacial deposits postdating late-Wisconsin Iliuk moraines and separated from them by volcaniclastic deposits laid down under ice-free conditions. Radiocarbon dating of organic material incorporated in the younger Katolinat till and in adjacent peat and lake sediments suggests that alpine glaciers on the northern Alaska Peninsula briefly expanded between ca. 8500 and 10,000 years B.P. Stratigraphic relationships and radiocarbon dates suggest an age for the older Ukak drift near the Pleistocene-Holocene boundary between ca. 10,000 and 12,000 years B.P. The authors suggest that rapid deglaciation following deposition of the Iliuk drift occurred ca. 13,000-12,000 years B.P. in response to large increases in global atmospheric greenhouse gas content, including C02. Short-term decreases in these concentrations, as recorded in polar ice cores, may be linked with brief periods of glacier expansion during the latest Pleistocene and early Holocene. A transient episode of low solar intensity may also have occurred during parts of the early Holocene. Rapid environmental changes and glacial fluctuations on the Alaska Peninsula may have been in response to transient changes in the concentration of atmospheric greenhouse gases and solar intensity.

  2. Late Pleistocene to early Holocene aeolian and flash-flood sedimentation and soil formation in a small hilly catchment in SW-Germany (Palatinate forest)

    NASA Astrophysics Data System (ADS)

    Dotterweich, M.; Kühn, P.; Tolksdorf, J. F.; Müller, S.; Nelle, O.

    2012-04-01

    This paper focuses on the dynamics of sedimentation processes and soil development in a steep slope 0-order catchment in the sandy Lower Bunter of the south-western mid-range mountains in Germany during the transition period from the late Glacial to the early Holocene. Italso discusses how late Palaeolithic gatherers and hunters may have influenced these processes by sedentary land occupation. The investigated dry valley covers an area of around 16.6 ha and is characterized by short and steep slopes of 30° to 60°. A significant amount of the sediments from the adjacent slopes had been captured along the wide and rather flat valley bottom and at the small outlet. Several exposures, pits, and percussion liner drillings revealed a weak to highly weathered reddish sandy material at the base and eight subsequent layers of incoherent sandy and charcoal (from pines) enriched sediments with different colours ranging from olive-brown to dull reddish brown. By stratigraphical means, the lowermost sediment can be ascribed to the early Lateglacial when the deposition of aeolian sands under cold conditions with scarce vegetation cover was a widespread phenomenon. The subsequent layer contains a higher amount of silt and dates into the Allerød as suggested by radiocarbon dating. This is corroborated by the occurrence of LST that indicate that these sediments have been near to the surface around 12,900 yr BP. It shows characteristics of a palaeosol with Bwb and BwAhb horizons (Brunic Arenosols dystric) and with greyish Ahb and Eb horizons (Albic Arenosols dystric) similar to the Usselo/Finow soils in north-eastern Germany. In the material above, many remnants of roots and organic particles and rounded bone fragments were revealed by micromorphological analyses. Then, an alternation of reddish brown coarse to fine sands and small, partly rounded stones with some small intercalate aggregations of humic material rich in charcoal which dates to around 10,000 yr BP were deposited

  3. Holocene aeolian activities in the southeastern Mu Us Desert, China

    NASA Astrophysics Data System (ADS)

    Jia, Feifei; Lu, Ruijie; Gao, Shangyu; Li, Jinfeng; Liu, Xiaokang

    2015-12-01

    Aeolian deposits from three sites in the Mu Us Desert were used to reconstruct the history of aeolian activities during the Holocene. The results of the lithologies, chronologies and proxy indicators showed that aeolian activities occurred at ∼9.96 cal ka BP, 7.9-6.9 ka BP, 6.4 ka BP and 3.8 cal ka BP∼. The cold event that occurred around 6.4 ka BP interrupted the Holocene Optimum period, which is largely consistent with the findings from sediments in adjacent regions and the monsoon areas of China. Combined with punished OSL and 14C ages of aeolian deposits samples in this region, the environmental changes in the Mu Us Desert were divided into four stages. Active sand dunes dominated before 11 ka BP. Aeolian activities occurred regionally from 11 to 8.5 ka BP and typical sandy paleosol widely developed with episodic aeolian activities between 8.5 and 4 ka BP. Dunes have reactivated and active sand dunes have gradually increased since 4 ka BP. Comparisons with the other paleoclimatic records indicated that the evolution of the Mu Us Desert was closely related to the East Asian monsoon. Paleosol development depended more on the precipitation brought by the East Asian summer monsoon (EASM). The stronger East Asian winter monsoon (EAMW) and higher isolation resulted in the aeolian activities in the early Holocene, while during the mid-Holocene the fluctuating EAWM played a more important role in inducing episodic aeolian activities. The environmental deterioration during the late Holocene can be related to weakened EASM or to increased anthropogenic influence.

  4. Inferences on Late Holocene climate from stable carbon and oxygen isotope ratio variability in soil and land snail shells from archaeological site 41KM69 in Texas, USA

    NASA Astrophysics Data System (ADS)

    Paul, D.; Mauldin, R.; Munoz, C. M.

    2011-12-01

    Well-preserved land snail shell excavate from archaeological site 41KM69 in Texas, USA, span the past 2200 years and provide an opportunity to explore the paleoclimate implications of isotopic variability in archaeological shell carbonates, bulk soil carbonates and soil organic matter. Terrestrial snail shells belonging to three genera (Polygyra, Rabdotus, and Helicina) were hand-picked from the 120 cm thick soil profile, for stable isotopic analyses. A wood charcoal radiocarbon date constrains samples below 100 cm depth in our soil profile to be ~2200 14C yr BP. Isotopic composition of modern adult snail specimens (n=24) and plants (n=18), collected from the study area, were determined for comparison with the archaeological data sets. All isotopic analyses were performed at the University of Texas at San Antonio using a Thermo Finnigan Gasbench II and a Costech Elemental Analyzer (EA) attached online to a DeltaPlus XP Stable Isotope Ratio Mass Spectrometer in continuous flow mode. Carbon isotopic compositions of both modern (-12.72 to -5.49%) and archaeological (-5.34 to -8.99%) adult snail shell carbonates suggest significant (> 60%) input of C3 plants into the diet of the snails over the past 2200 yrs. Oxygen isotopic compositions of archaeological and modern shells vary from -2.21% to -0.71% and -2.88 to +0.99%), respectively. This suggests that isotopic composition of environmental water (mainly rainwater) available at the time of shell growth was similar to that of the present day. A linearly decreasing trend in δ13C of soil organic matter from -22.83% at 2200 14C yr BP to -25.61% for modern samples imply progressively increasing abundance of C3 plants up to the present day. This implies a progressively wetter climate, or decreasing summer rainfall and less severe water stress conditions, in agreement with other studies on Holocene climate change in the southern Great Plains of USA. The studies, in general, document warm/arid conditions at ~ 2000 BP and

  5. 10 CFR Appendix Q to Part 50 - Pre-Application Early Review of Site Suitability Issues

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Pre-Application Early Review of Site Suitability Issues Q... FACILITIES Pt. 50, App. Q Appendix Q to Part 50—Pre-Application Early Review of Site Suitability Issues This... Reactor Safeguards of requests for early review of one or more site suitability issues relating to...

  6. 10 CFR Appendix Q to Part 50 - Pre-Application Early Review of Site Suitability Issues

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Pre-Application Early Review of Site Suitability Issues Q... FACILITIES Pt. 50, App. Q Appendix Q to Part 50—Pre-Application Early Review of Site Suitability Issues This... Reactor Safeguards of requests for early review of one or more site suitability issues relating to...

  7. 10 CFR Appendix Q to Part 50 - Pre-Application Early Review of Site Suitability Issues

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Pre-Application Early Review of Site Suitability Issues Q... FACILITIES Pt. 50, App. Q Appendix Q to Part 50—Pre-Application Early Review of Site Suitability Issues This... Reactor Safeguards of requests for early review of one or more site suitability issues relating to...

  8. From cold to cool in northernmost Norway: Lateglacial and early Holocene multi-proxy environmental and climate reconstructions from Jansvatnet, Hammerfest

    NASA Astrophysics Data System (ADS)

    Birks, Hilary H.; Jones, Vivienne J.; Brooks, Stephen J.; Birks, H. John B.; Telford, Richard J.; Juggins, Stephen; Peglar, Sylvia M.

    2012-02-01

    A multi-proxy palaeoecological study of the lateglacial and early Holocene sediments of Jansvatnet, Hammerfest, northernmost Norway (70°39' N) showed that cold and arid conditions prevailed in both the lateglacial interstadial and the Younger Dryas. Terrestrial proxies are macrofossils and pollen. Aquatic proxies are plant and invertebrate macrofossils, pollen, diatoms, and chironomids. Mean July temperatures were reconstructed using pollen and chironomid calibration functions and ecological knowledge of the fossil flora and fauna. Lake-water pH was reconstructed using a diatom pH-calibration function. Above sterile basal deglacial silts, biotic activity was detected around 14600 years ago in the interstadial (chronologically equivalent to the Bølling-Allerød in the Greenland Ice-Core Chronology). Catchment vegetation resembled polar desert and ultra-cold stenothermic chironomids lived in the lake. However, diatom assemblages were diverse and dynamic. In the Younger Dryas stadial, conditions deteriorated. In the early Younger Dryas chironomid-inferred air temperatures (CI-Tjul) fell about 1 °C. Pollen-inferred temperatures (PI-Tjul) did not fall and the terrestrial vegetation hardly changed because of the extreme aridity. The lake water was turbid from suspended clay which diminished aquatic life. Later in the Younger Dryas (ca 12400 cal yr BP) reconstructed mean July temperatures fell by a further 3 °C and were close to the minimum to support life, at around 3-4 °C. However, decreased turbidity allowed moss growth on the lake bottom that provided habitats for invertebrates and diatoms. In the last 200 years of the Younger Dryas temperatures increased by 2-3 °C and terrestrial and aquatic organisms responded quickly. At the start of the Holocene a rapid increase of more than 3 °C in PI-Tjul to 9.5 °C initiated the replacement of sparse arctic tundra by low-arctic dwarf-shrub heath. Simultaneously, a further 2 °C increase in CI-Tjul to 10-11 °C reflected

  9. A previously unrecognized path of early Holocene base flow and elevated discharge from Lake Minong to Lake Chippewa across eastern Upper Michigan

    USGS Publications Warehouse

    Loope, Walter L.; Jol, Harry M.; Fisher, Timothy G.; Blewett, William L.; Loope, Henry M.; Legg, Robert J.

    2014-01-01

    It has long been hypothesized that flux of fresh meltwater from glacial Lake Minong in North America's Superior Basin to the North Atlantic Ocean triggered rapid climatic shifts during the early Holocene. The spatial context of recent support for this idea demands a reevaluation of the exit point of meltwater from the Superior Basin. We used ground penetrating radar (GPR), foundation borings from six highway bridges, a GIS model of surface topography, geologic maps, U.S. Department of Agriculture–Natural Resources Conservation Service soils maps, and well logs to investigate the possible linkage of Lake Minong with Lake Chippewa in the Lake Michigan Basin across eastern Upper Michigan. GPR suggests that a connecting channel lies buried beneath the present interlake divide at Danaher. A single optical age hints that the channel aggraded to 225 m as elevated receipt of Lake Agassiz meltwater in the Superior Basin began to wane <10.6 ka. The large supply of sediment required to accommodate aggradation was immediately available at the channel's edge in the littoral shelves of abandoned Lake Algonquin and in distal parts of post-Algonquin fans. As discharge decreased further, the aggraded channel floor was quickly breached and interbasin flow to Lake Chippewa was restored. Basal radiocarbon ages on wood from small lakes along the discharge path and a GIS model of Minong's shoreline are consistent with another transgression of Minong after ca. 9.5 ka. At the peak of the latter transgression, the southeastern rim of the Superior Basin (Nadoway Drift Barrier) failed, ending Lake Minong. Upon Minong's final drop, aggradational sediments were deposited at Danaher, infilling the prior breach.

  10. Evidence for geographic variation in the diets of late Pleistocene and early Holocene Bison in North America, and differences from the diets of recent Bison

    NASA Astrophysics Data System (ADS)

    Rivals, Florent; Solounias, Nikos; Mihlbachler, Matthew C.

    2007-11-01

    During the late Pleistocene and early Holocene , Bison was widely dispersed across North America and occupied most regions not covered by ice sheets. A dietary study on Bison paleopopulations from Alaska, New Mexico, Florida, and Texas was performed using two methods that relate dental wear patterns to diet, mesowear analysis and microwear analysis. These data were compared to a mixed sample of extant Bison from the North American central plains, extant wood Bison from Alberta (Canada) and a variety of other modern ungulates. Mesowear relates macroscopic molar facet shape to levels of dietary abrasion. The mesowear signature observed on fossil Bison differs significantly from the hyper-abrasive grazing diet of extant Bison. Tooth microwear examines wear on the surface of enamel at a microscopic scale. The microwear signal of fossil samples resembles to modern Bison, but the fossil samples show a greater diversity of features, suggesting that fossil Bison populations regularly consumed food items that are texturally inconsistent with the short-grass diet typical of modern plains Bison. Mesowear and microwear signals of fossil Bison samples most closely resemble a variety of typical mixed feeding ungulates, all with diets that are substantially less abrasive than what is typical for modern plains Bison. Furthermore, statistical tests suggest significant differences between the microwear signatures of the fossil samples, thus revealing geographic variability in Pleistocene Bison diets. This study reveals that fossils are of value in developing an understanding of the dietary breadth and ecological versatility of species that, in recent times, are rare, endangered, and occupy only a small remnant of their former ranges.

  11. Tocuila Mammoths, Basin of Mexico: Late Pleistocene-Early Holocene stratigraphy and the geological context of the bone accumulation

    NASA Astrophysics Data System (ADS)

    Gonzalez, Silvia; Huddart, David; Israde-Alcántara, Isabel; Dominguez-Vazquez, Gabriela; Bischoff, James

    2014-07-01

    We report new stratigraphic, tephrochronology and dating results from the Tocuila Mammoth site in the Basin of Mexico. At the site there is evidence for a thin meteorite airburst layer dated between 10,878 and 10,707 cal BC at the onset of the Younger Dryas (YD) cool period. The Upper Toluca Pumice (UTP) tephra marker, caused by a Plinian eruption of the Nevado de Toluca volcano, dated from 10,666 to 10,612 cal BC, is above that layer. The eruption must have caused widespread environmental disruption in the region with evidence of extensive reworking and channelling by the Lake Texcoco shoreline and contributed to the widespread death and/or extinction of megafaunal populations, as suggested by earlier authors, but the new work reinforces the view that both catastrophic events must have caused large environmental disruption in a short time period of around two hundred years. There is no evidence for megafauna (mammoths, sabre toothed cats, camels, bison, glyptodonts) after the UTP volcanic event and subsequent lahars in the Basin of Mexico. At Tocuila, although there are some in situ tephra markers in nearshore lake sediments, such as the Great Basaltic Ash (GBA) and the UTP Ash, there is evidence of much reworking of several tephra populations in various combinations. The mammoth bone accumulation is reworked in a lahar sequence (volcanic mudflow) derived from several source sediments but associated with the major UTP Plinian eruption. Paleoindian populations were also present in the Basin of Mexico during the YD period, where several Paleoindian skeletons were found associated with the UTP ash deposits, e.g. Metro Man, Chimalhuacan Man and Tlapacoya Man.

  12. Middle Holocene thermal maximum in eastern Beringia

    NASA Astrophysics Data System (ADS)

    Kaufman, D. S.; Bartlein, P. J.

    2015-12-01

    A new systematic review of diverse Holocene paleoenvironmental records (Kaufman et al., Quat. Sci. Rev., in revision) has clarified the primary multi-centennial- to millennial-scale trends across eastern Beringia (Alaska, westernmost Canada and adjacent seas). Composite time series from midges, pollen, and biogeochemical indicators are compared with new summaries of mountain-glacier and lake-level fluctuations, terrestrial water-isotope records, sea-ice and sea-surface-temperature analyses, and peatland and thaw-lake initiation frequencies. The paleo observations are also compared with recently published simulations (Bartlein et al., Clim. Past Discuss., 2015) that used a regional climate model to simulate the effects of global and regional-scale forcings at 11 and 6 ka. During the early Holocene (11.5-8 ka), rather than a prominent thermal maximum as suggested previously, the newly compiled paleo evidence (mostly sensitive to summer conditions) indicates that temperatures were highly variable, at times both higher and lower than present, although the overall lowest average temperatures occurred during the earliest Holocene. During the middle Holocene (8-4 ka), glaciers retreated as the regional average temperature increased to a maximum between 7 and 5 ka, as reflected in most proxy types. The paleo evidence for low and variable temperatures during the early Holocene contrasts with more uniformly high temperatures during the middle Holocene and agrees with the climate simulations, which show that temperature in eastern Beringia was on average lower at 11 ka and higher at 6 ka than at present (pre-industrial). Low temperatures during the early Holocene can be attributed in part to the summer chilling caused by flooding the continental shelves, whereas the mid-Holocene thermal maximum was likely driven by the loss of the Laurentide ice sheet, rise in greenhouse gases, higher-than-present summer insolation, and expansion of forest over tundra.

  13. Historic and Holocene environmental change in the San Antonio Creek Basin, mid-coastal California

    NASA Astrophysics Data System (ADS)

    Scott Anderson, R.; Ejarque, Ana; Rice, Johnathan; Smith, Susan J.; Lebow, Clayton G.

    2015-03-01

    Using a combination of pollen, non-pollen palynomorphs (NPPs) and charcoal particle stratigraphies from sediment cores from two sites, along with historical records, we reconstructed paleoenvironmental change in mid-coastal California. The San Antonio Creek section contains a discontinuous, Holocene-length record, while Mod Pond includes a continuous late Holocene record. Together the records allow for interpretation of most of the present interglacial. The longer record documents coastal sage scrub and chaparral dominated by woodland elements early in the Holocene to about 9000 yr ago, a potential decline in woodland communities with drying conditions during the middle Holocene to about 4800 yr ago, and an expansion of coastal sage scrub with grassland during the late Holocene. Evidence for climatic fluctuations during the last 1000 yr at Mod Pond is equivocal, suggesting that the Medieval Climate Anomaly-Little Ice Age had modest impact on the Mod Pond environment. However, evidence of significant environmental change associated with cultural transitions in the 18th-19th centuries is stark. Introduction of non-native plants, establishment of cattle and sheep grazing, missionization of the native population, changes in burning practices during the Spanish period and enhanced cropping activities during North American settlement worked together to substantially modify the mid-California coastal landscape in about a century's time.

  14. Late Holocene and modern pollen records from three sites in Shannon and Carter Counties, southeast Missouri Ozarks

    SciTech Connect

    Huber, J.K. . Archaeometry Lab.)

    1993-03-01

    Palynological investigations of a small sinkhole bog (Buttonbush Bog) and two archaeological sites (Round Spring Shelter, Round Spring Site 23SH19 and Gooseneck Site 23CT54) located in Shannon and Carter counties, Missouri provide a 3,100 year record of vegetational change. Bryophytic polsters and surface samples were also collected in Shannon and Carter counties in the southeast Missouri Ozarks to determine modern pollen rain. A 302-cm core retrieved from Buttonbush Bog has a basal data of 3,130 [+-] 100 yr B.P. and a date of 1,400 [+-] 100 yr B.P. at 52--56 cm. The Buttonbush Bog pollen sequence is divided into three pollen-assemblage zones. The pollen spectra from Buttonbush Bog indicate that pine did not become well established in the southeast Missouri Ozarks until after 3,100 yr B.P. Zone 1 (the oldest) represents a mixed oak forest with minor components of pine and hickory. In Zone 2, pine values increase, indicating a shift to a pine-oak forest. The pollen sequence from Round Spring Shelter is divided into two pollen-assemblage zones. The lower zone (Zone 1) suggests the presence of a pine-oak forest in the vicinity of Round Spring prior to an Ambrosia rise at the top of the sequence in Zone 2. Regional pollen rain and variation in the local pollen rain are reflected by modern pollen spectra extracted from the bryophytic polsters surface samples. In this area the average regional pollen rain is dominated by pine, oak, hickory, and Ambrosia. The data are consistent with the mosaic of pine-oak and oak-hickory-pine forests characteristic of this region.

  15. Disturbance Frequency Changes in Western North and South America During the Holocene

    NASA Astrophysics Data System (ADS)

    Whitlock, C.; Bartlein, P.; Bianchi, M. M.; Briles, C.; Brunelle, A.; Long, C.; Markgraf, V.; Marlon, J.; Meeker, C.; Power, M.; Walsh, M.

    2003-12-01

    Fire is the dominant form of natural disturbance in temperate forested ecosystems, and as such, it serves as a process that links climate change to biosphere response. High-resolution charcoal records from the western temperate forests of North and South America provide an opportunity to compare current and recent (pre-settlement) changes in disturbance frequency with those during the Holocene. Charcoal data describe past fire activity under different climate and vegetation settings and offer information on changing levels of biomass as well as variations in fire frequency. An assessment of North American sites indicates gradually increasing levels of charcoal from the late-glacial to 2 ka, which is consistent with increasing fuel production during the Holocene. Fire-frequency data from both hemispheres indicate that the spatial heterogeneity evident in modern fire regimes has existed throughout the Holocene despite changes in the large-scale controls of climate. The heterogeneity is a result of spatial variations in the seasonal distribution of precipitation and their influence on fire climate and weather. Summer-dry areas (i.e., low summer:annual precipitation) registered higher-than-present fire activity in the early Holocene from ca. 13 to 7 ka. In North America, fire activity was apparently controlled by the early-Holocene strengthening of the northeast Pacific subtropical high during the summer insolation maximum. In Patagonia, high fire activity may have caused by the carry-over effects of low winter soil moisture during the winter insolation maximum. A decline in fire activity in summer-dry regions in the late Holocene suggests seasonally wetter conditions as a result of the onset of ENSO, less seasonality in precipitation, and/or the development of more closed forests. Summer-wet regions show the influence of stronger monsoonal circulation in the early Holocene, which caused a reduction in fire activity. In these regions, the late Holocene featured

  16. Southern Ocean contributions to the Eastern Equatorial Pacific heat content during the Holocene

    NASA Astrophysics Data System (ADS)

    Kalansky, Julie; Rosenthal, Yair; Herbert, Timothy; Bova, Samantha; Altabet, Mark

    2015-08-01

    Temperature reconstructions from a shallow core (375 m) from the Peru Margin are used to test the influence of Subantarctic Mode Water (SAMW) on the eastern equatorial Pacific (EEP) thermostad and thus the effect of southern high latitude climate on interior ocean heat content (OHC). Temperature estimates, based on Mg/Ca measurements of planktonic and benthic foraminifera (Neogloboquadrina dutertrei and Uvigerina spp., respectively) show higher temperatures in the early Holocene, a cooling of ∼ 2 ° by 8 kyr B.P. and after relatively stable temperatures to the present. The temperature signal is similar in direction and timing to a rather robust Holocene climate signal from the southern high latitudes suggesting it originated there and was advected to the core site in the EEP. Based on the N. dutertrei and Uvigerina Mg/Ca temperature and δ13C records we conclude that SAMW acted as a conduit transporting the southern high latitude climate to the interior of the equatorial Pacific. We propose that the early Holocene warmth is related to a southward migration of the Subtropical Front, which enhanced the influence of warm subtropical water in the region of SAMW formation and was then transported to the EEP thermostad. The early Holocene warmth recorded in the EEP thermostad has a muted sea surface temperature expression indicating this mechanism is important for sequestering heat in the ocean interior.

  17. Environments and trypanosomiasis risks for early herders in the later Holocene of the Lake Victoria basin, Kenya.

    PubMed

    Chritz, Kendra L; Marshall, Fiona B; Zagal, M Esperanza; Kirera, Francis; Cerling, Thure E

    2015-03-24

    Specialized pastoralism developed ∼3 kya among Pastoral Neolithic Elmenteitan herders in eastern Africa. During this time, a mosaic of hunters and herders using diverse economic strategies flourished in southern Kenya. It has been argued that the risk for trypanosomiasis (sleeping sickness), carried by tsetse flies in bushy environments, had a significant influence on pastoral diversification and migration out of eastern Africa toward southern Africa ∼2 kya. Elmenteitan levels at Gogo Falls (ca. 1.9-1.6 kya) preserve a unique faunal record, including wild mammalian herbivores, domestic cattle and caprines, fish, and birds. It has been suggested that a bushy/woodland habitat that harbored tsetse fly constrained production of domestic herds and resulted in subsistence diversification. Stable isotope analysis of herbivore tooth enamel (n = 86) from this site reveals, instead, extensive C4 grazing by both domesticates and the majority of wild herbivores. Integrated with other ecological proxies (pollen and leaf wax biomarkers), these data imply an abundance of C4 grasses in the Lake Victoria basin at this time, and thus little risk for tsetse-related barriers to specialized pastoralism. These data provide empirical evidence for the existence of a grassy corridor through which small groups of herders could have passed to reach southern Africa. PMID:25775535

  18. Environments and trypanosomiasis risks for early herders in the later Holocene of the Lake Victoria basin, Kenya

    PubMed Central

    Chritz, Kendra L.; Marshall, Fiona B.; Zagal, M. Esperanza; Kirera, Francis; Cerling, Thure E.

    2015-01-01

    Specialized pastoralism developed ∼3 kya among Pastoral Neolithic Elmenteitan herders in eastern Africa. During this time, a mosaic of hunters and herders using diverse economic strategies flourished in southern Kenya. It has been argued that the risk for trypanosomiasis (sleeping sickness), carried by tsetse flies in bushy environments, had a significant influence on pastoral diversification and migration out of eastern Africa toward southern Africa ∼2 kya. Elmenteitan levels at Gogo Falls (ca. 1.9–1.6 kya) preserve a unique faunal record, including wild mammalian herbivores, domestic cattle and caprines, fish, and birds. It has been suggested that a bushy/woodland habitat that harbored tsetse fly constrained production of domestic herds and resulted in subsistence diversification. Stable isotope analysis of herbivore tooth enamel (n = 86) from this site reveals, instead, extensive C4 grazing by both domesticates and the majority of wild herbivores. Integrated with other ecological proxies (pollen and leaf wax biomarkers), these data imply an abundance of C4 grasses in the Lake Victoria basin at this time, and thus little risk for tsetse-related barriers to specialized pastoralism. These data provide empirical evidence for the existence of a grassy corridor through which small groups of herders could have passed to reach southern Africa. PMID:25775535

  19. The chronology and rate of ice-sheet margin retreat in the major fjords of Western Norway during the Early Holocene

    NASA Astrophysics Data System (ADS)

    Mangerud, J.; Lohne, O. S.; Goehring, B. M.; Svendsen, J.; Gyllencreutz, R.; Schaefer, J. M.

    2009-12-01

    Hardangerfjorden is up to 900 m deep and about 170 km long. The well defined Younger Dryas (YD) end moraine is located 40 km inside the fjord mouth. Lateral moraines show that the surface gradient near the ice front was steep and the glacier was grounded. These moraines can be traced up to 1000 m a.s.l. about 40 km inland, where the fjord is 600 m deep, indicating a total ice thickness of 1600 m. The YD margin terminated on a threshold and the fjord gets much deeper on the proximal side of the moraine. Therefore, the ice margin must have been floating as soon as retreat from the YD position began and calving was certainly an important process during deglaciation. The break up of the glacier ice in the fjord must also have led to a considerable draw down of the ice-sheet surface further inland. According to our dating results the retreat started at 11,500 cal yr BP (Bondevik and Mangerud 2002; Lohne 2007). We have used three methods to estimate the up-fjord retreat: 1) 14C dating of organic material deposited during or soon after deglaciation (Romundset et al., 2009), 2) age determination of ice-marginal deltas by using a shore-line diagram we constructed from data in Lohne et al (2007) and Romundset et al (2009), 3) 10Be exposure dating of a number of large ice-transported boulders. All three methods provide consistent ages in the interval 10,900-11,100 cal yr BP for the deglaciation of the fjord head, which yields a mean retreat rate of 220-330 m/year. The ages for Hardangerfjorden can also be used for the even longer (220 km) and deeper (1300 m) Sognefjorden, giving a retreat rate of 370-550 m/year, because the relevant YD and Early Holocene moraines have been mapped and correlated (Vorren and Mangerud 2008). Bondevik, S. and Mangerud, J., 2002. A calendar age estimate of a very late Younger Dryas ice sheet maximum in western Norway. Quaternary Science Reviews 21, 1661-1676. Lohne, Ø.S., 2007. Late Weichselian relative sea-level changes and glacial history in

  20. Subsistence economy of el paraiso, an early peruvian site.

    PubMed

    Quilter, J; E, B O; Pearsall, D M; Sandweiss, D H; Jones, J G; Wing, E S

    1991-01-18

    Studies of food remains from the Preceramic monumental site of E1 Paraíso, Peru (1800 to 1500 B.C.), have shed new light on a debate regarding the relative importance of seafood versus terrestrial resources and the role of cultigens in subsistence economies during the early development of Peruvian civilization. Fish was the primary animal food at the site whereas plant foods consisted of a mixture of cultivated resources (squashes, beans, peppers, and jicama) with an additional reliance on fruits (guava, lucuma, and pacae). Wild plants, especially the roots of sedges and cat-tail, also may have accounted for a substantial part of the diet. Cotton was a chief crop, used in making fishing tackle and the textiles that served as clothing and items of high value and status. As an example of the beginnings of civilization, El Paraíso is a case in which impressive architecture was built on a relatively simple subsistence economy and energy was expended in the production of resources useful in local and regional exchange systems. PMID:17733284

  1. Latest Pleistocene and Holocene Glacier Fluctuations in southernmost Patagonia

    NASA Astrophysics Data System (ADS)

    Menounos, B.; Maurer, M.; Clague, J. J.; osborn, G.; Ponce, F.; Davis, P. T.; Rabassa, J.; Coronato, A.; Marr, R.

    2011-12-01

    Summer insolation has been proposed to explain long-term glacier fluctuations during the Holocene. If correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Testing this insolation hypothesis has been hampered by dating uncertainties of many Holocene glacier chronologies from Patagonia. We report on our ongoing research aimed at developing a regional glacier chronology at the southern end of the Andes north and west of Ushuaia, Argentina. We have found evidence for an advance of cirque glaciers at the end of the Pleistocene; one or locally two closely spaced moraines extend up to 2 km beyond Little Ice Age moraines. Radiocarbon dating of terrestrial macrofossils recovered from basal sediments behind two of these moraines yielded ages of 10,320 ± 25 and 10,330 ± 30 14C yr BP. These moraines may record glacier advances coeval with the Antarctic Cold Reversal; surface exposure dating of these moraines is currently in progress to test this hypothesis. We find no evidence of Holocene moraines older than 6800 14C yr BP, based on the distribution of Hudson tephra of that age. At some sites, there is evidence for an early Neoglacial advance of glaciers slightly beyond (< 0.5 km) Little Ice Age limits. Terrestrial macrofossils at the upper contact of basal till from one site yielded an age of 4505 ± 30 14C yr BP; this age overlaps the most probable age range of early Neoglacial ice expansion in southern Patagonia reported by Porter (2000) and the age of plants killed by expansion of the Quelccaya Ice Cap in Peru. We have documented multiple wood mats with stumps in growth position separated by till units in a 100 m section of the northeast lateral moraine at Stoppani Glacier (54.78 S, 68.98 W), 50 km west of Ushuaia. Ten radiocarbon ages on these wood mats range in age from 3510 ± 15 to 135 ± 15 14C yr BP. The mats decrease in age up-section; many overlap with published age ranges for

  2. Discovery of laterally extensive drape of siliciclastic silt in the Northern Calcareous Alps, Austria: Late-glacial to ?early Holocene aeolian deposition.

    NASA Astrophysics Data System (ADS)

    Gild, Charlotte; Geitner, Clemens; Haas, Jean Nicolas; Sanders, Diethard

    2016-04-01

    Field surveys in the Northern Calcareous Alps (NCA, a nappe stack of Triassic carbonate rocks) revealed a drape, or drapes, typically 20-40 cm in thickness of siliciclastic silt over extensive landscape areas, from valley floors to LGM (Last Glacial Maximum) nunataks. The drape veneers substrates ranging from country rocks to diverse post-LGM deposits - the latter with depositional and/or erosional topographies. The drape mostly is overlain by vegetated organic material and, in turn, tops inactive/abandoned post-LGM successions of fluvial (including kame terrace), alluvial fan, scree slope, LGM basal till, and rock-avalanche origin. The drape extends over kilometers at least (limit of field investigation in specific areas), up to LGM nunatak plateaus. Deposystems (e.g., scree slopes, alluvial fans) on carbonate-rocky terrain that remained active until the Holocene are not topped by the drape; a level of siliciclastic silt, however, was spotted within a few of these successions. The possibility that several levels of silt are intercalated within or top post-glacial deposits cannot be excluded at present; the large lateral extent and the stratigraphic position, however, suggest that at least most locations pertain to a single widespread level (with that reservation, we prefer to speak in singular of the drape). Over the inspected area (~ 90 x 20 km), the drape consists mainly of silt-sized grains of quartz, feldspars, micas, and amphiboles; at a few sites, calci- or dolosilt are admixed. Most of the grains are angular to subrounded, some grains show features of corrosion. Preliminary palynological analyses of this silt - seven locations from LGM nunataks to kame terrace and alluvial fans - suggest vegetation types that, together, may be assigned to palaeoclimates ranging from the late-glacial (Younger Dryas?) to the middle Holocene. A few of the pollen spectra appear to record sparse vegetation cover allowing for enhanced aeolian deposition, but other spectra (e

  3. Global Change in the Holocene

    NASA Astrophysics Data System (ADS)

    Alverson, Keith

    2004-05-01

    Many people, even perhaps the occasional Eos reader, associate the term ``global change'' with warming caused by mankind's recent addiction to fossil fuels. Some may also be well aware of enormous global changes in the distant past uninfluenced by humans; for example, Pleistocene ice ages. But was there any ``global change'' between the end of the last ice age and the onset of industrialization? The answer to this question is addressed early-in the title, even-in the new book Global Change in the Holocene. I don't suggest anyone stop reading after the title, though; the rest of the book is both highly informative and a real pleasure to read. The opening chapter tells us that the Holocene is certainly not, as sometimes charged, a ``bland, pastoral coda to the contrasted movements of a stirring Pleistocene symphony.'' Rather, it is a ``period of continuous change.'' Melodious language aside, the combination of sustained and high-amplitude climatic variability and a wealth of well-preserved, precisely datable paleoclimate archives make the Holocene unique. Only by studying the Holocene can we hope to unravel the low-frequency workings of the Earth system and the degree to which humans have changed our world. This book sets out to teach the reader how to obtain the relevant data and how to use it to do much more than showing static analogues of possible future climate states. It challenges researchers to discern in their data the effects of the dynamic processes underlying coupled variability in the Earth's climate and ecosystems. These processes continue to act today, and it is through providing an understanding of these system dynamics in the Holocene that paleo-environmental studies can make the greatest contribution to future-oriented concerns.

  4. Holocene precipitation changes in the deep tropics recorded by Speleothems (Invited)

    NASA Astrophysics Data System (ADS)

    Wang, X.; Auler, A. S.; Edwards, R.; Kong, X.; Cheng, H.; Cruz, F. W.; Wang, Y.; Broecker, W. S.

    2010-12-01

    We have obtained a high-resolution oxygen isotope (δ18O) record of cave calcite from Paraiso Cave, eastern Amazon, which covers most of the Holocene. Its chronology was determined by U-Th ages from three column-shaped stalagmites. Their δ18O profiles replicate among their contemporaneous growth periods. Therefore, the samples were likely precipitated under equilibrium conditions and their oxygen isotopic variations are primarily caused by climate change. We find that the δ18O decreases steadily from ~11.0 to 5.0 thousand years ago, with a growth gap between ~8.4 to 6.3 thousand years ago, and then gradually increases until the present. The large amplitude of the δ18O change (up to 4 per mil) suggests that the variation in δ18O value is dominated by meteoric precipitation change at this equatorial site. In order to investigate the interactions between the Intertropical Convergence Zone (ITCZ), monsoons and El Niño-Southern Oscillation (ENSO) activity during the Holocene, we compare the Paraiso record to speleothem records from other locations in the deep tropics, namely, cave sites from Flores, Borneo and Peru. We find that all these speleothem records are consistent, with a progressive δ18O decrease (rainfall increase) during the early Holocene, probably in response to the southward retreat of the ITCZ from its northernmost location in the early Holocene. This is evident from the strong anti-correlation between the speleothem monsoonal records from China and southern Brazil. However, our record is distinct from the others during the last 4 thousand years, when it switches to a continuous δ18O increase (rainfall decrease) trend, while the others flatten out. We propose that, during the late Holocene, the strengthened South American Summer Monsoon may override the ENSO influence and cause the discrepancy in precipitation between eastern Amazon and other deep tropical cave sites.

  5. Vegetation Response to Holocene Variations in Climate and Fire Activity in Southwestern Oregon

    NASA Astrophysics Data System (ADS)

    White, A.; Briles, C.; Whitlock, C. L.

    2014-12-01

    Past ecosystem responses to fire and climate change have been well studied in many parts of the Pacific Northwest, but forest history of the southern Cascades is poorly understood. Pollen and charcoal records from Hobart Lake (42.099°N, 122.482°W, 1458m) in southwestern Oregon were analyzed to reconstruct past changes in vegetation and fire activity. The watershed today supports mixed conifer forest of Abies, Pseudotsuga, Cupressaceae, and Pinus. From 8000 to 3500 cal yr BP, the forest had more xerophytic species, such as Pinus and Cupressaceae, and higher frequency of fires than at present, suggesting a climate that was warmer and drier than current conditions. The last 3500 cal years was characterized by increasing mesophytic taxa, such as Abies and Pseudotsuga, and decreasing fire activity; these trends are consistent with the establishment of cooler wetter conditions in the late Holocene. Changes in the abundance of Abies and Pseudotsuga pollen were compared at multiple sites to better understand their history in relation to long-term variations in climate and local disturbance. The pollen record suggests that Abies (i.e., Abies concolor, A. magnifica, A. amabilis or A. grandis) was abundant during the late-glacial period in a widespread subalpine forest that was present at all elevations. The genus declined in abundance during the early Holocene when it was best represented at higher elevations. Abies species gradually became more widespread and abundant during the mid- and late Holocene consistent with cooler conditions and expansion of closed mesic forest. Pseudotsuga was most abundant at low-elevation sites in the Coast and Cascade ranges during the early Holocene and then most abundant in more southern, mid-elevation sites in the Klamath and southern Cascade ranges in the late Holocene. Thus, the regional conifer history was strongly governed by variations in the summer insolation as they relate to changes in summer effective moisture.

  6. Holocene temperature shifts around Greenland: Paleolimnological approaches to quantifying past warmth and documenting its consequences

    NASA Astrophysics Data System (ADS)

    Axford, Y.; Lasher, G. E.; McFarlin, J. M.; Francis, D. R.; Kelly, M. A.; Langdon, P. G.; Levy, L.; Osburn, M. R.; Osterberg, E. C.

    2015-12-01

    Insolation-driven warmth across the Arctic during the early to middle Holocene (the Holocene Thermal Maximum, or HTM) represents a geologically accessible analog for future warming and its impacts. Improved constraints on the magnitude and seasonality of HTM warmth around Greenland's margins can advance the use of paleoclimate data to test and improve climate and ice sheet models. Here we present an overview of our recent efforts to reconstruct climate through the Holocene around the margins of the Greenland Ice Sheet using multiple proxies in lake sediments. We use insect (chironomid) assemblages to derive quantitative estimates of Holocene temperatures at sites with minimal soil and vegetation development near the eastern, northwestern and western margins of the ice sheet. Our chironomid-based temperature reconstructions consistently imply HTM July air temperatures 3 to 4.5 °C warmer than the pre-industrial late Holocene in these sectors of Greenland. The timing of reconstructed peak warmth differs between sites, with onset varying from ~10 ka to ~6.5 ka, but in good agreement with glacial geology and other evidence from each region. Our reconstructed temperature anomalies are larger than those typically inferred from annually-integrated indicators from the ice sheet itself, but comparable to the few other quantitative summer temperature estimates available from beyond the ice sheet on Greenland. Additional records are needed to confirm the magnitude of HTM warmth and to better define its seasonality and spatial pattern. To provide independent constraints on paleotemperatures and to elucidate additional aspects of Holocene paleoclimate, we are also employing oxygen isotopes of chironomid remains and other aquatic organic materials, and molecular organic proxies, in parallel (see Lasher et al. and McFarlin et al., this meeting). Combined with glacial geologic evidence, these multi-proxy records elucidate diverse aspects of HTM climate around Greenland - including

  7. An unusual early Holocene diatom event north of the Getz Ice Shelf (Amundsen Sea): Implications for West Antarctic Ice Sheet development

    NASA Astrophysics Data System (ADS)

    Esper, O.; Gersonde, R.; Hillenbrand, C.; Kuhn, G.; Smith, J.

    2011-12-01

    Modern global change affects not only the polar north but also, and to increasing extent, the southern high latitudes, especially the Antarctic regions covered by the West Antarctic Ice Sheet (WAIS). Consequently, knowledge of the mechanisms controlling past WAIS dynamics and WAIS behaviour at the last deglaciation is critical to predict its development in a future warming world. Geological and palaeobiological information from major drainage areas of the WAIS, like the Amundsen Sea Embayment, shed light on the history of the WAIS glaciers. Sediment records obtained from a deep inner shelf basin north of Getz Ice Shelf document a deglacial warming in three phases. Above a glacial diamicton and a sediment package barren of microfossils that document sediment deposition by grounded ice and below an ice shelf or perennial sea ice cover (possibly fast ice), respectively, a sediment section with diatom assemblages dominated by sea ice taxa indicates ice shelf retreat and seasonal ice-free conditions. This conclusion is supported by diatom-based summer temperature reconstructions. The early retreat was followed by a phase, when exceptional diatom ooze was deposited around 12,500 cal. years B.P. [1]. Microscopical inspection of this ooze revealed excellent preservation of diatom frustules of the species Corethron pennatum together with vegetative Chaetoceros, thus an assemblage usually not preserved in the sedimentary record. Sediments succeeding this section contain diatom assemblages indicating rather constant Holocene cold water conditions with seasonal sea ice. The deposition of the diatom ooze can be related to changes in hydrographic conditions including strong advection of nutrients. However, sediment focussing in the partly steep inner shelf basins cannot be excluded as a factor enhancing the thickness of the ooze deposits. It is not only the presence of the diatom ooze but also the exceptional preservation and the species composition of the diatom assemblage

  8. Holocene coastal glaciation of Alaska

    NASA Astrophysics Data System (ADS)

    Calkin, Parker E.; Wiles, Gregory C.; Barclay, David J.

    2001-01-01

    Holocene fluctuations of the three cirque glaciers on the Seward Peninsula and five groups of tidewater- and land-terminating glaciers along the northernmost Gulf of Alaska, provide a proxy record of late Holocene climatic change. Furthermore, the movements of the coastal glaciers were relevant to late Holocene native American migration. The earliest expansion was recorded about 6850 yr BP by Hubbard Glacier at the head of Yakutat Bay in the Gulf of Alaska; however, its down-fjord advance to the bay mouth was delayed until ˜2700 BP. Similarly, expansions of the Icy Bay, Bering, and McCarty glaciers occurred near their present termini by ˜3600-3000 BP, compatible with marked cooling and precipitation increases suggested by the Alaskan pollen record. Decrease in glacier activity ˜2000 BP was succeeded by advances of Gulf coastal glaciers between 1500 and 1300 BP, correlative with early Medieval expansions across the Northern Hemisphere. A Medieval Optimum, encompassing at least a few centuries prior to AD 1200 is recognized by general retreat of land-terminating glaciers, but not of all tidewater glaciers. Little Ice Age advances of land-based glaciers, many dated with the precision of tree-ring cross-dating, were centered on the middle 13th or early 15th centuries, the middle 17th and the last half of the 19th century A.D. Strong synchrony of these events across coastal Alaska is evident.

  9. Holocene ice dynamics and bottom-water formation associated with Cape Darnley polynya activity recorded in Burton Basin, East Antarctica

    NASA Astrophysics Data System (ADS)

    Borchers, Andreas; Dietze, Elisabeth; Kuhn, Gerhard; Esper, Oliver; Voigt, Ines; Hartmann, Kai; Diekmann, Bernhard

    2016-03-01

    A multi-proxy study including sedimentological, mineralogical, biogeochemical and micropaleontological methods was conducted on sediment core PS69/849-2 retrieved from Burton Basin, MacRobertson Shelf, East Antarctica. The goal of this study was to depict the deglacial and Holocene environmental history of the MacRobertson Land-Prydz Bay region. A special focus was put on the timing of ice-sheet retreat and the variability of bottom-water formation due to sea ice formation through the Holocene. Results from site PS69/849-2 provide the first paleo-environmental record of Holocene variations in bottom-water production probably associated to the Cape Darnley polynya, which is the second largest polynya in the Antarctic. Methods included end-member modeling of laser-derived high-resolution grain size data to reconstruct the depositional regimes and bottom-water activity. The provenance of current-derived and ice-transported material was reconstructed using clay-mineral and heavy-mineral analysis. Conclusions on biogenic production were drawn by determination of biogenic opal and total organic carbon. It was found that the ice shelf front started to retreat from the site around 12.8 ka BP. This coincides with results from other records in Prydz Bay and suggests warming during the early Holocene optimum next to global sea level rise as the main trigger. Ice-rafted debris was then supplied to the site until 5.5 cal. ka BP, when Holocene global sea level rise stabilized and glacial isostatic rebound on MacRobertson Land commenced. Throughout the Holocene, three episodes of enhanced bottom-water activity probably due to elevated brine rejection in Cape Darnley polynya occured between 11.5 and 9 cal. ka BP, 5.6 and 4.5 cal. ka BP and since 1.5 cal. ka BP. These periods are related to shifts from warmer to cooler conditions at the end of Holocene warm periods, in particular the early Holocene optimum, the mid-Holocene warm period and at the beginning of the neoglacial. In

  10. Holocene and latest Pleistocene climate and glacier fluctuations in Iceland

    NASA Astrophysics Data System (ADS)

    Geirsdóttir, Áslaug; Miller, Gifford H.; Axford, Yarrow; Ólafsdóttir, Sædís

    2009-10-01

    Multiproxy climate records from Iceland document complex changes in terrestrial climate and glacier fluctuations through the Holocene, revealing some coherent patterns of change as well as significant spatial variability. Most studies on the Last Glacial Maximum and subsequent deglaciation reveal a dynamic Iceland Ice Sheet (IIS) that responded abruptly to changes in ocean currents and sea level. The IIS broke up catastrophically around 15 ka as the Polar Front migrated northward and sea level rose. Indications of regional advance or halt of the glaciers are seen in late Alleröd/early Younger Dryas time and again in PreBoreal time. Due to the apparent rise of relative sea level in Iceland during this time, most sites contain evidence for fluctuating, tidewater glacier termini occupying paleo fjords and bays. The time between the end of the Younger Dryas and the Preboreal was characterized by repeated jökulhlaups that eroded glacial deposits. By 10.3 ka, the main ice sheet was in rapid retreat across the highlands of Iceland. The Holocene thermal maximum (HTM) was reached after 8 ka with land temperatures estimated to be 3 °C higher than the 1961-1990 reference, and net precipitation similar to modern. Such temperatures imply largely ice-free conditions across Iceland in the early to mid-Holocene. Several marine and lacustrine sediment climate proxies record substantial summer temperature depression between 8.5 and 8 ka, but no moraines have been detected from that time. Termination of the HTM and onset of Neoglacial cooling took place sometime after 6 ka with increased glacier activity between 4.5 and 4.0 ka, intensifying between 3.0 and 2.5 ka. Although a distinct warming during the Medieval Warm Period is not dramatically apparent in Icelandic records, the interval from ca AD 0 to 1200 is commonly characterized by relative stability with slow rates of change. The literature most commonly describes Little Ice Age moraines (ca AD 1250-1900) as representing the

  11. Late Pleistocene and Holocene Fire History of the California Islands

    NASA Astrophysics Data System (ADS)

    Scott, A. C.; Hardiman, M.; Pinter, N.; Anderson, R.

    2013-12-01

    Charcoal has been recovered from a range of late Pleistocene and Holocene sites on Santa Cruz Island and Santa Rosa Island, both islands part of California's Northern Channel Islands, U.S.A. Sediments have been dated using radiocarbon measurements based on wood charcoal, fungal sclerotia, glassy carbon and fecal pellets and are given as calendar years BP. This charcoal has been used to interpret the fire history of the Islands. Charcoal assemblages from samples dating from 24,690 to 12,900 years are dominated by coniferous wood charcoal. Little angiosperm charcoal was recovered in any of the samples. Fungal sclerotia are frequent in a number of samples from a range of ages both on Santa Cruz and Santa Rosa. Fecal pellets are common in most samples and abundant in others. Some of the fecal pellets have hexagonal sides and are likely to represent termite frass. The sediments are fluvial in origin and the distribution of charcoal is irregular making interpretation of fire return intervals and fire frequency difficult. The charcoal indicates a significant record of fire before the earliest documented human arrival on the islands. Charcoal reflectance data shows the occurrence of predominantly low temperature charcoals suggesting common surface fires in the coniferous forest. Soledad Pond sediments from Santa Rosa Island (Anderson et al., 2010) dating from 11,800 cal years BP show a distinctively different vegetation dominated by angiosperms and showing a very different fire history. Pinus stands, coastal sage scrub dominated by Baccharis sp. and grassland replaced the conifer forest as the climate warmed. The early Holocene became increasingly drier, particularly after ca. 9150 cal yr BP. By ca. 6900 cal yr BP grasslands recovered. Introduction of non-native species by ranchers occurred subsequent to AD 1850. Charcoal influx is high early in the Soledad Pond record, but declines during the early Holocene when minimal biomass suggests extended drought. A general

  12. What can we learn about an early human influence on the global methane cycle from bipolar atmospheric CH4, δD(CH4) and δ13CH4 measurements during the Holocene

    NASA Astrophysics Data System (ADS)

    Beck, Jonas; Bock, Michael; Schmitt, Jochen; Seth, Barbara; Blunier, Thomas; Fischer, Hubertus

    2015-04-01

    The past variation of the concentration of atmospheric methane (CH4) is observed to be generally in phase with the northern summer insolation cycle driven by the precession of the rotation axis of the Earth. However, in the mid-Holocene this regularity breaks down, and atmospheric CH4 starts to rise while the northern summer insolation continues to decline. Despite different attempts to explain this feature (e.g. contrasting hypotheses on early human influences or enhanced natural emissions in the southern tropics), an unambiguous explanation of the evolution of the atmospheric methane concentration has not yet been found. In addition to the inter-polar difference (IPD) of methane, allowing us to draw conclusions about the hemispheric imbalance of the source and sink distribution, the isotopic composition (δD and δ13C) of atmospheric CH4 provides further information about the methane cycle. Each source emits methane of a typical isotope signature, and each sink process leads to a certain isotopic fractionation and, thus, influences the isotopic composition of atmospheric methane. To exploit the full parameter set, we measured the methane isotopes on ice cores from both polar regions (NGRIP from Greenland; EDML and Talos Dome from Antarctica) and are able to calculate the inter-polar difference of δD (IPDδD) and δ13C (IPDδ13C) of methane over the Holocene. To avoid systematic errors, the samples from both hemispheres have been measured on the same system and during the same measurement campaign for each parameter. The NGRIP δD data show a clear covariation with the long-term changes in CH4 concentrations during the Holocene. The δD variations of 8-10 o are significantly larger than our measurement error of 2.3 o. However, the resulting IPDδD is constant within the measurement error at approximately -16.5 o (north-south) during the entire Holocene. The δ13C records (with a measurement precision of 0.13 o) show a clear decrease in δ13C of about 1.9 o and an

  13. Holocene sea-level changes in the Falkland Islands

    NASA Astrophysics Data System (ADS)

    Newton, Tom; Gehrels, Roland; Daley, Tim; Long, Antony; Bentley, Mike

    2014-05-01

    In many locations in the southern hemisphere, relative sea level (RSL) reached its maximum position during the middle Holocene. This highstand is used by models of glacial isostatic adjustment (GIA) to constrain the melt histories of the large ice sheets, particularly Antarctica. In this paper we present the first Holocene sea-level record from the Falkland Islands (Islas Malvinas), an archipelago located on the Patagonian continental shelf about 500 km east of mainland South America at a latitude of ca. 52 degrees. Unlike coastal locations in southernmost South America, Holocene sea-level data from the Falklands are not influenced by tectonics, local ice loading effects and large tidal ranges such that GIA and ice-ocean mass flux are the dominant drivers of RSL change. Our study site is a salt marsh located in Swan Inlet in East Falkland, around 50 km southwest of Stanley. This is the largest and best developed salt marsh in the Falkland Islands. Cores were collected in 2005 and 2013. Lithostratigraphic analyses were complemented by analyses of foraminifera, testate amoebae and diatoms to infer palaeoenvironments. The bedrock, a Permian black shale, is overlain by grey-brown organic salt-marsh clay, up to 90 cm thick, which, in a landward direction, is replaced by freshwater organic sediments. Overlying these units are medium-coarse sands with occasional pebbles, up to 115 cm thick, containing tidal flat foraminifera. The sandy unit is erosively overlain by a grey-brown organic salt-marsh peat which extends up to the present surface. Further away from the sea this unit is predominantly of freshwater origin. Based on 13 radiocarbon dates we infer that prior to ~9.5 ka sea level was several metres below present. Under rising sea levels a salt marsh developed which was suddenly drowned around 8.4 ka, synchronous with a sea-level jump known from northern hemisphere locations. Following the drowning, RSL rose to its maximum position around 7 ka, less than 0.5 m above

  14. Millennial Scale Variability of the AMOC and its Link to Climate During the Holocene

    NASA Astrophysics Data System (ADS)

    Thornalley, D. J.; Oppo, D.; Keigwin, L. D.; Hall, I. R.; Moffa Sanchez, P.

    2014-12-01

    Several proxy and modelling studies suggest that there may have been considerable change in the operation the Atlantic Meridional Overturning Circulation (AMOC) during the Holocene. Yet despite its importance for regional and global climate, the Holocene history of the AMOC is poorly constrained. Improving our knowledge of past AMOC variability will contribute to our general understanding of the dynamics of ocean circulation and the role it may play in causing or amplifying climate variability on millennial timescales. We present Holocene grain-size records in depth transects from Blake Outer Ridge and Cape Hatteras, sampling the full-depth range of the Deep Western Boundary Current (DWBC), the lower limb of the AMOC. These records will complement a depth-transect of grain-size records sampling the Iceland-Scotland (I-S) overflow, showing Holocene variations that reflect deglacial meltwater forcing in the early Holocene and insolation-forced trends from the middle-to-late Holocene (Thornalley et al., 2013, Climate of the Past). We will also present detailed grain-size records for the last 2,000 years, both in a depth transect of cores off Cape Hatteras, and from cores in the Iceland Basin, sampling the I-S overflow. Our extensive datasets enable us to provide a coherent synthesis of changes in the flow strength of key components of the AMOC on centennial-millennial and orbital timescales, which we can use to develop our understanding of past millennial-scale climate variability. Specific questions to be addressed include: How well coupled are Holocene trends in Iceland-Scotland overflow and the DWBC? How did I-S overflow and the AMOC vary during the last millennia, including the last ~150 years since the end of the Little Ice Age? Initial results suggest a long-term anti-phasing of the Nordic overflows, wherein mid-late Holocene weakening of the I-S overflow has been compensated for by a strengthening of Denmark Strait overflow. We will also report on pronounced

  15. Holocene rock varnish microstratigraphy and its chronometric application in the drylands of western USA

    NASA Astrophysics Data System (ADS)

    Liu, Tanzhuo; Broecker, Wallace S.

    2007-02-01

    Analyses of hundreds of rock varnish samples from latest Pleistocene and Holocene geomorphic features in the drylands of western USA reveal a regionally replicable Holocene microlamination sequence. This sequence consists of 12 approximately evenly spaced weak dark layers intercalated with 13 orange/yellow layers. Preliminary radiometric age calibration indicates that six dark layers in the upper portion of the sequence were deposited during the last 6000 yr, diagnostic of the Little Ice Age and late Holocene wet events; five dark layers in the lower portion of the sequence were deposited after the termination of the Pleistocene but slightly before 7000 YBP, indicative of the early Holocene wet events; and one dark layer in the middle portion of the sequence was deposited around 6500 YBP, suggestive of the middle Holocene wet phase. Our age calibration further indicates that the Holocene wet events represented by the dark layers largely correlate in time with the millennial-scale Holocene cooling events in the North Atlantic region. This radiometrically calibrated and climatically correlated Holocene microlamination sequence was then used as a unique correlative dating tool to determine surface exposure ages of geomorphic and geoarchaeological features in western USA deserts. The varnish microlamination (VML) dating of debris flow fan deposits in Death Valley, California, yields minimum ages of 12,500, 12,500-11,100, 11,100, 10,300, 9400, and 2800 YBP for six debris flow fan building events, suggesting that such events were more likely to have occurred during relatively wet periods of the Holocene. The VML dating of a prehistoric grinding stone from Chili of northern New Mexico yields a minimum age of 900-1100 YBP for the abandonment of this occupation site by the Anasazi Indians. The VML dating of a prehistoric flaked stone (a primary core) from Ocotillo, southern California, yields a minimum age of 12,500 YBP for the flaking of this stone artifact, suggesting at

  16. Using Macroscopic Charcoal to Reconstruct the Holocene Fire Activity of the Willamette Valley, Oregon and Washington

    NASA Astrophysics Data System (ADS)

    Walsh, M. K.; Whitlock, C.; Bartlein, P. J.; Pearl, C. A.

    2006-12-01

    High-resolution macroscopic charcoal analysis of two lacustrine records has revealed the Holocene fire activity of the Willamette Valley, located between the Coast and Cascade ranges of southwestern Washington and northwestern Oregon. The Willamette Valley experienced major environmental and cultural changes during the Holocene, however, its long-term fire history is poorly known. Of particular interest are shifts in fire activity that occurred in response to (1) millennial- and centennial-scale climate and vegetation changes (e.g., the Early Holocene warm period, the Little Ice Age) and (2) major shifts in human activity and population size (e.g., Native American population decline, Euro-American settlement). Macroscopic charcoal analysis of contiguous core samples was used to reconstruct fire activity at each site. Charcoal source (i.e., herbaceous or woody) was also determined based on particle morphology. Charcoal influx was decomposed into a peak component (which indicates fire episodes) and a background component (which indicates changes in burnable biomass). Charcoal records from Battle Ground Lake and Beaver Lake reveal major shifts in fire activity that are consistent with known changes in regional climate on orbital time scales. The Battle Ground Lake charcoal data, for example, show a general increase in fire frequency from the beginning of the Holocene to a maximum of ~18 fire episodes/1000 years at 6500 cal yr BP, associated with the early Holocene insolation maximum and its influence on summer drought, followed by a decrease to ~5 fire episodes/1000 years at present. Similar trends are indicated by the Beaver Lake charcoal data. Both records also indicate shifts in fire activity that suggest the possibility of anthropogenic burning, but at different times at each site. Additional records are being analyzed to examine the spatial and temporal patterns of fire activity across the Willamette Valley as a whole.

  17. Climate of Late Glacial and Early Holocene in Southern Slovakia reconstructed on the basis of high resolution stable isotope record from cave speleothem

    NASA Astrophysics Data System (ADS)

    Gąsiorowski, Michał; Hercman, Helena; Pawlak, Jacek; Gradziński, Michał; Bella, Pavel

    2015-04-01

    The Central Europe is a key region to understand climate variability (temperature, precipitation, air circulation, NAO index etc.) in Europe during post-LGM period. We studied stable isotopic record from 826 mm long stalagmite collected in the Jaskyňa na Kečovských Lúkach cave located in the Slovakian Karst. The record was precisely dated with 230Th/U dating method using mass spectrometry. Age-depth model was calculated using MOD-AGE software. Stable isotope record cover time from the termination of LGM (~21 kry) until the Holocene climate optimum (~7 kyr). Changes of 18O concentration indicated rapid warming around 20.5 kyr. After that, oxygen isotopes oscillated with millennial mode similar to Bond events. The specific peak of lighter and heavier oxygen isotope composition correlated with cold and warm period of the Late Glacial, i.e. the Older and the Younger Dryas, the Bølling and the Allerød oscillations, respectively. Much stronger excursion to the heavier values of delta 18O indicates beginning of the Holocene. The Bond events can be also identified during the Holocene and next rapid change to the lighter oxygen isotopic composition point to the 8.2 kyr cold event. The carbon isotope composition correlates negatively with oxygen isotope record, with much heavier carbon during LGM and lighter carbon signal ~17 kyr and on the beginning of the Holocene. The correlation between speleothem record and Greenland ice core records suggests that climate of Southern Sloviaka after the LGM was formed mainly by Atlantic air circulation with significant Mediterranean influences during Late Glacial.

  18. Holocene Lake Records on Kamchatka

    NASA Astrophysics Data System (ADS)

    Diekmann, Bernhard; Biskaborn, Boris; Chapligin, Bernhard; Dirksen, Oleg; Dirksen, Veronika; Hoff, Ulrike; Meyer, Hanno; Nazarova, Larisa

    2014-05-01

    palaeoecologocal responses in different lake systems under same climatic boundary conditions. Our findings give evidence of longterm climate changes that suggest the existence of a warm and humid early Holocene climate optimum between roughly 9.0 and 4.5 ka BP, followed by climate deterioration of the neoglacial epoch in concert with summer cooling, glacial advances, and enhanced continentality. Two strong cooling episodes punctuated late Holocene climate development between 4.5 and 3.5 ka BP and during the last millennium, marking the prelude of neoglacial cooling and the Little Ice Age. This general development of Holocene climate on Kamchatka is in line with environmental changes in the neighbouring Sea of Okhotsk, where the pattern of sea-ice dynamics is consistent with early Holocene warmth and Neoglacial climate cooling. While the marine records from the Sea of Okhotsk mainly reflect winter conditions, our findings show that summer climate on Kamchatka shows a similar trend of temporal change. Holocene climate variability on Kamchatka was mainly driven by external insolation forcing, changes in solar activity, and internal climate forcing. The latter is dictated by by the relative position of the Aleutan Low in response to the prevailing modes of Pacific Decadal Oscillation and the Arctic Oscillation that both control the influence of maritime or continental air masses and the intensity of rain- or snow-bringing cyclones.

  19. Holocene Enviromental Changes in AN Amazonian Floodplain Lake

    NASA Astrophysics Data System (ADS)

    Moreira, L.; Moreira-Turcq, P. F.; Turcq, B.; Cordeiro, R. C.

    2011-12-01

    The floodplains lakes are built due to the fluctuations in the level of the rivers, which causes the formation of bars and accumulation of sediment carried by the rivers and its tributaries. Thus, significant quantities of organic matter can accumulate within these lakes that might represent important carbon sinks. The organic sedimentation process in the floodplains remains unknown as well as very little is known about past conditions in the Amazonian floodplains. Because these gaps, the aim of this work is to provide, through sedimentological, mineralogical and organic geochemical analysis of a 124-cm long core collected in Lago Comprido (eastern Amazonia), evidences of paleoenviromental changes during the Holocene. The core COM1 was analysed using radiocarbon dates, organic carbon concentration, C/N ratio, delta 13C and diatoms. The core points out different sedimentary environments that occurs in the last 9900 years cal BP. The record is divided into three phases: - phase III (124-94 cm, 9900 to 3200 cal years BP): this interval is characterized by delta 13C values typical of graminea, suggesting dry conditions with longer low water levels of the Amazon River. Supporting evidence for driest conditions during this period comes from low organic carbon values due to oxidation and absence of diatoms in the sediment. The carbon flux was very low, reaching an average of 0.9 g C/m2/year. - phase II (93-46 cm, 3200 to 940 years cal BP): increasing lake level beginning in this phase. The delta 13C values ranged between -25% and -29%, which are thought to represent terrestrial plants. This may indicate the presence of a flooded vegetation in this site. The freshwater planktonic diatoms Aulacoseira sp start to increase in this phase, additional evidence that the period of the annual high water stands was probably longer than before. Carbon flux increases, reaching an average of 5 g C/m2/year. - phase I (45-0cm, < 940 years cal BP): the delta 13C values and CN ratios did

  20. Soil and Rock Physical Properties at the Mars Exploration Rover Landing Sites: Early Returns

    NASA Technical Reports Server (NTRS)

    Ming, D. W.; Anderson, R. C.; Arvidson, R. E.; Bell, J. F., III; Biesiadecki, J.; Christensen, P. H.; Gorevan, S. P.; Ehlmann, B. L.; Guinness, E. A.; Graff, T. G.

    2004-01-01

    The purpose of this paper is to report the 'early returns' on the physical properties of soil units and rocks at the MER landing sites. Because we are still very early in the mission at Meridiani Planum, results from the Gusev Crater Landing Site are emphasized here.

  1. 10 CFR Appendix Q to Part 50 - Pre-Application Early Review of Site Suitability Issues

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Pre-Application Early Review of Site Suitability Issues Q Appendix Q to Part 50 Energy NUCLEAR REGULATORY COMMISSION DOMESTIC LICENSING OF PRODUCTION AND UTILIZATION FACILITIES Pt. 50, App. Q Appendix Q to Part 50—Pre-Application Early Review of Site Suitability Issues...

  2. 10 CFR Appendix Q to Part 50 - Pre-Application Early Review of Site Suitability Issues

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Pre-Application Early Review of Site Suitability Issues Q Appendix Q to Part 50 Energy NUCLEAR REGULATORY COMMISSION DOMESTIC LICENSING OF PRODUCTION AND UTILIZATION FACILITIES Pt. 50, App. Q Appendix Q to Part 50—Pre-Application Early Review of Site Suitability Issues This appendix sets out procedures...

  3. Reconstructing Holocene palaeo-environmental conditions in the Baltic: A multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059)

    NASA Astrophysics Data System (ADS)

    Kotthoff, Ulrich; Andrén, Elinor; Andrén, Thomas; Ash, Jeanine; Bauersachs, Thorsten; Fanget, Anne-Sophie; Granoszewski, Wojciech; Groeneveld, Jeroen; Krupinski, Nadine; Peyron, Odile; Slomp, Caroline; Stepanova, Anna; Warnock, Jonathan; van Helmond, Niels; Expedition 347 Science Party

    2016-04-01

    Some of the largest marine environmental impacts from ongoing global climate change are occurring in continental shelf seas and enclosed basins, including severe oxygen depletion, intensifying stratification, and increasing temperatures. In order to predict future changes in water mass conditions, it is essential to reconstruct how these conditions have changed in the past against the background of climate changes. The brackish Baltic Sea is one of the largest semi-enclosed basins worldwide, and its sediment records provide a unique opportunity to analyse palaeo-environmental and climate change in central and northern Europe. IODP Expedition 347 recovered an exceptional set of sediment cores from the Baltic Sea which allow high-resolution reconstructions in unprecedented quality. We present a comparison of commonly-used proxies to reconstruct palaeoecosystems, -temperatures, and -salinity from IODP Site M0059 in the Little Belt over the past ˜8000 years. Our aim is to reconstruct the development of the terrestrial and marine ecosystems in the research area and the related environmental conditions, and to identify potential limitations of individual proxies. The age model for Site M0059 is based on 14Cdating, biostratigraphic correlation with neighbouring terrestrial pollen records, and sediment stratigraphy. Sedimentary organic carbon content and the bulk elemental composition have been measured, and can be used to determine the depositional environment and degree of oxygen depletion (e.g., Mo, Corg/Ptot). Pollen is used as proxy for vegetation development in the hinterland of the southern Baltic Sea and as a land/air-temperature proxy. Comparison with dinoflagellate cysts, insect remains, and green algae remains from the same samples provides a direct land-sea comparison. The application of the modern analogues technique to pollen assemblages has previously yielded precise results for late Pleistocene and Holocene datasets, including specific information on

  4. El Nino influence on Holocene reef accretion in Hawai'i

    USGS Publications Warehouse

    Rooney, J.; Fletcher, C.; Grossman, E.; Engels, M.; Field, M.

    2004-01-01

    New observations of reef accretion from several locations show that in Hawai'i accretion during early to middle Holocene time occurred in areas where today it is precluded by the wave regime, suggesting an increase in wave energy. Accretion of coral and coralline algae reefs in the Hawaiian Islands today is largely controlled by wave energy. Many coastal areas in the main Hawaiian Islands are periodically exposed to large waves, in particular from North Pacific swell and hurricanes. These are of sufficient intensity to prevent modern net accretion as evidenced by the antecedent nature of the seafloor. Only in areas sheltered from intense wave energy is active accretion observed. Analysis of reef cores reveals patterns of rapid early Holocene accretion in several locations that terminated by middle Holocene time, ca. 5000 yr ago. Previous analyses have suggested that changes in Holocene accretion were a result of reef growth "catching up" to sea level. New data and interpretations indicate that the end of reef accretion in the middle Holocene may be influenced by factors in addition to sea level. Reef accretion histories from the islands of Kaua'i, O'ahu, and Moloka'i may be interpreted to suggest that a change in wave energy contributed to the reduction or termination of Holocene accretion by 5000 yr ago in some areas. In these cases, the decrease in reef accretion occurred before the best estimates of the decrease in relative sea-level rise during the mid-Holocene high stand of sea level in the main Hawaiian Islands. However, reef accretion should decrease following the termination of relative sea-level rise (ca. 3000 yr ago) if reef growth were "catching up" to sea level. Evidence indicates that rapid accretion occurred at these sites in early Holocene time and that no permanent accretion is occurring at these sites today. This pattern persists despite the availability of hard substrate suitable for colonization at a wide range of depths between -30 m and the

  5. Holocene Evolution of the Indus River Basin: the effect of climate and drainage reorganization on the Harappan

    NASA Astrophysics Data System (ADS)

    Alizai, A. H.; Clift, P. D.; Vanlaningham, S.; Giosan, L.; Carter, A.; Hillier, S.; Macklin, M. G.; Duller, G. A.; Durcan, J.

    2009-12-01

    The Indus River basin has evolved significantly during the Holocene and may have affected the Harappan Civilization which is believed to have collapsed around 2000 BC. We aim to understand the links between drainage evolution, the intensity of the South Asian Monsoon and the development of this early human society. Sediment was sampled from modern rivers, pits and shallow boreholes in the alluvial plains of the Indus and the inactive Ghaggar-Hakra tributary. A suite of techniques are used to resolve sediment source changes during, the Holocene, including bulk and clay mineralogy (XRD), garnet geochemistry, U-Pb dating of zircon grains, Ar-Ar dating of mica, and bulk Nd isotopic analyses. We report preliminary 14C and optically-stimulated luminescence (OSL) ages, U-Pb dating of zircon and mineralogical data from a delta core site (Keti Bandar), as well as two core sites and two shallow pits from the eastern upper Indus flood plain. Sediments from the delta show that the mineralogical changes are coherent with the regional climate changes in the Early Holocene. XRD mineralogy shows that illite concentrations peak around 14% in Early Holocene and decrease to 4% around 8 ka, while plagioclase feldspar ranges from 9% in the Early Holocene to 17% at the peak of the monsoon. The mineralogy in general shows a coherent trend when plotted against oxygen isotope measurements from speleothems. 14C and OSL age results from the eastern Indus flood plain cluster around 5-6 ka suggesting an active river at and before this time, and coincide with when the Harappan flourished. This eastern palaeo-tributary (Ghaggar-Hakra) of Indus drains the Lesser and the Higher Himalayas and is different from the trunk Indus stream which has sediment derived mainly from the Karakoram, Transhimalayas, Hindu Kush and Kohistan ranges. U-Pb zircon ages from Mid-Holocene sands along the path of the Ghaggar-Hakra River are very similar to the Indus and Thar Desert sands. We suggest that the Ghaggar

  6. Holocene paleoclimate inferred from salinity histories of adjacent lakes in southwestern Sicily (Italy)

    USGS Publications Warehouse

    Curry, B Brandon; Henne, Paul; Mezquita-Joanes, Francesc; Marrone, Federico; Pieri, Valentina; La Mantia, Tommaso; Calo, Camilla; Tinner, Willy

    2016-01-01

    Marked uncertainties persist regarding the climatic evolution of the Mediterranean region during the Holocene. For instance, whether moisture availability gradually decreased, remained relatively constant, or increased during the last 7000 years remains a matter of debate. To assess Holocene limnology, hydrology and moisture dynamics, the coastal lakes Lago Preola and Gorgo Basso, located in southwestern Sicily, were investigated through several stratigraphic analyses of ostracodes, including multivariate analyses of assemblages, transfer functions of salinity, and biochemical analyses of valves (Sr/Ca, δ18O and δ13C). During the early Holocene, the Gorgo Basso and Lago Preola ostracode records are similar. After an initial period of moderate salinity (1690–6100 mg/l from ca. 10,000–8190 cal yr BP), syndepositional or diagenetic dissolution of ostracode valves suggests that salinity declined to <250 mg/L from ca. 8190 to 7000 cal yr BP at both sites. After ca. 6250 cal yr BP, the ostracode records are strikingly different. Lago Preola became much more saline, with paleosalinity values that ranged from 2270 to about 24,420 mg/L. We suggest that Lago Preola's change from a freshwater to mesosaline lake at about 6250 cal yr BP was related to sea level rise and resulting intrusion of seawater-influenced groundwater. In contrast, Gorgo Basso remained a freshwater lake. The salinity of Gorgo Basso declined somewhat after 6250 cal yr BP, in comparison to the early Holocene, ranging from about 550 to 1680 mg/L. Cypria ophtalmica, a species capable of rapid swimming and flourishing in waters with low dissolved oxygen levels, became dominant at approximately the time when Greek civilization took root in Sicily (2600 cal yr BP), and it completely dominates the record during Roman occupation (roughly 2100 to 1700 cal yr BP). These freshwater conditions at Gorgo Basso suggest high effective moisture when evergreen olive-oak forests collapsed in response

  7. Variations in the strength of the North Atlantic bottom water during Holocene

    NASA Astrophysics Data System (ADS)

    Kissel, Catherine; Van Toer, Aurélie; Laj, Carlo; Cortijo, Elsa; Michel, Elisabeth

    2013-05-01

    We report here on a multi-proxy study of the changes in the dynamics and the properties of bottom water mass in the subpolar North Altantic during Holocene. Magnetic properties coupled with sortable silt and benthic carbon isotopes are investigated for Holocene marine sedimentary sequences located in the Charlie-Gibbs fracture zone (53°N) and in central (57°N) and southern Gardar drift (59°N). All the cores are located at water depths bathed by the Iceland-Scotland Overflow Water (ISOW), mixed at the southernmost locality with southern sourced water masses. The long-term variations in measured proxies are fitted with similar polynomial curves. An early Holocene event characterized by a shutdown/shoaling of the bottom circulation at the deepest sites is most likely related to the main deglacial freshwater inputs. It is followed by a progressive strengthening/deepening of the overflow water which culminates around 6 kyr, in coincidence with the Holocene thermal maximum. After 6 kyr corresponding to a drastic hydrological reorganization in the North Atlantic, a general decline in the bottom flow strength is observed until about 2 kyr B.P. when it reached its present day state. After detrending, several short periods of reduced bottom flow strength and sedimentary transport from the northern detrital sources are observed, with a periodicity of around 600 yr with no clear relationship at this time scale between surface and deep ocean.

  8. Exploring holocene changes in palynological richness in northern Europe--did postglacial immigration matter?

    PubMed

    Giesecke, Thomas; Wolters, Steffen; Jahns, Susanne; Brande, Arthur

    2012-01-01

    In mid to high latitudes glacial and interglacial cycles have repeatedly changed the area available for plant growth. The speed at which plants are able to colonize areas at the onset of an interglacial is hypothesized to limit their distribution ranges even today (migrational lag). If the spread of plants would have been generally slow then plant diversity in previously glaciated areas would be expected to increase over time. We explore this hypothesis using results from six palynological investigations from two previously glaciated regions: central Sweden and north-eastern Germany. Rarefaction, slope of rank order abundance, and taxa accumulation plots were used to evaluate richness and evenness in pollen data in an attempt to separate richness from evenness. These analyses show little change in palynological richness for the northern sites throughout the Holocene. In contrast, the southern sites show an increase in richness and evenness during the early Holocene; this may be explained by the different initial conditions at the onset of the Holocene. A strong rise in palynological richness around 6000 and 1000 years ago at the southern sites can be attributed to the regional initiation of agriculture and major opening of the forest, respectively. For the northern sites there is no evidence for increased taxonomic diversity through time that could be due to delayed immigration of species. PMID:23240048

  9. Exploring Holocene Changes in Palynological Richness in Northern Europe – Did Postglacial Immigration Matter?

    PubMed Central

    Giesecke, Thomas; Wolters, Steffen; Jahns, Susanne; Brande, Arthur

    2012-01-01

    In mid to high latitudes glacial and interglacial cycles have repeatedly changed the area available for plant growth. The speed at which plants are able to colonize areas at the onset of an interglacial is hypothesized to limit their distribution ranges even today (migrational lag). If the spread of plants would have been generally slow then plant diversity in previously glaciated areas would be expected to increase over time. We explore this hypothesis using results from six palynological investigations from two previously glaciated regions: central Sweden and north-eastern Germany. Rarefaction, slope of rank order abundance, and taxa accumulation plots were used to evaluate richness and evenness in pollen data in an attempt to separate richness from evenness. These analyses show little change in palynological richness for the northern sites throughout the Holocene. In contrast, the southern sites show an increase in richness and evenness during the early Holocene; this may be explained by the different initial conditions at the onset of the Holocene. A strong rise in palynological richness around 6000 and 1000 years ago at the southern sites can be attributed to the regional initiation of agriculture and major opening of the forest, respectively. For the northern sites there is no evidence for increased taxonomic diversity through time that could be due to delayed immigration of species. PMID:23240048

  10. Chronostratigraphy of Holocene alluvium in eastern Grand Canyon: Correlatable terraces or local paleoflood sequences?

    NASA Astrophysics Data System (ADS)

    Tainer, E. M.; Pederson, J. L.; Rittenour, T. M.; O'Brien, G. R.

    2008-12-01

    Understanding the nature of Colorado River deposits in Grand Canyon will help reveal how the river responds to changes in its Colorado Plateau tributaries and Rocky Mountain headwaters. This study focuses on Holocene alluvial deposits associated with archaeological sites excavated near Ninemile Draw in Glen Canyon and at Tanner Bar in eastern Grand Canyon. We are testing two previously-developed models of deposition. Hereford (1996) suggested that Holocene alluvial deposits in Grand Canyon are a series of inset aggradational packages that correlate to valley fills and arroyo cutting cycles identified in tributaries on the Colorado Plateau, and they should be laterally correlatable throughout the river corridor. An alternate hypothesis is that the alluvial packages record paleoflood sequences along the Colorado River with no change in river grade during the Holocene. In this model, deposition is preserved more randomly and varies by location because of differences in local hydrologic geometry. Three detailed stratigraphic columns of terrace deposits and several stratigraphic panels of archaeological trenches with facies interpretations have been used to reconstruct a high-resolution alluvial history of these locations. Optically stimulated luminescence (OSL) and radiocarbon dating methods were used at both locations with consistent results. At both sites, stratigraphy includes multiple depositional facies of both mainstem and locally-source material. Deposits consist of several sequences bound by unconformities. Ninemile Draw stratigraphy indicates three such sequences. At Tanner Bar, ages spanning the entire Holocene also reveal at least two distinct periods of deposition. Overall, the alluvium is composed of at least six discrete alluvial packages located at overlapping heights above river level throughout the canyon. Therefore, ages of the deposits cannot be distinguished by terrace level. The two oldest packages dated are early to middle Holocene, older than any

  11. Tracking Nile Delta vulnerability to Holocene change.

    PubMed

    Marriner, Nick; Flaux, Clément; Morhange, Christophe; Stanley, Jean-Daniel

    2013-01-01

    Understanding deltaic resilience in the face of Holocene climate change and human impacts is an important challenge for the earth sciences in characterizing the full range of present and future wetland responses to global warming. Here, we report an 8000-year mass balance record from the Nile Delta to reconstruct when and how this sedimentary basin has responded to past hydrological shifts. In a global Holocene context, the long-term decrease in Nile Delta accretion rates is consistent with insolation-driven changes in the 'monsoon pacemaker', attested throughout the mid-latitude tropics. Following the early to mid-Holocene growth of the Nile's deltaic plain, sediment losses and pronounced erosion are first recorded after ~4000 years ago, the corollaries of falling sediment supply and an intensification of anthropogenic impacts from the Pharaonic period onwards. Against the backcloth of the Saharan 'depeopling', reduced river flow underpinned by a weakening of monsoonal precipitation appears to have been particularly conducive to the expansion of human activities on the delta by exposing productive floodplain lands for occupation and irrigation agriculture. The reconstruction suggests that the Nile Delta has a particularly long history of vulnerability to extreme events (e.g. floods and storms) and sea-level rise, although the present sediment-starved system does not have a direct Holocene analogue. This study highlights the importance of the world's deltas as sensitive archives to investigate Holocene geosystem responses to climate change, risks and hazards, and societal interaction. PMID:23922692

  12. 7300 years of vegetation history and climate for NW Malta: a Holocene perspective

    NASA Astrophysics Data System (ADS)

    Gambin, B.; Andrieu-Ponel, V.; Médail, F.; Marriner, N.; Peyron, O.; Montade, V.; Gambin, T.; Morhange, C.; Belkacem, D.; Djamali, M.

    2016-02-01

    This paper investigates the Holocene vegetation dynamics for Burmarrad in Northwest Malta and provides a pollen-based quantitative palaeoclimatic reconstruction for this centrally located Mediterranean archipelago. The pollen record from this site provides new insight into the vegetation changes from 7280 to 1730 cal BP which correspond well with other regional records. The climate reconstruction for the area also provides strong correlation with southern (below 40° N) Mediterranean sites. Our interpretation suggests an initially open landscape during the early Neolithic, surrounding a large palaeobay, developing into a dense Pistacia scrubland ca. 6700 cal BP. From about 4450 cal BP the landscape once again becomes open, coinciding with the start of the Bronze Age on the archipelago. This period is concurrent with increased climatic instability (between 4500 and 3700 cal BP) which is followed by a gradual decrease in summer moisture availability in the late Holocene. During the early Roman occupation period (1972-1730 cal BP) the landscape remains generally open with a moderate increase in Olea. This increase corresponds to archaeological evidence for olive oil production in the area, along with increases in cultivated crop taxa and associated ruderal species, as well as a rise in fire events. The Maltese archipelago provides important insight into vegetation, human impacts, and climatic changes in an island context during the Holocene.

  13. 7300 years of vegetation history and climate for NW Malta: a Holocene perspective

    NASA Astrophysics Data System (ADS)

    Gambin, B.; Andrieu-Ponel, V.; Médail, F.; Marriner, N.; Peyron, O.; Montade, V.; Gambin, T.; Morhange, C.; Belkacem, D.; Djamali, M.

    2015-09-01

    This paper investigates the Holocene vegetation dynamics for Burmarrad in north-west Malta and provides a pollen-based quantitative palaeoclimatic reconstruction for this centrally located Mediterranean archipelago. The pollen record from this site provides new insight into the vegetation changes from 7280 to 1730 cal BP which correspond well with other regional records. The climate reconstruction for the area also provides strong correlation with southern (below 40° N) Mediterranean sites. Our interpretation suggests an initially open landscape during the early Neolithic, surrounding a large palaeobay, developing into a dense Pistacia scrubland ca. 6700 cal BP. From about 4450 cal BP the landscape once again becomes open, coinciding with the start of the Bronze Age on the archipelago. This period is concurrent with increased climatic instability (between 4500 and 3700 cal BP) which is followed by a gradual decrease in summer moisture availability in the late Holocene. During the early Roman occupation period (1972 to 1730 cal BP) the landscape remains generally open with a moderate increase in Olea. This increase, corresponds to archaeological evidence for olive oil production in the area, along with increases in cultivated crop taxa and associated ruderal species, as well as a rise in fire events. The Maltese archipelago provides important insight into vegetation, human impacts and climatic changes in an island context during the Holocene.

  14. Charcoal analysis and Holocene vegetation history in southern Syria

    NASA Astrophysics Data System (ADS)

    Willcox, George

    1999-04-01

    Charcoal analysis of three archaeological sites in southern Syria in the vicinity of the Jebel al Arab (formerly Jebel Druze) indicates that during the Early Bronze Age an association consisting predominately of Pistacia, deciduous oak and almond was exploited. During the Middle Bronze Age these taxa diminish and are partially replaced by more steppic species or introduced wood such as olive. During the Roman period evergreen oak appeared in the region and gradually replaced the deciduous oak which is now restricted to a small area. The gradual replacement of deciduous oaks by evergreen oaks has been observed in other areas of the Mediterranean basin during the Holocene. Conifer charcoal such as pine and cedar is present on the sites, but it is not clear whether these were local or imported from farther away, for example, the Lebanese highlands. During the Middle Bronze Age olive wood was also used as combustible but here also its exact origin is not known.

  15. Holocene glacier activity in the British Columbia Coast Mountains, Canada

    NASA Astrophysics Data System (ADS)

    Mood, Bryan J.; Smith, Dan J.

    2015-11-01

    The Coast Mountains flank the Pacific Ocean in western British Columbia, Canada. Subdivided into the southern Pacific Ranges, central Kitimat Ranges and northern Boundary Ranges, the majority of large glaciers and icefields are located in the Boundary and Pacific ranges. Prior descriptions of the Holocene glacial history of this region indicate the Holocene was characterized by repeated episodes of ice expansion and retreat. Recent site-specific investigations augment our understanding of the regional character and duration of these events. In this paper, previously reported and new radiocarbon evidence is integrated to provide an updated regional assessment. The earliest evidence of glacier expansion in the Coast Mountains comes from the Boundary Ranges at 8.9 and 7.8 ka and in the Pacific Ranges at 8.5-8.2 ka, with the latter advance corresponding to an interval of rapid, global climate deterioration. Although generally warm and dry climates from 7.3 to 5.3 ka likely limited the size of glaciers in the region, there is radiocarbon evidence for advances over the interval from 7.3 to 6.0 and at 5.4-5.3 ka in the Pacific Ranges. Following these advances, glaciers in the Pacific Ranges expanded down valley at 4.8-4.6, 4.4-4.0, 3.5-2.6, 1.4-1.2, and 0.8-0.4 ka, while glaciers in Boundary Ranges were advancing at 4.1-4.0, 3.7-3.4, 3.1-2.8, 2.3, 1.7-1.1, and 0.8-0.4 ka. After 0.4 ka, it appears that most glaciers in the Coast Mountains continued to expand to attain their maximum Holocene extents by the early 18th to late 19th centuries. This enhanced record of Holocene glacier activity highlights the temporal synchrony in the Coast Mountains. Individual expansion events in the mid-to late Holocene broadly correspond to intervals of regional glacier activity reported in the Canadian Rocky Mountains, in Alaska, and on high-elevation volcanic peaks in Washington State.

  16. Did Lake Elsinore's Stormy Affair End, or Just Change, in the Mid-Holocene?

    NASA Astrophysics Data System (ADS)

    Kirby, M. E.; Lund, S. P.; Patterson, W. P.; Anderson, M. A.; Monarrez, P.; Ivanovici, L.; Nielsen, S.

    2008-12-01

    High-resolution, continuous terrestrial records of Holocene climate from Southern California are scarce. Recent research on Lake Elsinore, however, has shown that the lake's sediments hold excellent potential for paleoenvironmental analysis and reconstruction. Kirby et al. (2007) use environmental magnetic susceptibility and loss-on-ignition to suggest a wet early Holocene followed by a long-term drying trend. New grain size and δ18O(calcite) data reveal a more complex Holocene climate history for Southern California than previously recognized at the site. A modern comparison between 20th century San Jacinto River discharge and various sand size classifications suggests that percent sand is a reasonable, qualitative proxy for past climate wetness, especially intervals of above-average discharge (i.e., higher lake level). This modern analysis also indicates that exceptional discharge years produce discrete sand peaks; although, these sand peaks are not visible generally to the naked eye - at least for the 20th century. From this, percent sand is also used as a qualitative measure of past "storminess". Together, the sand data indicate a stormy early-to- mid Holocene with a pronounced decrease in the frequency of large storms by ~3,300 cy BP as well as millennial-scale hydrologic cycles throughout the Holocene. A count of visual "storm" layers supports the storm interpretation, which reveals 18 events before, and only 7 after, 4,000 cy BP. The occurrence of mudcracks in a slightly shallower core (1m modern depth difference) indicates only 2 potential lowstands before, and 5 after, 4,000 cy BP as well as no clear evidence for whole-lake, Holocene desiccation until ~500 cy BP. Although still in progress, the δ18O(calcite) also indicate a shift in the region's climatic state ca. 4,000-5,000 cy BP as well as millennial scale hydrologic cycles(?). This transition out of the mid-Holocene ca. 4,000 cy BP is observed elsewhere in Southern California (e.g., Dry Lake and Big

  17. Advanced Simulation Capability for Environmental Management (ASCEM): Early Site Demonstration

    SciTech Connect

    Meza, Juan; Hubbard, Susan; Freshley, Mark D.; Gorton, Ian; Moulton, David; Denham, Miles E.

    2011-03-07

    The U.S. Department of Energy Office of Environmental Management, Technology Innovation and Development (EM-32), is supporting development of the Advanced Simulation Capability for Environmental Management (ASCEM). ASCEM is a state-of-the-art scientific tool and approach for understanding and predicting contaminant fate and transport in natural and engineered systems. The modular and open source high performance computing tool will facilitate integrated approaches to modeling and site characterization that enable robust and standardized assessments of performance and risk for EM cleanup and closure activities. As part of the initial development process, a series of demonstrations were defined to test ASCEM components and provide feedback to developers, engage end users in applications, and lead to an outcome that would benefit the sites. The demonstration was implemented for a sub-region of the Savannah River Site General Separations Area that includes the F-Area Seepage Basins. The physical domain included the unsaturated and saturated zones in the vicinity of the seepage basins and Fourmile Branch, using an unstructured mesh fit to the hydrostratigraphy and topography of the site. The calculations modeled variably saturated flow and the resulting flow field was used in simulations of the advection of non-reactive species and the reactive-transport of uranium. As part of the demonstrations, a new set of data management, visualization, and uncertainty quantification tools were developed to analyze simulation results and existing site data. These new tools can be used to provide summary statistics, including information on which simulation parameters were most important in the prediction of uncertainty and to visualize the relationships between model input and output.

  18. A high resolution history of the El Niño - Southern Oscillation and of the solar activity during the Late Glacial - Early Holocene in the subtropical Andean region.

    NASA Astrophysics Data System (ADS)

    Giralt, S.; Schimmel, M.; Hernández, A.; Bao, R.; Valero-Garcés, B. L.; Sáez, A.; Pueyo, J. J.

    2009-04-01

    High-resolution laminated lacustrine sediments are excellent archives of the past hydrological changes and they provide valuable insights about the climatic processes that trigger these changes. The paleoclimatic records located in the Southern Hemisphere are fundamental for understanding the evolution of the El Niño - Southern Oscillation (ENSO) since this climatic phenomena is the main cause of droughts and floods in many areas of South America and other regions of the world, like Spain and Egypt. Available regional paleoclimate reconstructions show that modern climatic patterns in South America were established during the Late Holocene. The laminated sediments of Lago Chungará (18° 15' S - 69° 10' W, 4520 m a.s.l., Chilean altiplano) have allowed us to characterize the evolution of this climatic phenomena for the transition Late Glacial - Early Holocene (12,300 - 9,500 calendar years BP) as well as its relationship with other climate forcings, namely the solar activity. The studied sediments correspond to the lowermost 2.4 m of 8 m long Kullemberg cores recovered from this lake. These sediments are mainly made up of greenish and whitish laminae and thin layers constituted by diatomaceous oozes with carbonates and organic matter, arranged in rhythms and cycles. X-ray fluorescence (XRF) (Al, Si, S, K, Ca, Ti, Mn, Fe, Rb, Sr, Zn, Sb and Ba) analyses, total organic carbon (TOC), total carbon (TC), x-ray diffraction (XRD), biogenic silica, stable isotopes (delta18O and delta13C) on carbonates and on diatoms (delta18O) and magnetic susceptibility were determined in order to characterize the sediments of Lago Chungará. Previous statistical studies (cluster and Principal Component Analyses (PCA)) were used to disentangle the paleoclimatic signal from the other ones (volcanic and tectonic). The chronological model framework was built using 6 radiocarbon dates, allowing us to establish that laminated couplets were deposited on a pluriannual basis. These couplets are

  19. The expectant management of early pregnancies of uncertain site.

    PubMed

    Hahlin, M; Thorburn, J; Bryman, I

    1995-05-01

    The role of expectant management was evaluated in 80 women in whom clinical examination, including vaginal ultrasound, had failed to identify the location of an early pregnancy. In 45 cases, spontaneous resolution of the pregnancy products occurred. A normal intra-uterine pregnancy was diagnosed in 12 patients. A total of 23 patients underwent active therapeutic measures due to an ectopic pregnancy (n = 16) or a spontaneous abortion (n = 7). The effectiveness of different diagnostic measures to identify patients suitable for expectant management was analysed. In 33/34 patients (97%) with a relative daily human chorionic gonadotrophin (HCG) change of < -5%, and a serum progesterone concentration of < 20 nmol/l, spontaneous resolution of the pregnancy products occurred. Among 46 cases, with a relative daily HCG change of > -5% and/or serum progesterone > 20 nmol/l, active therapeutic measures were carried out in 22 cases (48%), a normal intra-uterine pregnancy was diagnosed in 12 cases (26%) and spontaneous resolution of the pregnancy products occurred in 12 cases (26%). In conclusion, the combination of a single progesterone assay and serial HCG determinations retrospectively identified early pregnancies of uncertain location in whom expectant management was a safe management option. PMID:7657770

  20. Late Holocene earthquake history of the Brigham City segment of the Wasatch fault zone at the Hansen Canyon, Kotter Canyon, and Pearsons Canyon trench sites, Box Elder County, Utah

    USGS Publications Warehouse

    DuRoss, Christopher B.; Personius, Stephen F.; Crone, Anthony J.; McDonald, Greg N.; Briggs, Richard W.

    2012-01-01

    Of the five central segments of the Wasatch fault zone (WFZ) having evidence of recurrent Holocene surface-faulting earthquakes, the Brigham City segment (BCS) has the longest elapsed time since its most recent surface-faulting event (~2.1 kyr) compared to its mean recurrence time between events (~1.3 kyr). Thus, the BCS has the highest time-dependent earthquake probability of the central WFZ. We excavated trenches at three sites––the Kotter Canyon and Hansen Canyon sites on the north-central BCS and Pearsons Canyon site on the southern BCS––to determine whether a surface-faulting earthquake younger than 2.1 ka occurred on the BCS. Paleoseismic data for Hansen Canyon and Kotter Canyon confirm that the youngest earthquake on the north-central BCS occurred before 2 ka, consistent with previous north-central BCS investigations at Bowden Canyon and Box Elder Canyon. At Hansen Canyon, the most recent earthquake is constrained to 2.1–4.2 ka and had 0.6–2.5 m of vertical displacement. At Kotter Canyon, we found evidence for two events at 2.5 ± 0.3 ka and 3.5 ± 0.3 ka, with an average displacement per event of 1.9–2.3 m. Paleoseismic data from Pearsons Canyon, on the previously unstudied southern BCS, indicate that a post-2 ka earthquake ruptured this part of the segment. The Pearsons Canyon earthquake occurred at 1.2 ± 0.04 ka and had 0.1–0.8 m of vertical displacement, consistent with our observation of continuous, youthful scarps on the southern 9 km of the BCS having 1–2 m of late Holocene(?) surface offset. The 1.2-ka earthquake on the southern BCS likely represents rupture across the Weber–Brigham City segment boundary from the penultimate Weber-segment earthquake at about 1.1 ka. The Pearsons Canyon data result in a revised length of the BCS that has not ruptured since 2 ka (with time-dependent probability implications), and provide compelling evidence of at least one segment-boundary failure and multi-segment rupture on the central WFZ. Our

  1. The Role of Social Networking Sites in Early Adolescents' Social Lives

    ERIC Educational Resources Information Center

    Antheunis, Marjolijn L.; Schouten, Alexander P.; Krahmer, Emiel

    2016-01-01

    The aim of this study was to examine the role of social networking sites (SNSs) in early adolescents' social lives. First, we investigated the relation between SNS use and several aspects of early adolescents' social lives (i.e., friendship quality, bridging social capital, and bonding social capital). Second, we examined whether there are…

  2. Constraining the time of extinction of the South American fox Dusicyon avus (Carnivora, Canidae) during the late Holocene.

    NASA Astrophysics Data System (ADS)

    Prevosti, Francisco; Santiago, Fernando; Prates, Luciano; Salemme, Mónica; Martin, Fabiana

    2010-05-01

    The mass extinction at the end of the Pleistocene affected South America during the Late Pleistocene and the Early Holocene, when megamammals and large mammals disappeared. Several carnivores became extinct, like the sabretooth Smilodon, the short face bear (Arctotherium) and some large canids (i.e. Protocyon, Canis dirus). After this mass event virtually no carnivores became extinct in South America. The only exception is the fox Dusicyon avus, a middle sized canid (estimated body mass between 10-15 kg) with a more carnivore diet than the living South American foxes (i.e. Lycalopex culpaeus). The last record of the species comes from middle-late Holocene archaeological sites in the Pampean Region (Argentina) and Patagonia (Argentina and Chile). During the Late Pleistocene D. avus had a wide distribution, that covered part of Uruguay, Argentina (Buenos Aires province) and the southernmost Chile. Albeit some remains from late Holocene sites have been published, these remains lack of isotopic dates that could (allow?) constraint (to determine) the date of extinction of this fox. In this contribution we present several new records from the Pampean Region and Patagonia, and several taxon dates. The new records indicate that D. avus disappeared in the late Holocene at least ≈ 3000 years BP in the island of Tierra del Fuego (Patagonia) and ≈ 1600 BP in the continent. Since at this time humans were occupying most of the Pampas and Patagonia a revision of the causes behind the extinction of this fox is required.

  3. Holocene dust records from the West African Sahel and their implications for changes in climate and land surface conditions

    NASA Astrophysics Data System (ADS)

    Cockerton, Helen E.; Holmes, Jonathan A.; Street-Perrott, F. Alayne; Ficken, Katherine J.

    2014-07-01

    We reconstructed aeolian dust accumulation during the Holocene from two radiocarbon-dated lake-sediment sequences from the Manga Grasslands in northeastern Nigeria in order to investigate long-term changes in the Harmattan dust system over West Africa and evaluate their possible causes. Flux values were low in the early Holocene, decreasing further to a minimum at around 6.2 kyr B.P. after which time they increased, steadily until around 2 kyr B.P. and then more sharply after this time. The long-term variations in dust flux agree broadly with changes in the exposed area of the Lake Chad Basin to the northeast of the study sites, which vary inversely with the volume of Paleolake Megachad. More proximal sources of dust, including the fine fraction of local dune sand and floodplains of nearby rivers, have also made a contribution to the total dust load during times of enhanced dune and fluvial activity. Sharp rises in dust flux over the past century may be related to human activity. Broad patterns of change in dust flux during the Holocene agree with other reconstructions over the same period. However, we see no evidence for a stepped rise during the middle Holocene, as seen at some sites from the northeastern tropical Atlantic, suggesting that controls on the Harmattan dust system have differed from those affecting dust deposition elsewhere across northern Africa.

  4. 10 CFR 2.604 - Notice of hearing on application for early review of site suitability issues in construction...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Notice of hearing on application for early review of site... Applicable to Early Partial Decisions on Site Suitability Issues in Connection With an Application for a... Limited Work Authorizations Early Partial Decisions on Site Suitability-Construction Permit § 2.604...

  5. 10 CFR 2.623 - Notice of hearing on application for early review of site suitability issues in combined license...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Limited Work Authorizations Early Partial Decisions on Site Suitability-Combined License Under 10 Cfr Part... 10 Energy 1 2012-01-01 2012-01-01 false Notice of hearing on application for early review of site... Applicable to Early Partial Decisions on Site Suitability Issues in Connection With an Application for...

  6. 10 CFR 2.604 - Notice of hearing on application for early review of site suitability issues in construction...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Notice of hearing on application for early review of site... Applicable to Early Partial Decisions on Site Suitability Issues in Connection With an Application for a... Limited Work Authorizations Early Partial Decisions on Site Suitability-Construction Permit § 2.604...

  7. 10 CFR 2.623 - Notice of hearing on application for early review of site suitability issues in combined license...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Limited Work Authorizations Early Partial Decisions on Site Suitability-Combined License Under 10 Cfr Part... 10 Energy 1 2010-01-01 2010-01-01 false Notice of hearing on application for early review of site... Applicable to Early Partial Decisions on Site Suitability Issues in Connection With an Application for...

  8. 10 CFR 2.604 - Notice of hearing on application for early review of site suitability issues in construction...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Notice of hearing on application for early review of site... Applicable to Early Partial Decisions on Site Suitability Issues in Connection With an Application for a... Limited Work Authorizations Early Partial Decisions on Site Suitability-Construction Permit § 2.604...

  9. 10 CFR 2.623 - Notice of hearing on application for early review of site suitability issues in combined license...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Limited Work Authorizations Early Partial Decisions on Site Suitability-Combined License Under 10 Cfr Part... 10 Energy 1 2011-01-01 2011-01-01 false Notice of hearing on application for early review of site... Applicable to Early Partial Decisions on Site Suitability Issues in Connection With an Application for...

  10. Holocene History of the Bering Sea Bowhead Whale ( Balaena mysticetus) in Its Beaufort Sea Summer Grounds off Southwestern Victoria Island, Western Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Dyke, Arthur S.; Savelle, James M.

    2001-05-01

    The fossil remains of 43 bowhead whales were mapped on the raised beaches of western Wollaston Peninsula, Victoria Island, Canadian Arctic, near the historic summer range limit of the Bering Sea stock in the Beaufort Sea. The elevations and radiocarbon ages of the remains demonstrate that the bowhead ranged commonly into the region following the submergence of Bering Strait at ca. 10,000 14C yr B.P. until ca. 8500 14C yr B.P. During the same interval, bowheads ranged widely from the Beaufort Sea to Baffin Bay. Subsequently, no whales reached Wollaston Peninsula until ca. 1500 14C yr B.P. Late Holocene populations evidently were small, or occupations were brief, in comparison to those of the early Holocene. Although the late Holocene recurrence may relate to the expansion of pioneering Thule whalers eastward from Alaska, there are few Thule sites and limited evidence of Thule whaling in the area surveyed to support this suggestion.

  11. Asynchronous evolution of the Indian and East Asian Summer Monsoon indicated by Holocene moisture patterns in monsoonal central Asia

    NASA Astrophysics Data System (ADS)

    Wang, Yongbo; Liu, Xingqi; Herzschuh, Ulrike

    2010-12-01

    The numerical meta-analysis of 92 proxy records (72 sites) of moisture and/or temperature change confirms earlier findings that the dominant trends of climatic evolution in monsoonal central Asia since the Last Glacial roughly parallel changes in Northern Hemisphere summer insolation, i.e. the period following the Last Glacial Maximum was characterized by dry and cold conditions until 15 cal. kyr BP, followed by a warm, wet period coincident with the Bølling/Allerød warm period and terminated by a cold, dry reversal during the Younger Dryas period. After an abrupt increase at the start of the Holocene, warm and wet conditions prevailed until ca. 4 cal. kyr BP when moisture levels and temperatures started to decrease. Ordination of moisture records reveals strong spatial heterogeneity in moisture evolution during the last 10 cal. kyr. The Indian Summer Monsoon (ISM) areas (northern India, Tibetan Plateau and southwest China) exhibit maximum wet conditions during the early Holocene, while many records from the area of the East Asian Summer Monsoon indicate relatively dry conditions, especially in north-central China where the maximum moisture levels occurred during the mid-Holocene. We assign such phenomena to strengthened Hadley Circulation centered over the Tibetan Plateau during the early Holocene which resulted in subsidence in the East Asian monsoonal regions leading to relatively dry conditions. Our observations of the asynchronous nature of the two Asian monsoon subsystems on millennial time scales have also been observed on annual time-scales as well as implied through the spatial analysis of vertical air motion patterns after strong ascending airflows over the Tibetan Plateau area that were calculated from NCEP/NCAR reanalysis data for the last 30 years. Analogous with the early Holocene, the enhancement of the ISM in a 'future warming world' will result in an increase in the asynchronous nature of the monsoon subsystems; this trend is already observed in

  12. Prp40 and early events in splice site definition.

    PubMed

    Becerra, Soraya; Andrés-León, Eduardo; Prieto-Sánchez, Silvia; Hernández-Munain, Cristina; Suñé, Carlos

    2016-01-01

    The alternative splicing (AS) of precursor messenger RNA (pre-mRNA) is a tightly regulated process through which introns are removed to leave the resulting exons in the mRNA appropriately aligned and ligated. The AS of pre-mRNA is a key mechanism for increasing the complexity of proteins encoded in the genome. In humans, more than 90% of genes undergo AS, underscoring the importance of this process in RNA biogenesis. As such, AS misregulation underlies multiple human diseases. The splicing reaction is catalyzed by the spliceosome, a highly dynamic complex that assembles at or near the intron/exon boundaries and undergoes sequential conformational and compositional changes during splicing. The initial recognition of splice sites defines the exons that are going to be removed, which is a critical step in the highly regulated splicing process. Although the available lines of evidence are increasing, the molecular mechanisms governing AS, including the initial interactions occurring at intron/exon boundaries, and the factors that modulate these critical connections by functioning as a scaffold for active-site RNAs or proteins, remain poorly understood. In this review, we summarize the major hallmarks of the initial steps in the splicing process and the role of auxiliary factors that contribute to the assembly of the spliceosomal complex. We also discuss the role of the essential yeast Prp40 protein and its mammalian homologs in the specificity of this pre-mRNA processing event. In addition, we provide the first exhaustive phylogenetic analysis of the molecular evolution of Prp40 family members. WIREs RNA 2016, 7:17-32. doi: 10.1002/wrna.1312 For further resources related to this article, please visit the WIREs website. PMID:26494226

  13. Holocene Climate in Northwest Greenland Inferred from Oxygen Isotopes of Preserved Aquatic Organic Material

    NASA Astrophysics Data System (ADS)

    Lasher, G. E.; Axford, Y.; McFarlin, J. M.; Kelly, M. A.; Osterberg, E. C.; Farnsworth, L. B.; Kotecki, P.

    2015-12-01

    Oxygen isotopes of paleo lake-water archived in subfossil aquatic organic material offer new insights into Arctic Holocene climate history. Here we present new constraints on the timing and magnitude of Holocene climate change in NW Greenland inferred from δ18O of chironomid head capsules, Cladocera ephippia, and aquatic macrophytes. δ18O of chironomids from surface sediments of multiple lakes in the region show consistent enrichment relative to lake-water (-18 to -22 ‰), on the order of 23 ‰. Lake-water δ18O collected during the summer of 2014 is comparable to modern and historical seasonal local meteoric water, and landscape position suggests dominantly precipitation inputs. Sediment cores recovered from two small, non-glacial lakes in 2014 near Thule Air Base capture continuous 7.7 kyr and 10.4 kyr records. δ18O of chironomids and macrophytes from Secret Lake decreases after 6 ka by 3 ‰ into the Neoglacial. Early Holocene values from Wax Lips Lake (informal name) are 3 to 4 ‰ higher than modern and decrease to the present, except for a large negative excursion ~5 ka. This is contemporaneous with a major change in stratigraphy and the hypothesized transient incursion of a regional, ice-dammed glacial lake system. At both lakes, declining δ18O from the early/middle to late Holocene is clearly recorded in multiple aquatic materials and is greater in magnitude than the mid to late Holocene changes in δ18O of the nearest ice core records (Agassiz and Camp Century, ~2 ‰). The temperature change of 4 to 6 °C inferred from this new δ18O approach is also larger than, but within the error of, chironomid assemblage based temperatures from Wax Lips Lake by McFarlin et al. (this meeting). This may indicate larger temperature changes at the ice sheet's margin than inferred from high-elevation ice core sites and/or some overprinting by enhanced evaporation of lake-water in the warmer climate of the early Holocene.

  14. Glacial retreat between the Late-Glacial and Early Holocene sequences in the Southern French Alps : definition of an accurate pattern by new Cosmic Ray Exposure ages.

    NASA Astrophysics Data System (ADS)

    Cossart, Etienne; Fort, Monique; Bourlès, Didier; Braucher, Régis; Carcaillet, Julien; Perrier, Romain; Siame, Lionel; Gribenski, Natacha

    2010-05-01

    The Southern French Alps, characterized by many climatic influences (oceanic, continental and mediterranean), remain a scientific problem for palaeo-environmental studies. Indeed, the lack of chronological benchmarks hitherto hampered the definition of sequences of glacier variations since the Last Glacial Maximum (LGM), even if a scenario was based upon an extensive fieldwork realized in the Ubaye valley. This scenario was then considered as a regional model by many geomorphologists, but this valley is not necessarily representative of the entire region. Firstly, this valley is the driest area within the Southern French Alps due the sheltering effect of relief against humid fluxes. Secondly, topography (altitudes, slopes and shapes) of the upper part of watersheds are not particularly prone to snow accumulation into the cirques. The established scenario is as follows. Glaciers shrank and decayed between the LGM and the Late-Glacial periods and glaciers were restricted in cirques areas during the Late-Glacial and Holocene glaciations. We try to discuss this model thanks to geomorphic investigations and new chronological benchmarks acquired in Briançonnais area, in the upper part of Durance watershed. The upper part of the Durance watershed was chosen because it corresponds to the accumulation zone of the main glacier of the Southern French Alps during the LGM. Thanks to extensive fieldwork and geomorphic mapping of remnants of past glaciations, and thanks to new chronological data (about 35 cosmic ray exposure -CRE- ages, acquired in 2004 and 2009) we propose here the first absolute scenario established in the very upper part of the catchment. To assess CRE ages, we sampled glacially-polished surfaces, along both longitudinal and transverse valley cross-sections, in order to assess both the retreat of the front and the thinning rate of the glacial tongue. We also paid attention to knobs located at the outlet of glacial cirques, and some morainic ridges. The

  15. Holocene sedimentation in Richardson Bay, California

    USGS Publications Warehouse

    Connor, Cathy L.

    1983-01-01

    Examination of foraminifers, diatoms, ostracodes, clay mineralogy, and sediment-size variation from 9 borehole sites along the salt-marsh margins of Richardson Bay reveals a record of gradual infilling of fine-grained estuarine sediments. Over the past 10,000 years this area was transformed from a V-shaped Pleistocene stream valley to a flat-floored arm of the San Francisco Bay estuary. A radiocarbon date obtained from a basal peat overlying nonmarine alluvial sand near the town of Mill Valley indicates that stable salt-marsh vegetation was present in the northwestern arm of Richardson Bay 4600?165 years ago and agrees within error limits with a Holocene sea-level curve developed by Atwater, Hedel, and Helley in 1977 for southern San Francisco Bay. The average sedimentation rate over the last 4600 years is estimated to be 0.2 cm/yr for the inner part of the bay. Comparison of early maps with updated versions as well as studies of marsh plant zonations in disturbed and nondisturbed areas shows that almost half of the marsh in Richardson Bay has been leveed or filled since 1899.

  16. Cortico-cortical evoked potentials for sites of early versus late seizure spread in stereoelectroencephalography.

    PubMed

    Lega, Bradley; Dionisio, Sasha; Flanigan, Patrick; Bingaman, William; Najm, Imad; Nair, Dileep; Gonzalez-Martinez, Jorge

    2015-09-01

    Cortico-cortical evoked potentials offer the possibility of understanding connectivity within seizure networks to improve diagnosis and more accurately identify candidates for seizure surgery. We sought to determine if cortico-cortical evoked potentials and post-stimulation oscillatory changes differ for sites of EARLY versus LATE ictal spread. 37 patients undergoing stereoelectroencephalography were tested using a cortico-cortical evoked potential paradigm. All electrodes were classified according to the speed of ictal spread. EARLY spread sites were matched to a LATE spread site equidistant from the onset zone. Root-mean-square was used to quantify evoked responses and post-stimulation gamma band power and coherence were extracted and compared. Sites of EARLY spread exhibited significantly greater evoked responses after stimulation across all patients (t(36)=2.973, p=0.004). Stimulation elicited enhanced gamma band activity at EARLY spread sites (t(36)=2.61, p=0.03, FDR corrected); this gamma band oscillation was highly coherent with the onset zone. Cortico-cortical evoked potentials and post-stimulation changes in gamma band activity differ between sites of EARLY versus LATE ictal spread. The oscillatory changes can help visualize connectivity within the seizure network. PMID:26220373

  17. Early endoscopic retrograde cholangiopancreatography after laparoscopic cholecystectomy can strain the occurrence of trocar site hernia.

    PubMed

    Sumer, Fatih; Kayaalp, Cuneyt; Yagci, Mehmet Ali; Otan, Emrah; Kocaaslan, Huseyin

    2014-11-16

    This study reports a 69-year-old, obese, female patient presenting with a biliary leakage after laparoscopic cholecystectomy for cholelithiasis. Closure of the umbilical trocar site had been neglected during the laparoscopic cholecystectomy. Early, on postoperative day five, endoscopic retrograde cholangiopancreatography (ERCP) requirement after laparoscopic cholecystectomy resolved the biliary leakage problem but resulted with a more complicated clinical picture with an intestinal obstruction and severe abdominal pain. Computed tomography revealed a strangulated hernia from the umbilical trocar site. Increased abdominal pressure during ERCP had strained the weak umbilical trocar site. Emergency surgical intervention through the umbilicus revealed an ischemic small bowel segment which was treated with resection and anastomosis. This report demonstrates that negligence of trocar site closure can result in very early herniation, particularly if an endoscopic intervention is required in the early postoperative period. PMID:25400872

  18. Early endoscopic retrograde cholangiopancreatography after laparoscopic cholecystectomy can strain the occurrence of trocar site hernia

    PubMed Central

    Sumer, Fatih; Kayaalp, Cuneyt; Yagci, Mehmet Ali; Otan, Emrah; Kocaaslan, Huseyin

    2014-01-01

    This study reports a 69-year-old, obese, female patient presenting with a biliary leakage after laparoscopic cholecystectomy for cholelithiasis. Closure of the umbilical trocar site had been neglected during the laparoscopic cholecystectomy. Early, on postoperative day five, endoscopic retrograde cholangiopancreatography (ERCP) requirement after laparoscopic cholecystectomy resolved the biliary leakage problem but resulted with a more complicated clinical picture with an intestinal obstruction and severe abdominal pain. Computed tomography revealed a strangulated hernia from the umbilical trocar site. Increased abdominal pressure during ERCP had strained the weak umbilical trocar site. Emergency surgical intervention through the umbilicus revealed an ischemic small bowel segment which was treated with resection and anastomosis. This report demonstrates that negligence of trocar site closure can result in very early herniation, particularly if an endoscopic intervention is required in the early postoperative period. PMID:25400872

  19. Holocene sea-level change and the emergence of Neolithic seafaring in the Fuzhou Basin (Fujian, China)

    NASA Astrophysics Data System (ADS)

    Rolett, Barry V.; Zheng, Zhuo; Yue, Yuanfu

    2011-04-01

    Neolithic seafaring across the Taiwan Strait began approximately 5000 years ago and involved open-sea voyages over distances of at least 130 km. Rapid sea-level rise preceded the emergence of open-sea voyaging, but the possible role of environmental change as a stimulus for the development of seafaring is poorly understood. We investigate this problem by presenting a record of Holocene sea-level change and coastal transformation based on sediment cores obtained from the Fuzhou Basin on the coast of Fujian, China. The cores are located in direct proximity to archaeological sites of the Tanshishan Neolithic culture (5000-4300 cal BP), which is significant for its similarity to the earliest Neolithic cultures of Taiwan. Multiple lines of evidence record the early Holocene inundation of the Fuzhou Basin around 9000 cal BP, the mid-Holocene sea-level highstand, and the final Holocene marine transgression. This final transition is precisely documented, with AMS dates showing the change occurred close to 1900 cal BP. Our paleogeographic reconstruction shows that a large estuary filled the Fuzhou Basin during the mid-Holocene. Tanshishan and Zhuangbianshan, two of the major Fuzhou Basin Neolithic sites, are located today on hills nearly 80 km from the modern coastline. However, when the sites were settled around 5500-5000 cal BP, the marine transgression had transformed these hills into islands in the upper estuary. We suggest that the Neolithic era estuary setting, together with the lack of land suitable for rice paddy agriculture, inhibited intensive food production but favored a maritime orientation and the development of seafaring.

  20. Latest Pleistocene and Holocene glacier fluctuations in southernmost Tierra del Fuego, Argentina

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Clague, John J.; Osborn, Gerald; Davis, P. Thompson; Ponce, Federico; Goehring, Brent; Maurer, Malyssa; Rabassa, Jorge; Coronato, Andrea; Marr, Rob

    2013-10-01

    Some researchers propose that summer insolation controls long-term changes in glacier extent during the Holocene. If this hypothesis is correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Although the chronology of Holocene glacier fluctuations in the Northern Hemisphere is well established, much uncertainty remains in the ages of Holocene glacier fluctuations in the Southern Hemisphere, especially South America. Here we report on latest Pleistocene and Holocene glacier fluctuations at the southern end of the Andes north and west of Ushuaia, Argentina. Surface exposure ages (10Be) from glaciated bedrock beyond cirque moraines indicate that alpine areas were free of ice by ca 16.9 ka. One, and in some cases two, closely spaced moraines extend up to 2 km beyond Little Ice Age moraines within many of the cirques in the region. The mean age of five 10Be ages from two pre-Little Ice Age moraines is 14.27-12.67 ka, whereas a minimum limiting radiocarbon age for a smaller, recessional moraine in one cirque is 12.38-12.01 ka. Our ages imply that, following glacier retreat beginning about 18.52-17.17 ka, cirque glaciers first advanced during the Antarctic Cold Reversal (14.5-12.9 ka) and may have later advanced or stabilized in the Younger Dryas Chronozone (12.9-11.7 ka). Based on the distribution of thick, geochemically distinct, and well-dated Hudson tephra, no Holocene moraines appear to be older than 7.96-7.34 ka. At some sites, there is evidence for one or more advances of glaciers sometime between 7.96-7.34 ka and 5.29-5.05 ka to limits only tens of meters beyond Little Ice Age maximum positions. Taken together, the data: 1) do not support the summer insolation hypothesis to explain Holocene glacier fluctuations in southernmost Patagonia; 2) confirm paleobotanical evidence for a warm, dry early Holocene; and 3) suggest that some glaciers in the region reached extents comparable to

  1. Early Site Permit Demonstration Program: Plant parameters envelope report. Volume 1

    SciTech Connect

    Not Available

    1993-03-01

    The Early Site Permit (ESP) Demonstration Program is the nuclear industry`s initiative for piloting the early resolution of siting-related issues before the detailed design proceedings of the combined operating license review. The ESP Demonstration Program consists of three phases. The plant parameters envelopes task is part of Phase 1, which addresses the generic review of applicable federal regulations and develops criteria for safety and environmental assessment of potential sites. The plant parameters envelopes identify parameters that characterize the interface between an ALWR design and a potential site, and quantify the interface through values selected from the Utility Requirements Documents, vendor design information, or engineering assessments. When augmented with site-specific information, the plant parameters envelopes provide sufficient information to allow ESPs to be granted based on individual ALWR design information or enveloping design information for the evolutionary, passive, or generic ALWR plants. This document is expected to become a living document when used by future applicants.

  2. Isolation basins, sea-level changes and the Holocene history of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Long, Antony J.; Woodroffe, Sarah A.; Roberts, David H.; Dawson, Sue

    2011-12-01

    Isolation basins are natural topographic depressions that at various times in their history may be connected to or isolated from the sea by changes in relative sea-level (RSL). They provide a valuable source of data for tracking large scale (tens of meters) changes in RSL over millennia, as well as quiet-water depositional environments where abrupt changes caused by tsunami, iceberg roll or storms may be recorded. In this paper we review isolation basins as sources of RSL data with a particular focus on their use in Greenland to constrain the Holocene history of the ice sheet. A new RSL curve from Disko Fjord, West Greenland is presented, which shows that local ice free conditions were established at c. 11 k cal yr BP, after which RSL fell rapidly from a marine limit at c. 80 m to reach close to present sea level by c. 4 k cal yr BP. We compare this record with other isolation basin RSL data from six other sites in Disko Bugt and note a strong northwest/southeast differential rebound across the area during the early and mid-Holocene that reflects variations in ice load history. We compare the Disko Bugt data with other previously published isolation basin RSL records from Sisimiut (central West Greenland), Nanortalik (south Greenland) and Ammassalik (southeast Greenland). RSL fell below present during the early-Holocene at Nanortalik (c. 10 k cal yr BP) and during the mid to late Holocene elsewhere before rising to present. These differences reflect variations in the timing and amount of Greenland ice load change since the last glacial maximum, as well as non-Greenland processes, notably the collapse of the Laurentide forebulge and also changes in ice equivalent sea-level. Isolation basin data have relatively small age and height uncertainties compared with other RSL indicators, enabling them to resolve between different earth and ice sheet models, especially during periods of large ice load and RSL change.

  3. The conservation of Holocene sediment archives in the Mediterranean and its relevance for geo-archaeology.

    NASA Astrophysics Data System (ADS)

    Sevink, J.; van Leusen, M.

    2012-04-01

    Mediterranean countries have laws and regulations that ensure the protection of their heritage, which often includes their 'geological heritage', such as in Italy where this geology is protected to an extent that is unknown to most Central and Northern European countries. This protection or geo-conservation, however, pertains largely to mineral and fossil bearing areas and sites, and rarely to relatively recent (Holocene to Late Quaternary) sediment archives. Such sediment archives play an increasingly important role in geo-archeology, allowing for precise dating and description of early cultures and their environment, as well as of the impact of man on his environment in connection with early land use and past climate changes. Holocene paleoecological archives are relatively scarce in the mediterranean, because of the climatic conditions which promote rapid and strong decomposition of organic remains. Current high quality archives pertain largely to crater lake and deep sea cores, which are hardly relevant for geo-archeology. Excellent archives may be available in coastal plains as was recently demonstrated for the Agro Pontino, allowing for detailed paleoecological studies as well as tephrochronological dating. Such archives are crucial for modern integrated geo-archeological studies and merit to be protected against degradation brought about by the often intensive agriculture in these plains that is marked by deep drainage and ploughing. In the Agro Pontino, such agriculture has already led to a virtually complete destruction of the Late Holocene (Roman and later) record in its former marshes. Based on this experience, authorities are strongly advised to include areas with important Holocene geo-archives in the geo-heritage to be conserved.

  4. Late Holocene climate: Natural or anthropogenic?

    NASA Astrophysics Data System (ADS)

    Ruddiman, W. F.; Fuller, D. Q.; Kutzbach, J. E.; Tzedakis, P. C.; Kaplan, J. O.; Ellis, E. C.; Vavrus, S. J.; Roberts, C. N.; Fyfe, R.; He, F.; Lemmen, C.; Woodbridge, J.

    2016-03-01

    For more than a decade, scientists have argued about the warmth of the current interglaciation. Was the warmth of the preindustrial late Holocene natural in origin, the result of orbital changes that had not yet driven the system into a new glacial state? Or was it in considerable degree the result of humans intervening in the climate system through greenhouse gas emissions from early agriculture? Here we summarize new evidence that moves this debate forward by testing both hypotheses. By comparing late Holocene responses to those that occurred during previous interglaciations (in section 2), we assess whether the late Holocene responses look different (and thus anthropogenic) or similar (and thus natural). This comparison reveals anomalous (anthropogenic) signals. In section 3, we review paleoecological and archaeological syntheses that provide ground truth evidence on early anthropogenic releases of greenhouse gases. The available data document large early anthropogenic emissions consistent with the anthropogenic ice core anomalies, but more information is needed to constrain their size. A final section compares natural and anthropogenic interpretations of the δ13C trend in ice core CO2.

  5. Patterns and drivers of Holocene vegetational change near the prairie-forest ecotone in Minnesota: revisiting McAndrews' transect.

    PubMed

    Nelson, David M; Hu, Feng Sheng

    2008-07-01

    Holocene vegetational dynamics along the prairie-forest border of Minnesota were first documented in McAndrews' classic work. Despite numerous subsequent paleo-studies, a number of questions remain unanswered about the vegetation history of the region. Here, pollen, stable-isotope, mineral, and charcoal data are described from three lakes near McAndrews' sites. These data were compared with other paleoenvironmental records to reconstruct vegetation, aridity, and fire. The climate was relatively wet with increasing summer temperatures before approximately 8000 yr before present (BP). The rates of changes were asymmetric for the onset and termination of middle-Holocene aridity, with an abrupt increase at approximately 8000 yr BP and a gradual, but variable, decline from approximately 7800 to 4000 yr BP. Early-Holocene coniferous forests changed to mixed-grass prairie without an intervening period of tallgrass prairie or deciduous forest, whereas the retreat of prairie was characterized by transitions from mixed-grass to tallgrass prairie to deciduous forest and finally to coniferous forest. Within the middle Holocene, the composition and structures of grass-dominated vegetation varied both temporally and spatially. Fire primarily responded to changes in climate and fuel loads. Vegetation was more strongly influenced by climatic changes than by fire-regime shifts. PMID:19086180

  6. The late devensian and holocene evolution of Barmouth Bay, Wales

    NASA Astrophysics Data System (ADS)

    Larcombe, Piers; Jago, Colin F.

    1994-03-01

    A marine seismic and sedimentological investigation of the Late-Devensian and Holocene sediments of Barmouth Bay, North Wales, was undertaken to reconstruct late-glacial and Holocene sedimentary environments, and to evaluate post-glacial sedimentation rates. In the last glacial, the Devensian, many Welsh estuaries were the sites of valley glaciers flowing from the Welsh Ice cap onto the modern inner-shelf. At Barmouth, the Mawddach valley glacier flowed into the present inner-shelf of Cardigan Bay. The modern courses of the Mawddach Estuary and the river Gwril were overdeepened by erosive sub-glacial flows, and are later infilled by a coarse-grained sub-glacial and pro-glacial infill sequence. With late-glacial relative sea-level rise and retreat of the Welsh Ice, the Mawddach valley tidewater glacier became grounded and confined to the valley. Re-equilibration of the ice profile occurred, and a morainal complex was formed at its toe. In the early Holocene, the morainal complex formed the seaward boundary of a sheltered nearshore basin where fine-grained, partly organic, sediments were deposited in a lagoonal or estuarine environment. Holocene reworking of the sediments by shallow-marine processes has formed a lag surface to the morainal complex, and has introduced gravel of Irish Sea Ice character from offshore. Wave action has formed a shingle coastal barrier, narrowing the mouth of the modern estuary. A shoreface-attached sand wedge, which attains a maximum thickness of 4 m beneath the modern ebb-tidal delta, overlies the lag surface and onlaps the coastal barrier. Since 8-9 ky BP, the mean sediment accumulation rate of estuarine and shallow-marine sediments has been 2.3-3.1 mm/yr, roughly equivalent to the long-term mean rate of sea-level rise for Cardigan Bay. This mean rate masks rapidly increasing accumulation rates in the Mawddach Estuary in the last 5-6 ky, which now may be 82 mm/yr, and which are due to reworking of shoreface and barrier sands into the

  7. Holocene aeolian sediments on the NE Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Stauch, G.; Lehmkuhl, F.; Hilgers, A.; Zhao, H.

    2012-04-01

    The semiarid climate of the northeastern Tibetan Plateau supports the formation of different types of aeolian sediments and landforms during the Holocene. Aeolians silts and sands in the catchment of the Donggi Cona in an elevation above 4000m to 4800 m asl reflect variable climate conditions during that time as well as different sediment sources. Based on 51 OSL datings and catchment wide geomorphological mapping a complex pattern of long and short distance sediment transport has been reconstructed. Only few aeolian archives are preserved from the late Pleistocene in this mountain environment indicating cold and dry climate conditions which prevented a continuous accumulation. During the early Holocene a phase of increased aeolian sedimentation of sand at the slopes of the mountains has been reconstructed. The sand originated from a large alluvial fan which was highly active during the Pleistocene. In addition, a thin loess cover is preserved at a few sites in the neighboring mountains ranges. The sedimentation of the loess started around 2000 years later than the sedimentation of the sand at the foot slope. Both archives are related to an increase in precipitation at the northern margin of the Tibetan Plateau which was related to a strengthening of the Asian Monsoon during that time. The wetter climate conditions favored the development of a vegetation cover which leads to the trapping and fixation of the aeolian sediments. However, with a further strengthening of the Monsoon systems these archives subsequently eroded due to higher run off and accumulated as colluvial and fluvial deposits in the basins. These phase lasted until 6 ka. A second aeolian period started at around 3 ka with the formation new dunes in the basins. This period can be associated with dry and cold climate of the late Holocene supporting the reactivation of the sand in the area. This might be further enhanced by an increased human impact by grazing during the late Holocene and resulting

  8. Turnover of binding sites for transcription factors involved in early Drosophila development.

    PubMed

    Costas, Javier; Casares, Fernando; Vieira, Jorge

    2003-05-22

    Despite the importance of cis-regulatory regions in evolution, little is know about their evolutionary dynamics. In this report, we analyze the process of evolution of binding sites for transcription factors using as a model a well characterized system, the Drosophila early developmental enhancers. We compare the sequences of eight enhancer regions for early developmental genes between Drosophila melanogaster and other two species, Drosophila virilis and Drosophila pseudoobscura, searching for the presence/absence of 104 biochemically verified binding sites from D. melanogaster. We also modeled the binding specificity of each binding site by the use of well-defined positional weight matrices (PWMs). The comparisons showed that turnover of binding sites seems to fit a molecular clock, at an approximate rate of 0.94% of gain/loss of binding sites per million years. This intense turnover affects both high and low affinity binding sites at the same extent. Furthermore, the subset of overlapping binding sites is also subjected to this high turnover. Conserved binding sites seem to be constrained to maintain not only location but also the exact sequence at each particular position. Finally, we detected a significant decrease in mean PWM scores for the D. virilis binding sites in the case of Hunchback. Possible explanations for this fact are discussed. PMID:12801649

  9. A model for the Holocene extinction of the mammal megafauna in Ecuador

    NASA Astrophysics Data System (ADS)

    Ficcarelli, G.; Coltorti, M.; Moreno-Espinosa, M.; Pieruccini, P. L.; Rook, L.; Torre, D.

    2003-03-01

    This paper presents the results of multidisciplinary research in the Ecuadorian coastal regions, with particular emphasis on the Santa Elena Peninsula. The new evidence, together with previous data gathered on the Ecuadorian cordillera during the last 12 years, allows us to formulate a model that accounts for most of the mammal megafauna extinction at the Pleistocene/Holocene transition. After the illustration of geomorphological and paleontological evidences of the area of the Santa Elena Peninsula (and other sites), and of a summary of the paleoclimatic data, the main results and conclusions of this work are: (1) Late Pleistocene mammal assemblages survived in the Ecuadorian coast until the Early Holocene sea level rise; (2) Prior to the extinction of most of the megafauna elements (mastodons, ground sloths, equids, sabre-tooth felids), the mammal communities at Santa Elena Peninsula comprise elements with differing habitat requirements, attesting conditions of high biological pressure; (3) At the El Cautivo site (Santa Elena Peninsula), we have discovered Holocene sediments containing the first known occurrences in Ecuador of lithic artifacts that are associated with mammal megafauna remains; (4) During the last 10,000 years, the coastal region of Ecuador underwent significant changes in vegetation cover. At the Pleistocene/Holocene transition the climate changed from very arid conditions to humid conditions. Our data indicates that the megafauna definitively abandoned the Cordillera areas around 12,000 yr BP due to t he increasing aridity, and subsequently migrated to coastal areas where ecological conditions still were suitable, Santa Elena Peninsula and mainly Amazonian areas being typical. We conclude that the unusual high faunal concentrations and the change to dense vegetation cover (due to a rapid increase in precipitation in the lower Holocene) at 8000-6000 yr BP, caused the final collapse and extinction of most elements of the mammal megafauna

  10. Late Holocene and recent rainforest cultural landscapes of North Queensland, Australia

    NASA Astrophysics Data System (ADS)

    Steinberger, L. M.; Moss, P. T.; Haberle, S.; Cosgrove, R.; Ferrier

    2011-12-01

    The tropical rainforests of North Queensland, Australia, have been environments of significant human activity for several thousand years. Palaeoecological research has highlighted the long-term effects of Quaternary climate change on these environments at a broad spatial scale, including the expansion of tropical rainforest across the region following the termination of the Last Glacial Maximum. However, identifying the effects of a hunter-gatherer Aboriginal population has been more difficult. Palaeoecological suggestions of Pleistocene Aboriginal burning, based on pollen and charcoal records, have relied on coincident timing with a general narrative of colonisation rather than direct links with archaeological evidence. Current research is explicitly examining the environmental consequences of human activity in North Queensland rainforests by producing local palaeoecological data directly linked to sites and periods of human occupation. Pollen, macrocharcoal and phytolith records have been produced from sites of human activity within the rainforest. Late Holocene Aboriginal occupation of the rainforest is demonstrated to have had significant cultural links to patches of open vegetation that existed within the rainforest. While these patches are likely to have originated as edaphically controlled remnants of Pleistocene vegetation, their expansion and maintenance in the late Holocene is associated with increasing intensity of Aboriginal occupation of the rainforest. Late Holocene Aboriginal rainforest occupation is also contrasted with the historical European colonisation of the rainforest in the late 19th century, which resulted in the most significant environmental changes in the region since the early Holocene. Historical and ethnographic records provide important cultural context for understanding the transition between Aboriginal and European cultural landscapes of the rainforest.

  11. Environmental evolution of the southern Chukchi Sea in the Holocene

    NASA Astrophysics Data System (ADS)

    Gusev, E. A.; Anikina, N. Yu.; Derevyanko, L. G.; Klyuvitkina, T. S.; Polyak, L. V.; Polyakova, E. I.; Rekant, P. V.; Stepanova, A. Yu.

    2014-07-01

    The molluscan shells from three drill and two piston cores obtained in the southern Russian sector of the Chukchi Sea are dated by the AMS 14C measurement method back to 0.8-3.5 and 9.2-10.5 ka. The period of 9-10 ka was marked by increased sedimentation rates related to the transgression onset. The fossils in the lower Holocene section exhibit the successive upward replacement of brackish-water organisms by their marine counterparts. After the opening of the Bering Strait in the middle Holocene, the sedimentation was under influence of the increased bioproductivity of the waters. The climatic optimum in the Chukotka region corresponds to the early Holocene, while the late Holocene was characterized by the wider development of the ice cover on the shelf.

  12. Tracking Nile Delta Vulnerability to Holocene Change

    PubMed Central

    Marriner, Nick; Flaux, Clément; Morhange, Christophe; Stanley, Jean-Daniel

    2013-01-01

    Understanding deltaic resilience in the face of Holocene climate change and human impacts is an important challenge for the earth sciences in characterizing the full range of present and future wetland responses to global warming. Here, we report an 8000-year mass balance record from the Nile Delta to reconstruct when and how this sedimentary basin has responded to past hydrological shifts. In a global Holocene context, the long-term decrease in Nile Delta accretion rates is consistent with insolation-driven changes in the ‘monsoon pacemaker’, attested throughout the mid-latitude tropics. Following the early to mid-Holocene growth of the Nile’s deltaic plain, sediment losses and pronounced erosion are first recorded after ~4000 years ago, the corollaries of falling sediment supply and an intensification of anthropogenic impacts from the Pharaonic period onwards. Against the backcloth of the Saharan ‘depeopling’, reduced river flow underpinned by a weakening of monsoonal precipitation appears to have been particularly conducive to the expansion of human activities on the delta by exposing productive floodplain lands for occupation and irrigation agriculture. The reconstruction suggests that the Nile Delta has a particularly long history of vulnerability to extreme events (e.g. floods and storms) and sea-level rise, although the present sediment-starved system does not have a direct Holocene analogue. This study highlights the importance of the world’s deltas as sensitive archives to investigate Holocene geosystem responses to climate change, risks and hazards, and societal interaction. PMID:23922692

  13. Discovery of a submerged relic reef and shoreline off Grand Cayman: further support for an early Holocene jump in sea level

    NASA Astrophysics Data System (ADS)

    Blanchon, Paul; Jones, Brian; Ford, Derek C.

    2002-03-01

    Drilling close to the base of a submerged sea-cliff on the terraced eastern shelf of Grand Cayman has revealed a relic Acropora palmata reef at a depth of 21 m below msl. Ten cores from its crest are principally composed of cobble-sized clasts of A. palmata set in a matrix of cemented skeletal grainstone. The clasts have a distinctive succession of encrusters that indicate rapid burial: a photophilic association of crustose coralline algae, foraminifera and vermetid gastropods superimposed by a cryptic association of sclerosponges, foraminifera and serpulids. In addition to rapid burial, U-Th thermal ionization mass spectrometer (TIMS) dating of coral clasts within 1 m of the relic-reef surface indicates minor temporal mixing with ages between 8.9 and 8.1 ka. Such mixing and rapid burial is consistent with a hurricane deposit and is identical to deposits found on the crests of modern reefs. In relation to its age, the preservation of a -18.5-m intertidal notch cut into the submerged sea-cliff on the western shelf of Grand Cayman implies that the crest of the relic reef has been lowered 1.5-2 m by marine abrasion/bioerosion at a rate of ˜0.25 mm yr -1. Reconstructing this eroded section using average Holocene accretion rates indicates that the reef likely ceased accreting at ˜7.6 ka at a depth of ˜19 m. Comparing these data with other relic reefs in the Caribbean indicates that the relic reef on Grand Cayman died within 160 years of relic reefs on Barbados, St. Croix, St. Thomas and north Florida. This narrow interval of reef demise also coincides with the time when modern reefs were establishing themselves some 4-9 m higher upslope—a fact that can only be resolved by invoking a rapid 6-m jump in sea level ˜7.5 ka ago. Such a jump would also account for two unexplained events around this time: the restricted interval of global delta initiation and the catastrophic flooding of the glacially lowered Black Sea.

  14. 10 CFR 2.621 - Acceptance and docketing of application for early review of site suitability issues in a combined...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Cfr Part 52 § 2.621 Acceptance and docketing of application for early review of site suitability... of site suitability issues in a combined license proceeding. 2.621 Section 2.621 Energy NUCLEAR... Procedures Applicable to Early Partial Decisions on Site Suitability Issues in Connection With an...

  15. 10 CFR 2.623 - Notice of hearing on application for early review of site suitability issues in combined license...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Early Partial Decisions on Site Suitability-Combined License Under 10 Cfr Part 52 § 2.623 Notice of... 10 Energy 1 2014-01-01 2014-01-01 false Notice of hearing on application for early review of site... Site Suitability Issues in Connection With an Application for a Construction Permit or Combined...

  16. 10 CFR 2.604 - Notice of hearing on application for early review of site suitability issues in construction...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Notice of hearing on application for early review of site... Site Suitability Issues in Connection With an Application for a Construction Permit or Combined License... Early Partial Decisions on Site Suitability-Construction Permit § 2.604 Notice of hearing on...

  17. 10 CFR 2.603 - Acceptance and docketing of application for early review of site suitability issues in a...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... of site suitability issues in a construction permit proceeding. 2.603 Section 2.603 Energy NUCLEAR... Procedures Applicable to Early Partial Decisions on Site Suitability Issues in Connection With an Application... Issuance of Limited Work Authorizations Early Partial Decisions on Site Suitability-Construction Permit §...

  18. 10 CFR 2.604 - Notice of hearing on application for early review of site suitability issues in construction...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Notice of hearing on application for early review of site... Site Suitability Issues in Connection With an Application for a Construction Permit or Combined License... Early Partial Decisions on Site Suitability-Construction Permit § 2.604 Notice of hearing on...

  19. 10 CFR 2.623 - Notice of hearing on application for early review of site suitability issues in combined license...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Early Partial Decisions on Site Suitability-Combined License Under 10 Cfr Part 52 § 2.623 Notice of... 10 Energy 1 2013-01-01 2013-01-01 false Notice of hearing on application for early review of site... Site Suitability Issues in Connection With an Application for a Construction Permit or Combined...

  20. A fluvial record of the mid-Holocene rapid climatic changes in the middle Rhone valley (Espeluche-Lalo, France) and of their impact on Late Mesolithic and Early Neolithic societies

    NASA Astrophysics Data System (ADS)

    Berger, Jean-François; Delhon, Claire; Magnin, Frédéric; Bonté, Sandrine; Peyric, Dominique; Thiébault, Stéphanie; Guilbert, Raphaele; Beeching, Alain

    2016-03-01

    This multi-proxy study of a small floodplain in the Rhone catchment area, at the northern edge of the Mediterranean morphoclimatic system, provides valuable information concerning the impact of mid-Holocene climate variability (8.5-7.0 ka) and the effects of two rapid climatic changes (8.2 and 7.7/7.1 ka) on an alluvial plain, its basin and the first farming societies of the Rhone valley. Around 7.7/7.1 ka, the combined effects of (1) a strong rate of change in insolation and (2) variations in solar activity amplified marine and atmospheric circulation in the north-west Atlantic (Bond event 5b), which imply continental hydrological, soil and vegetation changes in the small catchment area. For this period, strong fluctuations in the plant cover ratio have been identified, related to a regime of sustained and regular fires, as well as abundant erosion of the hill slopes and frequent fluvial metamorphoses which led to braiding of the watercourse in this floodplain. There are few data available to evaluate the impact of natural events on prehistoric communities. This continental archive offers clear multi-proxy data for discussion of these aspects, having 4 cultural layers interbedded in the fluvial sequence (1 Late Mesolithic, 3 Cardial/Epicardial). Earlier data indicate the difficulty in recognizing such cultural features in the low alluvial plains of southern France during the Mesolithic/Early Neolithic transition, which should lead to caution when developing settlement models for this period.

  1. Contributions to the Dart versus Arrow Debate: New Data from Holocene Projectile Points from Southeastern and Southern Brazil.

    PubMed

    Okumura, Mercedes; Araujo, Astolfo G M

    2015-01-01

    Lithic bifacial points are very common in the southern and southeastern regions of the Brazilian territory. Dated from Early to Late Holocene, these artifacts have not been studied in terms of their propulsion system. Given the characteristics of the bow and arrow compared to the atlatl and dart, there are important differences in the size and weight of arrowheads and dart points. Applying the techniques proposed by Shott (1997), Bradbury (1997), Fenenga (1953), Hughes (1998), and Hildebrandt and King (2012) to specimens recovered from eight sites dating from the early to the late Holocene, this work aims to present preliminary results to better understand the potential presence of darts and arrows in southeastern and southern Brazil. There was a variation in the results according to the application of different techniques. At least one set of points, dated from the Early Holocene, presented quite a high proportion of specimens classified as arrows, indicating the presence of points that could be used as arrowheads. PMID:26648546

  2. Lipid biomarkers in Holocene and glacial sediments from ancient Lake Ohrid (Macedonia, Albania)

    NASA Astrophysics Data System (ADS)

    Holtvoeth, J.; Vogel, H.; Wagner, B.; Wolff, G. A.

    2010-06-01

    Organic matter preserved in Lake Ohrid sediments originates from aquatic and terrestrial sources. Its variable composition reflects climate-controlled changes in the lake basin's hydrology and related organic matter export, i.e. changes in primary productivity, terrestrial plant matter input and soil erosion. Here, we present first results from lipid biomarker investigations of Lake Ohrid sediments from two near-shore settings: Site Lz1120 near the southern shore, with flat lands nearby and probably influenced by river discharge, and site Co1202 which is close to the steep eastern slopes. Variable proportions of terrestrial n-alkanoic acids and n-alkanols as well as compositional changes of ω-hydroxy acids document differences in soil organic matter supply between the sites and during different climate stages (glacial, Holocene, 8.2 ka cooling event). Changes in the vegetation cover are suggested by changes in the dominant chain length of terrestrial n-alkanols. Effective microbial degradation of labile organic matter and in situ contribution of organic matter derived from the microbes themselves are both evident in the sediments. We found evidence for anoxic conditions within the photic zone by detecting epicholestanol from sulphur-oxidising phototrophic bacteria and for the influence of an early human community from the occurrence of coprostanol, a biomarker for human and cattle faeces, in an early Holocene sample. This study illustrates the potential of lipid biomarkers for future environmental reconstructions using one of Europe's oldest continental climate archives, Lake Ohrid.

  3. Quantitative estimation of Holocene surface salinity variation in the Black Sea using dinoflagellate cyst process length

    NASA Astrophysics Data System (ADS)

    Mertens, Kenneth Neil; Bradley, Lee R.; Takano, Yoshihito; Mudie, Petra J.; Marret, Fabienne; Aksu, Ali E.; Hiscott, Richard N.; Verleye, Thomas J.; Mousing, Erik A.; Smyrnova, Ludmila L.; Bagheri, Siamak; Mansor, Mashhor; Pospelova, Vera; Matsuoka, Kazumi

    2012-04-01

    Reconstruction of salinity in the Holocene Black Sea has been an ongoing debate over the past four decades. Here we calibrate summer surface water salinity in the Black Sea, Sea of Azov and Caspian Sea with the process length of the dinoflagellate cyst Lingulodinium machaerophorum. We then apply this calibration to make a regional reconstruction of paleosalinity in the Black Sea, calculated by averaging out process length variation observed at four core sites from the Black Sea with high sedimentation rates and dated by multiple mollusk shell ages. Results show a very gradual change of salinity from ˜14 ± 0.91 psu around 9.9 cal ka BP to a minimum ˜12.3 ± 0.91 psu around 8.5 cal ka BP, reaching current salinities of ˜17.1 ± 0.91 psu around 4.1 cal ka BP. The resolution of our sampling is about 250 years, and it fails to reveal a catastrophic salinization event at ˜9.14 cal ka BP advocated by other researchers. The dinoflagellate cyst salinity-proxy does not record large Holocene salinity fluctuations, and after early Holocene freshening, it shows correspondence to the regional sea-level curve of Brückner et al. (2010) derived from Balabanov (2007).

  4. Holocene climate at Siple Dome, West Antarctica, using bubble number-density.

    NASA Astrophysics Data System (ADS)

    Spencer, M. K.; Dennison, A.; Alley, R. B.; Fitzpatrick, J. J.; Fegyveresi, J. M.

    2014-12-01

    Past allowable accumulation rate/temperature combinations from Holocene ice core samples at Siple Dome, West Antarctica, are estimated from the measured number-density of bubbles. Mass density increase and grain growth in polar firn both are controlled by temperature and accumulation rate, and their integrated effects are recorded in the number-density of bubbles as the firn changes to ice1, 2. Siple Dome bubble number-densities show an early-Holocene high in accumulation rate followed by an approximately 10% reduction in accumulation rate between 11.33 ka and 1.863 ka. 1. Spencer, M.K., R.B. Alley and J.J. Fitzpatrick. Developing a bubble number-density paleoclimatic indicator for glacier ice, J. Glaciol. 52(178), 358-364 (2006). 2. J.M. Fegyveresi, et al., Late-Holocene climate evolution at the WAIS Divide site, West Antarctica: bubble number-density estimates, J. Glaciol., 57(204) , 629 - 638 (2011).

  5. Allosteric vs. spontaneous exit-site (E-site) tRNA dissociation early in protein synthesis

    PubMed Central

    Chen, Chunlai; Stevens, Benjamin; Kaur, Jaskiran; Smilansky, Zeev; Cooperman, Barry S.; Goldman, Yale E.

    2011-01-01

    During protein synthesis, deacylated transfer RNAs leave the ribosome via an exit (E) site after mRNA translocation. How the ribosome regulates tRNA dissociation and whether functional linkages between the aminoacyl (A) and E sites modulate the dynamics of protein synthesis have long been debated. Using single molecule fluorescence resonance energy transfer experiments, we find that, during early cycles of protein elongation, tRNAs are often held in the E site until being allosterically released when the next aminoacyl tRNA binds to the A site. This process is regulated by the length and sequence of the nascent peptide and by the conformational state, detected by tRNA proximity, prior to translocation. In later cycles, E-site tRNA dissociates spontaneously. Our results suggest that the distribution of pretranslocation tRNA states and posttranslocation pathways are correlated within each elongation cycle via communication between distant subdomains in the ribosome, but that this correlation between elongation cycle intermediates does not persist into succeeding cycles. PMID:21969541

  6. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...) Commission finality. (1) Notwithstanding any provision in 10 CFR 50.109, while an early site permit is in... application for a license amendment, and must meet the requirements of 10 CFR 50.90 and 50.92. (f) Information... performed by the NRC staff must be in accordance with 10 CFR 50.54(f), and must be approved by the...

  7. Saugus Iron Works: Life and Work at an Early American Industrial Site. Teaching with Historic Places.

    ERIC Educational Resources Information Center

    Whitman, Maryann

    In 1948 archeologists verified that a now overgrown and urbanized landscape along the Saugus River (Massachusetts) was the site of the Saugus Iron Works from 1646 until 1648. That discovery led to a careful, though partly conjectural, reconstruction of the first successful integrated ironmaking plant in the colonial America. The early Puritan…

  8. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...) Commission finality. (1) Notwithstanding any provision in 10 CFR 50.109, while an early site permit is in... application for a license amendment, and must meet the requirements of 10 CFR 50.90 and 50.92. (f) Information... performed by the NRC staff must be in accordance with 10 CFR 50.54(f), and must be approved by the...

  9. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...) Commission finality. (1) Notwithstanding any provision in 10 CFR 50.109, while an early site permit is in... application for a license amendment, and must meet the requirements of 10 CFR 50.90 and 50.92. (f) Information... performed by the NRC staff must be in accordance with 10 CFR 50.54(f), and must be approved by the...

  10. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...) Commission finality. (1) Notwithstanding any provision in 10 CFR 50.109, while an early site permit is in... application for a license amendment, and must meet the requirements of 10 CFR 50.90 and 50.92. (f) Information... performed by the NRC staff must be in accordance with 10 CFR 50.54(f), and must be approved by the...

  11. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...) Commission finality. (1) Notwithstanding any provision in 10 CFR 50.109, while an early site permit is in... application for a license amendment, and must meet the requirements of 10 CFR 50.90 and 50.92. (f) Information... performed by the NRC staff must be in accordance with 10 CFR 50.54(f), and must be approved by the...

  12. Longitudinal Development of Antisocial Behaviors in Young and Early Adolescent Puerto Rican Children at Two Sites

    ERIC Educational Resources Information Center

    Bird, Hector R.; Shrout, Patrick E.; Davies, Mark; Canino, Glorisa; Duarte, Cristiane S.; Shen, Sa; Loeber, Rolf

    2007-01-01

    Objective: This report provides descriptive longitudinal findings over three waves of a study designed to assess the development of antisocial behaviors in young and early adolescent Puerto Rican children at two sites. Method: Through the use of standard assessment measures, representative samples of Puerto Rican children of both genders 5 to 13…

  13. 10 CFR 50.55 - Conditions of construction permits, early site permits, combined licenses, and manufacturing...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Conditions of construction permits, early site permits, combined licenses, and manufacturing licenses. 50.55 Section 50.55 Energy NUCLEAR REGULATORY COMMISSION DOMESTIC LICENSING OF PRODUCTION AND UTILIZATION FACILITIES Issuance, Limitations, and Conditions of Licenses and Construction Permits §...

  14. Fossil insects may provide unique information on structures and disturbances in past forest ecosystems - examples from Holocene studies in southern Sweden

    NASA Astrophysics Data System (ADS)

    Lemdahl, Geoffrey; Gustavsson, Gunnar; Olsson, Fredrik; Gaillard, Marie-José

    2010-05-01

    Insects are complex organisms that play an important role in all types of forest ecosystems. Insect remains are often abundant in waterlogged sediments and peat, and the majority of the fossils may be identified to species level, thus contributing with specific information. The occurrence of species feeding or confined to one or a few species of herbaceous plants, shrubs and trees may confirm or improve/refine the interpretations based on pollen and plant macrofossil analyses. Many insects, particularly ground living animals, select open, sun exposed habitats or closed shaded areas. Such indicators are valuable for reconstructions of forest/landscape openness. However, unique information can be provided by fossil insect assemblages. Insect studies carried out at two natural sites in southern Sweden with complete Holocene peat stratigraphies (Olsson and Lemdahl 2009) and a number of sites covering parts of the Holocene (e.g. Gaillard and Lemdahl 1994, Gustavsson et al. 2009) provide strong evidence on changes in forest structure and the occurrence and nature of disturbances. Studies in Britain have yielded similar results (e.g. Whitehouse 2006). Saproxylic beetles indicate the presence of dead wood, which clearly was a more prominent component in ancient woodlands than in present forests, and beetles confined to wood mould suggest the presence of large hollow trees. Finds of pyrophilic species, of which some are very rare in European woodlands today, together with layers of charcoal, suggest that fire was a major disturbance factor during most of the Holocene in southern Sweden. Whereas macroscopic charcoal fragments indicate local fires, the presence of pyrophilic insects is an indication of continuous fire activity at the regional spatial scale. Remains of dung beetles indicate extensive grazing by megaherbivores during early Holocene, and more intensive grazing during late Holocene, whereas such indicators are absent from mid Holocene records, which correlates

  15. Sea level changes in the Holocene

    SciTech Connect

    Tanner, W.F. )

    1993-03-01

    Beach ridge data provide much information on the history of sea level changes through all of Holocene time. Two data sets start at about 12,000 B.P., one of them essentially continuous to now with data every 40--50 yrs. Another starting at 7,600 B.P. is continuous to the present. Others span the last 3,200 years. These records agree reasonably closely, and show the Little Ice Age (since 1,200 A.D.). The sea level changes in these data include the following: (a) Early Holocene crisis, about 8,000 B.P. The Swedish (Baltic Sea) record ends about this time, the Hudson Bay record starts at roughly this time, and the Danish record has a 300--500-year gap at about this time. From the latter, it appears that sea level rose sharply, shortly before 8,000 B.P., and fell again shortly after 8,000 B.P. These were the largest changes in Holocene time. The vertical change may have been as much as 12--18 meters, and the rate of change as much as 5--8 cm/yr, perhaps the maximum possible. In stable areas, evidence for these changes are now 25--30 meters below sea level. (b) Early Holocene general rise, up to about 8,000 B.P. Evidence for this is now known only on uplifted coasts. (c) Middle Holocene high, 2 m above present MSL 7,000--5,500 B.P. (d) Middle Holocene low, 3--4 m below present MSL 5,000--3,500 B.P. (e) Several changes up to 2 meters, especially since 3,000 B.P. In general, rates of change have been close to 1 cm/yr (major exceptions noted above). The only persistent interval was that between beach ridges; each ridge and its associated swale seem to have been built by a sea-level rise-and-fall couplet, having dimensions so small (perhaps 5--30 cm) that they could be overlooked easily on tide-gauge records. The average apparent time interval was 35--50 years.

  16. Climate-driven expansion of blanket bogs in Britain during the Holocene

    NASA Astrophysics Data System (ADS)

    Gallego-Sala, A. V.; Charman, D. J.; Harrison, S. P.; Li, G.; Prentice, I. C.

    2016-01-01

    Blanket bog occupies approximately 6 % of the area of the UK today. The Holocene expansion of this hyperoceanic biome has previously been explained as a consequence of Neolithic forest clearance. However, the present distribution of blanket bog in Great Britain can be predicted accurately with a simple model (PeatStash) based on summer temperature and moisture index thresholds, and the same model correctly predicts the highly disjunct distribution of blanket bog worldwide. This finding suggests that climate, rather than land-use history, controls blanket-bog distribution in the UK and everywhere else. We set out to test this hypothesis for blanket bogs in the UK using bioclimate envelope modelling compared with a database of peat initiation age estimates. We used both pollen-based reconstructions and climate model simulations of climate changes between the mid-Holocene (6000 yr BP, 6 ka) and modern climate to drive PeatStash and predict areas of blanket bog. We compiled data on the timing of blanket-bog initiation, based on 228 age determinations at sites where peat directly overlies mineral soil. The model predicts that large areas of northern Britain would have had blanket bog by 6000 yr BP, and the area suitable for peat growth extended to the south after this time. A similar pattern is shown by the basal peat ages and new blanket bog appeared over a larger area during the late Holocene, the greatest expansion being in Ireland, Wales, and southwest England, as the model predicts. The expansion was driven by a summer cooling of about 2 °C, shown by both pollen-based reconstructions and climate models. The data show early Holocene (pre-Neolithic) blanket-bog initiation at over half of the sites in the core areas of Scotland and northern England. The temporal patterns and concurrence of the bioclimate model predictions and initiation data suggest that climate change provides a parsimonious explanation for the early Holocene distribution and later expansion of

  17. Climate-driven expansion of blanket bogs in Britain during the Holocene

    NASA Astrophysics Data System (ADS)

    Gallego-Sala, A. V.; Charman, D. J.; Harrison, S. P.; Li, G.; Prentice, I. C.

    2015-10-01

    Blanket bog occupies approximately 6 % of the area of the UK today. The Holocene expansion of this hyperoceanic biome has previously been explained as a consequence of Neolithic forest clearance. However, the present distribution of blanket bog in Great Britain can be predicted accurately with a simple model (PeatStash) based on summer temperature and moisture index thresholds, and the same model correctly predicts the highly disjunct distribution of blanket bog worldwide. This finding suggests that climate, rather than land-use history, controls blanket-bog distribution in the UK and everywhere else. We set out to test this hypothesis for blanket bogs in the UK using bioclimate envelope modelling compared with a database of peat initiation age estimates. We used both pollen-based reconstructions and climate model simulations of climate changes between the mid-Holocene (6000 yr BP, 6 ka) and modern climate to drive PeatStash and predict areas of blanket bog. We compiled data on the timing of blanket-bog initiation, based on 228 age determinations at sites where peat directly overlies mineral soil. The model predicts large areas of northern Britain would have had blanket bog by 6000 yr BP, and the area suitable for peat growth extended to the south after this time. A similar pattern is shown by the basal peat ages and new blanket bog appeared over a larger area during the late Holocene, the greatest expansion being in Ireland, Wales and southwest England, as the model predicts. The expansion was driven by a summer cooling of about 2 °C, shown by both pollen-based reconstructions and climate models. The data show early Holocene (pre-Neolithic) blanket-bog initiation at over half of the sites in the core areas of Scotland, and northern England. The temporal patterns and concurrence of the bioclimate model predictions and initiation data suggest that climate change provides a parsimonious explanation for the early Holocene distribution and later expansion of blanket

  18. Holocene environmental conditions in South Georgia - a multi-proxy study on a coastal marine record

    NASA Astrophysics Data System (ADS)

    Berg, Sonja; Jivcov, Sandra; Groten, Sonja; Viehberg, Finn; Rethemeyer, Janet; Melles, Martin

    2014-05-01

    The Holocene environmental history of the sub-Antarctic island of South Georgia so far has been reconstructed from lake sediments, peat records and geomorphological observations. The data available indicate a postglacial ice retreat, which reached the coastal areas around the early Holocene. Climate reconstructions for the Holocene, on the other hand, provide a more complex picture, which may partly result from the influence of local effects. We present preliminary results of a multi-proxy study on a sediment core recovered in early 2013 from a coastal marine inlet (Little Jason Lagoon) in Cumberland West Bay. The results include elemental data (high resolution XRF-scans, total organic carbon (TOC), nitrogen, and sulphur, lipid biomarkers, and macrofossil data. The sediment core comprises a c. 11m long sequence, which contains a complete record of postglacial sedimentation in the inlet. Its base is formed by a diamicton, indicating a former glaciation of the site, which is overlain by well-stratified sediments passing over into more massive muds in the upper past. A radiocarbon age from the organic-rich sediments above the diamicton provides a first estimate of 9700 14C years BP for a minimum age of ice retreat. We use the elemental data to infer changes in clastic input (e.g., K/Ti ratios), productivity (TOC) and water salinity (Cl counts) in the course of the Holocene. While Little Jason Lagoon has a connection to the sea today (sill depth c. 1 m), a decrease in Cl counts downcore points to fresher conditions in the early part of the record. This could be an indicator for changing relative sea level and/or changes in the amounts of freshwater inflow from the catchment. Macroscopic plant remains and lipid biomarkers (n-alkanes, n-fatty acids and sterols) provide information on the terrestrial vegetation in the catchment and its changes through time as well as on the influence of marine conditions in the lagoon. We suggest that the record from Little Jason Lagoon

  19. Holocene zooarchaeology and global change: Examples from the western US

    SciTech Connect

    Lyman, R.L. . Dept. of Anthropology)

    1993-03-01

    Mammalian faunal remains recovered from archaeological sites in the western US indicate that during the Holocene some taxa altered their ranges in response to climatic change whereas other taxa altered their ranges or migrational patterns due to historic commercial activities. The range of pygmy cottontail (Brachylagus idahoensis) in eastern Washington state shrank during the last 4,000 yrs in concert with a decrease in the range of big sagebrush (Artemisia tridentata). Recent biological surveys indicate that this taxon no longer occupies areas where it was found early in the 20th century, suggesting modern agricultural practices of burning and plowing sagebrush resulted in their local extirpation. Remains of newborn and female California sea lions (Zalophus californianus) and northern fur seals (Callorhinus ursinus) from late Holocene sites on the Oregon coast indicate that these species bred and pupped on this coast until the end of the 19 century. The absence of historical reports of these behaviors suggests that commercial exploitation of these species around the turn of the century resulted in the extirpation of local resident populations. In 1925 mountain goats (Oreamnos americanus) were introduced to what was to become Olympic National Park in Washington in 1938. Modern wildlife management policy calls for removal of this exotic, non-native species from Park lands. However, biogeographic data from archaeological excavations indicate great potential that mountain goats were extant on Park lands prehistorically. While conclusive evidence is not yet available, debates presently underway clearly indicate that the fossil record must play a role in modern wildlife management decisions.

  20. Predicting the macroseismic intensity from early radiated P wave energy for on-site earthquake early warning in Italy

    NASA Astrophysics Data System (ADS)

    Brondi, P.; Picozzi, M.; Emolo, A.; Zollo, A.; Mucciarelli, M.

    2015-10-01

    Earthquake Early Warning Systems (EEWS) are potentially effective tools for risk mitigation in active seismic regions. The present study explores the possibility of predicting the macroseismic intensity within EEW timeframes using the squared velocity integral (IV2) measured on the early P wave signals, a proxy for the P wave radiated energy of earthquakes. This study shows that IV2 correlates better than the peak displacement measured on P waves with both the peak ground velocity and the Housner Intensity, with the latter being recognized by engineers as a reliable proxy for damage assessment. Therefore, using the strong motion recordings of the Italian Accelerometric Archive, a novel relationship between the parameter IV2 and the macroseismic intensity (IM) has been derived. The validity of this relationship has been assessed using the strong motion recordings of the Istituto Nazionale di Geofisica e Vulcanologia Strong Motion Data and Osservatorio Sismico delle Strutture databases, as well as, in the case of the MW 6, 29 May 2012 Emilia earthquake (Italy), comparing the predicted intensities with the ones observed after a macroseismic survey. Our results indicate that P wave IV2 can become a key parameter for the design of on-site EEWS, capable of proving real-time predictions of the IM at target sites.

  1. Early reproductive success of the hard clam (Mercenaria mercenaria) from Five Sites in Long Island Sound

    SciTech Connect

    Stiles, S.; Choromanski, J.; Nelson, D.; Miller, J.; Greig, R.; Sennefelder, G. )

    1991-09-01

    Early reproductive success of hard clams (Mercenaria mercenaria) in Long Island Sound was measured to determine whether pollution may have adverse effects on fragile recruitment to fisheries. Clams were collected at five sites in 1987 when ready to spawn naturally, along with water from within 39 cm of the bottom. Levels of polychlorinated biphenyls (PCBs), copper, and cadmium were measured in the mature gonad and were found to be generally low. Clams were spawned and the gametes were collected and cultured both in their respective site waters and in reference laboratory seawater. In both site and reference seawater, embryos of clams from the most highly industrialized area (Bridgeport) with higher contaminant levels exhibited more irregularity in chromosome numbers and greater larval abnormality, possible indicators of long-term sublethal effects. Fertilization and early meiotic success at 1 to 1 1/2 h were significantly lower for clams from Norwalk than for those from Greenwich. At 48 h, mortality was lowest for Greenwich larvae and highest for Norwalk larvae in their respective site waters, but the mortality for these two sites was significantly lower than for other sites in reference water. This suggests sporadically poor environmental quality. Milford larvae also had significant mortality. Population-level significance of pollution effects on clam reproduction will depend on how contaminated the environment is over the entire reproductive season of the clams in Long Island Sound, and over how large a portion of the spawning grounds.

  2. Elucidating the Holocene Relative Sea-Level History of the US Atlantic Coast

    NASA Astrophysics Data System (ADS)

    Engelhart, S. E.; Anderson, C.; Hill, D.; Horton, B. P.; Peltier, W. R.; van de Plassche, O.; Shennan, I.; Thieler, E. R.; Tornqvist, T. E.

    2007-12-01

    There is an urgent need for a re-assessment of the quality of Holocene relative sea-level (RSL) observations from the Atlantic and Gulf coasts of the United States. Holocene RSL data provide an essential benchmark to compare against other records of RSL change in the last 100-150 years. Only high quality sea-level data reveal spatial and temporal variations in crustal movements since the Last Glacial Maximum and provide a vital constraint upon dynamical models of the Glacial Isostatic Adjustment (GIA) process. We require an accurate model of the GIA process to inform the global data set currently being produced on the time dependence of the gravitational field of the planet by the Gravity Recovery and Climate Experiment (GRACE). We have compiled database of 1400 possible sea-level index points for the Atlantic coast of the United States. These unvalidated data contain much scatter due to concepts inherent in their original interpretation. They rarely allow for other factors such as sediment compaction and tidal range variation. Following validation, results from Delaware and North Carolina show a rapid rise in RSL from the early to mid Holocene, with no evidence of sea- level above present. They also differ somewhat from GIA model predictions. Rates of RSL change during the late Holocene divide into three broad zones: (1) Maine to Boston, MA ~ RSL rise of less than 1 mm yr-1; (2) Cape Cod, MA to Maryland ~ RSL rise between 1 and 3 mm yr-1; and (3) North Carolina to South Carolina ~ RSL rise less than 1 mm yr-1. Comparison with tide-gauge records demonstrate an increase of at least 1 mm yr-1 at all sites since AD 1900.

  3. Long-term deforestation in NW Spain: linking the Holocene fire history to vegetation change and human activities

    NASA Astrophysics Data System (ADS)

    Kaal, Joeri; Carrión Marco, Yolanda; Asouti, Eleni; Martín Seijo, Maria; Martínez Cortizas, Antonio; Costa Casáis, Manuela; Criado Boado, Felipe

    2011-01-01

    The Holocene fire regime is thought to have had a key role in deforestation and shrubland expansion in Galicia (NW Spain) but the contribution of past societies to vegetation burning remains poorly understood. This may be, in part, due to the fact that detailed fire records from areas in close proximity to archaeological sites are scarce. To fill this gap, we performed charcoal analysis in five colluvial soils from an archaeological area (Campo Lameiro) and compared the results to earlier studies from this area and palaeo-ecological literature from NW Spain. This analysis allowed for the reconstruction of the vegetation and fire dynamics in the area during the last ca 11 000 yrs. In the Early Holocene, Fabaceae and Betula sp. were dominant in the charcoal record. Quercus sp. started to replace these species around 10 000 cal BP, forming a deciduous forest that prevailed during the Holocene Thermal Maximum until ˜5500 cal BP. Following that, several cycles of potentially fire-induced forest regression with subsequent incomplete recovery eventually led to the formation of an open landscape dominated by shrubs (Erica sp. and Fabaceae). Major episodes of forest regression were (1) ˜5500-5000 cal BP, which marks the mid-Holocene cooling after the Holocene Thermal Maximum, but also the period during which agropastoral activities in NW Spain became widespread, and (2) ˜2000-1500 cal BP, which corresponds roughly to the end of the Roman Warm Period and the transition from the Roman to the Germanic period. The low degree of chronological precision, which is inherent in fire history reconstructions from colluvial soils, made it impossible to distinguish climatic from human-induced fires. Nonetheless, the abundance of synanthropic pollen indicators (e.g. Plantago lanceolata and Urtica dioica) since at least ˜6000 cal BP strongly suggests that humans used fire to generate and maintain pasture.

  4. Peatland Carbon Dynamics on the North Slope of Alaska During the Holocene: The Role of Climate, Sea Ice, and Buried Peat

    NASA Astrophysics Data System (ADS)

    Yu, Zicheng; Massa, Charly; Cleary, Kathleen; Jones, Benjamin; Grosse, Guido

    2014-05-01

    Our recent and ongoing data syntheses indicate that peatlands accumulated more carbon (C) during past warm climate intervals in the circum-Arctic region, including Alaska. In particular, peak C accumulations have been observed during the Holocene Thermal Maximum (HTM) in the early Holocene when summer insolation was higher. However, we do not know the regional patterns and impacts of sea-ice change on Holocene peat C accumulation, especially around the Arctic Ocean where increased vegetation productivity has already been linked to sea ice declines in recent decades. Here we review Holocene peatland and tundra C accumulation records on the North Slope, along with our preliminary results, to investigate spatiotemporal pattern of C accumulation and the possible role of sea-ice change. As in many other northern high-latitude regions, most peatlands on the North Slope initiated in the early Holocene. Several discontinuous and low-resolution peat accumulation records from the region appear to show high accumulation rates or high C content in the early Holocene. In addition, we note that many peatlands that existed during the earlier Holocene on the North Slope have disappeared and are presently covered by mineral soils under tundra or eolian sandy deposits, indicating that current peatland extent is only a fraction of early Holocene extent. In contrast to highest C accumulation rates in the early Holocene, our preliminary results from a 70-cm-long peat core (lat. 70.71 N; long. 153.87 W) from northwest Teshekpuk Lake, near the Teshekpuk Lake Observatory on the Arctic Coastal Plain, about 10 km from the Arctic Ocean, shows a very different pattern. The highest C accumulation of 12.7 gC/m2/yr is observed after 2.9 ka, much higher than the rate of 3.8 gC/m2/yr at 8.1-2.9 ka. Furthermore, the period with high C rates after 2.9 ka at this site was dominated by well-preserved peat mosses (Sphagnum) and with abundant leaf fragments, likely from dwarf birch (Betula nana). This

  5. Centrosome movement in the early divisions of Caenorhabditis elegans: A cortical site determining centrosome position

    SciTech Connect

    Hyman, A.A. )

    1989-09-01

    In Caenorhabditis elegans embryos, early blastomeres of the P cell lineage divide successively on the same axis. This axis is a consequence of the specific rotational movement of the pair of centrosomes and nucleus. A laser has been used to perturb the centrosome movements that determine the pattern of early embryonic divisions. The results support a previously proposed model in which a centrosome rotates towards its correct position by shortening of connections, possibly microtubules, between a centrosome and a defined site on the cortex of the embryo.

  6. Chimpanzee nest distribution and site reuse in a dry habitat: implications for early hominin ranging.

    PubMed

    Hernandez-Aguilar, R Adriana

    2009-10-01

    This paper reports on a 20-month study of chimpanzee nesting patterns in Issa, Ugalla, western Tanzania. Ugalla is one of the driest, most open, and seasonal habitats where chimpanzees are found. The methods used were ethoarchaeological, as the chimpanzees were not habituated and behavioural observations were rare. Systematic data on the spatial and temporal distribution of nests are presented. Places with no nests at the beginning of the study, despite being suitable for nesting, were used as controls. Similar to other chimpanzee study sites, nests were highly concentrated in some parts of the landscape. Issa chimpanzees preferred to nest on slopes. They extensively used the woodland vegetation type of their habitat for nesting throughout the annual cycle. Ninety percent of nest sites were used repeatedly throughout the study period, but none of the control places had nests during this period. The results indicate that chimpanzees ranged more widely during the dry season, when food abundance was lowest, food was available mainly in open vegetation types, and when drinking water was restricted to a few sources. Early hominins in similar habitats may have followed the ranging strategy of Issa chimpanzees. As with a previous study, the distribution of nests was spatially similar to archaeological distributions in early hominin sites. Hominin topography and vegetation type preferences may be misrepresented in the archaeological record. Nest sites may have been the antecedents of carcass processing sites. PMID:19744699

  7. A high resolution Late Glacial to Holocene record of climatic and environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania)

    NASA Astrophysics Data System (ADS)

    Lacey, Jack; Francke, Alexander; Leng, Melanie; Vane, Chris; Wagner, Bernd

    2015-04-01

    Lake Ohrid (Macedonia/Albania) is one of the world's oldest lakes and is renowned for its high degree of biological diversity. It is the target site for the ICDP SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) project, an international research initiative to study the links between geology, environment and the evolution of endemic taxa. In 2011 a 10-meter core was recovered from the western shore of Lake Ohrid adjacent to the Lini Peninsula. Here we present high-resolution stable isotope and geochemical data from this core through the Late Glacial to Holocene to reconstruct past climate and hydrology (TIC, δ18Ocalcite, δ13Ccalcite) as well as the terrestrial and aquatic vegetation response to climate (TOC, TOC/N, δ13Corganic, Rock-Eval pyrolysis). The data identify 3 main zones: (1) the Late Glacial-Holocene transition represented by low TIC, TOC and higher isotope values, (2) the early to mid-Holocene characterised by higher TOC, TOC/N and lower δ18Ocalcite, and (3) the late Holocene which shows a marked decrease in TIC and TOC. In general there is an overall trend of increasing δ18Ocalcite from 9 ka to present, suggesting progressive aridification through the Holocene, which is consistent with previous records from Lake Ohrid and the wider Mediterranean region. Several proxies show commensurate excursions that imply the impact of short-term climate oscillations, such as the 8.2 ka event and the Little Ice Age. This is the best-dated and highest resolution archive of Late Glacial and Holocene climate from Lake Ohrid and confirms the overriding influence of the North Atlantic in the north-eastern Mediterranean. The data presented set the context for the SCOPSCO project cores recovered in spring-summer 2013 dating back into the Lower Pleistocene, and will act as a recent calibration to reconstruct climate and hydrology over the entire lake history.

  8. 10 CFR 51.75 - Draft environmental impact statement-construction permit, early site permit, or combined license.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... evaluation of alternative energy sources, unless these matters are addressed in the early site permit... 10 Energy 2 2014-01-01 2014-01-01 false Draft environmental impact statement-construction permit, early site permit, or combined license. 51.75 Section 51.75 Energy NUCLEAR REGULATORY...

  9. 10 CFR 51.75 - Draft environmental impact statement-construction permit, early site permit, or combined license.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... evaluation of alternative energy sources, unless these matters are addressed in the early site permit... 10 Energy 2 2013-01-01 2013-01-01 false Draft environmental impact statement-construction permit, early site permit, or combined license. 51.75 Section 51.75 Energy NUCLEAR REGULATORY...

  10. 10 CFR 51.75 - Draft environmental impact statement-construction permit, early site permit, or combined licesne.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... evaluation of alternative energy sources, unless these matters are addressed in the early site permit... 10 Energy 2 2010-01-01 2010-01-01 false Draft environmental impact statement-construction permit, early site permit, or combined licesne. 51.75 Section 51.75 Energy NUCLEAR REGULATORY...

  11. 10 CFR 51.75 - Draft environmental impact statement-construction permit, early site permit, or combined licesne.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... evaluation of alternative energy sources, unless these matters are addressed in the early site permit... 10 Energy 2 2011-01-01 2011-01-01 false Draft environmental impact statement-construction permit, early site permit, or combined licesne. 51.75 Section 51.75 Energy NUCLEAR REGULATORY...

  12. Report of the Peer Review Panel on the early site suitability evaluation of the Potential Repository Site at Yucca Mountain, Nevada; Yucca Mountain Site Characterization Project

    SciTech Connect

    1992-01-01

    The US Department of Energy (DOE) Yucca mountain Site Characterization Project Office (YMPO) assigned Science Applications International Corporation (SAIC), the Technical and Management Support Services (T&MSS) contractor to the YmPo, the task of conducting an Early Site Suitability Evaluation (ESSE) of the Yucca mountain site as a potential site for a high-level radioactive waste repository. First, the assignment called for the development of a method to evaluate a single site against the DOE General Guidelines for Recommendation of Sites for Nuclear Waste Repositories, 10 CFR Part 960. Then, using this method, an evaluation team, the ESSE Core Team, of senior YMP scientists, engineers, and technical experts, evaluated new information obtained about the site since publication of the final Environmental Assessment (DOE, 1986) to determine if new suitability/unsuitability findings could be recommended. Finally, the Core Team identified further information and analyses needed to make final determinations for each of the guidelines. As part of the task, an independent peer review of the ESSE report has been conducted. Expertise was solicited that covered the entire spectrum of siting guidelines in 10 CFR Part 960 in order to provide a complete, in-depth critical review of the data evaluated and cited in the ESSE report, the methods used to evaluate the data, and the conclusions and recommendations offered by the report. Fourteen nationally recognized technical experts (Table 2) served on the Peer Review Panel. The comments from the Panel and the responses prepared by the ESSE Core Team, documented on formal Comment Response Forms, constitute the body of this document.

  13. Clinal variation of some mammals during the Holocene in Missouri

    NASA Astrophysics Data System (ADS)

    Purdue, James R.

    1980-03-01

    Eastern cottontail ( Sylvilagus floridanus), fox squirrel ( Sciurus niger), and gray squirrel ( Sciurus carolinensis) were examined for clinal variation during the Holocene. Modern samples of all three species displayed strong east-west patterns along the western edge of the eastern deciduous forest: S. floridanus and S. niger decrease and S. carolinensis increases in size. Archeological samples of S. carolinensis from Rodgers Shelter (23BE125), Benton County, Missouri, and Graham Cave (23MT2), Montgomery County, Missouri, indicated an increase in size from early to middle Holocene. Sylvilagus floridanus from Rodgers Shelter decreased in size from early to middle Holocene and then increased during the late Holocene to modern proportions. A literature survey reveals that clinal variation is a common phenomenon among modern homeotherms. In introduced species, clinal variation has developed after relatively few generations, indicating rapid adaptations to environmental conditions; often winter climatic variables are implicated. Morphological variation in the study species during the Holocene is interpreted as a response to changing climates. Studies of morphological clines may lead to another valuable data source for reconstructing past ecologies.

  14. Glacial discharge, upwelling and productivity off the Adélie coast, Antarctica: results from a 171 m Holocene sediment core from IODP Expedition 318

    NASA Astrophysics Data System (ADS)

    Newton, Kate; Bendle, James; McKay, Robert; Albot, Anya; Moossen, Heiko; Seki, Osamu; Willmott, Veronica; Schouten, Stefan; Riesselman, Christina; Dunbar, Robert

    2016-04-01

    Antarctica's coastal oceans play a vital role in controlling both the global carbon cycle and climate change, through variations in primary production, ocean stratification and ice melt. Yet, the Southern Ocean remains the least studied region on Earth with respect to Holocene climate variability. The few Antarctic proximal marine sedimentary records available tend to be short, low resolution, and discontinuous. However, sediments recovered from the Adélie drift during IODP Expedition 318 present a new opportunity to study East Antarctic Holocene climatic evolution, at a resolution that facilitates direct comparison with ice-cores. A 171m core of Holocene laminated diatom ooze was recovered from site U1357, representing continuous Holocene accumulation in a climatically-sensitive coastal polynya. We present results of biomarker analyses (TEX86-L and compound specific fatty acid delta-D and delta-13C, and sterol delta-D) and grain size from throughout the Holocene, revealing the complexities of this climatically sensitive environment. Carbon isotopes are interpreted predominantly as a productivity signal via CO2 drawdown, whilst hydrogen isotopes reflect inputs of isotopically-depleted glacial meltwater from the large Mertz glacier tongue and other proximal glaciers. Both upwelling, as shown by TEX86-L and grain size, and glacial meltwater inputs, indicated by biomarker delta-D, appear to have an important control on productivity on various time scales. The latter may be forced by warm subsurface temperatures through basal melting of the Mertz glacier tongue, indicating both direct and indirect effects of upwelling on productivity. The post-glacial, Early Holocene appears to be characterized by a highly variable system, due to both strong upwelling and meltwater inputs, followed by a more stable and highly productive Middle Holocene under a warmer climate. During the Late Holocene, characterized by a sea-ice expansion, temperature-induced sea-ice melt may have

  15. Rapid Estimation of Macroseismic Intensity for On-site Earthquake Early Warning in Italy from Early Radiated Energ

    NASA Astrophysics Data System (ADS)

    Emolo, A.; Zollo, A.; Brondi, P.; Picozzi, M.; Mucciarelli, M.

    2015-12-01

    Earthquake Early Warning System (EEWS) are effective tools for the risk mitigation in active seismic regions. Recently, a feasibility study of a nation-wide earthquake early warning systems has been conducted for Italy considering the RAN Network and the EEW software platform PRESTo. This work showed that a reliable estimations in terms of magnitude and epicentral localization would be available within 3-4 seconds after the first P-wave arrival. On the other hand, given the RAN's density, a regional EEWS approach would result in a Blind Zone (BZ) of 25-30 km in average. Such BZ dimension would provide lead-times greater than zero only for events having magnitude larger than 6.5. Considering that in Italy also smaller events are capable of generating great losses both in human and economic terms, as dramatically experienced during the recent 2009 L'Aquila (ML 5.9) and 2012 Emilia (ML 5.9) earthquakes, it has become urgent to develop and test on-site approaches. The present study is focused on the development of a new on-site EEW metodology for the estimation of the macroseismic intensity at a target site or area. In this analysis we have used a few thousands of accelerometric traces recorded by RAN related to the largest earthquakes (ML>4) occurred in Italy in the period 1997-2013. The work is focused on the integral EW parameter Squared Velocity Integral (IV2) and on its capability to predict the peak ground velocity PGV and the Housner Intensity IH, as well as from these latters we parameterized a new relation between IV2 and the Macroseismic Intensity. To assess the performance of the developed on-site EEW relation, we used data of the largest events occurred in Italy in the last 6 years recorded by the Osservatorio Sismico delle Strutture, as well as on the recordings of the moderate earthquake reported by INGV Strong Motion Data. The results shows that the macroseismic intensity values predicted by IV2 and the one estimated by PGV and IH are in good agreement.

  16. Changes in Colorado Subalpine Fen Peat Stratigraphy and Humification During the Holocene

    NASA Astrophysics Data System (ADS)

    Sullivan, D. G.

    2013-12-01

    This project focuses on the record of peat stratigraphy and decomposition preserved in cores taken from minerotrophic peatlands in Colorado. Subalpine peatlands in the Colorado Rocky Mountains and in the Colorado Plateau cover only about 2% of the state's land area, yet these wetlands provide important wildlife habitat and ecosystem services. The peatlands in Colorado are fens, and, while summer precipitation contributes to the local hydrology, the fens are only found in locations where winter snowpack persists long enough into the summers to maintain sufficiently high water tables to preserve the peat. We hypothesized that changes in summer precipitation and winter snowpack through the Holocene would be evident in the degree of peat humification and stratigraphy. We were interested in determining how warmer summer conditions early in the Holocene influenced precipitation, particularly summer monsoons, and thus, groundwater. In addition, our research using lake sediment cores in the region indicates that sediment organic content may fluctuate with paleotemperature. We sought to determine whether fens likewise preserve evidence of relatively low magnitude temperature changes, including those associated with the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). Since fens persist in the region only under marginal conditions, they are very sensitive to fluctuations in climate and consequent hydrological responses. Nine fens were sampled in the study. Fen stratigraphy was studied at all of the sites. Humification analysis and bulk density and organic content determinations were conducted at one-centimeter intervals on cores from four of the fens. Core chronology was established using radiocarbon dating. Our results suggest that warmer summers in the early Holocene led to earlier snowmelt at lower elevations. Fens located near the lower margins of the subalpine zone (<3100 m elevation) ceased to accumulate peat during this period, changing to alluvial

  17. Early atmospheric detection of carbon dioxide from carbon capture and storage sites

    PubMed Central

    Pak, Nasrin Mostafavi; Rempillo, Ofelia; Norman, Ann-Lise; Layzell, David B.

    2016-01-01

    ABSTRACT The early atmospheric detection of carbon dioxide (CO2) leaks from carbon capture and storage (CCS) sites is important both to inform remediation efforts and to build and maintain public support for CCS in mitigating greenhouse gas emissions. A gas analysis system was developed to assess the origin of plumes of air enriched in CO2, as to whether CO2 is from a CCS site or from the oxidation of carbon compounds. The system measured CO2 and O2 concentrations for different plume samples relative to background air and calculated the gas differential concentration ratio (GDCR = −ΔO2/ΔCO2). The experimental results were in good agreement with theoretical calculations that placed GDCR values for a CO2 leak at 0.21, compared with GDCR values of 1–1.8 for the combustion of carbon compounds. Although some combustion plume samples deviated in GDCR from theoretical, the very low GDCR values associated with plumes from CO2 leaks provided confidence that this technology holds promise in providing a tool for the early detection of CO2 leaks from CCS sites.  Implications: This work contributes to the development of a cost-effective technology for the early detection of leaks from sites where CO2 has been injected into the subsurface to enhance oil recovery or to permanently store the gas as a strategy for mitigating climate change. Such technology will be important in building public confidence regarding the safety and security of carbon capture and storage sites. PMID:27111469

  18. Holocene changes of Andean alder (Alnus acuminata) in highland Ecuador and Peru

    NASA Astrophysics Data System (ADS)

    Weng, Chengyu; Bush, Mark B.; Chepstow-Lusty, Alex J.

    2004-10-01

    Fossil pollen records from the high Andes of Ecuador and northern Peru show that Alnus increased in abundance at most sites following warming associated with the onset of the Holocene. The peak of Alnus pollen abundance occurred between 9000 and 5000 yr BP. However, between 6500 and 4500 yr BP, the abundance of Alnus pollen declined markedly in all of the available records, including sites both within and above its modern distribution range. Even though the beginning of this decline may have been time-transgressive, the greatest reduction of Alnus abundance is consistent between sites, occurring at ca. 4500 yr BP. This synchrony suggests that one or more factors affected Alnus populations across the whole region. A cooler climate, droughts and anthropogenic activity are discussed as possible causes on such a large spatial scale. A scenario is suggested in which the early-mid Holocene increase in Alnus populations was curtailed by droughts, and then further impacted by major regional cooling from ca. 5000 yr BP onwards. Human agricultural activities in this wetter interval may also have delayed Alnus recovery. A resurgence of Alnus populations at 2000-1000 yr BP may have been a response to regional warming coupled with human land management practices. Copyright

  19. Precipitation variability of the Grand Canyon region, 1893 through 2009, and its implications for studying effects of gullying of Holocene terraces and associated archeological sites in Grand Canyon, Arizona

    USGS Publications Warehouse

    Hereford, Richard; Bennett, Glenn E.; Fairley, Helen C.

    2014-01-01

    A daily precipitation dataset covering a large part of the American Southwest was compiled for online electronic distribution (http://pubs.usgs.gov/of/2014/1006/). The dataset contains 10.8 million observations spanning January 1893 through January 2009 from 846 weather stations in six states and 13 climate divisions. In addition to processing the data for distribution, water-year totals and other statistical parameters were calculated for each station with more than 2 years of observations. Division-wide total precipitation, expressed as the average deviation from the individual station means of a climate division, shows that the region—including the Grand Canyon, Arizona, area—has been affected by alternating multidecadal episodes of drought and wet conditions. In addition to compiling and analyzing the long-term regional precipitation data, a second dataset consisting of high-temporal-resolution precipitation measurements collected between November 2003 and January 2009 from 10 localities along the Colorado River in Grand Canyon was compiled. An exploratory study of these high-temporal-resolution precipitation measurements suggests that on a daily basis precipitation patterns are generally similar to those at a long-term weather station in the canyon, which in turn resembles the patterns at other long-term stations on the canyon rims; however, precipitation amounts recorded by the individual inner canyon weather stations can vary substantially from station to station. Daily and seasonal rainfall patterns apparent in these data are not random. For example, the inner canyon record, although short and fragmented, reveals three episodes of widespread, heavy precipitation in late summer 2004, early winter 2005, and summer 2007. The 2004 event and several others had sufficient rainfall to initiate potentially pervasive erosion of the late Holocene terraces and related archeological features located along the Colorado River in Grand Canyon.

  20. Extraction of Functional Binding Sites from Unique Regulatory Regions: The Drosophila Early Developmental Enhancers

    PubMed Central

    Papatsenko, Dmitri A.; Makeev, Vsevolod J.; Lifanov, Alex P.; Régnier, Mireille; Nazina, Anna G.; Desplan, Claude

    2002-01-01

    The early developmental enhancers of Drosophila melanogaster comprise one of the most sophisticated regulatory systems in higher eukaryotes. An elaborate code in their DNA sequence translates both maternal and early embryonic regulatory signals into spatial distribution of transcription factors. One of the most striking features of this code is the redundancy of binding sites for these transcription factors (BSTF). Using this redundancy, we explored the possibility of predicting functional binding sites in a single enhancer region without any prior consensus/matrix description or evolutionary sequence comparisons. We developed a conceptually simple algorithm, Scanseq, that employs an original statistical evaluation for identifying the most redundant motifs and locates the position of potential BSTF in a given regulatory region. To estimate the biological relevance of our predictions, we built thorough literature-based annotations for the best-known Drosophila developmental enhancers and we generated detailed distribution maps for the most robust binding sites. The high statistical correlation between the location of BSTF in these experiment-based maps and the location predicted in silico by Scanseq confirmed the relevance of our approach. We also discuss the definition of true binding sites and the possible biological principles that govern patterning of regulatory regions and the distribution of transcriptional signals. PMID:11875036

  1. North Atlantic forcing of moisture delivery to Europe throughout the Holocene

    PubMed Central

    Smith, Andrew C.; Wynn, Peter M.; Barker, Philip A.; Leng, Melanie J.; Noble, Stephen R.; Tych, Wlodek

    2016-01-01

    Century-to-millennial scale fluctuations in precipitation and temperature are an established feature of European Holocene climates. Changes in moisture delivery are driven by complex interactions between ocean moisture sources and atmospheric circulation modes, making it difficult to resolve the drivers behind millennial scale variability in European precipitation. Here, we present two overlapping decadal resolution speleothem oxygen isotope (δ18O) records from a cave on the Atlantic coastline of northern Iberia, covering the period 12.1–0 ka. Speleothem δ18O reveals nine quasi-cyclical events of relatively wet-to-dry climatic conditions during the Holocene. Dynamic Harmonic Regression modelling indicates that changes in precipitation occurred with a ~1500 year frequency during the late Holocene and at a shorter length during the early Holocene. The timing of these cycles coincides with changes in North Atlantic Ocean conditions, indicating a connectivity between ocean conditions and Holocene moisture delivery. Early Holocene climate is potentially dominated by freshwater outburst events, whilst ~1500 year cycles in the late Holocene are more likely driven by changes internal to the ocean system. This is the first continental record of its type that clearly demonstrates millennial scale connectivity between the pulse of the ocean and precipitation over Europe through the entirety of the Holocene. PMID:27109216

  2. North Atlantic forcing of moisture delivery to Europe throughout the Holocene.

    PubMed

    Smith, Andrew C; Wynn, Peter M; Barker, Philip A; Leng, Melanie J; Noble, Stephen R; Tych, Wlodek

    2016-01-01

    Century-to-millennial scale fluctuations in precipitation and temperature are an established feature of European Holocene climates. Changes in moisture delivery are driven by complex interactions between ocean moisture sources and atmospheric circulation modes, making it difficult to resolve the drivers behind millennial scale variability in European precipitation. Here, we present two overlapping decadal resolution speleothem oxygen isotope (δ(18)O) records from a cave on the Atlantic coastline of northern Iberia, covering the period 12.1-0 ka. Speleothem δ(18)O reveals nine quasi-cyclical events of relatively wet-to-dry climatic conditions during the Holocene. Dynamic Harmonic Regression modelling indicates that changes in precipitation occurred with a ~1500 year frequency during the late Holocene and at a shorter length during the early Holocene. The timing of these cycles coincides with changes in North Atlantic Ocean conditions, indicating a connectivity between ocean conditions and Holocene moisture delivery. Early Holocene climate is potentially dominated by freshwater outburst events, whilst ~1500 year cycles in the late Holocene are more likely driven by changes internal to the ocean system. This is the first continental record of its type that clearly demonstrates millennial scale connectivity between the pulse of the ocean and precipitation over Europe through the entirety of the Holocene. PMID:27109216

  3. North Atlantic forcing of moisture delivery to Europe throughout the Holocene

    NASA Astrophysics Data System (ADS)

    Smith, Andrew C.; Wynn, Peter M.; Barker, Philip A.; Leng, Melanie J.; Noble, Stephen R.; Tych, Wlodek

    2016-04-01

    Century-to-millennial scale fluctuations in precipitation and temperature are an established feature of European Holocene climates. Changes in moisture delivery are driven by complex interactions between ocean moisture sources and atmospheric circulation modes, making it difficult to resolve the drivers behind millennial scale variability in European precipitation. Here, we present two overlapping decadal resolution speleothem oxygen isotope (δ18O) records from a cave on the Atlantic coastline of northern Iberia, covering the period 12.1–0 ka. Speleothem δ18O reveals nine quasi-cyclical events of relatively wet-to-dry climatic conditions during the Holocene. Dynamic Harmonic Regression modelling indicates that changes in precipitation occurred with a ~1500 year frequency during the late Holocene and at a shorter length during the early Holocene. The timing of these cycles coincides with changes in North Atlantic Ocean conditions, indicating a connectivity between ocean conditions and Holocene moisture delivery. Early Holocene climate is potentially dominated by freshwater outburst events, whilst ~1500 year cycles in the late Holocene are more likely driven by changes internal to the ocean system. This is the first continental record of its type that clearly demonstrates millennial scale connectivity between the pulse of the ocean and precipitation over Europe through the entirety of the Holocene.

  4. Holocene aridification of India

    NASA Astrophysics Data System (ADS)

    Ponton, Camilo; Giosan, Liviu; Eglinton, Tim I.; Fuller, Dorian Q.; Johnson, Joel E.; Kumar, Pushpendra; Collett, Tim S.

    2012-02-01

    Spanning a latitudinal range typical for deserts, the Indian peninsula is fertile instead and sustains over a billion people through monsoonal rains. Despite the strong link between climate and society, our knowledge of the long-term monsoon variability is incomplete over the Indian subcontinent. Here we reconstruct the Holocene paleoclimate in the core monsoon zone (CMZ) of the Indian peninsula using a sediment core recovered offshore from the mouth of Godavari River. Carbon isotopes of sedimentary leaf waxes provide an integrated and regionally extensive record of the flora in the CMZ and document a gradual increase in aridity-adapted vegetation from ˜4,000 until 1,700 years ago followed by the persistence of aridity-adapted plants after that. The oxygen isotopic composition of planktonic foraminifer Globigerinoides ruber detects unprecedented high salinity events in the Bay of Bengal over the last 3,000 years, and especially after 1,700 years ago, which suggest that the CMZ aridification intensified in the late Holocene through a series of sub-millennial dry episodes. Cultural changes occurred across the Indian subcontinent as the climate became more arid after ˜4,000 years. Sedentary agriculture took hold in the drying central and south India, while the urban Harappan civilization collapsed in the already arid Indus basin. The establishment of a more variable hydroclimate over the last ca. 1,700 years may have led to the rapid proliferation of water-conservation technology in south India.

  5. Deletion at Fragile Sites is a Common and Early Event in Barrett’s Esophagus

    PubMed Central

    Lai, Lisa A.; Kostadinov, Rumen; Barrett, Michael T.; Peiffer, Daniel A.; Pokholok, Dimitry; Odze, Robert; Sanchez, Carissa A.; Maley, Carlo C.; Reid, Brian J.; Gunderson, Kevin L.; Rabinovitch, Peter S.

    2011-01-01

    Barrett’s esophagus is a premalignant intermediate to esophageal adenocarcinoma, which develops in the context of chronic inflammation and exposure to bile and acid. We asked whether there might be common genomic alterations that could be identified as potential clinical biomarker(s) for Barrett’s esophagus by whole genome profiling. We detected copy number alterations and/or loss of heterozygosity (LOH) at fifty-six fragile sites in 20 patients with premalignant Barrett’s esophagus (BE). Chromosomal fragile sites are particularly sensitive to DNA breaks and have been shown to be frequent sites of rearrangement or loss in many human cancers. 78% of all genomic alterations detected by array-CGH were associated with fragile sites. Copy number losses in early BE were observed at particularly high frequency at FRA3B (81%), FRA9A/C (71.4%), FRA5E (52.4%) and FRA 4D (52.4%), and at lower frequencies in other fragile sites, including FRA1K (42.9%), FRAXC (42.9%), FRA 12B (33.3%) and FRA16D (33.3%). Due to the consistency of the region of copy number loss, we were able to verify these results by quantitative PCR which detected loss of FRA3B and FRA16D, in 83% and 40% of early molecular stage BE patients respectively. LOH in these cases was confirmed via pyrosequencing at FRA3B and FRA16D (75% and 70% respectively). Deletion and genomic instability at FRA3B and other fragile sites could thus be a biomarker of genetic damage in BE patients and a potential biomarker of cancer risk. PMID:20647332

  6. Deletion at fragile sites is a common and early event in Barrett's esophagus.

    PubMed

    Lai, Lisa A; Kostadinov, Rumen; Barrett, Michael T; Peiffer, Daniel A; Pokholok, Dimitry; Odze, Robert; Sanchez, Carissa A; Maley, Carlo C; Reid, Brian J; Gunderson, Kevin L; Rabinovitch, Peter S

    2010-08-01

    Barrett's esophagus (BE) is a premalignant intermediate to esophageal adenocarcinoma, which develops in the context of chronic inflammation and exposure to bile and acid. We asked whether there might be common genomic alterations that could be identified as potential clinical biomarker(s) for BE by whole genome profiling. We detected copy number alterations and/or loss of heterozygosity at 56 fragile sites in 20 patients with premalignant BE. Chromosomal fragile sites are particularly sensitive to DNA breaks and are frequent sites of rearrangement or loss in many human cancers. Seventy-eight percent of all genomic alterations detected by array-CGH were associated with fragile sites. Copy number losses in early BE were observed at particularly high frequency at FRA3B (81%), FRA9A/C (71.4%), FRA5E (52.4%), and FRA 4D (52.4%), and at lower frequencies in other fragile sites, including FRA1K (42.9%), FRAXC (42.9%), FRA 12B (33.3%), and FRA16D (33.3%). Due to the consistency of the region of copy number loss, we were able to verify these results by quantitative PCR, which detected the loss of FRA3B and FRA16D, in 83% and 40% of early molecular stage BE patients, respectively. Loss of heterozygosity in these cases was confirmed through pyrosequencing at FRA3B and FRA16D (75% and 70%, respectively). Deletion and genomic instability at FRA3B and other fragile sites could thus be a biomarker of genetic damage in BE patients and a potential biomarker of cancer risk. PMID:20647332

  7. Geophysical prospection on an Early Iron Age Cult Site near Frankfurt/Oder, Germany

    NASA Astrophysics Data System (ADS)

    Ullrich, Burkart; Kaufmann, Georg; Beilke-Voigt, Ines

    2010-05-01

    The Free University of Berlin and the Humboldt University of Berlin hosts the excellence cluster 264 Topoi, "The Formation and Transformation of Space and Knowledge in Ancient Civilizations". The Excellence Cluster pursues the goal of researching the interdependence of space and knowledge in the civilizations of the Ancient Near East, the Mediterranean, and Black Sea region and parts of the Eurasian steppe from the 6th millennium BC to around AD 500. Within this excellence cluster, the project A-I-11 "Lossow near Frankfurt/Oder - An Early Iron Age Cult Site of the Ancient Peripheral Zone" examines the evolution of an important cult site in Central Europe. The castle mound of Lossow was built as a fortified settlement in the late Bronze Age (10th century B.C.). After a phase of around 200 years, a supra-regionally significant, early Iron Age cult centre developed on this site (8th-6th century B.C.). Several pieces of evidence indicate that the locality had a central-site character. Typical for the site are well-shapes shafts, filled with large amounts of human and animal bones. The shafts with a diameter of about 1 meter and a depth of about 5 to 7 meters are a great challenge to near surface geophysics. Here, geophysical methods (geomagnetic gradiometry, geoelectric imaging, georadar survey) have been used to obtain a large-scale conclusive picture of the sub-surface both within the castle mount and around the perimeter. While the magnetic results reveal numerous archaeological artefacts, geoelectric imaging decipers the subsurface structure of the site.

  8. Reconstructing Past Vegetation Types During the Late Holocene Using Stable Carbon Isotopes of Leporids from Archaeological Sites in the American Southwest

    NASA Astrophysics Data System (ADS)

    Mauldin, R. P.; Munoz, C.; Kemp, L.; Hard, R.

    2012-12-01

    Stable carbon isotopes (δ13C) from bone collagen in leporids provide high-resolution vegetation reconstruction. Leporids [e.g., cottontails (Sylvilagus sp.), jackrabbits (Lepus sp.)] die young (ca. 2 years) and use small home ranges (< 1 km2). They consume a variety of vegetation, including plants that use both C3 and C4/CAM photosynthetic pathways. Leporids appear to focus on new growth as it becomes available throughout the year, perhaps as a function of water content. Their diet, and their bone collagen, provides a high-resolution view of the carbon isotopic values present in their local plant community. Here we provide an example of the use of leporid bone collagen for reconstruction of past vegetation types using data from several archaeological sites as well as modern collections. All samples are from a basin and range setting within the Chihuahuan Desert in far west Texas and southern New Mexico, USA. The sites span a period back to roughly 1350 BP. Isotopic patterns in leporid collagen show clear evidence of change in vegetation from around 775 BP to the modern period, with a dramatic shift of 4.2‰ in median δ13C values over this period in jackrabbit collagen and a 7.3‰ decrease in median carbon isotopic values in cottontail rabbits. These data suggest a significant increase in C3 plants in leporid diet, and by extension a relative increase in these plant types in the local environment sampled by leporids. This shift is consistent with historic accounts of more C3 mesquite, possibly because of historic land use and ranching practices in the 1800s. However, while this shift may have been accelerated by historic land use changes, our data suggest that the vegetation shift began several hundred years earlier during the prehistoric period. The prehistoric collagen isotopic record also shows increased sample variability through time in both species, suggesting that year-to-year variability in vegetation may have increased late in that sequence. Our results

  9. 10 CFR 2.603 - Acceptance and docketing of application for early review of site suitability issues in a...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... of site suitability issues in a construction permit proceeding. 2.603 Section 2.603 Energy NUCLEAR... Partial Decisions on Site Suitability Issues in Connection With an Application for a Construction Permit... Authorizations Early Partial Decisions on Site Suitability-Construction Permit § 2.603 Acceptance and...

  10. 10 CFR 2.621 - Acceptance and docketing of application for early review of site suitability issues in a combined...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Authorizations Early Partial Decisions on Site Suitability-Combined License Under 10 Cfr Part 52 § 2.621... of site suitability issues in a combined license proceeding. 2.621 Section 2.621 Energy NUCLEAR... Partial Decisions on Site Suitability Issues in Connection With an Application for a Construction...

  11. 10 CFR 2.603 - Acceptance and docketing of application for early review of site suitability issues in a...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... of site suitability issues in a construction permit proceeding. 2.603 Section 2.603 Energy NUCLEAR... Partial Decisions on Site Suitability Issues in Connection With an Application for a Construction Permit... Authorizations Early Partial Decisions on Site Suitability-Construction Permit § 2.603 Acceptance and...

  12. 10 CFR 2.621 - Acceptance and docketing of application for early review of site suitability issues in a combined...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Authorizations Early Partial Decisions on Site Suitability-Combined License Under 10 Cfr Part 52 § 2.621... of site suitability issues in a combined license proceeding. 2.621 Section 2.621 Energy NUCLEAR... Partial Decisions on Site Suitability Issues in Connection With an Application for a Construction...

  13. Forces of environmental flux in Central America during the holocene

    SciTech Connect

    Leyden, B. )

    1994-06-01

    A review of palynological and limnological data from Central America serves as a framework for evaluating environmental stability during the Holocene. The magnitude of climatic forcing after the early Holocene has not produced the dramatic changes that spanned the transition to post-glacial conditions. Nevertheless, climatic variability and human disturbance have had a significant impact on the vegetation of the region. This discussion has relevance for broader questions of species diversity and the long-term stability of vegetation associations in the tropics.

  14. The Actomyosin Ring Recruits Early Secretory Compartments to the Division Site in Fission Yeast

    PubMed Central

    Vjestica, Aleksandar; Tang, Xin-Zi

    2008-01-01

    The ultimate goal of cytokinesis is to establish a membrane barrier between daughter cells. The fission yeast Schizosaccharomyces pombe utilizes an actomyosin-based division ring that is thought to provide physical force for the plasma membrane invagination. Ring constriction occurs concomitantly with the assembly of a division septum that is eventually cleaved. Membrane trafficking events such as targeting of secretory vesicles to the division site require a functional actomyosin ring suggesting that it serves as a spatial landmark. However, the extent of polarization of the secretion apparatus to the division site is presently unknown. We performed a survey of dynamics of several fluorophore-tagged proteins that served as markers for various compartments of the secretory pathway. These included markers for the endoplasmic reticulum, the COPII sites, and the early and late Golgi. The secretion machinery exhibited a marked polarization to the division site. Specifically, we observed an enrichment of the transitional endoplasmic reticulum (tER) accompanied by Golgi cisternae biogenesis. These processes required actomyosin ring assembly and the function of the EFC-domain protein Cdc15p. Cdc15p overexpression was sufficient to induce tER polarization in interphase. Thus, fission yeast polarizes its entire secretory machinery to the cell division site by utilizing molecular cues provided by the actomyosin ring. PMID:18184749

  15. A P-wave based, on-site method for Earthquake Early Warning

    NASA Astrophysics Data System (ADS)

    Zollo, Aldo

    2016-04-01

    Can we rapidly predict the potential damage of earthquakes by-passing the estimation of its location and magnitude? One possible approach is to predict the expected peak ground shaking at the site and the earthquake magnitude from the initial P-peak amplitude and characteristic period, respectively. The idea, first developed by Wu and Kanamori (2005), is to combine the two parameters for declaring the alert once the real-time measured quantities have passed pre-defined thresholds. Our proposed on-site early warning method generalized this approach, based on the analysis of strong motion data from modern accelerograph networks in Japan, Taiwan and Italy (Zollo et al., 2010). It is based on the real-time measurement of the period (τc) and peak displacement (Pd) parameters at one or more co-located stations at a given target site to be protected against the earthquake effects. By converting these real-time proxies in predicted values of Peak Ground Velocity (PGV) or instrumental intensity (IMM) and magnitude, an alert level is issued at the recording site based on a decisional table with four entries defined upon threshold values of the parameters Pd and Tc. The latter ones are set according to the error bounds estimated on the derived prediction equations. A near-source network of stations running the onsite method can provide the event location and transmit the information about the alert levels recorded at near-source stations to more distant sites, before the arrival of the most destructive phase. The network-based approach allows for the rapid and robust estimation of the Potential Damage Zone (PDZ), that is the area where most of earthquake damage is expected (Colombelli et al., 2012). A new strategy for a P-wave based, on-site earthquake early warning system has been developed and tested on Japanese strong motion data and under testing on Italian data. The key elements are the real-time, continuous measurement of three peak amplitude parameters and their

  16. Preferential sites of early DNA cleavage in apoptosis and the pathway of nuclear damage.

    PubMed

    Krystosek, A

    1999-04-01

    We have tested the specific hypothesis that the pathway of nuclear collapse in apoptosis is governed by the early attack on active chromatin at spatially restricted nuclear sites. Cell death in PC12 pheochromocytoma cells deprived of serum growth factors, in HL-60 leukemic cells treated with inhibitors of protein or RNA biosynthesis, and in U937 histiocytic lymphoma cells exposed to the cytokine tumor necrosis factor alpha showed a common mechanism in the targeting of DNA for degradation. An incorporation assay with labeled nucleotide revealed an early selective nicking in peripheral nuclear chromatin with concomitant diminution in the amount of immunoreactive lamin B protein. This was followed by a phase of more extensive cleavages, continued nuclear protein loss, chromatin collapse, and fragmentation of nuclei. The spatial restriction of early cleavages is similar to the nicking obtained by the application of exogenous DNase I to fixed nuclei of normal cells and to that obtained in the activation of the endogenous endonuclease of liver nuclei by Ca2+. These similarities suggest that, in apoptosis, activation of an endonuclease preferentially recognizing a specific chromatin configuration, such as that of active (DNase I-sensitive) genes, underlies the early spatial demarcation of cleavages. PMID:10219626

  17. Towards a Circum-Antarctic Holocene Paleointensity Record

    NASA Astrophysics Data System (ADS)

    Brachfeld, S.; Kissel, C.; Laj, C.; Willmott, V.

    2005-12-01

    New Holocene geomagnetic paleointensity records have been constructed from the Western Antarctic Peninsula (WAP), Eastern Antarctic Peninsula (EAP), and from the East Antarctic Margin (EAM). The goal of this work is to develop Antarctic paleointensity reference curves for correlation and dating of Antarctic continental shelf sediments. Sediment sequences deposited in fjords and inner shelf basins contain Holocene sections of 3-meters to more than 20-meters, recording the last deglaciation, the paleohistory of ice shelves, and shifting paleoceanographic conditions. However, these records suffer from a lack biogenic calcite for radiocarbon dating. Diatomaceous mud contains sufficient acid insoluble organic matter (aiom) for radiocarbon dating and hence an independent chronology. However, laminated oozes yield shallow inclinations, hence the remanence vector is suspect. Bioturbated diatomaceous mud and diatom-poor muds yield excellent directional records and satisfy the criteria for magnetic uniformity, however the organic content is low and aiom dates can be problematic. Our paleointensity records show the broad pattern of higher intensity during the late Holocene, and lower intensity during the early to middle Holocene, similar to the sinusoidal intensity pattern seen in global absolute and relative paleointensity stacks. Several of the records contain 3 to 4 late Holocene peaks with 1000-year wavelengths that are similar in amplitude and duration to features seen in northern hemisphere lacustrine and marine records. Here we evaluate the local versus regional character of the Antarctic paleointensity records, and the consistency of aiom-dated versus paleointensity-tuned chronologies.

  18. Holocene variations in peatland methane cycling associated with the Asian summer monsoon system

    PubMed Central

    Zheng, Yanhong; Singarayer, Joy S.; Cheng, Peng; Yu, Xuefeng; Liu, Zhao; Valdes, Paul J.; Pancost, Richard D.

    2014-01-01

    Atmospheric methane concentrations decreased during the early to middle Holocene; however, the governing mechanisms remain controversial. Although it has been suggested that the mid-Holocene minimum methane emissions are associated with hydrological change, direct evidence is lacking. Here we report a new independent approach, linking hydrological change in peat sediments from the Tibetan Plateau to changes in archaeal diether concentrations and diploptene δ13C values as tracers for methanogenesis and methanotrophy, respectively. A minimum in inferred methanogenesis occurred during the mid-Holocene, which, locally, corresponds with the driest conditions of the Holocene, reflecting a minimum in Asian monsoon precipitation. The close coupling between precipitation and methanogenesis is validated by climate simulations, which also suggest a regionally widespread impact. Importantly, the minimum in methanogenesis is associated with a maximum in methanotrophy. Therefore, methane emissions in the Tibetan Plateau region were apparently lower during the mid-Holocene and partially controlled by interactions of large-scale atmospheric circulation. PMID:25135106

  19. Vegetation changes and timberline fluctuations in the Central Alps as indicators of holocene climatic oscillations

    SciTech Connect

    Wick, L.; Tinner, W.

    1997-11-01

    Pollen and plant-macrofossil data are presented for two lakes near the timberline in the Italian (Lago Basso, 2250 m) and Swiss Central Alps (Gouille Rion, 2343 m). The reforestation at both sites started at 9700-9500 BP with Pinus cembra, Larix decidua, and Betula. The timberline reached its highest elevation between 8700 and 5000 BP and retreated after 5000 BP, due to a mid-Holocene climatic change and increasing human impact since about 3500 BP (Bronze Age). The expansion of Picea abies at Lago Basso between ca. 7500 and 6200 BP was probably favored by cold phases accompanied by increased oceanicity, whereas in the area of Gouille Rion, where spruce expanded rather late (between 4500 and 3500 BP), human influence equality might have been important. The mass expansion of Alnus viridis between ca. 5000 and 3500 BP probably can be related to both climatic change and human activity at timberline. During the early and middle Holocene a series of timberline fluctuations is recorded as declines in pollen and macrofossil concentrations of the major tree species, and as increases in nonarboreal pollen in the pollen percentage diagram of Gouille Rion. Most of the periods of low timberline can be correlated by radiocarbon dating the climatic changes in the Alps as indicated by glacier advances in combination with palynological records, solifluction, and dendroclimatical data. Lago Basso and Gouille Rion are the only sites in the Alps showing complete palaeobotanical records of cold phases between 10,000 and 2000 BP with very good time control. The altitudinal range of the Holocene treeline fluctuations caused by climate most likely was not more than 100 to 150 m. A possible correlation of a cold period at ca. 7500-6500 BP (Misox oscillation) in the Alps is made with paleoecological data from North American and Scandinavia and a climate signal in the GRIP ice core from central Greenland 8200 yr ago (ca. 7400 yr uncal. BP).

  20. Palaeoenvironment and Holocene land use of Djara, Western Desert of Egypt

    NASA Astrophysics Data System (ADS)

    Kindermann, Karin; Bubenzer, Olaf; Nussbaum, Stefanie; Riemer, Heiko; Darius, Frank; Pöllath, Nadja; Smettan, Ursula

    2006-07-01

    The results of the interdisciplinary project ACACIA support the assumption of a more humid climate at Djara, on the Egyptian Limestone Plateau, which is a hyper-arid desert today, during the early and mid-Holocene. The ancient plant and animal inventories give new impetus for the suggestion of an interfingering of two climatic regimes, the winter rains from the north and west and the summer monsoonal rains from the south, on the latitude of Djara. A playa sediment sequence, the composition of plant and animal taxa as well as the reconstructed settlement patterns indicate a semi-arid climate with alternating more humid and drier conditions. The concentration of prehistoric sites in the Djara depression points to locally favourable conditions in contrast to the surrounding plateau surface. The widespread catchment and a distinct system of palaeochannels offered fresh water over a period of time due to the run-off from the plateau surface after rain events. Although the ecological conditions were better during the Holocene humid phase than they are today, a sedentary way of life was improbable. The hydrological constraints require altogether highly mobile subsistence strategies. Shells of the Nile bivalve Aspatharia sp. ( Spathopsis sp.) give evidence for contacts between Djara and the Nile Valley, which remains beside the Egyptian oases an important retreat area with perennially available water. The decrease of radiocarbon dates and related archaeological sites around 6300 BP (c. 5300 cal BC) indicate the depopulation of the Djara region as a consequence of the drying trend. While the drop off of the 14C-dates can also be observed in other desert research areas of the ACACIA-project, we date the end of the Holocene humid phase about 300 years earlier than previously suggested.

  1. Mid to late Holocene oceanographic changes offshore Adélie Land, Antarctica: Ultra-high resolution foraminiferal assemblage and isotopic records from IODP Expedition 318 Site U1357

    NASA Astrophysics Data System (ADS)

    Hendricks, E.; Salman, F. I.; Pekar, S. F.; Dunbar, R. B.; DeCesare, M.

    2014-12-01

    Foraminiferal biofacies as well as δ18O and δ13C records from IODP Site U1357 reveal significant changes in deep and surface water properties that include temperature, ventilation, and productivity during the mid to late Holocene. Site U1357 is located in the Adélie Trough, a glacially scoured valley on the continental shelf ~50km off the coast of East Antarctica. Sediment samples were taken at 10cm intervals resulting in an approximate time step for each sample of 7yr resolution based on extensive C14 dating and visible band counting exercises. As part of a collaborative effort between Queens College and Stanford University, samples from the upper part of the core were used in this study, which spanned from near Recent to 6kyr BP. Neogloboquadrina pachyderma make up nearly 50% of all foraminifers counted and was used to construct pelagic stable isotope records. From nearly 10,000 foraminifers counted, ~34 foraminiferal species were identified. The highest δ18O values occur from ~3.0 to ~6.1kyr and ~1kyr to Recent, with the lowest occurring from ~1.4 to ~3.8kyr. The highest δ13C values occur when δ18O are low. Total benthic foraminiferal abundances are highest during two intervals: Recent to ~1.4kyr and ~3.6 to ~6.1kyr. For ~2 to ~3.6kyr, the agglutinated species are the most dominant with calcareous benthic foraminifers being mainly absent. The higher δ18O values observed are consistent with lower surface water temperatures and decreased melt water from icebergs, with lower δ18O values ascribed to increased melt waters and possibly higher surface water temperatures. Previous studies indicate that cooler waters occurred when we observe lower foraminiferal δ18O values. This suggests that the N. pachyderma δ18O record was influenced primarily by the δ18O of seawater (e.g., iceberg melt waters), with temperature being a minor control. Higher δ13C values are associated with lower δ18O, which implies increased water column stratification coupled with high

  2. Holocene Evolution of Qing'ao Embayment, Southern China

    NASA Astrophysics Data System (ADS)

    Switzer, A. D.; Yu, F.; Chen, B.; Zheng, Z.; Wang, D.

    2012-12-01

    The Holocene evolution of the Qing'ao embayment, Nan'ao Island, southern China, is primarily the result of the interaction of tectonic activity, climate variation and changes in relative sea level. Characterizing the evolutionary history of the relatively small Qing'ao embayment during the Holocene will help improve our understanding of the driving mechanisms of coastal evolution in the area. To reconstruct the Holocene evolution history we analyzed the grain size, loss on ignition (LOI) and carbonate content of modern and core samples. Modern environmental analogs were examined in surface samples ranging from the coastal sand dunes through to offshore. The results of these modern samples suggest that dune sand (mean size of ~2.33Phi) are slightly finer than beach sand (mean size of 2.13Phi), and nearshore sediment is much coarser than offshore sediment (mean size of 5.90Phi). This modern analogs were then applied to 8 percussion cores from the Qing'ao embayment. A chronological framework obtained from 11 radiocarbon samples suggests that the embayment started to accept deposition since early Holocene, ~8500 cal. yr. BP. Three main phases of Holocene evolution were identified. A basin wide shell-rich sand sheet forms the basal Holocene facies and overlies clay rich presumably Pleistocene sediments or bedrock. This facies records an initial sedimentation phase associated with the early Holocene transgression into the embayment (~8500-6000 cal. yr. BP). The basal facies grades upward to a mixed sandy-mud facies which includes lagoonal clayey-silts, flood tide delta sands and records an estuarine phase lasting from ~6000-1000 cal. yr. BP that appears coincident with falling regional sea levels. Coincident with the estuarine phase is a period of coastal dune building recorded as yet undated massive sands that are found in the upper fill. Toward the end of the estuarine phase it is apparent that dune migration has restricted the lagoon entrance and that this was

  3. Palaeotectonic implications of increased late Eocene-early Oligocene volcanism from South Pacific DSDP sites

    USGS Publications Warehouse

    Kennett, J.P.; Von Der Borch, C.; Baker, P.A.; Barton, C.E.; Boersma, A.; Cauler, J.P.; Dudley, W.C., Jr.; Gardner, J.V.; Jenkins, D.G.; Lohman, W.H.; Martini, E.; Merrill, R.B.; Morin, R.; Nelson, Campbell S.; Robert, C.; Srinivasan, M.S.; Stein, R.; Takeuchi, A.; Murphy, M.G.

    1985-01-01

    Late Eocene-early Oligocene (42-35 Myr) sediments cored at two DSDP sites in the south-west Pacific contain evidence of a pronounced increase in local volcanic activity, particularly in close association with the Eocene-Oligocene boundary. This pulse of volcanism is coeval with that in New Zealand and resulted from the development of an Indo- Australian / Pacific Plate boundary through the region during the late Eocene. The late Eocene / earliest Oligocene was marked by widespread volcanism and tectonism throughout the Pacific and elsewhere, and by one of the most important episodes of Cenozoic climatic cooling. ?? 1985 Nature Publishing Group.

  4. Brief communication: Gladysvale: first early hominid site discovered in South Africa since 1948.

    PubMed

    Berger, L R; Keyser, A W; Tobias, P V

    1993-09-01

    We report here the discovery of fossil hominid teeth at Gladysvale, near Johannesburg in the southern Transvaal. This find makes the site the seventh in South Africa to yield australopithecine remains and the first new early hominid-bearing locality to be found in this region since 1948. Apart from the hominid specimens, our excavations at Gladysvale have added appreciably to the abundant Plio-Pleistocene fauna previously recorded from the cave deposit. The fauna indicates that savanna conditions prevailed during deposition of at least part of the fill. Preliminary faunal dating gives an age of deposition of between c1.7 and c2.5 mya. PMID:8238287

  5. Climate change and human occupation in the Southern Arabian lowlands during the last deglaciation and the Holocene

    NASA Astrophysics Data System (ADS)

    Lézine, Anne-Marie; Robert, Christian; Cleuziou, Serge; Inizan, Marie-Louise; Braemer, Frank; Saliège, Jean-François; Sylvestre, Florence; Tiercelin, Jean-Jacques; Crassard, Rémy; Méry, Sophie; Charpentier, Vincent; Steimer-Herbet, Tara

    2010-07-01

    Paleohydrological and archaeological evidence from the Southern and South-Eastern Arabian Peninsula reveal strong relations between phases of human settlements and climate change linked to the Indian monsoon system. During the early to mid-Holocene, large fresh-water lakes extended in the lowland deserts of Ramlat as-Sab'atayn (Yemen) and Wahiba Sands (Oman), which were very similar to those occurring in the North, in the Rub' al-Khali (Saudi Arabia), at that time. Many archaeological sites, characterized by scattered stone artefacts, ostrich-eggshells and bones around hearths, are related to this lacustrine phase, which culminated around 10 000-8000 cal yr B.P. in the lowland deserts before the lakes progressively dried up. The last record of fresh-water bodies' extensions date back 7300 cal yr B.P. at Shabwa (Yemen) and 7500 cal yr B.P. at al-Haid (Oman). Then, fresh-water was probably available only from seasonal run-off from adjacent highlands, where paleolakes persisted into the late Holocene. Dry climate conditions in the inland desert of Yemen during the late Holocene coincide with a phase of intensive human inhabitation as testified by development of irrigation in the piedmontane areas, numerous necropolises of built collective burials and houses.

  6. Holocene fire history in Western China - relationships with climate and human impact, and the role of fire in vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Cui, Q.

    2015-12-01

    It is well recognised that studies of past fire regimes and their causes (human and/or climatic) are useful to understand the long-term ecological effects of fire on vegetation communities. Further, information on the long-term fire history and its effect on vegetation dynamics may provide useful insights for vegetation management in fragile eco-environment of Western China. The main aim of this study is to quantitatively reconstruct high-resolution fire history in West China based on charcoal records from peatlands in Zoige basin (Tibet) and Altai Mountains (Xinjiang). We investigate the long-term relationships between fire, climate, human-impact and the history of biodiversity based on four Holocene macro- and micro- charcoal records and a synthesis on previously published pollen data and geochemistry data. Three hypotheses based on global charcoal records and former studies on palaeofire carried out in China need to be test by this study: 1) during early-mid Holocene period, fire frequency in the study area is relative low and best explained by the changes of regional climate; 2) during the late Holocene, fire activities in the study area increased might due to impacts of the human activities over the climate changes, and human activities is responsible for the temporal and spatial variations in fire regime; 3) the difference of fire histories can be explained by the difference of vegetation composition at site.

  7. Parasitic diversity found in coprolites of camelids during the Holocene.

    PubMed

    Taglioretti, Verónica; Fugassa, Martín Horacio; Sardella, Norma Haydée

    2015-07-01

    Knowledge of parasitic infections to which fauna was exposed in the past provides information on the geographical origin of some parasites, on the possible dispersal routes and for archaeological fauna on the potential zoonotic risk that human and animal populations could be exposed. The aim of the present study was to examine the gastrointestinal parasite present in camelid coprolites collected from the archaeological site Cerro Casa de Piedra, cave 7 (CCP7), Patagonia, Argentina. Coprolites were collected from different stratified sequences dating from the Pleistocene-Holocene transition to the late Holocene. Paleoparasitological examination revealed the presence of eggs of Trichostrongylidae attributed to Lamanema chavezi or Nematodirus lamae, eggs of three unidentified capillariids, Strongylus-type eggs and oocysts of Eimeria macusaniensis. These parasites affected camelids living in the studied area since the Pleistocene-Holocene transition, about 10,000 years ago. Gastrointestinal parasite fauna of patagonian camelids did not vary significatively from Pleistocene-Holocene transition to late Holocene, although environmental conditions fluctuated greatly throughout this period, as indicative of the strength and the stability of these associations over time. In this study, the zoonotic and biogeography importance of parasites of camelids are also discussed. PMID:25859925

  8. Takarkori rock shelter (SW Libya): an archive of Holocene climate and environmental changes in the central Sahara

    NASA Astrophysics Data System (ADS)

    Cremaschi, Mauro; Zerboni, Andrea; Mercuri, Anna Maria; Olmi, Linda; Biagetti, Stefano; di Lernia, Savino

    2014-10-01

    Rock shelters in the central Saharan massifs preserve anthropogenic stratigraphic sequences that represent both a precious archive for the prehistory of the region and a powerful proxy data for Holocene palaeoenvironments. The geoarchaeological (micromorphology) and archaeobotanical (pollen analysis) approaches were integrated to investigate the anthropogenic sedimentary sequence preserved within the Takarkori rock shelter, a Holocene archaeological site located in the Libyan central Sahara (southern Tadrart Acacus massif). The site was occupied throughout the Early and Middle Holocene (African Humid Period) by groups of hunter-gatherers before and by pastoral communities later. The investigation on the inner part of the sequence allows to recognize the anthropogenic contribution to sedimentation process, and to reconstruct the major changes in the Holocene climate. At the bottom of the stratigraphic sequence, evidence for the earliest frequentation of the site by hunters and gatherers has been recognized; it is dated to c. 10,170 cal yr BP and is characterized by high availability of water, freshwater habitats and sparsely wooded savannah vegetation. A second Early Holocene occupation ended at c. 8180 cal yr BP; this phase is marked by increased aridity: sediments progressively richer in organics, testifying to a more intense occupation of the site, and pollen spectra indicating a decrease of grassland and the spreading of cattails, which followed a general lowering of lake level or widening of shallow-water marginal habitats near the site. After this period, a new occupational phase is dated between c. 8180 and 5610 cal yr BP; this period saw the beginning of the frequentation of pastoral groups and is marked by an important change in the forming processes of the sequence. Sediments and pollen spectra confirm a new increase in water availability, which led to a change in the landscape surrounding the Takarkori rock shelter with the spreading of water bodies. The

  9. Holocene Charcoal Deposition From Brazilian Forest Fires

    NASA Astrophysics Data System (ADS)

    Turcq, B.; Cordeiro, R. C.; Albuquerque, A. S.; Simoes, F. L.; Sifeddine, A.

    2004-12-01

    Determination of charcoal accumulation rate in lacustrine sediments allows to reconstruct the fire history of the region surrounding the lake. Our studies have been achieved in three Amazonian sites and one site in Atlantic rainforest. Charcoal fragments are identified and counted under a microscope. Typical size of these charcoals is around ten micrometers and they probably have been subject to eolian transport. The highest charcoal accumulation rates were obtained in sediments from Middle Holocene in Carajás region, eastern Amazonia. These rates are on the same order than the present day charcoal accumulation rate in Alta Floresta, a region of Amazonia which is being submited to intense slash and burn. The lowest values were found in Lagoa da Pata in Sao Gabriel da Cachoeira, a very humid area in western Amazon. We observed from the D. Helvécio record, in the Atlantic rainforest, fire occurrences from 8,400 to 6,400 cal years BP. For Carajás lake, surrounded by tropical rain forest, we had identified fires during the period between 8,000 and 5,300 cal years BP. Finally, the lake Caracarana, which is surrounded by grass savanna, showed a record of main fire occurrence phase at 9,750 cal yrs BP and a second phase marked by charcoal peaks at 7,680, 6,990 and 6,460 cal yrs BP. The synchronism of the fire occurrence periods in different Brazilian regions is related to the Middle Holocene dry climate phase provoked by the low summer insolation. Differences in the accumulation rates can be attributed to differences in biomass availability and fire return time. The carbon released in the atmosphere by this fires must have contributed to the observed increase of CO2, poorer in 13C, during the middle Holocene.

  10. Holocene temperature records from the East China sea mud area southwest of the Cheju Island reconstructed by the U{37/K'} and TEX86 paleothermometers

    NASA Astrophysics Data System (ADS)

    Xing, Lei; Jiang, Yiqing; Yuan, Zineng; Zhang, Hailong; Li, Li; Zhou, Liping; Zhao, Meixun

    2013-12-01

    As an important marginal sea under the influences of both the Changjiang River and the Kuroshio, the East China Sea (ECS) environment is sensitive to both continental and oceanic forcing. Paleoenvironmental records are essential for understanding the long-term environmental evolution of the ECS and adjacent areas. However, paleo-temperature records from the ECS shelf are currently very limited. In this study, the U{37/K'} and TEX86 paleothermometers were used to reconstruct surface and subsurface temperature changes of the mud area southwest of the Cheju Island (Site F10B) in the ECS during the Holocene. The results indicate that temperature changes of F10B during the early Holocene (11.6-6.2 kyr) are associated with global climate change. During the period of 6.2-2.5 kyr, the similar variability trends of smoothing average of ΔT (the difference between surface and subsurface temperature) of Site F10B and the strength of the Kuroshio suggest that the Kuroshio influence on the site started around 6.2 kyr when the Kuroshio entered the Yellow Sea and continued to 2.5 kyr. During the late Holocene (2.5-1.45 kyr), apparent decreases of U{37/K'} sea surface temperature (SST) and ΔT imply that the direct influence of the Kuroshio was reduced while cold eddy induced by the Kuroshio gradually controlled hydrological conditions of this region around 2.5 kyr.

  11. Origin and dynamics of the northern South American coastal savanna belt during the Holocene - the role of climate, sea-level, fire and humans

    NASA Astrophysics Data System (ADS)

    Alizadeh, Kamaleddin; Cohen, Marcelo; Behling, Hermann

    2015-08-01

    Presence of a coastal savanna belt expanding from British Guiana to northeastern Brazil cannot be explained by present-day climate. Using pollen and charcoal analyses on an 11.6 k old sediment core from a coastal depression in the savanna belt near the mouth of the Amazon River we investigated the paleoenvironmental history to shed light on this question. Results indicate that small areas of savanna accompanied by a forest type composed primarily by the genus Micropholis (Sapotaceae) that has no modern analog existed at the beginning of the Holocene. After 11,200 cal yr BP, savanna accompanied by few trees replaced the forest. In depressions swamp forest developed and by ca 10,000 cal yr BP replaced by Mauritia swamps. Between 8500 and 5600 cal yr BP gallery forest (composed mainly of Euphorbiaceae) and swamp forest succeeded the treeless savanna. The modern vegetation with alternating gallery forest and savanna developed after 5600 cal yr BP. We suggest that the early Holocene no-analog forest is a relict of previously more extensive forest under cooler and moister Lateglacial conditions. The early Holocene savanna expansion indicates a drier phase probably related to the shift of the Intertropical Convergence Zone (ITCZ) towards its northernmost position. The mid-Holocene forest expansion is probably a result of the combined influence of equatorwards shift of ITCZ joining the South Atlantic Convergence Zone (SACZ). The ecosystem variability during the last 5600 cal yr BP, formed perhaps under influence of intensified ENSO condition. High charcoal concentrations, especially during the early Holocene, indicate that natural and/or anthropogenic fires may have maintained the savanna. However, our results propose that climate change is the main driving factor for the formation of the coastal savanna in this region. Our results also show that the early Holocene sea level rise established mangroves near the study site until 7500 cal yr BP and promoted

  12. Anthropogenic and geomorphic controls on peatland dynamics in contrasting floodplain environments during the Holocene and its impact on carbon storage

    NASA Astrophysics Data System (ADS)

    Verstraeten, Gert; Broothaerts, Nils; Notebaert, Bastiaan

    2016-04-01

    Peatlands are an important store of carbon in terrestrial environments, and scientific interest in peatlands has increased strongly in the light of the recent global climatic changes. Much attention has been paid to peatland dynamics in extensive arctic and boreal wetlands or to blanket peat in temperate regions. Nevertheless, long-term dynamics of peat in alluvial wetlands in temperate regions remains largely underresearched. In this study, data from three contrasting environments were used to provide more insights in the anthropogenic and geomorphic controls on peatland dynamics. The results show a high variability in alluvial peatland dynamics between the different study sites. In the central Belgian Loess Belt, alluvial peatlands developed during the early Holocene but gradually disappeared from the Mid-Holocene onwards due to the gradual intensification of agricultural activities in the catchment and consequent higher sedimentation rates in the floodplain system. The end of peat growth is shown to be diachronous at catchment scale, ranging between 6500 and 500 cal a BP. The disappearance of the alluvial peatlands has important implications since it potentially reduces the storage of locally produced C. Nevertheless, it was shown that this reduced production of local C but was outbalanced by the burial of hillslope derived C. Also within the sandy catchments of the Belgian Campine region alluvial peatlands initiated in the early Holocene but, here, they abruptly disappeared in the Mid-Holocene before the onset of intense agricultural activities in the catchment. This suggests that for the sandy regions, anthropogenic impact on peatland dynamics is less important compared to natural factors. For these regions, the disappearance of alluvial peatland formation resulted in a sharp decline in alluvial carbon storage as there is no compensation through hillslope derived C input. For the upper Dee catchment in NE Scotland, Holocene carbon floodplain storage varies

  13. An Early Pleistocene high-resolution paleoclimate reconstruction from the West Turkana (Kenya) HSPDP drill site

    NASA Astrophysics Data System (ADS)

    Stockhecke, Mona; Beck, Catherine; Brown, Erik T.; Cohen, Andrew; Deocampo, Daniel M.; Feibel, Craig S.; Pelletier, Jon D.; Rabideaux, Nathane M.; Sier, Mark

    2016-04-01

    The Hominin Sites and Paleolakes Drilling Project (HSPDP), and the related Olorgesailie Drilling Project (ODP), recovered ~2 km of drill core since 2012. At the HSPDP West Turkana Kaitio (WTK) site a 216 m-long core that covers the Early Pleistocene time window (1.3 to 1.87 Ma) during which hominids first expanded out of Africa and marine records document reorganization of tropical climate and the development of the strong Walker circulation. WTK carries particular interest for paleoclimate and paleoenvironmental reconstructions as it is located only 2.5 km from the location of one of the most complete hominin skeletons ever recovered (Nariokotome Boy). XRF core scanning data provide a means of evaluating records of past environmental conditions continuously and at high resolution. However, the record contains complex lithologies reflecting repeated episodes of inundation and desiccation along a dynamic lake margin. Here we present a methodological approach to address the highly variable lithostratigraphy of the East African records to establish comprehensive paleoclimate timeseries. The power spectrum of the presented hydroclimate record peaks at Milankovitch cycles, qualifying HSPDP drill cores from the Turkana Basin to be used as high-resolution Early Pleistocene paleoclimate archive. Comparing these data with marine climate reconstructions sheds light into athmospheric processes and continental climate dynamics.

  14. 10 CFR 2.603 - Acceptance and docketing of application for early review of site suitability issues in a...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Acceptance and docketing of application for early review of site suitability issues in a construction permit proceeding. 2.603 Section 2.603 Energy NUCLEAR REGULATORY COMMISSION RULES OF PRACTICE FOR DOMESTIC LICENSING PROCEEDINGS AND ISSUANCE OF ORDERS Additional Procedures Applicable to Early...

  15. 10 CFR 2.621 - Acceptance and docketing of application for early review of site suitability issues in a combined...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Acceptance and docketing of application for early review of site suitability issues in a combined license proceeding. 2.621 Section 2.621 Energy NUCLEAR REGULATORY COMMISSION RULES OF PRACTICE FOR DOMESTIC LICENSING PROCEEDINGS AND ISSUANCE OF ORDERS Additional Procedures Applicable to Early...

  16. Report on Lessons Learned from the NP 2010 Early Site Permit Program FINAL REPORT

    SciTech Connect

    2008-03-26

    This report provides a summary of lessons learned from the demonstration of the licensing process for three Early Site Permit (ESP) applications supported as part of the Department of Energy’s (DOE) Nuclear Power 2010 (NP 2010) program. The ESP process was established by the Nuclear Regulatory Commission (NRC) to enable completion of the site evaluation component of nuclear power plant licensing under 10 CFR Part 52 before a utility makes a decision to build a plant. Early Site Permits are valid for 10 to 20 years and can be renewed for an additional 10 to 20 years. NRC review of an ESP application addresses site safety issues, environmental protection issues, and plans for coping with emergencies. Successful completion of the ESP process will establish that a site is suitable for possible future construction and operation of a nuclear power plant. Most importantly, an ESP resolves significant site-related safety and environmental issues early in the decision process and helps achieve acceptance by the public. DOE competitively selected Dominion Nuclear Energy North Anna, LLC (Dominion); System Energy Resources, Inc. (an Entergy subsidiary); and Exelon Generation Company, LLC (Exelon) in 2002 to demonstrate the ESP process and provided cost-shared support through the NP 2010 program. Dominion pursued an ESP for the North Anna site in Virginia; System Energy Resources, Inc. pursued an ESP for the Grand Gulf site in Mississippi; and Exelon pursued an ESP for the Clinton site in Illinois. After successfully demonstrating the process, the NRC issued an ESP for Clinton on March 17, 2007; Grand Gulf on April 5, 2007; and North Anna on November 27, 2007. As with all successful projects, there are lessons to be learned from the NP 2010 early site permitting demonstration that can help improve future implementation guidance documents and regulatory review standards. In general, these lessons pertain to the effectiveness of the regulatory process, experience related to

  17. Early Pleistocene human humeri from the Gran Dolina-TD6 site (Sierra de Atapuerca, Spain).

    PubMed

    Bermúdez de Castro, José María; Carretero, José Miguel; García-González, Rebeca; Rodríguez-García, Laura; Martinón-Torres, María; Rosell, Jordi; Blasco, Ruth; Martín-Francés, Laura; Modesto, Mario; Carbonell, Eudald

    2012-04-01

    In this report, we present a morphometric comparative study of two Early Pleistocene humeri recovered from the TD6 level of the Gran Dolina cave site in Sierra de Atapuerca, northern Spain. ATD6-121 belongs to a child between 4 and 6 years old, whereas ATD6-148 corresponds to an adult. ATD6-148 exhibits the typical pattern of the genus Homo, but it also shows a large olecranon fossa and very thin medial and lateral pillars (also present in ATD6-121), sharing these features with European Middle Pleistocene hominins, Neandertals, and the Bodo Middle Pleistocene humerus. The morphology of the distal epiphysis, together with a few dental traits, suggests a phylogenetic relationship between the TD6 hominins and the Neandertal lineage. Given the older geochronological age of these hominins (ca. 900 ka), which is far from the age estimated by palaeogenetic studies for the population divergence of modern humans and Neandertals (ca. 400 ka), we suggest that this suite of derived "Neandertal" features appeared early in the evolution of the genus Homo. Thus, these features are not "Neandertal" apomorphies but traits which appeared in an ancestral and polymorphic population during the Early Pleistocene. PMID:22328492

  18. Rectilinear evolution in arvicoline rodents and numerical dating of Iberian Early Pleistocene sites

    NASA Astrophysics Data System (ADS)

    Palmqvist, Paul; González-Donoso, José María; De Renzi, Miquel

    2014-08-01

    Lozano-Fernández et al. (2013a) have recently published a method intended for numerical dating of Early Pleistocene sites, which is based on the assumption of uniform, constant rate increase through time of mean lower molar tooth length of water voles (Mimomys savini) in a number of levels sampled in the stratigraphic sequence of Atapuerca TD site. They suggest that the regression equation obtained in this local section for site chronology on tooth size could be useful for estimating the numerical age of other localities from southwestern Europe. However, in our opinion this biostratigraphic approach has severe conceptual and methodological problems, which discourage its use as a chronometric tool. These problems include that: (1) the logic behind their approach represents a ‘fallacy of hasty generalization', because the results obtained for a local section are generalized to all possible stratigraphic sequences; (2) the study is based on tooth measurements from a limited set of samples taken in a single locality, which are represented by small numbers of specimens, cover a short time span and have a high level of age uncertainty; (3) the samples analyzed show small, statistically non-significant differences between their mean tooth length values; (4) the approach assumes a linear-straight, orthoevolutionary model of change at constant, monotonic rate for the apparent trend to increasing tooth size in the M. savini lineage; (5) these changes are better described in the Atapuerca TD section by a random walk, or even by a series of independent events, than by a model of rectilinear change; and (6) the application of this methodology to other localities such as the Orce sites, which preserve the oldest evidence of human presence in Europe, would mean that an equation adjusted within a restricted chronological range (1.01-0.8 Ma) is used for extrapolating the ages of sites that are clearly older (˜1.4 Ma).

  19. Robotic single site versus robotic multiport hysterectomy in early endometrial cancer: a case control study

    PubMed Central

    2016-01-01

    Objective To compare surgical outcomes and cost of robotic single-site hysterectomy (RSSH) versus robotic multiport hysterectomy (RMPH) in early stage endometrial cancer. Methods This is a retrospective case-control study, comparing perioperative outcomes and costs of RSSH and RMPH in early stage endometrial cancer patients. RSSH were matched 1:2 according to age, body mass index, comorbidity, the International Federation of Gynecology and Obstetric (FIGO) stage, type of radical surgery, histologic type, and grading. Mean hospital cost per discharge was calculated summarizing the cost of daily hospital room charges, operating room, cost of supplies and length of hospital stay. Results A total of 23 women who underwent RSSH were matched with 46 historic controls treated by RMPH in the same institute, with the same surgical team. No significant differences were found in terms of age, histologic type, stage, and grading. Operative time was similar: 102.5 minutes in RMPH and 110 in RSSH (p=0.889). Blood loss was lower in RSSH than in RMPH (respectively, 50 mL vs. 100 mL, p=0.001). Hospital stay was 3 days in RMPH and 2 days in RSSH (p=0.001). No intraoperative complications occurred in both groups. Early postoperative complications were 2.2% in RMPH and 4.3% in RSSH. Overall cost was higher in RMPH than in RSSH (respectively, $7,772.15 vs. $5,181.06). Conclusion Our retrospective study suggests the safety and feasibility of RSSH for staging early endometrial cancer without major differences from the RMPH in terms of surgical outcomes, but with lower hospital costs. Certainly, further studies are eagerly warranted to confirm our findings. PMID:27171672

  20. Early Site Permit Demonstration Program, plant parameters envelopes: Comparison with ranges of values for four hypothetical sites. Volume 2

    SciTech Connect

    Not Available

    1992-09-01

    The purpose of this volume is to report the results of the comparison of the ALWR plan parameters envelope with values of site characteristics developed for our hypothetical sites that generally represent conditions encountered within the United States. This effort is not intended to identify or address the suitability of any existing site, site area, or region in the United States. Also included in this volume is Appendix F, SERCH Summaries Regarding Siting.

  1. Early Regulatory Engagement for Successful Site Remediation: the UK Experience - 13173

    SciTech Connect

    Maitland, R.P.; Senior, D.

    2013-07-01

    The Office for Nuclear Regulation (ONR) is an independent safety, security and transport regulator of the UK nuclear industry. ONR regulates all civil nuclear reactor power stations, fuel manufacture, enrichment, spent fuel reprocessing, most defence sites and installations that store and process legacy spent fuel and radioactive waste. The responsibility for funding and strategic direction of decommissioning and radioactive waste management of state owned legacy sites has rested solely with the Nuclear Decommissioning Authority (NDA) since 2005. A key component of NDA's mandate was to encourage new strategic approaches and innovation to dealing with the UK's waste legacy and which deliver value-for-money to the UK taxpayer. ONR, as an agency of the Health and Safety Executive, is entirely independent of NDA and regulates all prescribed activities on NDA's sites. NDA's competition of site management and closure contracts has attracted significant international interest and the formation of consortia comprised of major British, US, French and Swedish organizations bidding for those contracts. The prominence of US organizations in each of those consortia reflects the scale and breadth of existing waste management and D and D projects in the US. This paper will articulate, in broad terms, the challenges faced by international organizations seeking to employ 'off-the-shelf' technology and D and D techniques, successfully employed elsewhere, into the UK regulatory context. The predominantly 'goal-setting' regulatory framework in the UK does not generally prescribe a minimum standard to which a licensee must adhere. The legal onus on licensees in the UK is to demonstrate, whatever technology is selected, that in its applications, risks are reduced 'So Far As Is Reasonably Practicable' or 'SFAIRP'. By the nature of its role, ONR adopts a conservative approach to regulation; however ONR also recognises that in the decommissioning (and ultimately the site closure) domain

  2. Early Site Permit Demonstration Program: Regulatory criteria evaluation report. Appendix E

    SciTech Connect

    Not Available

    1993-03-01

    The primary objective of the Early Site Permit Demonstration Program (ESPDP) is to demonstrate successfully the use of 10CFR52 to obtain ESPs for one or more US sites for one (or more) ALWR nuclear power plants. It is anticipated that preparation of the ESP application and interaction with NRC during the application review process will result not only in an ESP for the applicant(s) but also in the development of criteria and definition of processes, setting the precedent that facilitates ESPs for subsequent ESP applications. Because siting regulatory processes and acceptance criteria are contained in over 100 separate documents, comprehensive licensing and technical reviews were performed to establish whether the requirements and documentation are self-consistent, whether the acceptance criteria are sufficiently well-defined and clear, and whether the licensing process leading to the issuance of an ESP is unambiguously specified. This document provides Appendix E which contains a population density report. In this study the proposed US Nuclear Regulatory Commission (NRC) population density and exclusion zone size criteria were evaluated for their potential effectiveness to meet the quantitative public health and safety objectives associated with the NRC Safety Goal Policy. In addition, the individual and societal risks from postulated accidents (based on NUREG-1150 methods) were determined and compared to the quantitative prompt and latent health objective of the safety goal policy.

  3. Holocene peatland initiation in the Greater Everglades

    NASA Astrophysics Data System (ADS)

    Dekker, Stefan C.; Boer, Hugo J.; Dermody, Brian J.; Wagner-Cremer, Friederike; Wassen, Martin J.; Eppinga, Maarten B.

    2015-02-01

    The mechanisms involved in the initiation and development of the Greater Everglades peatland ecosystems remain a topic of discussion. In this study, we first present an overview of basal ages of peat deposits in South Florida, which shows two major episodes of peatland initiation between 7.0-4.5 kyr and 3.5-2.0 kyr. Our analysis of regional climate proxy data sets led to three alternative hypotheses that may explain the timing and duration of these two peatland initiation episodes: (1) decreased drainage due to relative sea level (RSL) rise during the Holocene, (2) gradual increase in precipitation throughout the Holocene, and (3) a combination of increasing precipitation, rising RSL, and oscillations in the climate system. We test whether these three hypotheses can explain the pattern of initiation and development of the Greater Everglades peatlands using models that simulate the nonlinear processes involved in peat production and decomposition. The model results suggest that RSL rise could explain the onset of peatland initiation and imply that the climate was wet enough for peat development also during the early Holocene. The first two hypothesized mechanisms in combination with climate oscillations may explain the onset of peat accumulation at 8.2 kyr B.P. The two-phased character of peatland initiation maybe explained by the spatial distribution of local drainage conditions. As peatland development is highly nonlinear, our model uncovers a mechanistic way how peats can suddenly shift from a dry high equilibrium to a wet low equilibrium resulting in lake formation as observed in paleoecological studies in the Greater Everglades.

  4. Holocene peatland initiation in the Greater Everglades

    NASA Astrophysics Data System (ADS)

    Dekker, Stefan; de Boer, Hugo; Dermody, Brian; Wagner-Cremer, Friederike; Wassen, Martin; Eppinga, Maarten

    2015-04-01

    The mechanisms involved in the initiation and development of the Greater Everglades peatland ecosystems in South Florida (USA) remain a topic of discussion. In this study, we present an overview of basal ages of peat deposits in South Florida, which shows two major episodes of peatland initiation between 7.0-4.5 kyr and 3.5-2.0 kyr. Our analysis of regional climate proxy datasets led to three alternative hypotheses that may explain the timing and duration of these two peatland initiation episodes: (1) decreased drainage due to relative sea level (RSL) rise during the Holocene (2) gradual increase in precipitation throughout the Holocene, and (3) a combination of increasing precipitation, rising RSL and oscillations in the climate system. We test whether these three hypotheses can explain the pattern of initiation and development of the Greater Everglades peatlands using models that simulate the non-linear processes involved in peat production and decomposition in combination with the local drainage conditions of Southern Florida. The model results suggest that RSL-rise alone cannot predict the onset of peat initiation in the Greater Everglades using our model setup. The model also implies that the climate was wet enough for peat development also during the early Holocene. The first two hypothesized mechanisms in combination with climate oscillations may explain the onset of peat accumulation at 8.2 kyr BP. The two-phased character of peat land initiation may be explained by the spatial distribution of local drainage conditions. As peatland development is highly non-linear, our model uncovers a mechanistic way how peats can suddenly shift from a dry high equilibrium to a wet low equilibrium resulting in lake formation as observed in paleo-ecological studies in the Greater Everglades.

  5. Holocene history of ENSO variance and asymmetry in the eastern tropical Pacific

    NASA Astrophysics Data System (ADS)

    Carre, Matthieu; Sachs, Julian; Braconnot, Pascale; Purca, Sara; Schauer, Andrew; Falcon, Rommel Angeles; Julien, Michèle; Lavallée, Danièle

    2014-05-01

    Understanding how El Niño-Southern Oscillation (ENSO) is affected by natural and anthropogenic climate forcings requires studying its behavior under contrasted climate conditions. We present a reconstruction of ENSO characteristics in the eastern tropical Pacific during the Holocene based on the statistics of sea surface temperature (SST) variability derived from oxygen isotopes in fossil mollusk shells from Peru. ENSO variance was close to modern level in the early Holocene, and at its lowest level ~4-5 thousand years ago (ka). A shift in ENSO asymmetry indicates a persistent predominance of the central Pacific mode 6.7-7.5 ka. The modern ENSO regime was established ~3 ka. From climate models sensitivity experiments, we attribute the large variability of ENSO in the early Holocene to the wasting of continental ice sheets. These results demonstrate that both variance and spatial structure of ENSO are sensitive to external forcings but that insolation was not the prevailing forcing in the Holocene.

  6. Central southern Africa at the time of the African Humid Period: A new analysis of Holocene palaeoenvironmental and palaeoclimate data.

    NASA Astrophysics Data System (ADS)

    Burrough, Sallie; Thomas, David

    2014-05-01

    The Holocene African Humid Period (c 14.8-5.5 ka) is now recognised in high-resolution records from western Africa as well as in tropical Africa north of the equator. Establishing a clear picture of Holocene environmental changes from palaeodata in central southern Africa is, however, proving both difficult and contentious. This is because in dryland systems in particular it can be difficult to distinguish the effects of sub-millennial scale regional climatic variability from those of major externally-forced global climate changes. We analyse and review existing records for central southern Africa, and neighbouring areas affected by the same climate systems, to attempt to build a clearer spatial picture of regional hydrological system responses during the Holocene. We suggest palaeodata, including new data from Makgadikgadi basin barchan dunes indicate mid-late Holocene aridity following a period of marked hydrological dynamism extending from the early Holocene. We propose that present-day conditions in central southern Africa are relatively stable compared to the early and mid-Holocene and infer that this period of relative stability in the landscape has occurred since ca. 2 ka. We explain Holocene hydrological changes through analysis of changing zonal climatic influences linked to Congo Air Boundary (CAB) and Intertropical Convergence Zone (ITCZ) dynamics, the effects of which filter into the region via complex drainage basin dynamics. It is proposed that, sensu stricto, the AHP was not a spatially uniform feature of early Holocene central southern Africa.

  7. Drivers of Holocene peatland carbon accumulation across a climate gradient in northeastern North America

    NASA Astrophysics Data System (ADS)

    Charman, Dan J.; Amesbury, Matthew J.; Hinchliffe, William; Hughes, Paul D. M.; Mallon, Gunnar; Blake, William H.; Daley, Tim J.; Gallego-Sala, Angela V.; Mauquoy, Dmitri

    2015-08-01

    Peatlands are an important component of the Holocene global carbon (C) cycle and the rate of C sequestration and storage is driven by the balance between net primary productivity and decay. A number of studies now suggest that climate is a key driver of peatland C accumulation at large spatial scales and over long timescales, with warmer conditions associated with higher rates of C accumulation. However, other factors are also likely to play a significant role in determining local carbon accumulation rates and these may modify past, present and future peatland carbon sequestration. Here, we test the importance of climate as a driver of C accumulation, compared with hydrological change, fire, nitrogen content and vegetation type, from records of C accumulation at three sites in northeastern North America, across the N-S climate gradient of raised bog distribution. Radiocarbon age models, bulk density values and %C measurements from each site are used to construct C accumulation histories commencing between 11,200 and 8000 cal. years BP. The relationship between C accumulation and environmental variables (past water table depth, fire, peat forming vegetation and nitrogen content) is assessed with linear and multivariate regression analyses. Differences in long-term rates of carbon accumulation between sites support the contention that a warmer climate with longer growing seasons results in faster rates of long-term carbon accumulation. However, mid-late Holocene accumulation rates show divergent trends, decreasing in the north but rising in the south. We hypothesise that sites close to the moisture threshold for raised bog distribution increased their growth rate in response to a cooler climate with lower evapotranspiration in the late Holocene, but net primary productivity declined over the same period in northern areas causing a decrease in C accumulation. There was no clear relationship between C accumulation and hydrological change, vegetation, nitrogen content

  8. The Temporal Scale of Holocene Climatic Variability: From the Galapagos to Amazonia

    NASA Astrophysics Data System (ADS)

    Bush, M. B.; Restrepo, A.; Correa, A.; Ford, R.; Valencia, B.; Gosling, W.; Silman, M.; Conroy, J.; Overpeck, J. T.

    2006-12-01

    High-resolution lake cores from the Andes and Amazonian lowlands of W. South America and the Galapagos Islands provide new insights into the Holocene climate history of this region and its interactions with Pacific climate drivers. Our data reveal that a major drought event reported broadly from the Andes and Amazonia in the early to mid-Holocene is actually a complex series of droughts with wet interludes. These results suggest strong climatic instability prior to c. 5600 cal. yr BP. Establishment of wetter conditions at our Andean study site at c. 5600 cal. yr BP correspond to the start of Quinoa cultivation. A similar pattern of higher lake levels coinciding with the local spread of agriculture is also evident in the lowlands. Within an overall pattern of progressively wetter conditions over the last 4000 years there are periods of pronounced climatic instability (drought and flood). Fossil pollen, charcoal, sediment color, and carbon content identify periods of peak erosion between c. 900 and 1100 cal. yr BP. On the Galapagos Islands, a subdecadally resolved analysis of fossil pollen provides a striking pattern of climatic change and human-induced alteration of the landscape. Prior to the period of transforming human activity, the fossil pollen record contains a multidecadal oscillation, with wavlet analysis evealing a quasi- periodicty of c. 60 years. Andean pollen are readily identifible in the Galapagos record and transport of mainland pollen to the islands has varied markedly within the past millennium. These multiproxy records reveal the dynamic nature of Holocene climates in the tropics and the impact those changes have had on people and landscapes.

  9. A Holocene molluscan succession from floodplain sediments of the upper Lena River (Lake Baikal region), Siberia

    NASA Astrophysics Data System (ADS)

    White, Dustin; Preece, Richard C.; Shchetnikov, Alexander A.; Parfitt, Simon A.; Dlussky, Konstantin G.

    2008-05-01

    Floodplain sediments of the upper Lena River near Basovo in south-central Siberia have yielded the most detailed Holocene molluscan succession yet reported from the entire eastern Palaearctic. Over 72,500 shells from at least 28 species of terrestrial and 23 species of freshwater mollusc have been recovered, an abundance and diversity far higher than previously reported from the region. The molluscan assemblages are dominated by land snails, especially members of the genus Vallonia, represented by five species including Vallonia tenuilabris and two poorly known species Vallonia kamtschatica and Vallonia cf. chinensis. Other noteworthy species recovered include Gastrocopta theeli, Carychium pessimum, Vertigo extima (southernmost record), Vertigo microsphaera and the first Asian records of three other taxa ( Vertigo geyeri, Vertigo genesii and Vertigo parcedentata). Illustrations are provided for the critical species, since opinions differ about the status of various taxa and the correct names that should be used. The molluscan assemblages show clear successional trends during the early to mid-Holocene, reflecting episodes of dryness/wetness on the floodplain. Drier conditions at ca 6350 14C yr BP coincide with major changes in the archaeological record seen at other sites in the region but it remains unclear whether the two are linked. A prominent charcoal-rich horizon dated to ca 2800 14C yr BP marks a burning event in the catchment, which resulted in a two-fold increase in sediment accumulation rate. Remains of small mammals occurred throughout the sequence including a tooth of Microtus cf. maximowiczii, possibly the first occurrence of Ungar vole west of Lake Baikal. The faunal analyses have been integrated with a detailed pedological study of the sedimentary profile and a chronology was obtained by means of 12 AMS radiocarbon dates. This study provides the first detailed palaeoecological information relating to Holocene molluscan assemblages from the Cis

  10. Inside the “African Cattle Complex”: Animal Burials in the Holocene Central Sahara

    PubMed Central

    di Lernia, Savino; Tafuri, Mary Anne; Gallinaro, Marina; Alhaique, Francesca; Balasse, Marie; Cavorsi, Lucia; Fullagar, Paul D.; Mercuri, Anna Maria; Monaco, Andrea; Perego, Alessandro; Zerboni, Andrea

    2013-01-01

    Cattle pastoralism is an important trait of African cultures. Ethnographic studies describe the central role played by domestic cattle within many societies, highlighting its social and ideological value well beyond its mere function as ‘walking larder’. Historical depth of this African legacy has been repeatedly assessed in an archaeological perspective, mostly emphasizing a continental vision. Nevertheless, in-depth site-specific studies, with a few exceptions, are lacking. Despite the long tradition of a multi-disciplinary approach to the analysis of pastoral systems in Africa, rarely do early and middle Holocene archaeological contexts feature in the same area the combination of settlement, ceremonial and rock art features so as to be multi-dimensionally explored: the Messak plateau in the Libyan central Sahara represents an outstanding exception. Known for its rich Pleistocene occupation and abundant Holocene rock art, the region, through our research, has also shown to preserve the material evidence of a complex ritual dated to the Middle Pastoral (6080–5120 BP or 5200–3800 BC). This was centred on the frequent deposition in stone monuments of disarticulated animal remains, mostly cattle. Animal burials are known also from other African contexts, but regional extent of the phenomenon, state of preservation of monuments, and associated rock art make the Messak case unique. GIS analysis, excavation data, radiocarbon dating, zooarchaeological and isotopic (Sr, C, O) analyses of animal remains, and botanical information are used to explore this highly formalized ritual and the lifeways of a pastoral community in the Holocene Sahara. PMID:23437260

  11. Holocene fluctuations of Quelccaya Ice Cap, Peru based on lacustrine and surficial geologic archives

    NASA Astrophysics Data System (ADS)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.

    2013-12-01

    Peru's Quelccaya Ice Cap (QIC; 13.9°S, 70.8°W, ~5200-5670 m asl) is an important site for understanding tropical paleoclimate, mainly because of annually layered ice cores that provide an ~1800 year long record of tropical paleoclimatic conditions (e.g., Thompson et al., 2013). Here, we present a detailed record of QIC fluctuations using surficial deposits and lake sediments that extend back to late glacial time. We compare the late Holocene records of QIC 10Be-dated moraines and ice core data with lake sediments from a nearby glacially fed lake to establish the framework we use to interpret a Holocene long sediment record from a glacially fed lake. We also examine sediments from a nearby non-glacial lake to constrain non-glacial clastic input. We collected two ~5 m-long sediment cores, one from Laguna Challpacocha, which is currently fed by QIC meltwater, and one from the Laguna Yanacocha, which has not received QIC meltwater since ~12.3 ka. Changes in magnetic susceptibility, loss on ignition, bulk density and X-ray fluorescence chemistry combined with 14C and 210Pb chronologies provide information about sediment transported to the lakes. Retreat from the late Holocene extent defined by the 10Be-dated moraine record (~0.52 ka) is contemporaneous with a sharp transition from organic to clastic sedimentation in the Challpacocha core at ~ 0.52 ka. This implies that glacially-sourced clastic sedimentation, as tracked by loss on ignition, Ti counts and bulk density, increased during ice cap recession. Based on these same proxy data, we suggest the following Holocene history of QIC: QIC receded from the Challpacocha basin by ~10.6 ka. Increased clastic sedimentation at 8.2 - 4.1, 3.6 - 2.7 ka and from 0.55 ka - present are interpreted as times of ice cap recession. The increased clastic sedimentation at ~8.2 - 4.1 ka is consistent with surficial deposits near the present-day ice margin that indicate that at ~7.0 - 4.6 ka QIC was smaller than at present (Buffen et al

  12. Holocene river dynamics in Northland, New Zealand: The influence of valley floor confinement on floodplain development

    NASA Astrophysics Data System (ADS)

    Richardson, J. M.; Fuller, I. C.; Holt, K. A.; Litchfield, N. J.; Macklin, M. G.

    2013-11-01

    Valley floor mapping, sedimentology, and 14C-dating have been used to reconstruct the fluvial history at eight floodplain sites spread throughout Northland, a region removed from the main areas of tectonic and volcanic activity in New Zealand. We present a probability-based record of Holocene river behaviour for Northland using 14C-dated Holocene fluvial deposits and compare this with independent palaeoclimate proxy records from the North Island. Holocene floodplain evolution and fluvial behaviour have been conditioned by the degree of valley-floor confinement. In the most and least confined valley settings, Holocene floodplain evolution has involved the development of a single floodplain surface. At partly confined sites, the river terrace and floodplain geomorphology are more complex. Region-wide progressive floodplain alluviation through the mid to late Holocene and a period of increased river activity between 3500 and 2800 cal. YBP in response to climatically driven increases in sediment supply was followed by a period of valley floor incision and terrace formation beginning after 1900 cal. YBP. In partly confined valley settings, this was followed by the aggradation of a lower Holocene floodplain surface, with rapid rates of vertical accretion in response to post-settlement catchment disturbance. The results of this study indicate that valley floor confinement has played a major role in controlling Northland Holocene river floodplain development, producing a continuum of floodplain and river terrace landforms in response to climatically and anthropogenically driven variations in sediment flux.

  13. Posterior archaeomagnetic dating for the early Medieval site Thunau am Kamp, Austria

    NASA Astrophysics Data System (ADS)

    Schnepp, Elisabeth; Lanos, Philippe; Obenaus, Martin

    2014-05-01

    The early medieval site Thunau am Kamp consists of a hill fort and a settlement with large burial ground at the bank of river Kamp. All these features are under archaeological investigation since many years. The settlement comprises many pit houses, some with stratigraphic order. Every pit house was equipped with at least one cupola oven and/or a hearth or fireplace. Sometimes the entire cupola was preserved. The site was occupied during the 9th and 10th AD according to potshards which seem to indicate two phases: In the older phase ovens were placed in the corner of the houses while during the younger phase they are found in the middle of the wall. In order to increase the archaeomagnetic data base 14 ovens have been sampled. They fill the temporal gap in the data base for Austria around 900 AD. Laboratory treatment included alternation field and thermal demagnetisations as well as rock magnetic experiments. The baked clay with was formed from a loess sediment has preserved stable directions. Apart from one exception the mean characteristic remanent magnetization directions are concentrated around 900 AD on the early medieval part of the directional archaeomagnetic reference curve of Austria (Schnepp & Lanos, GJI, 2006). Using this curve archaeomagnetic dating with RenDate provides ages between 800 and 1100 AD which are in agreement with archaeological dating. In one case archaeomagnetic dating is even more precise. Together with the archaeological age estimates and stratigraphic information the new data have been included into the database of the Austrian curve. It has been recalculated using a new version of RenCurve. The new data confine the curve and its error band considerably in the time interval 800 to 1100 AD. The curve calibration process also provides a probability density distribution for each structure which allows for posterior dating. This refines temporal errors considerably. Usefulness of such an approach and archaeological implications will be

  14. North-south contrast in climate change across northwestern North America during the mid-Holocene transition and the possible relation to western Arctic Ocean sea ice

    NASA Astrophysics Data System (ADS)

    McKay, N.; Kaufman, D. S.

    2013-12-01

    Here we summarize the proxy climate time series from northwestern North America (Alaska and Yukon) included in a new systematic compilation of previously published Arctic Holocene proxy climate records. We identified 27 sites north of 58°N latitude where published proxy records are resolved at sub-millennial scale (at least one value every 400 years) and extend back to at least 6 ka. Each record has a demonstrated relationship with temperature, precipitation or the strength of the Aleutian Low (AL) pressure system. The primary feature of the 20 sites with temperature-sensitive records is a gradual cooling between 6 and 2 ka. These sites are mainly located in southern Alaska and Yukon near the Gulf of Alaska. The three northernmost sites show the opposite trend: warming between 6 and 2 ka. The 13 sites with moisture-sensitive records show a similar north-south disparity in mid-Holocene trends; moisture at the northernmost sites increased between 4 and 2 ka, whereas southerly sites trended towards drier conditions during the interval. AL-sensitive records indicate a decrease in AL strength over the interval, reaching a minimum around 2 ka. Direct orbital forcing would cause gradual cooling throughout the region as summer insolation decreased, and cannot explain the evidence for increasingly warm and wet conditions in the north. Climate model simulations also do not replicate this result: the Transient Climate Evolution of the last 21 ka (TraCE-21) experiment, run with Community Climate System Model (CCSM3), which includes a coupled sea-ice model, does not simulate warming trends anywhere in the western Arctic. One hypothesis to explain this discrepancy is variability in Holocene sea-ice cover in the Chukchi and Beaufort Seas north of the region. Multiple records from marine cores in the Chukchi Sea indicate decreasing sea-ice cover during this interval; high concentrations during the early Holocene may have been associated with Laurentide meltwater, or enhanced sea

  15. Structured Regions of Alpha-synuclein Fibrils Include the Early Onset Parkinson's Disease Mutation Sites

    SciTech Connect

    Comellas Canal, Gemma; Lemkau, Luisel R.; Nieuwkoop, Andrew J.; Kloepper, Kathryn D.; Ladror, Daniel T.; Ebisu, Reika; Woods, Wendy S.; Lipton, Andrew S.; George, Julia M.; Rienstra, Chad M.

    2011-08-26

    Alpha-Synuclein (AS) fibrils constitute the major proteinaceous component of Lewy bodies (LBs), the pathological hallmark of Parkinson’s disease (PD) and other neurodegenerative diseases. Three single point mutations in the AS gene, as well as multiplication of the wild-type (WT) AS allele, have been previously identified in families with early-onset PD. Although AS fibrils have been the subject of intense study, critical details about their structure including the precise location of the B-strands and the extent of the core, the three-dimensional structure and the effects of the mutations—remain unknown. Here, we have used magic-angle spinning solid-state NMR spectroscopy to present a detailed characterization of the full-length WT AS fibrils. With improved sample preparations, isotopic labeling patterns and NMR experiments, we have confidently assigned more than 90% of the 13C and 15N backbone and sidechain chemical shifts of the detected residues from residue 39 to 97, and quantified the conformational dynamics throughout this region. Our results demonstrate that the core of AS fibrils extends with a repeated motif and that residues 30, 46 and 53-the early-onset PD mutant sites-are located in structured regions of AS fibrils.

  16. Holocene disturbance dynamics from a pine-dominated forest in central British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Brown, K. J.; Hebda, N.; Condor, N.; Hebda, R.; Hawkes, B.

    2013-12-01

    A lake sediment record was retrieved from the Sub-Boreal Pine-Spruce biogeoclimatic zone on the Chilcotin Plateau in central British Columbia, Canada. The record is being analyzed for charcoal, pollen, and magnetic susceptibility, as well as insect and mollusc content. The oldest radiocarbon age is 9.2 cal BP, illustrating that the record spans most of the Holocene. Regarding fire disturbance, charcoal fragments are persistent throughout the core, revealing that fire disturbance has characterized the site for millennia. In total, 74 fire events were recognized. During the warm dry early Holocene, fire frequency was 12-15 fires 2000 yr-1 and peak magnitudes were low, possibly in response to a more open landscape. A change in fire regime occurred at ca. 5000 cal BP, as fire frequency increased, peaking at ca. 20 fires 2000 yr-1 by 3000 cal BP. Peak magnitude likewise increased notably, possibly in response to the development of denser forest cover. On-going analysis of pollen will better constrain the vegetation history in this poorly sampled region. In contrast to charcoal, which was pervasive, Dendroctonus ponderosae (mountain pine beetle) remains were absent in both modern and paleo samples. Given that several insect outbreaks have occurred in the region in the last 100 years, the scarcity of remains is likely related to taphonomic issues.

  17. Collaborative community hazard exposure mapping: Distant Early Warning radar sites in Alaska's North Slope

    NASA Astrophysics Data System (ADS)

    Brady, M.

    2015-12-01

    A method to produce hazard exposure maps that are developed in collaboration with local coastal communities is the focus of this research. Typically efforts to map community exposure to climate threats over large areas have limited consideration of local perspectives about associated risks, constraining their utility for local management. This problem is especially acute in remote locations such as the Arctic where there are unique vulnerabilities to coastal threats that can be fully understood only through inclusion of community stakeholders. Through collaboration with community members, this study identifies important coastal assets and places and surveys local perspectives of exposure to climate threats along Alaska's vast North Slope coastline spanning multiple municipalities. To model physical exposure, the study adapts the U.S. Geological Survey's (USGS) coastal vulnerability index (CVI) to the Arctic context by incorporating the effects of open water distance determined by sea ice extent, and assigning CVI values to coastal assets and places according to direction and proximity. The study found that in addition to concerns about exposed municipal and industrial assets, North Slope communities viewed exposure of traditional activity sites as presenting a particular risk for communities. Highly exposed legacy Cold War Distant Early Warning Line sites are of particular concern with impacts ranging from financial risk to contamination of sensitive coastal marine environments. This research demonstrates a method to collaboratively map community exposure to coastal climate threats to better understand local risks and produce locally usable exposure maps.

  18. Holocene environmental change in Kamchatka: A synopsis

    NASA Astrophysics Data System (ADS)

    Brooks, S. J.; Diekmann, B.; Jones, V. J.; Hammarlund, D.

    2015-11-01

    We present a synthesis of the results of a multiproxy, multisite, palaeoecological study of Holocene environmental change in Kamchatka, Far East Russia, details of which are presented elsewhere in the volume. We summarise the results of the analyses of pollen, diatom, chironomid, and testate amoebae assemblages, together with stable isotopes of oxygen and carbon, and sediment characteristics from the sediments of five lakes and a peat succession on a latitudinal gradient of the Kamchatka Peninsula, to infer environmental change and establish the major climate forcers and climatic teleconnections. There are synchronous shifts in the assemblage composition of most of the biota and across most sites at 6.5-6.2 ka BP, 5.2 ka BP, 4.0 ka BP, and 3.5 ka BP, suggesting a response to strong regional climate forcing at these times. These dates correspond to the warmest part of the Holocene Thermal Maximum (HTM) (6.5-6.2 ka BP), the beginning of the Neoglacial cooling (5.2 ka BP), the coolest and wettest part of the Neoglacial (4.0 ka BP), and a switch to warmer and drier conditions at 3.5 ka BP. Our results provide evidence for the penetration and domination of different air masses at different periods during the Holocene. Cool and dry periods in winter (e.g., at 6.0 ka BP) were driven by a relatively weak pressure gradient between the Siberian High and the Aleutian Low, whereas cool, wet periods in winter (e.g., the Neoglacial and during the LIA) developed when these two systems increased in strength. Warm, dry, continental periods in summer (e.g., at 2.5 ka BP) were driven by a weakening of the Siberian High. We find that the timing of the HTM in Kamchatka is later than in the Eurasian arctic but similar to northern Europe and the sub-arctic part of eastern Siberia. This progressive onset of the HTM was due to the effects of postglacial ice-sheet decay that modulated the routes of westerly storm tracks in Eurasia. A major ecosystem driver was the Siberian dwarf pine Pinus

  19. The Birougou Mountains: Forested throughout the Holocene

    NASA Astrophysics Data System (ADS)

    Pietsch, S. A.; Tanga, J.-J.; Ngok-Banak, L.

    2009-04-01

    The Congo basin with an area of ~400 million ha harbours the second largest tropical forest complex of the world which covers ~60% of the area. Besides tropical rain forest the savannah biome comprises the second naturally abundant ecosystem type. During the Holocene (20.000 yrs. BP - Modern Times) the distribution of forest and savannas changed with changing climate and during the last glacial maximum (~20.000 yrs. BP) most of the Congo basin was covered by savannas and the Congolian rain forests were confined to refuge areas. Later the distribution between savannas and rainforest changed with changing climate, whereby in some regions rainforest and savannas replaced each other while on some sites one vegetation type persisted. During drier periods of the Holocene the rain forest biome was confined to refuge areas, which formed a conservation reservoir for forest re-extension during more humid, i.e. forest favourable, climatic periods. In order to understand the dynamics of the forest/savannah replacement process reference states of patches of stable savannah or stable rain forest are needed. Within this paper we will describe a patch of stable rain forest vegetation located at the Birougou Mountains in Gabon, and demonstrate that rain forest vegetation has continuously persisted since the Holocene climate optimum dated at around ~6.000 yrs. B.P. by using the signature of stable Carbon isotope discrimination of photosynthesis. Savannah grasses follow the C4-type of photosynthesis while forest vegetation exhibits C3 photosynthesis. Accordingly they differ in the d13C ratios of carbon incorporated into biomass. Soil organic Carbon originates from decomposition of litter inputs. d13C values along a vertical soil profile thus indicate persistence or past changes in vegetation cover. 14C age of soil humic acids, indicate the mean residence time of soil organic carbon. Results indicate that at the Birougou mountains (in contrast to other parts of the Congo basin) litter

  20. ALERTES-SC3 Early Warning System prototype for South Iberian Peninsula: on-site approach.

    NASA Astrophysics Data System (ADS)

    Pazos, Antonio; Lopez de Mesa, Mireya; Gallego Carrasco, Javier; Martín Davila, José; Rioja del Rio, Carlos; Morgado, Arturo; Vera, Angel; Ciberia, Angel; Cabieces, Roberto; Strollo, Angelo; Hanka, Winfried; Carranza, Marta

    2016-04-01

    In recent years several Earthquake Early Warning Systems (EEWS) have been developed for different parts of the world. The area between SW Cape St. Vicente and the Strait of Gibraltar is one of the most seismically active zones in the Ibero-Maghrebian region, with predominantly moderate and superficial seismicity, but also big events with associated tsunamis are well documented in the area, like the 1755 Lisbon earthquake. In the frame of the ALERT-ES (2011-2013) and ALERTES-RIM (2014-2016) Spanish projects, the ALERTES-SC3 EEWS, regional approach, prototype has been developed at the Royal Spanish Navy Observatory (ROA) and is being tested in near real time for south Iberia. This prototype, based on the SeisComP3 software package, is largely based on algorithms derived from the analysis of the first seconds of the P wave records. Calculation of several parameters are carried out, mainly the characteristic period (τc) and the displacement peak (Pd), but also the velocity peak (Pv), the maximum period (τPmáx), among others. In order to warm the areas closest to the hypocentre, places located inside the "blind zone", a on-site EEWS has also been developed by ROA and integrated in the ALERTES-SC3 prototype. From the on-site approach, a warm level is declared from one station as a function of the estimated characteristic period (τc) and the displacement Peak (Pd), although the earthquake location and therefore the lead time available remains unknown. This on-site EEWS is being tested in several Western Mediterranean net (WM) stations as ARNO (Arenosillo, Huelva,Spain) or CHAS (Chafarinas island, North Africa, Spain). Also an on-site low cost station is being developed based in low cost accelerometers. In this work the current state of the on-site EEWS developed, its integration in the ALERTES-SC3 EEWS system and the low cost seismic stations are shown.

  1. Early hominin dental remains from the Plio-Pleistocene site of Drimolen, South Africa.

    PubMed

    Moggi-Cecchi, Jacopo; Menter, Colin; Boccone, Silvia; Keyser, André

    2010-05-01

    The Plio-Pleistocene fossil hominin site of Drimolen is located approximately 5.5km north of the other well-known South African Plio-Pleistocene sites (Sterkfontein, Swartkrans, Kromdraai, Coopers). It was discovered by A.W. Keyser in 1992. Systematic excavations led to the recovery of a remarkable number of fossil vertebrate taxa, including hominins. Most of the specimens collected consist of isolated teeth or those in jaws. The aim of this paper is to provide a morphological description of the dental specimens. The taxonomic allocation of each specimen is also reported, either confirming or revising previous provisional attributions. The analysis confirms the occurrence of two hominin species, Paranthropus robustus and Homo sp. With over 80 fossil hominin specimens recovered so far, Drimolen is the second largest sample of P. robustus, after Swartkrans. At Drimolen, P. robustus is represented mostly by craniodental specimens (63) among which are 47 isolated teeth and the remainder are maxillary and mandibular fragments with teeth. The assemblage markedly increases the dental sample of P. robustus. Furthermore, the Drimolen sample includes tooth classes not present in the Swartkrans or Kromdraai samples. The new tooth classes include both deciduous upper lateral incisors (DNH 31) and canines (DNH 23). In the dental sample described here there are nine specimens probably attributable to Homo, although a specific attribution is not yet possible. These specimens expand the small sample of early Homo from South African sites. Basic dimensions (MD and BL) of the Drimolen dental remains are compared in a preliminary analysis with other hominin samples. This analysis delineates the Drimolen P. robustus dental sample as characterized by smaller teeth overall than the Swartkrans sample (and in some cases also smaller than the Kromdraai sample), as well as a greater size range. PMID:20362324

  2. An Early Cenozoic Ichthyolith Record from Demerara Rise (ODP Site 1258: Equatorial Atlantic Ocean)

    NASA Astrophysics Data System (ADS)

    Bryant, R. M.; Sibert, E. C.; Norris, R. D.

    2014-12-01

    Peak global warmth during the early Eocene is a partial analog to the future structure of marine ecosystems in a high pCO2 world. Early Eocene oceans are generally regarded as supporting warmer oceans with lower overall productivity than today owing to the low concentrations of preserved organic matter in pelagic sediments. It has also been proposed that Eocene oceans were about as productive as now, but higher respiration rates in a warmer-than-modern ocean more efficiently recycled organic matter and nutrients. We investigated Eocene export productivity and its link to taxonomic diversity using the pelagic ichthyolith record. Ichthyoliths are calcium phosphate microfossils including fish teeth and shark denticles and their fragments, and are a unique paleoceanographic proxy because they represent a fossil record for marine vertebrates, a charismatic and tangible part of the ecosystem that generally goes unrepresented in the fossil record. Analysis of the ichthyolith record in Ocean Drilling Program Site 1258 (NE South America) shows a remarkable increase in accumulation rate of ichthyoliths from the Paleocene into the Eocene, suggesting that onset of the Early Eocene Climatic Optimum in the equatorial Atlantic was favorable to fish production. Our results suggest that, if anything, the early Eocene maintained higher productivity than in the late Paleocene. These results compare favorably with a record of ichthyolith accumulation in the South Pacific (DSDP 596), which also indicates unusually high rates of fish productivity in the peak of Eocene warm climates. Low resolution data sets from the Pacific suggest an explosion of morphotypes during the warm period associated with an increase in ichthyolith mass accumulation rates. Peak global warmth, therefore, appears to be associated with both higher fish production and higher taxonomic diversity than suggested by previous reconstructions of Eocene primary production. Increasing the amount of continuous records of

  3. Holocene fire history reconstruction using Tibetan lacustrine sediments

    NASA Astrophysics Data System (ADS)

    Callegaro, Alice; Kirchgeorg, Torben; Battistel, Dario; Bird, Broxton; Barbante, Carlo

    2016-04-01

    The important role that biomass burning playsin influencing the Holocene'sclimate is still under discussion. The present work gives information about past biomass burning events in the Tibetan Plateau and helps to increase the understanding of the interaction between climate, humans and fire activity during Holocene. Asiatic area is one of the centers of the advent of agriculture and pastoralism, and it is a strategic area for understanding the interaction between human and fire during the Holocene. We reconstructed past biomass burning events and vegetation from sediments collected from lake Paru Co, a small moraine dammed lake located in the Tibetan Plateau at 4845 m above sea level. We extracted lake sediment samples by accelerate solvent extraction and analysed different organic molecular proxies by GC-MS and IC-MS. We used monosaccharide anhydrides, levoglucosan and its isomers, as proxies for biomass burning. These are specific molecular markers originated from the pyrolysis of cellulose showing significant fire events and indicate changes in burned fuel. Furthermore we analysed polycyclic aromatic hydrocarbons (PAH) as additional combustion proxies. For a better understanding of changes in vegetation andof human habitation at the lake shore we analysed n-alkanes and sterols. Comparing the data of this multi-proxy approach used in the studied area with climatic and meteorological literature data, reconstruction and contextualization of past fire events are possible: we can see the agreement between dry climate period and presence of more intense fire events, especially in the Early Holocene.

  4. Pleistocene and Holocene geomorphological development in the Algarve, southern Portugal

    NASA Astrophysics Data System (ADS)

    Chester, David K.

    2012-06-01

    A detailed chronological framework for Pleistocene and Holocene geomorphology and landscape evolution in the Algarve is proposed. With regards to the Pleistocene, attention has focused on the origin, dating and stratigraphy of the Ludo Formation. Subsuming the classifications of earlier writers, it is now proposed that during the Pliocene a marine transgression occurred across a tectonically controlled basin that was constrained by the mountains of the Algarve interior to the north. Fluvial sands were then deposited in a regressive phase during the late Pliocene/early Pleistocene, while braided streams operating under semi-arid conditions subsequently laid down sands and gravels in the middle and upper Pleistocene. Lying unconformably over the Ludo Formation is an alluvial deposit (Odiáxere gravels and Loulé sands) of late Pleistocene/early Holocene date that is found within the river valleys of the Algarve. In the early-Holocene (ca.10, 000-ca.7000 BP) and early late-Holocene (ca.5000-ca.3000 BP), the situation in the Algarve was one of climatic amelioration (i.e., warmer and wetter conditions), rising sea levels, vegetation colonization, soil development and towards the end of this period trenching of the Odiáxere gravels and Loulé sands. From ca.3000 BP evidence is abundant that humans became important geomorphological agents either acting on their own or in combination with climatic factors. From around 5000 BP, conditions became dryer and, between ca.3000 BP and ca.700 BP, clearance of land by pre-Roman, Roman, and especially Islamic agricultural settlers caused widespread erosion and the deposition of extensive spreads of topsoil dominated sediment within river valleys (i.e., the Holocene terrace) and in coastal estuaries. A period followed up to 1900 CE when agricultural practices were less damaging to the soil, erosion was reduced and the Holocene terrace - together with coastal and estuarine deposits - was incised. In the past century and under

  5. New data on the stratigraphy and pedology of the Clovis and Plainview sites, Southern High Plains

    NASA Astrophysics Data System (ADS)

    Holliday, Vance T.

    1985-05-01

    The well known Clovis and Plainview archaeological sites of New Mexico and Texas have yielded new data on regional late Quaternary geologic, paleoclimatic, and pedologic histories. Eolian sedimentation at the Clovis site from about 10,000 to less than 8500 yr B.P. was followed by the formation of a cumulic soil between 8500 and 5000 yr B.P. Episodic eolian and slope wash deposition then culminated in massive eolian sedimentation about 5000 yr B.P. after which a Haplustalf formed then was subsequently buried by part of a dune system within the last 1000 yr. At the Plainview site, a basal stream gravel contains Plainview cultural material (ca. 10,000 yr B.P.), which is followed by a localized early Holocene lacustrine deposit, two eolian deposits (the younger dating to about 5000 yr B.P.), and a marsh deposit which slowly accreted as an Argiustoll formed in the younger eolian unit. The data indicate that on the Southern High Plains (1) between 12,000 and 8500 yr B.P. sedimentation varied from site to site, (2) there was a regional climate change toward warming and drying in the early Holocene, (3) two episodes of severe drought apparently occurred in the middle Holocene (6500 to 4500 yr B.P.), (4) between 4500 yr B.P. and the present an essentially modern climate existed, but with several shifts toward aridity within the last 1000 yr, (5) argillic horizons have developed in late Holocene soils, (6) clay illuviation can occur in calcareous soils, and (7) long-distance correlation of Holocene stratigraphy in the region is possible, particularly with the aid of soil morphology.

  6. An Early Middle Eocene Orbital Scale Benthic Isotope Record From IODP Site 1408, Newfoundland Rise

    NASA Astrophysics Data System (ADS)

    Wu, F.; Lawler, N.; Penman, D. E.; Zachos, J. C.; Kirtland Turner, S.; Norris, R. D.; Wilson, P. A.; Hull, P. M.

    2014-12-01

    The long-term Paleogene global cooling trend and eventual glaciation of Antarctica has been attributed to a reduction in greenhouse gas levels as well as changes in the configuration of high-latitude oceanic gateways. This major trend in climate and forcing is known to have initiated in the early middle Eocene, between 44-49 Mya, yet our understanding of the detailed evolution of climate and oceanic circulation and carbon chemistry of this critical interval has been limited for lack of high-resolution proxy climate records. Integrated Ocean Drilling Program (IODP) Expedition 342, designed in part to address this deficiency, successfully recovered highly expanded sequences of middle Eocene sediment from multiple sites in the western North Atlantic, with several sites characterized by high sedimentation rates (>2.8 cm/kyr) and pronounced lithologic cycles. Using samples from cores recovered at one of these sites, 1408, located on Southeast Newfoundland Ridge, we are reconstructing the first orbital-scale deep sea δ18O and δ13C records spanning a ~1.6 million year interval (~Chron 20r) of the middle Eocene. Based on analyses of benthic foraminifer N. truempyi, our preliminary data reveal distinct high-frequency cycles with periods matching those of the orbital cycles, particularly precession and obliquity. Cross spectral analysis of δ18O, δ13C and lithologic records reveal a high degree of coherency, implying a high sensitivity in local sediment fluxes and bottom water chemistry (and circulation) to orbital forcing. Also, given the location and depth (~2600 m at 50 Ma), Site 1408 constrains the end-member composition of northern component bathyal bottom waters so that comparison with benthic isotope records from the south Atlantic and other basins can be used to assess ocean circulation patterns in the mid-Eocene. In general, bottom water temperatures appear to have been warmer, and DIC δ13C lower than observed elsewhere. Thus, our preliminary results are

  7. Effects of Holocene vegetation change on soils across the forest-grassland transition, northern Minnesota, and implications for erosion processes

    NASA Astrophysics Data System (ADS)

    Mason, Joseph; Kasmerchak, Chase; Keita, Hawa; Liang, Mengyu; Gruley, Kristine

    2016-04-01

    Boundaries between forest and grassland in the midlatitudes and their shifts in response to Holocene climatic change, provide opportunities to detect effects of life on landscapes. In northern Minnesota, USA, paleoecological research has documented that grassland and/or savanna expanded eastward in the dry early to middle Holocene. In the late Holocene, forest cover expanded westward at the expense of savanna and grassland. We studied soils at 20 sites spanning the forest-grassland transition. A dramatic change in soil morphology coincides approximately, though not exactly, with that transition as recorded in 1870s-1880s land surveys, suggesting that soils change rapidly in response to forest expansion (we are attempting to constrain the timescale of response through radiocarbon dating of deep soil organic matter in which stable C isotopes record past presence of grassland). The key changes from grassland to forest are loss of organic matter below a thin surface A horizon and greatly enhanced mobility and downward translocation of clay - particularly smectite - in forest soils. This results in upper soil horizons that have relatively low smectite content and low microaggregate stability (as detected through laser diffraction analysis of aggregate disintegration in laboratory experiments), especially below the thin A horizon. The best explanation for this change appears to involve differences in how OM is added to and accumulated in the soil under forest and grassland; soil acidity and base saturation change more gradually eastward along a gradient more likely to reflect climate than vegetation. Evidence of bioturbation (especially gopher burrowing) is much more common at former grassland sites. In addition to mixing OM downward in the soil, burrowing moves detrital carbonates upward, probably enhancing OM accumulation and aggregate stability. Research on geomorphic response to Holocene climatic change in the Midwestern US has often emphasized higher potential

  8. [Chemical composition analysis of early neolithic pottery unearthed from Xiaohuangshang site, Zhejiang Province and Jiahu site, Henan Province by energy disperse X-ray fluorescence].

    PubMed

    Chen, Qian-Qian; Yang, Yu-Zhang; Zhang, Ju-Zhong; Cui, Wei

    2011-11-01

    The major elements in the early neolithic potteries unearthed from Xiaohuangshan site, Zhejiang Province and Jiahu site, Henan Province were determined by energy disperse X-ray fluorescence (EDXRF). The results show that the chemical compositions of the potteries from these two sites possess obvious regional features respectively. Compared with the specimen from Jiahu site, the potteries from Xiaohuangshan site have the common feature of ancient Chinese southern ceramics with high silicon and low aluminum contents. Simultaneously, the chemical composition of Xiaohuangshan pottery samples nearly unchanged from its early stage to the last stage. This phenomenon indicates that the source of the ceramic raw materials of Xiaohuangshan site was stable, and the continuous improvement of its pottery quality was mainly due to the progress in sintering techniques. However, the chemical composition of Jiahu potteries changed a lot in its three different periods. This change occurred because a large number of admixtures were added to the pottery bodies to improve their operating performances. These results also show that the improvements of pottery making techniques in different Chinese areas may have their own evolution directions respectively for the different geographical environments. PMID:22242535

  9. Holocene environmental evolution of the SE Greenland Shelf North and South of the Denmark Strait: Irminger and East Greenland current interactions

    NASA Astrophysics Data System (ADS)

    Jennings, A.; Andrews, J.; Wilson, L.

    2011-04-01

    Holocene climatic and paleoceanographic development of the SE Greenland Shelf is studied from cores MD99-2317 and MD99-2322, at sites north and south of the Denmark Strait, respectively. Lithofacies, IRD counts, calcium carbonate percentages, benthic and planktic foraminiferal assemblages and oxygen isotope analyses, and summer SSTs reveal significant climate variations in the Holocene driven by declining solar insolation and its interaction with waning continental ice sheets, and changing atmospheric pressure patterns. Large changes in the East Greenland and Irminger Currents and the Greenland Ice Sheet are manifested as a 4-part division of the Holocene. An early Holocene cold interval dominated by melting of the Greenland Ice Sheet and Polar Front retreat extends from 11.8 to 9.5 cal kyr BP. A cold interval from 9.5 to 8.1 cal kyr BP involved episodic cooling of the Irminger Current resulting from the last phases of Laurentide Ice Sheet deglaciation and delayed the Holocene optimum off East Greenland by 3 kyr relative to peak summer solar insolation, which likely helped to limit the early Holocene melting of the Greenland Ice Sheet. The period 8.1-3.5 cal kyr BP represents a climatic optimum interval of maximum Greenland Ice Sheet retreat and strong Irminger Current inflow to the Denmark Strait. Between 6.8 and 3.5 cal kyr BP, the Irminger Current penetrated further North into the Nordic Seas than has been observed in recent decades. This signal is consistent with diminished northerly winds, a weaker Greenland High and contracted subpolar gyre. By 5 cal kyr BP, periods of increased Polar Water and decreasing salinity in the Irminger Current suggest a transition toward expansion of the subpolar gyre and increased Polar Water in the EGC. The Neoglacial interval from 3.5 to 0.2 cal kyr BP was cold and variable with increased freshwater forcing from the Arctic Ocean, advance of the Greenland Ice Sheet and southward advance of the Polar Front. Enhanced northerly

  10. A pollen-based environmental reconstruction in Lake Hazar (Eastern Turkey) during the Late Pleistocene-Holocene: Example for the Eastern Mediterranean Realm

    NASA Astrophysics Data System (ADS)

    Biltekin, Demet; Kadir Eris, Kürsad; Namik Cagatay, Memet; Nagihan Arslan, Tugce; Akcer On, Sena; Acar, Dursun

    2016-04-01

    difference between Lake Hazar and some Near East sites is found concerning the delay during the early Holocene expansion of Quercus pollen. Such delay from the other studied sites in the Eastern Mediterranean has not been recorded in Lake Hazar. This can be explained by the existence of a warm and humid climate which provided favorable conditions for spreading of deciduous Quercus, starting in the early Holocene.

  11. Holocene cold events on the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Mischke, Steffen; Zhang, Chengjun

    2010-06-01

    A lake sediment core from the eastern Tibetan Plateau was investigated by multi-proxy geochemical, sedimentological and magnetic analyses and its age determined using 14C AMS dating in an approach to use short-lived climate periods for a spatial assessment of the Holocene climate history on the Tibetan Plateau. Six cold events were identified from the Lake Ximencuo record which occurred between 10.3-10.0, 7.9-7.4, 5.9-5.5, 4.2-2.8, 1.7-1.3 and 0.6-0.1 cal ka BP. A comparison with previously published Holocene records from lake and peat sections, ice cores and glacial remains of the Tibetan Plateau revealed that the cold event starting around 4.2 cal ka BP had the most significant and widespread impact on almost all of the examined sites. This cold event lasted about a millennium in the western and central part of the Tibetan Plateau and possibly several hundred years longer at some sites in its eastern realm. The cold event inferred between 7.9 and 7.4 cal ka BP from Lake Ximencuo was recorded at a number of sites on the eastern Tibetan Plateau too and probably corresponds to a cold event identified around 8.2 cal ka BP at the sites on the western and central Tibetan Plateau. The coincidence with the 8.2 ka event of the North Atlantic region implies that the latter exerted a significant environmental impact on the Tibetan Plateau too. The cold spell between 10.3 and 10.0 cal ka BP was recorded at some marginal sites of the Tibetan Plateau but had apparently a less significant environmental impact. The more irregular pattern of cold events between about 7 cal ka BP and the onset of the cold event after 4.2 cal ka BP might be related to the catchment-specific response of the lake sediment and peat accumulation to the termination of the Holocene 'climatic optimum' on the Tibetan Plateau. The final two cold events between 1.7 and 1.3 cal ka BP and in the last several hundred years representing the Little Ice Age are more widely seen on the Tibetan Plateau although they

  12. Advancing family health through the Garden of Eatin': on-site food gardens in early childhood education.

    PubMed

    Chaufan, Claudia; Yeh, Jarmin; Sigal, Byron

    2015-04-01

    Nutritional practices develop over the life course. Developing healthy habits at an early age can contribute to combating increasing child obesity rates. Through a range of activities that rely on the presence of an on-site food garden, North Bay Children's Center (NBCC), an early childhood education program, has enacted a "culture of health" into all aspects of the curriculum to promote healthy eating practices among children, families, teachers and staff. NBCC's garden program serves as a model in early childhood education and as a community-based intervention to improve family health and prevent child obesity. PMID:25713934

  13. Holocene and deglacial paleoenvironmental history of the Peru-Chile current system and adjacent continental Chile

    NASA Astrophysics Data System (ADS)

    Lamy, F.; Hebbeln, D.; Kim, J.; Mohtadi, M.; Ruehlemann, C.

    2002-12-01

    A combined analysis of terrigenous and biogenic compounds in marine sediments from the Chilean continental slope allows detailed reconstructions of both the paleoclimatic and paleoceanographic history of this region during the last glacial and Holocene. Based on sediment cores recovered during two cruises with the German R/V Sonne, we found evidence for changes both in continental rainfall, most likely induced by latitudinal shifts of the Southern Westerlies, and marine productivity as well as sea surface temperature (SST) changes within the Peru-Chile Current system on time scales ranging from Milankovitch to centennial-scale. On Milankovitch time-scales, we found strong evidence for precession-controlled shifts of the Southern Westerlies implying e.g. more humid conditions during the LGM in the Chilean Norte Chico and a trend towards more arid climates during the deglaciation culminating in the early Holocene. These shifts are paralleled by paleoceanographic changes indicating generally higher productivity during the LGM mainly caused by increased advection of nutrients from the south through an enhanced Peru-Chile current. SSTs off central Chile were about 3.5 C lower than present during the LGM. On shorter time-scales, extremely high resolution sediment cores from the southern Chilean margin provide evidence of significant short-term Holocene climate changes with bands of variability centred at ca. 900 and 1500 years, periodicities also well known from Northern Hemisphere records. Our data point to strong interhemispheric connections of climate change both on multi-centennial to millennial and Milankovitch time-scales with a major role of the tropics for the interhemispheric transfer of climate signals involving changes within the Hadley circulation and/or probably long-term modifications of the El Ni¤o-Southern Oscillation system. The recently drilled ODP Sites 1233 (ca. 41S) and 1234/1235 (ca. 36S) at the southern Chilean margin have the potential to extent

  14. Site fidelity and condition metrics suggest sequential habitat use by early juvenile snook

    USGS Publications Warehouse

    Brame, Adam B.; McIvor, Carole; Peebles, Ernst B; Hollander, David J.

    2014-01-01

    The common snook Centropomus undecimalis is an estuarine-dependent fish that relies on landward wetlands as nursery habitat. Despite its economic importance, portions of the snook's early life history are poorly understood. We compared habitat use of young-of-the-year (YOY) snook in 2 geomorphic mesohabitats (tidal pond and tidal creek) along an estuarine gradient (upstream vs. downstream) within a single wetland during fall recruitment. We used abundance, length, condition indices, and stable isotopes to assess ontogenetic mesohabitat use and site fidelity. We found that (1) YOY snook were more abundant within the upstream creek and ponds; (2) the smallest snook were found only in ponds; (3) snook from ponds had lower condition (Fulton's K and hepatosomatic index); (4) snook began moving from ponds to the creek at ~40 mm standard length; and (5) snook from the 2 mesohabitats were isotopically distinct, indicating high site fidelity at rather small spatial scales. Collectively, these data identified sequential use of mesohabitats, wherein seaward-spawned YOY snook moved landward and recruited to pond habitats, where they dedicated energy to growth (as length) before making an ontogenetic habitat shift to the creek. Once in the creek, YOY snook condition improved as they approached maturity and started the downstream return towards seaward locations. The wetland network that was previously viewed as generalized nursery habitat instead consists of mesohabitats that support different life stages in sequence. This represents ontogenetic habitat complementation, in which lower availability of a required mesohabitat type may limit the entire wetland's contribution to the adult population.

  15. Mass safe male circumcision: early lessons from a Ugandan urban site - a case study

    PubMed Central

    Galukande, Moses; Sekavuga, Denis Bbaale; Duffy, Kevin; Wooding, Nicholas; Rackara, Sam; Nakaggwa, Florence; Nagaddya, Teddy; Elobu, Alex Emmanuel; Coutinho, Alex

    2012-01-01

    Introduction It has been proven in several randomized clinical trials that HIV transmission from female to male is reduced by 60% and more among circumcised males. The national target for Uganda by 2015 is to circumcise 4.2 million adult males, an unprecedented number requiring a pragmatic approach and effective model(s) to deliver this target. The objective of the study was to describe early lessons learnt at a start up of a mass safe male circumcision (SMC) program in an urban Ugandan site, implemented through task shifting and a private public partnership approach. Methods A case study of an urban SMC site in Uganda's capital, Kampala with a catchment population of approximately 0.8 million adult males aged between 15 and 49 years. Client enrollment was voluntary; mobilization was by word of mouth and through the media. Non Physician clinicians (NPC) carried out the majority of the SMCs. The SMC and voluntary counseling and testing (VCT), adverse events (AE) management and follow up were done as per set national guidelines. The supervision was by a public and private service provider. All clients were consented. Results A total of 3000 males were circumcised in 27 days spread over four months. The AE rate was 2.1% all AEs were mild and reversible. No deaths occurred. The work rate was 111 SMCs per day. There was sufficient demand for SMC despite minimal mobilization effort. The bulk of the SMC work was successfully carried out by the NPCs. Conclusion Private Public Partnership and task shifting approaches were successful at the start up phase and we anticipate will be feasible for the scale up. PMID:23396906

  16. Holocene peatland shifts in vegetation, carbon, and climate at Imnavait, Alaska

    NASA Astrophysics Data System (ADS)

    Peteet, D. M.; Nichols, J. E.; Ouni, S.; Pavia, F.; Pearl, Y.

    2012-12-01

    The Imnavait Creek basin (68 40'N, 149 20'W; elevation 875-945 m) in the foothills of the Brooks Range, AK has been well studied in terms of modern vegetational communities, hydrology, and soils. But paleoclimate and paleovegetation reconstructions are limited. We retrieved a 2-m peatland core to examine the macrofossil/biomarker/carbon sequestration history throughout the Holocene and late-glacial. AMS 14C dates of the macrofossil remains will allow us to calculate carbon sequestration rates. The Holocene history (the top meter) records marked shifts in vascular plant as well as bryophyte history. A tri-partite sequence is apparent, with Andromeda/Sphagnum remains abundant in the early Holocene. The absence of bryophytes and the presence of Eriophorum and Carex achenes characterize the mid-Holocene. Andromeda and Betula nana with Sphagnum remains are abundant in the upper 30 cm of the core. Hydrogen isotope ratios of leaf wax alkanes record higher effective moisture in the early and late Holocene, suggesting more evaporative loss in the mid-Holocene which is characterized by Eriophorum. We compare our results with previously observed palynological shifts from lakes in the region and place this Arctic paleorecord in a larger perspective of peatland histories in a N-S transect covering nearly 10 degrees of latitude across Alaska. This tripartite pattern of effective moisture appears to be the same throughout the Alaskan transect, suggesting strong climatic control.

  17. Hand and foot remains from the Gran Dolina Early Pleistocene site (Sierra de Atapuerca, Spain).

    PubMed

    Lorenzo, C; Arsuaga, J L; Carretero, J M

    1999-01-01

    We report here the study of the 22 hand and foot remains from the Early Pleistocene level TD6 of the Gran Dolina site at Sierra de Atapuerca (Burgos, Spain) recovered from 1994 to 1996. These remains are paratypes of Homo antecessor. All of the elements are briefly described and compared with other fossil hominids. The capitate has a constricted neck, well developed head, strong attachment for the ligamentum interosseum trapezoid-capitate, a palmarly placed trapezoid facet with a distinctive small dorsal trapezoid facet, a highly curved and oblique orientation of the second metacarpal facet, and a transversally oriented dorsodistal border. A hamate with a moderately projecting and lightly built hamulus; an inferred reduced styloid process on the third metacarpal base; a wide second metacarpal head; and middle phalanges with well marked insertions for the flexor digitorum superficialis muscle and wide heads. The morphology and dimensions of the pedal remains from TD6 are very similar to modern humans; but the base, proximal articular surface and shafts of the proximal hallucal phalanges are more rounded and the midshaft of the proximal toe phalanx is wider. PMID:10496998

  18. Early life establishment of site-specific microbial communities in the gut

    PubMed Central

    Romano-Keeler, Joann; Moore, Daniel J; Wang, Chunlin; Brucker, Robert M; Fonnesbeck, Christopher; Slaughter, James C; Li, Haijing; Curran, Danielle P; Meng, Shufang; Correa, Hernan; Lovvorn III, Harold N; Tang, Yi-Wei; Bordenstein, Seth; George Jr, Alfred L; Weitkamp, Jörn-Hendrik

    2014-01-01

    Fecal sampling is widely utilized to define small intestinal tissue-level microbial communities in healthy and diseased newborns. However, this approach may lead to inaccurate assessments of disease or therapeutics in newborns because of the assumption that the taxa in the fecal microbiota are representative of the taxa present throughout the gastrointestinal tract. To assess the stratification of microbes in the newborn gut and to evaluate the probable shortcoming of fecal sampling in place of tissue sampling, we simultaneously compared intestinal mucosa and fecal microbial communities in 15 neonates undergoing intestinal resections. We report three key results. First, when the site of fecal and mucosal samples are further apart, their microbial communities are more distinct, as indicated by low mean Sørensen similarity indices for each patient's fecal and tissue microbiota. Second, two distinct niches (intestinal mucosa and fecal microbiota) are evident by principal component analyses, demonstrating the critical role of sample source in defining microbial composition. Finally, in contrast to adult studies, intestinal bacterial diversity was higher in tissue than in fecal samples. This study represents an unprecedented map of the infant microbiota from intestinal mucosa and establishes discernable biogeography throughout the neonatal gastrointestinal tract. Our results question the reliance on fecal microbiota as a proxy for the developing intestinal microbiota. Additionally, the robust intestinal tissue-level bacterial diversity we detected at these early ages may contribute to the maturation of mucosal immunity. PMID:24637795

  19. Lipid biomarkers in Holocene and glacial sediments from ancient Lake Ohrid (Macedonia, Albania)

    NASA Astrophysics Data System (ADS)

    Holtvoeth, J.; Vogel, H.; Wagner, B.; Wolff, G. A.

    2010-11-01

    Organic matter preserved in Lake Ohrid sediments originates from aquatic and terrestrial sources. Its variable composition reflects climate-controlled changes in the lake basin's hydrology and related organic matter export, i.e. changes in primary productivity, terrestrial plant matter input and soil erosion. Here, we present first results from lipid biomarker investigations of Lake Ohrid sediments from two near-shore settings: site Lz1120 near the southern shore, with low-lying lands nearby and probably influenced by river discharge, and site Co1202 which is close to the steep eastern slopes. Variable proportions of terrestrial n-alkanoic acids and n-alkanols as well as compositional changes of ω-hydroxy acids document differences in soil organic matter supply between the sites and during different climate stages (glacial, Holocene, 8.2 ka cooling event). Changes in the vegetation cover are suggested by changes in the dominant chain length of terrestrial n-alkanols. Effective microbial degradation of labile organic matter and in situ contribution of organic matter derived from the microbes themselves are both evident in the sediments. We found evidence for anoxic conditions within the photic zone by detecting epicholestanol and tetrahymanol from sulphur-oxidising phototrophic bacteria and bacterivorous ciliates and for the influence of a settled human community from the occurrence of coprostanol, a biomarker for human and animal faeces (pigs, sheep, goats), in an early Holocene sample. This study illustrates the potential of lipid biomarkers for future environmental reconstructions using one of Europe's oldest continental climate archives, Lake Ohrid.

  20. Timing and magnitude of the Caribbean mid-Holocene highstand

    NASA Astrophysics Data System (ADS)

    Ashe, E.; Khan, N.; Horton, B.; Brocard, G. Y.; Dutton, A.; Engelhart, S. E.; Kopp, R. E.; Hill, D. F.; Peltier, W. R.; Scatena, F. N.

    2015-12-01

    We present a database of published and new relative sea-level (RSL) data for the past 13 ka, which constrains the Holocene sea-level histories of the Caribbean coast of Central and South America (Florida Keys, USA to Guyana) and the Bahamas and Greater and Lesser Antilles islands. Our evaluation of mangrove peat and Acropora palmata sea-level indicators from geological investigations provides 503 sea-level index points and 242 limiting dates. We subdivide the database into 21 regions based on the availability of data, tectonic setting, and distance from the former Laurentide ice sheet. Most index points (75%) and limiting dates (90%) are <8 ka, although there is an unusual temporal distribution with the greatest amount of the data (~28%) occurring between 6-8 ka. We reassess and screen radiocarbon and U/Th ages of mangrove peat and coral data. We use the stratigraphic position (overburden thickness) of index points account for sediment compaction, and use the paleotidal model of Hill et al. (2011) to account for Holocene changes in paleotidal range. A noisy-input Gaussian process regression model calculates that the rates of RSL change were highest during the early Holocene (3-8 mm/yr) and have decreased over time (< 2 mm/yr), which is related to the reduction of ice equivalent meltwater input and collapse of the proglacial forebulge during the Holocene. The sea-level reconstructions demonstrate that RSL did not exceed the present height (0 m) during the Holocene in the majority of locations, with the exception of a small highstand (<2 m) on the northern coast of South America along the Orinoco Delta and Suriname/Guyana located furthest away from the former Laurentide Ice Sheet. The different sea-level histories are an ongoing isostatic response to deglaciation of the Laurentide Ice Sheet and suggest subsidence resulting from collapse of the proglacial forebulge reaches further south than previously considered.

  1. Two Holocene paleofire records from Peten, Guatemala: Implications for natural fire regime and prehispanic Maya land use

    NASA Astrophysics Data System (ADS)

    Anderson, Lysanna; Wahl, David

    2016-03-01

    Although fire was arguably the primary tool used by the Maya to alter the landscape and extract resources, little attention has been paid to biomass burning in paleoenvironmental reconstructions from the Maya lowlands. Here we report two new well-dated, high-resolution records of biomass burning based on analysis of macroscopic fossil charcoal recovered from lacustrine sediment cores. The records extend from the early Holocene, through the full arc of Maya prehistory, the Colonial, and post-Colonial periods (~ 9000 cal yr BP to the present). (Hereafter BP) The study sites, Lago Paixban and Lago Puerto Arturo, are located in northern Peten, Guatemala. Results provide the first quantitative analysis from the region demonstrating that frequent fires have occurred in the closed canopy forests since at least the early Holocene (~ 9000 BP), prior to occupation by sedentary agriculturalists. Following the arrival of agriculture around 4600 BP, the system transitioned from climate controlled to anthropogenic control. During the Maya period, changes in fire regime are muted and do not appear to be driven by changes in climate conditions. Low charcoal influx and fire frequency in the Earliest Preclassic period suggest that land use strategies may have included intensive agriculture much earlier than previously thought. Preliminary results showing concentrations of soot/black-carbon during the middle and late Preclassic periods are lower than modern background values, providing intriguing implications regarding the efficiency of Maya fuel consumption.

  2. Integrated Geophysycal Prospecting in Late Antiquity and Early Medieval Sites in Italy

    NASA Astrophysics Data System (ADS)

    Giannotta, Maria Teresa; Leucci, Giovanni; De Giorgi, Lara; Matera, Loredana; Persico, Raffaele; Muci, Giuseppe

    2016-04-01

    In this contribution, the results of some integrated geophysical prospecting (magnetometric and GPR) are exposed. This work has been performed in collaboration between archaeologists and geophysicists within the research project "History and Global Archaeology of the Rural Landascapes in Italy, between Late Antiquity and Medieval period. Integrated systems of sources, methodologies, and technologies for a sustainable development", financed by the Italian Ministry for Instruction, University and Research MIUR. In particular, the archaeological sites of Badia and San Giovanni in Malcantone, both in the Apulia Region (eastern-southern Italy) have been prospect. The sites have been identified on the basis of available documents, archaeological surveys and testimonies. In particular, we know that in Badia [1] it was probable the presence of an ancient roman villa of the late ancient period (strongly damaged by the subsequent ploughing activities). Whereas in San Giovanni there is still, today, a small chapel (deconsecrated) that was likely to be part of a previous