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Sample records for holocene coastal dunefields

  1. Late Holocene dune mobilizations in the northwestern Negev dunefield, Israel: A response to combined anthropogenic activity and short-term intensified windiness

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Katra, Itzhak; Blumberg, Dan G.

    2013-04-01

    The study of the effects of past climates on ancient cultures is usually based on geologic records pertaining to rainfall and temperature fluctuations and shifts. This study proposes a paradigm of anthropogenic activity and windiness fluctuations to explain aeolian sedimentation and dune mobilization in the northwestern (NW) Negev Desert dunefield (Israel). The proposed paradigm contributes a different approach to estimating the effect of climate changes on the unprecedented agricultural and urban settlement expansion during the late Roman to Early Islamic period in the northern and central Negev Desert. This study builds upon the late Holocene cluster of luminescence ages of Roskin et al. (Age, origin and climatic controls on vegetated linear dunes in the northwestern Negev Desert (Israel), Quaternary Science Reviews 30 (2011), 1649-1674) coupled with analysis of archaeological finds and historical texts. We suggest that whereas the NW Negev dunefield was generally stable during the Holocene, intermittent dune mobilization during the late Holocene, at ~1.8 ka and mostly 1.4-1.1 ka (~600-900 CE), are linked to periods of human occupation. The idea that the last glacial dune encroachments alone that formed the NW Negev dunefield is connected to cold-event windy climates that may have intensified East Mediterranean cyclonic winter storms, cannot explain the late Holocene dune mobilizations. We conceptually model a connection between late Holocene dune mobilization, widespread anthropogenic occupation and activity, and windiness. We maintain that historic grazing and uprooting shrubs for fuel in the past by nomads and sedentary populations led to decimation of dune stabilizers, biogenic soil crusts and vegetation, causing dune erodibility and low-grade activity. Short-term events of amplified wind power in conjunction with periods of augmented anthropogenic activity that triggered major events of dune mobilization (elongation) and accretion have been preserved in the

  2. The Impact of Urbanization on the Regional Aeolian Dynamics of an Arid Coastal Dunefield

    NASA Astrophysics Data System (ADS)

    Smith, Alexander; Jackson, Derek; Cooper, Andrew

    2016-04-01

    The anthropogenic impact on the geomorphology of many landscapes are inextricably connected but are often neglected due to the difficulty in making a direct link between the quasi natural and human processes that impact the environment. This research focuses on the Maspalomas dunefield, located on the southern coast of Gran Canaria, in the Canary Island Archipelago. The tourism industry in Maspalomas has led to intensive urbanization since the early 1960's over an elevated alluvial terrace that extends into the dunefield. Urbanization has had a substantial impact on both the regional airflow conditions and the geomorphological development of this transverse dune system. As a result airflow and sediment has been redirected in response to the large scale construction efforts. In situ data was collected during field campaigns using high resolution three-dimensional anemometry to identify the various modifications within the dunefield relative to incipient regional airflow conditions. The goal is to analyse the flow conditions near the urbanized terrace in relation to areas that are located away from the influence of the buildings and to verify numerical modelling results. Computational Fluid Dynamics (CFD) modelling is used in order to expand the areal extent of analysis by providing an understanding of relevant flow dynamics (e.g. flow velocity, directionality, turbulence, shear stresses, etc.) at the mesoscale. An integrative three dimensional model for CFD simulations was created to address the impact of both the urban area (i.e. hotels, commercial centers, and residential communities) as well as the dune terrain on regional flow conditions. Early modelling results show that there is significant flow modification around the urban terrace with streamline compression, acceleration, and deflection of flow on the windward side of the development. Consequently downwind of the terrace there is an area of highly turbulent flow conditions and well developed separation and

  3. Characterization of the Soil Hydromorphic Conditions in a Paludified Dunefield during the Mid-Holocene Hemlock Decline near Québec City, Québec

    NASA Astrophysics Data System (ADS)

    Bhiry, Najat; Filion, Louise

    1996-11-01

    The mid-Holocene eastern hemlock [ Tsuga canadensisL. (Carr.)] decline has been recently attributed to the activity of insect defoliators. N. Bihiry and L. Filion, Quaternary Research45,312-320 (1996). In this study, soil hydromorphic conditions were investigated for the period 6800-3200 yr B.P. using micromorphological data from a peat section from a swale in a paludified dunefield in southern Québec. After a short period of plant colonization in shallow pools between 6800 and 6400 yr B.P., mesic conditions predominated in the interdune before the decline (6400-4900 yr B.P.), as evidenced by strong bioturbation and abundance of excrements from the soil fauna. During the decline, a shift from mesic to wet conditions occurred (4900-4100 yr B.P.), although xeric to mesic conditions persisted on dune ridges until at least 4200 yr B.P. Wetness culminated when beaver occupied the site (4100-3750 yr B.P.). Hemlock needles with chewing damage typical of hemlock looper ( Lambdina fiscellaria) feeding were identified at levels dated 4900, 4600, and 4200 yr B.P., respectively, implying that the hemlock decline was associated with at least three defoliation events. The ca. 400-yr interval between these events likely represents the time required for this late-sucessional tree species to recover.

  4. Holocene coastal paleoenvironmental record, Bay of Brest

    NASA Astrophysics Data System (ADS)

    Fernane, Assia; Gandouin, Emmanuel; Goslin, Jérôme; Penaud, Aurélie; Van Vliet lanoë, Brigitte

    2013-04-01

    Coastal areas are sensitive environments regarding the risk of submersion and the impact on biodiversity induced by salinity changes. These areas thus provide good palaeocecological archives to monitor palaeo sea level changes and the associated adaptation of different biological communities. The north-western coast of France has poorly been investigated regarding its Holocene palaeoecological signatures (Morzadec-Kerfourn, 1974; Naughton et al., 2007). Chironomids have been recognized to be an efficient tool for palaeoclimate and palaeosalinity reconstructions in lakes (Brooks, 2006), and more recently in river floodplains (Gandouin et al, 2006). In this study, environmental changes related to both climate processes and human disturbances, were reconstructed over the last 5000 years, based on pollen and chironomid assemblages from two coastal cores retrieved at Pors Milin (Brittany, NW France). The sedimentary sequences consist of terrestrial peaty layers interdigited with marine clastic deposits. The study area is composed by a sandy beach, truncating the peat, limited by a high sandy bar, and a back marsh developed at + 4 m NGF. Pollen and chironomid results reveal that anthropogenic factors would mainly control environmental changes that occurred in this sector. The disappearance of many chironomid taxa (inhabitants of main river channel) and the dramatic fall in diversity may have been induced by the development of the Merovingian forest clearance at Pors Milin. Indeed, we suggest that the development of agriculture, the river embankment and the draining of wetlands may explain the chironomid habitat loss and the subsequent fall of biodiversity. This change in faunal assemblages occurred synchronously with a decrease in the "arborean / non arborean" pollen ratio reflecting the land opening of the watershed. Several nitrophilous and anthropogenic pollen taxa reinforce our hypothesis concerning the development of agricultural and livestock farming activities at

  5. Holocene climate change evidence from high-resolution loess/paleosol records and the linkage to fire-climate change-human activities in the Horqin dunefield in northern China

    NASA Astrophysics Data System (ADS)

    Mu, Yan; Qin, Xiaoguang; Zhang, Lei; Xu, Bing

    2016-05-01

    The combination of high-resolution sedimentary paleoclimate proxies of total organic carbon and magnetic susceptibility of a loess/paleosol section with black carbon (BC) records provides us with information about climate change and the linkage of fire-climate change-vegetation-human activities in the Horqin dunefield over the past 11,600 cal yr BP. We found that during 11,600-8000 cal yr BP (the early Holocene), the area was dominated by a dry climate. The vegetation coverage was low, which limited the extent of fire. The Holocene optimum can be placed between 8000 and 3200 cal yr BP, and during this period, anthropogenic fire was a key component of total fire occurrence as the intensity of human activity increased. The development of agricultural activities and the growing population during this period increased the use of fire for cooking food and burning for cultivation and land fertilization purposes. During 2800-2600 cal yr BP, a warm/moister climate prevailed and was associated with a high degree of pedogenesis and vegetation cover density, evident at 2700 cal yr BP. Fires may have contributed to human survival by enabling the cooking of food in the warm and wet climate. In the period since 2000 cal yr BP, fires linked to agriculture may have led to increased biomass burning associated with agricultural activity.

  6. Holocene Antarctic's coastal environment, ice sheet, and sea levels explored

    NASA Astrophysics Data System (ADS)

    Goodwin, I.; Berkman, P.; Hjort, C.; Hirakawa, K.

    Efforts are in the works to resolve a several-decade-long debate over the size and extent of the Antarctic ice sheet and its role in sea levels during the last glacial cycle. Researchers also want to find out more about the nature of environmental changes around the Antarctic coast throughout the Holocene, the sensitivity of the ice sheet to warm periods, and the significance of pre-Holocene marine fossils there.Scientists concerned with these issues presented their research priorities last fall at an Antarctic ice margin evolution (ANTIME) workshop, “Circum-Antarctic Coastal Environmental Variability and Sea Level History During the Late Quaternary.” These workshop participants included coastal and glacial geomorphologists, geochemists, and paleoecologists.

  7. Holocene formation and evolution of coastal dunes ridges, Brittany (France)

    NASA Astrophysics Data System (ADS)

    Van Vliet-Lanoë, Brigitte; Goslin, Jérôme; Hénaff, Alain; Hallégouët, Bernard; Delacourt, Christophe; Le Cornec, Erwan; Meurisse-Fort, Murielle

    2016-07-01

    Holocene coastal dune formation under a continuously rising sea level (SL) is an abnormal response to increasing storm frequency. The aim of this work is to understand the coastal sedimentary budget and the present-day sand starvation, controlled by climate and man. Dating in Brittany shows that Aeolian deposition initiated from ca. 4000 cal BP, with the slowing down of the SL rise. Pre-historical dunes appeared here from ca. 3000 cal BP, without SL regression. After, further building phases recycled the same stock of sands. Historical dunes I developed from ca. 350 AD. Major storms between 900 and 1200 AD resulted in the construction of washover coastal ridges, the Historical dunes II. A part of the sand was evacuated offshore. From ca. 1350 AD, the pre-existing ridges are reworked forming the Historical dunes III, leading to rapid coastal erosion and inland drift. Holocene dunes with a rising SL constitute a temporary anomaly, mostly forced by man, soon erased by storms in Brittany.

  8. Regional flow in the Baltic Shield during Holocene coastal regression

    USGS Publications Warehouse

    Voss, Clifford I.; Andersson, Johan

    1993-01-01

    The occurrence of saline waters in the Baltic Shield in Sweden is consistent with ongoing but incomplete Holocene flushing and depends on the geometry and connectivity of conductive structures at both regional and local scales, and on the surface topography. Numerical simulation of regional variable-density fluid flow during Holocene land-rise and coastal regression shows that the existence of any old saline water, whether derived from submarine recharge in regions below Sweden's highest postglacial coastline or geochemical processes in the crystalline rock, is an indication either of slow fluid movements through the bedrock over long times, or of long travel distances through fracture systems before arriving at measurement points. During the land-rise period, regional flow is not affected by the variable density of fluids in the upper few kilometers of the shield, and the topography of the water table is the only driving force. The spatial distribution of meteoric flushing water and pre-Holocene waters may be complex, with the possibility of relatively fresh water in fracture zones below salty units even at depths of a few kilometers. The domination of the topographic driving force implies that deep saline water is not necessarily stagnant, and significant flow may be expected to occur in well-connected horizons even at depth. Local topography variation and fracture zone location combine to create a complex flow field in which local topographic driving forces extend to considerable depth in some areas, whereas regional topographic forces predominate in others. Thus, a pattern may be difficult to discern in measurements of the regional salinity distribution, although it is clear that the coastal region is the major zone of discharge for deeper pre-Holocene fluids. During the land-rise period, the regional flow field equilibrates with changing climatic conditions and coastal positions, while the distribution of flushing water and older water lags and will

  9. Mars: Morphology of Southern Hemisphere intracrater dunefields

    NASA Technical Reports Server (NTRS)

    Lancaster, N.; Greeley, R.

    1987-01-01

    Viking Orbiter images of intracrater dunefields in the Noachis Terra region were examined in order to study the morphology of these landforms and to assess their relationship to local geological settings. The sizes of the dunefields range from 40 to 3600 sq km and vary directly with crater size. Preliminary studies reveal dunefields of two varieties. The most common type is composed of massed straight to slightly wavy crescentic dunes similar to those described by Breed. Dunefields of this type occupy more than 20% of the area of the crater floor, with the dunefield margins often marked by a large dune wall or rampart. Dune spacing ranges between 0.7 and 1.2 km. The second type of dune accumulation consists of clusters of large, widely spaced straight or curved ridges, which often intersect to create rectilinear patterns. Dunes are typically spaced 1.6 to 4 km apart. Earth terrestrial analogs for these dunes are discussed.

  10. Middle to late Holocene coastal evolution along the south coast of Upolu Island, Samoa

    USGS Publications Warehouse

    Goodwin, I.D.; Grossman, E.E.

    2003-01-01

    Stratigraphic surveys and sedimentological analyses of coastal sediments and reef cores along the south coast of Upolu Island, Samoa, reveal that during the middle Holocene this coast was characterised by barrier spits, open lagoons, and estuaries. These estuarine systems matured during the late Holocene, with progressive sedimentation and inlet closure, leading to the dominance of mangrove swamps in the past 1000 years. Contemporaneous with the transition of open estuaries to mangrove swamps was the aggradation and progradation of coastal plains. The coastal progradation since 700-1000 years BP is best explained by increased sediment availability and reduced incident wave energy at the shore resulting from the shallowing and subsequent cessation of reef crest accretion following the mid-Holocene sea-level highstand ca. ???4500 yr BP. A small relative sea-level (RSL) lowering since 700-1000 years may have contributed to the positive sediment budget. This study highlights the need for island-wide coastal surveys to assess the relative roles of RSL, sediment budgets, and hydrodynamics on coastal evolution and stability. Differences in coastal evolution around Upolu Island may also be influenced by differential tectonic movements associated with late Holocene volcanism, coseismicity, and/ or submarine landslides. ?? 2003 Elsevier B.V. All rights reserved.

  11. 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.

  12. A Holocene pollen record of vegetation and coastal environmental changes in the coastal swamp forest at Batulicin, South Kalimantan, Indonesia

    NASA Astrophysics Data System (ADS)

    Yulianto, Eko; Rahardjo, A. T.; Noeradi, Dardji; Siregar, D. A.; Hirakawa, K.

    2005-04-01

    Pollen analysis of a coastal peat swamp core representing 9100 BP from Batulicin, South Kalimantan, Indonesia, shows that mangrove forest, with Rhizophora as its main element has been established since the early Holocene. Vegetation development in general, and particularly mangrove forest, was influenced by Holocene environmental changes. The highest value of Rhizophora at ca. 8200 BP indicates an early Holocene sea level drop and implies sea level at ca. -9 m. Subsequently mangrove forest was severely disrupted by rapid sea level rise at ca. 6400 BP prior to the Holocene Maximum. However, it quickly recovered following a lower rate of sea level rise or subsequent sea level drop at ca. 6000 BP and flourished until ca. 1000 BP. From ca. 6000 BP, the environmental setting around the site seems to have gradually become more terrestrial and changed from mangrove forest to peat swamp forest due to higher precipitation and intensive progradation. Human influence is recognized from ca. 1600 BP.

  13. A new GIS approach for reconstructing and mapping dynamic late Holocene coastal plain palaeogeography

    NASA Astrophysics Data System (ADS)

    Pierik, H. J.; Cohen, K. M.; Stouthamer, E.

    2016-10-01

    The geomorphological development of Holocene coastal plains around the world has been studied since the beginning of the twentieth century from various disciplines, resulting in large amounts of data. However, the overwhelming quantities and heterogeneous nature of this data have caused the divided knowledge to remain inconsistent and fragmented. To keep improving the understanding of coastal plain geomorphology and geology, cataloguing of data and integration of knowledge are essential. In this paper we present a GIS that incorporates the accumulated data of the Netherlands' coastal plain and functions as a storage and integration tool for coastal plain mapped data. The GIS stores redigitised architectural elements (beach barriers, tidal channels, intertidal flats, supratidal flats, and coastal fresh water peat) from earlier mappings in separate map layers. A coupled catalogue-style database stores the dating information of these elements, besides references to source studies and annotations regarding changed insights. Using scripts, the system automatically establishes palaeogeographical maps for any chosen moment, combining the above mapping and dating information. In our approach, we strip the information to architectural element level, and we separate mapping from dating information, serving the automatic generation of time slice maps. It enables a workflow in which the maker can iteratively regenerate maps, which speeds up fine-tuning and thus the quality of palaeogeographical reconstruction. The GIS currently covers the late Holocene coastal plain development of the Netherlands. This period witnessed widespread renewed flooding along the southern North Sea coast, coinciding with large-scale reclamation and human occupation. Our GIS method is generic and can be expanded and adapted to allow faster integrated processing of growing amounts of data for many coastal areas and other large urbanising lowlands around the world. It allows maintaining actual data

  14. Reconstruction of Redox Conditions and Productivity in Coastal Waters of the Bothnian Sea during the Holocene

    NASA Astrophysics Data System (ADS)

    Dijkstra, N.; Quintana Krupinski, N. B.; Slomp, C. P.

    2014-12-01

    Hypoxia is a growing problem in coastal waters worldwide, and is a well-known cause of benthic mortality. The semi-enclosed Baltic Sea is currently the world's largest human-induced dead zone. During the early Holocene, it experienced several periods of natural hypoxia following the intrusion of seawater into the previous freshwater lake. Recent studies suggest that at that time, the hypoxia expanded north to include the deep basin of the Bothnian Sea. In this study, we assess whether the coastal zone of the Bothnian Sea was also hypoxic during the early Holocene. We analysed a unique sediment record (0 - 30 mbsf) from the Ångermanälven estuary, which was retrieved during the International Ocean Discovery Programme (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. Using geochemical proxies and foraminifera abundances, we reconstruct the changes in redox conditions, salinity and productivity in the estuary. Our preliminary results suggest that bottom waters in this coastal basin became anoxic upon the intrusion of brackish seawater in the early Holocene and that the productivity was elevated. The presence of benthic foraminifera in this estuary during the mid-Holocene suggests more saline conditions in the Bothnian Sea than today. Due to isostatic uplift, the estuary likely gradually became more isolated from the Bothnian Sea, which itself became more isolated from the Baltic Sea. Both factors likely explain the subsequent re-oxygenation of bottom waters and gradual refreshening of the estuary as recorded in the sediments. Interestingly, the upper meters of sediment are enriched in minerals that contain iron, phosphorus and manganese. We postulate that the refreshening of the estuary triggered the formation of these minerals, thereby increasing the phosphorus retention in these sediments and further reducing primary productivity. This enhanced retention linked to refreshening may contribute to the current oligotrophic conditions in the Bothnian Sea.

  15. The archaeological record and mid-Holocene marginal coastal palaeoenvironments around Liverpool Bay

    NASA Astrophysics Data System (ADS)

    Huddart, David; Gonzalez, Silvia; Roberts, Gordon

    1999-10-01

    The available published and unpublished archaeological record (human and animal bones, artefacts, footprints) is collated and reviewed in relation to the stratigraphic succession and palaeoecology for Mid-Holocene marginal coastal environments around Liverpool Bay. Two stratigraphic levels with human and animal footprint trails are described from Formby Point and whilst the upper level was formed between c 4000-3600 years B.P. (during the later Neolithic-early Bronze Age), the lower level is older. The animal and bone assemblages and the archaeological artefact evidence for this coastal region are reviewed. The implications of these finds for inter-tidal zone archaeology for this region are assessed but it appears that there is no evidence for major Mesolithic coastal human or animal activity, except for the North Wales coast, although there are major concentrations of Neolithic animal, human and artefacts remains. During the Bronze to Iron Age dunes were present and probably grazed. Metal artefacts have been located from several sites but there is a lack of associated pottery evidence throughout the Holocene. This may mean that settlements were inland and coastal areas were only visited for grazing, hunting and fishing.

  16. Holocene coastal dune fields used as indicators of net littoral transport: West Coast, USA

    NASA Astrophysics Data System (ADS)

    Peterson, Curt D.; Stock, Errol; Hart, Roger; Percy, David; Hostetler, Steve W.; Knott, Jeffrey R.

    2010-03-01

    Between Point Grenville, Washington, and Point Conception, California (1500 km distance) 21 dune fields record longshore transport in 20 littoral cells during the late Holocene. The direction of predominant littoral transport is established by relative positions of dune fields (north, central, or south) in 17 representative littoral cells. Dune field position is north of cell midpoints in northernmost Oregon and Washington, but is south of cell midpoints in southern Oregon and California. Downdrift sand trapping occurs at significant changes in shoreline angle and/or at bounding headlands that project at least 2.5 km seaward from the general coastal trend. Sand bypassing occurs around small headlands of less than 0.5 km in projection distance. A northward shift of the winter low-pressure center in the northeast Pacific Ocean is modeled from 11 ka to 0 ka. Nearshore current forcing in southern Oregon and northern California switched from northward in earliest Holocene time to southward in late Holocene time. The late Holocene (5-0 ka) is generally characterized by net northward littoral drift in northernmost Oregon and Washington and by net southward littoral drift in southernmost Oregon and California. A regional divergence of net transport direction in central Oregon, i.e. no net drift, is consistent with modeled wind and wave forcing at the present time (0 ka).

  17. Late Holocene sedimentation in a high Arctic coastal setting: Simpson Lagoon and Colville Delta, Alaska

    NASA Astrophysics Data System (ADS)

    Hanna, Andrea J. M.; Allison, Mead A.; Bianchi, Thomas S.; Marcantonio, Franco; Goff, John A.

    2014-02-01

    Arctic coastal environments near major river outfalls, like Simpson Lagoon, Alaska and the adjacent Colville River Delta, potentially contain high-resolution sediment records useful in elucidating late Holocene Arctic sediment transport pathways and coupled terrestrial-ocean evidence of paleoclimate variability. This study utilizes a multi-tracer geochronology approach (137Cs, 239,240Pu, and 14C) tailored for high-latitude environments to determine the age models for cores collected from Simpson Lagoon, and to date seismic boundaries in shallow acoustic reflection data (CHIRP) to examine late Holocene infill patterns. Modern (~100 y) sediment accumulation rates range from <0.02 to 0.46±0.04 cm y-1, with a primary depocenter in western Simpson Lagoon adjacent to the Colville Delta and a secondary depocenter in eastern Simpson Lagoon. CHIRP reflectors, age-constrained by 14C analysis, reveal rapid late Holocene (0-3500 y BP) transgression consistent with high modern shoreline retreat rates. The western depocenter contains >5 m of late Holocene interbedded sediments, likely derived primarily from the Colville River, with onset of accumulation occurring prior to ~3500 y BP. A paleo-high in central Simpson Lagoon, separating the two depocenters, was subaerially exposed prior to ~600 y BP. The millimeters-per-year sedimentation rates across the lagoon, coupled with the undisturbed, interbedded sediment record, indicate that these settings hold great potential to develop new Arctic paleoenvironmental records.

  18. Holocene coastal dune fields used as indicators of net littoral transport: West Coast, USA

    USGS Publications Warehouse

    Peterson, C.D.; Stock, E.; Hart, R.; Percy, D.; Hostetler, S.W.; Knott, J.R.

    2010-01-01

    Between Point Grenville, Washington, and Point Conception, California (1500 km distance) 21 dune fields record longshore transport in 20 littoral cells during the late Holocene. The direction of predominant littoral transport is established by relative positions of dune fields (north, central, or south) in 17 representative littoral cells. Dune field position is north of cell midpoints in northernmost Oregon and Washington, but is south of cell midpoints in southern Oregon and California. Downdrift sand trapping occurs at significant changes in shoreline angle and/or at bounding headlands that project at least 2.5 km seaward from the general coastal trend. Sand bypassing occurs around small headlands of less than 0.5 km in projection distance. A northward shift of the winter low-pressure center in the northeast Pacific Ocean is modeled from 11 ka to 0 ka. Nearshore current forcing in southern Oregon and northern California switched from northward in earliest Holocene time to southward in late Holocene time. The late Holocene (5-0 ka) is generally characterized by net northward littoral drift in northernmost Oregon and Washington and by net southward littoral drift in southernmost Oregon and California. A regional divergence of net transport direction in central Oregon, i.e. no net drift, is consistent with modeled wind and wave forcing at the present time (0 ka). ?? 2009 Elsevier B.V.

  19. Long-Term Resilience of Late Holocene Coastal Subsistence System in Southeastern South America

    PubMed Central

    Colonese, André Carlo; Collins, Matthew; Lucquin, Alexandre; Eustace, Michael; Hancock, Y.; de Almeida Rocha Ponzoni, Raquel; Mora, Alice; Smith, Colin; DeBlasis, Paulo; Figuti, Levy; Wesolowski, Veronica; Plens, Claudia Regina; Eggers, Sabine; de Farias, Deisi Scunderlick Eloy; Gledhill, Andy; Craig, Oliver Edward

    2014-01-01

    Isotopic and molecular analysis on human, fauna and pottery remains can provide valuable new insights into the diets and subsistence practices of prehistoric populations. These are crucial to elucidate the resilience of social-ecological systems to cultural and environmental change. Bulk collagen carbon and nitrogen isotopic analysis of 82 human individuals from mid to late Holocene Brazilian archaeological sites (∼6,700 to ∼1,000 cal BP) reveal an adequate protein incorporation and, on the coast, the continuation in subsistence strategies based on the exploitation of aquatic resources despite the introduction of pottery and domesticated plant foods. These results are supported by carbon isotope analysis of single amino acid extracted from bone collagen. Chemical and isotopic analysis also shows that pottery technology was used to process marine foods and therefore assimilated into the existing subsistence strategy. Our multidisciplinary results demonstrate the resilient character of the coastal economy to cultural change during the late Holocene in southern Brazil. PMID:24718458

  20. Long-term resilience of late holocene coastal subsistence system in Southeastern South america.

    PubMed

    Colonese, André Carlo; Collins, Matthew; Lucquin, Alexandre; Eustace, Michael; Hancock, Y; de Almeida Rocha Ponzoni, Raquel; Mora, Alice; Smith, Colin; Deblasis, Paulo; Figuti, Levy; Wesolowski, Veronica; Plens, Claudia Regina; Eggers, Sabine; de Farias, Deisi Scunderlick Eloy; Gledhill, Andy; Craig, Oliver Edward

    2014-01-01

    Isotopic and molecular analysis on human, fauna and pottery remains can provide valuable new insights into the diets and subsistence practices of prehistoric populations. These are crucial to elucidate the resilience of social-ecological systems to cultural and environmental change. Bulk collagen carbon and nitrogen isotopic analysis of 82 human individuals from mid to late Holocene Brazilian archaeological sites (∼6,700 to ∼1,000 cal BP) reveal an adequate protein incorporation and, on the coast, the continuation in subsistence strategies based on the exploitation of aquatic resources despite the introduction of pottery and domesticated plant foods. These results are supported by carbon isotope analysis of single amino acid extracted from bone collagen. Chemical and isotopic analysis also shows that pottery technology was used to process marine foods and therefore assimilated into the existing subsistence strategy. Our multidisciplinary results demonstrate the resilient character of the coastal economy to cultural change during the late Holocene in southern Brazil.

  1. Holocene melt-water variations recorded in Antarctic coastal marine benthic assemblages

    SciTech Connect

    Berkman, P.A.

    1992-03-01

    Climate changes can influence the input of meltwater from the polar ice sheets. In Antarctica, signatures of meltwater input during the Holocene may be recorded in the benthic fossils which exist at similar altitudes above sea level in emerged beaches around the continent Interpreting the fossils as meltwater proxy records would be enhanced by understanding the modern ecology of the species in adjacent marine environments. Characteristics of an extant scallop assemblage in West McMurdo Sound, Antarctica, have been evaluated across a summer meltwater gradient to provide examples of meltwater records that may be contained in proximal scallop fossils. Integrating environmental proxies from coastal benthic assemblages around Antarctica, over ecological and geological time scales, is a necessary step in evaluating the marginal responses of the ice sheets to climate changes during the Holocene.

  2. Alimini Lakes Project (PAL). Human-environment interaction during the Holocene in Mediterranean coastal wetlands

    NASA Astrophysics Data System (ADS)

    Balbo, Andrea; Primavera, Milena; Fiorentino, Girolamo; Simone, Oronzo; Caldara, Massimo; Quarta, Gianluca; Calcagnile, Lucio

    2010-05-01

    A diachronical understanding of the co-evolution of people and Mediterranean wetlands requires the combined study of archaeological and palaeoenvironmental records. By focusing on an extended chronology, and relying on the update of known and new archaeological and palaeonvironmental sequences, PAL investigates how the Alimini Lakes disctrict (Apulia, S Italy) has changed over the past 10ka (the Holocene), a period witnessing great climatic environmental and social change. Holocene climate change is amplified in coastal wetlands, greatly affecting hydrology vegetation and people. Likewise, socio-economical changes (e.g. the introduction of agriculture) play a fundamental role in the shaping of wet landscapes. Under the combined action of environmental and human factors, coastal wetlands are prone to rapid and drastic ecological shifts and constitute ideal locations for developing a geoarchaeological approach. The results of the first year of research are presented here and include (1) the visit, description and GPS positioning of previously and newly discovered archaeological areas (cave and open air sites), (2) sampling of two Holocene sedimentary sequences from the Alimini Lakes disctict, (3) the results of the preliminary analyses (including AMS radiocarbon dating) carried out on the samples. The relocation of new and previously found archaeological sites was necessary to overcome some confusions caused by the contrasting published information. Relocated archaeological sites were normalized in a GIS environment. Two main Pleistocene/Holocene palaeoenvironmental sequences were sampled within the Alimini Lakes district: (1) the Frassanito dune reference sequence, obtained from a portion of the coastal dune (up to 10 m high) bordering the trait of the Adriatic coast situated in front of the Alimini lakes, (2) the ALI G 1 core (9m long) sampled on the W shore of Alimini Grande Lake. The multiproxy study of these sedimentary sequences provides a record of Holocene

  3. Sudden, probably coseismic submergence of Holocene trees and grass in coastal Washington State

    USGS Publications Warehouse

    Atwater, B.F.; Yamaguchi, D.K.

    1991-01-01

    Growth-position plant fossils in coastal Washington State imply a suddenness of Holocene submergence that is better explained by coseismic lowering of the land than by decade- or century-long rise of the sea. Growth-position fossils implying sudden submergence include the stems and leaves of salt-marsh grass entombed in tide-flat mud close to 300 yr ago and roughly 1700 and 3100 yr ago. In some places the stems and leaves close to 300 yr old are surrounded by sand left by an extraordinary, landward-directed surge - probably a tsunami from a great thrust earthquake on the Cascadia subduction zone. -from Authors

  4. Quantifying Holocene Coastal Retreat From River Morphology in Southern England and Wales

    NASA Astrophysics Data System (ADS)

    Attal, M.; Mudd, S. M.; Hurst, M. D.; Crickmore, B. A.

    2013-12-01

    Southern England and Wales have been undergoing subsidence since the end of the Last Glacial Maximum, with average rates varying between 0.5 and 1.2 mm/yr over the last 10 ka (Shennan and Horton, 2002). Rivers typically respond to subsidence by aggrading (e.g., Ishihara et al., 2012), yet many English and Welsh rivers incise into bedrock at their outlet and exhibit river profiles convexities typical of systems experiencing a drop in base level (e.g., Snyder et al., 2002; Attal et al., 2011). Scientists have proposed that coastal erosion could result in such river morphology (Snyder et al., 2002; Leyland & Darby, 2008, 2009). We combine modelling with topographic analysis of a series of basins along the coast of Southern England and Wales to test whether coastal erosion could explain the occurrence of rivers incising into bedrock at the coast. We further assess whether the distribution of such rivers and the shape of river profiles could be used to constrain amounts of coastal erosion during the Holocene. Within zones characterized by similar lithologies and coastal exposure (i.e. the orientation of the coast and the type of water body it faces), we find that rivers with the smallest basins incise into bedrock at their mouth while rivers with the largest basins experience aggradation. The transition between these two types of basins occurs at a consistent basin size. This signal conforms to model predictions, assuming that the slope of rivers at the coast decreases with increasing basin size. Whereas rivers in basins comprising igneous and/or metamorphic rocks tend to be steeper than rivers flowing on sedimentary bedrock, we find that the critical drainage area does not vary significantly with varying lithology, suggesting that other factors such as spatial variations in coastal retreat exert a stronger control on the spatial distribution of the two types of rivers throughout the study area. Reconstruction of river profiles prior to base level rise allows estimates

  5. Holocene Coastal Environments near Pompeii before the A.D. 79 Eruption of Mount Vesuvius, Italy

    NASA Astrophysics Data System (ADS)

    Pescatore, Tullio; Senatore, Maria Rosaria; Capretto, Giovanna; Lerro, Gaia

    2001-01-01

    Studies of some 70 bore holes around ancient Pompeii, on the southwestern slope of the Somma-Vesuvius volcano, allow the reconstruction of Holocene environments earlier than the A.D. 79 eruption. This eruption produced about 10 km3 of pyroclastic material that buried the Roman cities of Pompeii, Herculaneum, and Stabiae and promoted a shoreline progradation of 1 km. The Sarno coastal plain, in a post-Miocene sedimentary basin, has been affected by Somma-Vesuvius volcanic activity since the late Pleistocene. At the Holocene transgressive maximum, the sea reached an area east of ancient Pompeii and formed a beach ridge (Messigno, 5600 and 4500 14C yr B.P.) more than 2 km inland from the present shore. Progradation of the plain due to high volcanic supply during the following highstand resulted in a new beach ridge (Bottaro-Pioppaino, 3600 14C yr B.P.) 0.5 km seaward of the Messigno ridge. Ancient Pompeii was built as the shoreline continued to prograde toward its present position. Deposits of the A.D. 79 eruption blanketed the natural levees of the Sarno River, marshes near the city and on the Sarno's floodplain, the morphological highs of Messigno and Bottaro-Pioppaino beach ridges, and the seashore. That shore was probably 1 km landward of the present one.

  6. Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction

    PubMed Central

    Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A.; Leorri, Eduardo

    2016-01-01

    The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches. PMID:27929122

  7. Holocene coastal morphologies and shoreline reconstruction for the southwestern coast of the Bohai Sea, China

    NASA Astrophysics Data System (ADS)

    Liu, Yanxia; Huang, Haijun; Qi, Yali; Liu, Xiao; Yang, Xiguang

    2016-09-01

    Ground-penetrating radar (GPR) reflection profiles were interpreted and combined with sedimentological data to highlight the morpho-evolutionary history of the southwestern sector of the Bohai Sea. The internal structures in GPR images obtained near the Holocene maximum transgression boundary revealed concave-upward and onlap types of transgressive paleo-topography. The relationship between historical courses of the Yellow River and the distribution of shell ridges at three periods (6 ka, 2 ka, and recent times) showed that the concave-upward types derived from the marine sediments overlap the fluvial sediments, and the onlap types from the marine sediments cover the coastal lagoon sediments. Based on the above paleo-geographical setting, previous sea-level markers were corrected, taking into account uncertainties of their relationship to former water levels. The rates of vertical tectonic displacement, evaluated through comparison of the relative sea level (RSL) data from the GPR images and the Holocene predicted sea-level elevation, markedly affected RSL changes. The fitted RSL curves from the corrected sea-level indicators showed that the accuracy of former sea-level determinations can be improved by comparing with the maximum transgressive position of GPR detection. A topographic digital elevation model (DEM) for 6 ka is reconstructed based on the corrected data.

  8. Late Holocene sedimentation in coastal areas of the northwestern Ross Sea (Antarctica)

    NASA Astrophysics Data System (ADS)

    Colizza, Ester; Finocchiaro, Furio; Kuhn, Gerhard; Langone, Leonardo; Melis, Romana; Mezgec, Karin; Severi, Mirko; Traversi, Rita; Udisti, Roberto; Stenni, Barbara; Braida, Martina

    2013-04-01

    Sediment cores and box cores collected in two coastal areas of the northwestern Ross Sea (Antarctica) highlight the possibility of studying the Late Holocene period in detail. In this work we propose a study on two box cores and two gravity cores collected in the Cape Hallett and Wood Bay areas during the 2005 PNRA oceanographic cruise. The two sites are feed by Eastern Antarctic Ice Shelf (EAIS) and previous studies have highlighted a complex postglacial sedimentary sequence, also influenced by local morphology. This study is performed within the framework of the PNRA-ESF PolarCLIMATE HOLOCLIP (Holocene climate variability at high-southern latitudes: an integrated perspective) Project. The data set includes: magnetic susceptibility, X-ray analyses, 210Pb, 14C dating, diatoms and foraminifera assemblages, organic carbon, and grain-size analyses. Furthermore XRF core scanner analyses, colour analysis from digital images, and major, minor and trace element concentration analyses (ICP-AES) are performed. Data show that the box core and upper core sediments represent a very recent sedimentation in which it is possible to observe the parameter variability probably linked to climate variability/changes: these variation will be compared with isotopic record form ice cores collected form the same Antarctic sector.

  9. Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction

    NASA Astrophysics Data System (ADS)

    Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A.; Leorri, Eduardo

    2016-12-01

    The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches.

  10. Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction.

    PubMed

    Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A; Leorri, Eduardo

    2016-12-08

    The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches.

  11. Holocene development of the eastern Gulf of Finland coastal zone (Baltic Sea)

    NASA Astrophysics Data System (ADS)

    Ryabchuk, Daria; Sergeev, Alexander; Gusentsova, Tatiana; Gerasimov, Dmitry; Zhamoida, Vladimir; Amantov, Aleksey; Kulkova, Marianna; Sorokin, Peter

    2014-05-01

    In 2011-2013 geoarcheological and marine geological research of the eastern Gulf of Finland coasts and near-shore bottom were undertaken. Researches were concentrated within several key-areas (Sestroretskaya Lowland, Narva-Luga Klint Bay and southern coastal zone of the Gulf (near Bolshaya Izhora village). Study areas can provide important information about Gulf of Finland Holocene coastal development as since Ancylus time (about 10000 cal.BP). Development of numerous sand accretion forms (spits, bars, dunes) of different shape, age and genesis caused formation of lagoon systems, situated now on-land due to land uplift. Coasts of lagoons in Sestroretskaya Lowland and Narva-Luga Klint Bay were inhabited by Neolithic and Early Metal people. Analysis of coastal morphology and results of geological research (GIS relief analyses, ground penetrating radar, drilling, grain-size analyses, radiocarbon dating) and geoarcheological studies allowed to reconstruct the mechanism of large accretion bodies (bars and spits) and lagoon systems formation during last 8000 years. Geoarcheological studies carried out within eastern Gulf of Finland coasts permitted to find some features of the Neolithic - Early Metal settlements distribution. Another important features of the eastern Gulf of Finland coastal zone relief are the series of submarine terraces found in the Gulf bottom (sea water depths 10 to 2 m). Analyses of the submarine terraces morphology and geology (e.g. grain-size distribution, pollen analyses and organic matter dating) allow to suppose that several times during Holocene (including preAncylus (11000 cal.BP) and preLittorina (8500 cal.BP) regressions) the sea-water level was lower than nowadays. During the maximal stage of the Littorina transgression (7600-7200 cal. BP) several open bays connected with the Littorina Sea appeared in this area. The lagoon systems and sand accretion bodies (spits and bars) were formed during the following decreasing of the sea level. Late

  12. Optically stimulated luminescence age controls on late Pleistocene and Holocene coastal lithosomes, North Carolina, USA

    USGS Publications Warehouse

    Mallinson, D.; Burdette, K.; Mahan, S.; Brook, G.

    2008-01-01

    Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3 to 2??ka. Oxygen-isotope data are used to place these deposits in the context of global climate and sea-level change. The occurrence of MIS 5a and MIS 3 shorelines suggests that glacio-isostatic adjustment (GIA) of the study area is large (ca. 22 to 26??m), as suggested and modeled by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. Correcting the shoreline elevations for GIA brings their elevation in line with other sea-level indicators. The age of the Kitty Hawk beach ridges places the Holocene shoreline well west of its present location at ca. 3 to 2??ka. The age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing mechanism. ?? 2007 University of Washington.

  13. Holocene environmental and climatic changes at Gorgo Basso, a coastal lake in southern Sicily, Italy

    NASA Astrophysics Data System (ADS)

    Tinner, Willy; van Leeuwen, Jacqueline F. N.; Colombaroli, Daniele; Vescovi, Elisa; van der Knaap, W. O.; Henne, Paul D.; Pasta, Salvatore; D'Angelo, Stefania; La Mantia, Tommaso

    2009-07-01

    We used a new sedimentary record to reconstruct the Holocene vegetation and fire history of Gorgo Basso, a coastal lake in south-western Sicily (Italy). Pollen and charcoal data suggest a fire-prone open grassland near the site until ca 10,000 cal yr BP (8050 cal BC), when Pistacia shrubland expanded and fire activity declined, probably in response to increased moisture availability. Evergreen Olea europaea woods expanded ca 8400 to decline abruptly at 8200 cal yr BP, when climatic conditions became drier at other sites in the Mediterranean region. Around 7000 cal yr BP evergreen broadleaved forests ( Quercus ilex, Quercus suber and O. europaea) expanded at the cost of open communities. The expansion of evergreen broadleaved forests was associated with a decline of fire and of local Neolithic ( Ficus carica-Cerealia based) agriculture that had initiated ca 500 years earlier. Vegetational, fire and land-use changes ca 7000 cal yr BP were probably caused by increased precipitation that resulted from (insolation-forced) weakening of the monsoon and Hadley circulation ca 8000-6000 cal yr BP. Low fire activity and dense coastal evergreen forests persisted until renewed human activity (probably Greek, respectively Roman colonists) disrupted the forest ca 2700 cal yr BP (750 BC) and 2100 cal yr BP (150 BC) to gain open land for agriculture. The intense use of fire for this purpose induced the expansion of open maquis, garrigue, and grassland-prairie environments (with an increasing abundance of the native palm Chamaerops humilis). Prehistoric land-use phases after the Bronze Age seem synchronous with those at other sites in southern and central Europe, possibly as a result of climatic forcing. Considering the response of vegetation to Holocene climatic variability as well as human impact we conclude that under (semi-)natural conditions evergreen broadleaved Q. ilex- O. europaea (s.l.) forests would still dominate near Gorgo Basso. However, forecasted climate change and

  14. Have the northwest Negev dunefield sands reddened since their deposition?

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Tsoar, Haim; Blumberg, Dan G.; Porat, Naomi; Rozensten, Ofer

    2010-05-01

    Sand grain coating redness has been extensively both in coastal and inland desert dunes. In Israel, sand redness has been quantified by calculating a spectral redness index (RI) using single RGB bands (RI= R2/(B*G3)) from reflectance spectroscopy. The RI values have been correlated to ferric oxide mass that was dissolved from sand grain coatings (Ben Dor et al., 2006; Tsoar et al., 2008). Five main requirements have been proposed to enhance sand grain reddening: iron source from the weathering of iron-bearing minerals originating from parent rock or aeolian dust, minimum moisture content, oxidizing interstitial conditions, sediment stability and time. Thus, as many researches have suggested, when the source factors and climatic conditions are homogenous, redder sands indicate increased maturity. The northwest Negev dunefield has been classified by Tsoar et al. (2008) into 3 incursion units based upon contouring a grid of RI values for surface sand samples. The central incursion unit has been suggested to be younger due to relatively lower RI values that decrease to the east. This work tests the relationship between RI values and optically stimulated luminescence (OSL) ages of aeolian sand sampled from the near surface down to dune substrate throughout the NW Negev dunefield. Room-dried sand samples were measured in the laboratory with an ASD FieldSpec spectrometer and RI was calculated. Dune sections have been found to usually have similar RI values throughout their vertical profile despite OSL ages ranging between recent and Late Pleistocene. Along a W-E transect, RI values also tend to be similar. The central (Haluzza) part of the dunefield exhibits significantly lower RI values than RI of sands south of the Qeren Ridge. Dune base OSL ages possibly representing burial/stabilization of an initial incursion are slightly more mature in the south and may be evidence of the earliest dune incursion into the Negev. Thus the increased redness may be attributed to an

  15. Holocene groundwater turnover in an coastal aquifer in Albania - mirrored by isotopes

    NASA Astrophysics Data System (ADS)

    Jacks, G.; Kumanova, Xh; Marku, S.

    2012-04-01

    Holocene groundwater turnover in a coastal aquifer in Albania - mirrored by isotopes Jacks G 1, Kumanova Xh 2 and Marku S 2 1) Dept. of Land and Water Resources Engineering, KTH, SE-114 29 Stockholm, Sweden 2) Albanian Geological Survey, Tirana, Albania Mati River has formed a coastal aquifer in N. Albania serving as a water source for 220 000 people. The near shore portions of the aquifer have a brackish groundwater. A crucial question is to what extent the aquifer is recharged from the alluvial cone at the entrance of the river into the coastal plain and to what extent the brackish water is drawn into a large well-field supplying Durres, the second largest town in Albania. The brackish water was dated by 14C, resulting in ages between 4-7000 years BP. ^18O data showed that the brackish water was not a mixture between sea water and fresh water but had freshwater signature of -5 to -10 o/oo. The low values are caused by the oxidation of sulphides in a copper mining area upstream in the Mati River catchment (Demi 2003). Most likely the salinity is derived from diffusion from saline pore water in intercalated clay layers. A similar condition is found in the coastal Kerala aquifers in Southern India (Jacks et al., 2007). The water extracted in the large well-field has low salinity. ^34S data show that the pumped groundwater has a typical river signature with ^34S = 4-5 o/oo while the brackish near shore water has a sea water signature around 20-21 o/oo. Thus the extracted water is almost entirely supplied by current recharge from the alluvial cone. The salinity now restricted to pore water in the intercalated clay layers might be derived from the Flandrian transgression. A shore line has been observed close to the foothills in the plane by Fouache (2006). The paleo-levels of the sea is very variable along the Adriatic coast as this is a tectonic active areas along the seam between the African and the European plates (Allaj et al. 2001; Fouache 2006; Mathers et al

  16. A Holocene pollen and diatom record from Vanderlin Island, Gulf of Carpentaria, lowland tropical Australia

    NASA Astrophysics Data System (ADS)

    Prebble, Matiu; Sim, Robin; Finn, Jan; Fink, David

    2005-11-01

    Sedimentary, palynological and diatom data from a dunefield lake deposit in the interior of Vanderlin Island in the Gulf of Carpentaria are presented. Prior to the formation of present perennial lake conditions, the intensified Australian monsoon associated with the early Holocene marine transgression allowed Cyperaceae sedges to colonise the alluvial margins of an expansive salt flat surrounded by an open Eucalyptus woodland. As sea level stabilised between 7500 and 4500 cal yr B.P. coastal dunes ceased to develop allowing dense Melaleuca forest to establish in a Restionaceae swamp. Dune-sand input into the swamp was diminished further as the increasingly dense vegetation prevented fluvial and aeolian transported sand arriving from coastal sources. This same process impounded the drainage basin allowing a perennial lake to form between 5500 and 4000 cal yr B.P. Myriophyllum and other aquatic taxa colonised the lake periphery under the most extensive woodland recorded for the Holocene. The palynological data support an effective precipitation model proposed for northern Australia that suggests more variable conditions in the late Holocene. A more precise measure of effective precipitation change is provided by diatom-based inferences that indicate few changes in lake hydrology. Such interpretations are explained in terms of palynological sensitivity to adjustments in local fire regimes where regional precipitation change may only be recorded indirectly through fire promoting mechanisms, including intensified ENSO periodicity and human impact.

  17. Rapid Holocene coastal change revealed by high-resolution micropaleontological analysis, Pamlico Sound, North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Grand Pre, Candace; Culver, Stephen J.; Mallinson, David J.; Farrell, Kathleen M.; Corbett, D. Reide; Horton, Benjamin P.; Hillier, Caroline; Riggs, Stanley R.; Snyder, Scott W.; Buzas, Martin A.

    2011-11-01

    Foraminiferal analyses of 404 contiguous samples, supported by diatom, lithologic, geochronologic and seismic data, reveal both rapid and gradual Holocene paleoenvironmental changes in an 8.21-m vibracore taken from southern Pamlico Sound, North Carolina. Data record initial flooding of a latest Pleistocene river drainage and the formation of an estuary 9000 yr ago. Estuarine conditions were punctuated by two intervals of marine influence from approximately 4100 to 3700 and 1150 to 500 cal yr BP. Foraminiferal assemblages in the muddy sand facies that accumulated during these intervals contain many well-preserved benthic foraminiferal species, which occur today in open marine settings as deep as the mid shelf, and significant numbers of well-preserved planktonic foraminifera, some typical of Gulf Stream waters. We postulate that these marine-influenced units resulted from temporary destruction of the southern Outer Banks barrier islands by hurricanes. The second increase in marine influence is coeval with increased rate of sea-level rise and a peak in Atlantic tropical cyclone activity during the Medieval Climate Anomaly. This high-resolution analysis demonstrates the range of environmental variability and the rapidity of coastal change that can result from the interplay of changing climate, sea level and geomorphology in an estuarine setting.

  18. Wet early to middle Holocene conditions on the upper Coastal Plain of North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Goman, Michelle; Leigh, David S.

    2004-05-01

    A peat core from a cutoff paleochannel of Little River on the upper Coastal Plain of North Carolina provides a continuous pollen record of environmental change for the past 10,500 years and includes a sedimentary record of overbank floods. Palynological and sedimentary data indicate that the early to middle Holocene was wetter than previously suggested from lake sites in the southeastern United States. The period from 9000 to 6100 cal yr B.P. is characterized by high pollen percentages of Nyssa and Quercus, but low percentages of Pinus. Fifteen large overbank flood events are present within this period (5 floods/1000 yr). In contrast, only 6 large overbank flood events occurred since 6100 cal yr B.P. (1 flood/1000 yr). The increases in moisture and flood events probably were controlled by changes in atmospheric circulation related to shifts in the position of the Bermuda High, sea surface temperatures, and El Niño activity that together may have affected the frequency of large floods generated from tropical storms in the region.

  19. Holocene coastal notches in the Mediterranean region: Indicators of palaeoseismic clustering?

    NASA Astrophysics Data System (ADS)

    Boulton, S. J.; Stewart, I. S.

    2015-05-01

    Marine tidal notches are developed by bioerosion in the intertidal zones of rocky coasts, but a combination of sea-level change and crustal movements can result in them being raised above or submerged below the water line. For that reason, the present-day elevation of these former shorelines relative to the mean sea level has long been used to quantify relative coastal uplift and subsidence in tectonically active areas, assuming that the sea-level (eustatic) change component is known. Along the microtidal Mediterranean littoral, it is generally assumed that notches develop during relative stillstands of sea level, when tectonic and eustatic trends are in unison, and that discrete notch levels record abrupt shoreline changes caused by local seismic displacements. Recently, however, a climatic model for notch formation has been proposed, in which stable periods of Holocene climate favour enhanced erosion; in this competing model, the rate of sea-level rise is lower than the tectonic uplift rate and individual notches are not specific seismic indicators. Because marine notches are widely used as geomorphic markers of tectonic, and in some cases palaeoseismic, movements, a reappraisal of the geological significance of these strandlines is warranted. In this paper, we explore the two conflicting notch models using a database of Eastern Mediterranean palaeoshorelines. Although we conclude that the spatial and temporal distribution of the notches supports a dominantly tectonic control on notch genesis as a result of earthquake clustering, we highlight how the diachronous timing of notch development tempers their value as tectonic markers.

  20. Rapid Holocene coastal change revealed by high-resolution micropaleontological analysis, Pamlico Sound, North Carolina, USA

    USGS Publications Warehouse

    Grand, Pre C.; Culver, S.J.; Mallinson, D.J.; Farrell, K.M.; Corbett, D.R.; Horton, B.P.; Hillier, C.; Riggs, S.R.; Snyder, S.W.; Buzas, M.A.

    2011-01-01

    Foraminiferal analyses of 404 contiguous samples, supported by diatom, lithologic, geochronologic and seismic data, reveal both rapid and gradual Holocene paleoenvironmental changes in an 8.21-m vibracore taken from southern Pamlico Sound, North Carolina. Data record initial flooding of a latest Pleistocene river drainage and the formation of an estuary 9000. yr ago. Estuarine conditions were punctuated by two intervals of marine influence from approximately 4100 to 3700 and 1150 to 500. cal. yr BP. Foraminiferal assemblages in the muddy sand facies that accumulated during these intervals contain many well-preserved benthic foraminiferal species, which occur today in open marine settings as deep as the mid shelf, and significant numbers of well-preserved planktonic foraminifera, some typical of Gulf Stream waters. We postulate that these marine-influenced units resulted from temporary destruction of the southern Outer Banks barrier islands by hurricanes. The second increase in marine influence is coeval with increased rate of sea-level rise and a peak in Atlantic tropical cyclone activity during the Medieval Climate Anomaly. This high-resolution analysis demonstrates the range of environmental variability and the rapidity of coastal change that can result from the interplay of changing climate, sea level and geomorphology in an estuarine setting. ?? 2011 University of Washington.

  1. Coastline orientation, aeolian sediment transport and foredune and dunefield dynamics of Moçambique Beach, Southern Brazil

    NASA Astrophysics Data System (ADS)

    Miot da Silva, Graziela; Hesp, Patrick

    2010-08-01

    This paper examines the role of coastline orientation on foredune and dunefield development at Moçambique Beach, Southern Brazil. The beach displays significant alongshore variations in exposure to the prevailing winds and waves, grain size, beach/surfzone morphodynamic type, foredune volume, and type and dimensions of the Holocene dune systems. Two wind analyses and calculation of aeolian drift potentials were carried out, one based on 1 year of wind record and another based on a record of 34 years. Monthly topographic surveys of beach and foredunes on 5 profiles along Moçambique beach were conducted over one year to obtain data on beach mobility and width, aeolian sediment transport and foredune development. Southerly winds dominate, and aeolian sediment supply is minimal in the south, moderate in the central portion and high in the northern portion of the embayment. The relationship between actual sediment supply, foredune building and potential sediment supply is relatively poor over one year due to factors such as beach type and mobility, beach moisture levels, rainfall, storm surge and wave scarping. The intermediate term (34 year) record indicates a strong relationship between foredune size and volume, winds and shoreline orientation: foredune volume is minimum in the southern part of the beach and greatest in the northern part of the beach. The Holocene barrier and dunefield development also reflects the long term control of shoreline orientation and increasing longshore gradient in exposure to southerly winds: for the last 6000-7000 years a small foredune developed in the southern portion, parabolics and small transgressive dunes in the central portion, and a large-scale transgressive dunefield in the northern portion.

  2. Coastal evidence for Holocene subduction-zone earthquakes and tsunamis in central Chile

    USGS Publications Warehouse

    Dure, Tina; Cisternas, Marco; Horton, Benjamin; Ely, Lisa; Nelson, Alan R.; Wesson, Robert L.; Pilarczyk, Jessica

    2015-01-01

    The ∼500-year historical record of seismicity along the central Chile coast (30–34°S) is characterized by a series of ∼M 8.0–8.5 earthquakes followed by low tsunamis (<4 m) occurring on the megathrust about every 80 years. One exception is the AD 1730 great earthquake (M 9.0–9.5) and high tsunami (>10 m), but the frequency of such large events is unknown. We extend the seismic history of central Chile through a study of a lowland stratigraphic sequence along the metropolitan coast north of Valparaíso (33°S). At this site, higher relative sea level during the mid Holocene created a tidal marsh and the accommodation space necessary for sediment that preserves earthquake and tsunami evidence. Within this 2600-yr-long sequence, we traced six laterally continuous sand beds probably deposited by high tsunamis. Plant remains that underlie the sand beds were radiocarbon dated to 6200, 5600, 5000, 4400, 3800, and 3700 cal yr BP. Sediment properties and diatom assemblages of the sand beds—for example, anomalous marine planktonic diatoms and upward fining of silt-sized diatom valves—point to a marine sediment source and high-energy deposition. Grain-size analysis shows a strong similarity between inferred tsunami deposits and modern coastal sediment. Upward fining sequences characteristic of suspension deposition are present in five of the six sand beds. Despite the lack of significant lithologic changes between the sedimentary units under- and overlying tsunami deposits, we infer that the increase in freshwater siliceous microfossils in overlying units records coseismic uplift concurrent with the deposition of five of the sand beds. During our mid-Holocene window of evidence preservation, the mean recurrence interval of earthquakes and tsunamis is ∼500 years. Our findings imply that the frequency of historical earthquakes in central Chile is not representative of the greatest earthquakes and tsunamis that the central Chilean subduction zone has

  3. The relationship between Holocene cultural site distribution and marine terrace uplift on the coast fringing Coastal Range, Taiwan

    NASA Astrophysics Data System (ADS)

    Yang, Hsiaochin; Chen, Wenshan

    2013-04-01

    According to the collision of Philippine Sea plate and Eurasia plate, a series of left-lateral active faults with reverse sense exists in the Longitudinal Valley of east Taiwan. The Holocene marine terraces along the east coast of the Coastal Range in Taiwan are well known for their very rapid uplift and record tectonic history of this active collision boundary. The Holocene marine terrace sequence resulting from successive sea level change and tectonic activation is subdivided into several steps where the highest and oldest terrace, back to ca 13,000yr BP, reaches up to ca 80 m above sea level, and the lower terraces are mostly erosional ones, overlain by less than 1m thick coral beds in situ. The uplift of the coast is very high, ranging from 5 to 10 m/ka. According to the fabrics of potsherds and geochronological data, the prehistoric cultures in eastern Taiwan could be classified into three stages: Fushan (ca 5000-3500yr BP), Peinan/Chilin (ca3500-2000yr BP), Kweishan (ca2000-1000 yr BP) and Jinpu (ca 1000-400yr BP) cultural assemblages respectively. A great difference exists between the various cultural stage, not only the pottery making techniques, but also the distributions of archaeological sites. Combined with the dynamic geomorphic evolution of marine terraces and the distribution of prehistoric culture sites on the east coast of the Coastal Range, a coastal migration trend could be established.

  4. Reconstructing Holocene sea-level change from coastal freshwater peat: A combined empirical and model-based approach

    NASA Astrophysics Data System (ADS)

    Anderson, William; Gehrels, Roland

    2014-05-01

    Freshwater environments have long been considered to be unsuitable for the reconstruction of Holocene sea-level changes as they provide limiting, rather than precise, sea-level index points. We recorded the stratigraphy of a small beach and backbarrier coastal Phragmites marsh at Hallsands, south Devon, southwest England, using hand-drilled cores and ground penetrating radar, and collected five new sea-level index points from the base of a Holocene peat sequence to refine the regional Holocene relative sea-level curve. We demonstrate that the samples, despite their freshwater origin, represent accurate sea-level index points due to the quantifiable relationship between tide levels and groundwater. By means of water-table monitoring and groundwater modelling we show that the primary controls on the water table in the marsh are: (1) stratigraphy; (2) peat permeability; and (3) recharge rates in the backbarrier marsh. The five index points document relative sea-level positions between 7200 and 2400 cal yr BP. Three points are in good agreement with previously collected regional data from intertidal deposits and two points usefully fill gaps in the existing reconstruction. We present an amended Holocene relative sea-level curve for south Devon, based on 30 data points. We conclude that the base of Holocene freshwater peat sequences in small backbarrier systems provide reliable index points for the reconstruction of relative Holocene sea-level changes provided that: (1) the backbarrier stratigraphy show uninterrupted peat sequences demonstrating that the barrier has remain closed; (2) the water table in the backbarrier marsh is controlled by the tidally-oscillating sea level; (3) values of recharge and peat permeability are such that ponding and drying of the backbarrier marsh is limited; and (4) the beach is relatively thin and its permeability is not the primary control of water-table elevations in the backbarrier marsh. The combined approach of data collection and

  5. Mineralogical maturity in dunefields of North America, Africa and Australia

    USGS Publications Warehouse

    Muhs, D.R.

    2004-01-01

    Studies of dunefields in central and western North America show that mineralogical maturity can provide new insights into the origin and evolution of aeolian sand bodies. Many of the world's great sand seas in Africa, Asia and Australia are quartz-dominated and thus can be considered to be mineralogically mature. The Algodones (California) and Parker (Arizona) dunes in the southwestern United States are also mature, but have inherited a high degree of mineralogical maturity from quartz-rich sedimentary rocks drained by the Colorado River. In Libya, sediments of the Zallaf sand sea, which are almost pure quartz, may have originated in a similar fashion. The Fort Morgan (Colorado) and Casper (Wyoming) dunefields in the central Great Plains of North America, and the Namib sand sea of southern Africa have an intermediate degree of mineralogical maturity because their sources are large rivers that drained both unweathered plutonic and metamorphic rocks and mature sedimentary rocks. Mojave Desert dunefields in the southwestern United States are quite immature because they are in basins adjacent to plutonic rocks that were their sources. Other dunefields in the Great Plains of North America (those in Nebraska and Texas) are more mature than any possible source sediments and therefore reflect mineralogical evolution over time. Such changes in composition can occur because of either of two opposing long-term states of the dunefield. In one state, dunes are stable for long periods of time and chemical weathering depletes feldspars and other weatherable minerals in the sediment body. In the other state, which is most likely for the Great Plains, abrasion and ballistic impacts deplete the carbonate minerals and feldspars because the dunes are active for longer periods than they are stable. ?? 2003 Elsevier B.V. All rights reserved.

  6. Do dune sands redden with age? The case of the northwestern Negev dunefield, Israel

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Blumberg, Dan G.; Porat, Naomi; Tsoar, Haim; Rozenstein, Offer

    2012-08-01

    The redness index of aeolian sand has been shown to be a promising qualitative spectroscopic method to define sand grain redness intensity, which reflects the extent of iron-oxide quartz grain coatings. This study investigates the relationship between redness intensity and optically stimulated luminescence (OSL) based depositional ages of sand samples taken from exposed and fully-drilled vegetated linear dunes in the northwestern Negev dunefield, Israel. Sand redness intensity did not vary greatly along the Negev sand transport paths and dune sections dated to be active during the Late Pleistocene (˜18-11.5 ka), Late Holocene, and modern times. No correlation was found between RI intensity (i.e., redness) and the depositional age of the sand. The relatively uniform RI values and sedimentological properties along most of the dunes suggest that sand grain coating development, and consequent rubification, have probably been minimal since the Late Pleistocene. Although it is possible that RI developed rapidly following deposition in a wetter Late Pleistocene climate, the drier and less stormy Holocene does not seem conducive to sand-grain rubification. Based on analyses of northern Sinai sand samples, remote sensing, and previous studies, we suggest that the attributes of the sand grain RI have been inherited from upwind sources. We propose that the sand grain coatings are early diagenetic features that have been similarly red since their suggested aeolian departure from the middle and upper Nile Delta.

  7. Late Holocene coastal wetlands change, Mississippi Sound, Alabama: Short-term vs. long-term patterns and processes

    SciTech Connect

    Davies, D.J.; Smith, W.E. . Environmental Geology Div.)

    1994-03-01

    Wetlands occupy much of the low-lying mainland coast in Mississippi Sound, Alabama, grading from Spartina salt marsh (48.8 km[sup 2]) to fresh water marshes (13.5 km[sup 2]) to forested wetlands (123.4 km[sup 2]) (Rathbun et al, 1987). These wetlands are undergoing rapid short-term (years to decades) net acreage loss due to headland shoreline erosion. In contrast, long-term (centuries to millennia) change in marsh area is largely due to submergence from Holocene transgression and local subsidence. The Sound overlies drowned Pleistocene-Holocene coastal sediments; existing salt marshes likely developed after inundation of paleomarshes cored at a MHW depth of [minus]3 to [minus]7 m in the mid-Sound (C[sup 14] dates of 4--7,000 Y.B.P.). Geomorphic evidence indicates the primary cause of short-term loss of salt marsh is localized erosion of its seaward edge, rather than submergence. A low (< 1 m) intertidal scarp and narrow sandy beach on open Sound shorelines indicate episodic storm erosion. Linear open Sound shorelines formed by wave modification, in contrast to typically less modified protected shores; nearshore Sound bathymetry shows a gently seaward sloping possible wave-cut terrace. Marsh erosion rates are due to several processes including water energy (background as well as seasonal storms); cohesiveness of marsh sediments; and health of marsh flora. Orientation of the shoreline relative to southerly wind-forced waves during passage of winter cold fronts may be the primary factor. While today's short-term rates of overall vertical coastal inundation are relatively low, the development of new marsh acreage is also negligible. As sediment influx from coastal streams is low, it may be difficult to sustain present marsh acreage should sea level rise accelerate.

  8. Late Pleistocene to Holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments, southwestern Taiwan

    USGS Publications Warehouse

    Chen, Y.-G.; Liu, J.C.-L.; Shieh, Y.-N.; Liu, T.-K.

    2004-01-01

    A core, drilled at San-liao-wan in the southwestern coastal plain of Taiwan, has been analyzed for total sulfur contents, isotopic values, as well as ratios of pyritic sulfur to organic carbon. Our results demonstrate a close relationship between late Pleistocene sea-level change and the proxies generated in this study. The inorganic sulfur contents indicate that at our study site, the Holocene transgression started at ???11 ka and remained under seawater for thousands of years until the late Holocene, corresponding to a depth of 20 m in the study core. The uppermost 20 m of core shows relatively high total organic carbon (TOC) and ??34S of inorganic sulfur, suggesting a transitional environment such as muddy lagoon or marsh, before the site turned into a modern coastal plain. In the lower part of the core, at depths of 110-145 m (corresponding ages of ???12-30 ka), low sulfur contents are recorded, probably indicating fluvial sediments deposited during the oceanic isotope stage (OIS) 2, a sea-level lowstand. The lower part of the core, roughly within OIS 3, records at least two transgressions, although the transgressional signals may be somewhat obscured by subsequent weathering. The reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data; however, the marine organic source was periodically dominant. The modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments, probably indicating that the sulfate migrated into the site subsequent to early diagenesis. ?? 2003 Elsevier Ltd. All rights reserved.

  9. Late Holocene Hydrologic Variability Reconstruction of the Coastal Southwestern United States Using Lake Sediments from Crystal Lake, CA

    NASA Astrophysics Data System (ADS)

    Palermo, J. A.; Kirby, M. E.; Hiner, C.; Leeper, R. J.

    2014-12-01

    This study aims to reconstruct a high resolution, late Holocene record of precipitation variability for the coastal southwestern United States region using sediment cores from Crystal Lake, CA. This region is especially susceptible to droughts and episodic floods, making it of particular importance to understand past hydrologic variability. Crystal Lake is a small, alpine landslide dammed lake in the Angeles National Forest of the San Gabriel Mountains. The lake is the only permanent, freshwater lake located in the range. It is hydrologically closed, meaning all lake level changes are controlled by changes in precipitation: evaporation. To reconstruct past hydrologic variability, two Livingston piston cores were taken 15 m apart in the depocenter of the lake in May 2014. A multi-proxy methodology was utilized including: magnetic susceptibility, total organic matter and total carbonate content, grain size, and bulk d13Corg of sediments. All analyses were conducted at 1 cm contiguous intervals except bulk d13Corg (at 2 cm). Seismic reflection profiles were also generated to examine the basin's stratigraphic features in the context of the individual sediment cores. A working age model was provided by multiple AMS 14C dates from discrete organic matter (i.e., seeds, charcoal). Results from this study are compared to preexisting records of late Holocene hydrologic variability from coastal, central, and southern California. Further, the forcing mechanisms that drive hydrologic change (wet vs. dry episodes) in Southern California, such as ocean-atmosphere interactions including El Niño Southern Oscillation or the Pacific Decadal Oscillation, are discussed.

  10. Recent and Holocene climate change controls on vegetation and carbon accumulation in Alaskan coastal muskegs

    NASA Astrophysics Data System (ADS)

    Peteet, Dorothy M.; Nichols, Jonathan E.; Moy, Christopher M.; McGeachy, Alicia; Perez, Max

    2016-01-01

    Pollen, spore, macrofossil and carbon data from a peatland near Cordova, Alaska, reveal insights into the climate-vegetation-carbon interactions from the initiation of the Holocene, c. the last 11.5 ka, to the present (1 ka = 1000 calibrated years before present where 0 = 1950 CE). The Holocene period is characterized by early deposition of gyttja in a pond environment with aquatics such as Nuphar polysepalum and Potamogeton, and a significant regional presence of Alnus crispa subsp. sinuata. Carbon accumulation (50 g/m2/a) was high for a short interval in the early Holocene when Sphagnum peat accumulated, but was followed by a major decline to 13 g/m2/a from 7 to 3.7 ka when Cyperaceae and ericads such as Rhododendron (formerly Ledum) groenlandicum expanded. This shift to sedge growth is representative of many peatlands throughout the south-central region of Alaska, and indicates a drier, more evaporative environment with a large decline in carbon storage. The subsequent return to Sphagnum peat after 4 ka in the Neoglacial represents a widespread shift to moister, cooler conditions, which favored a resurgence of ericads, such as Andromeda polifolia, and increased carbon accumulation rate. The sustained Alnus expansion visible in the top 10 cm of the peat profile is correlative with glacial retreat and warming of the region in the last century, and suggests this colonization will continue as temperature increases and ice melts.

  11. Palynological reconstruction of environmental changes in coastal wetlands of the Florida Everglades since the mid-Holocene

    NASA Astrophysics Data System (ADS)

    Yao, Qiang; Liu, Kam-biu; Platt, William J.; Rivera-Monroy, Victor H.

    2015-05-01

    Palynological, loss-on-ignition, and X-ray fluorescence data from a 5.25 m sediment core from a mangrove forest at the mouth of the Shark River Estuary in the southwestern Everglades National Park, Florida were used to reconstruct changes occurring in coastal wetlands since the mid-Holocene. This multi-proxy record contains the longest paleoecological history to date in the southwestern Everglades. The Shark River Estuary basin was formed 5700 cal yr BP in response to increasing precipitation. Initial wetlands were frequently-burned short-hydroperiod prairies, which transitioned into long-hydroperiod prairies with sloughs in which peat deposits began to accumulate continuously about 5250 cal yr BP. Our data suggest that mangrove communities started to appear after 3800 cal yr BP; declines in the abundance of charcoal suggested gradual replacement of fire-dominated wetlands by mangrove forest over the following 2650 yr. By 1150 cal yr BP, a dense Rhizophora mangle dominated mangrove forest had formed at the mouth of the Shark River. The mangrove-dominated coastal ecosystem here was established at least 2000 yr later than has been previously estimated.

  12. 3D modelling of mechanical peat properties in the Holocene coastal-deltaic sequence of the Netherlands

    NASA Astrophysics Data System (ADS)

    Koster, Kay; Stouthamer, Esther; Cohen, Kim; Stafleu, Jan; Busschers, Freek; Middelkoop, Hans

    2016-04-01

    Peat is abundantly present within the Holocene coastal-deltaic sequence of the Netherlands, where it is alternating with clastic fluvial, estuarine and lagoonal deposits. The areas that are rich in peat are vulnerable to land subsidence, resulting from consolidation and oxidation, due to loading by overlying deposits, infrastructure and buildings, as well as excessive artificial drainage. The physical properties of the peat are very heterogeneous, with variable clastic admixture up to 80% of its mass and rapid decrease in porosity with increasing effective stress. Mapping the spatial distribution of the peat properties is essential for identifying areas most susceptible to future land subsidence, as mineral content determines volume loss by oxidation, and porosity influences the rate of consolidation. Here we present the outline of a study focusing on mapping mechanical peat properties in relation to density and amount of admixed clastic constituents of Holocene peat layers (in 3D). In this study we use a staged approach: 1) Identifying soil mechanical properties in two large datasets that are managed by Utrecht University and the Geological Survey. 2) Determining relations between these properties and palaeogeographical development of the area by evaluating these properties against known geological concepts such as distance to clastic source (river, estuary etc.). 3) Implementing the obtained relations in GeoTOP, which is a 3D geological subsurface model of the Netherlands developed by the Geological Survey. The model will be used, among others, to assess the susceptibility of different areas to peat related land subsidence and load bearing capacity of the subsurface. So far, our analysis has focused stage 1, by establishing empirical relations between mechanical peat properties in ~70 paired (piezometer) cone penetration tests and continuously cored boreholes with LOI measurements. Results show strong correlations between net cone resistance (qn), excess pore

  13. Holocene coastal carbonates and evaporites of the southern Arabian Gulf and their ancient analogues

    NASA Astrophysics Data System (ADS)

    Alsharhan, A. S.; Kendall, C. G. St. C.

    2003-06-01

    The Holocene sediments of the coast of the United Arab Emirates in the southeastern Arabian Gulf are frequently cited in the literature as type examples for analogous assemblages of carbonates, evaporites and siliciclastics throughout the geologic record. This paper is intended as a convenient single source for the description of sediments of this region, providing information on how to reach the classic localities and some of the analogs. The Holocene sediments of the region accumulate over an area that is 500 km long and up to 60 km wide. The sediments collecting offshore are predominantly pelecypod sands mixed with lime and argillaceous mud, with these latter fine sediments increasing as the water deepens. The pelecypod-rich sediments also collect east of Abu Dhabi Island both in the deeper tidal channels between the barrier island lagoons and in deeper portions of the protected lagoons. West of Abu Dhabi Island the shallow water margin is the site of coral reefs and coralgal sands, whereas to the east oolites accumulate on the tidal deltas of channels located between barrier islands. Grapestones accumulate to the lee of the reefs and the oolite shoals where cementation becomes more common. They are particularly common on the less protected shallow water margins of the lagoons west of Abu Dhabi Island. Pelleted lime muds accumulate in the lagoons in the lee of the barrier islands of the eastern Abu Dhabi. Lining the inner shores of the protected lagoons of Abu Dhabi and on other islands to the west are cyano-bacterial mats and mangrove swamps. Landward of these, a prograding north facing shoreline is formed by supratidal salt flats (sabkhas), in which evaporite minerals are accumulating. This paper describes the localities associated with (1) the mangrove swamps of the west side of the Al Dhabaiya peninsula; (2) the indurated cemented carbonate crusts, cyanobacterial flats and sabkha evaporites on the shore of the Khor al Bazam south of Qanatir Island; (3) the

  14. Holocene history of the El Nino phenomenon as recorded in flood sediments of northern coastal Peru

    SciTech Connect

    Wells, L.E. )

    1990-11-01

    Significant precipitation along the north-central coast of Peru (lat 5{degree}-10{degree}S) occurs exclusively during El Nino incursions of warm water into the Peruvian littoral. Flood deposits from this region therefore provide a proxy record of extreme El Nino events. The author presents a 3,500 yr chronology of the extreme events based on radiocarbon dating of overbank flood sediments from the Rio Casma (lat 9.2{degree}S). The flood-plain stratigraphy suggests that the El Nino phenomenon has occurred throughout the Holocene and that flood events much larger than that which occurred during 1982-1983 occur here at least once very 1,000 yr.

  15. A simple cellular model to quantify controls on aeolian dune-field pattern development

    NASA Astrophysics Data System (ADS)

    Eastwood, E. N.; Nield, J. M.; Baas, A. C.; Kocurek, G.

    2009-12-01

    A second-generation, source-to-sink cellular automaton model captures and quantifies many of the factors controlling the evolution of aeolian dune-field patterns by varying only a small number of parameters. Our model quantifies the role of sediment supply, sediment availability, and transport capacity in the development and evolution of an aeolian dune-field pattern over long time scales. Simulation results produced by varying the sediment supply and transport capacity identified seven dune-field patterns. A new clustered dune-field pattern is identified and used to propose an alternative mechanism for the formation of superimposed dunes. Bedforms are hypothesized to cluster together, simultaneously forming two spatial scales of bedforms without first developing a large basal dune and small superimposed dunes. Sediment supply and transport capacity control the type and frequency of dune interactions, the sediment availability of the system, and ultimately the development of dune-field patterns. Our model allows predictions about the range of sediment supply and wind strengths required to produce many of the dune-field patterns seen in the real world. This simple model demonstrates the dominant control of aeolian sediment state on the construction and evolution of aeolian dune-field patterns.

  16. Coastal Lake Record of Holocene Paleo-Storms from Northwest Florida

    NASA Astrophysics Data System (ADS)

    Donoghue, J. F.; Coor, J. L.; Wang, Y.; Das, O.; Kish, S.; Elsner, J.; Hu, X. B.; Niedoroda, A. W.; Ye, M.

    2009-12-01

    The northwest Florida coast of the Gulf of Mexico has an unusually active storm history. Climate records for a study area in the mid-region of the Florida panhandle coast show that 29 hurricanes have made landfall within a 100-km radius during historic time. These events included 9 major storms (category 3 or higher). A longer-term geologic record of major storm impacts is essential for better understanding storm climatology and refining morphodynamic models. The Florida panhandle region contains a series of unique coastal lakes which are long-lived and whose bottom sediments hold a long-term record of coastal storm occurrence. The lakes are normally isolated from the open Gulf, protected behind a near-continuous dune barrier. Lake water is normally fresh to brackish. Lake bottom sediments consist of organic-rich muds. During major storms the dunes are breached and the lakes are temporarily open to marine water and the possibility of sandy overwash. Both a sedimentologic and geochemical signature is imparted to the lake sediments by storm events. Bottom sediment cores have been collected from the lakes. The cores have been subsampled and subjected to sedimentologic, stable isotopic and geochronologic analyses. The result is a sediment history of the lakes, and a record of storm occurrence during the past few millennia. The outcome is a better understanding of the long-term risk of major storms. The findings are being incorporated into a larger model designed to make reliable predictions of the effects of near-future climate change on natural coastal systems and on coastal infrastructure, and to enable cost-effective mitigation and adaptation strategies.

  17. Holocene sea-level changes in King George Island, West Antarctica, by virtue of geomorphological coastal evidences and diatom assemblages of sediment sections.

    NASA Astrophysics Data System (ADS)

    Poleshchuk, Ksenia; Verkulich, Sergey; Pushina, Zina; Jozhikov, Ilya

    2015-04-01

    A new curve of relative sea-level change is presented for the Fildes peninsula, King George Island, West Antarctic. This work is based on renewed paleogeography data, including coastal geomorphological evidence, diatom assemblages of lakes bottom sediments and radiocarbon datings of organics. The new data were obtained in several sections of quaternary sediments and groups of terraces, and allows us to expand and improve relevant conception about relative sea level changes in the King George Island region. The new radiocarbon datings of organics (mosses and shells) allows reconstructing Holocene conditions that maintain and cause the sea-level changes. Sea diatom assemblages of Dlinnoye lake bottom sediment core (that complies period about 8000 years B.P.) mark altitude of marine water penetrated into the lake. The altitudes of shell remains, which have certain life habits and expect specific salinity and depth conditions, coupled with their absolute datings, indicate the probable elevation of the past sea level. The Mid-Holocene marine transgression reached its maximum level of 18-20 m by 5760 years B.P. The transgression influenced the deglaciation of the Fildes peninsula and environment conditions integrally. The ratio of glacio-isostatic adjustment velocity and Holocene transgression leaded to the decrease of relative sea level during the Late Holocene excluding the short period of rising between 2000 and 1300 years B.P. Comparing this data with the curve for Bunger oasis, East Antarctica, introduced earlier gives an interesting result. Despite the maximum altitudes of relative sea-level rise in King George region were higher and occurred later than in Bunger oasis region, the short-term period of Late Holocene sea-level rising contemporizes. Besides that, this work allow to realize a correlation between regions of Antarctica and adjacent territory. That, in turn, lets answer the question of tectonic and eustatic factors ratio and their contribution to the

  18. Supergroup stratigraphy of the Atlantic and Gulf Coastal Plains (Middle? Jurassic through holocene, Eastern North America)

    USGS Publications Warehouse

    Weems, R.E.; ,; Edwards, L.E.

    2004-01-01

    An inclusive supergroup stratigraphic framework for the Atlantic and Gulf Coastal Plains is proposed herein. This framework consists of five supergroups that 1) are regionally inclusive and regionally applicable, 2) meaningfully reflect the overall stratigraphic and structural history of the Coastal Plains geologic province of the southeastern United States, and 3) create stratigraphic units that are readily mappable and useful at a regional level. Only the Marquesas Supergroup (Lower Cretaceous to lowest Upper Cretaceous) has been previously established. The Trent Supergroup (middle middle Eocene to basal lower Miocene) is an existing name here raised to supergroup rank. The Minden Supergroup (Middle? through Upper Jurassic), the Ancora Supergroup (Upper Cretaceous to lower middle Eocene), and the Nomini Supergroup (lower Miocene to Recent) are new stratigraphic concepts proposed herein. In order to bring existing groups and formations into accord with the supergroups described here, the following stratigraphic revisions are made. 1) The base of the Shark River Formation (Trent Supergroup) is moved upward. 2) The Old Church Formation is removed from the Chesapeake Group (Nomini Supergroup) and moved to the Trent Supergroup without group placement. 3) The Tiger Leap and Penney Farms formations are removed from the Hawthorn Group (Nomini Supergroup) and moved to the Trent Supergroup without group placement. 4) The Piney Point and Chickahominy formations are removed from the Pamunkey Group (Ancora Supergroup) and moved to the Trent Supergroup without group placement. 5) the Tallahatta Formation is removed from the Claiborne Group (Trent Supergroup) and placed within the Ancora Supergroup without group placement.

  19. Paleolimnological reconstruction of Holocene environments in wetland ponds of the Upper Atlantic Coastal Plain

    SciTech Connect

    Gaiser, E.E.; Taylor, B.E.

    1995-06-01

    The paleohydrology and paleoecology of Carolina bays and upland wetland ponds on the Savannah River Site (SRS), Aiken, South Carolina are being investigated to reconstruct environmental changes brought about by long-term variation in the climate of the Upper Atlantic Coastal Plain. Cores were taken in transacts through Flamingo Bay, a temporary pond on the SRS, to determine the vertical and horizontal sediment particle size and diatom, plant phytolith and sponge spicule microfossils. Stratigraphic data were used to construct a 3-dimensional map of the basin. In conjunction with archaeological data from the rim of the pond, physical stratigraphic data indicate a decrease in pond size and depth during the past 10,000 years. In order to infer past ecological settings from the fossil record, a survey to determine microhabitat requirements of regional diatom flora was undertaken in 43 temporary ponds throughout the coastal plain of South Carolina. The relationships between diatom assemblages and environmental variables were assessed using canonical correspondence analysis. Variables contributing significantly to the diatom-environment relationship included surface core location (near shore or pelagic), water depth, hydroperiod, microhabitat substrate, and sampling date, in order of decreasing influence. Strong relationships of diatom assemblages to drought frequency within and among basins provides a reliable basis for water level reconstruction in upland temporary ponds.

  20. Holocene sea surface temperatures in the East African Coastal Current region and their relationship with North Atlantic climate

    NASA Astrophysics Data System (ADS)

    Kuhnert, Henning; Kuhlmann, Holger; Mohtadi, Mahyar; Pätzold, Jürgen

    2013-04-01

    The East African Coastal Current (EACC) is one of the western boundary currents of the Indian Ocean and represents the only pathway for southern water masses to enter the Arabian Sea. Today, sea surface temperatures (SST) in the western boundary currents region covary with those in large parts of the central tropical Indian Ocean. The latter play an important role in global climate by influencing the mean state of the North Atlantic Oscillation (NAO) and associated Atlantic SST anomalies (Hoerling et al., 2001). In the EACC region paleoclimate data are sparse and its Holocene temperature history is unexplored. We present data from a 5 m long sediment core retrieved off northern Tanzania where the EACC flows northward year-round. Proximity to the Pangani River mouth provides a steady sediment supply. We have reconstructed SST from Mg/Ca and stable oxygen isotope ratios (^18O) of the surface-dwelling planktonic foraminifera species Globigerinoides ruber (sensu stricto). Our record spans the time period from 9700 to 1400 years BP at an average temporal resolution of 40 years. The Holocene is characterized by a sequence of intervals representing cool, warm, cool, and intermediate SST, with boundaries at 7.8, 5.6, and 4.4 ka BP. SST anomalies relative to the series mean range from -0.6 to +0.75 ° C. This pattern strikingly resembles a Northwest Atlantic foraminiferal ^18O record (Cléroux et al., 2012), with warm Indian SST corresponding to low Atlantic foraminiferal ^18O (indicating low sea surface density). This matches the modern situation on the interdecadal time-scale, where a warm Indian Ocean leads to a shift of the NAO towards a positive mean state, which is accompanied by SST warming over much of the low- and mid-latitude western Atlantic and a displacement of the Gulf Stream path. We hypothesize that this mechanism also operates on millennial time-scales to explain the obvious similarities in the SST patterns observed in the Northwest Atlantic and western

  1. Stratigraphy of divers pleistocene dunefields of carbonate sands on Fuerteventura (Spain)

    NASA Astrophysics Data System (ADS)

    Roettig, Christopher-B.; Kolb, Thomas; Wolf, Daniel; Baumgart, Philipp; Richter, Christiane; Zöller, Ludwig; Faust, Dominik

    2016-04-01

    Correlating Quaternary dunefields in Northern Fuerteventura is a scientific challenge as reliable stratigraphic findings are only available for the Lajares-Dunefields (Faust et al., 2015). Over the last few years we added further important sites to better understand the system dynamics and characteristics. A detailed stratigraphy of dune-paleosol-sequences in four dunefields spanning the entire region of Northern Fuerteventura will be proposed. This study aims at correlating marker horizons across all investigated dunefields. The correlation is based on environmental magnetic findings, geochemical and granulometric analyses, elemental composition and finally on mollusk assemblages. We could identify guide assemblages of mollusks that enable us to trace marker horizons over long distances in all studied dune-paleosol-sequences. A first chronological assessment will be presented. Furthermore the question of soil forming intensity will be discussed considering the background of climate change vs. exposition duration.

  2. A Holocene record of climate-driven shifts in coastal carbon sequestration

    USGS Publications Warehouse

    Mitra, Siddhartha; Zimmerman, A.R.; Hunsinger, G.B.; Willard, D.; Dunn, J.C.

    2009-01-01

    A sediment core collected in the mesohaline portion of Chesapeake Bay was found to contain periods of increased delivery of refractory black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs). The BC was most likely produced by biomass combustion during four centennialscale dry periods as indicated by the Palmer Drought Severity Index (PDSI), beginning in the late Medieval Warm Period of 1100 CE. In contrast, wetter periods were associated with increased non-BC organic matter influx into the bay, likely due to greater runoff and associated nutrient delivery. In addition, an overall increase in both BC and non-BC organic matter deposition during the past millennium may reflect a shift in climate regime. The finding that carbon sequestration in the coastal zone responds to climate fluctuations at both centennial and millennial scales through fire occurrence and nutrient delivery has implications for past and future climate predictions. Drought-induced fires may lead, on longer timescales, to greater carbon sequestration and, therefore, represent a negative climate feedback. Copyright 2009 by the American Geophysical Union.

  3. Rapid late Pleistocene/Holocene uplift and coastal evolution of the southern Arabian (Persian) Gulf

    NASA Astrophysics Data System (ADS)

    Wood, Warren W.; Bailey, Richard M.; Hampton, Brian A.; Kraemer, Thomas F.; Lu, Zhong; Clark, David W.; James, Rhodri H. R.; Al Ramadan, Khalid

    2012-03-01

    The coastline along the southern Arabian Gulf between Al Jubail, Kingdom of Saudi Arabia, and Dubai, UAE, appears to have risen at least 125 m in the last 18,000 years. Dating and topographic surveying of paleo-dunes (43-53 ka), paleo-marine terraces (17-30 ka), and paleo-marine shorelines (3.3-5.5 ka) document a rapid, > 1 mm/a subsidence, followed by a 6 mm/a uplift that is decreasing with time. The mechanism causing this movement remains elusive but may be related to the translation of the coastal area through the backbasin to forebulge hinge line movement of the Arabian plate or, alternatively, by movement of the underlying Infracambrian-age Hormuz salt in response to sea-level changes associated with continental glaciation. Independent of the mechanism, rapid and episodic uplift may impact the design of engineering projects such as nuclear power plants, airports, and artificial islands as well as the interpretation of sedimentation and archeology of the area.

  4. Automated mapping of linear dunefield morphometric parameters from remotely-sensed data

    NASA Astrophysics Data System (ADS)

    Telfer, M. W.; Fyfe, R. M.; Lewin, S.

    2015-12-01

    Linear dunes are among the world's most common desert dune types, and typically occur in dunefields arranged in remarkably organized patterns extending over hundreds of kilometers. The causes of the patterns, formed by dunes merging, bifurcating and terminating, are still poorly understood, although it is widely accepted that they are emergent properties of the complex system of interactions between the boundary layer and an often-vegetated erodible substrate. Where such dunefields are vegetated, they are typically used as extensive rangeland, yet it is evident that many currently stabilized dunefields have been reactivated repeatedly during the late Quaternary. It has been suggested that dunefield patterning and the temporal evolution of dunefields are related, and thus there is considerable interest in better understanding the boundary conditions controlling dune patterning, especially given the possibility of reactivation of currently-stabilized dunefields under 21st century climate change. However, the time-consuming process of manual dune mapping has hampered attempts at quantitative description of dunefield patterning. This study aims to develop and test methods for delineating linear dune trendlines automatically from freely-available remotely sensed datasets. The highest resolution free global topographic data presently available (Aster GDEM v2) proved to be of marginal use, as the topographic expression of the dunes is of the same order as the vertical precision of the dataset (∼10 m), but in regions with relatively simple patterning it defined dune trends adequately. Analysis of spectral data (panchromatic Landsat 8 data) proved more promising in five of the six test sites, and despite poor panchromatic signal/noise ratios for the sixth site, the reflectance in the deep blue/violet (Landsat 8 Band 1) offers an alternative method of delineating dune pattern. A new edge detection algorithm (LInear Dune Optimized edge detection; LIDO) is proposed, based on

  5. Granulometric characterization and evaluation of annually banded mid-Holocene estuarine silts, Welsh Severn Estuary (UK): coastal change, sea level and climate

    NASA Astrophysics Data System (ADS)

    Allen, J. R. L.; Haslett, S. K.

    2006-07-01

    Holocene silts (salt marshes) and highest intertidal-supratidal peats are superbly exposed on a 15 km coastal transect which reveals two laterally extensive units of annually banded silts (Beds 3, 7) associated with three transgressive-regressive silt-peat cycles (early sixth-early fourth millennium BC). Bed 3 in places is concordantly and gradationally related to peats above and below, but in others transgresses older strata. Bed 7 also grades up into peat, but everywhere overlies a discordance. The banding in Bed 3 at three main and two minor sites was resolved and characterized texturally at high-resolution (2.5/5 mm contiguous slices) using laser granulometry (LS230 with PIDS) and a comprehensive scheme of data-assessment. Most of Bed 3 formed very rapidly, at peak values of several tens of millimetres annually, in accordance with modelled effects of sea-level fluctuations on mature marshes (bed concordant and gradational) and on marshes growing up after coastal erosion and retreat (bed with discordant base). Using data from the modern Severn Estuary, the textural contrast within bands, and its variation between bands, points to a variable but overall milder mid-Holocene climate than today. The inter-annual variability affected marsh dynamics, as shown by the behaviour of the finely divided plant tissues present. Given local calibration, the methodology is applicable to other tidal systems with banded silts in Britain and mainland northwest Europe.

  6. Reconstruction of Holocene coastal foredune progradation using luminescence dating — An example from the Świna barrier (southern Baltic Sea, NW Poland)

    NASA Astrophysics Data System (ADS)

    Reimann, Tony; Tsukamoto, Sumiko; Harff, Jan; Osadczuk, Krystyna; Frechen, Manfred

    2011-09-01

    Two sandy spits on the Świna barrier (Wolin and Uznam) provide a very detailed succession of Holocene coastal foredunes and dunes and are regarded as key sites along the southern Baltic Sea coast. Optically Stimulated Luminescence (OSL) dating is proven to be a powerful tool for the reconstruction of Holocene coastal spit evolution and foredune accretion; quartz extracted from the coastal sediments in the study area provides excellent properties for OSL dating. The OSL age from the innermost dune indicates that spit development of the Świna barrier started immediately after rapid sea-level rise of the Littorina transgression decelerated at ~ 6.6 ka. A significant change in the foredune progradation rate occurred during the late Subatlantic transgression at ~ 1.2 ka (800 AD), when migration rates decreased from 2.6 ± 0.7 m a - 1 to 1.3 ± 0.4 m a - 1 . Progradation accelerated again during the "Little Ice Age" between 1550 and 1850 AD. The systematic dating of 28 samples reveals six hiatuses during foredune succession, at ~ 2100 BC, ~ 900 BC, 200 BC-200 AD, ~ 600 AD, ~ 1000 AD, and ~ 1600 AD. The timing of these hiatuses correlates with the phases of transgressive dune development in the surrounding area (Troszyn and Świna) and with phases of increased aeolian activity in other parts of North- and West-Europe. We conclude that four of these phases of foredune erosion/instability and aeolian sediment mobilisation were caused by general climate shifts to cooler and stormier conditions at ~ 2200 BC, ~ 900 BC, ~ 600 AD, and at ~ 1600 AD, the latter corresponding to the "Little Ice Age". The period of increased aeolian activity around 1000 AD is probably to a phase of intensive forest clearance in Central Europe. In contrast, the systematic foredune accretion and foredune plain growth correlates to periods of positive sediment budget, milder and calmer climate, and an intact vegetation cover.

  7. Coastal lagoon systems as indicator of Holocene sea-level development in a periglacial soft-sediment setting: Samsø, Denmark

    NASA Astrophysics Data System (ADS)

    Sander, Lasse; Fruergaard, Mikkel; Johannessen, Peter N.; Morigi, Caterina; Nielsen, Lars Henrik; Pejrup, Morten

    2014-05-01

    lagoon systems a valuable archive for the reconstruction of Holocene sea-level and coastal evolution.

  8. Continuous coastal subsidence during the Holocene along a source region of the 2011 great Tohoku-oki, Japan, earthquake revealed from new paleo-geodetic data

    NASA Astrophysics Data System (ADS)

    Niwa, Y.; Toda, S.; Sugai, T.

    2015-12-01

    Time-dependent inconsistency of crustal movement is suggested in the Sanriku coast, northeast Japan. In northern Sanriku, coseismic subsidence up to 0.4 m of the 2011 M=9.0 Tohoku-oki earthquake and a century-long subsidence apparently contradict to long-term uplift estimated from Pleistocene marine terraces. To explain the inconsistency, the following hypotheses have been proposed: 1) the 2011 event was typical, contributing long-term (104 yr) subsidence, 2) a significant interseismic contribution to long-term uplift, or 3) unknown huge events may have occurred to uplift the coastal region. However, in the southern Sanriku, closer to the 2011 source, poorly distributed marine terraces do not allow us to confirm the long-term uplift. We instead focus on the coastal plains that preserve sediments recording the tectonic history with better age constraints. We extracted 40 m-long samples of the Holocene sediments in the Rikuzen-takata and Kesennuma-Okawa plains, along the southern Sanriku. The two plains share sedimentary facies of river, estuary, and delta. At both sites, relative sea-level (RSL) from 10 to 9.0 ka estimated from altitude of intertidal deposits is significantly lower than the theoretical none-tectonic RSL. We interpret that this discrepancy is attributed to Holocene tectonic subsidence. Observed Holocene subsidence is consistent with 2011 coseismic and a century-long subsidence. This long-term subsidence possibly suggests that the southern Sanriku has been submerged by both the 2011 type coseismic and interseismic deformation on the 104 yr time-scale. A significant difference is their rates: long-term subsidence rate of ~1 mm/yr is slower than a century-long rate of 1-10 mm/yr. However, it may be accommodated with the recovery from the ongoing postseismic and continuous potential interseismic uplift. We thus argue that there is no reason to include tectonic contribution from unknown, different type megathrust earthquakes to form the southern Sanriku.

  9. Trickle-down boundary conditions in aeolian dune-field pattern formation

    NASA Astrophysics Data System (ADS)

    Ewing, R. C.; Kocurek, G.

    2015-12-01

    One the one hand, wind-blown dune-field patterns emerge within the overarching boundary conditions of climate, tectonics and eustasy implying the presence of these signals in the aeolian geomorphic and stratigraphic record. On the other hand, dune-field patterns are a poster-child of self-organization, in which autogenic processes give rise to patterned landscapes despite remarkable differences in the geologic setting (i.e., Earth, Mars and Titan). How important are climate, tectonics and eustasy in aeolian dune field pattern formation? Here we develop the hypothesis that, in terms of pattern development, dune fields evolve largely independent of the direct influence of 'system-scale' boundary conditions, such as climate, tectonics and eustasy. Rather, these boundary conditions set the stage for smaller-scale, faster-evolving 'event-scale' boundary conditions. This 'trickle-down' effect, in which system-scale boundary conditions indirectly influence the event scale boundary conditions provides the uniqueness and richness of dune-field patterned landscapes. The trickle-down effect means that the architecture of the stratigraphic record of dune-field pattern formation archives boundary conditions, which are spatially and temporally removed from the overarching geologic setting. In contrast, the presence of an aeolian stratigraphic record itself, reflects changes in system-scale boundary conditions that drive accumulation and preservation of aeolian strata.

  10. 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.

  11. Preservation of Paleoseismic and Paleogeodetic Records of mid to late Holocene Subduction Zone Earthquakes in Different Coastal Settings

    NASA Astrophysics Data System (ADS)

    Kelsey, H. M.; Horton, B.; Rubin, C. M.; Grand Pre, C.; Hawkes, A. D.; Dura, T.; Daryono, M.; Ladinsky, T.

    2009-12-01

    Dynamic variations in sea level and solid Earth properties along active subduction zones predetermine the duration and when paleoseismic and paleogeodetic records will be preserved in coastal regions. The most direct, reliable way to chronicle the history of past subduction zone earthquakes is through coastal stratigraphic sequences that preserve abrupt and gradual relative sea level changes caused by great subduction earthquake cycles. Specifically, paleoseismic timing and paleo geodetic determination of vertical displacement can be obtained through the application of litho-, bio- and chronostratigraphic analyses of selected coastal stratigraphic sequences. Such stratigraphic sequences are only preserved under a specific set of conditions wherein sea level rise, crustal loading, local crustal thickness and imposed strain accumulation and release from megathrust and upper plate faults and folds collectively conspire to provide a long-term, gradual relative sea level rise over millenia that span at least two or three subduction earthquake cycles. Given the conditions necessary to preserve stratigraphic sequences recording multiple great subduction earthquake cycles, it is not surprising that robust paleoseismic records from coastal marsh stratigraphies are rare. To illustrate the conditions under which coastal marshes preserve paleoseismic records of great subduction zone earthquakes, we present two sites with different combinations of sea level rise, crustal loading, crustal thickness and local tectonics. Although both sites preserve a paleoseismic record of subduction zone earthquakes, the length of the records and the specific time range of the records are notably different. The coastal, equatorial, island tropical setting in the Indian Ocean preserves tidal-marsh stratigraphic records of great subduction zone earthquakes in the time window 7-5 ka. In contrast, mid-latitude, North American, northeast Pacific coastal settings preserve tidal-marsh stratigraphic

  12. Redox Effects on Organic Matter Storage in Coastal Sediments During the Holocene: A Biomarker/Proxy Perspective

    NASA Astrophysics Data System (ADS)

    Bianchi, Thomas S.; Schreiner, Kathryn M.; Smith, Richard W.; Burdige, David J.; Woodard, Stella; Conley, Daniel J.

    2016-06-01

    Coastal margins play a significant role in the burial of organic matter (OM) on Earth. These margins vary considerably with respect to their efficiency in OM burial and to the amounts and periodicity of their OM delivery, depending in large part on whether they are passive or active margins. In the context of global warming, these coastal regions are expected to experience higher water temperatures, changes in riverine inputs of OM, and sea level rise. Low-oxygen conditions continue to expand around the globe in estuarine regions (i.e., hypoxic zones) and shelf regions (i.e., oxygen minimum zones), which will impact the amounts and sources of OM stored in these regions. In this review, we explore how these changes are impacting the storage of OM and the preservation of sedimentary biomarkers, used as proxies to reconstruct environmental change, in coastal margins.

  13. Natural and human controls of the Holocene evolution of the beach, aeolian sand and dunes of Caesarea (Israel)

    NASA Astrophysics Data System (ADS)

    Roskin, J.; Sivan, D.; Shtienberg, G.; Roskin, E.; Porat, N.; Bookman, R.

    2015-12-01

    The study focuses on the Holocene appearance, chronology and drivers of beach sand deposition and inland aeolian sand transport around the Roman-Byzantine ruins of Caesarea, Israel. Beach sand, sand sheets, nebkha, linear and transverse dunes as well as parabolic and transverse interdunes along two transects were sampled in the current study down to their substrate. Sixteen new optically stimulated luminescence ages cluster at ∼5.9-3.3 ka, ∼1.2-1.1 ka (800-900 AD) and ∼190-120 years ago (1825-1895 AD) indicating times of middle and late Holocene sand sheet depositions and historical dune stabilization. The first age cluster indicates that beach sand accumulated when rates of global sea level rise declined around 6-5 ka. Until ∼4 ka sand sheets encroached up to 2.5 km inland. Historical and archaeological evidence points to sand mobilization since the first century AD. Sand sheets dating to 1.2-1.1 ka, coevally found throughout the dunefield represent sand stabilization due to vegetation reestablishment attributed to gradual and fluctuating decline in human activity from the middle Early Islamic period until the 10th century. Historical and chronological evidence of the existence of transverse and coppice dunes from the 19th century suggest that dunes only formed in the last few centuries. The study illustrates the initial role of natural processes, in this case decline in global sea level rise and the primary and later role of fluctuating human activity upon coastal sand mobility. The study distinguishes between sand sheets and dunes and portrays them as sensors of environmental changes.

  14. A review of the chronologies and geomorphology of the aeolian landforms in the northwestern Negev dunefield (Israel)

    NASA Astrophysics Data System (ADS)

    Roskin, Joel

    2015-04-01

    The northwestern (NW) Negev Desert dunefield covering an area of only 1,300 km2, comprises the eastern end of the northern Sinai Peninsula - NW Negev erg and is probably the most densely dated dune body in the INQUA Dunes Atlas chronologic database. Over 230 luminescence ages (TL, IRSL, and mainly OSL) and radiocarbon dates have been retrieved over the past course of 20 years from calcic and sandy palaeosols serving as dune substrates, sand sheets, vegetated linear dunes (VLDs), fluvial deposits, and archaeological sites. Despite being from different deposit types and aeolian morphologies, and based on different methodologies, the chronologies usually show good compatibility. By reviewing and reassessing the significance of the Eastern Mediterranean INQUA Dunes Atlas chronologies, along with detailed stratigraphic, structural and geomorphologic data and understandings, the major, and possibly extreme, episodes of aeolian activity and stability are outlined. Repetitive chronostratigraphic sequences in VLDs indicate that this dune type, at least in the Negev, comprises a reliable recorder of main dune mobilization periods. This presentation demonstrates that certain combinations of research finds, using different OSL dating strategies and other regional and local late Quaternary records and in particular aeolian ones, are required assets for providing for acceptable local and regional palaeoclimatic interpretations. The distribution of the VLD chronologies points to rapid mobilization during the Heinrich 1 and Younger Dryas, characterized by powerful winds, though VLDs also form in late Holocene palaeoenvironments. Time slices illustrate the different sensitivities of the studied aeolian landforms to the source, availability, and supply of sediment; long- and short-term climate change, local human-induced environmental changes and also their joint effects, that enable evaluation of aeolian responses to future environmental and climate changes.

  15. Coastal response to accelerated sea-level rise (>4 mm/yr) based on early-mid Holocene coastal evolution in the northwestern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Anderson, J. B.; Rodriguez, A. B.; Simms, A.

    2009-12-01

    There is growing consensus that the rate of sea level rise by the end of this century will reach, and possibly exceed, 5 mm/yr. Predictions as to how sea-level rise will impact coasts often rely on passive inundation models that simply flood the coastal landscape. However, the geological record clearly shows that coastal response to past sea-level rise was more complex, mainly due to differences in sediment supply and subsidence. Ultimately, coastal submergence and erosion depend on whether coastal environments are capable of aggrading as fast as sea-level rises, and this is largely dependent on sediment supply and, in the case of wetlands, vegetation growth. It has been 7000 years since sea level was rising at a rate of 5 mm/yr in the northern Gulf of Mexico. After approximately 4000 cal yrs BP the rate of rise decreased to less than 1 mm/yr. The rate has more than doubled in historical time. An analysis of shoreline and bayline change in Texas and western Louisiana during the past 9000 years shows that coastal retreat was quite episodic, with episodes of widespread and pronounced change that lasted a few centuries. During these episodes, the larger bays of the region (Calcasieu Lake, Sabine Lake, Galveston Bay, Matagorda Bay and Corpus Christi Bay) experienced major re-organization of estuarine environments. Within the limits of radiocarbon precision (a few centuries due to poorly constrained regional carbon reservoir variations) these events appear to have been contemporaneous. This begs the question, where these events caused by short-lived increases in the rate of rise or do they reflect a threshold response of coastal systems to an overall rise that averaged 4.0 mm/yr? This was a time when the West Antarctic ice sheet was experiencing its final stages of retreat from the inner continental shelf and inland passages, which could have resulted in rapid sea-level events of a few decimeters, below the resolution of Gulf of Mexico sea-level curves. These results

  16. Amino acid racemization analysis (AAR) as a successful tool for dating Holocene coastal sediments: Stratigraphy of a barrier island spit (Southern Sylt/North Sea)

    NASA Astrophysics Data System (ADS)

    Tillmann, Tanja; Ziehe, Daniel

    2014-05-01

    Dating of Holocene sediments in shallow coastal areas of the German North Sea by conventional techniques is commonly problematic. In particular the marine reservoir effect of radiocarbon means that radiocarbon dating cannot be applied to sediments younger than about 400 years. Amino acid racemization dating (AAR) is a viable alternative for dating young sediments. The method is based on the determination of ratios of D and L amino acid enantiomers in organic matrices of biogenic carbonates. In this study we use AAR as a tool for dating Holocene barrier islands sediments. Based on an AAR derived chronological framework we develop a model of barrier spit accretion which describes the interaction between extreme events, fair weather coastal processes and sedimentary development that constrains the major episodes of barrier island evolution. The stratigraphy was defined using ground-penetrating radar (GPR) surveys complemented by sedimentological coring data. The stratigraphy is then conceptualised in a AAR chronostratigraphic framework to define a chronological order and allow the development of a stratigraphic model of the evolution of Southern Sylt. The AAR data provide high temporal resolution and have been used for dating stages of barrier spit accretion. The time lines are marked as storm surge generated erosion unconformities in the stratigraphic profile. Individual shells and shell fragments of Cerastoderma edule, Mya arenaria, Mytilus edulis and Scrobicularia plana have been accumulated by short-term storm events as shell layers associated with the erosion unconformities and have been dated by AAR. Time lines reveal that the barrier spit accretion occurred episodically, and is dependant on the provided rate of sand delivery. The general trend is that sequences young to the. South. The AAR derived time lines have been verified and correlated by historic maps and sea charts. It is apparent that spit enlargement at this site increased significantly during the

  17. Evolution of the siliciclastic-carbonate shelf system of the northern Kenyan coastal belt in response to Late Pleistocene-Holocene relative sea level changes

    NASA Astrophysics Data System (ADS)

    Accordi, Giovanni; Carbone, Federico

    2016-11-01

    A classification of depositional environments of the Lamu Archipelago is proposed based on a sedimentary facies analysis of unconsolidated and hard bottoms of the study area. The genesis of the siliciclastic-carbonate depositional pattern, typical of this East African region, is closely related both to the presence of a quartz-dominate Pleistocene riverine net-flooded during the Holocene sea level rise-and to the coeval development on the shallow shelf of a coral ecosystem producing vast skeletal sediments. The present facies pattern originates from the variable contribution in time and space of three sediment types: skeletal carbonate, quartz and palimpsest debris. The facies analysis allowed to distinguish 10 depositional facies and to differentiate them into three main types of substratum: soft bottom, reefal hard bottom and non-reefal hard bottom. These three types define both the loose facies typical of the channelized coastal belt and several facies of the shallow shelf. In the first, the amounts and textures of the stored sediment are strictly related to three major geomorphic types of substratum: sheltered mangal flat, shallow channel and deep channel. In the second and the third, a wide range of textures is related to coastal flats, benches, islets and emerging rocks. This modern facies pattern is implemented through a series of evolutionary phases: i-during the Last Interglacial Period, since isotope substage 5b, the shallow shelf-above -20 m-is permanently exposed for about 80 ka, with erosion, karstification and cuts of river channels through the shelf; ii-after the Last Glacial Maximum, when the sea level fell to about 110-115 m b.p.s.l. (below present sea level) at 18-17 ka BP, the sea level rose at -20 m for about 9 ka, flooding the shallow shelf area and gradually drowning the riverine net; iii-the maximum flooding of the coastal belt was reached at about 4.5 ka BP, when a gradual moisture reduction caused a decrease of siliciclastic sediment supply

  18. Holocene sedimentation and coastal wetlands response to rising sea level at the Aucilla river mouth, a low energy coast in the Big Bend area of Florida

    USGS Publications Warehouse

    Garrett, Connie; Hertler, Heidi; Hoenstine, Ronald; Highley, Brad

    1993-01-01

    The shallow dip of the Florida carbonate platform results in low wave energy on Florida ???Big Bend??? coasts. Therefore sedimentation is dominated by river-and tidal-hydrodynamics near the Aucilla River mouth. Where present, Holocene sediments are thin and unconformably overlie Oligocene-aged Suwannee Limestone. The oldest unlithified sediments include reworked carbonate rubble with clay and wood fragments (seven thousand years old or less, based on wood radio-carbon dating). Although this basal sequence is observed in most areas, the sediments that overlie it vary. Sediment sequences from the outer littoral to submarine environments include organic-rich sands, oyster biotherm remains, and cleaner sands with organic-filled burrows. Inner littoral (salt-marsh) sequences generally consist of sandy, fining-upwards sequences in which dry weights of fine-grained clastics and organic components increase up-sequence at similar rates. Offshore sediments preserve greatly attenuated fluvial and salt-marsh facies, if these facies are preserved at all. With sea-level rise, erosion can result from insufficient sediment supply and down-cutting by tidal currents (Dolotov, 1992; and Dalrymple et al., 1992). Dolotov (1992) attributes displacement of original coastal stratigraphy to insufficient sediments for beach profile maintenance, while Dalrymple et al. (1992) attribute erosional truncation (ravinement) or complete removal of portions of typical estuarine sequences to headward migration of tidal channels.

  19. late Pleistocene and Holocene pollen record from Laguna de las Trancas, northern coastal Santa Cruz County, California

    USGS Publications Warehouse

    Adam, David P.; Byrne, Roger; Luther, Edgar

    1981-01-01

    A 2.1-m core from Laguna de las Trancas, a marsh atop a landslide in northern Santa Cruz County, California, has yielded a pollen record for the period between about 30,000 B. P. and roughly 5000 B. P. Three pollen zones are recognized. The earliest is characterized by high frequencies of pine pollen and is correlated with a mid-Wisconsinan interstade of the mid-continent. The middle zone contains high frequencies of both pine and fir (Abies, probably A. grandis) pollen and is correlated with the last full glacial interval (upper Wisconsinan). The upper zone is dominated by redwood (Sequoia) pollen and represents latest Pleistocene to middle Holocene. The past few thousand years are not represented in the core. The pollen evidence indicates that during the full glacial period the mean annual temperature at the site was about 2°C to 3°C lower than it is today. We attribute this small difference to the stabilizing effect of marine upwelling on the temperature regime in the immediate vicinity of the coast. Precipitation may have been about 20 percent higher as a result of longer winter wet seasons.

  20. Marine water from mid-Holocene sea level highstand trapped in a coastal aquifer: Evidence from groundwater isotopes, and environmental significance.

    PubMed

    Lee, Stephen; Currell, Matthew; Cendón, Dioni I

    2016-02-15

    A multi-layered coastal aquifer in southeast Australia was assessed using environmental isotopes, to identify the origins of salinity and its links to palaeo-environmental setting. Spatial distribution of groundwater salinity (electrical conductivity values ranging from 0.395 to 56.1 mS/cm) was examined along the coastline along with geological, isotopic and chemical data. This allowed assessment of different salinity sources and emplacement mechanisms. Molar chloride/bromide ratios range from 619 to 1070 (621 to 705 in samples with EC >15 mS/cm), indicating salts are predominantly marine. Two distinct vertical salinity profiles were observed, one with increasing salinity with depth and another with saline shallow water overlying fresh groundwater. The saline shallow groundwater (EC=45.4 to 55.7 mS/cm) has somewhat marine-like stable isotope ratios (δ(18)O=-2.4 to -1.9 ‰) and radiocarbon activities indicative of middle Holocene emplacement (47.4 to 60.4pMC). This overlies fresher groundwater with late Pleistocene radiocarbon ages and meteoric stable isotopes (δ(18)O=-5.5 to -4.6‰). The configuration suggests surface inundation of the upper sediments by marine water during the mid-Holocene (c. 2-8 kyr BP), when sea level was 1-2m above today's level. Profiles of chloride, stable isotopes, and radiocarbon indicate mixing between this pre-modern marine water and fresh meteoric groundwater to varying degrees around the coastline. Mixing calculations using chloride and stable isotopes show that in addition to fresh-marine water mixing, some salinity is derived from transpiration by halophytic vegetation (e.g. mangroves). The δ(13)C ratios in saline water (-17.6 to -18.4‰) also have vegetation/organic matter signatures, consistent with emplacement by surface inundation and extensive interaction between vegetation and recharging groundwater. Saline shallow groundwater is preserved only in areas where low permeability sediments have slowed subsequent downwards

  1. Coastal lake sediments from the southern Cape, South Africa - Implications for sea level and climate variations during the Holocene

    NASA Astrophysics Data System (ADS)

    Wündsch, M.; Haberzettl, T.; Kirsten, K. L.; Meschner, S.; Frenzel, P.; Baade, J.; Daut, G.; Mäusbacher, R.; Kasper, T.; Quick, L. J.; Meadows, M. E.; Zabel, M.

    2015-12-01

    Within the RAIN project (Regional Archives for Integrated iNvestigations) interdisciplinary investigations on climate evolution and environmental change in southern Africa during the Late Quaternary are being conducted. For this purpose, spatial and temporal variations of the three major rainfall zones covering South Africa (winter-, summer- and year-round rainfall zone) are studied using both marine and terrestrial archives. Here we present results inferred from sediment records from lakes Groenvlei and Eilandvlei located on the southern Cape coast within the year-round rainfall zone. From Eilandvlei, a brackish lake that is connected to the Indian Ocean via an estuary, a 30.5 m sediment core was recovered. Reservoir-corrected radiocarbon ages reveal a continuous sedimentation and a maximum age of about 8,900 cal BP. This ultra-high-resolution record of environmental change during the Holocene represents a unique discovery for entire southern Africa. Geochemical data reveal different phases of marine and terrestrial sediment deposition throughout the covered time span. Hence, this record reflects changes in sea level, but also variations in terrestrial sediment transport and thus changing climatic conditions. The sediment core from Groenvlei, which today is isolated from the Indian Ocean, covers the past 4,200 cal BP. Sediments from this lake are predominantly composed of autochthonous carbonates. Mineralogical investigations reveal alternating deposition of calcite and aragonite/dolomite, pointing to variable Mg/Ca ratios and thus variations in lake water salinity. These changes can be linked to sea level variations as well as to changes in the precipitation/evaporation balance, and hence climate. Based on these results, the Groenvlei record reveals a decreasing marine influence and a trend from generally drier to wetter conditions within the last 4,200 yrs. Moreover, several layers of enhanced allochtonous input were detected in this record, which can be

  2. Response of surface processes to climatic change in the dunefields and Loess Plateau of North China during the late Quaternary

    USGS Publications Warehouse

    Lu, H.; Mason, J.A.; Stevens, T.; Zhou, Y.; Yi, S.; Miao, X.

    2011-01-01

    This paper draws on recent optically stimulated luminescence (OSL) dating to evaluate the long-held assumption that dust accumulation rates in the Loess Plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time, because both are controlled by the strength of the Asian monsoons and also possibly because the dunefields are proximal loess sources. The results show there is little evidence that high rates of loess accumulation coincided with well-dated episodes of extensive dune activity in the Mu Us, Otindag, and Horqin dunefields, at 11-8ka and 1-0ka. Explanations for the apparent lack of coupling include local variation in the trapping of dust and post-depositional preservation of the loess and dune sediments, in response to varying local environmental conditions. In addition, a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields. The results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale. The dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale, but the timing of late Quaternary dune activity, along with a variety of other evidence, indicates that moisture changes in many of the drylands of northern China may not be in phase with precipitation in core regions of the Asian monsoons. ?? 2011 John Wiley & Sons, Ltd.

  3. Sediment facies and Holocene deposition rate of near-coastal fluvial systems: An example from the Nobi Plain, Japan

    NASA Astrophysics Data System (ADS)

    Hori, Kazuaki; Usami, Shogo; Ueda, Hiroki

    2011-05-01

    Floodplains are a major component of present near-coastal fluvial systems that have evolved in response to postglacial changes in climate and sea level. Knowledge of sedimentary facies and deposition rates on a centennial to millennial time scale is required for considering floodplain evolution. Two cores, AP1 and AP2, were acquired from an abandoned channel of the Ibi River and its natural levee on the Nobi Plain, central Japan. Sediment facies analysis, electrical conductivity, and radiocarbon dating of borehole samples showed that in both cores organic-rich dark gray floodbasin mud overlies deltaic deposits dating to after approximately 3200 years calibrated radiocarbon age (cal BP) in relation to delta progradation. The accumulation of floodbasin mud continued at the both sites until about 400 cal BP. Around 400 cal BP, the mud was eroded by the overlying channel sand and gravel at AP1 and was covered by fine-grained natural levee deposits at AP2 with an abrupt contact. This timing is concordant with the historical record of avulsion of the Ibi River during the Keicho Era (AD 1596-1615). Averaged aggradation rates at the AP1 and AP2 sites were approximately 2.2 and 3.2 mm/yr, respectively. Faulting-related subsidence along the western edge of the plain has influenced these rates by creating accommodation. Averaged deposition rates differed greatly between the floodbasin and the levee, suggesting that rapid aggradation of the natural levee also occurred on a centennial to millennial scale. These empirical data may be useful for testing models of the architecture and evolution of near-coastal fluvial systems.

  4. Upper-plate deformation following megathrust earthquakes: Holocene slip along the El Yolki Fault in central Chile inferred from deformed coastal sediments

    NASA Astrophysics Data System (ADS)

    Hillemann, Christian; Melnick, Daniel; Jara-Muñoz, Julius; Strecker, Manfred R.

    2015-04-01

    Great subduction earthquakes are commonly accompanied by motion of upper-plate faults, either during the megathrust event or in the weeks to months that follow. One of the best documented examples of such coupled behavior is probably the 2010 Pichilemu earthquake sequence of central Chile with MW 6.9 and 7.0 events sourced by a shallow normal fault 11 days after the MW 8.8 Maule earthquake that originated offshore Chile. Similarly, normal faults ruptured the surface after the 2011 Tohoku earthquake in Japan, and additional examples may exist in other subduction environments. Static stress transfer on optimally oriented faults located at the periphery of high-slip sectors has been suggested as the trigger mechanism for these earthquakes following major plate-boundary earthquakes. Numerous normal and reverse faults have been mapped along the ~500-km-long rupture zone of the 2010 Maule earthquake, but post-seismic upper-plate seismicity was concentrated only at the Pichilemu normal fault, which is immediately to the north of the area where slip reached its maximum of 17 m. To gain insight into the relation between megathrust ruptures and associated motion of upper-plate faults, we studied the El Yolki Fault (ELYF), a normal fault located near the region of lowest megathrust slip in 2010. We attempted to obtain the slip rate of the ELYF integrating field mapping of Holocene coastal landforms and combined airborne and terrestrial LiDAR data. In addition, paleoseismological trenches were dug along the uplifted footwall block where marine lagoonal sediments were back-tilted and uplifted by inferred slip along the ELYF. The trenches reveal basal metamorphic rocks and overlying fluvial sediments into which a stepped sequence of four distinct, decimeter-scale scarps had been sculpted at successively higher positions above bedrock. These erosional scarps are covered by a sequence of onlapping silty and clayey organic-rich intertidal sediments. In turn, these units are

  5. Seismic or hydrodynamic control of rapid late-holocene sea-level rises in Southern coastal Oregon, USA?

    USGS Publications Warehouse

    Nelson, A.R.; Ota, Y.; Umitsu, M.; Kashima, K.; Matsushima, Y.

    1998-01-01

    Intertidal stratigraphy has been instrumental in demonstrating the hazard posed by great earthquakes at the Cascadia subduction zone, but inferring an earthquake history from interbedded sequences of peat and mud is complicated by many factors that influence sedimentation and relative sea-level change on both tectonic and nontectonic coasts. Rapid-to-sudden rises in relative sea level marked by sharp contacts between intertidal peat and overlying mud or sand may reflect coseismic coastal subsidence and tsunami deposition or, alternatively, nonseismic hydrodynamic changes in estuaries. Reconnaissance coring at 16 sites in the marshes fringing a narrow, protected tidal inlet of Coos Bay, supplemented by diatom and 14C analyses at four sites, reveals a stratigraphic record too fragmentary and ambiguous to distinguish seismic from hydrodynamic causes for more than three of the 10 rises in relative sea-level identified. Only three sharp contacts have the wide extent and evidence of substantial (>0.5 m) submergence that distinguish them from similar contacts produced by nonseismic processes. Correlation with stratigraphic sequences at other estuaries shows that the fringing marshes suddenly subsided and were partially buried by tsunami sand during a great plate-boundary earthquake about 300 years ago. Similar contacts were produced by earthquakes about 1500-1800 years ago, and perhaps about 2400-2700 years ago. Other earthquakes with substantially less subsidence may also have occurred, but evidence is too ambiguous to reconstruct a more complete history.

  6. Late Holocene glacial history of the Copper River Delta, coastal south-central Alaska, and controls on valley glacier fluctuations

    NASA Astrophysics Data System (ADS)

    Barclay, David J.; Yager, Elowyn M.; Graves, Jason; Kloczko, Michael; Calkin, Parker E.

    2013-12-01

    Fluctuations of four valley glaciers in coastal south-central Alaska are reconstructed for the past two millennia. Tree-ring crossdates on 216 glacially killed stumps and logs provide the primary age control, and are integrated with glacial stratigraphy, ages of living trees on extant landforms, and historic forefield photographs to constrain former ice margin positions. Sheridan Glacier shows four distinct phases of advance: in the 530s to c.640s in the First Millennium A.D., and the 1240s to 1280s, 1510s to 1700s, and c.1810s to 1860s during the Little Ice Age (LIA). The latter two LIA advances are also recorded on the forefields of nearby Scott, Sherman and Saddlebag glaciers. Comparison of the Sheridan record with other two-millennia long tree-ring constrained valley glacier histories from south-central Alaska and Switzerland shows the same four intervals of advance. These expansions were coeval with decreases in insolation, supporting solar irradiance as the primary pacemaker for centennial-scale fluctuations of mid-latitude valley glaciers prior to the 20th century. Volcanic aerosols, coupled atmospheric-oceanic systems, and local glacier-specific effects may be important to glacier fluctuations as supplemental forcing factors, for causing decadal-scale differences between regions, and as a climatic filter affecting the magnitude of advances.

  7. Late Holocene climate and land-use impacts on ecology and carbon cycling in Atlantic coastal plain tidal freshwater wetlands

    NASA Astrophysics Data System (ADS)

    Jones, M.; Bernhardt, C. E.

    2013-12-01

    Tidal freshwater wetlands are vulnerable to degradation from changing climate, land-use practices, and sea level. Their position between fully tidal and fully non-tidal ecosystems and sensitivity to minor fluctuations in salinity makes them ideal candidates to record the effects of climate and sea-level variability. These wetlands also act as a substantial carbon (C) sink, and paleoclimate studies provide important evidence not only on the long-term impact of perturbations on their ecological structure and function, but also on their ability to store C. Here we examine the late Holocene impacts of climate, land-use change, and sea level rise on four tidal freshwater wetlands in the Waccamaw River and Turkey Creek, South Carolina. A transect of four sites that range from an almost completely fresh forested swamp at the most upstream site to a higher salinity oligohaline marsh downstream. The two intermediate sites are forested swamps at different stages of degradation. We analyzed pollen assemblages, plant macrofossils, and carbon accumulation rates from sediment cores spanning the last ~1500-2000 years. Overall, higher rates of C accumulation are associated with woody swamp peat than with herbaceous peat, as determined from peat macrofossils and pollen assemblages. All sites show decreased C accumulation rates with the onset of the Medieval Climate Anomaly (MCA), which remained low through the Little Ice Age (LIA) (~1500 to 150 cal yr BP). These changes are accompanied by a switch from woody swamp peat to a graminoid-dominated peat lithology in the two uppermost forested swamp locations, as well as in the oligohaline marsh located farthest south along the transect. The switch from swamp to the modern oligohaline marsh during the MCA suggests that both sea level and land-use change permanently transformed the wetland. Rice cultivation beginning ~300 cal yr BP may be responsible for an apparent hiatus in several of the cores and may explain a Poaceae spike in the

  8. Holocene Depositional History of Shad Pond, a Hypersaline Coastal Lagoon, Eleuthera, Bahamas and Its Influence on Lucayan Occupation

    NASA Astrophysics Data System (ADS)

    Boush, L. E.; Fentress, S.; Conroy, M.; Cook, A.; Miseridina, D.; Buynevich, I. V.; Myrbo, A.; Brown, E. T.; Berman, M.; Gnivecki, P.; Kjellmark, E.; Savarese, M.; Brady, K.

    2013-12-01

    Shad Pond, an enclosed hypersaline lagoon on the southeastern tip of Eleuthera, Bahamas reveals a ~5000-year record of hurricane activity, as well as sea-level and climate change history. Three sediment cores recovered 1.04-2.54 m of sediment over bedrock along a transect perpendicular to shoreline. Sediment composition and grain size, loss on ignition, X-ray fluorescence (XRF) measurements of the cores along with dune transects and ground-penetrating radar (GPR) profiles adjacent to the lake provide a comprehensive dataset to interpret the history of this coastal basin. The sedimentary sequence was composed of alternating lithofacies that included microbial mats, sand, and peat. Laminated mats often alternated with sandy layers in thin to medium-bedded units. Two peat layers were found in the basal part of the shore-distal core (Site 1) between 1.82-2.40 m and 2.53-2.54 m and were separated by a 13-cm-thick gray mud layer. In general, organic matter and carbonate content tracked granulometry and composition in all cores. High-resolution XRF scans of Ca and Sr at Site 1 show elevated levels ~3,700 cal yBP, which correlate with the top of the peat layer, but these elemental concentrations vary at Site 3. XRF measurements of Fe indicate a dust flux that has been recorded regionally throughout the Caribbean. Dune transects and GPR profiles indicate a phased history of the pond, beginning with initial stages as an open lagoon dominated by red mangrove, with black mangrove and buttonwood also present. The lake likely closed at approximately 3,700 cal yBP indicated by the transition between the upper peat and microbial mat layers. This could have been due to increased storm events in a regime of rising sea level. Aeolian aggradation continued to heighten the barrier between the bedrock headlands to its present position. Hurricane overwash deposits punctuated the algal mat accumulation throughout this time period. Present-day hypersaline conditions sustain algal mats

  9. Definition and origin of the dune-field pattern at White Sands, New Mexico

    NASA Astrophysics Data System (ADS)

    Baitis, Elke; Kocurek, Gary; Smith, Virginia; Mohrig, David; Ewing, Ryan C.; Peyret, A.-P. B.

    2014-12-01

    A LiDAR-derived digital elevation model (DEM) of a representative portion of the White Sands Dune Field, New Mexico, allows for characterization of an unprecedented range of dune-field parameters and serves as a basis for pattern analysis. Dune-field parameters were measured and statistically analyzed for populations of dunes selected at random and occurring along transects. Populations sampled by these two different methods are comparable, but highlight the sensitivity of transect placement in a dune field that has pattern heterogeneity. Based upon coefficients of variation, pattern emerges at White Sands primarily because of a strong fabric of crestline orientation, and secondarily because of the regularity of spacing between dunes of similar shape as defined by sinuosity, height and length. Linear regression of dune parameters shows that dune geometric relationships vary primarily with crestline length, but there is little correlation between other parameters, including dune spacing and height. This result highlights the sensitivity of identifying topographic heterogeneity in a LiDAR-derived DEM, given that mean ratios conform to global averages. Stripping off the dunes in Matlab shows a terraced surface, which is interpreted to represent paleo-shorelines formed during relative still stands in the overall retreat of Lake Otero. Elevated bands of higher, more closely spaced dunes occur just leeward of the paleo-shorelines. A revised model for the White Sands Dune Field consists of the basinward progradation of successive dune-field segments. Each segment is associated with a paleo-shoreline, and consists of an upwind dune ridge, represented by the elevated bands, and a leeward dune field.

  10. Palaeoclimate interpretations of Late Pleistocene vegetated linear dune mobilization episodes: evidence from the northwestern Negev dunefield, Israel

    NASA Astrophysics Data System (ADS)

    Roskin, J.; Tsoar, H.; Porat, N.; Blumberg, D. G.

    2012-04-01

    The northern Sinai - northwestern (NW) Negev erg stretches east out of the Nile Delta that is believed to be the erg's sand source. The vegetated linear dune (VLD) field of the NW Negev Desert, situated at the downwind eastern end of the erg, constitutes an ideal setting for dating and interpreting its Late Quaternary dune encroachment episodes. This study builds upon the results of Roskin et al. (Age, origin and climatic controls on vegetated linear dunes in the northwestern Negev Desert (Israel), Quaternary Science Reviews 30 (2011), 1649-1674) that presented the stratigraphy of 35 sections and 97 optically stimulated luminescence (OSL) ages from the NW Negev dunefield. Here we analyze Late Pleistocene dune mobilizations and stabilizations and interpret their palaeoclimatic controls in light of regional and global dune ages, sediment records and proxies. While initial dune encroachment into, and stabilization in, the NW Negev took place during the Last Glacial Maximum (LGM) at ~23-18 ka, spatial and statistical analyses of the OSL dataset suggest that since the LGM, Negev dune activity was concentrated in two significant mobilization-stabilization episodes: a main episode at ~16-13.7 ka and a minor one at ~12.4-11.6 ka when the dunes reached their maximum spatial extent and stabilized. These episodes include rapid dune encroachment and accretion events and coincide with the Heinrich 1 and Younger Dryas cold events, respectively. The Late Pleistocene sand-transporting winds were characterized by a westerly direction that resulted in west-east VLD elongation. Dune mobilizations may have occurred in response to wintertime East Mediterranean cyclonic systems that brought storms of rainfall and strong winds. The rapid dune mobilization events and their concurrence with the Heinrich 1 and Younger Dryas cold events suggest a more global control. Despite the rainfall, the elongating VLDs were probably sparsely vegetated because of the high wind power; their stabilization

  11. Dinocysts and other palynomorphs from the Holocene record of the Adélie coastal margin, Antarctica (IODP Site U1357)

    NASA Astrophysics Data System (ADS)

    Hartman, Julian; Sangiorgi, Francesca; Bijl, Peter; Brinkhuis, Henk

    2016-04-01

    During International Ocean Drilling Program Expedition 318, about 170 meters of Holocene core have been retrieved from Site U1357, near the Adélie Coast, East-Antarctica. This core provides a high resolution marine record of Holocene climate variability close to the Antarctic margin. Palynomorphs in this core are extremely well-preserved due to the high sedimentation rates of diatom ooze. One of these exceptionally well-preserved finds is the first account of cysts of a sea-ice dwelling suessoid dinoflagellate (Polarella glacialis). Furthermore, a new species of dinoflagellate cyst, large amounts of tintinnid loricae, copepod remains, and various kinds of unknown/undescribed acritarch species have been found. Although the composition of the palynomorphs assemblage is highly variable throughout the record, this record potentially gives insight into ecological and/or environmental changes in a polynya-controlled environment since the last deglaciation. For example, the dinocyst assemblage seems to indicate that the sea-ice season was shorter in the early Holocene.

  12. Water management during climate change using aquifer storage and recovery of stormwater in a dunefield in western Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Lopez, O.; Stenchikov, G.; Missimer, T. M.

    2014-07-01

    An average of less than 50 mm yr-1 of rainfall occurs in the hyperarid region of central Western Saudi Arabia. Climate change is projected to create greater variation in rainfall accumulation with more intense rainfall and flood events and longer duration droughts. To manage climate change and variability in ephemeral stream basins, dams are being constructed across wadi channels to capture stormwater, but a large percentage of this stored water is lost to evaporation. A dam/reservoir system located in Wadi Al Murwani in Western Saudi Arabia was recently constructed and is expected to contain a maximum stored water volume of 150 million m3. A hydrologic assessment of a dunefield lying 45 km downstream was conducted to evaluate its potential use for aquifer storage and recovery of the reservoir water. A 110 m elevation difference between the base of the dam and the upper level of the dunefield occurs, allowing conveyance of the water from the reservoir to the dunefield storage site by gravity feed without pumping, making the recharge system extremely energy efficient. Aquifer storage and recovery coupled with dams would allow water management during extreme droughts and climate change and has widespread potential application in arid regions.

  13. Development of spatially diverse and complex dune-field patterns: Gran Desierto Dune Field, Sonora, Mexico

    USGS Publications Warehouse

    Beveridge, C.; Kocurek, G.; Ewing, R.C.; Lancaster, N.; Morthekai, P.; Singhvi, A.K.; Mahan, S.A.

    2006-01-01

    The pattern of dunes within the Gran Desierto of Sonora, Mexico, is both spatially diverse and complex. Identification of the pattern components from remote-sensing images, combined with statistical analysis of their measured parameters demonstrate that the composite pattern consists of separate populations of simple dune patterns. Age-bracketing by optically stimulated luminescence (OSL) indicates that the simple patterns represent relatively short-lived aeolian constructional events since ???25 ka. The simple dune patterns consist of: (i) late Pleistocene relict linear dunes; (ii) degraded crescentic dunes formed at ???12 ka; (iii) early Holocene western crescentic dunes; (iv) eastern crescentic dunes emplaced at ???7 ka; and (v) star dunes formed during the last 3 ka. Recognition of the simple patterns and their ages allows for the geomorphic backstripping of the composite pattern. Palaeowind reconstructions, based upon the rule of gross bedform-normal transport, are largely in agreement with regional proxy data. The sediment state over time for the Gran Desierto is one in which the sediment supply for aeolian constructional events is derived from previously stored sediment (Ancestral Colorado River sediment), and contemporaneous influx from the lower Colorado River valley and coastal influx from the Bahia del Adair inlet. Aeolian constructional events are triggered by climatic shifts to greater aridity, changes in the wind regime, and the development of a sediment supply. The rate of geomorphic change within the Gran Desierto is significantly greater than the rate of subsidence and burial of the accumulation surface upon which it rests. ?? 2006 The Authors. Journal compilation 2006 International Association of Sedimentologists.

  14. Coastal landscape evolution on the western margin of the Bahía Blanca Estuary (Argentina) mirrors a non-uniform sea-level fall after the mid-Holocene highstand

    NASA Astrophysics Data System (ADS)

    Pratolongo, Paula; Piovan, María Julia; Cuadrado, Diana G.; Gómez, Eduardo A.

    2016-11-01

    Sedimentary descriptions and radiocarbon ages from two cores obtained from coastal plains along the western margin of the Bahía Blanca Estuary (Argentina) were integrated with previous information on landscape patterns and plant associations to infer landscape evolution during the mid-to-late Holocene. The study area comprises at least two marine terraces of different elevations. The old marine plain (OMP), at an average elevation of 5 m above mean tidal level (MTL), is a nearly continuous flat surface. The Recent marine plain (RMP), 2 to 3 m above MTL, is a mosaic of topographic highs and elongated depressions that may correspond to former tidal channels. Mollusks at the base of the OMP core (site elevation 5.09 m above MTL), with ages between 5,660 ± 30 and 5,470 ± 30 years BP, indicate a subtidal setting near the inland limits of the marine ingression. The sandy bottom of the core is interpreted as the last stage of the transgressive phase, followed by a tight sequence of dark laminated muds topped by a thick layer of massive gray muds. The RMP core (site elevation 1.80 m above MTL) has a similar sedimentary sequence, but unconformities appear at lower elevations and the massive mud deposits are less developed. The thickness of the grayish mud layer is a major difference between the OMP and RMP cores, but deeper layers have similar ages, suggesting a common origin at the end of the transgressive phase. The overlying massive muds would correspond to rapid sedimentation during a high sea-level stillstand or slow regression. It is proposed that, after a rapid sea-level drop to about 3 m above MTL, a flat and continuous surface corresponding to the OMP emerged, and more recent coastal dynamics shaped the dissected landscape of the RMP. For the Bahía Blanca Estuary, smooth regressive trends have been proposed after the mid-Holocene highstand, but also stepped curves. A stillstand or slowly dropping sea level was described around 3,850 ± 100 years BP, as well as

  15. A mid-Holocene record of sediment dynamics and high resolution accretion rates in a coastal salt marsh from Northern California

    NASA Astrophysics Data System (ADS)

    Brown, L. N.; Holmquist, J. R.; MacDonald, G. M.

    2013-12-01

    Sediment accretion rates in coastal salt marshes are the critical determining factor in terms of ecosystem stability in the face of accelerated sea level rise (SLR), projected to rise by up to 1.4 m by 2100 in Southern California (National Research Council, 2012). However, high resolution studies of accretion rates in coastal salt marshes over the past several millennia have not yet been conducted for most of the US west coast. We collected multiple sediment records from small salt marshes surrounding Humboldt Bay, California. Due to this unique tectonic setting, many suspect cores from these marshes have evidence of coastal subsidence due to earthquake activity or large tsunami deposits (Jacoby et al., 1995). These records therefore are one of the best proxy measures for how salt marshes in California may respond to accelerated SLR. We analyzed all cores for magnetic susceptibility, % organic matter, and select cores for particle size. High resolution, millennial and centennial scale, radiocarbon dating for these sediment records reveals a detailed history of marsh accretion rates.

  16. Holocene climate change in Arctic Canada and Greenland

    NASA Astrophysics Data System (ADS)

    Briner, Jason P.; McKay, Nicholas P.; Axford, Yarrow; Bennike, Ole; Bradley, Raymond S.; de Vernal, Anne; Fisher, David; Francus, Pierre; Fréchette, Bianca; Gajewski, Konrad; Jennings, Anne; Kaufman, Darrell S.; Miller, Gifford; Rouston, Cody; Wagner, Bernd

    2016-09-01

    This synthesis paper summarizes published proxy climate evidence showing the spatial and temporal pattern of climate change through the Holocene in Arctic Canada and Greenland. Our synthesis includes 47 records from a recently published database of highly resolved Holocene paleoclimate time series from the Arctic (Sundqvist et al., 2014). We analyze the temperature histories represented by the database and compare them with paleoclimate and environmental information from 54 additional published records, mostly from datasets that did not fit the selection criteria for the Arctic Holocene database. Combined, we review evidence from a variety of proxy archives including glaciers (ice cores and glacial geomorphology), lake sediments, peat sequences, and coastal and deep-marine sediments. 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 sites). 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.

  17. AMS-dated mollusks in beach ridges and berms document Holocene sea-level and coastal changes in northeastern Kuwait Bay

    NASA Astrophysics Data System (ADS)

    Reinink-Smith, Linda M.

    2015-09-01

    In northeastern Kuwait, ancient beach ridges and associated berms are separated from the present shoreline by a 4-6 km-wide sabkha. A diverse mollusk fauna in the beach ridges attests to a former open marine environment. A total of 21 AMS dates were obtained in this study. Thirteen mollusk samples from beach ridges yielded AMS dates ranging from ~ 6990 cal yr BP in the southeast to ~ 3370 cal yr BP in the northwest, suggesting a southeast to northwest age progression during the Holocene transgression. In contrast, four samples from berms throughout the study area yielded AMS dates of 5195-3350 cal yr BP showing no age progression; these berms consist largely of Conomurex persicus gastropods that aggregated by storms during a highstand at ~ 5000-3500 cal yr BP. The berms are presently at ~ + 6 m above sea level, 2-3 m above the beach ridges. Human settlements were common on the ridge crests before and after the highstand. Regression to present-day sea level commenced after the highstand, which is when the sabkha began forming. A landward, marine-built terrace, which yielded AMS dates > 43,500 14C yr BP, probably formed during Marine Oxygen Isotope Stage 5e and hence is not genetically related to the beach ridges.

  18. Spectroscopy, morphometry, and photoclinometry of Titan's dunefields from Cassini/VIMS

    USGS Publications Warehouse

    Barnes, J.W.; Brown, R.H.; Soderblom, L.; Sotin, C.; Le, Mouelic S.; Rodriguez, S.; Jaumann, R.; Beyer, R.A.; Buratti, B.J.; Pitman, K.; Baines, K.H.; Clark, R.; Nicholson, P.

    2008-01-01

    Fine-resolution (500 m/pixel) Cassini Visual and Infrared Mapping Spectrometer (VIMS) T20 observations of Titan resolve that moon's sand dunes. The spectral variability in some dune regions shows that there are sand-free interdune areas, wherein VIMS spectra reveal the exposed dune substrate. The interdunes from T20 are, variously, materials that correspond to the equatorial bright, 5-??m-bright, and dark blue spectral units. Our observations show that an enigmatic "dark red" spectral unit seen in T5 in fact represents a macroscopic mixture with 5-??m-bright material and dunes as its spectral endmembers. Looking more broadly, similar mixtures of varying amounts of dune and interdune units of varying composition can explain the spectral and albedo variability within the dark brown dune global spectral unit that is associated with dunes. The presence of interdunes indicates that Titan's dunefields are both mature and recently active. The spectrum of the dune endmember reveals the sand to be composed of less water ice than the rest of Titan; various organics are consistent with the dunes' measured reflectivity. We measure a mean dune spacing of 2.1 km, and find that the dunes are oriented on the average in an east-west direction, but angling up to 10?? from parallel to the equator in specific cases. Where no interdunes are present, we determine the height of one set of dunes photoclinometrically to be between 30 and 70 m. These results pave the way for future exploration and interpretation of Titan's sand dunes. ?? 2007 Elsevier Inc. All rights reserved.

  19. Mid-Holocene Hemlock Decline in Eastern North America Linked with Phytophagous Insect Activity

    NASA Astrophysics Data System (ADS)

    Bhiry, Najat; Filion, Louise

    1996-05-01

    Macrofossil evidence indicates that the mid-Holocene hemlock [ Tsuga canadensisL. (Carr.)] decline that occurred over a wide area in eastern North America was associated with phytophagous insect activity. In situhemlock macrofossils and insect remains found in a paludified dunefield at the northern limit of hemlock testify that two defoliation events occurred at 4910 ± 90 and 4200 ± 100 yr B.P., respectively. The sharp coincidence of remains from hemlock needles with chewing damage typical of hemlock looper feeding, head capsules from the hemlock looper ( Lambdina fiscellaria) and the spruce budworm ( Choristoneura fumiferana), absence of hemlock fruiting remains, and tree-ring anomalies in fossil hemlocks that died prematurely (<165 yr) suggest that defoliation affected hemlock reproductive capacity and pollen productivity, or more likely caused mass mortality. Our findings indicate that defoliation can affect ecosystems for centuries, especially when long-lived tree species are involved.

  20. Mg/Ca, Sr/Ca, and stable isotopes in modern and Holocene Protothaca staminea shells from a northern California coastal upwelling region

    USGS Publications Warehouse

    Takesue, R.K.; VanGeen, A.

    2004-01-01

    This study explores the potential of intertidal Protothaca staminea shells as high-resolution geochemical archives of environmental change in a coastal upwelling region. Mg/Ca and Sr/Ca ratios were analyzed by excimer laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) at sub-weekly temporal resolution in shells growing ???1 mm per month. Growth patterns of a modern P. staminea shell from Humboldt Bay, California, collected in December 1999 made it possible to infer a lifespan from 1993 to 1998. Growth hiatuses in the shell may have excluded records of extreme events. Mg/Ca ratios appeared to be partly controlled by water temperature; the correlation coefficient between temperature and Mg/Ca was r = 0.71 in one of four growth increments. Significant year-to-year differences in the sensitivity of Mg/Ca to temperature in P. staminea could not be explained, however. Sr/Ca ratios appeared to be more closely related to shell growth rate. Oxygen isotopes, measured at 2-week temporal resolution in the same shell, did not show a clear relation to local temperature in summer, possibly because temperatures were higher and less variable at the King Salmon mudflat, where the shell was collected, than in the main channel of Humboldt Bay, where water properties were monitored. Negative shell ??13C values (<-0.5???) marked spring and summer coastal upwelling events. The Mg contents of P. staminea midden shells dated to ???3 ka and ???9 ka were significantly lower than in the modern shell. This may have resulted from degradation of a Mg-rich shell organic matrix and precluded quantitative interpretation of the older high-resolution records. Elevated ??13C values in the ???3 ka shell suggested that the individual grew in highly productive or stratified environment, such as a shallow coastal embayment or lagoon. Copyright ?? 2004 Elsevier Ltd.

  1. 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.

  2. Palaeoenvironmental reconstructions from linear dunefields: recent progress, current challenges and future directions

    NASA Astrophysics Data System (ADS)

    Telfer, M. W.; Hesse, P. P.

    2013-10-01

    This paper reviews recent progress in the use of linear dunes as ‘geoproxies' of late Quaternary environmental change, summarises the challenges facing their use, and explores some potential solutions to these challenges. Large areas of the swathes of linear dunes which occupy the continental interior of southern Africa, Australia, and parts of central Asia and southern America currently have limited or negligible aeolian activity. They have been recognised as offering potential information about past environments for more than a century, but only with the widespread application of luminescence dating during the 1990s did they realistically start to offer the prospect of being an extensive, dateable proxy of late Quaternary palaeoenvironments and, possibly, palaeoclimates. Dating aeolian dune sands with luminescence methods is generally (although not always) relatively straightforward. Over the past twenty years, a large number (>1000) of luminescence ages have been added to the global dataset, yet there has also been significant criticism of some of the rationale underpinning much of the interpretation of the records derived. At the landscape scale, developments of arguably equal importance have come from improved geomorphological understanding based on the wider availability of remotely-sensed data and the paradigm of dunefield evolution as a self-organising complex system. Current challenges are identified in three key regions: incomplete understanding of how the process geomorphology of linear dunes affect the accumulation and preservation of sediment, a lack of clarity regarding the temporal and spatial scale of the response in a dynamic environmental setting and uncertainty surrounding the drivers of changing rates of net accumulation. Solutions to these challenges lie within diverse research methodologies. Certainly, further field study is required, with improvement required in understanding system responses to changing environmental stimuli at scales from

  3. A 700 year record of combustion-derived pollution in northern Spain: tools to identify the Holocene/Anthropocene transition in coastal environments.

    PubMed

    Leorri, Eduardo; Mitra, Siddhartha; Irabien, María Jesús; Zimmerman, Andrew R; Blake, William H; Cearreta, Alejandro

    2014-02-01

    There is an uneven geographical distribution of historic records of atmospheric pollutants from SW Europe and those that exist are very limited in temporal extent. Alternative data source is required to understand temporal trends in human impacts on atmospheric pollution. Polycyclic aromatic hydrocarbons (PAHs), heavy metal content and stable Pb isotopic ratios in a sediment core from a salt marsh in northern Spain were used to reconstruct the regional history of contaminant inputs over the last 700 years. Pre-1800s concentrations of Pb and PAHs represented baseline concentrations, i.e. pre-Industrial, conditions. During the initial stages of the Industrial Revolution, 1800s to 1860s, PAH concentrations increased by a factor of about two above baseline levels in the sediment column. By the 1930s, PAH levels reached ca. 10 times pre-Industrial levels and, along with Pb, reached a peak at ca. 1975 CE. Since then, sedimentary PAH and Pb concentrations decreased significantly. A combination of PAH isomer and Pb stable isotope ratios suggests that the contaminant sources are regional, likely derived partially from wood, but mainly coal used by the metallurgic industry in the Basque country since the 1800s and until the 1970s when leaded petrol saw increased use. This chronology of regional atmosphere-derived pollution expands current southwest Europe emission records and shows coastal salt marsh sediments to be useful in reconstructing the Anthropocene.

  4. Coastal Evolution in a Mediterranean Microtidal Zone: Mid to Late Holocene Natural Dynamics and Human Management of the Castelló Lagoon, NE Spain

    PubMed Central

    Ejarque, Ana; Julià, Ramon; Reed, Jane M.; Mesquita-Joanes, Francesc; Marco-Barba, Javier; Riera, Santiago

    2016-01-01

    We present a palaeoenvironmental study of the Castelló lagoon (NE Spain), an important archive for understanding long-term interactions between dynamic littoral ecosystems and human management. Combining geochemistry, mineralogy, ostracods, diatoms, pollen, non-pollen palynomorphs, charcoal and archaeo-historical datasets we reconstruct: 1) the transition of the lagoon from a marine to a marginal environment between ~3150 cal BC to the 17th century AD; 2) fluctuations in salinity; and 3) natural and anthropogenic forces contributing to these changes. From the Late Neolithic to the Medieval period the lagoon ecosystem was driven by changing marine influence and the land was mainly exploited for grazing, with little evidence for impact on the natural woodland. Land-use exploitation adapted to natural coastal dynamics, with maximum marine flooding hampering agropastoral activities between ~1550 and ~150 cal BC. In contrast, societies actively controlled the lagoon dynamics and become a major agent of landscape transformation after the Medieval period. The removal of littoral woodlands after the 8th century was followed by the expansion of agrarian and industrial activities. Regional mining and smelting activities polluted the lagoon with heavy metals from the ~11th century onwards. The expansion of the milling industry and of agricultural lands led to the channelization of the river Muga into the lagoon after ~1250 cal AD. This caused its transformation into a freshwater lake, increased nutrient load, and the infilling and drainage of a great part of the lagoon. By tracking the shift towards an anthropogenically-controlled system around ~750 yr ago, this study points out Mediterranean lagoons as ancient and heavily-modified systems, with anthropogenic impacts and controls covering multi-centennial and even millennial timescales. Finally, we contributed to the future construction of reliable seashell-based chronologies in NE Spain by calibrating the Banyuls-sur-Mer

  5. Coastal Evolution in a Mediterranean Microtidal Zone: Mid to Late Holocene Natural Dynamics and Human Management of the Castelló Lagoon, NE Spain.

    PubMed

    Ejarque, Ana; Julià, Ramon; Reed, Jane M; Mesquita-Joanes, Francesc; Marco-Barba, Javier; Riera, Santiago

    2016-01-01

    We present a palaeoenvironmental study of the Castelló lagoon (NE Spain), an important archive for understanding long-term interactions between dynamic littoral ecosystems and human management. Combining geochemistry, mineralogy, ostracods, diatoms, pollen, non-pollen palynomorphs, charcoal and archaeo-historical datasets we reconstruct: 1) the transition of the lagoon from a marine to a marginal environment between ~3150 cal BC to the 17th century AD; 2) fluctuations in salinity; and 3) natural and anthropogenic forces contributing to these changes. From the Late Neolithic to the Medieval period the lagoon ecosystem was driven by changing marine influence and the land was mainly exploited for grazing, with little evidence for impact on the natural woodland. Land-use exploitation adapted to natural coastal dynamics, with maximum marine flooding hampering agropastoral activities between ~1550 and ~150 cal BC. In contrast, societies actively controlled the lagoon dynamics and become a major agent of landscape transformation after the Medieval period. The removal of littoral woodlands after the 8th century was followed by the expansion of agrarian and industrial activities. Regional mining and smelting activities polluted the lagoon with heavy metals from the ~11th century onwards. The expansion of the milling industry and of agricultural lands led to the channelization of the river Muga into the lagoon after ~1250 cal AD. This caused its transformation into a freshwater lake, increased nutrient load, and the infilling and drainage of a great part of the lagoon. By tracking the shift towards an anthropogenically-controlled system around ~750 yr ago, this study points out Mediterranean lagoons as ancient and heavily-modified systems, with anthropogenic impacts and controls covering multi-centennial and even millennial timescales. Finally, we contributed to the future construction of reliable seashell-based chronologies in NE Spain by calibrating the Banyuls-sur-Mer

  6. Linking restoration ecology with coastal dune restoration

    NASA Astrophysics Data System (ADS)

    Lithgow, D.; Martínez, M. L.; Gallego-Fernández, J. B.; Hesp, P. A.; Flores, P.; Gachuz, S.; Rodríguez-Revelo, N.; Jiménez-Orocio, O.; Mendoza-González, G.; Álvarez-Molina, L. L.

    2013-10-01

    Restoration and preservation of coastal dunes is urgently needed because of the increasingly rapid loss and degradation of these ecosystems because of many human activities. These activities alter natural processes and coastal dynamics, eliminate topographic variability, fragment, degrade or eliminate habitats, reduce diversity and threaten endemic species. The actions of coastal dune restoration that are already taking place span contrasting activities that range from revegetating and stabilizing the mobile substrate, to removing plant cover and increasing substrate mobility. Our goal was to review how the relative progress of the actions of coastal dune restoration has been assessed, according to the ecosystem attributes outlined by the Society of Ecological Restoration: namely, integrity, health and sustainability and that are derived from the ecological theory of succession. We reviewed the peer reviewed literature published since 1988 that is listed in the ISI Web of Science journals as well as additional references, such as key books. We exclusively focused on large coastal dune systems (such as transgressive and parabolic dunefields) located on natural or seminatural coasts. We found 150 articles that included "coastal dune", "restoration" and "revegetation" in areas such as title, keywords and abstract. From these, 67 dealt specifically with coastal dune restoration. Most of the studies were performed in the USA, The Netherlands and South Africa, during the last two decades. Restoration success has been assessed directly and indirectly by measuring one or a few ecosystem variables. Some ecosystem attributes have been monitored more frequently (ecosystem integrity) than others (ecosystem health and sustainability). Finally, it is important to consider that ecological succession is a desirable approach in restoration actions. Natural dynamics and disturbances should be considered as part of the restored system, to improve ecosystem integrity, health and

  7. A linear dune dam - a unique late Pleistocene aeolian-fluvial archive bordering the northwestern Negev Desert dunefield, Israel

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Bookman, Revital; Friesem, David; Vardi, Jacob

    2016-04-01

    Interactions between aeolian and fluvial processes, known as aeolian-fluvial (A-F) interactions, play a fundamental role in shaping the surface of the Earth especially in arid zones. The blocking of wadis by dunes (dune-damming) is an A-F interaction that is perceived to be an archive of periods of aeolian 'superiority' on fluvial transport power and has had a strong impact on arid landscapes and prehistoric man since the late Quaternary. The southern fringes of the northwestern Negev dunefield are lined with discontinuous surfaces of light-colored, playa-like, low-energy, fine-grained fluvial deposits (LFFDs). Abundant Epipalaeolithic camp sites mainly border the LFFDs. The LFFDs are understood to be reworked loess-like sediment deposited in short-lived shallow water bodies during the late Pleistocene. These developed adjacently upstream of hypothesized dune dams of wadis that drain the Negev highlands. However, no dune dam structures by the LFFDs have been explicitly identified or analyzed. This paper presents for the first time the morphology, stratigraphy and sedimentology of a hypothesized dune dam. The studied linear-like dune dam structure extends west-east for several hundred meters, has an asymmetric cross-section and is comprised of two segments. In the west, the structure is 3-5 m high, 80 m wide, with a steep southern slope, and is covered by pebbles. Here, its morphology and orientation resembles the prevailing vegetated linear dunes (VLDs) of the adjacent dunefield though its slope angles differ from VLDs. To the south of the structure extends a thick LFFD sequence. In the east the structure flattens and is covered by nebkhas with its southern edge overlapped by LFFD units. The structures' stratigraphy is found to be comprised of a thick LFFD base, overlaid by aeolian and fluvially reworked sand, a thin middle LFFD unit, and a crest comprised of LFFDs, fluvial sand and pebbles. Carbonate contents and particle size distributions of the sediments easily

  8. Facies characterization and sequential evolution of an ancient offshore dunefield in a semi-enclosed sea: Neuquén Basin, Argentina

    NASA Astrophysics Data System (ADS)

    Veiga, Gonzalo D.; Schwarz, Ernesto

    2016-08-01

    This study analyses a 30-m-thick, sand-dominated succession intercalated between offshore mudstones in the Lower Cretaceous record of the Neuquén Basin, Argentina, defining facies associated with unidirectional currents as sand dunes (simple and compound), rippled sand sheets and heterolithic sheets. These facies associations are related to the development of an offshore, forward-accreting dunefield developed as a response to the onset of a tidal-transport system. The reported stratigraphic record results from the combination of the gradual downcurrent decrease of the current speed together with the long-term climbing of the entire system. Maximum amplification of the tidal effect associated with incoming oceanic tides to this epicontinental sea would develop at the time of more efficient connection between the basin and the open ocean. Thus, the onset of the offshore tidal system approximately corresponds to the time of maximum flooding conditions (or immediately after). The short-term evolution of the tidal-transport system is more complex and characterized by the vertical stacking of small-scale cycles defined by the alternation of episodes of construction and destruction of the dunefield. The development of these cycles could be the response to changes in tidal current speed and transport capacity.

  9. The Holocene temperature conundrum.

    PubMed

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

    2014-08-26

    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.

  10. 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.

  11. Holocene aridification of India

    USGS Publications Warehouse

    Ponton, C.; Giosan, L.; Eglinton, T.I.; Fuller, D.Q.; Johnson, J.E.; Kumar, P.; Collett, T.S.

    2012-01-01

    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. Copyright 2012 by the American Geophysical Union.

  12. Holocene estuary development in the Algarve Region (Southern Portugal)

    NASA Astrophysics Data System (ADS)

    Schneider, Heike; Höfer, Dana; Trog, Carmen; Hempel, Rita; Daut, Gerhard; Mäusbacher, Roland

    2010-05-01

    Former coastal estuaries in the Algarve region of South Portugal are used for reconstruction coastal evolution since first marine transgression processes at about 8.000 years before. The sediments of these archives allow high resolution analyses of geochemical and palynological signals. Drillings in different lagoons of the Algarve region contain the sequences from the fluvial sediments during the early Holocene, marine transgression facies during the middle Holocene and the marine/fluvial sediment deposits until present. The results of the sedimentological, geochemical and palynological analyses show that each estuary developed differently, depending on the morphology of the paleovalley, environmental conditions and especially the influence of the sea and the formation of barrier systems. The estuaries were flooded between 7500 and 5500 cal a BP by sea level rise and were almost completely filled by sediment by the beginning of the Roman occupation (226 y BC / 2176 cal a BP). A clear change in sedimentological processes is evident in the estuaries between 5500 and 3000 cal a BP and is interpreted as a result of high energy events such as storms or tsunamis (Schneider et al. 2009, Hilbich et al. 2008 ). Palynological as well as archaeological investigations show distinct anthropogenic influences since 3500 cal. BP by increasing values in maquies, cereals and open land communities. References Hilbich, C., Mügler, I., Daut, G., Frenzel, P., van der Borg, K., Mäusbacher, R. (2008): Reconstruction of the depositional history of the former coastal lagoon of Vilamoura (Algarve, Portugal): A sedimentological, microfaunal and geophysical approach.- Journal of Coastal Research 24(2B), 83-91. Schneider, H., Höfer, D., Trog, C., Busch, S., Schneider, M., Baade, J., Daut, G. & R. Mäusbacher (2009): Holocene estuary development in the Algarve Region (Southern Portugal) - A reconstruction of sedimentological and ecological evolution. - Quaternary International (In Press

  13. Tropical Peat and Peatland Development in the Floodplains of the Greater Pamba Basin, South-Western India during the Holocene

    PubMed Central

    Padmalal, Damodaran; Limaye, Ruta B.; S., Vishnu Mohan; Jennerjahn, Tim; Gamre, Pradeep G.

    2016-01-01

    Holocene sequences in the humid tropical region of Kerala, South-western (SW) India have preserved abundance of organic—rich sediments in the form of peat and its rapid development in a narrow time frame towards Middle Holocene has been found to be significant. The sub—coastal areas and flood plains of the Greater Pamba Basin have provided palaeorecords of peat indicating that the deposits are essentially formed within freshwater. The combination of factors like stabilized sea level and its subsequent fall since the Middle Holocene, topographic relief and climatic conditions led to rapid peat accumulation across the coastal lowlands. The high rainfall and massive floods coupled with a rising sea level must have inundated > 75% of the coastal plain land converting it into a veritable lagoon—lake system that eventually led to abrupt termination of the forest ecosystem and also converted the floodplains into peatland where accumulation of peat almost to 2.0–3.0 m thickness in coastal lowlands and river basins during the shorter interval in the Middle Holocene. Vast areas of the coastal plains of Kerala have been converted into carbon rich peatland during the Middle Holocene and transforming the entire coastal stretch and associated landforms as one of the relatively youngest peatlands in the extreme southern tip of India. Unlike the uninterrupted formation of peatlands of considerable extent during the Holocene in Southeast Asia, the south Peninsular Indian region has restricted and short intervals of peatlands in the floodplains and coastal lowlands. Such a scenario is attributed to the topographic relief of the terrain and the prevailing hydrological regimes and environmental conditions as a consequence of monsoon variability since Middle Holocene in SW India. Considering the tropical coastal lowlands and associated peatlands are excellent repositories of carbon, they are very important for regional carbon cycling and habitat diversity. The alarming rate of

  14. Tropical Peat and Peatland Development in the Floodplains of the Greater Pamba Basin, South-Western India during the Holocene.

    PubMed

    Kumaran, Navnith K P; Padmalal, Damodaran; Limaye, Ruta B; S, Vishnu Mohan; Jennerjahn, Tim; Gamre, Pradeep G

    2016-01-01

    Holocene sequences in the humid tropical region of Kerala, South-western (SW) India have preserved abundance of organic-rich sediments in the form of peat and its rapid development in a narrow time frame towards Middle Holocene has been found to be significant. The sub-coastal areas and flood plains of the Greater Pamba Basin have provided palaeorecords of peat indicating that the deposits are essentially formed within freshwater. The combination of factors like stabilized sea level and its subsequent fall since the Middle Holocene, topographic relief and climatic conditions led to rapid peat accumulation across the coastal lowlands. The high rainfall and massive floods coupled with a rising sea level must have inundated > 75% of the coastal plain land converting it into a veritable lagoon-lake system that eventually led to abrupt termination of the forest ecosystem and also converted the floodplains into peatland where accumulation of peat almost to 2.0-3.0 m thickness in coastal lowlands and river basins during the shorter interval in the Middle Holocene. Vast areas of the coastal plains of Kerala have been converted into carbon rich peatland during the Middle Holocene and transforming the entire coastal stretch and associated landforms as one of the relatively youngest peatlands in the extreme southern tip of India. Unlike the uninterrupted formation of peatlands of considerable extent during the Holocene in Southeast Asia, the south Peninsular Indian region has restricted and short intervals of peatlands in the floodplains and coastal lowlands. Such a scenario is attributed to the topographic relief of the terrain and the prevailing hydrological regimes and environmental conditions as a consequence of monsoon variability since Middle Holocene in SW India. Considering the tropical coastal lowlands and associated peatlands are excellent repositories of carbon, they are very important for regional carbon cycling and habitat diversity. The alarming rate of land

  15. Paleoshoreline record of relative Holocene sea levels on Pacific islands

    NASA Astrophysics Data System (ADS)

    Dickinson, William R.

    2001-11-01

    -oceanic island groups of both the northwestern and southwestern Pacific Ocean followed close on the heels of the mid-Holocene sea-level highstand, and took advantage of newly attractive coastal environments engendered by sea-level drawdown. The effects of the mid-Holocene highstand were modified to varying degrees in different island groups by geodynamic uplift or subsidence.

  16. Photo-Geomorphology of Coastal Landforms, Cat Island, Bahamas. Volume II,

    DTIC Science & Technology

    The report provides the aerial imagery used in the analysis of the coastal landforms of Cat Island in the east-central Bahama Islands. Interpretive...published volume Coastal Landform of Cat Island, Bahamas: A Study of Holocene Accretionary Topography and Sea-Level Change but may also serve as an

  17. Coastal sedimentation

    NASA Technical Reports Server (NTRS)

    Schubel, J. R.

    1980-01-01

    Several important coastal sedimentation problems are identified. Application of existing or anticipated remote sensing techniques to examine these problems is considered. Specifically, coastal fine particle sediment systems, floods and hy hurricanes and sedimentation f of coastal systems, routes and rates of sediment transport on continental shelves, and dredging and dredged material disposal are discussed.

  18. 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.

  19. 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

  20. Coastal Prairie

    USGS Publications Warehouse

    ,

    2000-01-01

    The coastal prairie, located along the coastal plain of southwestern Louisiana and southcentral Texas, is the southernmost tip of the tallgrass prairie ecosystem so prevalent in the Midwest. The coastal prairie ecosystem once covered as much as 3.8 million ha (9 million acres); today, more than 99% of this land has been lost to agriculture, range improvement, and urbanization. The remainder is highly fragmented and severely threatened by invasions of exotic species and urban sprawl. In Louisiana, the former 1 million ha of coastal prairie have now been reduced to about 100 ha. In Texas, only about 100,000 ha of coastal prairie remain intact.

  1. Reconstruction of Holocene Seismic Events Along Kamchatka's Pacific Coast

    NASA Astrophysics Data System (ADS)

    Pinegina, T.; Bourgeois, J.

    2004-12-01

    Since 1995 we have been conducting detailed neotectonic and paleoseismological field studies of the Holocene at more than 15 localities along the east coast of Kamchatka. Specific methods of these investigations include 1) application of tephra chronology and tephra stratigraphy for dating and correlation of various types of coastal deposits and landforms; 2) study of paleotsunami deposits in order to determine their ages and recurrence rate and to estimate the magnitude of large tsunamis and tsunamigenic earthquakes along the Kurile-Kamchatka subduction zone and north of the latter during Holocene time; 3) analysis of the geologic structure, age, and modern and paleo-topography of marine terraces and beach ridges in order to determine the direction and scale of seismotectonic movements over different time intervals; and 4) identification and dating of inferred seismogenic landslides along the coast. Eastern Kamchatka's short history (since about 1730 A.D.) includes many large and several great earthquakes, although historical coverage of these events is scarce because of both low population density, and also military secrecy. Nevertheless, we can use historical earthquakes and tsunami deposits as benchmarks for pre-historic events. Moreover, our studies have helped elucidate historic cases, including co-seismic deformation, tsunami runup, and tsunami source mechanism. As a result of these studies we have reconstructed key events in coastal evolution during the Holocene, and determined the ages of marine accumulative landforms on various segments of the coast. A combination of all our data enables us to get an idea about spatial and temporal distribution of strong subduction-type earthquakes along the Kuril-Kamchatka trench and 'non-subduction' earthquakes north of the trench terminus.

  2. 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.

  3. A Holocene Sediment Record From Lake Elsinore, Southern California: Evidence for Relative Lake Level Change and the Onset of ENSO.

    NASA Astrophysics Data System (ADS)

    Kirby, M. E.; Lund, S. P.; Poulsen, C. J.

    2003-12-01

    There are very few complete terrestrial, Holocene paleoclimate records from coastal southwestern North America. Lake Elsinore, located 120km southeast of Los Angeles, represents one of the only natural, non-playa lakes in the region. Furthermore, it is well documented that coastal southwestern North America is highly sensitive to changes in atmospheric circulation and its affect on regional hydrodynamics. As shown by Kirby et al. (in press), modern lake levels at Lake Elsinore respond directly to total annual precipitation, particularly winter season amounts. The lake is also located along the eastern Pacific Ocean where changes in ocean circulation and its thermal structure modulate the overlying atmosphere, and thus the adjacent continental climate. Here, we present two 7 meter sediment core records from Lake Elsinore spanning the entire Holocene. Although the cores are from the lake's littoral zone, they show surprisingly complete records with very little lithologic evidence for major hiatuses. A combination of sedimentological analyses (e.g., mass magnetic susceptibility (CHI); total percent carbonate; total organic matter) and lithologic descriptions provide insight to lake dynamics over the Holocene. Using the historical calibration between magnetic susceptibility and relative lake level (i.e., high lake levels = high CHI values and vice versa) from Kirby et al. (in press), we developed a first-order estimate of Holocene relative lake levels for Lake Elsinore. The historic calibration is extrapolated through the sediment record based on the assumption that, like today, first order lake level change is directly related to precipitation amount. Both total percent carbonate and total organic matter support our historical calibration between CHI and lake level. Our data suggest a relative increase in lake levels during the mid-Holocene (ca. 8,000 cal yr BP) and through to the present day. From this observation, we hypothesize that regional hydrology as linked to

  4. Holocene Tectonic and Sedimentary Evolution of Coastal San Diego

    NASA Astrophysics Data System (ADS)

    Maloney, J. M.; Driscoll, N. W.; Brothers, D. S.; Babcock, J. M.; Kent, G.

    2010-12-01

    The shelf and nearshore region of San Diego, California, between La Jolla cove in the north and the U.S.- Mexico border in the south, is an important ecological and economic resource. It contains two of the largest kelp forests in southern California and lies offshore miles of popular beaches. Understanding the interplay between tectonic and sedimentary processes in this area is critical because it will allow us to assess how other forcing functions such as the rapid sea level rise (2 - 3 mm/yr) and predicted climate change associated with global warming are impacting the kelp and nearshore environments. The fault architecture and sedimentary deposits offshore San Diego have been mapped using high-resolution seismic CHIRP profiling. The mapped area lies within the inner California Continental Borderland (CCB), which is characterized by a system of basins and ridges and extensive strike-slip faulting. The CHIRP data clearly images several splays of the Coronado Bank Fault Zone (CBFZ), a major fault in the area, which show recent activity in the upper 30 m of sediment with the most recent deformation at ~4 m below seafloor. Several sediment packages as deep as 50 m below the seafloor are imaged and place important constraints on tectonic deformation and sediment dispersal in the region as well as the earthquake recurrence interval on the CBFZ. Exposed and buried wavecut terraces identified on numerous CHIRP profiles, which can be correlated to terraces mapped regionally, provide insight into tectonic uplift rates and sea-level fluctuations. Finally, the extensive kelp forests offshore Mount Soledad and Point Loma occur where hardgrounds are exposed at the seafloor as a consequence of tectonic uplift. High resolution mapping offshore San Diego is providing new insight into the complex interplay between tectonics, sedimentation, and biology in this ecologically diverse region.

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

    NASA Astrophysics Data System (ADS)

    Curry, Brandon; Henne, Paul D.; Mesquita-Joanes, Francesc; Marrone, Federico; Pieri, Valentina; La Mantia, Tommaso; Calò, Camilla; Tinner, Willy

    2016-10-01

    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 to increased Greco

  6. Holocene evolution of Itapeva Lake, Rio Grande do Sul, Brazil: Palynomorphs C org, N, and S records

    NASA Astrophysics Data System (ADS)

    Meyer, Karin Elise Bohns; Reichhart, Karin; Ashraf, Abdul Rahman; Marques-Toigo, Marleni; Mosbrugger, Volker

    2005-06-01

    Holocene coastal environmental changes are interpreted from a 590 cm long core taken from Itapeva Lake in the northern coastal plain, Rio Grande do Sul, Brazil. The sediment core is radiocarbon dated at 211 cm depth (6460±40 yr B.P.) and studied by geochemistry and palynomorph analyses. The Pleistocene-Holocene boundary is predicted at the top of a glauconitic sand layer at 330 cm depth. On the basis of C org, N, S, and palynomorph data, it is possible to distinguish four zones related to the Holocene transgression-regression cycle, as well as proxies for the salinity trends and organic matter source. The start of Zone 1 represents the oldest Holocene sedimentary record in the core. Palynomorphs reveal a marsh environment with a freshwater influence. In Zone 2, Operculoclinium centrocarpum and high S values indicate brackish water and reflect a Holocene sea-level rise related to the postglacial marine transgression. The high amount of Cyperaceae pollen grains and a significant C org increase in Zone 3 indicate a typical marsh environment with episodes of marine water that reflect a regression phase. Salvinia natans (L) All. and Cyperaceae pollen grains are the most significant palynomorphs in Zone 4, which characterizes a freshwater marsh.

  7. Recurrence of postseismic coastal uplift, Kuril subduction zone, Japan

    USGS Publications Warehouse

    Kelsey, H.; Satake, K.; Sawai, Y.; Sherrod, B.; Shimokawa, K.; Shishikura, M.

    2006-01-01

    Coastal stratigraphy of eastern Hokkaido indicates that decimeters of coastal uplitt occurred repeatedly m the late Holocene. Employing radiocarbon dating and tephrochronology, we identify along a 100 km length of the Kuril subduction zone six uplift events since ???2,800 years B.P. Uplift events occur at the same frequency as unusually high tsunamis. Each coastal uplift event, which occurs on average every 500 years, is the product of decade-long post seismic deep slip on the down dip extension of the seismogenic plate boundary following an offshore multi-segment earthquake that generates unusually high tsunamis. Copyright 2006 by the American Geophysical Union.

  8. 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

    The availibility of terrestrial records of Holocene palaeoenvironmental changes in eastern Siberia still is quite limited, compared to other regions on the northern hemisphere. In particular, the Kamchatka Peninsula as an important climate-sensitive region is very underrepresented. Situated at the border of northeastern Eurasia, the maritime-influenced terrestrial setting of Kamchatka offers the potential to pinpoint connections of environmental changes between the periglacial and highly continental landmasses of eastern Siberia and the sub-Arctic Pacific Ocean and Sea of Okhotsk. The study region lies at the eastern end-loop of the global thermohaline ocean conveyor belt and is strongly affected by atmospheric teleconnections. Volcanic, tectonic, and glacial processes overprint palaeoenvironmental changes in addition to primary climate forcing. In order to widen our understanding of plaeoclimate dynamics on Kamchatka, sediment cores from different lake systems and peat sections were recovered and analysed by a multi-proxy approach, using sedimentological and geochemical data as well as fossil bioindicators, such as diatoms, pollen, and chironomids. Chronostratigraphy of the studied records was achieved through radiocarbon dating and tephrostratigraphy. Sediment cores with complete Holocene sedimentary sequences were retrieved from Lake Sokoch, an up to six metre deep lake of proglacial origin, situated at the treeline in the Ganalsky Ridge of southern central Kamchatka (53°15,13'N, 157°45.49' E, 495 m a.s.l.). Lacustrine sediment records of mid- to late Holocene age were also recovered from the up to 30 m deep Two-Yurts Lake, which occupies a former proglacial basin at the eastern flank of the Central Kamchatka Mountain Chain, the Sredinny Ridge (56°49.6'N, 160°06.9'E, 275 m a.s.l.). In addition to sediment coring in the open and deep Two-Yurts Lake, sediment records were also recovered from peat sections and small isolated forest lakes to compare

  9. Holocene climate of New England

    NASA Astrophysics Data System (ADS)

    Davis, Margaret B.; Spear, Ray W.; Shane, Linda C. K.

    1980-09-01

    Stratigraphic studies of pollen and macrofossils from six sites at different elevations in the White Mountains of New Hampshire demonstrate changes in the distributions of four coniferous tree species during the Holocene. Two species presently confined to low elevations extended farther up the mountain slopes during the early Holocene: white pine grew 350 m above its present limit beginning 9000 yr B.P., while hemlock grew 300-400 m above its present limit soon after the species immigrated to the region 7000 yr. B.P. Hemlock disappeared from the highest sites about 5000 yr B.P., but both species persisted at sites 50-350 m above their present limits until the Little Ice Age began a few centuries ago. The history of the two main high-elevation conifers is more difficult to interpret. Spruce and fir first occur near their present upper limits 9000 or 10,000 yr B.P. Fir persisted in abundance at elevations similar to those where it occurs today throughout the Holocene, while spruce became infrequent at all elevations from the beginning of the Holocene until 2000 yr B.P. These facts suggest a more complex series of changes than a mere upward shift of the modern environmental gradient. Nevertheless, we conclude that the minimum climatic change which would explain the upward extensions of hemlock and white pine is a rise in temperature, perhaps as much as 2°C. The interval of maximum warmth started 9000 yr B.P. and lasted at least until 5000 yr B.P., correlative with the Prairie Period in Minnesota.

  10. 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

  11. Mid-Holocene paleoceanographic conditions in the Limfjord region from gastropod (Littorina littorea) oxygen and carbon isotopes

    NASA Astrophysics Data System (ADS)

    Burman, J.; Schmitz, B.

    2003-04-01

    Stable oxygen and carbon isotope intrashell transects of common intertidal gastropods Littorina littorea have been used to reconstruct environmental conditions in the Limfjord region during the mid-Holocene (late Atlantic time). The subfossil specimens studied are from the excavated Stone Age Kitchenmidden in Ertebølle, northern Denmark, dated between 5970±95 to 5070±90 B.P. In addition recent specimens were studied from different coastal localities within the Limfjord, along a salinity gradient from the west to east. These modern shells were used as control samples, in order to construct an oceanographic model for the Limfjord, in which the seasonal isotopic range from the Littorina subfossils could be interpreted. The coastal marine climate in the Ertebølle region during the mid-Holocene indicates summer-SST close to 22^oC and 4-5 ppm reduced salinity compared to fully marine conditions. The mid-Holocene central Limfjord can be described as a coastal area, which experienced similar salinity conditions (c. 30.5 PSU) that prevail in the western part (Odden area) today. In terms of summer-SST as compared with a 10-year average (1989-1998) for the Limfjord region, temperatures were 2-3^oC above recent climatic settings. These results point towards a mid-Holocene Limfjord in contact with the North Sea/Skagerrak with possibly more pronounced water exchange with the North Sea than today.

  12. Holocene evolution of the western Orinoco Delta, Venezuela

    USGS Publications Warehouse

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

    2003-01-01

    The pristine nature of the Orinoco Delta of eastern Venezuela provides unique opportunities to study the geologic processes and environments of a major tropical delta. Remote-sensing images, shallow cores, and radiocarbon-dating of organic remains form the basis for describing deltaic environments and interpreting the Holocene history of the delta. The Orinoco Delta can be subdivided into two major sectors. The southeast sector is dominated by the Rio Grande-the principal distributary-and complex networks of anastomosing fluvial and tidal channels. The abundance of siliciclastic deposits suggests that fluvial processes such as over-bank flooding strongly influence this part of the delta. In contrast, the northwest sector is represented by few major distributaries, and overbank sedimentation is less widespread relative to the southeast sector. Peat is abundant and occurs in herbaceous and forested swamps that are individually up to 200 km2 in area. Northwest-directed littoral currents transport large volumes of suspended sediment and produce prominent mudcapes along the northwest coast. Mapping of surface sediments, vegetation, and major landforms identified four principal geomorphic systems within the western delta plain: (1) distributary channels, (2) interdistributary flood basins, (3) fluvial-marine transitional environments, and (4) marine-influenced coastal environments. Coring and radiocarbon dating of deltaic deposits show that the northern delta shoreline has prograded 20-30 km during the late Holocene sea-level highstand. Progradation has been accomplished by a combination of distributary avulsion and mudcape progradation. This style of deltaic progradation differs markedly from other deltas such as the Mississippi where distributary avulsion leads to coastal land loss, rather than shoreline progradation. The key difference is that the Orinoco Delta coastal zone receives prodigious amounts of sediment from northwest-moving littoral currents that transport

  13. Holocene aridity and storm phases, Gulf and Atlantic coasts, USA

    NASA Astrophysics Data System (ADS)

    Otvos, Ervin G.

    2005-05-01

    A bottomland flora that prevailed between ˜9900 and 6000 cal yr B.P. in a North Carolina stream valley may not reflect a regionally much wetter Atlantic climate, coeval with record drought in the Great Plains region and assumed dry Gulf coastal conditions. Such conditions were inferred for 6000 ± 1000 yr ago when the Bermuda High may have consistently occupied summer positions far to the NE. Arid episodes coeval with the Little River local wet interval are known from eolian sediments and pollen spectra in the Atlantic and the Gulf coastal plain. For multiple reasons, the regional extent, intensity, and duration of coastal aridity and alternating wet phases and the Bermuda High positions are not yet adequately constrained. The climate and edaphic causes for the steadily growing predominance of southern pines over hardwoods, achieved between ˜8900 and 4200 cal yr B.P. at different sites at different times are similarly still unresolved. New data from Shelby Lake, AL, reconfirms that no credible field or other proxy evidence exists for a previously postulated "catastrophic Gulf hurricane phase" in the late Holocene.

  14. Diagenetic dolomite formation in a Holocene evaporitic lake

    SciTech Connect

    Coshell, L.; Scott, J. ); Rosen, M.; Turner, J.V. )

    1991-03-01

    Holocene dolomite forms in the sediment of Lake Hayward, a small, permanent, hypersaline lake in the Clifton-Preston Lakeland System, Western Australia. The Clifton-Preston Lakeland System is similar in climate, geography, and sedimentology to the Coorong Region of South Australia. However, dolomite in Lake Hayward is not a primary precipitate as in the Coorong but is of diagenetic origin. The diagenetic origin can be deduced from the combination of the following criteria: (1) the dolomite occurs only between 60-70 cm from the sediment water interface; (2) dolomite occurs as luminescing cement; and (3) dolomite has pristine well-formed rhomb-shaped crystals. The source of magnesium for dolomitization is probably from the concentration of inflowing groundwater by evaporation and the selective removal of calcium by aragonite/calcite precipitation. Although the mechanisms of dolomite formation in Lake Hayward are slightly different than in the Coorong, the presence of Holocene dolomite in an almost identical setting illustrates the importance of the 'Coorong model' for dolomite formation in modern coastal areas.

  15. 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

  16. 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.

  17. 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

  18. The geological framework of coastal land loss in Louisiana

    SciTech Connect

    Penland, S. ); Roberts, H.H. ); Williams, S.J. )

    1990-09-01

    The Mississippi River delta and chenier plains in Louisiana are experiencing catastrophic coastal land loss rates exceeding 100 km{sup 2}/ yr. Louisiana's coastal zone contains 40% of the US wetlands and 80% of the nation's loss occurs here. The origin and stability of these coastal environments are tied to the sediments discharged by the Mississippi River through the delta cycle process. Sediments accumulate in well-defined delta complexes at approximately 800-1,000 year intervals followed by abandonment and barrier island formation. The delta-cycle process, which builds new deltas and barrier islands, has been stopped by flood control structures. These harness the flow of the Mississippi River within a massive levee system, channeling most of the sediments off of the continental shelf. Deprived of sediments and subsiding rapidly, Louisiana's wetlands are disintegrating and the shoreline is eroding. Subsidence is a key critical process driving the submergence of Louisiana's sediment-starved coastal zone. The thickness of the Holocene sequence controls the subsidence rate. Where the Holocene delta plain sequence is greater than 50 m, the submergence rates are 1- 1.25 cm/yr and the land loss rates are 80 km{sup 2}/yr. In contrast, where the Holocene chenier plain thickness is less than 15 m, the submergence rates are 0.4-0.6 cm/yr, and the land loss rate is 10 km{sup 2}/yr.

  19. Holocene paleoenvironments of Northeast Iowa

    USGS Publications Warehouse

    Baker, R.G.; Bettis, E. Arthur; Schwert, D.R.; Horton, D.G.; Chumbley, C.A.; Gonzalez, Luis A.; Reagan, M.K.

    1996-01-01

    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 bryophyle 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 mesic elements such as Acer saccharum, Tilia americana, Ostrya 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 and 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 ??? 3000 BP (while nonarboreal pollen percentages remained relatively high) indicates that oak savanna prevailed with little change until settlement time. The bryophyte assemblages strongly support the vascular plant record. Rich fen species characteristic of boreal habitats occur only in the late-glacial. They are replaced by a number of deciduous-forest elements when early-to-middle Holocene forests were

  20. Holocene loess and paleosols in central Alaska: A proxy record of Holocene climate change

    SciTech Connect

    Bigelow, N.H.; Beget, J.E.

    1992-03-01

    Episodic Holocene loess deposition and soil formation in the sediments of the Nenana valley of Central Alaska may reflect Holocene climate change. Periods of loess deposition seem to correlate with times of alpine glacier activity, while paleosols correspond to times of glacial retreat These variations may reflect changes in solar activity Stuiver and Braziunas, 1989. Other mechanisms, such as orbitally forced changes in seasonality, volcanism, and atmospheric C02 variability may also have affected Holocene climates and loess deposition.

  1. The Holocene Isolation of Dalma Island

    NASA Astrophysics Data System (ADS)

    Lokier, Stephen

    2010-05-01

    Dalma Island can be broadly defined as an emergent salt diapir formed through the halokinetic emplacement of the Precambrian-Cambrian Hormuz Complex. The outline of the island, as seen today, has been much modified by anthropogenic dredge-and-fill activities. The lithofacies of Dalma Island can be subdivided into three distinct geological and geographical provinces. The core of the island is dominated by the sedimentary, evaporitic and volcanic lithologies of the Hormuz Complex. These chaotically distributed units are unconformably overlain by sediments and evaporites of the Miocene Fars Formation. The island's coastline is dominated by Recent bioclastic sediments, primarily derived from reefs at the island's northern coast. Following exposure of the Arabian Gulf floor during the Last Glacial Maximum, marine waters entered the Strait of Hormuz in the latest Pleistocene and the Gulf once again became a shallow epicontinental seaway. Bathymetric surveys reveal that the sea floor surrounding Dalma Island and separating it from the mainland lies at a depth shallower than 40 m. The Holocene transgression would not have had any effect on this area until after 10.2 Ka. After this time, rising ground water levels, associated with the advancing shoreline, may have resulted in the localised formation of shallow lakes or marshes in depressions. As sea level continued to rise, these lakes coalesced and the Dalma Salt Dome became increasingly isolated from the mainland. Once the transgression had reached the -15 m contour, by 8.5 Ka, Dalma would have been completely isolated from the mainland. By 6 ka sea level had reached present levels with continued rise eventually peaking between 1-2 m higher than today. At this time the area of the island would have been much reduced with wide areas of the island's low-lying coastal plain being either submerged or lying in the intertidal environment. The above figures for the isolation of Dalma make two assumptions. Firstly, it is

  2. Holocene history of ENSO variance and asymmetry in the eastern tropical Pacific.

    PubMed

    Carré, Matthieu; Sachs, Julian P; Purca, Sara; Schauer, Andrew J; Braconnot, Pascale; Falcón, Rommel Angeles; Julien, Michèle; Lavallée, Danièle

    2014-08-29

    Understanding the response of the El Niño-Southern Oscillation (ENSO) to global warming requires quantitative data on ENSO under different climate regimes. Here, we present a reconstruction of ENSO in the eastern tropical Pacific spanning the past 10,000 years derived from oxygen isotopes in fossil mollusk shells from Peru. We found that ENSO variance was close to the modern level in the early Holocene and severely damped ~4000 to 5000 years ago. In addition, ENSO variability was skewed toward cold events along coastal Peru 6700 to 7500 years ago owing to a shift of warm anomalies toward the Central Pacific. The modern ENSO regime was established ~3000 to 4500 years ago. We conclude that ENSO was sensitive to changes in climate boundary conditions during the Holocene, including but not limited to insolation.

  3. Enhanced Late Holocene ENSO/PDO expression along the margins of the eastern North Pacific

    USGS Publications Warehouse

    Barron, John A.; Anderson, Lesleigh

    2011-01-01

    Late Holocene records indicate a more variable, El Niño-like, and more positive PDO Pacific. The Aleutian Low became more intensified during the winter and/or located more to the east. The North Pacific High became weaker and/or displaced more to the south. Coastal upwelling off California intensified during the spring but decreased during the fall. Oregon and California SSTs became warmer, recording the shoreward migration of sub-tropical gyre waters during the fall, while spring upwelling (cooler SST) increased in the Santa Barbara Basin. The high-resolution proxy records indicate enhanced ENSO and PDO variability after ∼4000 cal BP off southern California, ∼3400 cal BP off northern California, and by ∼2000 cal BP in southwestern Yukon. A progressively northward migration of the ENSO teleconnection during the late Holocene is proposed.

  4. Multiple thermal maxima during the Holocene

    SciTech Connect

    Davis, O.K.

    1984-08-10

    The astronomical theory of climatic change provides an alternative to the traditional chronology for Holocene climatic change, which calls for one thermal maximum about 6000 years ago. The theory predicts a series of maxima during the Holocene, one for each season. Because the relation of the perihelion to the spring equinox changes with a 22,000-year period, late summer insolation would have been greatest 5000 years ago, whereas early summer insolation would have been greatest 13,000 years ago. Climatic reconstructions based on the response of ecosystems to late summer climate indicate a later Holocene thermal maximum than paleoclimatic data sensitive to early summer climate. In southern Idaho, three different vegetation types indicate thermal maxima at different times during the Holocene, depending on the climatic variable controlling each type. 28 references, 2 figures.

  5. Faunal histories from Holocene ancient DNA.

    PubMed

    de Bruyn, Mark; Hoelzel, A Rus; Carvalho, Gary R; Hofreiter, Michael

    2011-08-01

    Recent studies using ancient DNA have been instrumental in advancing understanding of the impact of Holocene climate change on biodiversity. Ancient DNA has been used to track demography, migration and diversity, and is providing new insights into the long-term dynamics of species and population distributions. The Holocene is key to understanding how the past has impacted on the present, as it bridges the gap between contemporary phylogeographic studies and those with inference on Pleistocene patterns, based on ancient DNA studies. Here, we examine the major patterns of Holocene faunal population dynamics and connectivity; highlighting the dynamic nature of species and population responses to Holocene climatic change, thereby providing an 'analogue' for understanding potential impacts of future change.

  6. 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.

  7. Methane turnover and environmental change from Holocene biomarker records in a thermokarst lake in Arctic Alaska

    USGS Publications Warehouse

    Elvert, Marcus; Pohlman, John; Becker, Kevin W.; Gaglioti, Benjamin V.; Hinrichs, Kai-Uwe; Wooller, Matthew J.

    2016-01-01

    Arctic lakes and wetlands contribute a substantial amount of methane to the contemporary atmosphere, yet profound knowledge gaps remain regarding the intensity and climatic control of past methane emissions from this source. In this study, we reconstruct methane turnover and environmental conditions, including estimates of mean annual and summer temperature, from a thermokarst lake (Lake Qalluuraq) on the Arctic Coastal Plain of northern Alaska for the Holocene by using source-specific lipid biomarkers preserved in a radiocarbon-dated sediment core. Our results document a more prominent role for methane in the carbon cycle when the lake basin was an emergent fen habitat between ~12,300 and ~10,000 cal yr BP, a time period closely coinciding with the Holocene Thermal Maximum (HTM) in North Alaska. Enhanced methane turnover was stimulated by relatively warm temperatures, increased moisture, nutrient supply, and primary productivity. After ~10,000 cal yr BP, a thermokarst lake with abundant submerged mosses evolved, and through the mid-Holocene temperatures were approximately 3°C cooler. Under these conditions, organic matter decomposition was attenuated, which facilitated the accumulation of submerged mosses within a shallower Lake Qalluuraq. Reduced methane assimilation into biomass during the mid-Holocene suggests that thermokarst lakes are carbon sinks during cold periods. In the late-Holocene from ~2700 cal yr BP to the most recent time, however, temperatures and carbon deposition rose and methane oxidation intensified, indicating that more rapid organic matter decomposition and enhanced methane production could amplify climate feedback via potential methane emissions in the future.

  8. Onshore-offshore coastal lithofacies of Polis basin, NW Cyprus

    SciTech Connect

    Ward, L.C. )

    1988-08-01

    The Polis basin, northwest Cyprus, is located between the Akamas Peninsula and the main Troodos ophiolite massif. The basin contains sediments of Miocene-Holocene age and allows detailed study of a range of onshore-offshore coastal lithofacies which represent potential reservoirs. Coastal sediments of Messinian age characterized by algal mats and fluvial channel fill are found in the basin. Following very late Miocene rifting and Pliocene transgression, steep, narrow, faulted coastlines were produced, and several coastal facies were generated. These include coastal alluvial fans, offshore reefs, and tectonically generated cliff deposits as olistolith blocks. The steep, faulted coastline generated fan-delta deposits in early Pliocene time, superseded during late Pliocene regression by carbonate fan deltas. Offshore coastal lithofacies include storm-generated deposits, consisting of rip-up clasts and hummocky cross-stratification in sand-silt sequences, and mass-flow and channelized conglomerates and debris flows in this tectonically active basin. Shoreline sands are dominated by long-shore drift which generated longitudinal sandbars and offshore gravel bars. Pleistocene-age deposits show several suites of coastal deposits, formed in response to oscillations in Pleistocene sea level. These include beach deposits demonstrating beach-crest and planar bimodal back-beach deposits, together with coastal lagoons transected by cross-bedded fluvial conglomerate deposits. In addition, lowstands produced large channelized braided fluvial deposits which formed part of a broad coastal plain. Certain Pleistocene channels are deformed by continuing synsedimentary tectonic activity.

  9. Relationship between species diversity and reef growth in the Holocene at Ishigaki Island, Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Hongo, Chuki; Kayanne, Hajime

    2010-01-01

    Coral reefs are influenced by global and local factors, and living corals are currently faced with a potential loss of species diversity. Knowledge of the relationship between species diversity and reef growth during the Holocene is important in terms of accurately reconstructing natural conditions prior to recent disturbances (e.g., human impact, pollution, and over-harvesting) and in predicting future scenarios (e.g., abrupt sea-level rise, coastal change, and economic services). This study seeks to characterize the Holocene and present-day reef at Ishigaki Island in the Ryukyu Islands, focusing on spatial and temporal variations in the relationship between species diversity and reef growth. The analysis is based on a drilling core obtained for the Holocene reefs and quantitative species-diversity data (Shannon and Weaver's diversity index, H') obtained for the present-day reef. H' was calculated for four coral communities surveyed at the Ibaruma and Fukido reefs. The Holocene sequence was dominated by the corymbose coral community (e.g., Acropora digitifera, A. hyacinthus, Goniastrea retiformis, and Platygyra ryukyuensis), yielding an H' value of 1.6. The encrusting coral community (e.g., Echinopora lamellose and Pachyseris rugosa) showed the highest diversity at the reef ( H' = 2.2); however, this community was not one of the main reef builders during the Holocene. The massive coral community (e.g., Porites lutea and Favites chinensis) showed the lowest diversity ( H' = 0.6). It also made a minor contribution to reef building; this community appeared in a shallow lagoon once sea level had stabilized. The arborescent coral community (e.g., A. formosa and A. nobilis) was one of the main reef builders, although yielding an H' value of much less than 1.0. Species diversity is not a prerequisite in terms of Holocene reef growth. Thus, a few species (e.g., A. digitifera, A. hyacinthus, A. formosa, A. nobilis, G. retiformis, and P. ryukyuensis) from two main reef

  10. Carbon sequestration in Southeast Asian tropical peatlands over the Holocene period: large-scale hydrological controls

    NASA Astrophysics Data System (ADS)

    Dommain, R.; Couwenberg, J.; Cobb, A.; Gandois, L.; Kai, F.; Su'ut, N.; Abu Salim, K.; Harvey, C. F.; Glaser, P. H.; Joosten, H.

    2012-12-01

    Tropical peatlands are recognized as a significant sink of carbon dioxide and an important source of methane. Low latitude peatlands contain an estimated pool of 90 Pg C, of which ca. 70 Pg C is stored in Southeast Asian peatlands. However, the Holocene development of this carbon reservoir is poorly established. Here we provide a synthesis of carbon uptake rates by tropical peatlands in Southeast Asia across millennial timescales for the past 11,000 years. Our reconstruction of the carbon accumulation history for Borneo, Sumatra and Peninsular Malaysia is based on a synthesis of radiocarbon dated peat profiles, modeling of peatland extent, and a new carbon accumulation record from Brunei (NW-Borneo). During the early Holocene the first peatlands formed in southern Borneo under the influence of a strong monsoon and rapid rise in sea-level. The carbon accumulation rate (CAR) in these peatlands was on average 60 g C m-2 yr-1 at this time. Peatlands started to spread across the coastal lowlands of Borneo, Sumatra and Peninsular Malaysia after 8000 cal BP only when the rate of rising sea-level decreased. The major phase of coastal peatland initiation lasted from 7000 to 4000 cal BP. This period was marked by a Holocene precipitation maximum, suppressed El Niño activity, and the Holocene maximum in sea-level on the Sunda Shelf. The mean CAR of coastal peatlands at this time was 80 g C m-2 yr-1, with a Holocene peak of ~100 g C m-2 yr-1 from 4900 to 4500 cal BP. Significantly, atmospheric CO2 concentrations measured in the Taylor Dome Antarctic ice core indicate a plateau during this period of otherwise rising CO2 concentrations. During the Late Holocene CAR declined both in coastal peatlands (ca. 70 g C m-2 yr-1) and in southern Borneo (ca. 20 g C m-2 yr-1) in response to falling sea-levels and increased El Niño frequency and intensity. In fact, several peatlands in southern Borneo have stopped accumulating peat-carbon under higher El Niño activity. These results

  11. Pleistocene and Holocene Iberian flora: a complete picture and review

    NASA Astrophysics Data System (ADS)

    González Sampériz, Penélope

    2010-05-01

    A detailed analysis of the location and composition of Iberian vegetation types during the whole Pleistocene and Holocene periods shows a complex patched landscape with persistence of different types of ecosystems, even during glacial times. In addition, recent, high-resolution palaeoecological records are changing the traditional picture of post-glacial vegetation succession in the Iberian Peninsula. The main available charcoal and pollen sequences include, coniferous and deciduous forest, steppes, shrublands, savannahs and glacial refugia during the Pleistocene for Meso-thermophytes (phytodiversity reservoirs), in different proportions. This panorama suggests an environmental complexity that relates biotic responses to climate changes forced by Milankovitch cycles, suborbital forcings and by the latitudinal and physiographic particularities of the Iberian Peninsula. Thus, many factors are critical in the course of vegetational developments and strong regional differences are observed since the Early Pleistocene. Currently, the flora of Iberia is located in two biogeographical/climatic regions: the Eurosiberian and the Mediterranean. The first one includes northern and northwestern areas of the peninsula, where post-glacial responses of vegetation are very similar to Central Europe, although with some particularities due to its proximity to both the Atlantic Ocean and the Mediterranean region. The second one comprises the main territory of Iberia and shows more complex patterns and singularities, now and in the past. Steppe landscapes dominated extensive areas over all the territory during the cold spells of the Quaternary, especially during the Late Pleistocene up to the Last Glacial Maximum, but differences in composition of the dominant taxa (Compositae versus Artemisia) are observed since the Early Pleistocene, probably related to moisture regional gradients. Coastal shelves and intramountainous valleys, even in continental areas, are spots of floristic

  12. Coastal Navigation Portfolio Management

    DTIC Science & Technology

    2015-02-19

    CIRP.aspx Coastal Inlets Research Program Coastal Navigation Portfolio Management The Coastal Navigatoin Portfolio Management work unit...across the vast coastal navigation portfolio of projects. The USACE maintains a vast infrastructure portfolio of deep-draft coastal entrance...the Corps needs to be able to direct resources at the navigation projects that are most critical to overall marine transportation system performance

  13. 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.

  14. Holocene thinning of the Greenland ice sheet.

    PubMed

    Vinther, B M; Buchardt, S L; Clausen, H B; Dahl-Jensen, D; Johnsen, S J; Fisher, D A; Koerner, R M; Raynaud, D; Lipenkov, V; Andersen, K K; Blunier, T; Rasmussen, S O; Steffensen, J P; Svensson, A M

    2009-09-17

    On entering an era of global warming, the stability of the Greenland ice sheet (GIS) is an important concern, especially in the light of new evidence of rapidly changing flow and melt conditions at the GIS margins. Studying the response of the GIS to past climatic change may help to advance our understanding of GIS dynamics. The previous interpretation of evidence from stable isotopes (delta(18)O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially and that a consistent Holocene climate optimum-the unusually warm period from about 9,000 to 6,000 years ago found in many northern-latitude palaeoclimate records-did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing delta(18)O from GIS ice cores with delta(18)O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of delta(18)O evidence from ice cores, our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our delta(18)O-based results are corroborated by the air content of ice cores, a proxy for surface elevation. State-of-the-art ice sheet models are generally found to be underestimating the extent and changes in GIS elevation and area; our findings may help to improve the ability of models to reproduce the GIS response to Holocene climate.

  15. Holocene sedimentation processes and environmental changes along the Namibian coastline

    NASA Astrophysics Data System (ADS)

    Schüller, Irka; Belz, Lukas; Wilkes, Heinz; Wehrmann, Achim

    2016-04-01

    The regional oceanic and atmospheric circulation patterns strongly control environmental conditions in southern Africa. Changes in the system may have significant consequences on climate and related processes. The hyper arid coast of Namibia is mainly influenced by (1) the cold Benguela upwelling, (2) the Benguela current and (3) the Angola current. The Benguela current transports the cool, upwelling water from south to north and interacts with the warm, contrary flowing Angola current at the Angola-Benguela Front (ABF). Today the ABF is located around the Namibian-Angolan border with minor seasonal changes. Therefore, climate and environment at the Namibian coast are affected by the cold water conditions. It is known evidently that the location of the ABF changed during the Holocene over several latitudes and enabled warm water species to expand their range farther south. Several (paleo-) lagoons (coastal salt pans) exist along the Namibian coastline. Most of them are already barred and filled by longshore sediment transport processes. Tidal flooding and active sedimentation processes are restricted to the southernmost lagoons. Two different types of sediments occur. The northern pans contain well sorted, siliciclastic medium sands. Fine-layered alternation refers to changes in mineral composition. The southern pans are dominated by typical tidal sediments with a high amount of benthic fauna (mainly bivalves and gastropods). At Cape Cross the distinct shift between both facies is documented in the cores. Age determinations of core material prove a very fast sediment filling of the distinct lagoons with high sedimentation rates. However, the age of closure differs from lagoon to lagoon. Northern pan sediments are much older (Cape Cross: ~ 5000 a BP) than southern (Sandwich Bay and Conception Bay: 1800 - 300 a BP). Additional information are supported by river clay deposits (~ 36600 a BP) and fossil reed systems (~ 47900 a BP) in Conception Bay and peat deposits at

  16. Distribution of albatross remains in the Far East regions during the Holocene, based on zooarchaeological remains.

    PubMed

    Eda, Masaki; Higuchi, Hiroyoshi

    2004-07-01

    Many albatross remains have been found in the Japanese Islands and the surrounding areas, such as Sakhalin and South Korea. These remains are interesting for two reasons: numerous sites from which albatross remains have been found are located in coastal regions of the Far East where no albatrosses have been distributed recently, and there are some sites in which albatross remains represent a large portion of avian remains, although albatrosses are not easily preyed upon by human beings. We collected data on albatross remains from archaeological sites in the Far East regions during the Holocene and arranged the remains geographically, temporally and in terms of quantity. Based on these results, we showed that coastal areas along the Seas of Okhotsk and Japan have rarely been used by albatrosses in Modern times, though formerly there were many albatrosses. We proposed two explanations for the shrinkage of their distributional range: excessive hunting in the breeding areas, and distributional changes of prey for albatrosses.

  17. 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

  18. 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

  19. Holocene depositional history of a large glaciated estuary, Penobscot Bay, Maine

    SciTech Connect

    Knebel, H.J.

    1985-01-01

    Data from seismic-reflection profiles, sidescan-sonar images, and sediment samples reveal the Holocene depositional history of the large (1100 km/sup 2/) Penobscot Bay estuary of coastal Maine. Isostatic recovery of the crust caused the bay to emerge during the immediate postglacial period, and relative sea level stood at about -40 m sometime between 9000 and 11,000 years ago. During the postglacial low stand, the ancestral Penobscot River flowed across the subaerially exposed head of the bay and debouched into Middle Passage. Organic-matter-rich silty clays form the river were deposited in the glacially eroded lower reaches of Middle and West Passages behind a shallow bedrock sill at the mouth of the bay. East Passage was isolated from the rest of the system and received only small amounts of locally derived sediment. During the ensuing Holocene transgression, the locus of sedimentation shifted to the head of the bay. Here, fluvial sediments filled the ancestral channels of the Penobscot River as base level rose, and the migrating surf zone created a gently dipping erosional unconformity, marked by a thin, reworked lag deposit of coarse sand and gravel. As sea level continued to rise, a relatively thick layer (as much as 15 m) of silty clay was deposited at the head of West Passage. During and since the transgression, tidal currents and waves have eroded and reworked Holocene deposits along the shore, within restricted channels, around topographic highs, and over the shallow bay-mouth sill.

  20. Carbonate-evaporite cycles in the Miocene to Holocene of Abu Dhabi, United Arab Emirates

    SciTech Connect

    Whittle, G.L.; Alsharhan, A.S.; Takezaki, H.

    1995-08-01

    The coastal sabkhas of the United Arab Emirates provide a Holocene analog for the study of evaporite formation. Carbonate-evaporite sequences are common throughout geologic history and, in the Arabian Gulf region in particular, create the reservoir-seal relationship of some of the most prolific hydrocarbon reservoirs in the world. Detailed core description, thin section study and geochemical analysis of Miocene to Holocene cores from the sabkha of Abu Dhabi have been performed in order to characterize modern sabkha diagenetic patterns. Two primary lithologies, dolomite and anhydrite were identified and subdivided into lithofacies. Based on these lithofacies, deposition is interpreted to have occurred in shallow open marine, lagoonal, tidal channel, tidal/algal flats and supratidal sabkha settings. The primary diagenetic effects are dolomitization, anhydritc formation and leaching. As anhydrite precipitated (in the form of gypsum), the Mg:Ca ratio increased to the point where rapid dolomitization of original limestone occurred. Leaching was pervasive, as subaerial exposure led to the formation of moldic porosity in dolomitized packstones and grainstones. Dolomitic cements in these pores, and leached zones in some of these crystals suggests that leaching continued after dolomitization. By comparing the Holocene sabkha sediments to ancient ones, insight may be gained into the extent of dolomilization both with depth and distance for in the high water mark, the zonation of the stratigraphy from upper supratidal to shallow shelf, the preservation potential of algal mats after burial, the compaction effects after shallow burial, and other diagenetic alterations.

  1. Salinity and hydrodynamics of the Holocene and upper Pleistocene beneath the Louisiana wetlands from electrical measurements

    SciTech Connect

    McGinnis, L.D.; Thompson, M.D.; Kuecher, G.J.; Wilkey, P.L.; Isaacson, H.R.

    1995-06-01

    A conceptual hydrodynamic model in the Holocene and upper Pleistocene beneath the Louisiana wetlands is described in terms of safety distributions. Porewater safety is calculated from electrical measurements, including resistivity soundings, electric logs, and electromagnetic profiling. Electrical measurements support the primary, basin-wide groundwater flow model; however, the data also indicate secondary contributions from expulsion of fluids under geopressure along active growth faults and from original waters of deposition. Expulsion of water from growth faults has been described previously for deeper sections of the Pleistocene, but has not been reported for the Holocene or upper Pleistocene beneath the Louisiana wetlands. Porewater chemistry variations beneath the coastal wetlands are a consequence of the following (in order of importance): (1) environment of deposition; (2) a basin-wide, regional flow system; (3) expulsion from deep-seated growth faults; and (4) pore water extrusion due to compaction. Water chemistry in Holocene clays and muds is influenced primarily by the deposition environment In Pleistocene sands, the chemistry is a function of the other three factors.

  2. Holocene relative sea level rise and subsidence in northern Gulf of Mexico

    SciTech Connect

    Penland, S.; Sutter, J.R.; Ramsey, K.E.; McBride, R.D.

    1988-01-01

    The analysis of more than 90 tidal gauge records, 10,000-km high resolution seismic profiles, 500 vibracores, and 250 radiocarbon dates led to the development of a new sea level history for the Louisiana coastal zone and adjacent continental shelf for the last 8,000 years. Now reinterpreted, the original single delta plain is seen as actually two individual, imbricated shelf-phase delta plains deposited at different sea levels. Termed the modern and late Holocene, these two delta plains are separated by a regional shoreface refinement surface, which can be traced updip to the relict-transgressive Teche shoreline. The Late Holocene delta plain was deposited during a sea level stillstand 6 m below the present, 3,000-7,2000 years ago. A 5 to 6-m eustatic-enhanced relative rise in sea level, 2,5000-3,000 years ago at a rate of 1-1.2 cm/yr led to the complete transgresive submergence of the lower late Holocene delta plain. Sea level reached its approximate position about 2,500 years ago, and since then the Mississippi River has built the modern delta plain consisting of the abandoned St. Bernard and Lafourche delta complexes and the active Balize and Atchafalaya delta complexes.

  3. Sedimentary evolution of the Holocene subaqueous clinoform off the southern Shandong Peninsula in the Western South Yellow Sea

    NASA Astrophysics Data System (ADS)

    Qiu, Jiandong; Liu, Jian; Saito, Yoshiki; Yang, Zigeng; Yue, Baojing; Wang, Hong; Kong, Xianghuai

    2014-10-01

    Based on the stratigraphic sequence formed since the last glaciation and revealed by 3000 km long high-resolution shallow seismic profiles and the core QDZ03 acquired recently off the southern Shandong Peninsula, we addressed the sedimentary characteristics of a Holocene subaqueous clinoform in this paper. Integrated analyses were made on the core QDZ03, including sedimentary facies, sediment grain sizes, clay minerals, geochemistry, micro paleontology, and AMS 14C dating. The result indicates that there exists a Holocene subaqueous clinoform, whose bottom boundary generally lies at 15-40 m below the present sea level with its depth contours roughly parallel to the coast and getting deeper seawards. The maximum thickness of the clinoform is up to 22.5 m on the coast side, and the thickness contours generally spread in a banded way along the coastline and becomes thinner towards the sea. At the mouths of some bays along the coast, the clinoform stretches in the shape of a fan and its thickness is evidently larger than that of the surrounding sediments. This clinoform came into being in the early Holocene (about 11.2 cal kyr BP) and can be divided into the lower and upper depositional units (DU 2 and DU 1, respectively). The unit DU 2, being usually less than 3 m in thickness and formed under a low sedimentation rate, is located between the bottom boundary and the Holocene maximum flooding surface (MFS), and represents the sediment of a post-glacial transgressive systems tract; whereas the unit DU 1, the main body of the clinoform, sits on the MFS, belonging to the sediment of a high-stand systems tract from middle Holocene (about 7-6 cal kyr BP) to the present. The provenance of the clinoform differs from that of the typical sediments of the Yellow River and can be considered as the results of the joint contribution from both the Yellow River and the proximal coastal sediments of the Shandong Peninsula, as evidenced by the sediment geochemistry of the core. As is

  4. Overview of Recent Coastal Tectonic Deformation in the Mexican Subduction Zone

    NASA Astrophysics Data System (ADS)

    Ramírez-Herrera, M. Teresa; Kostoglodov, Vladimir; Urrutia-Fucugauchi, Jaime

    2011-08-01

    Holocene and Pleistocene tectonic deformation of the coast in the Mexico subudction margin is recorded by geomorphic and stratigraphic markers. We document the spatial and temporal variability of active deformation on the coastal Mexican subduction margin. Pleistocene uplift rates are estimated using wave-cut platforms at ca. 0.7-0.9 m/ka on the Jalisco block coast, Rivera-North America tectonic plate boundary. We examine reported measurements from marine notches and shoreline angle elevations in conjunction with their radiocarbon ages that indicate surface uplift rates increasing during the Holocene up to ca. 3 ± 0.5 m/ka. In contrast, steady rates of uplift (ca. 0.5-1.0 m/ka) in the Pleistocene and Holocene characterize the Michoacan coastal sector, south of El Gordo graben and north of the Orozco Fracture Zone (OFZ), incorporated within the Cocos-North America plate boundary. Significantly higher rates of surface uplift (ca. 7 m/ka) across the OFZ subduction may reflect the roughness of subducting plate. Absence of preserved marine terraces on the coastal sector across El Gordo graben likely reflects slow uplift or coastal subsidence. Stratigraphic markers and their radiocarbon ages show late Holocene (ca. last 6 ka bp) coastal subsidence on the Guerrero gap sector in agreement with a landscape barren of marine terraces and with archeological evidence of coastal subsidence. Temporal and spatial variability in recent deformation rates on the Mexican Pacific coast may be due to differences in tectonic regimes and to localized processes related to subduction, such as crustal faults, subduction erosion and underplating of subducted materials under the southern Mexico continental margin.

  5. Holocene evolution and sedimentation rate of Alikes Lagoon, Zakynthos island, Western Greece - preliminary results

    NASA Astrophysics Data System (ADS)

    Avramidis, P.; Kontopoulos, N.

    2009-03-01

    In the present study we present preliminary results of Zakynthos Alikes lagoon, which is one of the most seismically active regions of Greece. In order to estimate - interpret the Holocene evolution of the area and to reconstruct the palaeonvironmental changes, we based on the data of a 21 m sediment core. Sediment types, structure, colour, as well as contact depths and bed characteristics, were recorded in the field. Standarised sedimentological analysis were carried out, on 46 samples including grain size analysis, calculation of moment measures, and micro- and molluscan fossils of 17 selected samples. Moreover, radiocarbon age determinations have been made on individual Cardium shells from two horizons and whole - core Magnetic Susceptibility (MS) measurements were taken. The interpretation of depositional environments suggests a coastal environment (restricted-shallow) with reduced salinity such as a lagoon margin and in a tidal flat and/or marsh particularly. The maximum age of the study sediments is about 8500 BP. The rate of sedimentation between 8280 BP and 5590 BP was 5.3 mm/yr and between 5590 BP and modern times 1.03 mm/yr. The rate of sedimentation was higher until mid-Holocene while decrease after to 1.03 mm/yr, results which are similar to other coastal areas of western Greece.

  6. Middle Holocene aridity, eolian-dune accretion, and the formation of Lake Mattamuskeet, eastern North Carolina

    NASA Astrophysics Data System (ADS)

    Rodriguez, A. B.; Waters, M. N.; Piehler, M. F.

    2009-12-01

    The stratigraphic record of Lake Mattamuskeet, eastern North Carolina, shows an interval of eolian activity in the middle Holocene. There are about 500,000 elliptical lakes, wetlands, and depressions with elevated rims located on the Atlantic Coastal Plain named Carolina Bays. Lake Mattamuskeet is the largest (162 km2; mean depth 1.0 m), and formed when a blowout depression of a parabolic dune flooded 1540-1635 cal yr. BP. The parabolic dune is up to 2.0-m thick, contains sedimentary structures that indicate rapid deposition, and is composed of a coarsening-upward sequence of silt at the base to sandy silt at the top. Below the dune is an 8420-8605 cal yr. BP paleosol, which corresponds to a wet period in the area. The bottom half of the dune deposit contains abundant charcoal beds and laminae dated at ~6600 cal yr. BP, indicating fire was associated with initial formation of the parabolic dune. Middle Holocene climate of the southeast Atlantic coastal plain is not well constrained. Deposition of the eolian dune could be a local response to fire; or indicate a time of reduced effective moisture in the area. Given that pedogenesis on the dune did not initiate until ~2780-2965 cal yr. BP and flooding of the Lake basin did not occur for ~1000 years after that, effective moisture may have been low for approximately 3600 years after initial dune accretion.

  7. Ages, distributions, and origins of upland coastal dune sheets in Oregon, USA

    USGS Publications Warehouse

    Peterson, C.D.; Stock, E.; Price, D.M.; Hart, R.; Reckendorf, F.; Erlandson, J.M.; Hostetler, S.W.

    2007-01-01

    A total of ten upland dune sheets, totaling 245??km in combined length, have been investigated for their origin(s) along the Oregon coast (500??km in length). The ages of dune emplacement range from 0.1 to 103??ka based on radiocarbon (36 samples) and luminescence (46 samples) dating techniques. The majority of the emplacement dates fall into two periods of late-Pleistocene age (11-103??ka) and mid-late-Holocene age (0.1-8??ka) that correspond to marine low-stand and marine high-stand conditions, respectively. The distribution of both the late-Pleistocene dune sheets (516??km2 total surface area) and the late-Holocene dune sheets (184??km2) are concentrated (90% of total surface area) along a 100??km coastal reach of the south-central Oregon coast. This coastal reach lies directly landward of a major bight (Heceta-Perpetua-Stonewall Banks) on the continental shelf, at depths of 30-200??m below present mean sea level (MSL). The banks served to trap northward littoral drift during most of the late-Pleistocene conditions of lowered sea level (- 50 ?? 20??m MSL). The emerged inner-shelf permitted cross-shelf, eolian sand transport (10-50??km distance) by onshore winds. The depocenter sand deposits were reworked by the Holocene marine transgression and carried landward by asymmetric wave transport during early- to mid-Holocene time. The earliest dated onset of Holocene dune accretion occurred at 8??ka in the central Oregon coast. A northward migration of Northeast Pacific storm tracks to the latitude of the shelf depocenter (Stonewall, Perpetua, Heceta Banks) in Holocene time resulted in eastward wave transport from the offshore depocenter. The complex interplay of coastal morphology, paleosea-level, and paleoclimate yielded the observed peak distribution of beach and dune sand observed along the south-central Oregon coast. ?? 2007 Elsevier B.V. All rights reserved.

  8. Evaluating mid-Holocene precipitation over Australasia and the Maritime Continent in climate models

    NASA Astrophysics Data System (ADS)

    Ackerley, Duncan; Reeves, Jessica

    2015-04-01

    The Australasian INTIMATE (INTegration of Ice-core, Marine and Terrestrial records) initiative (INQUA project #0809) was undertaken to develop a consistent chronological assessment of the climate of the past 30000 years over Australia, New Zealand and the Maritime Continent. Work has continued as part of SHAPE initiative (INQUA project #1302), but there has currently been little use of this comprehensive resource for evaluating the available climate model data. Therefore, this work presents the initial assessment of model simulations of the mid-Holocene over the Australasian and Maritime Continents (taken from the Paleoclimate Modelling Intercomparison Project, PMIP) in relation to those available data. The mid-Holocene (6 ka) encompasses a period after sea level stabilisation (around 8-7.5 ka) and before the onset of strong ENSO-related variability (post 4 ka). There is some evidence of possibly drier conditions over northern Australia with increased coastal dune activity, along with slightly wetter conditions over Borneo and Papua New Guinea. Weakening of the Southern Hemisphere mid-latitude westerlies (relative to the early Holocene) is also likely to have occurred, as evidenced by drier conditions in Western Tasmania and Victoria. The modelled results from the mid-Holocene simulations indicate that conditions were approximately 1-6% drier over much of continental Australia than at present. There is also evidence of slightly wetter conditions (1-3%) over the northern tip of Australia and parts of Papua New Guinea and Borneo. The Southern Hemisphere westerlies in the mid-latitudes (around 50S) are also weaker by 1-2 m s-1 in the model simulations. There are also differences in the seasonal cycle of precipitation and circulation in these models in response to the changes in the orbital parameters in the mid-Holocene relative to present day. The precipitation in the early half of the monsoon season (October, November and December-OND) is typically 10% higher in the

  9. Postglacial development of the eastern Gulf of Finland: from Pleistocene glacial lake basins to Holocene lagoon systems

    NASA Astrophysics Data System (ADS)

    Ryabchuk, Daria; Sergeev, Alexander; Kotilainen, Aarno; Hyttinen, Outi; Grigoriev, Andrey; Gerasimov, Dmitry; Anisimov, Mikhail; Gusentsova, Tatiana; Zhamoida, Vladimir; Amantov, Aleksey; Budanov, Leonid

    2016-04-01

    Despite significant amount of data, there are still lots of debatable questions and unsolved problems concerning postglacial geological history of the Eastern Gulf of Finland, the Baltic Sea. Among these problems are: 1) locations of the end moraine and glacio-fluvial deposits; 2) time and genesis of the large accretion forms (spits, bars, dunes); 3) basinwide correlations of trangression/regression culminations with the other parts of the Baltic Sea basin; 4) study of salinity, timing, frequency and intensity of Holocene saline water inflows and their links of sedimentation processes associated with climate change. Aiming to receive new data about regional postglacial development, the GIS analyses of bottom relief and available geological and geophysical data was undertaken, the maps of preQuaternary relief, moraine and Late Pleistocene surfaces, glacial moraine and Holocene sediments thicknesses were compiled. High-resolution sediment proxy study of several cores, taken from eastern Gulf of Finland bottom, allows to study grain-size distribution and geochemical features of glacial lake and Holocene sediments, to reveal sedimentation rates and paleoenvironment features of postglacial basins. Interdisciplinary geoarcheological approaches offer new opportunities for studying the region's geological history and paleogeography. Based on proxy marine geological and coastal geoarcheological studies (e.g. off-shore acoustic survey, side-scan profiling and sediment sampling, on-shore ground-penetrating radar (GPR SIR 2000), leveling, drilling, grain-size analyses and radiocarbon dating and archeological research) detailed paleogeographical reconstruction for three micro-regions - Sestroretsky and Lahta Lowlands, Narva-Luga Klint Bay and Southern Ladoga - were compiled. As a result, new high resolution models of Holocene geological development of the Eastern Gulf of Finland were received. Model calibration and verification used results from proxy geoarcheological research

  10. Geomorphological & Geoarchaeological Indicators of the Holocene Sea-Level Changes on Ras El Hekma Area, NW Coast of Egypt

    NASA Astrophysics Data System (ADS)

    Torab, Magdy

    2016-02-01

    Ras El Hekma area is a part of the NW coast of Egypt. It is located on the Egyptian Mediterranean Coast, approximately 220 km West of Alexandria City. It is shaped as a triangle with its headland extending into the Mediterranean sea for about 15 km, and is occupied by sedimentary rocks belonging to the Tertiary and Quaternary Eras. Its western coastline consists of Pleistocene Oolitic limestone ridges with separated steep scarps, while the eastern coastline consists of sandy beaches, coastal spits, coastal bars, tombolos and bays. The objective of this paper is to define some geomorphological and geoarchaelological indicators of The Holocene sea-level changes in the study area, especially the geomorphic landforms such as: marine notches, cliffs, sea caves and benches. This is to add to some archaeological remains that have been discovered by the paper's author under the current sea level. These remains include: submerged ruins of Greek and Roman harbors, wells and fish tanks near the coastline (Leuke Akte, Hermaea, Phoinikous and Zygris), in addition to an ancient Roman harbor used during the World War II in Tell El Zaytun area (Site #6). Evaluations of the discovered archaeological remains help our understanding of the evolution of the sea level during the Holocene. This study is based on observation of the relative sea-level curves drawn of the Holocene, detailed geomorphological and Geoarchaelogical surveying, sampling, dating and mapping as well as satellite image interpretation and GIS techniques.

  11. Holocene Tree Line and Climate Change on the Queen Charlotte Islands, Canada

    NASA Astrophysics Data System (ADS)

    Pellatt, Marlow G.; Mathewes, Rolf W.

    1997-07-01

    Palynological study of two subalpine ponds on the Queen Charlotte Islands reveals changes in tree line and climate during the Holocene. The findings agree with previous reconstructions, from nearby Louise Pond on the Queen Charlotte Islands, that suggest a warmer-than-present climate and higher-than-present tree lines in the early Holocene (ca. 9600-6600 14C yr B.P.). Basal ages at SC1 Pond and Shangri-La Bog indicate that the basins did not hold permanent water before 7200 14C yr B.P., consistent with a warmer and drier early Holocene previously inferred from Louise Pond. Pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 ± 90 14C yr B.P., similar to the 5790 ± 130 14C yr B.P. age for cooling inferred from Louise Pond. Conditions similar to present were established at SC1 Pond by 3460 ± 100 14C yr B.P., confirming the previous estimate of 3400 14C yr B.P. at Louise Pond. This 3400 14C yr B.P. vegetation shift on the Queen Charlotte Islands corresponds with the beginning of the Tiedemann glacial advance in the south-coastal mountains of British Columbia (ca. 3300 14C yr B.P.), the Peyto and Robson glacial advances between 3300 and 2800 14C yr B.P. in the Rocky Mountains, and climatic cooling inferred from palynological studies throughout southern British Columbia, northern Washington, and southeast Alaska. These findings confirm that changes in regional climate influenced changes in vegetation in coastal British Columbia.

  12. Holocene fire activity and vegetation response in South-Eastern Iberia

    NASA Astrophysics Data System (ADS)

    Gil-Romera, Graciela; Carrión, José S.; Pausas, Juli G.; Sevilla-Callejo, Miguel; Lamb, Henry F.; Fernández, Santiago; Burjachs, Francesc

    2010-05-01

    Since fire has been recognized as an essential disturbance in Mediterranean landscapes, the study of long-term fire ecology has developed rapidly. We have reconstructed a sequence of vegetation dynamics and fire changes across south-eastern Iberia by coupling records of climate, fire, vegetation and human activities. We calculated fire activity anomalies (FAAs) in relation to 3 ka cal BP for 10-8 ka cal BP, 6 ka cal BP, 4 ka cal BP and the present. For most of the Early to the Mid-Holocene uneven, but low fire events were the main vegetation driver at high altitudes where broadleaved and coniferous trees presented a highly dynamic post-fire response. At mid-altitudes in the mainland Segura Mountains, fire activity remained relatively stable, at similar levels to recent times. We hypothesize that coastal areas, both mountains and lowlands, were more fire-prone landscapes as biomass was more likely to have accumulated than in the inland regions, triggering regular fire events. The wet and warm phase towards the Mid-Holocene (between ca 8 and 6 ka cal BP) affected the whole region and promoted the spread of mesophytic forest co-existing with Pinus, as FAAs appear strongly negative at 6 ka cal BP, with a less important role of fire. Mid and Late Holocene landscapes were shaped by an increasing aridity trend and the rise of human occupation, especially in the coastal mountains where forest disappeared from ca 2 ka cal BP. Mediterranean-type vegetation (evergreen oaks and Pinus pinaster- halepensis types) showed the fastest post-fire vegetation dynamics over time.

  13. On Early Holocene Ice-Sheet/Sea-Level Interactions

    NASA Astrophysics Data System (ADS)

    Tornqvist, T. E.; Hijma, M.

    2011-12-01

    conundrum. Given the potentially large freshwater fluxes involved, this issue clearly needs to be resolved. Future progress as envisioned above will require more sophisticated sea-level studies worldwide, with decimeter-scale vertical resolution and sub-centennial scale temporal resolution. A particular challenge for the early Holocene is the diminishing role of coral records - compared to earlier stages of deglaciation - due to a lack of vertical resolution. On the other hand, the sparseness of coastal peat records before 6 to 8 ka presents another obstacle. A combination of increased prospecting offshore and targeting new types of sea-level indicators therefore deserves to be encouraged. Finally, all new field studies should be conducted in tandem with efforts to further refine glacial isostatic adjustment (GIA) models. Within this context, we foresee a primary focus on (1) optimizing site selection for the collection of new RSL records by means of GIA model predictions; (2) converting local observations of RSL rise into eustatic signals, including volumes and sources of meltwater discharge; and (3) capitalizing on gravitational fingerprint theory as outlined above.

  14. Hydrogeologic framework of the Virginia coastal plain

    USGS Publications Warehouse

    Meng, Andrew A.; Harsh, John F.

    1988-01-01

    This report defines the hydrogeologic framework of the Virginia Coastal Plain and is a product of a comprehensive regional study to define the geology, hydrology, and geochemistry of the northern Atlantic Coastal Plain aquifer system extending from North Carolina to Long Island, New York. The Virginia Coastal Plain consists of an eastward-thickening wedge of generally unconsolidated, interbedded sands and clays, ranging in age from Early Cretaceous to Holocene. These sediments range in thickness from more than 6,000 feet beneath the northeastern part of the Eastern Shore Peninsula to nearly 0 feet along the Fall Line. Eight confined aquifers, eight confining units, and an uppermost water table aquifer are delineated as the hydrogeologic framework of the Coastal Plain sediments in Virginia. The nine regional aquifers, from oldest to youngest, are lower, middle, and upper Potomac, Brightseat, Aquia, Chickahominy-Piney Point, St. Marys-Choptank, Yorktown-Eastover, and Columbia. The Brightseat is a newly identified and correlated aquifer of early Paleoceneage. This study is one of other, similar studies of the Coastal Plain areas in North Carolina, Maryland-Delaware, New Jersey, and Long Island, New York. These combined studies provide a system of hydrogeologic units that can be identified and correlated throughout the northern Atlantic Coastal Plain. Data for this study were collected and analyzed from October 1979 to May 1983. The nine aquifers and eight confining units are identified and delineated by use of geophysical logs, drillers' information, and stratigraphic and paleontologic data. By correlating geophysical logs with hydrologic, stratigraphic, and paleontologic data throughout the Coastal Plain, a comprehensive multilayered framework of aquifers and confining units, each with distinct lithologic properties, was developed. Cross sections show the stratigraphic relationships of aquifers and confining units in the hydrogeologic framework of the Virginia

  15. Lineaments in coastal plain sediments as seen in ERTS imagery

    NASA Technical Reports Server (NTRS)

    Withington, C. F.

    1973-01-01

    Examination of satellite imagery over the Atlantic Coastal Plain near Washington, D. C. shows numerous lineaments, which cannot be accounted for by any known cultural or natural features. At least some of these lineaments represent the surface expression of faults, for one of them has been correlated with the outcrop of a fault that had been traced for several miles in southern Prince Georges County, Maryland. If a substantial number of these lineaments do indeed represent fault traces, the fact that they show on the surface suggests that the geologic history of the Coastal Plain is much more complex than has previously been recognized, and that faulting may have occurred in the Holocene, much later than has generally been recognized. The importance that such recent movements could have on future development of the Coastal Plain should be emphasized.

  16. Climatic fluctuations during the Holocene based on eastern Mediterranean continental shelf sediment cores

    NASA Astrophysics Data System (ADS)

    Mor-Federman, Tsofit; Bookman, Revital; Almogi-Labin, Ahuva; Herut, Barak

    2013-04-01

    .7074 in the southern core compared to ~0.7080 in the northern core, reflect a strong finger print of the Blue Nile on the sediments adjacent to the Nile cone that rapidly disappear northwards. The changes in the geochemical and sedimentary proxies are connected to Holocene climatic fluctuations. Change of provenances and decrease of fluvial input to the basin and in water column productivity around 5,500 years BP occur simultaneously with changes in the intensity of the monsoonal system over the headwaters of the Nile. These changes, that are present both at southern and central inner shelf, can be connected to the end of the African humid period. In the late Holocene, as the influence of the Nile on the central part of the shelf decreases, the Mediterranean climate system that originates in the northern hemisphere climate system is more evident. Cycles of ~1,500 years of coarse sediments probably originating from erosion in the coastal environment correlate with cold events known as the north Atlantic Bond cycles. Our results show the potential of shelf sediments to record and understand the control of climatic global systems on inner shelf sediment records.

  17. Natural variability in ocean carbon chemistry on the California margin during the Holocene

    NASA Astrophysics Data System (ADS)

    Chrystal, A. E.; Paytan, A.

    2011-12-01

    Limited information is available to understand the potential magnitude and consequences of ocean acidification in temperate coastal environments. Some regions, such as the California margin, are influenced both by terrestrial runoff and by a strong upwelling system, which brings nutrient-rich, but corrosive, low-pH and low [CO_{3}^{2-}] water to the surface. Coastal upwelling areas may therefore be particularly sensitive to additional carbon input due to anthropogenic carbon emissions. Regions with strong coastal upwelling are among the most biologically productive marine sites in the world and are fundamental to the integrity of oceanic food webs and economic fisheries. Thus, it is important that we understand how anthropogenic acidification will affect these coastal ecosystems. A critical step in understanding the influence of reduced pH and [CO_{3}^{2-}] on coastal environments is to quantify the natural variability in ocean pH over long timescales (thousands of years) and to constrain the components that impact carbon chemistry in coastal systems; these include terrestrial freshwater input, upwelling, circulation changes, productivity, and anthropogenic CO_{2} flux. We propose to create a baseline against which to compare anthropogenic change via an integrative study of these variables over the past 10,000 years (Holocene). As a preliminary step, we will measure Mg/Ca, B/Ca and U/Ca in benthic foraminifera from the Santa Monica Basin (ODP 1015) and compare these with existing radio-carbon measurements and high-resolution δ^{18}O and δ^{13}C records from the same site to evaluate pH changes in the context of variability in salinity, upwelling and circulation changes.

  18. Fossil mollusc-faunas: Their bearing on the Holocene evolution of the Lower Central Plain of Bangkok (Thailand)

    NASA Astrophysics Data System (ADS)

    Negri, Mauro Pietro

    2009-08-01

    In this work, fossil molluscan assemblages are analyzed in order to reconstruct the evolution of the Northern Gulf of Thailand during the Holocene. The marine sediments (Bangkok Clay Formation) of the Lower Central Plain of Bangkok and the coastal plain of Phetchaburi were sampled at 16 localities, obtaining fossil shells and mangrove peat whose 14C ages range from 9000 to 2000 CYBP. A statistical treatment of abundance data returned four major groups, namely the Dendostrea rosacea association (intertidal mud), the Corbula fortisulcata- Mactra luzonica association (shallow infralittoral sandy mud), the Nuculana mauritiana- Timoclea scabra association (infralittoral sand spit) and the Timoclea scabra- Arcopagia pudica association (infralittoral mud). The data allowed both a stratigraphic correlation along two transects covering all of the Holocene basin and the creation of digitalized maps showing the presumable extension of the Thai paleogulf around the apex of Flandrian transgression event (about 5500 CYBP).

  19. Stratigraphic evidence for anthropogenically induced coastal environmental change from Oaxaca, Mexico

    NASA Astrophysics Data System (ADS)

    Goman, Michelle; Joyce, Arthur; Mueller, Raymond

    2005-05-01

    Previous interdisciplinary paleoenvironmental and archaeological research along the Río Verde Valley of Oaxaca, Mexico, showed that Holocene erosion in the highland valleys of the upper drainage basin triggered geomorphic changes in the river's coastal floodplain. This article uses stratigraphic data from sediment cores extracted from Laguna Pastoría, an estuary in the lower Río Verde Valley, to examine changes in coastal geomorphology potentially triggered by highland erosion. Coastal lagoon sediments contain a stratigraphically and chronologically distinct record of major hurricane strikes during late Holocene times. Three distinct storm facies are identified from sediment cores obtained from Laguna Pastoría, which indicate that profound coastal environmental changes occurred within the region and are correlated with increased sediment supplied from highland erosion. The Chione/ Laevicardium facies was deposited in an open bay while the Mytella/barnacle facies and sand facies were deposited in an enclosed lagoon following bay barrier formation. We argue that highland erosion triggered major geomorphic changes in the lowlands including bay barrier formation by ˜2500 cal yr B.P. These environmental changes may have had significant effects on human populations in the region. The lagoon stratigraphy further indicates an increase in mid-late Holocene hurricane activity, possibly caused by increased El Niño frequencies.

  20. 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.

  1. Introduction to Holocene environmental change in Kamchatka

    NASA Astrophysics Data System (ADS)

    Brooks, S. J.; Diekmann, B.; Jones, V. J.; Hammarlund, D.

    2015-11-01

    This volume brings together a collection of papers on Holocene environmental change in the Kamchatka Peninsula, in the Russian Far East. Much of the work that appears in these papers was completed under the auspices of two major research activities: a UK NERC-funded project Influence of global teleconnections on Holocene climate in Kamchatka, which dealt with the analysis of lake records collected during the Swedish Beringia 2005 expedition organised by the Swedish Polar Research Secretariat; and a Russian-German multidisciplinary research project KALMAR - Kurile-Kamchatka and Aleutian Marginal Sea-Island Arc Systems: Geodynamic and Climate Interaction in Space and Time, funded by the German Federal Ministry of Education and Research (BMBF).

  2. Holocene deceleration of the Greenland Ice Sheet.

    PubMed

    MacGregor, Joseph A; Colgan, William T; Fahnestock, Mark A; Morlighem, Mathieu; Catania, Ginny A; Paden, John D; Gogineni, S Prasad

    2016-02-05

    Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet's radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet's dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry.

  3. Holocene deceleration of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    MacGregor, Joseph A.; Colgan, William T.; Fahnestock, Mark A.; Morlighem, Mathieu; Catania, Ginny A.; Paden, John D.; Gogineni, S. Prasad

    2016-02-01

    Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet’s radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet’s dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry.

  4. Holocene fault scarps near Tacoma, Washington, USA

    USGS Publications Warehouse

    Sherrod, B.L.; Brocher, T.M.; Weaver, C.S.; Bucknam, R.C.; Blakely, R.J.; Kelsey, H.M.; Nelson, A.R.; Haugerud, R.

    2004-01-01

    Airborne laser mapping confirms that Holocene active faults traverse the Puget Sound metropolitan area, northwestern continental United States. The mapping, which detects forest-floor relief of as little as 15 cm, reveals scarps along geophysical lineaments that separate areas of Holocene uplift and subsidence. Along one such line of scarps, we found that a fault warped the ground surface between A.D. 770 and 1160. This reverse fault, which projects through Tacoma, Washington, bounds the southern and western sides of the Seattle uplift. The northern flank of the Seattle uplift is bounded by a reverse fault beneath Seattle that broke in A.D. 900-930. Observations of tectonic scarps along the Tacoma fault demonstrate that active faulting with associated surface rupture and ground motions pose a significant hazard in the Puget Sound region.

  5. The Role of Middle and Late Holocene North Pacific Sea Surface Temperatures on Precipitation Patterns in the Western United States

    NASA Astrophysics Data System (ADS)

    Barron, J. A.; Anderson, L.; Starratt, S.; Wahl, D.; Anderson, L.; Addison, J. A.

    2015-12-01

    Comparative analyses of marine and terrestrial proxy records reveal regional changes in precipitation seasonality and relationships with sea surface temperatures (SSTs) as indicators of ocean-atmosphere dynamics. Enhanced La Niña-like conditions and cooler SSTs characterized the middle Holocene (~8.O to 4.0 ka) waters off northern California and in the eastern equatorial Pacific. Terrestrial records suggest that winters in the western US were generally dry, although wetter intervals attributed to winter precipitation beginning at ~5.5 ka are documented in coastal Oregon and Washington and in the northern Great Basin. Proxy studies suggest that the North American Monsoon (NAM) intensified beginning at ~7.5 ka, coinciding with warming Gulf of California SSTs coupled with a more northerly position of the Intertropical Convergence Zone (ITCZ). If monsoonal precipitation spread northward into the eastern Great Basin and the western Rockies of Colorado, it is possible that wetter intervals of the middle Holocene in Nevada, Utah, and western Colorado may reflect increases in both summer and winter precipitation. El Niño event frequency and intensity began increasing between 4.0 and 3.0 ka, when modern ocean-atmosphere dynamics appear to have been established along the California coastal margin. Effects included cool, wet winters, enhanced spring coastal upwelling that extended into the summer, and higher September-October SSTs corresponding with the end of the coastal upwelling season. Winters became wetter in both the coastal and interior regions of the western US, while spring and summers generally became drier. The intensity of NAM precipitation also declined due to a more southerly mean position of the ITCZ. By ~3.0 cal ka the modern climatology of the margins of eastern North Pacific was established, resulting in intensification of the northwest-southwest precipitation dipole and the development of distinct Pacific Decadal Oscillation cycles.

  6. 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

    , et al., 2013). Reconstruction of the Early Holocene average July air temperatures based on chironomid analysis showed that in the middle of the Peninsula air T July were around + 10.3oC which is below the modern values. A sharp warming took place then during the Mid Holocene optimum (Ilyashuk, 2000; Ilyashuk, 2013). The reconstructed Early Holocene T July of the southern part of the Peninsula are similar to the modern T July + 12oC. For a detailed reconstruction of paleogeographic environments of the south-western part of the Kola Peninsula in Holocene we studied the valley of Kolvica river and the southern shore of lake Kolvitsa (67.01-67.11 N; 33.17-33.48 E). Analysis of lithological sequences and radiocarbon dating of sediments of small lakes present a clear outline of the development of the studied region from 9.3 14C ka (10.5 cal. ka BP) to the present day. Based on micro-paleontological analyzes we performed a qualitative reconstruction of climatic conditions during the Holocene, which shows a clear change of cooling and warming in the studied area, as well as the dynamics of the White Sea coastal zone and the development of the studied lake basins. This project was financed by RFBR 15-35-50479 mol_nr.

  7. Influence of Holocene stratigraphic architecture on ground surface settlements: A case study from the City of Pisa (Tuscany, Italy)

    NASA Astrophysics Data System (ADS)

    Sarti, Giovanni; Rossi, Veronica; Amorosi, Alessandro

    2012-12-01

    The Holocene stratigraphic architecture of modern coastal and deltaic plains has peculiar characteristics that may influence ground surface settlements. In the Pisa urban area, the inhomogeneous spatial distribution of geotechnically weak layers, typically formed during the mid-late Holocene (highstand) coastal progradation, is inferred to be responsible for urban ground settlement and building damage, as evidenced by the tilt of several surface structures, among which the famous Leaning Tower of Pisa is the most prominent. On the basis of integrated stratigraphic, sedimentological and geotechnical data from a wide georeferenced database, three facies associations with high deformability potential (Units 1-3) are identified in the uppermost 30 m as opposed to depositional facies (Units 4-5) with higher geotechnical strength. Whereas Unit 1 represents a thick, laterally extensive lagoonal clay deposit, the overlying highly deformable units (Units 2-3) show more discontinuous spatial distribution controlled by the Holocene paleohydrographic evolution of the Arno coastal plain. Unit 2, dated between the Neolithic and the Etruscan age (ca. 5000-2000 yr BP), is composed of swamp clays and silty clays recording lagoon infilling due to Arno Delta progradation. Units 3 and 4, which consist of wet levee deposits and stiff floodplain clays, respectively, formed during the subsequent phases of alluvial plain construction started around the Roman age (from ca. 2000 yr BP). Whereas Units 3 and 4 are recorded within the uppermost 5 m, fluvial and distributary channel sands (Unit 5) cut the underlying deltaic-alluvial succession at various stratigraphic levels, down to Unit 1. The spatial distribution of these units gives rise to three, locally juxtaposed, stratigraphic motifs in Pisa underground, reflecting different potential risks for settlement under building loads. We show how lateral changes in stratigraphic architecture account for the irregular spatial distribution of

  8. 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

  9. 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.

  10. High-resolution climatic evolution of coastal northern California during the past 16,000 years

    USGS Publications Warehouse

    Barron, J.A.; Heusser, L.; Herbert, T.; Lyle, M.

    2003-01-01

    Holocene and latest Pleistocene oceanographic conditions and the coastal climate of northern California have varied greatly, based upon high-resolution studies (ca. every 100 years) of diatoms, alkenones, pollen, CaCO3%, and total organic carbon at Ocean Drilling Program (ODP) Site 1019 (41.682??N, 124.930??W, 980 m water depth . Marine climate proxies (alkenone sea surface temperatures [SSTs] and CaCO3%) behaved remarkably like the Greenland Ice Sheet Project (GISP)-2 oxygen isotope record during the B??lling-Allerod, Younger Dryas (YD), and early part of the Holocene. During the YD, alkenone SSTs decreased by >3??C below mean B??lling-Allerod and Holocene SSTs. The early Holocene (ca. 11.6 to 8.2 ka) was a time of generally warm conditions and moderate CaCO3 content (generally >4%). The middle part of the Holocene (ca. 8.2 to 3.2 ka) was marked by alkenone SSTs that were consistently 1-2??C cooler than either the earlier or later parts of the Holocene, by greatly reduced numbers of the gyre-diatom Pseudoeunotia doliolus (<10%), and by a permanent drop in CaCO3% to <3%. Starting at ca. 5.2 ka, coastal redwood and alder began a steady rise, arguing for increasing effective moisture and the development of the north coast temperate rain forest. At ca. 3.2 ka, a permanent ca. 1??C increase in alkenone SST and a threefold increase in P. doliolus signaled a warming of fall and winter SSTs. Intensified (higher amplitude and more frequent) cycles of pine pollen alternating with increased alder and redwood pollen are evidence that rapid changes in effective moisture and seasonal temperature (enhanced El Nin??o-Southern Oscillation [ENSO] cycles) have characterized the Site 1019 record since about 3.5 ka.

  11. Changing sedimentation in tidal flat sediments of the southern North Sea from the Holocene to the present: a geochemical approach

    NASA Astrophysics Data System (ADS)

    Dellwig, O.; Hinrichs, J.; Hild, A.; Brumsack, H.-J.

    2000-12-01

    This study presents geochemical evidence for a change in depositional energy conditions of tidal flat sediments (southern North Sea) from the Holocene, i.e. human unaffected, to present-day conditions. We investigated Holocene and present tidal flat sediments and suspended particulate matter (SPM) from the NW German coastal area (Spiekeroog Island back-barrier area and Jade Bay), as well as sediments from the Helgoland Island mud hole area. Samples were analysed for bulk parameters (TC, TIC), major (Al, Ca, Fe, Mg, K, P, Si, Ti), and trace elements (Ba, Pb, Rb, Sr, V, Zn, Zr). Enrichment factors versus average shale reveal four groups of elements for the investigated Holocene and present sediments. Fe, Mg, K, Ba, Rb, and V show a shale-like behaviour and enrichments of Ca and Sr reflect the occurrence of carbonate, whereas higher levels of P, Pb, and Zn in the present samples are due to pollution. The fourth group consists of Si, Ti, and Zr, which may be used as indicators of depositional energy because these elements are concentrated by particle sorting effects. The most pronounced geochemical difference between the Holocene and present tidal flat sediments is an enrichment of Zr in the present samples. As Zr is commonly associated with heavy minerals, this enrichment indicates a higher depositional energy environment in the present sediments, which can be traced to modern dike building. The same effect, i.e. increasing current velocities, is responsible for a general depletion of fine-grained, Al-rich, material in the present sediments. The examination of SPM shows that large amounts of this fine-grained material are present in the water column and may be transported from the intertidal system into the open North Sea. The comparison of a calculated Holocene clay accumulation rate with modern estimates of SPM deposition in the German Bight reveals about a two-fold higher deposition of fine material in the Holocene tidal flats. As the sediments from the Helgoland

  12. Particle size characterisation of Holocene back-barrier sequences from North Atlantic coasts (SW Spain and SE England)

    NASA Astrophysics Data System (ADS)

    Lario, J.; Spencer, C.; Plater, A. J.; Zazo, C.; Goy, J. L.; Dabrio, C. J.

    2002-01-01

    In this paper, we present the results of bivariate plots of grain size parameters (mean against sorting) in the reconstruction of Holocene environmental change in coastal environments where barrier formation has had an important control on sedimentation. Sites on the North Atlantic coast with differing histories of climate, sediment flux, sea-level change and barrier integrity are investigated to determine the general efficacy of this bivariate parameter model in distinguishing between open- and closed-basin conditions, and in reviewing the significance of aperiodic high-energy geomorphic events in controlling late stage back-barrier sedimentation.

  13. East meets West: Differing views of the Aleutian Low's role in affecting Holocene productivity in the Subarctic North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Addison, J. A.; Finney, B. P.; Harada, N.

    2012-12-01

    Modern instrumental and monitoring observations indicate strong multi-decadal changes and spatial heterogeneities affect climate and marine ecosystems in the North Pacific Ocean. Networks of high-resolution paleoclimate archives from this dynamic region are therefore required to describe changes prior to historical records. We present new decadally-resolved marine sediment core data from the Kuril Islands in the Sea of Okhotsk, together with sub-decadal data from the temperate fjords of the Gulf of Alaska (GoAK). These distant sites are located along the western (Kuril) and eastern (GoAK) boundaries of the Subarctic North Pacific Ocean, where micronutrient-rich coastal waters interact with North Pacific high-nutrient-low-chlorophyll (HNLC) waters to drive highly productive marine ecosystems. In the Sea of Okhotsk, a notable increase in opal concentrations (a proxy for past siliceous primary productivity) occurs during the middle Holocene between ~5000 and 6000 yrs ago, while alkenone-based warm season SST proxies either decline or remain relatively constant. A similar middle Holocene increase in opal concentrations is also observed in the GoAK during an interval of declining warm season coastal SAT as inferred from pollen transfer functions [Heusser et al., 1985]. Declining summer solar insolation during the middle Holocene can explain the overall decline in warm-season SST in both the Sea of Okhotsk and the Gulf of Alaska. However, as the increase in opal likely reflects an improvement in North Pacific phytoplankton growing conditions during the spring/summer bloom season, then the opal increase seems unlikely to be related directly to summer solar insolation. We propose a middle Holocene intensification of the Aleutian Low (AL) pressure cell and concomitant changes in North Pacific circulation may be responsible. In both regions, several potential mechanisms related to an intensified AL could result in greater productivity including: (i) increased advection

  14. Holocene Tsunami deposits associated with earthquakes along Pacific coast, northeast Japan

    NASA Astrophysics Data System (ADS)

    Suzuki, H.; Imaizumi, T.; Ishiyama, T.; Miyauchi, T.; Kagohara, K.; Haraguchi, T.; Marushima, N.; Omachi, T.

    2009-12-01

    We investigated Holocene tsumami deposits along the Pacific coast of northeast Japan in order to define the ages and source areas of earthquakes generating large tsunamis. Sediment cores were collected by using geoslicers and hand augers at alluvial lowlands interpreted by aerial photographs, and ages of deposits were dated by radiocarbon methods and tephrochronology. Pacific coast of northeast Japan faces the Japan trench where Pacific plate subducts beneath the Eurasian plate, so that the coast has repeatedly experienced some large tsunamis following historical interplate earthquakes (the 1896 Meiji Sanriku Tsunami, the 1793 Kansei Tsunami, the 1611 Keicho Sanriku Tsunami and the 869 Jogan Tsunami). While the southern part along the Pacific coast (from the Sendai Plain to the Joban coastal region) has nearly straight shorelines and well developed coastal lowlands, the northern part (the Sanriku coastal region) has typical ria shorelines and poorly developed coastal lowlands. Multiple sand layers are identified between muddy or peaty sediments in drilled core samples to a depth of 1-5.5 m at several coastal areas, which is located at backlands of beach ridges and natural levees. In the southern part along the Pacific coast, sand layers corresponding to the 869 Jogan Tsunami are identified, and the older sand layers suggest that tsunamis which are as large as the 869 tsunami have occurred at few hundred years intervals over the past 5000 years. On the other hand, in the northern part along the Pacific coast, multiple sand layers which indicate the arrival of large tsunamis are also found at the similar intervals to the southern coast during 6000-2000 years ago, but most of the depositional ages of the sand layers do not coincide with those of the southern coast. We suggest that earthquakes generating large tsunamis along northern and southern Pacific coast of northeast Japan have both occurred at few hundred years intervals during the late Holocene, but in most

  15. The Anthropocene - and International Law of the Holocene

    NASA Astrophysics Data System (ADS)

    Vidas, D.

    2012-12-01

    may become necessary. First, with few exceptions, today's Law of the Sea regulates human impacts on the ocean and submarine components of the Earth System in terms of the political boundaries of sovereignty and jurisdiction, translated into law: basically, this is what is expressed through the various maritime zones and the division of jurisdictional competences among coastal and flag states. However, prospects of rising sea-levels and the consequences for the current law-of-the-sea architecture will eventually necessitate deep-going changes in that legal framework. Second, also the ultimate objectives of the current international regulations will need to be re-formulated, and crafted so as to enable us to better channel and confine human impacts on the Earth System. Moreover, some fundamentals of International Law - not least the concept of 'territory' and state control over territory as a constituent element of statehood in international law - may, as we leave the Holocene and enter the Anthropocene, require profound re-examination. REFERENCES: Vidas, D., 2011. The Anthropocene and the International Law of the Sea, Philosophical Transactions of the Royal Society - A, Vol. 369, pp. 909-925. Zalasiewicz, J., M. Williams, W. Steffen and P.J. Crutzen, 2010. The New World of the Anthropocene, Environmental Science & Technology, Vol. 44, pp. 2228-2231.

  16. Coastal Inlets Research Program

    DTIC Science & Technology

    2015-02-09

    FEB 2015 2. REPORT TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE Coastal Inlets Research Program 5a. CONTRACT NUMBER...S) AND ADDRESS(ES) U.S. Army Engineer Research and Development Center,CIRP - The Coastal Inlets Research Program,3909 Halls Ferry Road,Vicksburg,MS...CIRP.aspx Coastal Inlets Research Program The Coastal Inlets Research Program (CIRP) is a R&D Program funded through the Operations & Maintenance

  17. 'Cape capture': Geologic data and modeling results suggest the holocene loss of a Carolina Cape

    USGS Publications Warehouse

    Thieler, E.R.; Ashton, A.D.

    2011-01-01

    For more than a century, the origin and evolution of the set of cuspate forelands known as the Carolina Capes-Hatteras, Lookout, Fear, and Romain-off the eastern coast of the United States have been discussed and debated. The consensus conceptual model is not only that these capes existed through much or all of the Holocene transgression, but also that their number has not changed. Here we describe bathymetric, lithologic, seismic, and chronologic data that suggest another cape may have existed between Capes Hatteras and Lookout during the early to middle Holocene. This cape likely formed at the distal end of the Neuse-Tar-Pamlico fiuvial system during the early Holocene transgression, when this portion of the shelf was fiooded ca. 9 cal (calibrated) kyr B.P., and was probably abandoned by ca. 4 cal kyr B.P., when the shoreline attained its present general configuration. Previously proposed mechanisms for cape formation suggest that the large-scale, rhythmic pattern of the Carolina Capes arose from a hydrodynamic template or the preexisting geologic framework. Numerical modeling, however, suggests that the number and spacing of capes can be dynamic, and that a coast can self-organize in response to a high-angle-wave instability in shoreline shape. In shoreline evolution model simulations, smaller cuspate forelands are subsumed by larger neighbors over millennial time scales through a process of 'cape capture.' The suggested former cape in Raleigh Bay represents the first interpreted geological evidence of dynamic abandonment suggested by the self-organization hypothesis. Cape capture may be a widespread process in coastal environments with large-scale rhythmic shoreline features; its preservation in the sedimentary record will vary according to geologic setting, physical processes, and sea-level history. ?? 2011 Geological Society of America.

  18. Fire regimes and vegetation change in tropical northern Australia during the late-Holocene

    NASA Astrophysics Data System (ADS)

    Mackenzie, Lydia; Moss, Patrick; Ulm, Sean; Sloss, Craig; Heijnis, Henk; Jacobsen, Geraldine

    2016-04-01

    This study explores the impact of human occupation and abandonment on fire regimes and vegetation communities in the South Wellesley Islands, Gulf of Carpentaria, tropical northern Australia, using charcoal and pollen analysis from four sediment records. Pollen analysis from wetland sediments reveal vegetation succession from mangrove communities to hypersaline mudflats and open woodlands occurred during the late-Holocene. Aquatic species replaced salt tolerant species as the prograding shoreline and dune development formed the Marralda wetlands by 800 cal a BP on the south east coast of Bentinck Island. Wetlands developed on the north and west coast by 500 and 450 cal a BP, respectively. The timing of wetland initiation indicates localised late-Holocene sea level regression, stabilisation and coastal plain development in the Gulf of Carpentaria. Wetland initiation encouraged permanent human occupation of the South Wellesley archipelago, with ongoing archaeological research finding permanent occupation in the last 1500 years, followed by a significant increase in sites from 700 years ago, which peaks over the last 300 years. Macro-charcoal (>125μm) accumulation rates provide a record of fire intensity and frequency across the Island. Both local and regional fire events increase in the last 700 years as traditional owners occupied the Island, with local fires occurring every 104 and 74 years on average (N= 4 and 5 respectively). In the 1950's traditional Indigenous Kaiadilt fire management practices ceased, with the frequency and peak magnitude of fire events significantly increasing and vegetation communities becoming more open. The South Wellesley Islands were unoccupied until the 1980's and were not influenced by European occupation. This study of an Island ecosystem during the late-Holocene provides insight into the effect of human presence and fire regimes on vegetation composition and distribution in a fire resilient environment.

  19. Source, transport, and evolution of saline groundwater in a shallow Holocene aquifer on the tidal deltaplain of southwest Bangladesh

    NASA Astrophysics Data System (ADS)

    Worland, Scott C.; Hornberger, George M.; Goodbred, Steven L.

    2015-07-01

    Deltaic groundwater resources are often vulnerable to degradation from seawater intrusion or through interaction with saline paleowaters. The Ganges-Brahmaputra-Meghna River delta, in Bangladesh and West Bengal, India, is a particularly vulnerable area with an estimated 20 million coastal inhabitants directly affected by saline drinking water. The shallow groundwater of the coastal regions is primarily brackish with pockets of fresher water. A small-scale hydrologic investigation of groundwater salinity beneath an embanked tidal channel island was undertaken to explore possible hydrogeological explanations of the distribution of water salinities in the shallow aquifer. This study employs a combination of 3H and 14C dating, electromagnetic subsurface mapping, and a 2-D solute transport model. The authors conclude that the shallow groundwater salinity can best be explained by the slow infiltration of meteoric water into paleo-brackish estuarine water that was deposited during the early-mid Holocene.

  20. Solar pacing of storm surges, coastal flooding and agricultural losses in the Central Mediterranean.

    PubMed

    Kaniewski, David; Marriner, Nick; Morhange, Christophe; Faivre, Sanja; Otto, Thierry; Van Campo, Elise

    2016-04-29

    Storm surges, leading to catastrophic coastal flooding, are amongst the most feared natural hazards due to the high population densities and economic importance of littoral areas. Using the Central Mediterranean Sea as a model system, we provide strong evidence for enhanced periods of storminess leading to coastal flooding during the last 4500 years. We show that long-term correlations can be drawn between storminess and solar activity, acting on cycles of around 2200-yr and 230-yr. We also find that phases of increased storms and coastal flooding have impacted upon mid- to late Holocene agricultural activity on the Adriatic coast. Based on the general trend observed during the second half of the 20(th) century, climate models are predicting a weakening of Mediterranean storminess. By contrast, our new data suggest that a decrease in solar activity will increase and intensify the risk of frequent flooding in coastal areas.

  1. Solar pacing of storm surges, coastal flooding and agricultural losses in the Central Mediterranean

    PubMed Central

    Kaniewski, David; Marriner, Nick; Morhange, Christophe; Faivre, Sanja; Otto, Thierry; Van Campo, Elise

    2016-01-01

    Storm surges, leading to catastrophic coastal flooding, are amongst the most feared natural hazards due to the high population densities and economic importance of littoral areas. Using the Central Mediterranean Sea as a model system, we provide strong evidence for enhanced periods of storminess leading to coastal flooding during the last 4500 years. We show that long-term correlations can be drawn between storminess and solar activity, acting on cycles of around 2200-yr and 230-yr. We also find that phases of increased storms and coastal flooding have impacted upon mid- to late Holocene agricultural activity on the Adriatic coast. Based on the general trend observed during the second half of the 20th century, climate models are predicting a weakening of Mediterranean storminess. By contrast, our new data suggest that a decrease in solar activity will increase and intensify the risk of frequent flooding in coastal areas. PMID:27126207

  2. Solar pacing of storm surges, coastal flooding and agricultural losses in the Central Mediterranean

    NASA Astrophysics Data System (ADS)

    Kaniewski, David; Marriner, Nick; Morhange, Christophe; Faivre, Sanja; Otto, Thierry; van Campo, Elise

    2016-04-01

    Storm surges, leading to catastrophic coastal flooding, are amongst the most feared natural hazards due to the high population densities and economic importance of littoral areas. Using the Central Mediterranean Sea as a model system, we provide strong evidence for enhanced periods of storminess leading to coastal flooding during the last 4500 years. We show that long-term correlations can be drawn between storminess and solar activity, acting on cycles of around 2200-yr and 230-yr. We also find that phases of increased storms and coastal flooding have impacted upon mid- to late Holocene agricultural activity on the Adriatic coast. Based on the general trend observed during the second half of the 20th century, climate models are predicting a weakening of Mediterranean storminess. By contrast, our new data suggest that a decrease in solar activity will increase and intensify the risk of frequent flooding in coastal areas.

  3. Vegetation Response and Landscape Dynamics of Indian Summer Monsoon Variations during Holocene: An Eco-Geomorphological Appraisal of Tropical Evergreen Forest Subfossil Logs

    PubMed Central

    Kumaran, Navnith K. P.; Padmalal, Damodaran; Nair, Madhavan K.; Limaye, Ruta B.; Guleria, Jaswant S.; Srivastava, Rashmi; Shukla, Anumeha

    2014-01-01

    The high rainfall and low sea level during Early Holocene had a significant impact on the development and sustenance of dense forest and swamp-marsh cover along the southwest coast of India. This heavy rainfall flooded the coastal plains, forest flourishing in the abandoned river channels and other low-lying areas in midland.The coastline and other areas in lowland of southwestern India supply sufficient evidence of tree trunks of wet evergreen forests getting buried during the Holocene period under varying thickness of clay, silty-clay and even in sand sequences. This preserved subfossil log assemblage forms an excellent proxy for eco-geomorphological and palaeoclimate appraisal reported hitherto from Indian subcontinent, and complements the available palynological data. The bulk of the subfossil logs and partially carbonized wood remains have yielded age prior to the Holocene transgression of 6.5 k yrs BP, suggesting therein that flooding due to heavy rainfall drowned the forest cover, even extending to parts of the present shelf. These preserved logs represent a unique palaeoenvironmental database as they contain observable cellular structure. Some of them can even be compared to modern analogues. As these woods belong to the Late Pleistocene and Holocene, they form a valuable source of climate data that alleviates the lack of contemporaneous meteorological records. These palaeoforests along with pollen proxies depict the warmer environment in this region, which is consistent with a Mid Holocene Thermal Maximum often referred to as Holocene Climate Optimum. Thus, the subfossil logs of tropical evergreen forests constitute new indices of Asian palaeomonsoon, while their occurrence and preservation are attributed to eco-geomorphology and hydrological regimes associated with the intensified Asian Summer Monsoon, as recorded elsewhere. PMID:24727672

  4. Vegetation response and landscape dynamics of Indian Summer Monsoon variations during Holocene: an eco-geomorphological appraisal of tropical evergreen forest subfossil logs.

    PubMed

    Kumaran, Navnith K P; Padmalal, Damodaran; Nair, Madhavan K; Limaye, Ruta B; Guleria, Jaswant S; Srivastava, Rashmi; Shukla, Anumeha

    2014-01-01

    The high rainfall and low sea level during Early Holocene had a significant impact on the development and sustenance of dense forest and swamp-marsh cover along the southwest coast of India. This heavy rainfall flooded the coastal plains, forest flourishing in the abandoned river channels and other low-lying areas in midland.The coastline and other areas in lowland of southwestern India supply sufficient evidence of tree trunks of wet evergreen forests getting buried during the Holocene period under varying thickness of clay, silty-clay and even in sand sequences. This preserved subfossil log assemblage forms an excellent proxy for eco-geomorphological and palaeoclimate appraisal reported hitherto from Indian subcontinent, and complements the available palynological data. The bulk of the subfossil logs and partially carbonized wood remains have yielded age prior to the Holocene transgression of 6.5 k yrs BP, suggesting therein that flooding due to heavy rainfall drowned the forest cover, even extending to parts of the present shelf. These preserved logs represent a unique palaeoenvironmental database as they contain observable cellular structure. Some of them can even be compared to modern analogues. As these woods belong to the Late Pleistocene and Holocene, they form a valuable source of climate data that alleviates the lack of contemporaneous meteorological records. These palaeoforests along with pollen proxies depict the warmer environment in this region, which is consistent with a Mid Holocene Thermal Maximum often referred to as Holocene Climate Optimum. Thus, the subfossil logs of tropical evergreen forests constitute new indices of Asian palaeomonsoon, while their occurrence and preservation are attributed to eco-geomorphology and hydrological regimes associated with the intensified Asian Summer Monsoon, as recorded elsewhere.

  5. Chronology of Holocene Cheniers and Oyster Reefs on the Coast of Bohai Bay, China

    NASA Astrophysics Data System (ADS)

    Wang, Hong; Van Strydonck, Mark

    1997-03-01

    Cheniers and oyster reefs are two essential components of Holocene strata on the coast of Bohai Bay, China. The existing nonconventional 14C dates, often with unsuitable sample positions, less-tested samples, and unreasonable data comparisons, limit the refined analysis of the local chronostratigraphy. On the basis of a number of pretreatment routines, including geological investigations, X-ray diffraction analysis (XRD), δ 13C measurement of shells, selection of appropriate shell species ( Umboniumsp. and Terebridae) for 14C dating, and determination of the local mean δ 13C value (-2.68‰ PDB) for the common shells, a set of samples was radiocarbon-dated by Accelerator Mass Spectrometry (AMS). These new ages, obtained from the lower part of cheniers, enable us to estimate the initiation of the cheniers, and confirm that the existing nonconventional dates are often questionable due to unsuitable sample positions. Another two AMS ages, dated for two different microgrowth layers, precipitated in a varying water body, of the same Crassostrea gigasshell are statistically identical within 2σ error. This implies that the different water masses in the coastal environment would be rapidly in balance with the contemporaneous atmospheric CO 2. Both MARINE93 and INTERCAL93 were used for calibration of radiocarbon dates. These amended the time frame of the local Holocene history.

  6. The Posidonia oceanica marine sedimentary record: A Holocene archive of heavy metal pollution.

    PubMed

    Serrano, O; Mateo, M A; Dueñas-Bohórquez, A; Renom, P; López-Sáez, J A; Martínez Cortizas, A

    2011-10-15

    The study of a Posidonia oceanica mat (a peat-like marine sediment) core has provided a record of changes in heavy metal abundances (Fe, Mn, Ni, Cr, Cu, Pb, Cd, Zn, As and Al) since the Mid-Holocene (last 4470yr) in Portlligat Bay (NW Mediterranean). Metal contents were determined in P. oceanica. Both, the concentration records and the results of principal components analysis showed that metal pollution in the studied bay started ca. 2800yr BP and steadily increased until present. The increase in Fe, Cu, Pb, Cd, Zn and As concentrations since ca. 2800yr BP and in particular during Greek (ca. 2680-2465cal BP) and Roman (ca. 2150-1740cal BP) times shows an early anthropogenic pollution rise in the bay, which might be associated with large- and short-scale cultural and technological development. In the last ca. 1000yr the concentrations of heavy metals, mainly derived from anthropogenic activities, have significantly increased (e.g. from ~15 to 47μg g(-1) for Pb, ~23 to 95μg g(-1) for Zn and ~8 to 228μg g(-1) for As). Our study demonstrates for the first time the uniqueness of P. oceanica meadows as long-term archives of abundances, patterns, and trends of heavy metals during the Late Holocene in Mediterranean coastal ecosystems.

  7. Holocene deposits of reservoir-quality sand along the Central South Carolina coastline

    SciTech Connect

    Sexton, W.J.; Hayes, M.O.

    1996-06-01

    The Holocene coastal sand deposits of the central South Carolina coastline were investigated to estimate volumes of reservoir-quality (RQ) sediments. These sand bodies, which vary considerably in size, thickness, shape, and continuity, were deposited in a variety of depositional settings including barrier islands, ebb-tidal deltas, exposed sand flats, tidal sand ridges, and tidal point bars. To identify the RQ sediment for each sand-body type, a conservative mud cutoff value of 15% was chosen. Average thickness values ranged from 6 m for barrier island deposits to 15 m for ebb-tidal deltas. Of the six most significant RQ sand depositional environments on the central portion of the South Carolina coast, ebb-tidal delta complexes accounted for 77% of all RQ sediments. This dominance of the ebb-tidal delta deposits is attributed to the relatively large tidal range in the area (up to 3 m) and to the presence of a number of large, incised alluvial valleys, which are host to estuarine complexes with large tidal prisms. If the Holocene sand deposits along the central 115 km of the South Carolina coast were preserved in the rock record, a total of 1.3 X 10{sup 6} ac-ft of RQ sands would be present, a significant amount considering the short time interval of approximately 5000 yr.

  8. Pleistocene To Holocene Human, Climatic and Environmental Changes In Central and Eastern Java (indonesia)

    NASA Astrophysics Data System (ADS)

    Sémah, A.-M.; Sémah, F.; Simanjuntak, H. T.

    The period between 21,000 and 6000 BP, which includes the Pleistocene-Holocene boundary, is likely to have known drastic environmental changes in the Indones ian archipelago, as seen from various sedimentary, pollen analytic, and archaeological records. In a low altitude swampy basin of central Java which yielded a thick clay and peat stratigraphy, several steps can be pointed between the driest period noticed prior 15,000 BP up to a climatic optimum c. 8,000 BP: a significant increase in humidity from c. 15,000 BP onwards, an extension of the forest after 10,500 BP, completion of almost everwet conditions c. 8,500 BP before a forest regression at c.6000 BP. Correlative excavations of the cave fillings near the coast of the Indian ocean, in the Southern Mountains of Java island, reflect conspicuous changes in the archaeological record: a more or less occasional human occupation of the caves during the late Plaistocene is followed by an intensive one in the early Holocene. Human groups, who brought new technologies (like sophisticated bone tools) had to adapt to and get their subsistence in an extending rain forest like environment, with a faunal turnover (Macaca and Presbytis dominance) or in the numerous flooded basins which formed during that period (fresh water molluscs gathering and smaller tortoise hunting). They carried out close contacts with the coastal area and used also the caves as burial places.

  9. Late Holocene vegetation changes in relation with climate fluctuations and human activity in Languedoc (southern France)

    NASA Astrophysics Data System (ADS)

    Azuara, J.; Combourieu-Nebout, N.; Lebreton, V.; Mazier, F.; Müller, S. D.; Dezileau, L.

    2015-12-01

    Holocene climate fluctuations and human activity since the Neolithic have shaped present-day Mediterranean environments. Separating anthropogenic effects from climatic impacts to better understand Mediterranean paleoenvironmental changes over the last millennia remains a challenging issue. High-resolution pollen analyses were undertaken on two cores from the Palavasian lagoon system (Hérault, southern France). These records allow reconstruction of vegetation dynamics over the last 4500 years. Results are compared with climatic, historical and archeological archives. A long-term aridification trend is highlighted during the late Holocene, and three superimposed arid events are recorded at 4600-4300, 2800-2400 and 1300-1100 cal BP. These periods of high-frequency climate variability coincide in time with the rapid climatic events observed in the Atlantic Ocean (Bond et al., 2001). From the Bronze Age (4000 cal BP) to the end of the Iron Age (around 2000 cal BP), the spread of sclerophyllous taxa and loss of forest cover result from anthropogenic impact. Classical Antiquity is characterized by a major reforestation event related to the concentration of rural activity and populations in coastal plains leading to forest recovery in the mountains. A major regional deforestation occurred at the beginning of the High Middle Ages. Around 1000 cal BP, forest cover is minimal while the cover of olive, chestnut and walnut expands in relation to increasing human influence. The present-day vegetation dominated by Mediterranean shrubland and pines has been in existence since the beginning of the 20th century.

  10. Late Holocene vegetation changes in relation with climate fluctuations and human activities in Languedoc (Southern France)

    NASA Astrophysics Data System (ADS)

    Azuara, J.; Combourieu-Nebout, N.; Lebreton, V.; Mazier, F.; Müller, S. D.; Dezileau, L.

    2015-09-01

    Holocene climate fluctuations and human activities since the Neolithic have shaped present-day Mediterranean environments. Separating anthropogenic effects from climatic impacts to reconstruct Mediterranean paleoenvironments over the last millennia remains a challenging issue. High resolution pollen analyses were undertaken on two cores from the Palavasian lagoon system (Hérault, southern France). These records allow reconstruction of vegetation dynamics over the last 4500 years. Results are compared with climatic, historical and archeological archives. A long-term aridification trend is highlighted during the Late Holocene and three superimposed arid events are recorded at 4600-4300, 2800-2400 and 1300-1100 cal BP. These periods of climatic instability coincide in time with the rapid climatic events depicted in the Atlantic Ocean (Bond et al., 2001). From the Bronze Age (4000 cal BP) to the end of the Iron Age (around 2000 cal BP), the spread of evergreen taxa and loss of forest cover result from anthropogenic impact. The Antiquity is characterized by a major reforestation event related to the concentration of rural activities and populations in coastal plains leading to forest recovery in the mountains. A major regional deforestation occurred at the beginning of the High Middle Ages. Around 1000 cal BP, forest cover is minimal while cover of olive, chestnut and walnut expands in relation to increasing human influence. The present day vegetation dominated by Mediterranean shrubland and pines has been in existence since the beginning of the 20th century.

  11. A mid-Holocene candidate tsunami deposit from the NW Cape (Western Australia)

    NASA Astrophysics Data System (ADS)

    May, Simon Matthias; Falvard, Simon; Norpoth, Maike; Pint, Anna; Brill, Dominik; Engel, Max; Scheffers, Anja; Dierick, Manuel; Paris, Raphaël; Squire, Peter; Brückner, Helmut

    2016-03-01

    Although extreme-wave events are frequent along the northwestern coast of Western Australia and tsunamis in 1994 and 2006 induced considerable coastal flooding locally, robust stratigraphical evidence of prehistoric tropical cyclones and tsunamis from this area is lacking. Based on the analyses of X-ray computed microtomography (μCT) of oriented sediment cores, multi-proxy sediment and microfaunal analyses, optically stimulated luminescence (OSL) and 14C-AMS dating, this study presents detailed investigations on an allochthonous sand layer of marine origin found in a back-barrier depression on the NW Cape Range peninsula. The event layer consists of material from the adjacent beach and dune, fines and thins inland, and was traced up to ~ 400 m onshore. Although a cyclone-induced origin cannot entirely be ruled out, the particular architecture and fabric of the sediment, rip-up clasts and three subunits point to deposition by a tsunami. As such, it represents the first stratigraphical evidence of a prehistoric, mid-Holocene tsunami in NW Western Australia. It was OSL-dated to 5400-4300 years ago, thus postdating the regional mid-Holocene sea-level highstand.

  12. The linkage between marine sediment records and changes in Holocene Saharan landscape: simulating the dust cycle

    NASA Astrophysics Data System (ADS)

    Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

    2016-04-01

    Marine sediment records reveal an abrupt and strong increase in dust deposition in the North Atlantic at the end of the African Humid Period about 4.9 ka to 5.5 ka ago (deMenocal et al., 2000; McGee et al., 2013). The change in dust flux has been attributed to varying Saharan land surface cover. Alternatively, the enhanced dust accumulation is linked to enhanced surface winds and a consequent intensification of coastal upwelling. We present simulation results from a recent sensitivity study, where we demonstrate for the first time the direct link between dust accumulation in marine cores and changes in Saharan land surface during the Holocene. We have simulated timeslices of he mid-Holocene (6 ka BP) and pre-industrial (1850 AD) dust cycle as a function of Saharan land surface cover and atmosphere-ocean conditions using the coupled atmosphere-aerosol model ECHAM6.1-HAM2.1. We prescribe mid-Holocene vegetation cover based on a vegetation reconstruction from pollen data (Hoelzmann et al., 1998) and mid-Holocene lake surface area is determined using a water routing and storage model (Tegen et al., 2002). In agreement with data from marine sediment cores, our simulations show that mid-Holocene dust deposition fluxes in the North Atlantic were two to three times lower compared with pre-industrial fluxes. We identify Saharan land surface characteristics to be the main control on dust transport from North Africa to the North Atlantic. We conclude that the variation in dust accumulation in marine cores is likely related to a transition of the Saharan landscape during the Holocene and not due to changes in atmospheric or ocean conditions alone. Reference: deMenocal, P., Ortiz, J., Guilderson, T., Adkins, J., Sarnthein, M., Baker, L., and Yarusinsky, M.: Abrupt onset and termination of the African Humid Period:: rapid climate responses to gradual insolation forcing, Quaternary Science Reviews, 19, 347-361, 2000. Hoelzmann, P., Jolly, D., Harrison, S. P., Laarif, F

  13. Holocene tsunamis from Mount Etna and the fate of Israeli Neolithic communities

    NASA Astrophysics Data System (ADS)

    Pareschi, Maria Teresa; Boschi, Enzo; Favalli, Massimiliano

    2007-08-01

    Field evidence reveals that the Neolithic village of Atlit-Yam (Israeli coast) was destroyed in an event which also caused the sudden death of tens of inhabitants. Archaeological evidence and numerical simulations support the notion that the village was destroyed, ~8.3 ka B.P., by a tsunami triggered by a known Holocene flank collapse of Mt. Etna volcano (Italy). The filling of a water well within the village confirms inundation by a tsunami wave train and a sediment layer, composed of a clayed-sandy matrix and other detritus including reworked marine sediment, indicates tsunami inundation. This scenario shows that tsunamis generated by sector collapses from coastal volcanoes can seriously threaten near-shore settlements thousands of kilometres distant from the tsunami source.

  14. Late holocene vegetation change on Andros Island, Bahamas: Evidence of Caribbean climate change and human colonization

    SciTech Connect

    Kjhellmark, E. )

    1994-06-01

    Sediment cores from blue holes on Andros Island, Bahamas, contain a remarkably detailed record of the past vegetation. A Holocene dry period from at least 2000 to 1500 yr bp is evidenced by sedimentological and palynological facies from the basal portion of one core. The coincides with a suggested dry period in Central America and the Caribbean region, but it has never been found this far north and east. A hardwood vegetation is established at ca. 1500 yr bp and remains a dominant vegetation component until [approximately]900 yr bp when pine and charcoal begin to increase in abundance. At 750 yr bp, pinewoods replace the hardwoods and charcoal peaks indicating human disturbance. The 900 yr bp date for the onset of significant human disturbance is relatively late, compared with other estimates of human colonization of the Caribbean region, suggesting that the occupation of island interiors may have lagged behind that of the coastal regions.

  15. Land-level changes from a late Holocene earthquake in the northern Puget lowland, Washington

    USGS Publications Warehouse

    Kelsey, H.M.; Sherrod, B.; Johnson, S.Y.; Dadisman, S.V.

    2004-01-01

    An earthquake, probably generated on the southern Whidbey Island fault zone, caused 1-2 m of ground-surface uplift on central Whidbey Island ???2800-3200 yr ago. The cause of the uplift is a fold that grew coseismically above a blind fault that was the earthquake source. Both the fault and the fold at the fault's tip are imaged on multichannel seismic refection profiles in Puget Sound immediately east of the central Whidbey Island site. Uplift is documented through contrasting histories of relative sea level at two coastal marshes on either side of the fault. Late Holocene shallow-crustal earthquakes of Mw = 6.5-7 pose substantial seismic hazard to the northern Puget Lowland. ?? 2004 Geological Society of America.

  16. Revised Ages for Laminated Sediment and a Holocene-Marker Diatom from the Northern California Continental Slope

    USGS Publications Warehouse

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

    1994-01-01

    Conventional and accelerator mass spectrometry 14C ages indicate that laminated sediment in three cores from the northern California continental slope near 38??N and 39??N were deposited between 42,000 and 25,000 yr B.P. This revises and refines our previous estimates that laminated sediment accumulated during the late Pleistocene to early Holocene (J. V. Gardner and E. Hemphill-Haley, 1986, Geology 14, 691-694). Preservation of laminated sediment on the upper slope in this area suggests a period of intense coastal upwelling, high primary productivity, and resultant depletion of oxygen in bottomwaters preceding the onset of global glacial conditions. The transition from Pleistocene to Holocene conditions, and the establishment of a modern climatic regime driven by the California Current, included the incursion of the subtropical diatom, Pseudoeunotia doliola. P. doliola is common in sediment younger than about 10,000 yr and thus is a reliable marker species for identifying Holocene deposits off northern California.

  17. Mid-Holocene climate and land-sea interaction along the southern coast of Saurashtra, western India

    NASA Astrophysics Data System (ADS)

    Banerji, Upasana S.; Pandey, Shilpa; Bhushan, Ravi; Juyal, Navin

    2015-11-01

    The relict mudflat from the southern Saurashtra coast of Gujarat was investigated using geochemical and palynological analyses supported by radiocarbon dating to understand whether climate fluctuations and sea-level operated in tandem during mid-Holocene. The study revealed that the Saurashtra coast experienced relatively wet climatic conditions with simultaneous occurrence of marginally high sea-level between 4710 and 2825 cal yr BP. Subsequently, a gradual onset of aridity and lowering of the sea-level was observed between 2825 and 1835 cal yr BP, and further a slight decrease in aridity is observed after 1835 cal yr BP. The present day coastal configuration was probably achieved after around 1500 cal yr BP. Considering the tectonic instability of Saurashtra coast (land level changes), the effective mid-Holocene sea-level was estimated to be ∼1 m higher than the present. The study demonstrates that sea-level changes, climate variability and land-level changes were coupled during the mid-Holocene.

  18. Holocene climate and climate variability of the northern Gulf of Mexico and adjacent northern Gulf Coast: A review

    USGS Publications Warehouse

    Poore, Richard Z.

    2008-01-01

    Marine records from the northern Gulf of Mexico indicate that significant multidecadal- and century-scale variability was common during the Holocene. Mean annual sea-surface temperature (SST) during the last 1,400 years may have varied by 3°C, and excursions to cold SST coincide with reductions in solar output. Broad trends in Holocene terrestrial climate and environmental change along the eastern portion of the northern Gulf Coast are evident from existing pollen records, but the high-frequency details of climate variability are not well known. Continuous and well-dated records of climate change and climate variability in the western portion of the northern Gulf Coast are essentially lacking.Information on Holocene floods, droughts, and storm frequency along the northern Gulf Coast is limited. Records of floods may be preserved in continental shelf sediments, but establishing continuity and chronologies for sedimentary sequences on the shelf presents challenges due to sediment remobilization and redeposition during storms. Studies of past storm deposits in coastal lakes and marshes show promise for constructing records of past storm frequency. A recent summary of sea-level history of the northern Gulf Coast indicates sea level was higher than modern sea level several times during the last few thousand years.

  19. Middle Holocene Unconformity in Seneca Lake, NY

    NASA Astrophysics Data System (ADS)

    Curtin, T. M.; Crocker, M.; Loddengaard, K.

    2008-12-01

    The post-glacial history of the Finger Lakes, NY have involved several changes in lake levels throughout the latest Pleistocene and Holocene, resulting from the changing position of the retreating Laurentide ice sheet, river outlet position, glacial rebound, and water balance. Previous studies of high-resolution seismic reflection profiles from three Finger Lakes define a middle Holocene erosional surface at water depths as great as 26 m in the northern end of each of lake. There are two proposed hypotheses to explain the origin of the observed erosional surfaces: 1) subaerial erosion during a lake lowstand and 2) erosion resulting from increased internal seiche activity. To evaluate these hypotheses, we examined a series of 2 to 5 m long piston cores collected along a north-south transect from one of the Finger Lakes, Seneca Lake. Cores were correlated using distinctive changes in the profiles of grain size, loss-on-ignition, and magnetic susceptibility. We recognize a significant erosional unconformity of early to middle Holocene sediment at modern depths <60 m because portions of the normal deepwater sediment sequence were missing in cores and were commonly replaced by a thin zone of sand and abraded shells (bivalves, gastropods). At water depths >60 m, the unconformity continues as a conformable zone. We attribute the unconformity to wave abrasion and nearshore current winnowing of the shoreface during a lowstand. With an assumption of an effective 20 m wave base, the depth to the low level lake surface responsible for the unconformity is estimated to be 40 m. The age of the unconformity is ~6 ka, based on radiocarbon ages of lithologic boundaries in the sediment cores. Because the unconformity grades into a conformable zone in deepwater cores that display no change in lithology, we hypothesize that the large-scale lake level drop is likely not the result of climate change, but rather a change in accommodation space in the northern portion of the lake basin due

  20. 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

  1. Mediterranean Holocene climate, environment and human societies

    NASA Astrophysics Data System (ADS)

    Holmgren, Karin; Gogou, Alexandra.; Izdebski, Adam.; Luterbacher, Juerg.; Sicre, Marie-Alexandrine; Xoplaki, Elena

    2016-03-01

    This paper introduces the reader to a special issue of articles that explores links and processes behind societal change, climate change and environmental change in a Holocene perspective in the Mediterranean region. All papers are, by purpose, co-authored by scientists representing different disciplines. The cross-cutting theme has been to reach beyond simple explanations of potential climate-society relationships and advance our understanding on how to improve research methods and theories in the field. The thirteen papers in this issue address these questions in three different ways, by i) conceptual/methodological approaches; ii) review papers; and iii) case studies.

  2. Late Holocene morphodynamics in the littoral zone of the Iwik Peninsula area (Banc d'Arguin — Mauritania)

    NASA Astrophysics Data System (ADS)

    Barusseau, J. P.; Certain, R.; Vernet, R.; Saliège, J. F.

    2010-09-01

    In the littoral zone of the Banc d'Arguin both littoral sedimentary units and man-made deposits (shell-middens) abound. They were formed during the Late Holocene after the final onset of the post-glacial transgression. Here, a geo-archaeological approach is used to study them. The geomorphological and sedimentological characteristics of the coastal features define two distinct coastal sedimentary units in the Iwik-Aouatil zone between an ancient shoreline which formed on the Tafaritian substratum ca 6.7-5.7 cal. ka BP and the present one: (i) very extensive sand flats and (ii) linear relief features, both covered by a thin veneer of anthropogenic Anadara senilis shell-middens. They developed under a stable sea-level regime. The sand flats expanded at variable rates throughout the period. The linear relief features represent beach barriers and coastal dunes which can be dated archaeologically thanks to the superimposed shell-middens, supplemented by 14C dating. Two series of linear sedimentary units are identified. First, a complex north-south system of dunes and hook-ended sand barriers developed from 4.8 to 4.1 cal. ka BP and, secondly, two regular and linear beach barriers developed between 3.7 and 3.3 cal. ka BP. Their morphological characteristics suggest that they were generated through littoral drift processes. Directional changes observed between the first and the second groups demonstrate that the wave refraction pattern was dramatically modified after the closure of the strait between the former Iwik Island and the land. A comparison with the nearby Jerf el Oustani coastal area in the Late Holocene shows that both sites shared similarities in depositional patterns but also differences in the chronology of the sedimentary units. Processes involved in the development of the linear units are indicative of the enhancement of both sand influx and longshore drift due to climatic change.

  3. Magnitude and variability of Holocene sediment accumulation in Santa Monica Bay, California

    USGS Publications Warehouse

    Sommerfield, C.K.; Lee, H.J.

    2003-01-01

    The spatial variability of Holocene (past 10,000 years) sediment accumulation in Santa Monica Bay (California) was examined to identify controls sediment trapping in a bathymetrically complex coastal embayment and to provide geologic context for the post-industrial sedimentary record and associated pollution gradients. Sediment chronologies based on downcore AMS 14C dates were used to quantify long-term (millennia) accumulation rates in an effort to elucidate particle-transport pathways and sinks. Sediment accumulation rates for the full range of bayfloor environments (50-630 m water depths) range from 22 to 102 mg/cm2/year (15-88 mm/100 year), have an overall mean of 51??21 mg/cm2/year (1??, n=11), and are comparable to rates reported for adjacent borderland basins. Maximal accumulation rates on the Malibu shelf and within a reentrant to Redondo canyon are interpreted to reflect (1) proximity to sediment sources and (2) localized oceanographic and topographic conditions conducive to sediment trapping and deposition. The 14C-derived accumulation rates are 2-10 times lower than rates determined through 210Pb geochronology for the same sites in a related study, revealing that Holocene sediment accumulation has been non-steady-state. Santa Monica Bay is an important sink for suspended matter; averaged over the past several millennia a mass of sediment equivalent to 10-80% of the modern annual river supply is sequestered yearly. Net influx of suspended matter derived from the adjacent Palos Verdes shelf is evinced by a concentration gradient of p,p???-DDE in bayfloor sediments, whereas the distribution of anthropogenic silver suggests transport from Santa Monica shelf to the southeastern boundary of the bay. The results of this study provide new insight to the long-term fates of particulate matter in Los Angeles coastal waters. ?? 2003 Elsevier Science Ltd. All rights reserved.

  4. Outlet glaciers of southeast Greenland: rapid, synchronised regional retreat at the start of the Holocene?

    NASA Astrophysics Data System (ADS)

    Dyke, L. M.; Hughes, A. L.; Murray, T.; Ródes

    2012-12-01

    We report new in-situ cosmogenic isotope (10Be) exposure dates from two major fjord systems in southeast (SE) Greenland. Low elevation erratic pairs from Kangerdlugssuaq Fjord reveal the onset of coastal deglaciation at ~11 ky BP. Overlapping exposure ages from a fjord axis transect show this was followed by a period of rapid deglaciation to a position at least 50 km from the mouth. The rapid deglaciation of Kangerdlugssuaq Fjord taken together with similar dates from Sermilik Fjord situated ~350 km southwards (Hughes et al., 2012), shows synchronous coastal deglaciation. This regional synchronicity implies a common regional driving mechanism. Ice sheet retreat from the continental shelf was underway by 15 ky BP, probably in response to long term climate amelioration following the Last Glacial Maximum (LGM). We suggest that the 'fjord phase' of deglaciation occurred rapidly due to significant climatic amelioration and changing oceanic conditions at the end of the Younger Dryas stadial. To test the synchronicity of regional deglaciation further, we will report exposure ages and retreat rates from Bernstorffs Isfjord, 650 km south of Kangerdlugssuaq and 300 km south of Sermilik Fjord. Bathymetric data and geomorphological evidence from Bernstorffs Isfjord hint at a still-stand or re-advance during the Holocene: exposure dates will be used to test this hypothesis. Widespread changes have been reported in the marine terminating glaciers of the southeast sector of the Greenland Ice Sheet (GrIS) during the early 2000s. Our results show retreat rates that are either significantly faster or persist for much longer than those observed recently, and demonstrate the great sensitivity of these marine-terminating glaciers to climatic change. References: Hughes, A.L.C., Rainsley, E., Murray T., Fogwill, C.J., Schnabel, C. and Xu, S. (2012) Rapid response of Helheim Glacier, southeast Greenland, to early Holocene climate warming. Geology, 40, 427-430.

  5. Rapid anthropogenic response to short-term aeolian-fluvial palaeoenvironmental changes during the Late Pleistocene-Holocene transition in the northern Negev Desert, Israel

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Katra, Itzhak; Agha, Nuha; Goring-Morris, A. Nigel; Porat, Naomi; Barzilai, Omry

    2014-09-01

    Archaeological investigations along Nahal Sekher on the eastern edge of Israel's northwestern Negev Desert dunefield revealed concentrations of Epipalaeolithic campsites associated respectively with ancient water bodies. This study, aimed at better understanding the connections between these camps and the water bodies, is concerned with a cluster of Natufian sites. A comprehensive geomorphological study integrating field mapping, stratigraphic sections, sedimentological analysis and optically stimulated luminescence (OSL) ages was conducted in the vicinity of a recently excavated Natufian campsite of Nahal Sekher VI whose artifacts directly overlay aeolian sand dated by OSL to 12.4 ± 0.7 and 11.7 ± 0.5 ka. Residual sequences of diagnostic silty sediments, defined here as low-energy fluvial fine-grained deposits (LFFDs), were identified within the drainage system of central Nahal Sekher around the Nahal Sekher VI site. LFFD sections were found to represent both shoreline and mid-water deposits. The thicker mid-water LFFD deposits (15.7 ± 0.7-10.7 ± 0.5 ka) date within the range of the Epipalaeolithic campsites, while the upper and shoreline LFFD units that thin out into the sands adjacent to the Nahal Sekher VI site display slightly younger ages (10.8 ± 0.4 ka-7.6 ± 0.4 ka). LFFD sedimentation by low-energy concentrated flow and standing-water developed as a result of proximal downstream dune-damming. These water bodies developed as a result of encroaching sand that initially crossed central Nahal Sekher by 15.7 ± 0.7 ka and probably intermittently blocked the course of the wadi. LFFD deposition was therefore a response to a unique combination of regional sand supply due to frequent powerful winds and does not represent climate change in the form of increased precipitation or temperature change. The chronostratigraphies affiliate the Natufian sites to the adjacent ancient water bodies. These relations reflect a rapid, but temporary anthropogenic response to a

  6. Potential and limits of luminescence dating for establishing late-Holocene cyclone and tsunami chronologies

    NASA Astrophysics Data System (ADS)

    Brill, Dominik; May, Simon Matthias; Jankaew, Kruawun; Engel, Max; Brückner, Helmut

    2014-05-01

    Long-term recurrence intervals of coastal hazards such as tropical cyclones and tsunamis can be reconstructed on the basis of geological evidence of prehistoric events. These geological records have the potential to extend the period under observation beyond historical time scales. In addition to radiocarbon datings, optically stimulated luminescence (OSL) dating is used for the establishment of late-Holocene event chronologies. Here we discuss the potential and limits of applying OSL to sandy storm and tsunami deposits based on case studies from SW Thailand and NW Australia, where quartz luminescence properties (i.e., high sensitivity, thermally stable signal components dominated by the easily bleachable fast component, no mineralogical impurities) are favourable. Potential uncertainties and age offsets due to (i) incomplete signal resetting and (ii) spatial and temporal variations of dose rates that are supposed to be characteristic for deposits of coastal flooding events are evaluated. Incomplete bleaching of the OSL signal is evident in most deposits but can be corrected by statistical analysis of small aliquots or single grains using the minimum age model. Although the dating of modern analogues such as deposits from the 2004 Indian Ocean Tsunami revealed residuals, these uncertainties are insignificant compared to the respective local recurrence intervals. Further potential uncertainties arise from the complex coastal stratigraphies recording tsunami and cyclone deposits, such as variations between peat layers and sand sheets as well as differing concentrations of heavy minerals, but are comparably small if the geometry of different strata is adequately addressed. In contrast, errors introduced by temporal variations of environmental radiation fields may be much more significant. Especially changing water contents or radioactive disequilibria due to element mobility in marine carbonates are frequent in coastal settings and may lead to large uncertainties

  7. Alder Expansion as a Coastal Warming Signal - Linking Coastal Alaskan Carbon to Vegetation Change with Climate

    NASA Astrophysics Data System (ADS)

    Peteet, D. M.; Nichols, J. E.; Moy, C. M.; McGeachy, A.

    2014-12-01

    Corser Bog (60.5296364oN, 145.453858oW), 21 km east of Cordova, AK is a sphagnum-dominated peatland 42 m asl. adjacent to Sheridan Glacier and the Copper River Delta. Deglaciation at 11.5 ka began with shallow pond deposition, reflecting regional warmth with the pioneers Alnus crispa subsp. sinuata, Salix, and ferns colonizing the fresh, mineral soils on the landscape. Continued early Holocene warming/melting of glaciers led to the foundation species Alnus dominance and peatland formation, surrounded by shrubs such as Rubus spectabilis, Sambucus racemosa, and wetland species such as Myrica gale and Potentilla palustris. As Sphagnum peat accumulated, the highest rates of carbon accumulation for a few centuries are represented at 50 g/m2/a, similar to short-term very high rates in the early Holocene throughout the circumboreal region but varying within the early Holocene due to development of local wet, bryophytic environments. A shift to sedge peat regionally along the South-Central Alaskan coast 7.6 - 3.7 ka is paralleled by a more evaporative, drier climate with Rhododendron groenlandicum presence, lower carbon accumulation (13 g/m2/a), and minimal macrofossil preservation, which is paralleled regionally in coastal muskegs both to the northwest and southeast and by a hiatus in a nearby lake record. A cooler, moister climate is evident in Corser Bog with the shift to Sphagnum peat at 3.7 ka, regional shifts from sedge to Sphagnum peat throughout the entire coastline from Yakutat to Girdwood, AK and the demonstration of glacial advances in the region. Alnus pollen markedly increases to 60% in the uppermost sample, indicative of a major signal for glacial recession in this region.

  8. Subsidence along the Atlantic Coast of the United States: Insights from GPS and late Holocene relative sea level data

    NASA Astrophysics Data System (ADS)

    A Karegar, M.; Engelhart, S. E.; Dixon, T. H.

    2015-12-01

    Subsidence along the Atlantic coast of the United States is the largest amplitude collapse of a pro-glacial forebulge on Earth. High-quality geological records of late Holocene Relative Sea Level (RSL) are now available for this region. These data provide an independent constraint on Glacial Isostatic Adjustments (GIA), for comparison to continuous GPS measurements that directly measure net vertical crustal motion from GIA and other processes. Installation of more than 130 permanent GPS stations since 2006 represents an improvement towards precise determination of present-day subsidence rates along the coastal plain. We present an improved vertical velocity field for the eastern seaboard of the U.S. and parts of Atlantic Canada with uncertainty estimates that incorporate time-correlated noise. We use the geologic rates of RSL as an independent constraint to separate the long-term GIA-induced displacement (average motion over past 4 ka) from the GPS vertical displacement (average of one or two decades). Differences between the two are important for mitigating coastal land loss and predicting future storm surge inundation. Our results indicate that for most areas of the U.S. eastern seaboard there is no difference between GPS rates and late Holocene RSL rates. Exceptions are related to areas of recent excessive groundwater extraction in Virginia and South Carolina. The present-day subsidence rates in these areas are approximately double the long-term geologic rates.

  9. The importance of radiocarbon dates and tephra for developing chronologies of Holocene environmental changes from lake sediments, North Far East

    DOE PAGES

    Lozhkin, Anatoly V.; Brown, Thomas A.; Anderson, Patricia M.; ...

    2016-08-12

    One problem with developing continuous chronologies of paleoenvironmental change in northern areas of the Far East using 14C is the low organic content in lake sediments. However, Holocene age-models can be supplemented by widespread tephra deposits reported in the Magadan region. The best documented of these tephras has been correlated to the KO tephra from southern Kamchatka dated to 7600 BP. Though a key chronostratigraphic marker, no detailed compendium of the distribution of this tephra and its associated 14C dates has been available from sites in the northern Far East. We provide such a summary. Known locally as the Elikchanmore » tephra, lake cores indicate an ash fall that extended ~1800 km north of the Kamchatkan caldera with a ~500 km wide trajectory in the Magadan region. Other Holocene tephras preserved in lake sediments have poorer age control and possibly date to ~2500 BP, ~2700 BP and ~6000 BP. These ashes seem to be restricted to coastal or near-coastal sites. Finally, a single record of a ~25,000 BP tephra has also been documented ~100 km to the northeast of Magadan.« less

  10. The importance of radiocarbon dates and tephra for developing chronologies of Holocene environmental changes from lake sediments, North Far East

    SciTech Connect

    Lozhkin, Anatoly V.; Brown, Thomas A.; Anderson, Patricia M.; Glushkova, Olga Yu; Melekestsev, Ivan V.

    2016-08-12

    One problem with developing continuous chronologies of paleoenvironmental change in northern areas of the Far East using 14C is the low organic content in lake sediments. However, Holocene age-models can be supplemented by widespread tephra deposits reported in the Magadan region. The best documented of these tephras has been correlated to the KO tephra from southern Kamchatka dated to 7600 BP. Though a key chronostratigraphic marker, no detailed compendium of the distribution of this tephra and its associated 14C dates has been available from sites in the northern Far East. We provide such a summary. Known locally as the Elikchan tephra, lake cores indicate an ash fall that extended ~1800 km north of the Kamchatkan caldera with a ~500 km wide trajectory in the Magadan region. Other Holocene tephras preserved in lake sediments have poorer age control and possibly date to ~2500 BP, ~2700 BP and ~6000 BP. These ashes seem to be restricted to coastal or near-coastal sites. Finally, a single record of a ~25,000 BP tephra has also been documented ~100 km to the northeast of Magadan.

  11. Late Holocene sea level changes along the coast of Southwestern Turkey

    NASA Astrophysics Data System (ADS)

    Kızıldaǧ, Nilhan; Özdaş, Harun; Özel, Erdeniz

    2014-05-01

    A multi-disciplinary survey has been performed along the coast of southwestern Turkey in order to determine relative sea level changes during the Late Holocene. Especially, the submergence of harbour structures of the ancient coastal settlements provides noticeable evidence for eustatic sea level rise and/or tectonic subsidence. In addition, the traces of bioerosion produced by some organisms along the limestone coasts formed at mean sea level position represent a remarkable data of paleoshorelines. These traces can be found below the current sea level nowadays due to relative sea level rise. Both archaeological and biological data provide an important source on the amount and period of relative sea level rise along the coasts of southwestern Turkey-southeastern Aegean Sea. This region is under the influence of active tectonism as a result of the collision of the Arab-African and Eurasian plates. Thus, a large number of earthquakes have occurred in this zone which must have been an impact on submergence of ancient harbour structures and geomorphological formations. This area is located very important zone in terms of being tectonically active, having a large number of ancient coastal settlements, and consisting of limestone lithology. A number of submerged archaeological structures and bioerosion formations have been investigated by measuring the depths of remains with respect to the present sea level. By comparing the eustatic sea level change, current elevations and construction time of archaeological remains, which dated taking into account construction techniques and ceramic findings, we determine the amount of relative sea level change. In addition, numerous active faults have been detected by performing seismic survey. The results indicate that the vertical tectonic movement has much more effect on submergence of archaeological and geomorphological features than eustatic sea level rise. Uncovering the role of the tectonic movement and sea level changes on the

  12. Central Greenland Holocene Deuterium Excess Variability

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Jouzel, J.; Falourd, S.; Cattani, O.; Dahl-Jensen, D.; Johnsen, S.; Sveinbjornsdottir, A. E.; White, J. W. C.

    Water stable isotopes (oxygen 18 and deuterium) have been measured along the Holocene part of two deep ice cores from central Greenland, GRIP and North GRIP. Theoretical studies have shown that the second-order isotopic parameter, the deu- terium excess (d=dD-8d18O), is an indicator of climatic changes at the oceanic mois- ture source reflecting at least partly changes in sea-surface-temperature. The two deu- terium excess records from GRIP and North GRIP show a long term increasing trend already observed in Antarctic deep ice cores and related to changes in the Earth's obliquity during the Holocene : an decreased obliquity is associated with a larger low to high latitude annual mean insolation gradient, warmer tropics, colder poles, and a more intense atmospheric transport from the tropics to the poles, resulting in a higher moisture source temperature and higher deuterium excess values. Superimposed onto this long term trend, central Greenland deuterium excess records also exhibit small abrupt events (8.2 ka BP and 4.5 ka BP) and a high frequency variability.

  13. Reconstruction of late Holocene flooding events in the Gulf of Genoa, Ligurian Sea

    NASA Astrophysics Data System (ADS)

    Lamy, Frank; Kaiser, Jerome; Arz, Helge; Ruggieri, Nicoletta

    2014-05-01

    The area of the Gulf of Genoa contains a large potential for studying past rainfall variability as it is one of the major Mediterranean centers for cyclogenesis. The strongest depressions form when cold arctic/subarctic air outbreaks flow through the Rhone valley into the Gulf of Lions and the Ligurian Sea during late autumn when sea surface temperatures are still relatively high. The cyclones are more frequent during negative Arctic Oscillation / North Atlantic Oscillation (AO/NAO). As well, significant negative correlations exist between AO/NAO and winter/spring precipitation and river discharge in northwestern Italy. Related autumn flooding events occur at interannual time-scales and may cause substantial damage in the region. Moreover, the "Genoa Cyclones" sometimes move northeastwards into eastern/central Europe (the so-called "Vb" cyclone track) and contributed for example substantially to the Elbe flooding in 2002. During R/V Poseidon cruise P413 (May 2011), ca. 60 sediment cores were taken along the Ligurian shelf, continental slope and in the basin between off Livorno and the French border. Coring profiles from the coastal area to the deep basin allow reconstructing past environmental variability over the last ca. 90000 years with sedimentation rates varying between ca. 0.5 cm*yr-1 for the latest Holocene to ca. 10 cm*kyr-1 for the last glacial. On the shelf, mud lenses with exceptionally high sedimentation rates reaching several m/kyr provide detailed Holocene records of changes in terrigenous sediment input primarily related to autumn rainfall events. We performed high resolution (mm) analyses of major elements using XRF core-scanning on two cores with extremely high resolution (0.2-0.4 cm/year) over the last 2.5 kyr BP. Typical elements of detrital origin (i.e. Ti, Fe) present a very high variability, probably related to flooding events during the late Holocene. Spectral analysis on these records reveals significant periodicities around 4-5 and 7

  14. Optical dating of late Holocene storm surges from Schokland (Noordoostpolder, the Netherlands)

    NASA Astrophysics Data System (ADS)

    van den Biggelaar, Don; Kluiving, Sjoerd; van Balen, Roland; Kasse, Cronelils; Troelstra, Simon; Prins, Maarten; Wallinga, Jakob; Versendaal, Alice

    2015-04-01

    Storm surges have a major impact on land use and human habitation in coastal regions. Our understanding of this impact can be improved by correlating long-term historical storm records with sedimentary evidence of storm surges, but so far few studies use such an approach. Here we present detailed geological and historical data on late Holocene storm surges from the former island Schokland, located in the northern part of Flevoland (central Netherlands). During the late Holocene, Schokland transformed from a peat area that gradually inundated (~1200 yr ago) via an island in a marine environment (~400 yr ago) to a land-locked island in the reclaimed Province of Flevoland (~70 yr ago). Deposits formed between 1200 and 70 year ago on lower parts of the island, consist of a stacked sequence of clay and sand layers, with the latter being deposited during storm surges. We dated the sandy laminae of late Holocene storm surges in the clay deposit on Schokland to improve the age model of the island's flooding history during the last 1200 years. Samples for dating were obtained from a mechanical core at Schokland. The top of the peat underlying the clay and sand deposits was dated using 14C accelerator mass spectrometry (AMS) of terrestrial plant and seed material. Sandy intervals of the flood deposits were dated using a series of ten quartz OSL ages, which were obtained using state-of-the-art methods to deal with incomplete resetting of the OSL signal. These new dates, together with laboratory analyses on the clay deposit (thermogravimetric analysis, grain-size analyses, foraminifera, bivalves and ostracods) and a literature study show that storm surges had a major impact on both the sedimentary and the anthropogenic history of Schokland. The results show that the stacked clay sequence is younger than expected, indicating either an increasing sedimentation rate or reworking of the clay by storm surges. Furthermore, the results indicate that a correlation can be made between

  15. New constraints on late Holocene eustatic sea-level changes from Mahé, Seychelles

    NASA Astrophysics Data System (ADS)

    Woodroffe, Sarah A.; Long, Antony J.; Milne, Glenn A.; Bryant, Charlotte L.; Thomas, Alexander L.

    2015-05-01

    This study provides new estimates of globally integrated ice sheet melt during the late Holocene (since 4 ka BP) from Seychelles in the western Indian Ocean, a tectonically stable, far field location where the necessary Glacial-Isostatic Adjustment (GIA) correction is small and is relatively insensitive to predictions using different Earth viscosity profiles. We compare sea level data from Seychelles to estimates of eustasy from two GIA models, ICE-5G and EUST3, which represent end-members in the quantity of global melt during the late Holocene. We use data from a range of coastal environments including fringing reef, present day beaches, fossil plateau and mangrove deposits on the largest island of the Seychelles archipelago, Mahé to reconstruct relative sea-level changes. Our data suggest that extensive coastal deposits of carbonate-rich sands that fringe the west coast formed in the last 2 ka and the horizontal nature of their surface topography suggests RSL stability during this period. Mangrove sediments preserved behind these deposits and in river mouths date to c. 2 ka and indicate that RSL was between -2 m and present during this interval. Correcting the reconstructed sea level data using a suite of optimal GIA models based on the two ice models mentioned above and a large number (c. 350) of Earth viscosity models gives a result that is consistent with the sedimentological constraints. When uncertainties in both model results and data are considered, it is possible to rule out eustatic sea levels below c. 2 m and more than a few decimetres above present during the past two millennia. This uncertainty is dominated by error in the reconstructions rather than the model predictions. We note, however, that our estimates of eustasy are more compatible with the EUST3 model compared to the ICE-5G model during the late Holocene (2-1 ka BP). Our evidence from Seychelles shows that the timing of when eustatic sea level first rose close to present is between the

  16. Holocene vegetation, environment and anthropogenic influence in the Fuzhou Basin, southeast China

    NASA Astrophysics Data System (ADS)

    Yue, Yuanfu; Zheng, Zhuo; Rolett, Barry V.; Ma, Ting; Chen, Cong; Huang, Kangyou; Lin, Gongwu; Zhu, Guangqi; Cheddadi, Rachid

    2015-03-01

    A ∼40 m sediment core (FZ4) was collected from the Fuzhou Basin, near the lower reaches of the Min River, in Fujian Province on the southeast coast of China. The sediment and pollen record contributes to our understanding of Holocene paleogeography, including local changes in vegetation and climate in the context of Neolithic cultural developments. The sediment record reveals a fluvial environment in the Fuzhou Basin during the late Pleistocene, and it demonstrates that a change from fluvial to estuarine conditions at ∼9000 cal yr BP resulted from postglacial sea level rise. Evidence of abundant marine diatoms and tidal flat laminations observed in the FZ4 sediments, implies that the Fuzhou Basin was under marine influence between ∼9000 and ∼2000 cal yr BP. After 2000 cal yr BP, a rapid retreat in coastline associated with fluvial aggradation and coastal progradation produced more shallow water for wetlands and initiated formation of the floodplain landscape. The pollen record reveals the presence of a dense subtropical forest between ca. 9000 and 7000 cal yr BP, representing the Holocene thermal maximum, which is linked with rising sea level and marine transgression in the Fuzhou Basin. Between ca. 5500 and 2000 cal yr BP, the thermophilous forest dominated by Castanopsis retreated and coniferous forest expanded, reflecting moderate climatic cooling during this period. Timing of the high frequencies for Pinus and ferns correspond with the mid-late Holocene cooling trend recorded in local mountain peatland and coastal regions of the lower Yangtze and Hanjiang deltas. Anthropogenically induced land cover change was negligible prior to the Tanshishan cultural period, which marks the beginning of Neolithic era sedentary village life on the Fujian coast around 5500 BP. The pollen transition at ca. 3000-1500 cal yr BP, distinguished by rising frequencies of Poaceae and taxa (including Cyperaceae and Artemisia) closely associated with agricultural land cover

  17. Coastal Modeling System

    DTIC Science & Technology

    2014-09-04

    Coastal Inlets Research Program Coastal Modeling System The work unit develops the Coastal Modeling System ( CMS ) and conducts basic research to...further understanding of sediment transport under mixed forcing from waves and currents. The CMS is a suite of coupled two- dimensional numerical...models for simulating waves, hydrodynamics, salinity and sediment transport, and morphology change. The CMS was identified by the USACE Hydraulics and

  18. Holocene climatic variations in the Western Cordillera of Colombia: A multiproxy high-resolution record unravels the dual influence of ENSO and ITCZ

    NASA Astrophysics Data System (ADS)

    Muñoz, Paula; Gorin, Georges; Parra, Norberto; Velásquez, Cesar; Lemus, Diego; Monsalve-M., Carlos; Jojoa, Marcela

    2017-01-01

    The Páramo de Frontino (3460 m elevation) in Colombia is located approximately halfway between the Pacific and Atlantic oceans. It contains a 17 kyr long, stratigraphically continuous sedimentary sequence dated by 30 AMS 14C ages. Our study covers the last 11,500 cal yr and focuses on the biotic (pollen) and abiotic (microfluorescence-X or μXRF) components of this high mountain ecosystem. The pollen record provides a proxy for temperature and humidity with a resolution of 20-35 yr, and μXRF of Ti and Fe is a proxy for rainfall with a sub-annual (ca. 6-month) resolution. Temperature and humidity display rapid and significant changes over the Holocene. The rapid transition from a cold (mean annual temperature (MAT) 3.5 °C lower than today) and wet Younger Dryas to a warm and dry early Holocene is dated at 11,410 cal yr BP. During the Holocene, MAT varied from ca. 2.5 °C below to 3.5° above present-day temperature. Warm periods (11,410-10,700, 9700-6900, 4000-2400 cal yr BP) were separated by colder intervals. The last 2.4 kyr of the record is affected by human impact. The Holocene remained dry until 7500 cal yr BP. Then, precipitations increased to reach a maximum between 5000 and 4500 cal yr BP. A rapid decrease occurred until 3500 cal yr BP and the late Holocene was dry. Spectral analysis of μXRF data show rainfall cyclicity at millennial scale throughout the Holocene, and at centennial down to ENSO scale in more specific time intervals. The highest rainfall intervals correlate with the highest activity of ENSO. Variability in solar output is possibly the main cause for this millennial to decadal cyclicity. We interpret ENSO and ITCZ as the main climate change-driving mechanisms in Frontino. Comparison with high-resolution XRF data from the Caribbean Cariaco Basin (a proxy for rainfall in the coastal Venezuelian cordilleras) demonstrates that climate in Frontino was Pacific-driven (ENSO-dominated) during the YD and early Holocene, whereas it was Atlantic

  19. Past and Future Ecosystem Change in the Coastal Zone

    NASA Astrophysics Data System (ADS)

    Gell, P.

    2017-02-01

    The coastal zone is in a constant state of flux. Long term records of change attest to high amplitude sea level changes. Relative stability though the Late Holocene has allowed for the evolution of barrier dune systems, estuaries and coastal lakes with associated plant and faunal associations. This evolution has been interspersed with changes in the balance between climate driven changes in outflow from catchments. These interactions have been considerably disturbed through the impacts of industrialised people who have diverted and consumed water and invested in infrastructure that has impacted on river flows and the tidal prism in estuaries. This has impacted their provisioning services to humans. It has also impacted their regulating services in that development along the coastline has impacted on the resilience of the littoral zone to absorb natural climate extremes. Looking from the past we can see the pathway to the future and more easily recognise the steps needed to avoid further coastal degradation. This will increasingly need to accommodate the impacts of future climate trends, increased climate extremes and rising seas. Coastal societies would do well to identify their long term pathway to adaptation to the challenges that lie ahead and plan to invest accordingly.

  20. NATIONAL COASTAL CONDITION REPORT III

    EPA Science Inventory

    Coastal waers in the US include estuaries, coastal wetlands, coral reefs, ,mangrove and kelp forests, seagrass meadows, and upwelling areas. Critical coastal habitats provide spawning grounds, nurseries, shelter, and food for finfish, shellfish, birds, and other wildlife. The n...

  1. Holocene depositional history of a large glaciated estuary, Penobscot Bay, Maine

    USGS Publications Warehouse

    Knebel, H. J.

    1986-01-01

    Data from seismic-reflection profiles, sidescan sonar images, and sediment samples reveal the Holocene depositional history of the large (1100 km2) glaciated Penobscot Bay estuary of coastal Maine. Previous work has shown that the late Wisconsinan ice sheet retreated from the three main passages of the bay between 12,700 and 13,500 years ago and was accompanied by a marine transgression during which ice and sea were in contact. Isostatic recovery of the crust caused the bay to emerge during the immediate postglacial period, and relative sea level fell to at least -40 m sometime between 9000 and 11,500 years ago. During lowered sea level, the ancestral Penobscot River flowed across the subaerially exposed head of the bay and debouched into Middle Passage. Organic-matter-rich mud from the river was deposited rapidly in remnant, glacially scoured depressions in the lower reaches of Middle and West Passages behind a shallow (???20 m water depth) bedrock sill across the bay mouth. East Passage was isolated from the rest of the bay system and received only small amounts of locally derived fine-grained sediments. During the Holocene transgression that accompanied the eustatic rise of sea level, the locus of sedimentation shifted to the head of the bay. Here, heterogeneous fluvial deposits filled the ancestral valley of the Penobscot River as base level rose, and the migrating surf zone created a gently dipping erosional unconformity, marked by a thin (<2 m) lag deposit of coarse sand and gravel. As sea level continued to rise, a thin (???9 m) layer of acoustically transparent muddy sediments accumulated over a shallow platform in the eastern half of the bay head. Graded sediments within this stratum began to accumulate early in the transgression, and they record both the decrease in energy conditions and the waning influence of the Penobscot River at the head of the bay. In contrast, relatively thick (up to 25 m) silty clays accumulated within a subbottom trough in the

  2. Stratigraphic and sedimentologic response to Late Quaternary climate change and glacio-eustasy, Colorado River, Gulf Coastal Plain of Texas

    SciTech Connect

    Blum, M.D. . Dept. of Geology)

    1992-01-01

    This paper summarizes results of investigations of the Colorado River, Gulf Coastal Plain of Texas, which provides a detailed record of fluvial response to late Quaternary climatic change and glacio-eustatic sea level rise. Four allostratigraphic units of late Pleistocene through modern age are differentiated in the bedrock-confined lower Colorado valley on the Inner Coastal Plain. Here up to 10 meters of late Pleistocene sediments underlie a terrace at 17--20 meters above the present-day channel. Two distinct allostratigraphic units underlie an extensive Holocene terrace at 12--14 meters above the present-day channel. Allostratigraphic units and bounding disconformities correlate with climatic changes that have been identified from paleobiological data, and represent stratigraphic response to changes in the relationship between discharge and sediment supply. In addition, changes in sedimentary facies through time represents a response to changes in climate coupled with a protracted degradation of upland soil mantles. This degradation of soils altered the rate at which precipitation inputs were transferred to stream channels as runoff, which led to increases in the peakedness of flood hydrographs and changes in the relative importance of channel versus floodplain depositional environments. Increased flood stages during the late Holocene promoted the increasing importance of floodplain construction by vertical accretion, and late Holocene to modern allostratigraphic units contain thick vertical accretion facies. These same allostratigraphic units and component facies persist downvalley to the Outer Coastal Plain, but stratigraphic architecture changes as a result of the last glacio-eustatic cycle. Here late Holocene and modern sediments onlap and bury late Pleistocene and early to middle Holocene stratigraphic units that were emplaced during the last sea level lowstand and the transgression that followed.

  3. Holocene evolution and sedimentation rate of Alikes Lagoon, Zakynthos island, Western Greece: preliminary results

    NASA Astrophysics Data System (ADS)

    Avramidis, P.; Kontopoulos, N.

    2009-07-01

    In the present study we present preliminary results from Alikes lagoon in Zakynthos island, an area that is one of the most seismically active regions of Greece. In order to estimate - interpret the Holocene evolution of the area and to reconstruct the palaeoenvironmental changes, we based on data derived from a 21 m sediment core. Sediment types, structure, colour, as well as contact depths and bed characteristics were recorded in the field. Standarised sedimentological analysis was carried out, on 46 samples including grain size analysis, calculation of moment measures, and micro- and molluscan fossils of 17 selected samples. Moreover, radiocarbon age determinations have been made on individual Cardium shells from two horizons and whole - core Magnetic Susceptibility (MS) measurements were taken. The interpretation of depositional environments suggests a coastal environment (restricted-shallow) with reduced salinity such as a lagoon margin and in a tidal flat and/or marsh particularly. The maximum age of the studied sediments is about 8500 BP. The rate of sedimentation between 8280 BP while 5590 BP was 5.3 mm/yr and between 5590 BP and modern times is on the order of 1.03 mm/yr. These sedimentation rates results are similar to other coastal areas of western Greece.

  4. Macrofossil records of West Antarctic Ice Sheet retreat during the Holocene

    NASA Technical Reports Server (NTRS)

    Berkman, Paul Arthur

    1993-01-01

    Marine macrofossils in emerged beaches around Antarctica represent a geochemical framework for interpreting meltwater signatures associated with variations in the adjacent ice sheet margins during the last 10,000 years. In particular, mollusc species provide ideal experimental templates for assessing hydrochemical variations in Antarctic coastal marine environments because of their excellent preservation, high abundances, circumpolar distributions, and carbonate shells, which incorporate trace elements and stable isotopes. Modern samples of the bivalve Adamussium colbecki, which were collected across a depth gradient in the vicinity of a glacial meltwater stream in West McMurdo Sound, revealed shell trace element concentrations that were significantly higher above 10 meters because of their exposure to meltwater runoff. This meltwater signature also was reflected by the shell oxygen isotopic composition, which was in equilibrium with the ambient seawater, as demonstrated by the overlap between the predicted and actual O-(delta-18)sub w values. These modern samples provide analogs for interpreting the geochemical records in their fossils, which were based solely on molluscan fossils, complement the above geochemical data by suggesting that the rate of beach emergence fluctuated around Antarctica during the mid-Holocene. Paleoenvironmental analysis of macrofossils from emerged beaches represents a new direction in Antarctic research that can be used to assess changes in the margins of the ice sheets since the Last Glacial Maximum. The resolution of these analyses will be enhanced by collaborations that are developing with scientists who are conducting comparable studies in other coastal regions around the continent.

  5. Stature in Holocene foragers of North India.

    PubMed

    Lukacs, John R; Pal, J N; Nelson, Greg C

    2014-03-01

    The Ganga Plain of North India provides an archaeological and skeletal record of semi-nomadic Holocene foragers in association with an aceramic Mesolithic culture. Prior estimates of stature for Mesolithic Lake Cultures (MLC) used inappropriate equations from an American White reference group and need revision. Attention is given to intralimb body proportions and geo-climatic provenance of MLC series in considering the most suitable reference population. Regression equations from ancient Egyptians are used in reconstructing stature for MLC skeletal series from Damdama (DDM), Mahadaha (MDH), and Sarai Nahar Rai (SNR). Mean stature is estimated at between 174 (MDH) and 178 cm (DDM and SNR) for males, and between 163 cm (MDH) and 179 cm (SNR) for females. Stature estimates based on ancient Egyptian equations are significantly shorter (from 3.5 to 7.1 cm shorter in males; from 3.2 to 7.5 cm shorter in females) than estimates using the American White reference group. Revised stature estimates from tibia length and from femur + tibia more accurately estimate MLC stature for two reasons: a) these elements are highly correlated with stature and have lower standard estimates of error, and b) uncertainty regarding methods of measuring tibia length is avoided. When compared with Holocene samples of native Americans and Mesolithic Europeans, MLC series from North India are tall. This aspect of their biological variation confirms earlier assessments and results from the synergistic influence of balanced nutrition from broad-spectrum foraging, body-proportions adapted to a seasonally hot and arid climate, and the functional demands of a mobile, semi-nomadic life-style.

  6. Controls on fire activity over the Holocene

    NASA Astrophysics Data System (ADS)

    Kloster, S.; Brücher, T.; Brovkin, V.; Wilkenskjeld, S.

    2014-11-01

    Changes in fire activity over the last 8000 years are simulated with a global fire model driven by changes in climate and vegetation cover. The changes were separated into those caused through variations in fuel availability, fuel moisture or wind speed which react differently to changes in climate. Disentangling these controlling factors helps to understand the overall climate control on fire activity over the Holocene. Globally the burned area is simulated to increase by 2.5% between 8000 and 200 cal yr BP with larger regional changes compensating on a global scale. Despite the absence of anthropogenic fire ignitions, the simulated trends in fire activity agree reasonably well with continental scale reconstructions from charcoal records, with the exception of Europe. For some regions the change in fire activity is predominantly controlled through changes in fuel availability (Australia-Monsoon, American Tropics/Subtropics). For other regions changes in fuel moisture are more important for the overall trend in fire activity (North America, Sub-Saharan Africa, Europe, Asia-Monsoon). In Sub-Saharan Africa, for example, changes in fuel moisture alone lead to an increase in fire activity between 8000 and 200 cal yr BP, while changes in fuel availability lead to a decrease. Overall, the fuel moisture control is dominating the simulated fire activity for Sub-Saharan Africa. The simulations clearly demonstrate that both changes in fuel availability and changes in fuel moisture are important drivers for the fire activity over the Holocene. Fuel availability and fuel moisture do, however, have different climate controls. As such observed changes in fire activity can not be related to single climate parameters such as precipitation or temperature alone. Fire models, as applied in this study, in combination with observational records can help to understand the climate control on fire activity, which is essential to project future fire activity.

  7. Controls on fire activity over the Holocene

    NASA Astrophysics Data System (ADS)

    Kloster, S.; Brucher, T.; Brovkin, V.; Wilkenskjeld, S.

    2015-05-01

    Changes in fire activity over the last 8000 years are simulated with a global fire model driven by changes in climate and vegetation cover. The changes were separated into those caused through variations in fuel availability, fuel moisture or wind speed, which react differently to changes in climate. Disentangling these controlling factors helps in understanding the overall climate control on fire activity over the Holocene. Globally the burned area is simulated to increase by 2.5% between 8000 and 200 cal yr BP, with larger regional changes compensating nearly evening out on a global scale. Despite the absence of anthropogenic fire ignitions, the simulated trends in fire activity agree reasonably well with continental-scale reconstructions from charcoal records, with the exception of Europe. For some regions the change in fire activity is predominantly controlled through changes in fuel availability (Australia monsoon, Central America tropics/subtropics). For other regions changes in fuel moisture are more important for the overall trend in fire activity (North America, Sub-Saharan Africa, Europe, Asia monsoon). In Sub-Saharan Africa, for example, changes in fuel moisture alone lead to an increase in fire activity between 8000 and 200 cal yr BP, while changes in fuel availability lead to a decrease. Overall, the fuel moisture control is dominating the simulated fire activity for Sub-Saharan Africa. The simulations clearly demonstrate that both changes in fuel availability and changes in fuel moisture are important drivers for the fire activity over the Holocene. Fuel availability and fuel moisture do, however, have different climate controls. As such, observed changes in fire activity cannot be related to single climate parameters such as precipitation or temperature alone. Fire models, as applied in this study, in combination with observational records can help in understanding the climate control on fire activity, which is essential to project future fire

  8. The Holocene palaeogeography and relative sea level for two tidal basins of the German North Sea coast

    NASA Astrophysics Data System (ADS)

    Bungenstock, Friederike; Wartenberg, Wolfram; Mauz, Barbara; Freund, Holger; Frechen, Manfred; Weerts, Henk J. T.; Berner, Heinrich

    2014-05-01

    The response of coasts to global sea-level rise is highly variable. Knowledge of driving coastal parameters alongside the regional sea-level history is therefore indispensable when the response to global sea-level rise is to be assessed. Here, we study the Holocene relative sea-level of the south coast of the North Sea which is controlled by a number of very local parameters, as well as by regional glacio-isostatic adjustments. It is therefore crucial to restrict the data acquisition and evaluation to small coastal sections, ideally to single tidal basins, to minimize the sources of uncertainties (Bungenstock & Weerts 2010, 2012). We present data from two tidal basins, Langeoog and Jade Bay. For Langeoog a database derived from 600 cores, 68 km of Boomer seismic data, 33 radiocarbon ages and 8 OSL dates is available. (Bungenstock & Schäfer 2009, Mauz & Bungenstock 2007). For the Jade bay, the database comprises sedimentary markers, pollen and macro remains derived from 68 cores. The sedentary chronology is based on 54 radiocarbon ages and pollen constraints (Wartenberg & Freund 2011, Wartenberg et al. 2013). For both tidal basins the sedimentological record was interpreted in terms of the local paleogeographical development since about 7000 cal BP and its influence on the local relative sea-level curve. While the trend of the relative sea level is similar for both tidal basins, it shows a different altitude. The timing of the main marine transgression within the Langeoog area takes place ~3000 cal. BP whereas the sedimentological record of the Jade Bay shows two prominent transgressions, one for ~5000 cal. BP and one for ~3000 cal. BP. The Langeoog palaeo-environment is continuously characterised by marine influence. Within the Jade Bay two different palaeo-environments could be identified, documenting that from the West to the centre the landscape development in the Jade Bay was drainage driven feeding the associated fen peat with minerogenic water but being

  9. NATIONAL COASTAL CONDITION REPORT

    EPA Science Inventory

    The National Coastal Condition report compiles several available data sets from different agencies and areas of the country and summarizes them to present a broad baseline picture of the condition of coastal waters. Although data sets presented in this report do not cover all coa...

  10. Resilience from coastal protection.

    PubMed

    Ewing, Lesley C

    2015-10-28

    Coastal areas are important residential, commercial and industrial areas; but coastal hazards can pose significant threats to these areas. Shoreline/coastal protection elements, both built structures such as breakwaters, seawalls and revetments, as well as natural features such as beaches, reefs and wetlands, are regular features of a coastal community and are important for community safety and development. These protection structures provide a range of resilience to coastal communities. During and after disasters, they help to minimize damages and support recovery; during non-disaster times, the values from shoreline elements shift from the narrow focus on protection. Most coastal communities have limited land and resources and few can dedicate scarce resources solely for protection. Values from shore protection can and should expand to include environmental, economic and social/cultural values. This paper discusses the key aspects of shoreline protection that influence effective community resilience and protection from disasters. This paper also presents ways that the economic, environmental and social/cultural values of shore protection can be evaluated and quantified. It presents the Coastal Community Hazard Protection Resilience (CCHPR) Index for evaluating the resilience capacity to coastal communities from various protection schemes and demonstrates the use of this Index for an urban beach in San Francisco, CA, USA.

  11. Coastal zone management

    NASA Technical Reports Server (NTRS)

    Tilton, E. L., III

    1975-01-01

    A panel of federal and state representatives concerned with coastal zone affairs discussed their problems in this area. In addition, several demonstrations of the application of remote sensing technology to coastal zone management were described. These demonstrations were performed by several agencies in a variety of geographical areas.

  12. NATIONAL COASTAL ASSESSMENT

    EPA Science Inventory

    The purpose of the National Coastal Assessment (NCA) is to estimate the status and trends of the condition of the nation's coastal resources on a state, regional and national basis. Based on NCA monitoring from 1999-2001, 100% of the nation's estuarine waters (at over 2500 locati...

  13. The Pleistocene-Holocene Unconformity in California Prehistory

    NASA Astrophysics Data System (ADS)

    Jones, T. L.

    2007-05-01

    The earliest archaeological record from California shows a dramatic unconformity or cultural hiatus between the terminal Pleistocene and the early Holocene. Clovis-like fluted projectile points which mark initial human colonization ca. 13,300-12,900 cal BP, are relatively common and have been found throughout the state, but almost exclusively as isolates. Early Holocene sites are abundant as well, particularly on the coast where at least 23 deposits show occupation as old as ca. 10,000-9000-cal BP. Only one of these, Daisy Cave, extends back into the terminal Pleistocene, but the remainder mark occupations that began only at the onset of the Holocene. There are almost no archaeological sites in California that date between 12,900 and 10,300 cal BP or that exhibit superimposed terminal Pleistocene and early Holocene components. This pattern is consistent with a significant disruptive event during the Younger-Dryas.

  14. Characteristics of Southern California coastal aquifer systems

    USGS Publications Warehouse

    Edwards, B.D.; Hanson, R.T.; Reichard, E.G.; Johnson, T.A.

    2009-01-01

    , litany of names for the various formations, lithofacies, and aquifer systems identified within these basins. Despite these nomenclatural problems, available data show that most basins contain similar sequences of deposits and share similar geologic histories dominated by glacio-eustatic sea-level fluctuations, and overprinted by syndepositional and postdepositional tectonic deformation. Impermeable, indurated mid-Tertiary units typically form the base of each siliciclastic groundwater basin. These units are overlain by stacked sequences of Pliocene to Holocene interbedded marine, paralic, fluvial, and alluvial sediment (weakly indurated, folded, and fractured) that commonly contain the historically named "80-foot sand," "200-foot sand," and "400-foot gravel" in the upper part of the section. An unconformity, cut during the latest Pleistocene lowstand (??18O stage 2; ca. 18 ka), forms a major sequence boundary that separates these units from the overlying Holocene fluvial sands and gravels. Unconfined aquifers occur in amalgamated coarse facies near the bounding mountains (forebay area). These units are inferred to become lithologically more complex toward the center of the basins and coast line, where interbedded permeable and low-permeability alluvial, fluvial, paralic, and marine facies contain confined aquifers (pressure area). Coastal bounding faults limit intrabasin and/or interbasin flow in parts of many basins. ?? 2009 Geological Society of America.

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

    PubMed

    Jones, Miriam C; Yu, Zicheng

    2010-04-20

    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.

  16. Large Holocene lakes and climate change in the Chihuahuan Desert

    NASA Astrophysics Data System (ADS)

    Castiglia, Peter J.; Fawcett, Peter J.

    2006-02-01

    Lake-level variations preserved as beach ridges in the Laguna El Fresnal and Laguna Santa María subbasins, northern Mexico, record millennially spaced episodes of increased precipitation during the Holocene epoch. We find that the early, middle, and late Holocene were punctuated by periods wet enough to establish large pluvial lakes in currently dry basins in the Chihuahuan Desert; the largest dated pluvial lake covered ˜5650 km2 during the early Holocene. Constructional beach ridges in these subbasins are 221 ± 33 14C yr B.P. (Little Ice Age equivalent), 3815 ± 52 to 4251 ± 59 14C yr B.P. (early Neoglacial), 6110 ± 80 to 6721 ± 68 14C yr B.P. (mid-Holocene), and 8269 ± 64 to 8456 ± 97 14C yr B.P. (early Holocene), dates that correlate with other millennially spaced wet or cold events in the Northern Hemisphere. We attribute these wet episodes to increased precipitation, cooler temperatures, and reduced evaporation following southward shifts in winter storm tracks, which are related to long-term El Niño Southern Oscillation variability during the Holocene.

  17. Holocene vegetation history from fossil rodent middens near Arequipa, Peru

    USGS Publications Warehouse

    Holmgren, C.A.; Betancourt, J.L.; Rylander, K.A.; Roque, J.; Tovar, O.; Zeballos, H.; Linares, E.; Quade, Jay

    2001-01-01

    Rodent (Abrocoma, Lagidium, Phyllotis) middens collected from 2350 to 2750 m elevation near Arequipa, Peru (16??S), provide an ???9600-yr vegetation history of the northern Atacama Desert, based on identification of >50 species of plant macrofossils. These midden floras show considerable stability throughout the Holocene, with slightly more mesophytic plant assemblages in the middle Holocene. Unlike the southwestern United States, rodent middens of mid-Holocene age are common. In the Arequipa area, the midden record does not reflect any effects of a mid-Holocene mega drought proposed from the extreme lowstand (100 m below modern levels, >6000 to 3500 yr B.P.) of Lake Titicaca, only 200 km east of Arequipa. This is perhaps not surprising, given other evidence for wetter summers on the Pacific slope of the Andes during the middle Holocene as well as the poor correlation of summer rainfall among modern weather stations in the central AndesAtacama Desert. The apparent difference in paleoclimatic reconstructions suggests that it is premature to relate changes observed during the Holocene to changes in El Nin??o Southern Oscillation modes. ?? 2001 University of Washington.

  18. Holocene Glacial Fluctuation Reconstructed From Glacio-marine Sediments at Skallen in the Lüzow-Holm Bay, East Antarctica

    NASA Astrophysics Data System (ADS)

    Maemoku, H.; Miura, H.; Iwasaki, S.; Yokoyama, Y.; Matsuzaki, H.

    2006-12-01

    The history of glacial fluctuation in a fringe of Antarctica since LGM is able to be reconstructed from relative sea level change with raised marine sediments or coastal terraces due to isostatic rebound. In the Terra Nova bay, west Antarctica, ages of abandoned penguin rookeries were concentrated from 5,000 to 4,000 BP and warming event corresponding to that period could be recognized as " Penguin Optimum" (Baroni and Oronbelli, 1994). Concentration of ages of abandoned rookeries in almost same period is also reported in Windmill Islands, east Antarctica (Goodwin, 1993). Miura et al.(2002) revealed that the rate of coastal emergence due to isostatic rebound changed during mid Holocene by observing the stratigraphy of raised beach which had seventeen tidal steps in Lützow-Holm bay, east Antarctica and indicated the occurrence of warming event in mid Holocene. This study aims to reconstruct the history of glacial fluctuation in the east Antarctica since mid Holocene by mapping of glacio-marine sediments and geomorphological evidence of glacial advance or transgressional marine environment. The preliminary results of this study are as follows. 1) We could discriminate two periods of glacial advance since mid Holocene. The present belongs to the last retreat period. The fist period of glacial advance occurred in between 5,000 BP and 3,000 BP. The next one began at least since 1,950 BP and lasted for 200 years. The extent and duration of glacial advance was smaller than the first period. 2) The transitional period from the first glacial advance to the following retreat period possibly accords with the timing of other warming events reported in the antarctic area. We would like to indicate that the period of warming events in Antarctica apparently seems to be consistent with dry and cold period which is usually correlated with with the fluctuation of sunspots number reported in many areas such as Lake Chad (Rognon, 1979) or South Africa (Deacon and Lancaster, 1988

  19. Coastal Hazards: Hurricanes, Tsunamis, Coastal Erosion.

    ERIC Educational Resources Information Center

    Vandas, Steve

    1998-01-01

    Details an ocean-based lesson and provides background information on the designation of 1998 as the "Year of the Ocean" by the United Nations. Contains activities on the poster insert that can help raise student awareness of coastal-zone hazards. (DDR)

  20. Oysters, estuaries, and Late Pleistocene-Holocene sea level, northeastern Gulf of Mexico

    SciTech Connect

    Schroeder, W.W. . Marine Science Program); Shultz, A.W. )

    1993-03-01

    The timing and magnitude of global sea level fluctuations over the past 35 kyr remain nondum ostenduntur after three decades of study. The construction of local relative sea level histories is often complicated by the need to assess regional tectonic and climatic components together. The authors attempt to contribute to an understanding of sea level fluctuations in the northeastern Gulf of Mexico through the application of faunal tracking, using fossil oyster shells as indicators of paleoestuarine environments. They assume that sites on the continental shelf where oysters have been collected were coastal and therefore are reasonable approximations of past shoreline locations and sea-level elevations. They acknowledge that this assumption is a leap of faith for some observers, but is justified as a provisional step toward an independent determination. Insights into Quaternary coastal paleogeography are gathered from locations and radiocarbon ages of American oyster (Crassostrea virginica) shells collected from the Alabama continental shelf. Prior to the onset of the last Wisconsinan glaciation (35 to 26 kyr BP), estuaries occupied a zone 20 to 25 km seaward of today's coastline. As glaciation increased and sea level was lowered (23 to 21 kyr BP), open coastal estuarine conditions developed southward. Oysters dating from the lowstand period (20 to 16 kyr BP) have not been collected. As sea level rose over the next 10 kyr (16 to 6 kyr BP), estuaries were displaced northward in steps. This data on depths and ages can be viewed as supporting an interpretation of fluctuating Holocene sea level, rather than a steady sea-level rise.

  1. Stratigraphic and hydrogeologic framework of the Alabama Coastal Plain

    USGS Publications Warehouse

    Davis, M.E.

    1988-01-01

    Tertiary and Cretaceous sand aquifers of the Southeastern United States Coastal Plain comprise a major multlstate aquifer system informally defined as the Southeastern Coastal Plain aquifer system, which is being studied as part of the U.S. Geological Survey's Regional Aquifer System Analysis (RASA) program. The major objectives of each RASA study are to identify, delineate, and map the distribution of permeable clastlc rock, to examine the pattern of ground-water flow within the regional aquifers, and to develop digital computer simulations to understand the flow system. The Coastal Plain aquifers in Alabama are being studied as a part of this system. This report describes the stratlgraphlc framework of the Cretaceous, Tertiary, and Quaternary Systems in Alabama to aid in delineating aquifers and confining units within the thick sequence of sediments that comprises the Southeastern Coastal Plain aquifer system in the State. Stratigraphlc units of Cretaceous and Tertiary age that make up most of the aquifer system in the Coastal Plain of Alabama consist of clastlc deposits of Early Cretaceous age; the Coker and Gordo Formations of the Tuscaloosa Group, Eutaw Formation, and Selma Group of Late Cretaceous age; and the Midway, Wilcox, and Clalborne Groups of Tertiary age. However, stratigraphlc units of late Eocene to Holocene age partially overlie and are hydraulically connected to clastic deposits in southern Alabama. These upper carbonate and clastlc stratlgraphic units also are part of the adjoining Florldan and Gulf Coastal Lowlands aquifer systems. The Coastal Plain aquifer system is underlain by pre-Cretaceous rocks consisting of low-permeabillty sedimentary rocks of Paleozolc, Triassic, and Jurassic age, and a complex of metamorphic and igneous rocks of Precambrian and Paleozolc age similar to those found near the surface in the Piedmont physiographic province. Twelve hydrogeologlc units in the Alabama Coastal Plain are defined--slx aquifers and six confining

  2. Coastal evolution between two giant rivers: The Chan May embayment in central Vietnam

    NASA Astrophysics Data System (ADS)

    Gouramanis, C.; Switzer, A.; Bristow, C.; Pham, D. T.; Mauz, B.; Pile, J.; Doan, L. D.; Hoang, Q. D.; Ngo, C. K.; Dao, N.; Polivka, P.; Soria, L.; Lee, Y.; Sloss, C.; Hoang, L. V.

    2015-12-01

    The coastal landscapes of Vietnam are dominated in the north and south by the very large Red and Mekong rivers. Central Vietnam, in contrast, has few large rivers that flow to the coastal zone. This coupled with the high relief (>1500 m) of the granitic Truong Son Range and shallow gradient continental shelf, has produced two different coastal geomorphologies. The first is a shallow basin infilled with a sequence of parallel, arcuate beach ridges, and the second includes the development of shore-parallel spits and coastal lagoons. All systems are Holocene in age and we present evidence of the Holocene evolution of the northward-facing, beach ridge strandplain located in the Chan May embayment, approximately 35 km north of Danang. This embayment is relatively small (5 km long at the beach and with a beach ridge sequence that spans 11 km from the modern beach to the base of the Truong Son Range) compared to other beach ridge strandplains to the north and south and serves as an analogue for the evolution of these larger systems. The Holocene evolution of the embayment was resolved using Ground Penetrating Radar (GPR), high-resolution sedimentological analysis and quartz Optically Stimulated Luminescence were used to investigate the internal stratigraphy and chronological development of the beach ridges at Chan May. The strandplain contains uniform, clean quartz-rich sediment interspersed by thin heavy mineral rich bands forming shallow-gradient beach ridges that have steadily prograded seaward during the regression after the mid-Holocene sea level highstand. As the beach ridges prograded seaward, a small river feeding directly from the Truong Son Range meandered across the strandplain and significantly modified the embayment. Recently, the river has become much reduced due to anthropogenic modification of the river and landscape. Prior to the Holocene marine highstand, the area was similarly characterized by a surface of prograding beach ridges that were eroded by

  3. Proxy-Derived Reconstructions of Holocene Paleoclimate for the Hudson Bay Lowlands, an Extensive Peatland in Northern Canada

    NASA Astrophysics Data System (ADS)

    Finkelstein, S. A.; Bunbury, J.; Friel, C.; O'Reilly, B.

    2013-12-01

    The Hudson Bay Lowlands (HBL) is an extensive peatland in northern Canada where an estimated 31 Pg of carbon have accumulated during the Holocene. Given the large size of this carbon pool and the rapid rate of climate warming at high latitudes, quantifying the responses of this peatland to climate change is a critical research priority. Comparing Holocene paleoclimate reconstructions and paleo-vegetation and carbon dynamics in HBL peatlands through analyses of sediment cores is an effective approach to understanding the sensitivity of the carbon pool to climate. Robust paleoclimate reconstructions for the Holocene are needed for such comparisons. Until recently, there have been few paleoclimate reconstructions available for the HBL. Owing to the unique geographic setting of this low lying region to the west of Hudson Bay, reconstructions from adjacent subarctic regions are not directly applicable. We synthesize in this paper a series of paleoenvironmental records derived from biological proxies preserved in lake and wetland sediment cores collected from within the HBL with the goal of improving available paleoclimate information for the region. Our available pollen records document a series of vegetation changes during the Holocene, beginning with the establishment of coastal or salt marsh communities after emergence of the HBL from the Tyrrell Sea, followed by establishment of vegetation typical of poor fens or bogs. These local vegetation changes are apparently primarily related to hydrological changes driven by isostatic rebound and autogenic processes. Regional assemblages composed of tree pollen, which may be more directly tied to climate, show less variability during the Holocene. Reconstructions using modern analogs suggest minimal variation in temperature during the period of record, although these reconstructions show a moderate increase in precipitation following 3000 yrs BP, corresponding to Neoglacial climates reported at other northern high latitude

  4. Coastal mapping handbook

    USGS Publications Warehouse

    ,; ,; Ellis, Melvin Y.

    1978-01-01

    Passage of the Coastal Zone Management Act of 1972 focused attention on the Nation's coastal land and water areas. As plans for more effective management of the coastal zone evolved, it soon became apparent that improved maps and charts of these areas were needed. This handbook was prepared with the requirements of the entire coastal community in mind, giving greatest attention to the needs of coastal zone managers and planners at the State and local levels. Its principal objective is to provide general information and guidance; it is neither a textbook nor a technical manual, but rather a primer on coastal mapping. This handbook should help planners and managers of coastal programs to determine their mapping requirements, select the best maps and charts for their particular needs, and to deal effectively with personnel who gather data and prepare maps. The sections on "Sources of Assistance and Advice" and "Product and Data Sources" should be especially useful to all involved in mapping the coastal zone. Brief summaries of the mapping efforts of several State coastal zone management programs are included. "Future outlook" discusses anticipated progress and changes in mapping procedures and techniques. Illustrations are inserted, where appropriate, to illustrate the products and equipment discussed. Because of printing restrictions, the colors in map illustrations may vary from those in the original publication. The appendixes include substantial material which also should be of interest. In addition a glossary and an index are included to provide easy and quick access to the terms and concepts used in the text. For those interested in more technical detail than is provided in this handbook, the "Selected references" will be useful. Also, the publications of the professional societies listed in appendix 4 will provide technical information in detail.

  5. Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: implications for the regional sediment budget and long-term shoreline response

    USGS Publications Warehouse

    Denny, Jane F.; Schwab, William C.; Baldwin, Wayne E.; Barnhardt, Walter A.; Gayes, Paul T.; Morton, R.A.; Warner, John C.; Driscoll, Neal W.; Voulgaris, George

    2013-01-01

    High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget. The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain ~67 M m3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component. Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the

  6. Late Holocene Andesitic Eruptions at Mount Rainier

    NASA Astrophysics Data System (ADS)

    Sisson, T. W.; Vallance, J. W.

    2005-12-01

    Holocene Mt. Rainier erupted much more frequently than is recorded by its 11 pumiceous tephras. In the 2.6-2.2 ka Summerland eruptive period, 6 groups of thin (1-5 mm) Sparsely Vesicular Glassy (SVG) ashes were deposited (S1-S6), followed by the 0.3 km3 C-tephra. Two groups of andesitic lava flows and one andesitic block-and-ash flow (2.45 ka) also erupted in the Summerland period (ice conceals any other products). Based on glass composition the pyroclastic flow correlates with S4 ashes that also contain pumiceous grains and rare pumice lapilli. The first of the lava groups, exposed in windows through the Emmons and Winthrop glaciers, is Sr-rich for Mt. Rainier eruptives and correlates with S5 & S6 ashes based on similar high-Sr plagioclase. The ensuing C-tephra formed by plinian eruption of mixed and mingled magma comprising 4 juvenile components: mixed porphyritic andesite pumice, crystal-poor andesite scoria, vesicular high-Sr dacite blebs in pumice and scoria, and poorly inflated crystal-rich high-Sr dacite. High-Sr components were probably entrained conduit linings and segregations from the preceding high-Sr eruptions. The youngest lava group, exposed at the summit, is normal-Sr andesite lacking mixing textures of the C-tephra, and represents eruption of another small batch of andesitic magma perhaps just after the C event. SVG ash grains have blocky-to-fluidal shapes, are rich in plagioclase microlites, and their glasses are high-SiO2 (66-78%) and low-Al2O3 (15-11%). Melting experiments yield apparent equilibration pressures <50MPa for SVG liquids. SVG ashes likely result from shallow hydromagmatic explosions as largely degassed magmas transited the upper-edifice hydrothermal system during effusive eruptions. Rare pumice lapilli codeposited with S1, S2, and S4 ashes have microlite-free dacitic glasses, one with nonreacted hbl phenocrysts. These pumice formed from magmas that ascended rapidly from reservoir depths, synchronous with or closely between effusive

  7. The Holocene Paleolimnology of Lake Superior

    NASA Astrophysics Data System (ADS)

    Hyodo, A.; Longstaffe, F. J.

    2010-12-01

    This study describes contributions of glacial meltwater to Lake Superior over the last 11,000 cal BP. Rhythmites (interpreted as varves), lithological and mineralogical variations, and radiocarbon dating were used to establish chronostratigraphic correlation among four sediment cores from Lake Superior (Duluth, Caribou and Ile Parisienne basins, Thunder Bay Trough). Glacial sediments were deposited between 10,850 and 8,800 cal BP. The oxygen-isotope compositions of ostracodes record the presence of glacial meltwater in ancient Lake Superior as the Laurentide Ice Sheet waxed and waned. Glacial meltwater was increasingly dominant between ~10,850 and ~9,250 cal BP, particularly as thick varves formed in northern portions of the Lake Superior Basin (10,400-10,200, 9,900 and 9,300-9,200 cal BP). Glacial meltwater supply was reduced in the Thunder Bay Trough between 9,250 and 8,950 cal BP, but returned from 8,950 to 8,800 cal BP. Glacial meltwater flow from the Lake Superior Basin probably bypassed the Huron Basin several times during this period. Final termination of glacial meltwater supply occurred at 8,800 cal BP - coincident with cessation of varve formation and inception of ancient Lakes Agassiz-Ojibway and Houghton. Primary productivity was very low and algal growth occurred under conditions of extreme nitrogen deficiency - as determined using TOC, TN and C/N ratios - until glacial meltwater supply to the Basin was ended. The postglacial sediments are non-calcareous. The diatom silica proxy record shows that oxygen-isotope compositions of water rapidly increased after glacial meltwater termination, reaching -10 per mil during the Holocene Thermal Maximum. The oxygen-isotope compositions of water decreased at 3,000 cal BP in response to the Holocene Neoglacial Interval before gradually rising to Lake Superior’s modern value of -8.7 per mil. Aquatic primary productivity, inferred using TOC, TN, and the carbon- and nitrogen isotope compositions, has increased

  8. Postglacial sea-level rise and its impact on the circum-arctic Holocene climate evolution

    NASA Astrophysics Data System (ADS)

    Bauch, Henning; Abramova, Ekaterina; Alenius, Teija; Saarnisto, Matti

    2016-04-01

    The global sea-level rise after the last glaciation not only affected the surface properties (circulation, T-S, sea ice seasonality) of the Arctic Ocean and nearby seas it also had a strong impact on the Holocene development of the shallow North Siberian shelf systems and the environmental evolution of the adjacent hinterland areas. In this region sea level reconstructions indicate the postglacial highstand occurred some time in the middle Holocene, between 6 to 5 ka (Klemann et al., 2015). After that time the sedimentary regime of the shelf seas stabilized as noted in a drastic decrease in sedimentation rates observed in all sediment cores taken from middle to outer shelf water depths of the Laptev Sea (Bauch et al. 2001). But, at water depths lower than 30 meters - i.e., in the inner shelf and nearer to the coasts - sedimentation continued at relatively higher rates, presumably due to input of terrigenous material from river runoff as well as coastal erosion. In relation to the latter process, the huge Lena Delta should comprise a region of sediment catchment where aggradation wins over erosion. However, little is known about the detailed history of this delta during the second half of the Holocene. We therefore have investigated three islands within the Lena Delta. All of these are comprised of massive peat of several meters in thickness. Picking discrete specimens of water mosses (Sphagnum) only, we have carefully dated these peat sections. The depth/age relation of the sampled profiles reflect the growth rate of peat, and thus, the islands. It shows that the islands' history above the present-day delta sea level is about 4000 yrs. old. Moreover, a significant change in peat growth is noted after 2500 yrs BP in both, accumulation and composition, and allows the conclusion of a major shift in Arctic environmental conditions since then. Thus, our results add further information also for other coastal studies, as the ongoing degradation of the rather vulnerable

  9. Bacterial diversity and distribution in the holocene sediments of a northern temperate lake.

    PubMed

    Nelson, David M; Ohene-Adjei, Samuel; Hu, Feng Sheng; Cann, Isaac K O; Mackie, Roderick I

    2007-08-01

    Sediments contain an abundance of microorganisms. However, the diversity and distribution of microorganisms associated with sediments are poorly understood, particularly in lacustrine environments. We used banding patterns from denaturing gradient gel electrophoresis (DGGE) and 16S rDNA sequences to assess the structure of bacterial communities in the Holocene sediments of a meromictic lake in Minnesota. Cluster analysis of the DGGE banding patterns indicates that the early- and middle-Holocene samples group separately from the late-Holocene samples. About 79% of the recovered bacterial sequences cluster with the alpha-, beta-, delta-, epsilon-, and gamma- Proteobacteriaceae and Firmicutes. The remaining approximately 21% lack cultured representatives. The taxonomic lineages of bacteria differ statistically among the early-, middle-, and late-Holocene samples, although the difference is smallest between early- and middle-Holocene samples. Early- and middle-Holocene samples are dominated by epsilon-Proteobacteriaceae, and late-Holocene samples are dominated by sequences from uncultured subphyla. We only recovered delta-Proteobacteriaceae in late-Holocene sediments and alpha- and gamma- Proteobacteriaceae in late- and middle-Holocene sediments. Diversity estimates derived from early-, middle-, and late-Holocene clone libraries indicate that the youngest (late-Holocene) samples had significantly greater bacterial diversity than the oldest (early-Holocene) samples, and the middle-Holocene samples contained intermediate levels of diversity. The observed patterns of diversity may be caused by increased bacterial niche-partitioning in younger sediments that contain a greater abundance of labile organic matter than older sediments.

  10. Holocene Indian Ocean Cosmic Impacts: The Megatsunami Chevron Evidence From Madagascar

    NASA Astrophysics Data System (ADS)

    Masse, W.; Bryant, E.; Gusiakov, V.; Abbott, D.; Rambolamana, G.; Raza, H.; Courty, M.; Breger, D.; Gerard-Little, P.; Burckle, L.

    2006-12-01

    The 2.6 million year Quaternary period terrestrial physical record lacks definitive crater evidence for major regional catastrophic impacts by asteroids and comets other than the 10.5-km diameter Botsumtwi structure in Ghana and the 14.0-km diameter Zhamanshin structure in Kazakhstan [1] dating between about 900 and 1100 kya. Current cosmic impact rate models suggest that an average of between 3-6 globally catastrophic impacts should have occurred on the Earth during the Quaternary, along with several additional significant regional impacts in addition to Zhamanshin and Botsumtwi. These models and data indicate that the great majority of the "missing" major impact locations would likely have occurred in poorly studied oceanic settings. Only recently have Late Quaternary and Holocene period coastal paleo-megatsunami chevron deposits been defined in the Caribbean and along the western coasts of Australia, along with the suggestion that some may have been created by oceanic cosmic impacts in distinction to those caused by landslips, eruptions, and seismic events. We investigate the possibility that many or most megatsunami chevrons occurring along the southern coast of Madagascar were caused by two or more major Holocene Indian Ocean cosmic impacts. This hypothesis is based on an initial study of the worldwide archaeological and anthropological record, and the preliminary study of satellite images of the chevrons, selected Indian Ocean deep-sea cores, sea-floor bathymetry, and physical examination of the Madagascar deposits themselves. Candidate Indian Ocean impact structures are identified and correlated with the southern Madagascar megatsunami chevron deposits. [1] Masse, W.B. 2007 The Archaeology and Anthropology of Quaternary Period Cosmic Impact. In Bobrowsky, P.T. & Rickman, H. (eds.)Comets/Asteroid Impacts and Human Society. Springer, Berlin (in press).

  11. Alaskan transect links Holocene carbon shifts to peatland paleoecology and paleoclimate

    NASA Astrophysics Data System (ADS)

    Peteet, D. M.; Nichols, J. E.; Andreev, A.; McGeachy, A.; Perez, M.

    2011-12-01

    Arctic and subarctic peatlands are highly sensitive to climate shifts, and greenhouse warming is greatest at high latitudes. As high latitudes warm and peatlands provide positive and negative feedbacks in carbon sequestration, the paleo-perspective becomes critical in assessing future peatland stocks. We target a north-south (temperature) and east-west (moisture) transect of Alaskan peatlands using pollen and spores, plant macrofossils, charcoal, stable isotopes, and C/N coupled with carbon to explore the relationship of climate and vegetation shifts to carbon storage through time. Since deglaciation, peatlands have developed in a variety of maritime and continental subarctic and arctic environments with vegetation ranging from fens to bogs. Factors affecting the net carbon storage (productivity and decomposition) include the vegetation type, precipitation, temperature, bryophyte component, seasonality, snow history, fire history, and permafrost. New paleoecological records from three Holocene peatlands, each spanning at least 9000 years, include a continental boreal forest site, Goldmine Bog, Fairbanks, (65°N, 147°W), and maritime sites including Phalarope Bog, Kodiak (57°N, 154°W), and Bear Bog, Cordova (60°N, 145°W). Major shifts in moisture and temperature are evident throughout the Holocene from our multiproxy investigations of each site. Our data address several questions about subarctic/arctic carbon storage and climate, such as whether bogs or fens sequester more carbon, as this topic is intensely debated in the current literature. We also compare shifts in inferred moisture and temperature with carbon storage at each site, and with other coastal and interior sites for a fuller understanding of changes in the climate of this important region.

  12. 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.

  13. Stone tools and foraging in northern Madagascar challenge Holocene extinction models.

    PubMed

    Dewar, Robert E; Radimilahy, Chantal; Wright, Henry T; Jacobs, Zenobia; Kelly, Gwendolyn O; Berna, Francesco

    2013-07-30

    Past research on Madagascar indicates that village communities were established about AD 500 by people of both Indonesian and East African heritage. Evidence of earlier visits is scattered and contentious. Recent archaeological excavations in northern Madagascar provide evidence of occupational sites with microlithic stone technologies related to foraging for forest and coastal resources. A forager occupation of one site dates to earlier than 2000 B.C., doubling the length of Madagascar's known occupational history, and thus the time during which people exploited Madagascar's environments. We detail stratigraphy, chronology, and artifacts from two rock shelters. Ambohiposa near Iharana (Vohémar) on the northeast coast, yielded a stratified assemblage with small flakes, microblades, and retouched crescentic and trapezoidal tools, probably projectile elements, made on cherts and obsidian, some brought more that 200 km. (14)C dates are contemporary with the earliest villages. No food remains are preserved. Lakaton'i Anja near Antsiranana in the north yielded several stratified assemblages. The latest assemblage is well dated to A.D. 1050-1350, by (14)C and optically stimulated luminescence dating and pottery imported from the Near East and China. Below is a series of stratified assemblages similar to Ambohiposa. (14)C and optically stimulated luminescence dates indicate occupation from at least 2000 B.C. Faunal remains indicate a foraging pattern. Our evidence shows that foragers with a microlithic technology were active in Madagascar long before the arrival of farmers and herders and before many Late Holocene faunal extinctions. The differing effects of historically distinct economies must be identified and understood to reconstruct Holocene histories of human environmental impact.

  14. Stone tools and foraging in northern Madagascar challenge Holocene extinction models

    PubMed Central

    Dewar, Robert E.; Radimilahy, Chantal; Wright, Henry T.; Jacobs, Zenobia; Kelly, Gwendolyn O.; Berna, Francesco

    2013-01-01

    Past research on Madagascar indicates that village communities were established about AD 500 by people of both Indonesian and East African heritage. Evidence of earlier visits is scattered and contentious. Recent archaeological excavations in northern Madagascar provide evidence of occupational sites with microlithic stone technologies related to foraging for forest and coastal resources. A forager occupation of one site dates to earlier than 2000 B.C., doubling the length of Madagascar’s known occupational history, and thus the time during which people exploited Madagascar’s environments. We detail stratigraphy, chronology, and artifacts from two rock shelters. Ambohiposa near Iharana (Vohémar) on the northeast coast, yielded a stratified assemblage with small flakes, microblades, and retouched crescentic and trapezoidal tools, probably projectile elements, made on cherts and obsidian, some brought more that 200 km. 14C dates are contemporary with the earliest villages. No food remains are preserved. Lakaton’i Anja near Antsiranana in the north yielded several stratified assemblages. The latest assemblage is well dated to A.D. 1050–1350, by 14C and optically stimulated luminescence dating and pottery imported from the Near East and China. Below is a series of stratified assemblages similar to Ambohiposa. 14C and optically stimulated luminescence dates indicate occupation from at least 2000 B.C. Faunal remains indicate a foraging pattern. Our evidence shows that foragers with a microlithic technology were active in Madagascar long before the arrival of farmers and herders and before many Late Holocene faunal extinctions. The differing effects of historically distinct economies must be identified and understood to reconstruct Holocene histories of human environmental impact. PMID:23858456

  15. Holocene relative sea levels of Bonaire (Leeward Antilles) - Evidence from circumlittoral sediment traps

    NASA Astrophysics Data System (ADS)

    Engel, Max; May, Simon Matthias; Brückner, Helmut

    2014-05-01

    Relative sea-level (RSL) rise in the near future represents one of the most serious coastal hazards worldwide, in particular in the Caribbean region where it may enhance negative effects from hurricane-induced flooding. RSL is a function of global (glacioeustasy, steric effect), regional (e.g. glacio-isostatic adjustment [GIA], gravitational effects inducing deformation of the earth, upper/lower mantle viscosity, etc.) and local (sediment compaction, tectonic uplift/subsidence) factors. Information on past RSL supports inferences on upper limits of ice shield ablation, estimates of anthropogenic contribution to historical and future RSL rise and calibration of rheological Earth models. We present the first Holocene RSL curve for the island of Bonaire in the southern Caribbean based on 42 14C datings from 20 sediment cores taken from nine different sedimentary archives along the coast. The sedimentary environment of each index point was linked to a palaeo-water depth based on literature and field observations. The index points trace a local RSL history of decelerating rise since 7000-6000 years ago and subsequent asymptotical approximation, similar to RSL curves from adjacent coasts of Curaςao and Venezuela. The results were compared to an existing reference model which considers global effects and regional GIA (including implications for geopotential). Even though the central and northwestern parts of Bonaire experienced slow tectonic uplift of up to 50 cm since the mid-Holocene and correction for compaction was applied, the new RSL curve for Bonaire runs slightly below the reference model which is probably due to sediment compaction in the investigated archives, collapse of cavities in the underlying limestone, or, at Boka Bartol, local-scale normal faulting (c. 1.5 mm/yr).

  16. National Coastal Condition Assessment

    EPA Pesticide Factsheets

    The NCCA is a collaborative, statistical survey of the nation's coastal waters and the Great Lakes. It is one of four national surveys that EPA and its partners conduct to assess the condition and health of the nation's water resources.

  17. 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.

  18. The Holocene environmental history of a small coastal lake on the north-eastern Kamchatka Peninsula

    NASA Astrophysics Data System (ADS)

    Solovieva, N.; Klimaschewski, A.; Self, A. E.; Jones, V. J.; Andrén, E.; Andreev, A. A.; Hammarlund., D.; Lepskaya, E. V.; Nazarova, L.

    2015-11-01

    A radiocarbon and tephra-dated sediment core from Lifebuoy Lake, located on the north-east coast of Kamchatka Peninsula, was analysed for pollen, spores, diatoms, chironomids and tephra in order to uncover regional environmental history. The 6500-year environmental history of Lifebuoy Lake correlates with the broad regional patterns of vegetation development and climate dynamics with both diatoms and chironomids showing near-synchronous changes. Between ca. 6300 and 3900 cal yr BP, the lake ecosystem was naturally enriched, with several Stephanodiscus species dominating the diatom plankton. This natural eutrophication state is likely to be due to a combination of the base-rich catchment geology, the fertilisation effect of several fires in the catchment, silica input from tephra layers and, possibly, nitrogen input from seabirds. The substantial tephra deposit at about 3850 cal yr BP might have stopped sedimentary phosphorus from entering the lake water thus decreasing the trophic state of the lake and facilitating the shift in diatom composition to a benthic Fragiliariaceae complex. Both diatoms and chironomids showed simultaneous compositional changes, which are also reflected by statistically significant changes in their rates of change 300-400 years after the arrival of Pinus pumila in the lake catchment. The rapid increase in both total diatom concentration and the percentage abundance of the large heavy species, Aulacoseira subarctica might be a response to the change in timing and intensity of lake spring turn-over due to the changes in the patterns of North Pacific atmospheric circulation, most notably westward shift of the Aleutian Low. The two highest peaks in A. subarctica abundance at Lifebouy Lake occurred during opposite summer temperature inferences: the earlier peak (3500-2900 cal yr BP) coincided with warm summers and the latter peak (300 cal yr BP-present) occurred during the cold summer period. These imply that A. subarctica shows no direct response to the changes of summer air temperature. Instead, it appears to thrive during the periods of increased winter precipitation, thicker ice and late spring turn-over periods, i.e., shows indirect response to climate. The clearest effect of tephra deposition on the lake ecosystem is above 908 cm (ca. 3800 cal yr BP) where the tephra deposit might have caused the shift from Stephanodiscus-dominated planktonic assemblages to the Fragilariaceae complex of benthic species. Tephra deposits might have also contributed towards the development of eutrophic plankton from about 6300 cal yr BP. It is not certain if several tephra deposits influenced diatom and chironomid changes during the last 300 years.

  19. Maximum-limiting ages of Lake Michigan coastal dunes: Their correlation with Holocene lake level history

    USGS Publications Warehouse

    Arbogast, Alan F.; Loope, Walter L.

    1999-01-01

    At each site, thick deposits of eolian sand overlie late-Pleistocene lacustrine sands. Moderately developed Spodosols (Entic Haplorthods) formed in the uppermost part of the lake sediments are buried by thick dune sand at three sites. At the fourth locality, a similar soil occurs in a very thin (1.3 m) unit of eolian sand buried deep within a dune. These soils indicate long-term (∼ 4,000 years) stability of the lake deposits following subaerial exposure. Radiocarbon dating of charcoal in the buried sola indicates massive dune construction began between 4,900 and 4,500 cal. yr B.P. at the Nordhouse Dunes site, between 4,300 and 3,900 cal. yr B.P. at the Jackson and Nugent Quarries, and between 3,300 to 2,900 cal. yr B.P. at Rosy Mound. Given these ages, it can be concluded that dune building at one site occurred during the Nipissing high stand but that the other dunes developed later. Although lake levels generally fell after the Nipissing, it appears that dune construction may have resulted from small increases in lake level and destabilization of lake-terrace bluffs.

  20. Evidence for latest Pleistocene to Holocene uplift at the southern margin of the Central Anatolian Plateau (CAP), southern Turkey

    NASA Astrophysics Data System (ADS)

    Cosentino, Domenico; Öǧretmen, Nazik; Cipollari, Paola; Gliozzi, Elsa; Radeff, Giuditta; Yıldırım, Cengiz; Baykara, Oruc M.; Shen, Chuan-Chou

    2016-04-01

    Along the Mediterranean coastal area of southern Anatolia, markers of ancient sea-level have been reported west of Alanya and east of the Göksu delta. In both areas, bioconstructed fossil rims, consisting mainly of calcareous algae, are situated 0.5 m above the live counterpart. The fossil rim to the west of Alanya has been dated between 2690 to 1545 yrs BP, evidencing late Holocene rock uplift at the CAP southern margin. More recently, based on beachrocks along the coastal area from Incekum to the south of Adana, authors showed that the shoreline was raised around 0.5 m after 19 BC-200 AD. Based on new field observations along the coast between Aydı ncı k and Ayaş (Mersin, southern Turkey), together with AMS 14C dating and high-resolution U-Th chronology, a more complex uplift history can be suggested. Along the coast of Yeşilovacı k, we observed up to seven uplifted marine notches, from 0.5 m to 6.10 m above sea level. Some of them show relationships with a travertine crust that yielded U-Th ages of 2727 ± 1559 years and 5236 ± 2255 years. In the same area, a calcareous algae fossil trottoir related to a marine notch 5.40 m above sea level yielded an AMS 14C 2σ age of 32700 to 31645 years cal BP. Considering that the global ocean was 60 m below the present sea level at 32 ka, the Yeşilovacı k coastal area has been uplifted at 2 mm/yr. Moving to the east, in a small embayment at Eǧribük, two distinct well cemented beach deposits containing Murex brandaris, Cerithium vulgatum, and Columbella rustica have been uplifted at 0.3 m and 0.7 m above the present sea level. Although it is difficult to reconstruct the paleodepth of those beach deposits, AMS 14C 2σ ages of 5575 to 5445 years cal BP and 2130 to 1965 years cal BP show late Holocene uplift. In the Narlı kuyu area, up to seven different uplifted markers of sea level were observed between 0.8 and 7.2 m above the present sea level. In addition, near Ayaş new insights for late Holocene uplift are

  1. Groundwater quality in the Coastal Los Angeles Basin, California

    USGS Publications Warehouse

    Fram, Miranda S.; Belitz, Kenneth

    2012-01-01

    The Coastal Los Angeles Basin study unit is approximately 860 square miles and consists of the Santa Monica, Hollywood, West Coast, Central, and Orange County Coastal Plain groundwater basins (California Department of Water Resources, 2003). The basins are bounded in part by faults, including the Newport-Inglewood fault zone, and are filled with Holocene-, Pleistocene-, and Pliocene-age marine and alluvial sediments. The Central Basin and Orange County Coastal Plain are divided into a forebay zone on the northeast and a pressure zone in the center and southwest. The forebays consist of unconsolidated coarser sediment, and the pressure zones are characterized by lenses of coarser sediment divided into confined to semi-confined aquifers by lenses of finer sediments. The primary aquifer system in the study unit is defined as those parts of the aquifer system corresponding to the perforated intervals of wells listed in the California Department of Public Health (CDPH) database of public-supply wells. The majority of public-supply wells are drilled to depths of 510 to 1,145 feet, consist of solid casing from the land surface to a depth of about 300 to 510 feet, and are perforated below the solid casing. Water quality in the primary aquifer system may differ from that in the shallower and deeper parts of the aquifer systems.

  2. High Arctic Paraglacial Coastal Evolution in Northern Billefjorden, Svalbard

    NASA Astrophysics Data System (ADS)

    Strzelecki, Matt; Long, Antony; Lloyd, Jerry

    2013-04-01

    Most sediment budget studies in paraglacial, High Arctic, environments have focussed attention on quantifying sediment fluxes in glacial and fluvial catchments. In contrast, little attention has been paid to the functioning of the paraglacial coastal zone with existing models of coastal change based on relict systems developed in mid latitude settings. The pristine coasts of Spitsbergen provided a superb opportunity to quantify how High Arctic coasts are respondingto rapid climate warming and associated paraglacial landscape transformation. In this paper we reconstruct the development of the paraglacial coasts in Petuniabukta and Adolfbukta, the northernmost bays of Billefjorden, central Spitsbergen. The study area is characterized by a sheltered location, a semi-arid, sub-polar climate, limited wave fetch and tidal range, and rapid retreat of all surrounding glaciers. Using a combination of geomorphological, sedimentological, remote sensing and dating methods, we study the processes controlling the coastal zone development over annual, century and millennial timescales. Interannual changes observed between 2008-2010 show that gravel barriers in the study area are resilient to the impacts of local storms and the operation of sea-ice processes. In general, the processes controlling the short-term barrier development often operate in the opposite direction to the landforming patterns visible in the longer-term evolution. Over multi-decadal timescales, since the end of the Little Ice Age. we observe drammatic changes in sediment flux and coastal response under an interval characterised by a warming climate, retreating local ice masses, a shortened winter sea-ice season and melting permafrost. A new approach of dating juvenile mollusc found in uplifted marine barriers led to the better understating of the Late Holocene evolution of a Petuniabukta coastal zone and its reaction to deglaciation, glacioisostatic uplift and sea-level fluctuations. We propose a new

  3. Seawater isotope constraints on tropical hydrology during the Holocene

    NASA Astrophysics Data System (ADS)

    Oppo, Delia W.; Schmidt, Gavin A.; LeGrande, Allegra N.

    2007-07-01

    Paleoceanographic data from the low latitude Pacific Ocean provides evidence of changes in the freshwater budget and redistribution of freshwater within the basin during the Holocene. Reconstructed Holocene seawater δ 18O changes compare favorably to differences predicted between climate simulations for the middle Holocene (MH) and for the pre-Industrial late Holocene (LH). The model simulations demonstrate that changes in the tropical hydrologic cycle affect the relationship between δ 18Osw and surface salinity, and allow, for the first time, quantitative estimates of western Pacific salinity change during the Holocene. The simulations suggest that during the MH, the mean salinity of the Pacific was higher because less water vapor was transported from the Atlantic Ocean and more was transported to the Indian Ocean. The salinity of the western Pacific was enhanced further due both to the greater advection of salt to the region by ocean currents and to an increase in continental precipitation at the expense of maritime precipitation, the latter a consequence of the stronger Asian summer monsoon.

  4. 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.

  5. 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.

  6. Holocene Climate and Catchment-Specific Responses to Climate Change, Recorded in a Transect of Icelandic Lakes

    NASA Astrophysics Data System (ADS)

    Geirsdottir, A.; Axford, Y.; Florian, C. R.; Miller, G. H.; Crump, S. E.; Larsen, D. J.; Olafsdóttir, S.; Thordarson, T.; Blair, C.

    2015-12-01

    Holocene paleoclimate reconstructions from the northern North Atlantic landmasses exhibit greater responses to climate forcings than other Arctic regions presumably tied to changes in North Atlantic ocean-atmosphere circulation. Here we present an overview of high-resolution, precisely dated and PSV synchronized Holocene lake sediment records on Iceland, where we employ diverse proxies at sites spanning a broad modern climate gradient, from the presently glaciated highlands to the coastal lowlands. Despite substantial differences in catchment specific processes that influence each lake record, the multi-proxy reconstructions over the last 10 ka show remarkably consistent trends, especially throughout the mid to late Holocene cooling related to the slow decrease in summer insolation. Of particular note are highly non-linear abrupt departures of centennial scale summer cold periods such as at 5.5 ka, ~4.2 ka; ~3.0 ka, ~1.5 ka, 0.7 ka, and 0.2 ka. Some of the abrupt shifts may be related to Icelandic volcanism influencing catchment stability, but the lack of a full recovery to pre-existing values after the perturbation suggests increased periglacial activity, decreased vegetation cover, and glacier growth in Iceland. That these shifts reflect regional climate changes is also supported by contemporaneous shifts documented elsewhere in the northern North Atlantic region. Although timing and abruptness of these shifts is similar between our Icelandic lake records, their magnitude can differ substantially. Regional-scale factors such as volcanism likely modulate climatic responses to radiative forcing; and at the same time, local watershed characteristics like vegetation cover and soil properties produce site-specific environmental responses to climate change. Our Icelandic lake records provide opportunities to observe the precise timing of local climate shifts and corresponding environmental responses, and thus to disentangle these effects.

  7. The Holocene deglaciation of the Byers Peninsula (Livingston Island, Antarctica) based on the dating of lake sedimentary records

    NASA Astrophysics Data System (ADS)

    Oliva, M.; Antoniades, D.; Giralt, S.; Granados, I.; Pla-Rabes, S.; Toro, M.; Liu, E. J.; Sanjurjo, J.; Vieira, G.

    2016-05-01

    The process of deglaciation in the Antarctic Peninsula region has large implications for the geomorphological and ecological dynamics of the ice-free environments. However, uncertainties still remain regarding the age of deglaciation in many coastal environments, as is the case in the South Shetland Islands. This study focuses on the Byers Peninsula, the largest ice-free area in this archipelago and the one with greatest biodiversity in Antarctica. A complete lacustrine sedimentary sequence was collected from five lakes distributed along a transect from the western coast to the Rotch Dome glacier front: Limnopolar, Chester, Escondido, Cerro Negro and Domo lakes. A multiple dating approach based on 14C, thermoluminescence and tephrochronology was applied to the cores in order to infer the Holocene environmental history and identify the deglaciation chronology in the Byers Peninsula. The onset of the deglaciation started during the Early Holocene in the western fringe of the Byers Peninsula according to the basal dating of Limnopolar Lake (ca. 8.3 cal. ky BP). Glacial retreat gradually exposed the highest parts of the Cerro Negro nunatak in the SE corner of Byers, where Cerro Negro Lake is located; this lake was glacier-free since at least 7.5 ky. During the Mid-Holocene the retreat of the Rotch Dome glacier cleared the central part of the Byers plateau of ice, and Escondido and Chester lakes formed at 6 cal. ky BP and 5.9 ky, respectively. The dating of the basal sediments of Domo Lake suggests that the deglaciation of the current ice-free easternmost part of the Byers Peninsula occurred before 1.8 cal. ky BP.

  8. Indian monsoon variations during three contrasting climatic periods: the Holocene, Heinrich Stadial 2 and the last interglacial-glacial transition

    NASA Astrophysics Data System (ADS)

    Zorzi, Coralie; Fernanda Sanchez Goñi, Maria; Anupama, Krishnamurthy; Prasad, Srinivasan; Hanquiez, Vincent; Johnson, Joel; Giosan, Liviu

    2016-04-01

    In contrast to the East Asian and African monsoons the Indian monsoon is still poorly documented throughout the last climatic cycle (last 135,000 years). Pollen analysis from two marine sediment cores (NGHP-01-16A and NGHP-01-19B) collected from the offshore Godavari and Mahanadi basins, both located in the Core Monsoon Zone (CMZ) reveals changes in Indian summer monsoon variability and intensity during three contrasting climatic periods: the Holocene, the Heinrich Stadial (HS) 2 and the Marine Isotopic Stage (MIS) 5/4 during the ice sheet growth transition. During the first part of the Holocene between 11,300 and 4,200 cal years BP, characterized by high insolation (minimum precession, maximum obliquity), the maximum extension of the coastal forest and mangrove reflects high monsoon rainfall. This climatic regime contrasts with that of the second phase of the Holocene, from 4,200 cal years BP to the present, marked by the development of drier vegetation in a context of low insolation (maximum precession, minimum obliquity). The historical period in India is characterized by an alternation of strong and weak monsoon centennial phases that may reflect the Medieval Climate Anomaly and the Little Ice Age, respectively. During the HS 2, a period of low insolation and extensive iceberg discharge in the North Atlantic Ocean, vegetation was dominated by grassland and dry flora indicating pronounced aridity as the result of a weak Indian summer monsoon. The MIS 5/4 glaciation, also associated with low insolation but moderate freshwater fluxes, was characterized by a weaker reduction of the Indian summer monsoon and a decrease of seasonal contrast as recorded by the expansion of dry vegetation and the development of Artemisia, respectively. Our results support model predictions suggesting that insolation changes control the long term trend of the Indian monsoon precipitation, but its millennial scale variability and intensity are instead modulated by atmospheric

  9. Indian monsoon variations during three contrasting climatic periods: The Holocene, Heinrich Stadial 2 and the last interglacial-glacial transition

    NASA Astrophysics Data System (ADS)

    Zorzi, Coralie; Sanchez Goñi, Maria Fernanda; Anupama, Krishnamurthy; Prasad, Srinivasan; Hanquiez, Vincent; Johnson, Joel; Giosan, Liviu

    2015-10-01

    In contrast to the East Asian and African monsoons the Indian monsoon is still poorly documented throughout the last climatic cycle (last 135,000 years). Pollen analysis from two marine sediment cores (NGHP-01-16A and NGHP-01-19B) collected from the offshore Godavari and Mahanadi basins, both located in the Core Monsoon Zone (CMZ) reveals changes in Indian summer monsoon variability and intensity during three contrasting climatic periods: the Holocene, the Heinrich Stadial (HS) 2 and the Marine Isotopic Stage (MIS) 5/4 during the ice sheet growth transition. During the first part of the Holocene between 11,300 and 4200 cal years BP, characterized by high insolation (minimum precession, maximum obliquity), the maximum extension of the coastal forest and mangrove reflects high monsoon rainfall. This climatic regime contrasts with that of the second phase of the Holocene, from 4200 cal years BP to the present, marked by the development of drier vegetation in a context of low insolation (maximum precession, minimum obliquity). The historical period in India is characterized by an alternation of strong and weak monsoon centennial phases that may reflect the Medieval Climate Anomaly and the Little Ice Age, respectively. During the HS 2, a period of low insolation and extensive iceberg discharge in the North Atlantic Ocean, vegetation was dominated by grassland and dry flora indicating pronounced aridity as the result of a weak Indian summer monsoon. The MIS 5/4 glaciation, also associated with low insolation but moderate freshwater fluxes, was characterized by a weaker reduction of the Indian summer monsoon and a decrease of seasonal contrast as recorded by the expansion of dry vegetation and the development of Artemisia, respectively. Our results support model predictions suggesting that insolation changes control the long term trend of the Indian monsoon precipitation, but its millennial scale variability and intensity are instead modulated by atmospheric

  10. ‘Cape capture’: Geologic data and modeling results suggest the Holocene loss of a Carolina Cape

    USGS Publications Warehouse

    Thieler, E. Robert; Ashton, Andrew D.

    2011-01-01

    For more than a century, the origin and evolution of the set of cuspate forelands known as the Carolina Capes—Hatteras, Lookout, Fear, and Romain—off the eastern coast of the United States have been discussed and debated. The consensus conceptual model is not only that these capes existed through much or all of the Holocene transgression, but also that their number has not changed. Here we describe bathymetric, lithologic, seismic, and chronologic data that suggest another cape may have existed between Capes Hatteras and Lookout during the early to middle Holocene. This cape likely formed at the distal end of the Neuse-Tar-Pamlico fluvial system during the early Holocene transgression, when this portion of the shelf was flooded ca. 9 cal (calibrated) kyr B.P., and was probably abandoned by ca. 4 cal kyr B.P., when the shoreline attained its present general configuration. Previously proposed mechanisms for cape formation suggest that the large-scale, rhythmic pattern of the Carolina Capes arose from a hydrodynamic template or the preexisting geologic framework. Numerical modeling, however, suggests that the number and spacing of capes can be dynamic, and that a coast can self-organize in response to a high-angle-wave instability in shoreline shape. In shoreline evolution model simulations, smaller cuspate forelands are subsumed by larger neighbors over millennial time scales through a process of ‘cape capture.’ The suggested former cape in Raleigh Bay represents the first interpreted geological evidence of dynamic abandonment suggested by the self-organization hypothesis. Cape capture may be a widespread process in coastal environments with large-scale rhythmic shoreline features; its preservation in the sedimentary record will vary according to geologic setting, physical processes, and sea-level history.

  11. Migrating Seals on Shifting Sands: Testing Alternate Hypotheses for Holocene Ecological and Cultural Change on the California Coast

    NASA Astrophysics Data System (ADS)

    Koch, P. L.; Newsome, S. D.; Gifford-Gonzalez, D.

    2001-12-01

    The coast of California presented Holocene humans with a diverse set of ecosystems and geomorphic features, from large islands off a semi-desert mainland in the south, to a mix of sandy and rocky beaches abutting grassland and oak forest in central California, to a rocky coast hugged by dense coniferous forest in the north. Theories explaining trends in human resource use, settlement patterns, and demography are equally diverse, but can be categorized as 1) driven by diffusion of technological innovations from outside the region, 2) driven by population growth leading to more intensive extraction of resources, or 3) driven by climatic factors that affect the resource base. With respect to climatic shifts, attention has focused on a possible regime shift ca. 5500 BP, following peak Holocene warming, and on evidence for massive droughts and a drop in marine productivity ca. 1000 BP. While evidence for a coincidence between climatic, cultural, and ecological change is present, albeit complex, in southern California, similar data are largely lacking from central and northern California. We are using isotopic and archaeofaunal analysis to test ideas for ecological and cultural change in central California. Three features of the archaeological record are relevant. First, overall use of marine resources by coastal communities declined after 1000 BP. Second, northern fur seals, which are common in earlier sites, drop in abundance relative to remaining marine animals. We have previously established that Holocene humans in central California were hunting gregariously-breeding northern fur seals from mainland rookeries. These seals breed exclusively on offshore islands today, typically at high latitudes. Their restriction to these isolated sites today may be a response to human overexploitation of their mainland rookeries prehistorically. Finally, collection of oxygen and carbon isotope data from mussels at the archaeological sites, while still in a preliminary phase, has

  12. Late Holocene Hurricane Activity in the Gulf of Mexico from a Bayou Sediment Archive

    NASA Astrophysics Data System (ADS)

    Rodysill, J. R.; Donnelly, J. P.; Toomey, M.; Sullivan, R.; MacDonald, D.; Evans, R. L.; Ashton, A. D.

    2012-12-01

    Hurricanes pose a considerable threat to coastal communities along the Atlantic seaboard and in the Gulf of Mexico. The complex role of ocean and atmospheric dynamics in controlling storm frequency and intensity, and how these relationships could be affected by climate change, remains uncertain. To better predict how storms will impact coastal communities, it is vital to constrain their past behavior, in particular how storm frequency and intensity and the pattern of storm tracks have been influenced by past climate conditions. In an effort to characterize past storm behavior, our work contributes to the growing network of storm records along the Atlantic and Gulf coasts by reconstructing storm-induced deposits in the northern Gulf of Mexico during the Late Holocene. Previous work on the northern Gulf coast has shown considerable centennial-scale variability in the occurrence of intense hurricanes, much like the northern Atlantic coast and in the Caribbean Sea. The timing of active and quiet intervals during the last 1000 years amongst the Gulf Coast records appears to be anti-phased with stormy intervals along the North American east coast. The sparse spatial coverage of the existing intense hurricane reconstructions provides a limited view of the natural variability of intense hurricanes. A new, high resolution reconstruction of storms along the northern Gulf Coast would be beneficial in assembling the picture of the patterns of storminess during the Late Holocene. Our study site, Basin Bayou, is situated on the north side of Choctawhatchee Bay in northwest Florida. From 1851 to 2011, 68 storms have struck the coast within 75 miles of Basin Bayou, of which 10 were Category 3 or greater, making it a prime location to reconstruct intense hurricanes. Basin Bayou openly exchanges water with Choctawhatchee Bay through a narrow channel, which acts as a conduit for propagating storm surges, and potentially coarse-grained bay sediments, into the bayou. Our record is

  13. Mid-Holocene environmental changes in the Bay of Skaill, Mainland Orkney, Scotland: an integrated geomorphological, sedimentological and stratigraphical study

    NASA Astrophysics Data System (ADS)

    de La Vega Leinert, Anne C.; Keen, David H.; Jones, Robert L.; Wells, James M.; Smith, David E.

    2000-07-01

    A detailed multidisciplinary investigation of intertidal freshwater sediments exposed in the north of the Bay of Skaill, Mainland Orkney, Scotland, have revealed a complex sedimentary sequence. This provided evidence for dynamic coastal environmental changes in the area since the mid-Holocene. Freshwater ponds developed on glacial sediments ca. 6550 +/- 80 yr BP (cal. bc 5590-5305). From ca. 6120 +/- 70 yr BP (cal. bc 5040-4855), these were infilled by blown sand from the distal edge of a dune ridge located to the west. Thereafter, a series of sand-blow events alternating with periods of quiescence occurred until ca. 4410 +/- 60 yr BP (cal. bc 3325-2900). Between ca. 5240 +/- 160 and 4660 +/- 80 yr BP (cal. bc 4370-3115), pollen and charcoal records show evidence of anthropogenic activities, associated with the nearby Neolithic settlement of Skara Brae. Agriculture was probably affected by recurrent sand movement and widespread deposition of calcium carbonate in the hinterland of the bay. Machair development between ca. 6100 and 5000 yr BP (cal. bc 5235-3540) corresponds to a mid-Holocene phase of dune formation recorded elsewhere in northwest Europe. The more recent and progressive formation of the bay has probably been related to increasing external forcing via storminess, long-term relative sea-level change and sediment starvation within this exposed environment.

  14. Seasonal deposition of Holocene banded sediments in the Severn Estuary Levels (southwest Britain): palynological and sedimentological evidence

    NASA Astrophysics Data System (ADS)

    Dark, Petra; Allen, J. R. L.

    2005-01-01

    Banded sediments outcrop widely in the intertidal zone of the Severn Estuary and have been suggested, on the basis of textural analysis, to have formed in response to seasonal variations in sea temperature and windiness (Holocene, 14 (2004) 536). Here palynological and sedimentological analyses of banded sediments of mid-Holocene date from Gold Cliff, on the Welsh side of the Severn Estuary, are combined to test and further develop the hypothesis of seasonal deposition. Pollen percentage and concentration data are presented from a short sequence of bands to establish whether textural variations in the bands coincide with variations in pollen content reflecting seasonal flowering patterns. It is shown that fine-grained band parts contain higher total pollen concentrations, and a higher proportion of pollen from late spring- to summer-flowering plants, than coarse-grained band parts. Pollen in the coarser deposits appears primarily to reflect deposition from the buffering 'reservoir' of suspended pollen in the estuarine water-body and from rivers, when there is little pollen in the air in winter, while the finer sediments contain pollen deposited from the atmosphere during the flowering season, superimposed on these 'background' sources. The potential of such deposits for refining chronologies and identifying seasonality of coastal processes is noted, and the results of charcoal particle analysis of the bands presented as an example of how they have the potential to shed light on seasonal and annual patterns of human activity.

  15. Sedimentary archives of the French Atlantic coast (inner Bay of Vilaine, south Brittany): Depositional history and late Holocene climatic and environmental signals

    NASA Astrophysics Data System (ADS)

    Sorrel, Philippe; Tessier, Bernadette; Demory, François; Baltzer, Agnès; Bouaouina, Firas; Proust, Jean-Noël; Menier, David; Traini, Camille

    2010-06-01

    The late Holocene is of particular interest to our understanding of the evolution of coastal sedimentary systems because this period encompasses warmer and cooler periods, and rising sea level in northern Europe. Based on an approach combining AMS 14C, sedimentological and rock magnetic analyses on sediment cores complemented with seismic data collected in the macrotidal Bay of Vilaine (south Brittany), we document the depositional history of the inner bay coeval to the mid- to late-Holocene transgression in south Brittany. Correlation between sedimentary archives revealed the main sedimentary infilling phases during the last 6000 years. Four units (U1-U4) are recognized in the coastal sediment wedge of the system, corresponding to the stepwise marine invasion of the bay. We show that (1) marine inundation, due to the steep morphology of the bedrock, is diachronous between distal and proximal records. A time lag of ˜1000 years is inferred over a distance of less than 5 km; (2) in the outer areas, the sedimentation has been condensed since 3000 years; (3) proximal estuarine archives offer the best record of sedimentary processes covering the last 2000 years, including the Medieval Warm Period (MWP). Correlations in proximal records in the Bay of Vilaine assess the connection between coastal sedimentary dynamics, climatic conditions and anthropogenic activities during the MWP. We match the preservation of clay deposits to increased river-borne suspended matter transported to the estuary probably as a result of accelerated land-use development (higher soil erosion) in the catchment area between ca. 880 and 1050 AD. Because the preservation of estuarine sedimentary successions is favoured when coastal wave sediment reworking is minimal, it is proposed that the prevailing climatic regime in south Brittany during the MWP likely resembled to that of the preferred negative phase of the North Atlantic Oscillation (NAO). Our data are fairly consistent with other late

  16. Lateglacial-Holocene Environment History, Kazakhstan

    NASA Astrophysics Data System (ADS)

    Kremenetski, K.; Velichko, A.

    2007-12-01

    Kazakhstan is located in central Asia between Caspian Sea and Tiang-Shang Mountains. Few well dated holocene sequences from the forest-steppe and steppe belt of Kazakhstan provided information about the vegetation and climate history. Mokhovoe mire was studied in the watershed of Tobol and Ubagan rivers. That's the most thick peat mire in northern Kazakhstan. Sedimentation in the Mokhovoe sequence started ca. 7800 BP. At that time regional vegetation was represented by steppes and birch-poplar forests. Pine penetrated in the Tobol region likely between 6500 and 6000 BP. Pine grew on sand terraces of Tobol River together with birch. At 3000-2900 BP Tilia, Quercus, Ulmus grew in north-west Kazakhstan.The general structure of vegetation was the same as at 6500-6000 BP. At 1900-1500 BP climate became less continental and pine forests with pure pine canopy expanded on sandy terraces of Tobol and Ubagan rivers. Soon after 1500 BP broad-leaved trees were extinct from the regional forests. Pashennoe lake is located in Karkaralinsk mountains in the most elevated part in the south-east part of the Kazakhstan lowhills. Dry grass-wormwood and wormwood steppes were spread in the region at 10500-8200 BP. Picea obovata and Hippophäe rhamnoides occurred in protected parts in intermountain valleys of Karkaralinsk mountains. Salix and Betula also occurred in valleys. Between 8000 and 6000 BP forest vegetation in Karkaralinsk mountains was represented by birch forests. Pine penetrated to Karkaralinsk mountains between 6000 and 5500 BP, but it didn't formed large forests. At the same time the maximal spread of Alnus glutinosa was reconstructed. The general structure of regional vegetation was stable up to. At 1500 BP pure pine forests expanded over Karkaralinsk mountains and around Pashennoe lake. Few lakes were investigated in Borovoe mountains in south of Kokchetav region of Kazakhstan. In early Holocene birch forests dominated in regional vegetation. Pine expanded in Borovoe at ca

  17. Upper Ocean Variability in the Indo-Pacific Warm Pool during the Late Holocene, Early Holocene and Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Xu, J.; Kuhnt, W.; Holbourn, A. E.; Andersen, N.

    2009-12-01

    We analyzed oxygen isotopes and Mg/Ca ratios in the surface dwelling planktonic foraminifer Globigerinoides ruber (white s.s.) and the thermocline dweller Pulleniatina obliquiloculata to improve understanding of upper ocean spatial variability in the Indo-Pacific Warm Pool (IPWP). We focused on three critical time intervals: the Last Glacial Maximum (LGM; 18-21.5 ka), the early Holocene (8-9 ka) and the late Holocene (0-2 ka). Our records from twenty-four stations in the South China Sea, Timor Sea, Indonesian seas and western Pacific indicate overall dry and cool conditions in the IPWP during the LGM with a low thermal gradient between surface and thermocline waters. Warm surface waters (>28 Celsius degree) spread over the entire region during the early Holocene, indicating substantial expansion of the IPWP. However in the eastern Indian Ocean (Timor Sea), the thermocline gradually shoaled from the LGM to early Holocene, reflecting intensification of the subsurface Indonesian Throughflow. Increased precipitation over the South China Sea appears related to an intensified summer monsoon and northward displacement of the Intertropical Convergence Zone. Increased freshwater export from the South China Sea through the Java Sea also contributed to a change in the vertical structure of the Indonesian Throughflow from surface- to thermocline-dominated flow and a freshening of Timor Sea waters during the early Holocene.

  18. Impact of Holocene climate variability on Arctic vegetation

    NASA Astrophysics Data System (ADS)

    Gajewski, K.

    2015-10-01

    This paper summarizes current knowledge about the postglacial history of the vegetation of the Canadian Arctic Archipelago (CAA) and Greenland. Available pollen data were used to understand the initial migration of taxa across the Arctic, how the plant biodiversity responded to Holocene climate variability, and how past climate variability affected primary production of the vegetation. Current evidence suggests that most of the flora arrived in the area during the Holocene from Europe or refugia south or west of the region immediately after local deglaciation, indicating rapid dispersal of propagules to the region from distant sources. There is some evidence of shrub species arriving later in Greenland, but it is not clear if this is dispersal limited or a response to past climates. Subsequent climate variability had little effect on biodiversity across the CAA, with some evidence of local extinctions in areas of Greenland in the late Holocene. The most significant impact of climate changes is on vegetation density and/or plant production.

  19. Synchronous interhemispheric Holocene climate trends in the tropical Andes.

    PubMed

    Polissar, Pratigya J; Abbott, Mark B; Wolfe, Alexander P; Vuille, Mathias; Bezada, Maximiliano

    2013-09-03

    Holocene variations of tropical moisture balance have been ascribed to orbitally forced changes in solar insolation. If this model is correct, millennial-scale climate evolution should be antiphased between the northern and southern hemispheres, producing humid intervals in one hemisphere matched to aridity in the other. Here we show that Holocene climate trends were largely synchronous and in the same direction in the northern and southern hemisphere outer-tropical Andes, providing little support for the dominant role of insolation forcing in these regions. Today, sea-surface temperatures in the equatorial Pacific Ocean modulate rainfall variability in the outer tropical Andes of both hemispheres, and we suggest that this mechanism was pervasive throughout the Holocene. Our findings imply that oceanic forcing plays a larger role in regional South American climate than previously suspected, and that Pacific sea-surface temperatures have the capacity to induce abrupt and sustained shifts in Andean climate.

  20. Synchronous interhemispheric Holocene climate trends in the tropical Andes

    PubMed Central

    Polissar, Pratigya J.; Abbott, Mark B.; Wolfe, Alexander P.; Vuille, Mathias; Bezada, Maximiliano

    2013-01-01

    Holocene variations of tropical moisture balance have been ascribed to orbitally forced changes in solar insolation. If this model is correct, millennial-scale climate evolution should be antiphased between the northern and southern hemispheres, producing humid intervals in one hemisphere matched to aridity in the other. Here we show that Holocene climate trends were largely synchronous and in the same direction in the northern and southern hemisphere outer-tropical Andes, providing little support for the dominant role of insolation forcing in these regions. Today, sea-surface temperatures in the equatorial Pacific Ocean modulate rainfall variability in the outer tropical Andes of both hemispheres, and we suggest that this mechanism was pervasive throughout the Holocene. Our findings imply that oceanic forcing plays a larger role in regional South American climate than previously suspected, and that Pacific sea-surface temperatures have the capacity to induce abrupt and sustained shifts in Andean climate. PMID:23959896

  1. Holocene evolution of Apalachicola Bay, Florida

    USGS Publications Warehouse

    Osterman, L.E.; Twichell, D.C.; Poore, R.Z.

    2009-01-01

    A program of geophysical mapping and vibracoring was conducted to better understand the geologic evolution of Apalachicola Bay. Analyses of the geophysical data and sediment cores along with age control provided by 34 AMS 14C dates on marine shells and wood reveal the following history. As sea level rose in the early Holocene, fluvial deposits filled the Apalachicola River paleochannel, which extended southward under the central part of the bay and seaward across the continental shelf. Sediments to either side of the paleochannel contain abundant wood fragments, with dates documenting that those areas were forested at 8,000 14C years b.p. As sea level continued to rise, spits formed of headland prodelta deposits. Between ???6,400 and ???2,500 14C years b.p., an Apalachicola prodelta prograded and receded several times across the inner shelf that underlies the western part of the bay. An eastern deltaic lobe was active for a shorter time, between ???5,800 and 5,100 14C years b.p. Estuarine benthic foraminiferal assemblages occurred in the western bay as early as 6,400 14C years b.p., and indicate that there was some physical barrier to open-ocean circulation and shelf species established by that time. It is considered that shoals formed in the region of the present barrier islands as the rising sea flooded an interstream divide. Estuarine conditions were established very early in the post-glacial flooding of the bay. ?? 2009 US Government.

  2. Reef-sourced slope deposits, Holocene, Bahamas

    SciTech Connect

    Ginsburg, R.N.; Eberli, G.P.; Harris, P.M.; Slater, R.; Swart, P.K.

    1987-05-01

    Observations and sampling to 350 m from a two-person submersible off Chub Cay, Berry Island, Bahamas, support the idea that the Holocene deep reef is a principal source of talus, now cemented, that foots the windward margins of Great Bahama Bank. At the Chub Cay dive site, a wall extends from 30 to 170 m subsea; below is a low-relief fore reef slope, ca. 50/sup 0/, of limestone veneered with sediment. The upper wall from 30 to 80 m, the deep reef, has a luxuriant growth of corals and a profusion of the calcareous alga halimeda spp. Below 50 m, living coral decreases, and from 80 to 170 m the wall is highly irregular with discontinuous ledges and blind-end caves. At depths from 150 to 170 m, the wall gives way to the fore reef slope whose relative smooth surface dips at 50/sup 0/ to 60/sup 0/ and extends to 350 m. The fore reef is limestone, but its topography resembles that of alluvial fans; rounded ridges rise a few meters above the intervening valleys that are tens of meters wide. The limestone surface has a discontinuous veneer of fine sediment and algal plates, and locally loose cobble and boulder-sized blocks of limestone. A sample of the limestone slope is of well-cemented coral clasts and skeletal sediment. They infer that the deep reef grows outward so rapidly that it caves periodically. The resulting debris bypasses the wall, but some is perched on the steep fore reef slope below where it is soon incorporated into the slope by submarine cementation.

  3. Late-Holocene vegetation and climate change in Jeju Island, Korea and its implications for ENSO influences

    NASA Astrophysics Data System (ADS)

    Park, Jungjae; Shin, Young Ho; Byrne, Roger

    2016-12-01

    Several recent studies suggest the hypothesis that the El Niño-Southern Oscillation (ENSO) is an important factor controlling the Holocene East Asian Monsoon (EAM). However, the mechanism underlying this influence remains unclear due to the lack of high-resolution paleoclimate records from the coast of East Asia. Here, we provide a new record of late Holocene climate change in coastal East Asia based on multi-proxy evidence (pollen, organic content, magnetic susceptibility, grain size) obtained from a sediment core from Jeju Island, South Korea. As Jeju Island is strongly influenced by the Kuroshio flow, our sediment proxy records contain ENSO signals from the tropical Pacific. The study area was affected by dry/cool conditions in the western tropical Pacific (WTP) between 4350 and 1920 cal yr BP when El Niños were frequent, and by rapid warming/wetting and forestation since 1920 cal yr BP when La Niñas were more common. Jeju Island was relatively dry/cool between 2100 and 1600, 1300-1200, 1100-1000, 800-650, and 300-50 cal yr BP, as opposed to the Galápagos Islands, which were relatively wet/warm, reflecting the ENSO-related negative correlation between eastern and western margins of Pacific. Wet conditions may have prevailed during the early Little Ice Age (LIA) (620-280 cal yr BP) despite consistent cooling. This period of high precipitation may have been associated with the increased landfall of typhoons and with warmer Kuroshio currents under La Niña-like conditions. According to our results, EAM on the East Asian coastal margin was predominantly driven by ENSO activity, rather than by the precession effect. Paleoclimatic data from Jeju Island, with its insular position and closeness to warm Kuroshio currents, provide clear evidence of these ENSO influences.

  4. Time-stratigraphic aspects of a formation: Interpretation of surficial Pleistocene deposits by analogy with Holocene paralic deposits, southeastern Delaware

    NASA Astrophysics Data System (ADS)

    Demarest, J. M.; Biggs, R. B.; Kraft, J. C.

    1981-08-01

    Pleistocene shoreline deposits in close spatial and temporal proximity to Holocene deposits permit detailed interpretation of the development of Pleistocene coastal deposits when a modern-ancient analog approach is used. Peak sea levels during the past 1 m.y. or more have allowed the preservation of transgressive shoreline systems, here referred to as paralic units, along the inner continental margin. These Pleistocene paralic units are similar to Holocene coastal deposits now forming on Delmarva Peninsula. The Omar Formation (early to late Pleistocene age) incorporates at least four juxtaposed, transgressive, paralic units of different ages, each containing deposits of lagoonal sands and muds, tidal marsh, barrier sands and gravels, tidal delta sands and silty sands, and tidal channel sands and gravels. The successive paralic units become younger in the seaward direction. Thus, although the Omar Formation in the study area is almost entirely made up of transgressive deposits produced during rising sea levels, in a longer time frame it forms a progradational sequence. Only about 2% to 5% of the elapsed time during the deposition of the studied part of the Omar Formation is represented by sedimentary units. The internal time-stratigraphy of the Omar Formation is extremely complex. This makes the time-stratigraphic interpretation of any one outcrop or drill hole difficult. Any lithologic change may represent a wide variety of time gaps, from minutes to tens of thousands of years. The analog approach, in which sedimentary lithosome mapping is used, allows one to infer a time-stratigraphic framework of the deposits. These concepts can aid in the interpretation of depositional history of older paralic deposits and the nature of the development of certain types of clastic formations.

  5. Louisiana coastal ecosystem

    USGS Publications Warehouse

    ,

    2000-01-01

    Louisiana's coast and its degradation and restoration are major environmental issues being studied at the National Wetlands Research Center. Coastal ecosystems are vulnerable because of the tremendous amount of human activity that takes place along the coast. Information on ecological processes is essential to guide the development along the coast as well as to protect and restore wildlife habitat.Louisiana has about 40% of coastal wetlands in the lower 48 states; they support fish, waterfowl, and fur-bearing animals as well as unique cultures like that of the Acadians. The fish and wildlife resources of Louisiana's coast produce over $1 billion each year in revenues.But Louisiana has the highest coastal loss rate because of natural and human causes. Over the past three decades, Louisiana has lost as much as 35-40 mi2 (90-104 km2) of coastal wetlands a year.The National Wetlands Research Center is qualified to assess and monitor this ecosystem because of its proximity to the study area, a staff chosen for their expertise in the system, and a number of established partnerships with others who study the areas. The Center is often the lead group in partnerships with universities, other federal agencies, and private entities who study this ecosystem.Most of the Center's research and technology development performed for coastal wetlands are done at the Lafayette headquarters; some work is performed at the National Wetlands Research Center's project office in Baton Rouge, LA.

  6. Holocene Millennial-Scale Climate Variability in Western North America

    NASA Astrophysics Data System (ADS)

    Fawcett, P. J.; Castiglia, P. J.; Meyer, G. A.; Armour, J.

    2002-12-01

    We compare several high-resolution paleoclimatic records from western North America that indicate near-synchronous millennial-scale climate variability through much of the Holocene. A Holocene pluvial lake system in northern Chihuahua, Mexico alternates between lake highstands representing cooler and wetter conditions and dry playa conditions representing warmer, drier climates. Alpine lakes and bogs from the Sangre de Cristo Mountains of northern New Mexico record a series of glacial and periglacial events (colder, effectively wetter climates) that alternate with warmer, drier climates over the late Pleistocene and the Holocene. Forest fire-related sedimentation and alluvial activity from northeast Yellowstone National Park also shows a clear response to millennial-scale climate change during the Holocene. Pulses of fire-related debris flow activity occur during warmer, drier periods that are more prone to droughts. These alternate with cooler, effectively wetter conditions that produce more river discharge and form broad flood plains later preserved as terraces. Pluvial lake highstands in northern Mexico are centered at the following calendar ages: 230 yr B.P., 4.2 ka, 7.4 ka, and 9.3 ka. The northern New Mexico chronology shows cold, effectively wetter climates at the following calendar age midpoints: 200 yr B.P., 3.0 ka, 3.9 ka and 5.7 ka. The Yellowstone chronology shows cold, effectively wetter climates during the following age ranges: 300 to 600 yr B.P., 1.4 to 1.6 ka, 2.8 to 3.1 ka, 3.9 to 4.3 ka, and 5.5 to 6.0 ka. In the Rocky Mountain records, the millennial-scale events are more prominent during the late Holocene Neoglacial interval than during the early to middle Holocene. These climate events in western North America reflect widespread temperature anomalies and to a lesser extent, precipitation anomalies. The cold phases of these events correlate with a North Atlantic record of ice-rafting and cool events (Bond et al., 2001) and suggest that

  7. Holocene sand shoals offshore of Mississippi River delta plain, Louisiana

    SciTech Connect

    Penland, S.; McBride, R.A. ); Suter, J.R. ); Williams, S.J. ); Kindinger, J.L. ); Boyd, R. )

    1989-09-01

    Offshore of the Mississippi River delta plain lies a series of Holocene sand shoals marking the position of ancient submerged shorelines. These ancient shorelines represent stillstand positions during which the Holocene transgression drove sea level across the former lowstand subaerial erosion surface of the Mississippi River delta plain. Short periods of rapid sea level rise led to the transgressive submergence of these sandy shorelines. Two shoreline trends can be recognized at the {minus}10-m and {minus}20-m isobaths on the continental shelf.

  8. Zoonotic parasites associated with felines from the Patagonian Holocene.

    PubMed

    Fugassa, Martín Horacio; Beltrame, María Ornela; Bayer, María S; Sardella, Norma Haydée

    2009-12-01

    Feline coprolites were examined for parasites with the aim of studying ancient infections that occurred in the Patagonian region during the Holocene period. Eggs compatible to Trichuris sp., Calodium sp., Eucoleus sp., Nematodirus sp., Oesophagostomum sp. (Nematoda), Monoecocestus sp. (Cestoda) and Eimeria macusaniensis (Coccidia) were recovered from faecal samples. The results obtained from the analysis provide evidence of consumption by felids of the viscera of both rodents and camelids. This knowledge allows for improved explanations as to the distribution of parasitism and its significance to the health of humans and animals inhabiting the area under study during the Middle Holocene.

  9. 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.

  10. The Holocene perspective of Northern Hemisphere temperature evolution

    NASA Astrophysics Data System (ADS)

    Lohmann, G.; Laepple, T.

    2009-04-01

    The average surface air temperature of the globe has increased by about 0.5°C since the middle of the nineteenth century. Regarding the climate changes observed during the 20th century, it is of particular importance to identify and quantify the environmental changes to put the recent warming in relationship with the natural climate variations at different timescales. Considering the relatively short period of the available instrumental data, the use of paleoclimate records in combination with model simulations proves to be very useful for the estimation of past climate variability. Here we analyse the Holocene temperature evolution of the past 6000 years as well as the recent and projected future climate evolution. For our analysis, we use the output of an ensemble of general circulation models for the mid-Holocene (PMIP II project) and for recent and projected future (CMIP 3 project), complemented by transient simulations over the mid-to-late Holocene. The model data are also compared to observations and proxy data. The general structure of the Northern Hemisphere appears to have a "Hockey Stick" shape: The Northern Hemisphere cooling during the mid-to-late Holocene (neoglaciation) has been partly compensated during the past century. The reason for the Holocene trend lies in the astronomical forcing in conjunction with climate feedbacks whereas the recent and projected future warming trend can be attributed to anthropogenic influence on greenhouse gas concentrations in the atmosphere plus climate feedbacks. It is important to detect regional differences: At low latitudes and over large parts of the open ocean, the present climate is already warmer than that of the mid-Holocene during boreal summer, whereas at mid and high latitudes (especially over land and parts of the Arctic Ocean) the mid-Holocene values will be reached within the next 20-80 years. Seasonality and regional circulation and temperature anomalies are discussed. It is argued that the Holocene

  11. 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

  12. The groundwater exchange rate of the southern Baltic coastal lowland

    NASA Astrophysics Data System (ADS)

    Burzyński, K.; Sadurski, A.

    1990-11-01

    The groundwater of the southern Baltic lowlands usually occurs in particular hydrogeological conditions. The lowland is mostly covered by peats several metres in thickness. Peatbog water is isolated from deeper aquifers and has different chemical composition. Salty, relic groundwater of marine origin from the Atlantic period of the Holocene (Littorina transgression) may have survived in the deeper coastal aquifers in places of sluggish flow. The results of mathematical modelling of groundwater circulation show that the flow rate and local directions of groundwater change during the year, depending on the rate of groundwater recharge by precipitation. We present here an unsteady flow model, which makes it possible to predict the water table fluctuations during a year at any point of the area studied. The calculation of the groundwater exchange rate did not confirm the presence of any places of very sluggish groundwater flow, where salty, young relic water might have survived.

  13. Post-glacial Sediment Load and Subsidence in Coastal Louisiana

    NASA Technical Reports Server (NTRS)

    Ivins, Erik R.; Dokka, Roy K.; Blom, Ronald G.

    2007-01-01

    Sea level rise in the Gulf of Mexico has occurred at a rate of 1.8-2.2 mm/yr during the 20th century, or nearly the same as observed globally due to combined steric and water mass changes. Tide gauges in coastal Louisiana, however, record a substantially larger rate of rise and while a number of causal mechanisms may be responsible, their specific contribution is poorly understood. Using a realistic viscoelastic Earth model, detailed geologic parameters for south Louisiana and new GPS data, we demonstrate that Holocene sedimentary loading in the Gulf and Mississippi River delta is capable of contributing to 1-8 mm/yr of subsidence over areas of 30-0.75 x 10(exp 3) km(exp 2).

  14. 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

  15. Coastal Processes with Engineering Applications

    NASA Astrophysics Data System (ADS)

    Dean, Robert G.; Dalrymple, Robert A.

    2004-03-01

    The world's coastlines, dividing land from sea, are geological environments that are unique in their composition and the physical processes affecting them. At the dynamically active intersection of land and the oceans, humans have been building structures throughout history. Initially used for naval and commercial purposes, more recently recreation and tourism have increased activity in the coastal zone dramatically. Shoreline development is now causing a significant conflict with natural coastal processes. This text on coastal engineering will help the reader understand these coastal processes and develop strategies to cope effectively with shoreline erosion. The book is organized in four parts: (1) an overview of coastal engineering, using case studies to illustrate problems; (2) hydrodynamics of the coastal zone, reviewing storm surges, water waves, and low frequency motions within the nearshore and surf zone; (3) coastal responses including equilibrium beach profiles and sediment transport; (4) applications such as erosion mitigation, beach nourishment, coastal armoring, tidal inlets, and shoreline management.

  16. NATIONAL COASTAL CONDITION REPORT II

    EPA Science Inventory

    Coastal waters in the US include estuaries, coastalwetlands, coral reefs, mangrove and kep forests, seagrass meadows, and upwelling areas. Critical coastal habitats provide spawning grounds, nurseries, shelter, and food for finfish, shellfish, birds, and other wildlife. the nat...

  17. Arctic Coastal Erosion Modeling

    NASA Astrophysics Data System (ADS)

    Ravens, T. M.; Jones, B.; Zhang, J.; Tweedie, C. E.; Erikson, L. H.; Gibbs, A.; Richmond, B. M.

    2011-12-01

    A process-based coastal erosion/shoreline change model has been developed for Arctic coastal bluffs subject to niche erosion/block collapse. The model explicitly accounts for many environmental/geographic variables including: water temperature, water level, wave height, and bluff height. The model was originally developed for a small coastal segment near Drew Point, Beaufort Sea, Alaska. This coastal setting has experienced a dramatic increase in erosion since the early 2000's. The bluffs at this site are 3-4 m tall and consist of ice-wedge bounded blocks of fine-grained sediments cemented by ice-rich permafrost and capped with a thin organic layer. The bluffs are typically fronted by a narrow (~ 5 m wide) beach or none at all. During a storm surge, the sea contacts the base of the bluff and a niche is formed through thermal and mechanical erosion. The niche grows both vertically and laterally and eventually undermines the bluff, leading to block failure or collapse. The fallen block is then eroded both thermally and mechanically by waves and currents, which must occur before a new niche forming episode may begin. The model has been calibrated based on shoreline change data at Drew Point for two time periods: 1979-2002 and 2002-2007. Measured and modeled shoreline change rates were about 8 m/yr and 16 m/yr, for the earlier and later periods, respectively. In this paper, this work is extended to include modeling and measurement of coastal erosion at Drew Point on an annual basis for the period 2007-2010. In addition, the model is applied at three other Arctic coastal locations - Elson Lagoon, Cape Halkett, and Barter Island - where niche erosion/block collapse prevails.

  18. Preliminary geochemical data on shallow marine mollusc from middle Pleistocene-Holocene beach ridges in the gulf of S. Jorge (Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Consoloni, Ilaria; Zanchetta, Giovanni; Aguirre, Marina L.; Baneschi, Ilaria; Boretto, Gabriella M.; Dallai, Luigi; D'Orazio, Massimo; Fallick, Anthony E.; Isola, Ilaria; Pappalardo Adriano Ribolini, Marta

    2010-05-01

    The Patagonia coast comprised between ca 45° S and 43° S preserves a spectacular succession of Quaternary raised beach deposits mostly composed by gravelly beach-ridge successions containing abundant storm accumulations of mollusc remains. Currently, this coastal area is interested by the competing action of the warm Brazilian current from north and the Falkland (Malvinas) current from the south, and roughly it corresponds to the boundary of the Magellanean and Argentinean zooprovinces. Although paleontological studies have been conducted in the recent past (e.g. Aguirre, 2003) there are not practically geochemical studies on these natural archives to infer local paleoceanographic and paleoclimate changes. Preliminary geochemical studies (petrography, stable isotopes, trace elements) on the aragonitic shell Prototaqua antiqua collected in various localities spanning from Holocene to Middle Pleistocene (MIS 9 to MIS 1, e.g. Schellmann and Radke, 2000) successions indicate that this species is relatively well preserved and can be used for the reconstruction of the past coastal oceanographic changes in the area. Aguirre, M.L., 2003. Late Pleistocene and Holocene palaeoenvironments in Golfo San Jorge, Patagonia: molluscan evidence. Marine Geology 194, 3-30. Schellmann, G., Radtke, U., 2000. ESR dating of stratigraphically well-constrained marine terraces along the Patagonian Atlantic coast (Argentina). Quaternary International 68/71, 261-273.

  19. Coastal Inlets Research Program

    DTIC Science & Technology

    2012-01-01

    US Army Corps of Engineers BUILDING STRONG® Julie Dean Rosati Program Manager Jim Walker HQ Navigation Business Line Manager Jeff Lillycrop...0.9 0.1 c VEe= 2,000,000 m3 VCe = 200,000 m3 VFe=200,000 m3 VOe=1,000,000,000 m3 Offshore Ebb Shoal Channel Flood Shoal Bay Deposition...Basin Vce ,VDe,VEe,VFe,Vye ,VOe 0.3 Coastal and Hydraulics Laboratory 4  Conduct R&D to reduce O&M costs at coastal navigation projects  Include

  20. Coastal Inlets Research Program

    DTIC Science & Technology

    2013-03-01

    e N u m b e 50 10 20 30 C u m W C u m u 00 1997 1999 2001 2003 2005 2007 2009 2011 2013** Calendar Year Coastal and Hydraulics Laboratory 4...Flow 14 Verification & Validation Cases Bouss-2D: Advanced phase -resolving wave propagation and t f ti d l Coastal and Hydraulics Laboratory 21 rans...Structures , Noyo Bay, CA Half Moon Bay, CA SWG M t d Shi Ch l TX : a agor a p anne , Galveston Bay, TX Sargent Beach, TX NAE P i t J dith H b RI

  1. Geologic framework of the long bay inner shelf: implications for coastal evolution in South Carolina

    USGS Publications Warehouse

    Barnhardt, W.; Denny, J.; Baldwin, W.; Schwab, W.; Morton, R.; Gayes, P.; Driscoll, N.

    2007-01-01

    The inner continental shelf off northern South Carolina is a sediment-limited environment characterized by extensive hardground areas, where coastal plain strata and ancient channel-fill deposits are exposed at the sea floor. Holocene sand is concentrated in large shoals associated with active tidal inlets, an isolated shore-detached sand body, and a widespread series of low-relief sand ridges. The regional geologic framework is a strong control on the production, movement and deposition of sediment. High-resolution geologic mapping of the sea floor supports conceptual models indicative of net southwestward sediment transport along the coast.

  2. New Archeointensities from Mid Holocene Archeological Materials

    NASA Astrophysics Data System (ADS)

    Kapper, K.; Donadini, F.; Hirt, A. M.

    2013-12-01

    Paleointensity variation determined from mid Holocene archeomagnetic samples can improve the understanding of Earth's magnetic field and how it has changed during the past 10 000 years. It is important for models of Earth's magnetic field to fill gaps in archeomagnetic data records prior 1000 BC, which are prevalent in European data sets. New data help to complement regional reference curves, which are useful for dating of archeologic artifacts, e.g., pottery or displaced objects such as tiles, if the paleointensity of the object is known. Due to small temporal resolution and uncertainties in data records, the maximum intensity and maximum rate of change of the geomagnetic field is poorly understood. Stacks of intensity records are assumed to smooth out high frequency features in the secular variation curve such as archeomagnetic jerks and geomagnetic spikes. In previous studies it was shown that archeointensities could be measured from various archeological materials, if they were heated and obtain a pure thermoremanent magnetization. Ceramics or potsherds were the first materials to be used to measure the geomagnetic field intensity. They are usually heated to high temperatures and are abundant. In more recent years it was shown that copper slags can be used as well for archeointensity determinations. These are widespread in Europe, Asia and Africa from about 5000 BC onwards, carry a strong magnetization, and charcoal is usually close by or even embedded in the slag and can be used for radiocarbon dating. Samples from burned soils of archeological fires or hearth remains can have accurate archeointensities, provided that the samples carry a pure thermoremanent magnetization, which usually can be found in the center of the fireplace. But for some sites the center is difficult to locate, and relatively loose material may easily suffer from disturbances. In this study we report on results from archeointensity measurements on 91 specimens made of ceramics, slags, and

  3. A new Holocene sea-level database for the US Gulf Coast: Improving constraints for past and future sea levels

    NASA Astrophysics Data System (ADS)

    Hijma, M.; Tornqvist, T. E.; Hu, P.; Gonzalez, J.; Hill, D. F.; Horton, B. P.; Engelhart, S. E.

    2011-12-01

    The interpretation of present-day sea-level change, as well as the prediction of future relative sea-level (RSL) rise and its spatial variability, depend increasingly on the ability of glacial isostatic adjustment (GIA) models to reveal non-eustatic components of RSL change. GIA results from the redistribution of mass due to the growth and decay of ice sheets. As a consequence, formerly ice-covered areas are still rebounding and currently experience RSL fall, while in other areas the rate of RSL rise is enhanced due to glacial forebulge collapse. The development of GIA models relies to a large extent on the availability of quality-controlled Holocene RSL data. There is thus an urgent need for systematically compiled and publicly available databases of geological RSL data that can be used not only for the purposes mentioned above, but also can serve to underpin coastal management and policy decisions. We have focused our efforts to develop a Holocene sea-level database for the Atlantic and Gulf coasts of the US. Many of the research problems that can be addressed with this sea-level database revolve around the identification of crustal motions due to glacial forebulge collapse that affects the entire region and likely extends beyond South Florida. For the east coast, GIA-related subsidence rates have been calculated with unprecedented precision: <0.8 mm a-1 in Maine, increasing to rates of 1.7 mm a-1 in Delaware, and a return to rates <0.9 mm a-1 in the Carolinas. Here, we first define our methodology to reconstruct RSL, with particular reference to the quantification of age and elevation errors. Many sea-level indicators are related to a specific tide level (e.g., peat that formed between highest astronomical tide and mean high water level). We use paleotidal modeling to account for any changes during the Holocene. We furthermore highlight a number of errors associated with 14C dating that have rarely, if ever, been considered in previous studies of this nature

  4. Evolution of foredune barriers at Admiral Bay, Western Australia - Implications for Holocene relative sea levels and extreme wave events

    NASA Astrophysics Data System (ADS)

    Engel, Max; May, Simon Matthias; Scheffers, Anja; Squire, Peter; Pint, Anna; Kelletat, Dieter; Brückner, Helmut

    2014-05-01

    Only few geomorphological studies on the Canning Coast of Western Australia exist to date, most probably reflecting its remoteness and low population density. However, WA's annual gross state product (GSP) growth of ~5 % during the past decade and the highest GSP per capita nationwide resulting from a mining boom increase public attention as well as the demand for precise information on landscape inventory and evolution. In this paper, new data from a sequence of vegetated foredune barriers, gradually being eroded by a migrating estuary inside the macrotidal Admiral Bay (also known as McKelson Creek, Whistle Creek or Panganunganyjal), 110 km southwest of Broome, are presented. Based on sediment cores, DGPS-based elevation transects, and stratigraphical analyses on outcrops of the relict foredunes, we aim at (i) reconstructing lateral coastal changes during the Holocene, (ii) drawing inferences on relative sea-level (RSL) change, and (iii) identifying and dating imprints of extreme-wave events. Sedimentary analyses comprise documentation of bedding structures, foraminiferal content and macrofaunal remains (including shell taphonomy), grain size, and organic matter. Chronological contexts are established using 26 14C-AMS datings. Marine flooding of the pre-Holocene base landward of the 2.5 km-wide foredunes can be pinpointed to 7400-7200 cal BP. A mangrove ecosystem established and was quickly replaced by intertidal coarse sands after only 200-400 years. The high-energy intertidal environment prevailed until c. 4000 cal BP before turning into the present supralittoral mudflat environment. At that time, coastal regression led to beach progradation and isochronic formation of foredune barriers. Drivers of progradation were a stable RSL or gradual RSL fall after the mid-Holocene highstand and a positive sand budget provided by high sublittoral productivity of calcareous shells in combination with erosion at the adjacent sandstone capes and longshore drift. The foredunes

  5. Mid-Holocene regional reorganization of climate variability

    NASA Astrophysics Data System (ADS)

    Wirtz, K. W.; Bernhardt, K.; Lohmann, G.; Lemmen, C.

    2009-01-01

    We integrate 130 globally distributed proxy time series to refine the understanding of climate variability during the Holocene. Cyclic anomalies and temporal trends in periodicity from the Lower to the Upper Holocene are extracted by combining Lomb-Scargle Fourier-transformed spectra with bootstrapping. Results were cross-checked by counting events in the time series. Main outcomes are: First, the propensity of the climate system to fluctuations is a region specific property. Many records of adjacent sites reveal a similar change in variability although they belong to different proxy types (e.g., δ18O, lithic composition). Secondly, at most sites, irreversible change occured in the Mid-Holocene. We suggest that altered ocean circulation together with slightly modified coupling intensity between regional climate subsystems around the 5.5 kyr BP event (termination of the African Humid Period) were responsible for the shift. Fluctuations especially intensified along a pan-American corridor. This may have led to an unequal crisis probability for early human civilizations in the Old and New World. Our study did not produce evidence for millennial scale cyclicity in some solar activity proxies for the Upper Holocene, nor for a privileged role of the prominent 250, 550, 900 and 1450 yr cycles. This lack of global periodicities corroborates the regional character of climate variability.

  6. Mid-Holocene regional reorganization of climate variability

    NASA Astrophysics Data System (ADS)

    Wirtz, K. W.; Bernhardt, K.; Lohmann, G.; Lemmen, C.

    2009-04-01

    We integrate 130 globally distributed proxy time series to refine the understanding of climate variability during the Holocene. Cyclic anomalies and temporal trends in periodicity from the Lower to the Upper Holocene are extracted by combining Lomb-Scargle Fourier-transformed spectra with bootstrapping. Results were cross-checked by counting events in the time series. Main outcomes are: First, the propensity of the climate system to fluctuations is a region specific property. Many records of adjacent sites reveal a similar change in variability although they belong to different proxy types (e.g., δ18O, lithic composition). Secondly, at most sites, irreversible change occured in the Mid- Holocene. We suggest that altered ocean circulation together with slightly modified coupling intensity between regional climate subsystems around the 5.5 kyr BP event (termination of the African Humid Period) were responsible for the shift. Fluctuations especially intensified along a pan- American corridor. This may have led to an unequal crisis probability for early human civilizations in the Old and New World. Our study did not produce evidence for millennial scale cyclicity in some solar activity proxies for the Upper Holocene, nor for a privileged role of the prominent 250, 550, 900 and 1450 yr cycles. This lack of global periodicities corroborates the regional character of climate variability.

  7. 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.

  8. Holocene lake-level fluctuations of Lake Aricota, Southern Peru

    USGS Publications Warehouse

    Placzek, C.; Quade, Jay; Betancourt, J.L.

    2001-01-01

    Lacustrine deposits exposed around Lake Aricota, Peru (17?? 22???S), a 7.5-km2 lake dammed by debris flows, provide a middle to late Holocene record of lake-level fluctuations. Chronological context for shoreline deposits was obtained from radiocarbon dating of vascular plant remains and other datable material with minimal 14C reservoir effects (<350 yr). Diatomites associated with highstands several meters above the modern lake level indicate wet episodes. Maximum Holocene lake level was attained before 6100 14C yr B.P. and ended ???2700 14C yr B.P. Moderately high lake levels occurred at 1700 and 1300 14C yr B.P. The highstand at Lake Aricota during the middle Holocene is coeval with a major lowstand at Lake Titicaca (16?? S), which is only 130 km to the northeast and shares a similar climatology. Comparisons with other marine and terrestrial records highlight emerging contradictions over the nature of mid-Holocene climate in the central Andes. ?? 2001 University of Washington.

  9. Mid-Holocene Hydrologic Model of the Shingobee Watershed, Minnesota

    NASA Astrophysics Data System (ADS)

    Filby, Sheryl K.; Locke, Sharon M.; Person, Mark A.; Winter, Thomas C.; Rosenberry, Donald O.; Nieber, John L.; Gutowski, William J.; Ito, Emi

    2002-11-01

    A hydrologic model of the Shingobee Watershed in north-central Minnesota was developed to reconstruct mid-Holocene paleo-lake levels for Williams Lake, a surface-water body located in the southern portion of the watershed. Hydrologic parameters for the model were first estimated in a calibration exercise using a 9-yr historical record (1990-1998) of climatic and hydrologic stresses. The model reproduced observed temporal and spatial trends in surface/groundwater levels across the watershed. Mid-Holocene aquifer and lake levels were then reconstructed using two paleoclimatic data sets: CCM1 atmospheric general circulation model output and pollen-transfer functions using sediment core data from Williams Lake. Calculated paleo-lake levels based on pollen-derived paleoclimatic reconstructions indicated a 3.5-m drop in simulated lake levels and were in good agreement with the position of mid-Holocene beach sands observed in a Williams Lake sediment core transect. However, calculated paleolake levels based on CCM1 climate forcing produced only a 0.05-m drop in lake levels. We found that decreases in winter precipitation rather than temperature increases had the largest effect on simulated mid-Holocene lake levels. The study illustrates how watershed models can be used to critically evaluate paleoclimatic reconstructions by integrating geologic, climatic, limnologic, and hydrogeologic data sets.

  10. Mid-Holocene hydrologic model of the Shingobee watershed, Minnesota

    USGS Publications Warehouse

    Filby, S.K.; Locke, Sharon M.; Person, M.A.; Winter, T.C.; Rosenberry, D.O.; Nieber, J.L.; Gutowski, W.J.; Ito, E.

    2002-01-01

    A hydrologifc model of the Shingobee Watershed in north-central Minnesota was developed to reconstruct mid-Holocene paleo-lake levels for Williams Lake, a surface-water body located in the southern portion of the watershed. Hydrologic parameters for the model were first estimated in a calibration exercise using a 9-yr historical record (1990-1998) of climatic and hydrologic stresses. The model reproduced observed temporal and spatial trends in surface/groundwater levels across the watershed. Mid-Holocene aquifer and lake levels were then reconstructed using two paleoclimatic data sets: CCM1 atmospheric general circulation model output and pollen-transfer functions using sediment core data from Williams Lake. Calculated paleo-lake levels based on pollen-derived paleoclimatic reconstructions indicated a 3.5-m drop in simulated lake levels and were in good agreement with the position of mid-Holocene beach sands observed in a Williams Lake sediment core transect. However, calculated paleolake levels based on CCM1 climate forcing produced only a 0.05-m drop in lake levels. We found that decreases in winter precipitation rather than temperature increases had the largest effect on simulated mid-Holocene lake levels. The study illustrates how watershed models can be used to critically evaluate paleoclimatic reconstructions by integrating geologic, climatic, limnologic, and hydrogeologic data sets. ?? 2002 University of Washington.

  11. Holocene eolian activity in the Minot dune field, North Dakota

    USGS Publications Warehouse

    Muhs, D.R.; Stafford, Thomas W.; Been, J.; Mahan, S.A.; Burdett, J.; Skipp, G.; Rowland, Z.M.

    1997-01-01

    Stabilized eolian sand is common over much of the Great Plains region of the United States and Canada, including a subhumid area of ??? 1500 km2 near Minot, North Dakota. Eolian landforms consist of sand sheets and northwest-trending parabolic dunes. Dunes and sand sheets in the Minot field are presently stabilized by a cover of prairie grasses or oak woodland. Stratigraphic studies and accelerator mass spectrometry radiocarbon dating of paleosols indicate at least two periods of eolian sand movement in the late Holocene. Pedologic data suggest that all of the dune field has experienced late Holocene dune activity, though not all parts of the dune field may have been active simultaneously. Similar immobile element (Ti, Zr, La, Ce) concentrations support the interpretation that eolian sands are derived from local glaciofluvial and glaciolacustrine sediments. However, glaciolacustrine and glaciofluvial source sediments have high Ca concentrations from carbonate minerals, whereas dune sands are depleted in Ca. Because noneolian-derived soils in the area are calcareous, these data indicate that the Minot dune field may have had extended periods of activity in the Holocene, such that eolian abrasion removed soft carbonate minerals. The southwest-facing parts of some presently stabilized dunes were active during the 1930s drought, but were revegetated during the wetter years of the 1940s. These observations indicate that severe droughts accompanied by high temperatures are the most likely cause of Holocene eolian activity.

  12. Holocene biomass burning and global dynamics of the carbon cycle.

    PubMed

    Carcaillet, C; Almquist, H; Asnong, H; Bradshaw, R H W; Carrión, J S; Gaillard, M J; Gajewski, K; Haas, J N; Haberle, S G; Hadorn, P; Müller, S D; Richard, P J H; Richoz, I; Rösch, M; Sánchez Goñi, M F; von Stedingk, H; Stevenson, A C; Talon, B; Tardy, C; Tinner, W; Tryterud, E; Wick, L; Willis, K J

    2002-12-01

    Fire regimes have changed during the Holocene due to changes in climate, vegetation, and in human practices. Here, we hypothesise that changes in fire regime may have affected the global CO2 concentration in the atmosphere through the Holocene. Our data are based on quantitative reconstructions of biomass burning deduced from stratified charcoal records from Europe, and South-, Central- and North America, and Oceania to test the fire-carbon release hypothesis. In Europe the significant increase of fire activity is dated approximately 6000 cal. yr ago. In north-eastern North America burning activity was greatest before 7500 years ago, very low between 7500-3000 years, and has been increasing since 3000 years ago. In tropical America, the pattern is more complex and apparently latitudinally zonal. Maximum burning occurred in the southern Amazon basin and in Central America during the middle Holocene, and during the last 2000 years in the northern Amazon basin. In Oceania, biomass burning has decreased since a maximum 5000 years ago. Biomass burning has broadly increased in the Northern and Southern hemispheres throughout the second half of the Holocene associated with changes in climate and human practices. Global fire indices parallel the increase of atmospheric CO2 concentration recorded in Antarctic ice cores. Future issues on carbon dynamics relatively to biomass burning are discussed to improve the quantitative reconstructions.

  13. Little late Holocene strain accumulation and release on the Aleutian megathrust below the Shumagin Islands, Alaska

    USGS Publications Warehouse

    Witter, Robert C.; Briggs, Richard W.; Engelhart, Simon E.; Gelfenbaum, Guy R.; Koehler, Richard D.; Barnhart, William D.

    2014-01-01

    Can a predominantly creeping segment of a subduction zone generate a great (M > 8) earthquake? Despite Russian accounts of strong shaking and high tsunamis in 1788, geodetic observations above the Aleutian megathrust indicate creeping subduction across the Shumagin Islands segment, a well-known seismic gap. Seeking evidence for prehistoric great earthquakes, we investigated Simeonof Island, the archipelago's easternmost island, and found no evidence for uplifted marine terraces or subsided shorelines. Instead, we found freshwater peat blanketing lowlands, and organic-rich silt and tephra draping higher glacially smoothed bedrock. Basal peat ages place glacier retreat prior to 10.4 ka and imply slowly rising (<0.2 m/ka) relative sea level since ~3.4 ka. Storms rather than tsunamis probably deposited thin, discontinuous deposits in coastal sites. If rupture of the megathrust beneath Simeonof Island produced great earthquakes in the late Holocene, then coseismic uplift or subsidence was too small (≤0.3 m) to perturb the onshore geologic record.

  14. Ancient harbors and Holocene morphogenesis of the Ras Ibn Hani peninsula (Syria)

    NASA Astrophysics Data System (ADS)

    Marriner, Nick; Goiran, Jean-Philippe; Geyer, Bernard; Matoïan, Valérie; al-Maqdissi, Michel; Leconte, Marion; Carbonel, Pierre

    2012-07-01

    Ras Ibn Hani peninsula, a wave-dominated tombolo (800 × 1000 m) on the Syrian coast, provides evidence for significant Holocene changes that can be linked to geological inheritance, rising post-glacial sea level, sediment supply and human impacts. Initial development of Ras Ibn Hani's coastal system began ~ 8000 years ago when shallow marine environments formed in a context of rising post-glacial sea level. Following relative sea-level stabilization ~ 6000 cal yr BP, beach facies trace the gradual formation of a wave-dominated sandbank fronted by a ~ 2300 × ~ 500 m palaeo-island whose environmental potentiality was attractive to Bronze Age societies. A particularly rapid phase of tombolo accretion is observed after ~ 3500 cal yr BP characterised by a two- to fourfold increase in sedimentation rates. This is consistent with (i) a pulse in sediment supply probably driven by Bronze Age/Iron Age soil erosion in local catchments, and (ii) positive feedback mechanisms linked to regionally attested neotectonics. Archaeological remains and radiocarbon datings confirm that the subaerial tombolo was probably in place by the Late Bronze Age. These data fit tightly with other eastern Mediterranean tombolo systems suggesting that there is a great deal of predictability to their geology and stratigraphy at the regional scale.

  15. Holocene morphogenesis of Alexander the Great's isthmus at Tyre in Lebanon

    PubMed Central

    Marriner, Nick; Morhange, Christophe; Meulé, Samuel

    2007-01-01

    In 332 B.C., Alexander the Great constructed an ≈1,000-m-long causeway to seize the offshore island of Tyre. The logistics behind this engineering feat have long troubled archaeologists. Using the Holocene sedimentary record, we demonstrate that Alexander's engineers cleverly exploited a shallow proto-tombolo, or sublittoral sand spit, to breach the offshore city's defensive impregnability. We elucidate a three-phase geomorphological model for the spit's evolution. Settled since the Bronze Age, the area's geological record manifests a long history of natural and anthropogenic forcings. (i) Leeward of the island breakwater, the maximum flooding surface (e.g., drowning of the subaerial land surfaces by seawater) is dated ≈8000 B.P. Fine-grained sediments and brackish and marine-lagoonal faunas translate shallow, low-energy water bodies at this time. Shelter was afforded by Tyre's elongated sandstone reefs, which acted as a 6-km natural breakwater. (ii) By 6000 B.P., sea-level rise had reduced the dimensions of the island from 6 to 4 km. The leeward wave shadow generated by this island, allied with high sediment supply after 3000 B.P., culminated in a natural wave-dominated proto-tombolo within 1–2 m of mean sea level by the time of Alexander the Great (4th century B.C.). (iii) After 332 B.C., construction of Alexander's causeway entrained a complete anthropogenic metamorphosis of the Tyrian coastal system. PMID:17517668

  16. Latest Pleistocene and Holocene glacier fluctuations on Mount Baker, Washington

    NASA Astrophysics Data System (ADS)

    Osborn, Gerald; Menounos, Brian; Ryane, Chanone; Riedel, Jon; Clague, John J.; Koch, Johannes; Clark, Douglas; Scott, Kevin; Davis, P. Thompson

    2012-08-01

    Glaciers on stratovolcanoes of the Pacific Northwest of North America offer opportunities for dating late Pleistocene and Holocene glacier advances because tephra and fossil wood are common in lateral moraines and in glacier forefields. We capitalize on this opportunity by examining the Holocene glacial record at Mount Baker, an active stratovolcano in northwest Washington. Earlier workers concluded that glaciers on Mount Baker during the early Holocene were more extensive than during the Little Ice Age and hypothesized that the explanation lay in unusual climatic or hypsometric effects peculiar to large volcanoes. We show that the main argument for an early Holocene glacier advance on Mount Baker, namely the absence of ca 10,000-year-old tephra on part of the south flank of the mountain, is incorrect. Moreover, a lake-sediment core indicates that a small cirque moraine previously thought be of early Holocene age is also likely older than the tephra and consequently of late Pleistocene age. Lateral and end moraines and wood mats ca 2 km downvalley of the present snout of Deming Glacier indicate that an advance during the Younger Dryas interval was little more extensive than the climactic Little Ice Age advance. Tephra and wood between tills in the left lateral moraine of Easton Glacier suggest that ice on Mount Baker was restricted in the early Holocene and that Neoglaciation began ca 6 ka. A series of progressively more extensive Neoglacial advances, dated to about 2.2, 1.6, 0.9, and 0.4 ka, are recorded by stacked tills in the right lateral moraine of Deming Glacier. Intervening retreats were long enough to allow establishment of forests on the moraine. Wood mats in moraines of Coleman and Easton glaciers indicate that Little Ice Age expansion began before 0.7 ka and was followed by retreat and a readvance ca 0.5 ka. Tree-ring and lichen data indicate glaciers on the south side of the mountain reached their maximum extents in the mid-1800s. The similarity between

  17. 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

  18. Holocene reef accretion: southwest Molokai, Hawaii, U.S.A.

    USGS Publications Warehouse

    Engels, Mary S.; Fletcher, Charles H.; Field, Michael E.; Storlazzi, Curt D.; Grossman, Eric E.; Rooney, John J.B.; Conger, Christopher L.; Glenn, Craig

    2004-01-01

    Two reef systems off south Molokai, Hale O Lono and Hikauhi (separated by only 10 km), show strong and fundamental differences in modern ecosystem structure and Holocene accretion history that reflect the influence of wave-induced near-bed shear stresses on reef development in Hawaii. Both sites are exposed to similar impacts from south, Kona, and trade-wind swell. However, the Hale O Lono site is exposed to north swell and the Hikuahi site is not. As a result, the reef at Hale O Lono records no late Holocene net accretion while the reef at Hikauhi records consistent and robust accretion over late Holocene time. Analysis and dating of 24 cores from Hale O Lono and Hikauhi reveal the presence of five major lithofacies that reflect paleo-environmental conditions. In order of decreasing depositional energy they are: (1) coral-algal bindstone; (2) mixed skeletal rudstone; (3) massive coral framestone; (4) unconsolidated floatstone; and (5) branching coral framestone-bafflestone. At Hale O Lono, 10 cores document a backstepping reef ranging from ∼ 8,100 cal yr BP (offshore) to ∼ 4,800 cal yr BP (nearshore). A depauperate community of modern coral diminishes shoreward and seaward of ∼ 15 m depth due to wave energy, disrupted recruitment activities, and physical abrasion. Evidence suggests a change from conditions conducive to accretion during the early Holocene to conditions detrimental to accretion in the late Holocene. Reef structure at Hikauhi, reconstructed from 14 cores, reveals a thick, rapidly accreting and young reef (maximum age ∼ 900 cal yr BP). Living coral cover on this reef increases seaward with distance from the reef crest but terminates at a depth of ∼ 20 m where the reef ends in a large sand field. The primary limitation on vertical reef growth is accommodation space under wave base, not recruitment activities or energy conditions. Interpretations of cored lithofacies suggest that modern reef growth on the southwest corner of Molokai, and by

  19. Model for Coastal Restoration

    SciTech Connect

    Thom, Ronald M.; Judd, Chaeli

    2007-07-27

    Successful restoration of wetland habitats depends on both our understanding of our system and our ability to characterize it. By developing a conceptual model, looking at different spatial scales and integrating diverse data streams: GIS datasets and NASA products, we were able to develop a dynamic model for site prioritization based on both qualitative and quantitative relationships found in the coastal environment.

  20. Neotropical coastal wetlands

    USGS Publications Warehouse

    McKee, Karen L.; Batzer, Darold P.; Baldwin, Andrew H.

    2012-01-01

    The Neotropical region, which includes the tropical Americas, is one of the world's eight biogeographic zones. It contains some of the most diverse and unique wetlands in the world, some of which are still relatively undisturbed by humans. This chapter focuses on the northern segment of the Neotropics (south Florida, the Caribbean islands, Mexico, and Central America), an area that spans a latitudinal gradient from about 7 N to 29 N and 60 W to 112 W. Examples of coastal wetlands in this realm include the Everglades (Florida, USA), Ten Thousand Islands (Florida, USA), Laguna de Terminos (Mexico), Twin Cays (Belize), and Zapata Swamp (Cuba). Coastal wetlands are dominated by mangroves, which will be emphasized here, but also include freshwater swamps and marshes, saline marshes, and seagrass beds. The aim of this chapter is to provide a broad overview of Neotropical coastal wetlands of the North American continent, with an emphasis on mangroves, since this is the dominant vegetation type and because in-depth coverage of all wetland types is impossible here. Instead, the goal is to describe the environmental settings, plant and animal communities, key ecological controls, and some conservation concerns, with specific examples. Because this book deals with wetlands of North America, this chapter excludes coastal wetlands of South America. However, much of the information is applicable to mangrove, marsh, and seagrass communities of other tropicaI regions.

  1. MANAGING COASTAL DATA

    EPA Science Inventory

    To answer broad-scale questions on environmental conditions, the Environmental Monitoring and Assessment Program (EMAP) and its partners have collected estuarine and coastal data from hundreds of stations along the coasts of the continental United States. Types of data include w...

  2. 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.

  3. Drivers of Holocene sea-level change in the Caribbean

    NASA Astrophysics Data System (ADS)

    Khan, Nicole S.; Ashe, Erica; Horton, Benjamin P.; Dutton, Andrea; Kopp, Robert E.; Brocard, Gilles; Engelhart, Simon E.; Hill, David F.; Peltier, W. R.; Vane, Christopher H.; Scatena, Fred N.

    2017-01-01

    We present a Holocene relative sea-level (RSL) database for the Caribbean region (5°N to 25°N and 55°W to 90°W) that consists of 499 sea-level index points and 238 limiting dates. The database was compiled from multiple sea-level indicators (mangrove peat, microbial mats, beach rock and acroporid and massive corals). We subdivided the database into 20 regions to investigate the influence of tectonics and glacial isostatic adjustment on RSL. We account for the local-scale processes of sediment compaction and tidal range change using the stratigraphic position (overburden thickness) of index points and paleotidal modeling, respectively. We use a spatio-temporal empirical hierarchical model to estimate RSL position and its rates of change in the Caribbean over 1-ka time slices. Because of meltwater input, the rates of RSL change were highest during the early Holocene, with a maximum of 10.9 ± 0.6 m/ka in Suriname and Guyana and minimum of 7.4 ± 0.7 m/ka in south Florida from 12 to 8 ka. Following complete deglaciation of the Laurentide Ice Sheet (LIS) by ∼7 ka, mid-to late-Holocene rates slowed to < 2.4 ± 0.4 m/ka. The hierarchical model constrains the spatial extent of the mid-Holocene highstand. RSL did not exceed the present height during the Holocene, except on the northern coast of South America, where in Suriname and Guyana, RSL attained a height higher than present by 6.6 ka (82% probability). The highstand reached a maximum elevation of +1.0 ± 1.1 m between 5.3 and 5.2 ka. Regions with a highstand were located furthest away from the former LIS, where the effects from ocean syphoning and hydro-isostasy outweigh the influence of subsidence from forebulge collapse.

  4. Coastal hazards: hurricanes, tsunamis, coastal erosion

    USGS Publications Warehouse

    Vandas, Stephen; Mersfelder, Lynne; Farrar, Frank; France, Rigoberto Guardado; Yajimovich, Oscar Efraín González; Muñoz, Aurora R.; Rivera, María del C.

    1996-01-01

    Oceans are the largest geographic feature on the surface of the Earth, covering approximately 70% of the planet's surface. As a result, oceans have a tremendous impact on the Earth, its climate, and its inhabitants. The coast or shoreline is the boundary between ocean environments and land habitats. By the year 2025, it is estimated that approximately two-thirds of the world's population will be living within 200 kilometers of a coast. In many ways, we treat the coast just like any other type of land area, as a safe and stable place to live and play. However, coastal environments are dynamic, and they constantly change in response to natural processes and to human activities.

  5. Holocene fault scarps in the Western Alps

    NASA Astrophysics Data System (ADS)

    Hippolyte, J. C.

    2003-04-01

    In the Tarentaise Valley, Goguel (1969) had described recent fault scarps. The present work shows that they are normal faults indicating a SE-directed trend of extension in agreement with recent microseismicity data (Sue et al., 1999). It is proposed that they reflect the Quaternary normal reactivation of the "Front du Houiller" thrust fault. In the Belledonne external crystalline massif, Bordet (1970) had observed from helicopter three main fault scarps that he interpreted as active SE-dipping reverse faults. Partly owing to the difficulties of access this area was not visited until now. Field observations reveal that these faults dip in fact 61-68° to the NW, and are normal faults. The faults scarps are 1 to 13 meters high. These faults, together with at least 10 newly discovered conjugate SE-dipping normal fault scarps of 0.5 to 18 meters high, form an about 2 km wide fault zone along the "Synclinal Median" (S.M.) fault. They attest for the activity of this 70 km-long NNE-striking main fault running in the middle of the Belledonne Massif. Its activity is confirmed by major faceted spurs at the La Perche, the La Perrière and the Claran passes, and by ruptures cutting moraines. Other fault scarps are discovered in the whole Belledonne massif showing in particular that the Font-de-France fault, a 60 km-long SE-dipping fault, is also active. All the observed active faults are normal. Their offsets of mountains slopes, of screes and of rock glacier morphologies demonstrate their activity during the Holocene. They indicate a present SE-directed extension in agreement with recent GPS data (Calais et al., 2002). This mapping shows that the present extensional deformation of the Alps is not limited to the west by the "Frontal Pennine thrust" (Sue et al., 1999) but affects also the external Alps. Taking into account focal plane mechanisms, extension affects at least 70 % of the Western Alps. Some scarps have been sampled for Beryllium cosmogenic dating. However

  6. Improving the timing of middle Holocene retreat and late Holocene advance of Jakobshavn Isbrae, Greenland

    NASA Astrophysics Data System (ADS)

    Briner, J. P.; Stewart, H. A.; Young, N. E.; Csatho, B.; Axford, Y.

    2009-04-01

    The Greenland Ice Sheet is undergoing dramatic change. How the ice sheet continues to respond to climate change has important ramifications for global climate and sea level rise, but the observation-based record of ice sheet change is extremely short. We use glacial-geologic techniques to determine the behavior of the Greenland Ice Sheet over longer timescales. In particular, we focus on the Holocene history of Jakobshavn Isbrae, one of the key ice streams on Greenland that is responsible for disproportionate mass loss of the Greenland Ice Sheet. Radiocarbon ages from basal lake sediments and 10Be exposure ages of bedrock spanning from the present ice margin to Disko Bugt, ~50 km west, reveal rapid deglaciation between ~8 and ~7 ka. After ~7 ka, the ice margin continued to retreat inland behind its present position. Although it is difficult to reconstruct how far inland the ice margin retreated, the Little Ice Age advance reworked marine bivalves that date from 2.2 to 6.1 ka (Weidick and Bennike, 2007). The bivalve ages indicate that the ice margin was behind its Little Ice Age position between ~6 and ~2 ka, and that its Neoglacial advance post-dates ~2 ka. We improve the timing of the Neoglacial advance of Jakobshavn Isbrae by collecting sediment cores from lakes that are beyond the Little Ice Age margin but close enough to receive ice sheet meltwater during the Little Ice Age advance. The sediments in these "threshold" lakes contain distinct units of varved sediments (representing a proglacial environment) that sharply overlie gyttja (representing a non-glacial environment). Four radiocarbon ages of the sedimentary contacts from three different lake sites range from 530±10 to 370±60 cal yr BP (1410-1640 AD), and reveal when Jakobshavn Isbrae neared its maximum Little Ice Age margin. Furthermore, the lake sediments reveal that between early Holocene deglaciation and the Little Ice Age, Jakobshavn Isbrae never spilled into these lake basins, indicating that the

  7. Stable isotope enrichment in paleowaters of the southeast atlantic coastal plain, United States.

    PubMed

    Plummer, L N

    1993-12-24

    Paleowaters from the Floridan aquifer system in the southeastern Atlantic coastal plain have higher D/H and (18)O/(16)O ratios than local Holocene ground water. Maximum delta(18)O enrichments in ground water having adjusted radiocarbon ages of 20,000 to 26,000 years are 0.7 to 2.3 per mil. The trend in isotopic enrichment in paleowaters is the reverse of that normally observed in continental glacial age ground water. Dissolved nitrogen and argon concentrations indicate, however, that the average recharge temperature was 5.3 degrees C cooler than that today. The data indicate cool conditions in the southeast Atlantic coastal plain during the last glacial maximum, with recharge limited primarily to late summer tropical cyclones and hurricanes.

  8. Stable isotope enrichment in paleowaters of the southeast atlantic coastal plain, United States

    SciTech Connect

    Plummer, L.N. )

    1993-12-24

    Paleowaters from the Floridan aquifer system in the southeastern Atlantic coastal plain have higher D/H and [sup 18]O/[sup 16]O ratios than local Holocene groundwater. Maximum [delta][sup 18]O enrichments in groundwater having adjusted radiocarbon ages of 20,000 to 26,000 years are 0.7 to 2.3 per mil. The trend in isotopic enrichment in paleowaters is the reverse of that normally observed in continental glacial age groundwater. Dissolved nitrogen and argon concentrations indicate, however, that the average recharge temperature was 5.3[degrees]C cooler than that today. The data indicate cool conditions in the southeast Atlantic coastal plain during the last glacial maximum, with recharge limited primarily to late summer tropical cyclones and hurricanes.

  9. Stable isotope enrichment in paleowaters of the southeast Atlantic coastal plain, United States

    USGS Publications Warehouse

    Plummer, L.N.

    1993-01-01

    Paleowaters from the Floridan aquifer system in the southeastern Atlantic coastal plain have higher D/H and 18O/16O ratios than local Holocene ground water. Maximum ??18O enrichments in ground water having adjusted radiocarbon ages of 20,000 to 26,000 years are 0.7 to 2.3 per mil. The trend in isotopic enrichment in paleowaters is the reverse of that normally observed in continental glacial age ground water. Dissolved nitrogen and argon concentrations indicate, however, that the average recharge temperature was 5.3??C cooler than that today. The data indicate cool conditions in the southeast Atlantic coastal plain during the last glacial maximum, with recharge limited primarily to late summer tropical cyclones and hurricanes.

  10. Climate changes and solar cycles recorded at the Holocene Paraná Delta, and their impact on human population

    PubMed Central

    Milana, Juan Pablo; Kröhling, Daniela

    2015-01-01

    The Paraná delta, growing at a rate of c. 2 km2 yr−1 since 6,000 yrs, is one of the most complete records of the Late Holocene in southern South America. The evolution of this 17,400 km2 delta enclosed in Plata estuary, can be tracked by a series of 343 successive coastal-ridges showing a c.11 years period, in coincidence with sunspot cycle, also found in some North Hemisphere coastal-ridge successions. The Paraná delta shifted from fluvial, to wave-dominated, and back to the present fluvial-dominated delta, in response to climate changes associated with wind activity correlating with South American glacial cycles. The wave-dominated windy period coincides with the activation of the Pampean Sand Sea, suggesting desert conditions prevailed on the Pampas between 5,300 and 1,700 yrs, in coincidence with scarce or absent pre-historic aborigine remains (“archeological silence”). Further warmer and less windy conditions allowed human repopulation. Results suggest that aside the solar forcing, both short and medium term climate changes controlled delta evolution. An important learning is that a slight cooling would turn the highly productive pampas, into that unproductive desert and, given the lack of artificial irrigation systems, changing present-day warmhouse into a cooling cycle might be economically catastrophic for the region. PMID:26246410

  11. Radiocarbon reservoir effect from shell and plant pairs in Holocene sediments around the Yeongsan River in Korea

    NASA Astrophysics Data System (ADS)

    Nakanishi, Toshimichi; Hong, Wan; Sung, Ki Suk; Lim, Jaesoo

    2013-01-01

    The marine reservoir effect was measured by comparing the radiocarbon ages of shell and plant pairs obtained from the same horizons of a sediment core around the Yeongsan River in the southwestern part of the Korean Peninsula. The Holocene sediment formed in five environments: tidal flat, inner bay, shallow marine, flood plain, and embankment from bottom to top. The tidal flat and shallow marine sediments should be good indicators of marine reservoir effect, as they formed in coastal environments where it was easy to access not only marine shells but also terrestrial plants. Some old detritus could be identified and removed, based on reliable accumulation curves and sedimentological interpretation. Hence, the age differences between the plants and shells could be successfully evaluated, and they indicated that the marine reservoir effect varied over time between 0 and 500 years. There was an increase of this effect at ca. 8000 cal year BP and a decrease at ca. 5000 cal year BP, possibly linked with coastal environment changes induced by sea level changes and by changes in the circulation of seawater.

  12. Climate changes and solar cycles recorded at the Holocene Paraná Delta, and their impact on human population

    NASA Astrophysics Data System (ADS)

    Milana, Juan Pablo; Kröhling, Daniela

    2015-08-01

    The Paraná delta, growing at a rate of c. 2 km2 yr-1 since 6,000 yrs, is one of the most complete records of the Late Holocene in southern South America. The evolution of this 17,400 km2 delta enclosed in Plata estuary, can be tracked by a series of 343 successive coastal-ridges showing a c.11 years period, in coincidence with sunspot cycle, also found in some North Hemisphere coastal-ridge successions. The Paraná delta shifted from fluvial, to wave-dominated, and back to the present fluvial-dominated delta, in response to climate changes associated with wind activity correlating with South American glacial cycles. The wave-dominated windy period coincides with the activation of the Pampean Sand Sea, suggesting desert conditions prevailed on the Pampas between 5,300 and 1,700 yrs, in coincidence with scarce or absent pre-historic aborigine remains (“archeological silence”). Further warmer and less windy conditions allowed human repopulation. Results suggest that aside the solar forcing, both short and medium term climate changes controlled delta evolution. An important learning is that a slight cooling would turn the highly productive pampas, into that unproductive desert and, given the lack of artificial irrigation systems, changing present-day warmhouse into a cooling cycle might be economically catastrophic for the region.

  13. Climate changes and solar cycles recorded at the Holocene Paraná Delta, and their impact on human population.

    PubMed

    Milana, Juan Pablo; Kröhling, Daniela

    2015-08-06

    The Paraná delta, growing at a rate of c. 2 km(2) yr(-1) since 6,000 yrs, is one of the most complete records of the Late Holocene in southern South America. The evolution of this 17,400 km(2) delta enclosed in Plata estuary, can be tracked by a series of 343 successive coastal-ridges showing a c.11 years period, in coincidence with sunspot cycle, also found in some North Hemisphere coastal-ridge successions. The Paraná delta shifted from fluvial, to wave-dominated, and back to the present fluvial-dominated delta, in response to climate changes associated with wind activity correlating with South American glacial cycles. The wave-dominated windy period coincides with the activation of the Pampean Sand Sea, suggesting desert conditions prevailed on the Pampas between 5,300 and 1,700 yrs, in coincidence with scarce or absent pre-historic aborigine remains ("archeological silence"). Further warmer and less windy conditions allowed human repopulation. Results suggest that aside the solar forcing, both short and medium term climate changes controlled delta evolution. An important learning is that a slight cooling would turn the highly productive pampas, into that unproductive desert and, given the lack of artificial irrigation systems, changing present-day warmhouse into a cooling cycle might be economically catastrophic for the region.

  14. Holocene biome shifts in the East Asian monsoon margin region

    NASA Astrophysics Data System (ADS)

    Dallmeyer, Anne; Claussen, Martin; Ni, Jian; Wang, Yongbo; Cao, Xianyong; Herzschuh, Ulrike

    2013-04-01

    East Asia is affected by three major atmospheric circulation systems determining the regional climate and vegetation distribution: The moisture advected by the Indian and East Asian monsoon support the growing of forest in large parts of Eastern China. The influence of the monsoon gets weaker further on the continent yielding a transition of forest to steppe and of steppe to desert in Central East Asia (e.g. Inner Mongolia) where the dry westerly winds prevail. Particularly in these transition zones, vegetation is supposed to be very sensitive to climate change and strong feedbacks are expected in case of climate and vegetation shifts due to large environmental changes (Feng et al., 2006). During mid-Holocene, cyclic variations in the Earth's orbit around the sun led to an enhancement of the Asian monsoon system probably causing strong shifts in the biome distribution. According to reconstructions, the steppe-forest margin moved to the northwest by about 500km (Yu et al., 2000) and the desert area in China and Inner Mongolia was substantially reduced compared to today (Feng et al., 2006). However, in the complex environment of Asia, the locally limited reconstructions may not portray the general vegetation change. To get a systematic overview on the spatial pattern of biome shifts in the Asian monsoon - westerly wind transition zone since mid-Holocene, we use the diagnostic vegetation model BIOME4 and force this model with climate anomalies from different transient Holocene climate simulations performed in coupled atmosphere-ocean-vegetation models. The main aims of this study are to a) get a consistent ensemble of possible changes in biome distribution since the mid-Holocene b) test the robustness of the simulated vegetation changes and quantify the differences between the models, and c) allow for a better comparison of simulated and reconstructed vegetation changes. Preliminary results confirm the general trend seen in the reconstructions. The simulations reveal

  15. Coastal Paleoclimate: Unraveling Temperature and Salinity History Using Ostracode Shell Chemistry

    NASA Astrophysics Data System (ADS)

    Dwyer, G. S.; Cronin, T. M.; Vann, C. D.; Kamiya, T.

    2001-12-01

    Long-term records of temperature and salinity of coastal waters are important for understanding coastal environmental change, its linkages to regional, hemispheric or global climate change, and its impact on coastal ecosystems and cultures, yet few reliable, widely applicable temperature and salinity proxies are available for coastal settings. To address this need, we developed magnesium/calcium (Mg/Ca) paleothermometry in calcitic shells of benthic ostracode Loxoconcha, a common genus found in shallow shelf, lagoon, and estuarine systems from tropical to temperate latitudes. Calibration studies, including analysis of field and laboratory-raised specimens as well as ambient water chemistry from a wide range of temperatures and salinties (T=10 to 30 deg. C, S=15 to 40 ppt), confirm a strong Mg/Ca-temperature relationship. We have applied this relation to sediment cores from Chesapeake Bay to reconstruct late Holocene water temperature which, when coupled with benthic ostracode or foraminifer stable oxygen isotopes (\\delta18Ob), permits removal of the temperature effect on \\delta18Ob and the direct calculation of the \\delta18O of the water. This in turn provides an estimate of paleosalinity and regional runoff and precipitation. At salinity below approximately 15 ppt and in regions where coastal geology is dominated by limestone, the Mg/Ca-temperature relation can be complicated due to the influence of runoff on the Mg/Ca ratio of local coastal waters. Such is the case for eastern Florida Bay, where salinity-dependent, runoff-driven changes in water Mg/Ca ratios appear to override the temperature effect on shell Mg/Ca ratios. Multi-decadal to inter-annual variability in ostracode Mg/Ca records from this coastal setting thus primarily reflects salinity fluctuations that appear to be associated with ENSO-driven winter rainfall anomalies.

  16. Did Iceland's icecaps disappear in the Warm Early Holocene?

    NASA Astrophysics Data System (ADS)

    Geirsdottir, A.; Miller, G. H.; Black, J.; Thordarson, T.

    2002-12-01

    We address the magnitude of Holocene climate change in the North Atlantic region, especially the warmth of the early Holocene, by reconstructing changes in Langjokull, one of the four largest icecaps on Iceland today. Outlet glaciers from Langjokull drained into Hvitarvatn, a large (12 x 3 km; 70 m deep) lake until AD 1945, and continue to dominate sedimentation in the lake at present. If the icecap disappeared in the early Holocene, sedimentation would have been slow and dominated by fluvially transported sediment. When glacial erosion occurs in the catchment, sedimentation rates increase and grain size decreases. When outlet glaciers calve directly into the lake, ice-rafted detritus (IRD) occurs. Because Iceland's climate, and therefore glacier mass balance, is highly sensitive to ocean/atmosphere changes in the North Atlantic, the status of Iceland's glaciers provides a sensitive monitor of North Atlantic climate change throughout the Holocene. Seismic reflection data divide the history of sedimentation into five well-defined episodes: The basin is floored by an acoustically chaotic seismic unit with an undulating upper contact (till). Ponded on the basal seismic unit is a seismic facies 10 to >30 m thick showing prograding reflection characteristics with common hard reflectors indicating deltaic deposition (deglaciation). Unit 3 is a 3-to-5-m-thick, acoustically transparent, suggesting lacustrine sedimentation without episodes of rapid sedimentation. The upper two seismic units are characterized by closely spaced strong horizontal seismic reflectors indicative of glacier-dominated sedimentation (Neoglaciation). To evaluate the long-term status of Langj”kull we cored on a bedrock high, where sedimentation is dominated by suspension settling. We sampled 13 m of sediment in two 5.4 m cores, reaching most of the way through seismic unit 3. Seismic Units 1 and 2 (upper10 m) are laminated, with the laminations increasing in definition and thickness towards the

  17. Holocene environmental change at the oasis of Tayma

    NASA Astrophysics Data System (ADS)

    Engel, Max; Brückner, Helmut; Wellbrock, Kai; Pint, Anna; Grottker, Matthias; Voss, Peter; Ginau, Andreas; Klasen, Nicole; Frenzel, Peter

    2013-04-01

    The oasis of Tayma in northwestern Saudi Arabia has a rich cultural heritage comprising a large number of historic buildings and artefacts from the late Neolithic onwards. Extensive groundwater resources and the location at a branch of the Incense Road connecting south Arabia and the eastern Mediterranean determined the site's importance in Antiquity. This paper reports about Holocene environmental change at Tayma setting the frame for the interpretation of the archaeological record. Humid conditions during the early Holocene are inferred for the Arabian Peninsula (AP) based on the investigation of sabkhas, palaeo-lakes, sand dunes, wadis, speleothems and marine sediments. Most of these climate archives are located in the southern and southeastern part of the AP, where a northward shift of the Intertropical Convergence Zone (ITCZ) triggered increased rainfall at the onset of the Holocene. At Tayma, where the influence of the ITCZ shift can be excluded, the sedimentary infill of a sabkha basin, the micro- and macrofaunal record, a digital elevation model based on DGPS measurements, and 14C-AMS data indicate the presence of a perennial lake with a minimum depth of 13 m, a stored water volume of 1.16 107 m3 and a surface of 18.45 km2 between 10,000-9000 cal BP. Foraminiferal test malformations and the shape of sieve pores on ostracod valves were used to detect trends in palaeo-salinity and ecological stress conditions. Contraction of the lake at least after 8500 cal BP is a response to a long-term aridisation trend subsequent to the early Holocene. Based on the hydrological water balance equation, quantitative data on minimum palaeo-rainfall during the early Holocene humid period were determined. Input parameters for the equation are the minimum lake level, lake surface and lake volume during the peak of the early Holocene humid period as well as palaeo-evapotranspiration, groundwater infiltration, and surface runoff. A perennial lake in the endorheic basin of the

  18. Patagonian and southern South Atlantic view of Holocene climate

    NASA Astrophysics Data System (ADS)

    Kaplan, M. R.; Schaefer, J. M.; Strelin, J. A.; Denton, G. H.; Anderson, R. F.; Vandergoes, M. J.; Finkel, R. C.; Schwartz, R.; Travis, S. G.; Garcia, J. L.; Martini, M. A.; Nielsen, S. H. H.

    2016-06-01

    We present a comprehensive 10Be chronology for Holocene moraines in the Lago Argentino basin, on the east side of the South Patagonian Icefield. We focus on three different areas, where prior studies show ample glacier moraine records exist because they were formed by outlet glaciers sensitive to climate change. The 10Be dated records are from the Lago Pearson, Herminita Península-Brazo Upsala, and Lago Frías areas, which span a distance of almost 100 km adjacent to the modern Icefield. New 10Be ages show that expanded glaciers and moraine building events occurred at least at 6120 ± 390 (n = 13), 4450 ± 220 (n = 7), 1450 or 1410 ± 110 (n = 18), 360 ± 30 (n = 5), and 240 ± 20 (n = 8) years ago. Furthermore, other less well-dated glacier expansions of the Upsala Glacier occurred between 1400 and ∼1000 and ∼2300 and ∼2000 years ago. The most extensive glaciers occurred over the interval from ∼6100 to ∼4500 years ago, and their margins over the last ∼600 years were well within and lower than those in the middle Holocene. The 10Be ages agree with 14C-limiting data for the glacier histories in this area. We then link southern South American, adjacent South Atlantic, and other Southern Hemisphere records to elucidate broader regional patterns of climate and their possible causes. In the early Holocene, a far southward position of the westerly winds fostered warmth, small Patagonian glaciers, and reduced sea ice coverage over the South Atlantic. Although we infer a pronounced southward displacement of the westerlies during the early Holocene, these conditions did not occur throughout the southern mid-high latitudes, an important exception being over the southwest Pacific sector. Subsequently, a northward locus and/or expansion of the winds over the Patagonia-South Atlantic sector promoted the largest glaciers between ∼6100 and ∼4500 years ago and greatest sea ice coverage. Over the last few millennia, the South Patagonian Icefield has experienced

  19. Hydrogeologic framework of the North Carolina Coastal Plain aquifer system

    USGS Publications Warehouse

    Winner, M.D.; Coble, R.W.

    1989-01-01

    The hydrogeologic framework of the North Carolina Coastal Plain aquifer system consists of ten aquifers separated by nine confining units. From top to bottom the aquifers are: the surficial aquifer, Yorktown aquifer, Pungo River aquifer, Castle Hayne aquifer, Beaufort aquifer, Peedee aquifer, Black Creek aquifer, upper Cape Fear aquifer, lower Cape Fear aquifer, and the Lower Cretaceous aquifer. The uppermost aquifer (the surficial aquifer in most places) is a water-table aquifer and the bottom of the system is underlain by crystalline bedrock. The sedimentary deposits forming the aquifers are of Holocene to Cretaceous age and are composed mostly of sand with lesser amounts of gravel and limestone. Confining units between aquifers are composed primarily of clay and silt. The thickness of the aquifers ranges from zero along the Fall Line to more than 10,000 feet at Cape Hatteras. Prominent structural features are the increasing easterly homoclinal dip of the sediments and the Cape Fear arch, the axis of which trends in a southeast direction. The stratigraphic continuity is determined from correlations of 161 geophysical logs along with data from drillers' and geologists' logs. Aquifers were defined by means of these logs plus water-level and water-quality data and evidence of the continuity of pumping effects. Eighteen hydrogeologic sections depict the correlation of these aquifers throughout the Coastal Plain.

  20. Hydrogeologic framework of the North Carolina coastal plain

    USGS Publications Warehouse

    Winner, M.D.; Coble, R.W.

    1996-01-01

    The hydrogeologic framework of the North Carolina Coastal Plain aquifer system consists of 10 aquifers separated by 9 confining units. From top to bottom, the aquifers are the surficial aquifer, Yorktown aquifer, Pungo River aquifer, Castle Hayne aquifer, Beaufort aquifer, Peedee aquifer, Black Creek aquifer, upper Cape Fear aquifer, lower Cape Fear aquifer, and Lower Cretaceous aquifer. The uppermost aquifer (the surficial aquifer in most places) is a water-table aquifer, and the bottom of the system is underlain by crystalline bedrock. The sedimentary deposits forming the aquifers are of Holocene to Cretaceous age and are composed mostly of sand, with lesser amounts of gravel and limestone. The confining units between the aquifers are composed primarily of clay and silt. The thickness of the aquifers ranges from zero along the Fall Line to more than 10,000 feet at Cape Hatteras. Prominent structural features are the increasing easterly homoclinal dip of the sediments and the Cape Fear arch, the axis of which trends in a southeast direction. Stratigraphic continuity was determined from correlations of 161 geophysical logs along with data from drillers? and geologists? logs. Aquifers were defined by means of these logs as well as water-level and water-quality data and evidence of the continuity of pumping effects. Eighteen hydrogeologic sections depict the correlation of these aquifers throughout the North Carolina Coastal Plain.

  1. Simulating decadal coastal morphodynamics

    NASA Astrophysics Data System (ADS)

    Nicholls, Robert J.; French, Jon R.; van Maanen, Barend

    2016-03-01

    Coastal geomorphic systems provide many services of key importance to humankind, including protection from flood and erosion hazards, diverse habitats and amenity values (Agardy et al., 2005; Jones et al., 2011). However, these systems are widely undergoing degradation that can be substantially attributed to the cumulative direct and indirect effects of human interference. Declining sediment inputs and throughputs are frequently a factor driving a shift towards progressive coastal erosion (Valiela, 2006; Nicholls et al., 2007). Such sediment starved systems have reduced resilience and are further threatened by human-induced climate change, not only due to accelerated sea-level rise, but also through possible shifts in wave and surge climate (Wong et al., 2014).

  2. Mid- to Late Holocene Sea-Level Record in French Polynesia, South-Central Pacific

    NASA Astrophysics Data System (ADS)

    Hallmann, N.; Camoin, G.; Vella, C.; Eisenhauer, A.; Samankassou, E.; Botella, A.; Milne, G. A.; Fietzke, J.; Dussouillez, P.; Plaine, J.

    2014-12-01

    The Mid- to Late Holocene provides the opportunity to study the coastal response to sea-level change that has a similar amplitude (i.e., a few decimetres up to 1 m) to the sea-level rise that is likely to occur before the end of the current century. Furthermore, this time period provides an important baseline of natural climate variability prior to the industrial revolution. This study aims to reconstruct Mid- to Late Holocene relative sea-level change in French Polynesia by examining coral reef records from ten islands, which represent ideal settings for accurate sea-level change studies because: 1) they can be regarded as tectonically stable during the relevant period (slow subsidence), 2) they are located far from former ice sheets ('far-field'), 3) they are characterized by a low tidal amplitude, and 4) they cover a wide range of latitudes which produces significantly improved constraints on GIA (Glacial Isostatic Adjustment) model parameters. The accurate reconstruction of sea-level change relies on absolute U/Th dating of in situ coral colonies and their accurate positioning via GPS RTK (Real Time Kinematic) measurements with a vertical and horizontal precision of ± 2.5 cm and ~1 cm, respectively. We focus mainly on the analysis of coral microatolls, which are sensitive low-tide recorders, as their vertical accretion is limited by the water level. Their growth patterns allow the reconstruction of low-amplitude and high-frequency sea-level changes on centennial to sub-decadal time scales. A sea-level rise of less than ~1 m is documented between 6 and 3-3.5 ka, and is followed by a gradual fall in sea level that started around 2 ka and persisted until the past few centuries. The reconstructed sea-level curve therefore extends the Tahiti sea-level curve [Deschamps et al., 2012, Nature, 483, 559-564], and is in good agreement with a geophysical model tuned to fit far-field deglacial records [Bassett et al., 2005, Science, 309, 925-928].

  3. Holocene hydrological and sea surface temperature changes in the northern coast of the South China Sea

    NASA Astrophysics Data System (ADS)

    Wu, Mong-Sin; Zong, Yongqiang; Mok, Ka-Man; Cheung, Ka-Ming; Xiong, Haixian; Huang, Guangqing

    2017-03-01

    In order to reconstruct the Holocene environmental history of a coastal site in the northern South China Sea, this study analysed the organic carbon isotope ratios (δ13Corg) and alkenone unsaturation ratios (UK‧37) from a 36.5 m-long sediment core drilled at seabed in the mouth region of the Pearl River estuary and generated a coupled hydrological and temperature record. This record reveals changes of monsoon-induced sediment discharge and sea surface temperature of the Holocene in four stages. In Stage I, the site was under fluvial conditions prior to postglacial marine transgression. Stage II saw an increase of sea surface temperature from c. 23.0 °C to 27.0 °C, associated with a strengthened summer monsoon from c. 10,350 to 8900 cal. years BP. This was also a period of rapid sea-level rise and marine transgression, during which the sea inundated the palaeo-incised channel, i.e. the lower part of the T-shape accommodation space created by the rising sea. In these 1500 years, fluvial discharge was strong and concentrated within the channel, and the high sedimentation rate (11.8 mm/year) was very close to the rate of sea-level rise. In the subsequent 2000 years (Stage III) sea level continued to rise and the sea flooded the broad seabed above the palaeo-incised channel, resulted in fluvial discharge spreading thinly across the wide accommodation space and a much reduced sedimentation rate (1.8 mm/year). Sea surface temperature in this stage reached 27.3 °C initially, but dropped sharply to 26.1 °C towards c. 8200 cal. years BP. The final stage covers the last 7000 years, and the site was under a stable sea level. Sedimentation in this stage varied a little, but averaged at 1.8 mm/year. Whilst fluvial discharge and sea surface temperature didn't change much, two short periods of hydrological and temperature change were observed, which are related to the climatic cooling events of c. 4200 cal. years ago and the Little Ice Age.

  4. Changes in the northern Adriatic molluscan community from the Holocene transgression up to the present

    NASA Astrophysics Data System (ADS)

    Gallmetzer, Ivo; Haselmair, Alexandra; Tomasovych, Adam; Stachowitsch, Michael; Zuschin, Martin

    2016-04-01

    The northern Adriatic Sea is one of the few modern, epicontinental seas comparable to typical Palaeozoic shelf environments. It has a shallow average water depth (<50 m) and was formed at the end of the last glaciation when the sea level rose. Since historical times this part of the Adriatic has been strongly influenced by human activities through multiple direct or indirect impacts (e.g. fishing, coastal building development, pollution, eutrophication, increased sedimentation), making it one of the most degraded marine ecosystems worldwide. Our study was designed to reconstruct major environmental changes here since the onset of the Holocene transgression using down-core changes in death assemblages of molluscs as indicators for ecological shifts. The sediment cores were taken at three different stations (Brijuni Islands, Croatia, off Piran, Slovenia, and off Venice, Italy), each representative of specific sediment and nutrient conditions and degrees of habitat exploitation. The cores were 1.5 m long and had diameters of 90 or 160 mm. For the molluscan shell analyses, sediment subsamples were examined for species composition, abundance, taxonomic similarity and ecological interactions (e.g. frequencies of drilling predation). In total, 98,700 valves and shells were investigated and 113 bivalve and 178 gastropod species recorded. Sedimentation rates derived from 210Pb dating are very low, between 0.15 cm/yr at Brijuni and 0.25 cm/yr at Piran. The dating of Lucinella divaricata, Timoclea ovata and Gouldia minima shells with 14C calibrated amino-acid racemisation (AAR) revealed that the cores at all three stations cover at least 6000 to 8000 years, i.e. the whole Holocene transgression period. Time averaging is high, especially in the lower core layers of Piran station, probably due to strong bioturbation. Surface mixed-layer assemblages tend to show right-skewed postmortem age-frequency distributions, whereas subsurface assemblages show unimodal or uniform shapes

  5. Reconstructing Late Holocene Relative Sea-level Changes on the Gulf Coast of Florida

    NASA Astrophysics Data System (ADS)

    Gerlach, M. J.; Engelhart, S. E.; Kemp, A.; Moyer, R. P.; Smoak, J. M.; Bernhardt, C. E.

    2015-12-01

    Little is known about late Holocene relative sea-level (RSL) along the Gulf Coast of Florida. A RSL reconstruction from this region is needed to fill a spatial gap in sea-level records which can be used to support coastal management, contribute geologic data for Earth-Ice models estimating late Holocene land-level change and serve as the basis for which future projections of sea-level rise must be superimposed. Further, this dataset is crucial to understanding the presence/absence and non-synchronous timing of small sea-level oscillations (e.g. rise at ~ 1000 A.D.; fall at ~ 1400 A.D.) during the past 2000 years on the Atlantic and Gulf Coasts of the United States that may be linked to climate anomalies. We present the results of a high-resolution RSL reconstruction based on the sediment record of two salt marshes on the eastern margin of the Gulf of Mexico. Two ~1.3m cores primarily composed of Juncus roemeranius peat reveal RSL changes over the past ~2000 years in the southern end of Tampa Bay and in Charlotte Harbor, Florida. Two study sites were used to isolate localized factors affecting RSL at either location. Lithostratigraphic analysis at both sites identifies a transition from sandy-silt layers into salt-marsh peat at the bottom of each core. The two records show continuous accumulation of salt-marsh peat with Juncus roemeranius macrofossils and intermittent sand horizons likely reflecting inundation events. We used vertically zoned assemblages of modern foraminifera to assign the indicative meaning. The high marsh is dominated by Ammoastuta inepta, Haplophragmoides wilberti, and Arenoparella mexicana, with low marsh and tidal flats identified by Ammobaculites spp. and Miliammina fusca. Chronologies for these study sites were established using AMS radiocarbon dating of in-situ plant macrofossils, Cs137, Pb210 and pollen and pollution chronohorizons. Our regional RSL curve will add additional data for constraining the mechanisms causing RSL change.

  6. The Anthropocene is functionally and stratigraphically distinct from the Holocene.

    PubMed

    Waters, Colin N; Zalasiewicz, Jan; Summerhayes, Colin; Barnosky, Anthony D; Poirier, Clément; Gałuszka, Agnieszka; Cearreta, Alejandro; Edgeworth, Matt; Ellis, Erle C; Ellis, Michael; Jeandel, Catherine; Leinfelder, Reinhold; McNeill, J R; Richter, Daniel deB; Steffen, Will; Syvitski, James; Vidas, Davor; Wagreich, Michael; Williams, Mark; Zhisheng, An; Grinevald, Jacques; Odada, Eric; Oreskes, Naomi; Wolfe, Alexander P

    2016-01-08

    Human activity is leaving a pervasive and persistent signature on Earth. Vigorous debate continues about whether this warrants recognition as a new geologic time unit known as the Anthropocene. We review anthropogenic markers of functional changes in the Earth system through the stratigraphic record. The appearance of manufactured materials in sediments, including aluminum, plastics, and concrete, coincides with global spikes in fallout radionuclides and particulates from fossil fuel combustion. Carbon, nitrogen, and phosphorus cycles have been substantially modified over the past century. Rates of sea-level rise and the extent of human perturbation of the climate system exceed Late Holocene changes. Biotic changes include species invasions worldwide and accelerating rates of extinction. These combined signals render the Anthropocene stratigraphically distinct from the Holocene and earlier epochs.

  7. 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.

  8. A lacustrine carbonate record of Holocene seasonality and climate

    USGS Publications Warehouse

    Wittkop, Chad A.; Teranes, Jane L.; Dean, Walter E.; Guilderson, Thomas P.

    2009-01-01

    Annually laminated (varved) Holocene sediments from Derby Lake, Michigan, display variations in endogenic calcite abundance reflecting a long-(millennial-scale) decrease in burial punctuated with frequent short- (decadal-scale) oscillations due to carbonate dissolution. Since 6000 cal yr B.P., sediment carbonate abundance has followed a decreasing trend while organic-carbon abundance has increased. The correlation between organic-carbon abundance and the sum of March-April-October-November insolation has an r2 value of 0.58. We interpret these trends to represent a precession-driven lengthening of the Holocene growing season that has reduced calcite burial by enhancing net annual organic-matter production and associated calcite dissolution. Correlations with regional paleoclimate records suggest that changes in temperature and moisture balance have impacted the distribution of short- oscillations in carbonate and organic-matter abundance superimposed on the precession-driven trends.

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

    USGS Publications Warehouse

    Chumbley, C.A.; Baker, R.G.; Bettis, E. Arthur

    1990-01-01

    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 provide 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.

  10. The variability of the North Atlantic Oscillation throughout the Holocene

    NASA Astrophysics Data System (ADS)

    Wassenburg, Jasper; Dietrich, Stephan; Fietzke, Jan; Fohlmeister, Jens; Wei, Wei; Jochum, Klaus Peter; Scholz, Denis; Richter, Detlev; Sabaoui, Abdellah; Lohmann, Gerrit; Andreae, Meinrat; Immenhauser, Adrian

    2013-04-01

    The North Atlantic Oscillation (NAO) has a major impact on Northern Hemisphere winter climate. Trouet et al. (2009) reconstructed the NAO for the last millennium based on a Moroccan tree ring PDSI (Palmer Drought Severity Index) reconstruction and a Scottish speleothem record. More recently, Olsen et al. (2012) extended the NAO record back to 5.2 ka BP based on a lake record from West Greenland. It is, however, well known that the NAO exhibits non-stationary behavior and the use of a single location for a NAO reconstruction may not capture the complete variability. In addition, the imprint of the NAO on European rainfall patterns in the Early and Mid Holocene on (multi-) centennial timescales is still largely unknown. This is related to difficulties in establishing robust correlations between different proxy records and the fact that proxies may not only reflect winter conditions (i.e., the season when the NAO has the largest influence). Here we present a precisely dated, high resolution speleothem δ18O record from NW Morocco covering the complete Early and Mid Holocene. Carbon and oxygen isotopes were measured at a resolution of 15 years. A multi-proxy approach provides solid evidence that speleothem δ18O values reflect changes in past rainfall intensity. The Moroccan record shows a significant correlation with a speleothem rainfall record from western Germany, which covers the entire Holocene (Fohlmeister et al., 2012). The combination with the extended speleothem record from Scotland, speleothem records from north Italy and the NAO reconstruction from West Greenland (Olsen et al., 2012) allows us to study the variability of the NAO during the entire Holocene. The relation between West German and Northwest Moroccan rainfall has not been stationary, which is evident from the changing signs of correlation. The Early Holocene is characterized by a positive correlation, which changes between 9 and 8 ka BP into a negative correlation. Simulations with the state

  11. Origin and deformation of Holocene shoreline terraces, Yellowstone Lake, Wyoming

    SciTech Connect

    Meyer, G.A.; Locke, W.W.

    1986-08-01

    Geodetic surveys within the Yellowstone caldera have documented active uplift that is most likely caused by magmatic processes in the upper crust. Along the northeast shore of Yellowstone Lake, maximum relative uplift rates are 10 mm/yr for the period 1923-1975. However, information on deformation prior to historic instrumental records has been lacking. In this study, closely spaced data on elevations of postglacial shoreline terraces around the north end of Yellowstone Lake reveal complex tilting. Though most Holocene deformation is probably magma related, the pattern of shoreline tilting deviates significantly from the historic pattern of roughly symmetric inflation of the caldera. Along the northeast shore, where tilt directions of historic and shoreline deformation are similar, differential uplift of a > 2500-yr-old terrace is roughly 10 m; this gives a maximum uplift rate of 4 mm/yr. These unique Holocene terraces may exist due to episodic deformation because vertical movements affecting the lake outlet directly control lake level.

  12. Early Holocene Vegetation Record from the Salton Basin, California

    NASA Astrophysics Data System (ADS)

    Rinehart, Roberta B.; McFarlane, Donald A.

    1995-03-01

    Plant and vertebrate macrofossils in an early Holocene fossil packrat ( Neotoma sp.) midden with a radiocarbon age of 8640 ± 100 14 C yr B.P. are reported from the Chocolate Mountains, near the Salton Sea, Riverside County, California. An inventory of the midden has permitted a comparison of the modern flora and fauna of the site with that extant during the early Holocene. Whereas the biota had assumed most aspects of its modern Sonoran desert aspect by this date, statistically significant evidence of differences is attributed to an increased flow of surface water in Salt Creek, a high-standing, low-salinity Lake LeConte, and the late arrival of some characteristic Sonoran desert plants. These observations are consistent with models of significant fall-winter precipitation in the Sonoran Desert, although we cannot exclude alternative explanations.

  13. Holocene eruptive activity of El Chichon volcano, Chiapas, Mexico

    NASA Technical Reports Server (NTRS)

    Tilling, R. I.; Rubin, M.; Sigurdsson, H.; Carey, S.; Duffield, W. A.; Rose, W. I.

    1984-01-01

    Geologic and radiometric-age data indicate that El Chichon was frequently and violently active during the Holocene, including eruptive episodes about 600, 1250, and 1700 years ago and several undated, older eruptions. These episodes, involving explosive eruptions of sulfur-rich magma and associated domegrowth processes, were apparently separated by intervals of approximately 350 to 650 years. Some of El Chichon's eruptions may correlate with unusual atmospheric phenomena around A.D. 1300 and possibly A.D. 623.

  14. Wasatch fault zone, Utah - segmentation and history of Holocene earthquakes

    USGS Publications Warehouse

    Machette, Michael N.; Personius, Stephen F.; Nelson, Alan R.; Schwartz, David P.; Lund, William R.

    1991-01-01

    The Wasatch fault zone (WFZ) forms the eastern boundary of the Basin and Range province and is the longest continuous, active normal fault (343 km) in the United States. It underlies an urban corridor of 1.6 million people (80% of Utah's population) representing the largest earthquake risk in the interior of the western United States. The authors have used paleoseismological data to identify 10 discrete segments of the WFZ. Five are active, medial segments with Holocene slip rates of 1-2 mm a-1, recurrence intervals of 2000-4000 years and average lengths of about 50 km. Five are less active, distal segments with mostly pre-Holocene surface ruptures, late Quaternary slip rates of <0.5 mm a-1, recurrence intervals of ???10,000 years and average lengths of about 20 km. Surface-faulting events on each of the medial segments of the WFZ formed 2-4-m-high scarps repeatedly during the Holocene. Paleoseismological records for the past 6000 years indicate that a major surface-rupturing earthquake has occurred along one of the medial segments about every 395 ?? 60 years. However, between about 400 and 1500 years ago, the WFZ experienced six major surface-rupturing events, an average of one event every 220 years, or about twice as often as expected from the 6000-year record. Evidence has been found that surface-rupturing events occurred on the WFZ during the past 400 years, a time period which is twice the average intracluster recurrence interval and equal to the average Holocene recurrence interval.

  15. The Acridian plagues, a new Holocene and Pleistocene palaeoclimatic indicator

    NASA Astrophysics Data System (ADS)

    Meco, Joaquín; Petit-Maire, Nicole; Ballester, Javier; Betancort, Juan F.; Ramos, Antonio J. G.

    2010-07-01

    Five palaeosols, intercalated within the Quaternary dune beds of Fuerteventura and Lanzarote (Canary Islands), off the Moroccan coast, mark wetter climatic episodes. In all of them, billions of calcified insect ootheca testify to past occurrences of Acridian plagues, such as those reaching the western Sahara following heavy rainfall events over the Sahel. The most massive infestation is in the Holocene, and should coincide with the climax of Saharo-Sahelian humidity at the peak of the present interglacial.

  16. Holocene eruptive activity of El Chichon volcano, Chiapas, Mexico

    NASA Astrophysics Data System (ADS)

    Tilling, R. I.; Rubin, M.; Sigurdsson, H.; Carey, S.; Duffield, W. A.; Rose, W. I.

    1984-05-01

    Geologic and radiometric-age data indicate that El Chichon was frequently and violently active during the Holocene, including eruptive episodes about 600, 1250, and 1700 years ago and several undated, older eruptions. These episodes, involving explosive eruptions of sulfur-rich magma and associated domegrowth processes, were apparently separated by intervals of approximately 350 to 650 years. Some of El Chichon's eruptions may correlate with unusual atmospheric phenomena around A.D. 1300 and possibly A.D. 623.

  17. Holocene submergence of the Eastern Shore of Virginia

    USGS Publications Warehouse

    Newman, W.S.; Rusnak, G.A.

    1965-01-01

    Radiocarbon ages of basal peats 4500 years old or younger and the thickness of salt-marsh peat in the lagoon east of Wachapreague, Virginia, are nearly the same as those of equivalent samples from New Jersey and Cape Cod. This suggests that these coasts have had similar submergence histories. Data obtained from the coasts of Connecticut and northeastern Massachusetts indicate that the Atlantic coast of the United States has been differentially warped during the later Holocene.

  18. Holocene reef development where wave energy reduces accommodation

    USGS Publications Warehouse

    Grossman, Eric E.; Fletcher, Charles H.

    2004-01-01

    Analyses of 32 drill cores obtained from the windward reef of Kailua Bay, Oahu, Hawaii, indicate that high wave energy significantly reduced accommodation space for reef development in the Holocene and produced variable architecture because of the combined influence of sea-level history and wave exposure over a complex antecedent topography. A paleostream valley within the late Pleistocene insular limestone shelf provided accommodation space for more than 11 m of vertical accretion since sea level flooded the bay 8000 yr BP. Virtually no net accretion (pile-up of fore-reef-derived rubble (rudstone) and sparse bindstone, and (3) a final stage of catch-up bindstone accretion in depths > 6 m. Coral framestone accreted at rates of 2.5-6.0 mm/yr in water depths > 11 m during the early Holocene; it abruptly terminated at ~4500 yr BP because of wave scour as sea level stabilized. More than 4 m of rudstone derived from the upper fore reef accreted at depths of 6 to 13 m below sea level between 4000 and 1500 yr BP coincident with late Holocene relative sea-level fall. Variations in the thickness, composition, and age of these reef facies across spatial scales of 10-1000 m within Kailua Bay illustrate the importance of antecedent topography and wave-related stress in reducing accommodation space for reef development set by sea level. Although accommodation space of 6 to 17 m has existed through most of the Holocene, the Kailua reef has been unable to catch up to sea level because of persistent high wave stress.

  19. Biotic turnover rates during the Pleistocene-Holocene transition

    NASA Astrophysics Data System (ADS)

    Stivrins, Normunds; Soininen, Janne; Amon, Leeli; Fontana, Sonia L.; Gryguc, Gražyna; Heikkilä, Maija; Heiri, Oliver; Kisielienė, Dalia; Reitalu, Triin; Stančikaitė, Miglė; Veski, Siim; Seppä, Heikki

    2016-11-01

    The Northern Hemisphere is currently warming at the rate which is unprecedented during the Holocene. Quantitative palaeoclimatic records show that the most recent time in the geological history with comparable warming rates was during the Pleistocene-Holocene transition (PHT) about 14,000 to 11,000 years ago. To better understand the biotic response to rapid temperature change, we explore the community turnover rates during the PHT by focusing on the Baltic region in the southeastern sector of the Scandinavian Ice Sheet, where an exceptionally dense network on microfossil and macrofossil data that reflect the biotic community history are available. We further use a composite chironomid-based summer temperature reconstruction compiled specifically for our study region to calculate the rate of temperature change during the PHT. The fastest biotic turnover in the terrestrial and aquatic communities occurred during the Younger Dryas-Holocene shift at 11,700 years ago. This general shift in species composition was accompanied by regional extinctions, including disappearance of mammoth (Mammuthus primigenius) and reindeer (Rangifer tarandus) and many arctic-alpine plant taxa, such as Dryas octopetala, Salix polaris and Saxifraga aizoides, from the region. This rapid biotic turnover rate occurred when the rate of warming was 0.17 °C/decade, thus slightly lower than the current Northern Hemisphere warming of 0.2 °C/decade. We therefore conclude that the Younger Dryas-Holocene shift with its rapid turnover rates and associated regional extinctions represents an important palaeoanalogue to the current high latitude warming and gives insights about the probable future turnover rates and patterns of the terrestrial and aquatic ecosystem change.

  20. Holocene climate changes in the Cape Hatteras region

    NASA Astrophysics Data System (ADS)

    Naughton, F.; Keigwin, L. D.; Peteet, D. M.; Desprat, S.; Oliveira, D.; Abrantes, F.

    2013-12-01

    In the last century many studies have been done in various naturally occurring archives to understand the nature, timing and causes of Holocene natural climate oscillations. Most of the available Holocene climatic reconstructions are however, not based on a direct comparison of terrestrial, marine and ice records making it difficult to obtain an accurate understanding of the interactions of the atmosphere-ocean-land systems and their relationship in global climate variability. Few studies based on direct sea land comparison have been reported for some key areas of the eastern North Atlantic but almost none in the western North Atlantic. Here we present a direct comparison between terrestrial (pollen) and marine (planktonic δ18O) proxies from a well dated (ten AMS 14C dates on planktonic foraminifera and seaweed) slope core (KNR 178-2 JPC 32), retrieved close to Cape Hatteras (35°58.58'N, 74°42.77'W, 1006 m). This study provides information on eastern North America vegetation and on the northwestern Atlantic sea surface response to both Holocene long-term and rapid climate changes. Five intervals, marked mainly by changes in temperate trees are associated with long term climate shifts (12000-9150 ka; 9150-7250 ka; 7250-5350 ka; 5350-2800 ka; 2800-700 ka). Over these intervals, several abrupt cooling events are noted, as well as several indications of shifts in moisture. The comparison of our data with those available and unpublished records from several key sites of the North Atlantic region, gives insights into the nature, timing and causes of Holocene climate oscillations in the North Atlantic region and in particular off Cape Hatteras.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  2. Coastal Surveillance Baseline Model Development

    DTIC Science & Technology

    2015-02-27

    reconnaissance (ISR) model for coastal surveillance. The model needs to be developed in the System Toolkit (STK) software package version 10.0 (or...reconnaissance (ISR) model for coastal surveillance. The model needs to be developed in the System Toolkit (STK) software package version 10.0 (or...Catalogue STK System Toolkit TA Technical Authority DRDC CORA Task #185 Coastal Surveillance Baseline Model Development 27 February 2015 F-1 5758-001

  3. An introduction to coastal geomorphology

    SciTech Connect

    Pethick, J.S.

    1984-01-01

    This book is an introduction to wave and tidally dominated coastal forms, including beaches, cliffs, dunes, estuaries, mudflats and marshlands. The book emphasises the physical mechanisms by which this variety of landforms is produced and maintained. It introduces the energy outputs - waves, currents, tides - into the coastal 'machine', examines the way in which this energy is converted into water and sediment movement, and leads to an account of coastal landform development.

  4. A Mid-Holocene sea level fluctuation in South Carolina

    SciTech Connect

    Gayes, P.T.; Nelson, D.D. . Marine and Wetland Studies); Scott, D.B.; Collins, E. . Centre for Marine Geology)

    1993-03-01

    A high stand of relative sea level occurred at 4.2 ka in Murrells Inlet on the northern coast of South Carolina. The event was identified using benthic foraminiferal zonations, marsh stratigraphic relations and radiocarbon data. This highstand reached a maximum of approximately [minus]1 meter MSD and was followed by a fall of 2 meters until 3.6 ka. Subsequent to 3.6 ka submergence was slow averaging 10 cm/century to the present. A second smaller fluctuation may have occurred around 2.5 ka but remains poorly constrained. Although a Mid-Holocene highstand had been suggested by others, it has not been well constrained. New data from North Inlet, South Carolina also record a baselevel change in the Mid-Holocene. Strong differential submergence between Murrells Inlet and Santee Delta, South Carolina, has occurred over the last 4 ka, probably as a result of sediment loading by and subsidence of, the Santee Delta. The occurrence of the 4.2 ka highstand corresponds in the range (7 [minus] 4 ka) to that of the Holocene Hypsithermal. The rate and magnitude of the relative sea level fluctuation are similar to those projected for future flooding and suggest that the evaluation of the Hypsithermal highstand may provide an insight to continued sea-level rise.

  5. Holocene evolution of the northeastern corner of the Nile Delta

    NASA Astrophysics Data System (ADS)

    Sneh, A.; Weissbrod, T.; Ehrlich, A.; Horowitz, A.; Moshkovitz, S.; Rosenfeld, A.

    1986-09-01

    The constructive phase of the modern Nile Delta, as manifested in a 48-m section drilled east of the Suez Canal, commenced in very early Holocene times. Sands rich in marine fauna were deposited in the littoral zone and the shoreline was more than 20 km landward of its present-day position. Subsequently, clays and silts were dumped from the Nile distributaries and the marine faunal spectrum became very limited and brackish. Later in early and middle Holocene times the sediments deposited were rich in freshwater, delta-plain diatoms and pollen and in allochthonous fern spores from the tropics, indicating proximity of a distributary mouth. The middle part of the section (22.5-17.5 m) is very poor in faunal and floral remains; pollen grains from sabkha vegetation are abundant. The environment, which seems lagoonal and slightly hypersaline, is related to the sea regression in middle Holocene times. Euryhaline pelecypods, dating from about 3000 yr B.P., are abundant around the 8-m depth. Upward, there is an increase in pollen grains from sabkhas; the section is poor in diatoms and those present are mostly euryhaline and lagoonal. Allochthonous spores derived from the nearby Pelusiac Branch are abundant. Between 3000 and 2000 yr B.P. the constructive phase of the modern delta terminated and winnowed sands began accreting in front of the delta plain.

  6. Regional aridity in North America during the middle Holocene

    USGS Publications Warehouse

    Dean, W.E.; Ahlbrandt, T.S.; Anderson, R.Y.; Bradbury, J.P.

    1996-01-01

    Increased aridity throughout the Great Plains and Rocky Mountain region during the middle Holocene has been documented from pollen records, aeolian proxy variables in lake cores, and active sand dune migration. Varve calibration provided by a continuously varved record of the Holocene from a core from Elk Lake, northwestern Minnesota, shows that the influx of aeolian elastic material increased beginning about 8 ka and ended about 3.8 ka, with peak aeolian activity at about 6 ka. If aeolian influx to Elk Lake corresponds in time to aeolian influx in other lakes and to maximum dune activity in Minnesota dune fields, then the varve calibration in Elk Lake provides precise time calibration of periods of peak aeolian activity in Minnesota. Palaeowind studies from the Minnesota dune fields show that the dominant wind direction when the dunes were active was from the northwest, the same as the dominant wind direction in dune fields throughout the Great Plains and Rocky Mountains. If the mid-Holocene aeolian activity in Minnesota was driven by an increase in westerly zonal winds, then the varve calibration can be extended to more precisely determine the timing of activity of dunes over a much broader area. We suggest that an increase in the westerly zonal wind field might have a solar-geomagnetic cause.

  7. Late Holocene sea-level change in Arctic Norway

    NASA Astrophysics Data System (ADS)

    Barnett, Robert L.; Gehrels, W. Roland; Charman, Dan J.; Saher, Margot H.; Marshall, William A.

    2015-01-01

    Relative sea-level data from the pre-industrial era are required for validating geophysical models of glacio-isostatic adjustment as well as for testing models used to make sea-level predictions based on future climate change scenarios. We present the first late Holocene (past ˜3300 years) relative sea-level reconstruction for northwestern Norway based on investigations in South Hinnøya in the Vesterålen - Lofoton archipelago. Sea-level changes are reconstructed from analyses of salt-marsh and estuarine sediments and the micro-organisms (foraminifera and testate amoebae) preserved within. The 'indicative meaning' of the microfauna is established from their modern distributions. Records are dated by radiocarbon, 201Pb, 137Cs and chemostratigraphical analyses. Our results show a continuous relative sea-level decline of 0.7-0.9 mm yr-1 for South Hinnøya during the late Holocene. The reconstruction extends the relative sea-level trend recorded by local tide gauge data which is only available for the past ˜25 years. Our reconstruction demonstrates that existing models of shoreline elevations and GIA overpredict sea-level positions during the late Holocene. We suggest that models might be adjusted in order to reconcile modelled and reconstructed sea-level changes and ultimately improve understanding of GIA in Fennoscandia.

  8. Solar driven climate changes recorded in Holocene alpine speleothems

    NASA Astrophysics Data System (ADS)

    Frisia, S.; Borsato, A.; Preto, N.; McDermott, F.

    2003-04-01

    Inter-annual variations in the growth rate of three annually laminated speleothems from Grotta di Ernesto, an alpine cave located at 1160 m a.s.l. in northern Italy, reveal significant periodicities at ca. 1/11 and 1/22 cycles/yr, related to changes in solar irradiance. Additional frequency components may be related to the influence of NAO/AO mode changes. In the late Holocene, reduced calcite deposition during historic minima of solar output is indicative of the influence of solar forcing on Alpine climate and environment. Annual growth laminae thickness, controlled by cave drip-water supersaturation with respect to calcite, primarily reflects changes in soil pCO_2 production modulated by incoming solar radiation. The preservation of high-frequency signals, and the rapid response of speleothem climate proxy series to changes in solar radiation, favor atmospheric amplification of solar variability, rather than mechanisms involving changes in oceanic circulation. In the early- to mid-Holocene, only the lower frequency components of solar variability are preserved. Periods of reduced calcite deposition roughly correspond to the ca. 10^3-yrs-scale cycles of North Atlantic drift-ice records. Lowest growth rates are recorded at about 3200 and 6800 years BP. If the lamina thickness-climate relationships assessed for the Recent (through present-day monitoring, and by correlation with 200 years of instrumental records) held also for the mid and early Holocene, these episodes were characterized by very cold winters and relatively dry summers.

  9. Glaciological reconstruction of Holocene ice margins in northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Birkel, S. D.; Osterberg, E. C.; Kelly, M. A.; Axford, Y.

    2014-12-01

    The past few decades of climate warming have brought overall margin retreat to the Greenland Ice Sheet. In order to place recent and projected changes in context, we are undertaking a collaborative field-modeling study that aims to reconstruct the Holocene history of ice-margin fluctuation near Thule (~76.5°N, 68.7°W), and also along the North Ice Cap (NIC) in the Nunatarssuaq region (~76.7°N, 67.4°W). Fieldwork reported by Kelly et al. (2013) reveals that ice in the study areas was less extensive than at present ca. 4700 (GIS) and ca. 880 (NIC) cal. years BP, presumably in response to a warmer climate. We are now exploring Holocene ice-climate coupling using the University of Maine Ice Sheet Model (UMISM). Our approach is to first test what imposed climate anomalies can afford steady state ice margins in accord with field data. A second test encompasses transient simulation of the Holocene, with climate boundary conditions supplied by existing paleo runs of the Community Climate System Model version 4 (CCSM4), and a climate forcing signal derived from Greenland ice cores. In both cases, the full ice sheet is simulated at 10 km resolution with nested domains at 0.5 km for the study areas. UMISM experiments are underway, and results will be reported at the meeting.

  10. A Holocene paleomagnetic record from Fish Lake, Oregon.

    NASA Astrophysics Data System (ADS)

    Ziegler, L. B.; Stoner, J. S.; Abbott, M. B.; Finkenbinder, M. S.; Hatfield, R. G.; Konyndyk, D.; Reilly, B.; Hillman, A. L.

    2014-12-01

    Paleo-geomagnetic observations provide fundamental models of the core and the geodynamo that cannot other- wise be obtained. Data and modeling studies are beginning to show that regions of concentrated magnetic flux (flux lobes) on the Core-Mantle boundary, those observed historically and others only hinted at from the short historical record, impose a structure on the geomagnetic field that may govern at least some components of geo- magnetic change. Accumulating evidence suggests that this structure reflects the influence of the lower mantle, yet this structure and the evolution of the geomagnetic field within it, even for the Holocene, are only beginning to be- come apparent. Comparison of specific, well-dated Holocene timeseries of PSV (sedimentary and archeomagnetic) inclination, declination, and paleointensity at key locations can provide intriguing insight when viewed through the lens of the known historical and assumed millennial flux lobes. A limiting factor for these studies is the uneven distribution of high quality data with independent chronologies, with Europe and the North Atlantic having better constrained data sets than North America. To begin to fill this data gap, we present initial results from an ongoing study of the paleomagnetic record from Fish Lake, Oregon. Initial evaluation of directions and intensity along with the construction of an independent chronology allow us to assess and build upon prior results to constrain the evolution of the North American flux lobe and refine our understanding of paleo-geomagnetic change during the Holocene.

  11. The Nile Delta: climate pacing and vulnerability to Holocene change

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Deltas are potentially important sentinels to investigate climate-driven changes in palaeohydrology and human impacts, but, paradoxically, have often been overlooked as palaeoclimate records. In this paper, we present two time-series from the Nile Delta to probe both millennial and centennial-scale changes in deltaic hydrogeomorphology over the past 8000 years. 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. Using a second record we suggest that, at shorter timescales, many of the major phases of deltaic modification were mediated by climate events linked to El Niño Southern Oscillation- type (ENSO) variability. In the final part of the paper, we propose that following the early to mid-Holocene growth of the Nile's deltaic plain pronounced deltaic erosion is first recorded after ~4000 years ago, the corollaries of falling sediment supply and an intensification of anthropogenic impacts from the Pharaonic period onwards. The 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.

  12. 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.

  13. Biomarker records of Holocene climate variations in Asian interior

    NASA Astrophysics Data System (ADS)

    Song, M.; Liu, Z.; Liu, W.; Zhao, C.; Li, S.; He, Y.

    2012-12-01

    Understanding Holocene climate fluctuation may provide clues to projection of future climate change. Lake sediments in the arid central Asia (ACA), as an archive of past climate information, keep attracting considerable interest. We have retrieved several sediment cores from Lake Manas, an endorheic lake in Zunggar desert, Xinjiang Province, China. Biomarker proxies including alkenone Uk'37, %C37:4 and C37 concentration (C37 Conc), and physical proxies including density and magnetic susceptibility (MS) have been analyzed. We have found substantial climatic and environmental changes during the late Holocene. Density, MS and Uk'37 values are high during Medieval Warm Period (MWP) and C37 Conc is very low. During the Little Ice Age, density and MS decrease, Uk'37 values drop to near 0.1, C37 Conc is increased by 2 to 3 magnitude. Thus, warm and dry conditions dominated MWP while cold and wet conditions dominated LIA, a typical "Westerly" pattern which is opposite to the hydrological variation in Asian monsoonal regions. Biomarker records' correlation with solar irradiance (SI), the North Atlantic Oscillation (NAO), the 1000year ACA Moisture Index (ACAM), and the North Hemisphere Temperature (NHT) suggests SI as one of the forcing factor on temperature fluctuation and cold and wet LIA possibly resulting from westerly-jet shift, negative NAO oscillation and the lower evaporation induced by the decrease of temperature. Biomarker records for the whole Holocene will be also presented.

  14. Mechanisms, Rates, and Patterns of Shallow Subsidence in Coastal Louisiana

    NASA Astrophysics Data System (ADS)

    Tornqvist, T. E.; Jankowski, K. L.

    2014-12-01

    It is increasingly clear that the exceptionally high land-surface subsidence rates in coastal Louisiana (as inferred, among others, from tide-gauge records) are primarily due to processes that operate in the uppermost tens of meters of the subsurface. Considerable efforts are needed to better quantify these processes in terms of their rates and spatial patterns. Only then the predictive models can be developed that so far have remained elusive. Here we present shallow stratigraphic data, demonstrating that compaction within the Holocene column can explain a large portion of the subsidence that is observed at the land surface. Loading of water-rich deltaic strata with clastic sediment is an effective mechanism to drive subsidence rates up to at least 5 mm/yr that can persist for centuries if not longer. While stratigraphic studies offer detailed insights in the dominant processes, they have less potential to determine present-day subsidence rates and to predict future subsidence rates and their spatial patterns. The Coastwide Reference Monitoring System (CRMS), a major effort initiated by the US Geological Survey to monitor Louisiana's coastal wetlands, offers unique new opportunities to study shallow subsidence on sub-decadal timescales. All of the ~400 CRMS sites include a rod-surface elevation table combined with marker horizons, resulting in detailed records of surface-elevation change and vertical accretion rates. Here we use these data to determine rates of shallow (<45 m) subsidence throughout coastal Louisiana over the past 5-7 years, primarily due to sediment compaction. For the 226 sites with at least 5 years of observation, the range of shallow subsidence rates varies by several tens of mm/yr. Statistical analysis of the relationship between shallow subsidence and other wetland characteristics (e.g., organic matter content, salinity) helps to elucidate the spatial patterns of modern subsidence, with the ultimate objective to improve subsidence predictions.

  15. Neotectonics of coastal Jeffara (southern Tunisia): State of the art

    NASA Astrophysics Data System (ADS)

    Ghedhoui, Rim; Deffontaines, Benoît; Rabia, Mohamed Chedly

    2016-04-01

    Helped by the studies and results of previous researchers, we herein study the neotectonic of the coastal Jeffara with the input of numerous 2D reflection seismic profiles onshore, combined with Digital Elevation Model analyses (issued from SRTM) and field works. Acquired and available data were then integrated within a GIS Geodatabase, where Jerba, Zarzis and Jorf appear to be part of a N-S pull-apart basin within a NW-SE transtensive right-lateral major fault zone. Our structural geologic and geomorphologic analyses confirm and prove the presence of NNW-SSE right-lateral en-echelon tension gashes, NW-SE aligned salt diapirs, numerous active folds offsets, en-echelon folds, and so-on… They are associated with this major right-lateral NW-SE transtensive major coastal Jeffara fault zone that affect the Holocene and the Villafranchian deposits. We therefore confirm herein a new structural geodynamic Jeffara model, due to the post Lower Cretaceous northward migration of northern African to the Eurasian plates, this NW-SE transtensive fault zone is interpreted as a part of the southern branch of the eastward Sahel block extrusion toward the free Mediterranean Sea boundary. Therefore this geodynamic movement may explain the presence, offshore, of small elongated NW-SE, N-S and NE-SW transtensive basins and grabens with petroleum interest. To conclude, at the regional scale, the structural geomorphologic approach combined with both field work and 2D reflection seismic profile analyses appear to be an excellent tool to prove and confirm the NW-SE right-lateral transtensive extrusion fault zone of the coastal Jeffara.

  16. Sedimentology of coastal chevron deposits - tsunamigenic versus aeolian origin

    NASA Astrophysics Data System (ADS)

    Garcia Garcia, A.; Spiske, M.; Tsukamoto, S.; Schmidt, V.

    2012-12-01

    The genesis of v-shaped coastal chevrons is currently controversially discussed. So far, chevrons are only described regarding their morphology, but not in terms of their origin. Two possible origins of chevrons are proposed: both aeolian transport and tsunami inundation are discussed as depositing processes. We present initial results of a detailed sedimentological survey of Holocene coastal chevrons from the American and Australian west coasts. The chevrons were measured and levelled using a differential GPS system. Large scale internal structures were recorded by ground penetrating radar imaging. Trenches were dug for sampling and analyzing small scale internal structures. The sediment samples were used for the analysis of grain-size distributions, mineral composition and content of marine microorganisms. Additional samples were taken for optically stimulated luminescence (OSL) and radiocarbon dating. Furthermore, we took reference samples from beaches, cliffs and rivers, which could act as potential sediment sources for the surveyed chevrons. Tsunami deposits are commonly polymodal, exhibit a grain-size decrease and tend to show better sorting in landward direction. Such trends are not present in the surveyed chevrons. Most samples are well to moderately well sorted and unimodal. The OSL ages decrease in transport direction and indicate a long term generation process, such as dune migration, rather than a short term event like a tsunami. This fact is additionally underlined by land snails found in different stratigraphic levels within the Australian chevrons. Furthermore, the occurrence of intercalated soil horizons implies a change of stable and active migration phases. The initial results of this study point out to an aoelian origin of coastal chevrons and do not support the previously supposed thesis of a tsunamigenic origin.

  17. Late Pleistocene raised beaches of coastal Estremadura, central Portugal

    NASA Astrophysics Data System (ADS)

    Benedetti, Michael M.; Haws, Jonathan A.; Funk, Caroline L.; Daniels, J. Michael; Hesp, Patrick A.; Bicho, Nuno F.; Minckley, Thomas A.; Ellwood, Brooks B.; Forman, Steven L.

    2009-12-01

    We present new stratigraphic, sedimentological, and chronological data for a suite of tectonically raised beaches dating to Marine Isotope Stages 5, 4, and 3 along the Estremadura coast of west-central Portugal. The beach deposits are found in association with ancient tidal channels and coastal dunes, pollen bearing mud and peat, and Middle Paleolithic archaeological sites that confirm occupation of the coastal zone by Neanderthal populations. The significance of these deposits is discussed in terms of the archaeological record, the tectonic and geomorphic evolution of the coast, and correlation with reconstructions of global climate and eustatic sea-level change. Direct correlation between the Estremadura beach sections is complicated by the tectonic complexity of the area and the age of the beach deposits (which are near or beyond the limit of radiocarbon dating). Evidence from multiple sites dated by AMS radiocarbon and optical luminescence methods suggests broad synchroneity in relative sea-level changes along this coast during Marine Isotope Stage 3. Two beach complexes with luminescence and radiocarbon age control date to about 35 ka and 42 ka, recording a rise in relative sea level around the time of Heinrich Event 4 at 39 ka. Depending on assumptions about eustatic sea level at the time they were deposited, we estimate that these beaches have been uplifted at rates of 0.4-4.3 mm yr -1 by the combined effects of tectonic, halokinetic, and isostatic processes. Uplift rates of 1-2 mm yr -1 are likely if the beaches represent sea level stands at roughly 40 m below modern, as suggested by recent eustatic sea level reconstructions. Evidence from coastal bluffs and the interior of the study area indicates extensive colluvial, fluvial, and aeolian sedimentation beginning around 31 ka and continuing into the Holocene. These geomorphic adjustments are related to concomitant changes in climate and sea level, providing context that improves our understanding of Late

  18. A Comparison of 20th Century and Holocene Historical Lake Areas and Implications for Reconstruction of Holocene Moisture Balance.

    NASA Astrophysics Data System (ADS)

    Plank, C. P.; Ferreira, M.; Shuman, B.; Ito, E.

    2005-12-01

    Low lake stands during the Holocene document a period of drier than modern conditions in the upper Midwest after 8000 cal yr B.P. Here, we seek to compare the magnitudes and spatial extent of these mid-Holocene water-level changes with the changes that occurred during the 1930s Dust Bowl drought. The comparison allows us to consider the potential range of hydrologic conditions in the mid-continent, and to detect similarities or differences between the two periods as a way to learn more about the climatic controls on the mid-Holocene moisture-balance. (How good an analog is the 1930s drought for the mid-Holocene aridity?) Each lake record, however, is unique and comparisons among lakes have been hindered by local hydrologic influences and sedimentary processes. We therefore test the simple methodological assumption that the stratigraphic records of small lakes may be used in concert to produce valid and meaningful maps of Holocene moisture balance. First we confirm that broad regional trends in lake area reflect long-term moisture balance patterns by studying the 1930s aerial photography. Second, we confirm that regionally coherent patterns of sedimentary change related to past water levels can be detected for the mid-Holocene via GPR profiles. Changes in open water surface area in response to the 1930's drought are quantified and mapped for over 300 small (1km sq. or less) lakes of northern and central Minnesota in order to determine if small basins responded to drought with explainable regional coherency. A map of percent area change (between AD 1930 and 2003) reveals that coherent trends in surface area response reflect the gradient of moisture balance change over the same period. We found a trend in percent surface area change from east to west with western lakes completely drying out (>100% change), a wider variability of responses in central Minnesota, and eastern lakes undergoing almost no change (<10%). GPR profiles were collected on two east-west transects

  19. Recording of the Holocene sediment infilling in a confined tide-dominated estuary: the bay of Brest (Britanny, France)

    NASA Astrophysics Data System (ADS)

    Gregoire, Gwendoline; Le Roy, Pascal; Ehrhold, Axel; Jouet, Gwenael; Garlan, Thierry

    2016-04-01

    Modern estuaries constitute key areas for the preservation of sedimentary deposits related to the Holocene period. Several previous studies using stratigraphic reconstructions in such environments allowed to characterise the major parameters controlling the Holocene transgressive sequence and to decipher their respective role in the sedimentary infill: (1) the evolution of main hydrologic factors (wave or tide-dominated environment), (2) the sea level fluctuation and (3) the morphologies of the bedrock and the coastline. Nevertheless, the timing of the transgressive deposits and the detailed facies need to be precise in regard to the stratigraphic schemes. The Bay of Brest (Western Brittany, France) offers the opportunity to examine these points and to compare with previous studies. It constitutes an original tide-dominated estuary that communicates to the open sea (Iroise Sea) by a narrow strait. Two main rivers (Aulne and Elorn) are connected to a submerged paleovalleys network that was incised in the Paleozoic basement during lowstands and still preserved in the present morphology. It delineates the central basin surrounded by tidal flat located in sheltered area. The analysis of high and very-high resolution seismic lines recorded through the whole bay combined with sediment cores (up to 4.5 m long) and radiocarbon dating allow to precise the architecture and the timing of the thick Holocene coastal wedge. It is preserved from the valley network to the shore and presents a longitudinal variability (downstream-upstream evolution). The infill is divided into two successive stages (corresponding to the transgressive and highstand system tracts) which laterally evolve from the paleo-valley to the coast. Two units constitute the transgressive system tract. The oldest, dated from 8200 to 7000 cal B.P. is composed of fine-grained, organic-rich tidal flat deposits located in the sheltered area and organised in levees on the terrace bordering the paleo-valley. A tidal

  20. A NATIONAL COASTAL ASSESSMENT OF COASTAL SEDIMENT CONDITION

    EPA Science Inventory

    One element of the Environmental Monitoring and Assessment Program's National Coastal Assessment is to estimate the current status, extent, changes and trends in the condition of the Nation's coastal sediments on a national basis. Based on NCA monitoring activities from 1999-2001...

  1. Holocene stream aggradation and degradation, Pajarito Plateau, northern New Mexico

    SciTech Connect

    Reneau, S.L.; Gardner, J.N. ); Kelson, K.I. ); Hemphill-Haley, M.A. )

    1993-04-01

    Radiocarbon dates obtained from three canyons on the Pajarito Plateau, northern NM document alternating periods of Holocene stream aggradation and degradation that are, at least in part, synchronous between canyons. Four or more Holocene terraces are present in Frijoles Canyon, which has been rapidly incising into easily eroded, non-welded 1.1 Ma Bandelier Tuff. The oldest of these is an extensive fill terrace that is underlain by up to 13 m of stream gravels. This fill terrace records the most significant period of Holocene aggradation in Frijoles Canyon, and a date of 6.2 ka from basal slopewash burying the stream sediments provides a minimum-limiting age for this terrace. After 6.2 ka, temporary pauses in channel incision are recorded by strath terraces dated at ca. 4.6 and 1.6 ka, and an intermediate undated strath terrace. Age data obtained from Rendija and Cabra Canyons, 13 km to the north, indicate periods of stream aggradation similar in age to those in Frijoles Canyon. A minimum of two Holocene terraces are present in Rendija Canyon, and dates of 6.1--6.3 ka from stream sediments beneath the higher terrace and from overlying slopewash correlate it with the major fill terrace in Frijoles Canyon. In Cabra Canyon the unchanneled valley floor is underlain by more than 7 m of unconsolidated sediments, and four or more unconformable sedimentary packages were exposed in a 4-m deep trench. The lowest exposed Holocene sediments yielded an age of ca. 5.7 ka, and three overlying units that back-fill paleo-channels yielded ages of 3.5--3.8, 1.6, and 0.3 ka. In all three canyons the modern floodplains are aggrading, and radiocarbon dates of 0--0.4 ka from the uppermost sediments of the valley floors suggest these streams have been near present level for several hundred years. The similar ages obtained from stream deposits in Pajarito Plateau drainages suggest a climatic control for at least some of the aggradation events.

  2. A Holocene speleothem record from Morocco, NW Africa

    NASA Astrophysics Data System (ADS)

    Wassenburg, Jasper; Fietzke, Jan; Richter, Detlev; Immenhauser, Adrian

    2010-05-01

    A well dated Holocene speleothem (stalagmite) from the Middle Atlas Mountains in Morocco has been investigated for its continental climate record. The aim is to compile an improved understanding of the climatically complex triple point of the North Atlantic, Mediterranean and Saharan / Monsoonal climate realms in NW Africa. At present, only few studies concerning continental climate reconstructions from NW Africa have been published (Lamb et al. 1995, Cheddadi et al. 1998, Genty et al. 2006). Given the significance of this region, this lack of data forms a strong motivation for additional, well dated climate records. The speleothem (GP2) was sampled in the 'Grotte de Piste' (ca 800 m above sea level), mean annual precipitation is about 930 mm (mainly falling in the winter season) and the mean annual temperature is about 13° C. GP2 is 60 cm tall and grew - based on U/Th MC-ICP-MS data - continuously between 11.5 kyr BP (early Holocene) and 2.9 kyr BP (late Holocene). X-Ray Diffraction data indicate a mainly aragonitic mineralogy. 'Hendy tests' suggest that CaCO3 precipitation was close to isotopic equilibrium with respect to oxygen isotopes, however kinetic effects might have influenced carbon isotopes. Carbon and oxygen isotope data have been measured along a transect with increments of approximately 1 mm representing a resolution of about 15 yrs. Highly covariant oscillations in δ13C and δ18O with an average cyclicity of about 410 yrs. are observed. These oscillations coincide with macroscopically visible high density and low density layers, possibly reflecting a higher or lower amount of inclusions and perhaps higher and lower growth rates. Geochemical analysis of speloan aragonite is accompanied by cave monitoring that has started in November 2009. Parameters quantified include: drip water parameters, cave air humidity, pCO2 and cave air temperature. Precipitation experiments using watch glasses will also be performed. References Cheddadi, R., Lamb, H. F

  3. Planetary Hypothesis, sub-Milankovitch frequencies and Holocene cold events

    NASA Astrophysics Data System (ADS)

    Compagnucci, R. H.; Cionco, R. G.; Agosta, E.; Wanner, H.

    2013-05-01

    The Planetary Hypothesis of solar cycles proposes that the movement of the Sun around the solar system barycenter modulates the solar cycles at several times scales. Using a 3-D model of the solar system (Cionco and Compagnucci, 2012) we derived the solar barycentric motion and various dynamic parameters such as the angular momentum (L= Lx, Ly, Lz) for the Holocene. Angular momentum inversions are sporadic and important events in the dynamics of the MSB: Lz becomes negative and giant planets are nearly aligned. These episodes are related to some grand solar grand minima such as Maunder and Dalton, and also to the recent deep minimum 2007-2010 which was preceded by a Lz inversion in 1990. During the Holocene several negative Lz episodes occur that are grouped in approximately millennia to centuries long periods. Each group is separated by ~2000 years where the Lz values remain positive, both generating a cycle between 1500 and 2500 years. The spectral analysis shows significant peaks at sub-Milankovitch frequencies. Furthermore, the analysis of the spatiotemporal variability of temperature defined six specific cold events (8200, 6300, 4700, 2700, 1550 and 550 years BP) during the Holocene (Wanner et al, 2011). During, and /or before, of these major climates cooling, a group of negative Lz episodes were presented. Oppositely the resulted during the warms periods were the lack of the angular movement inversion together with the extremes of positive Lz . Therefore, the origin of Holocene cold events seems to be linked to the gravitational influence of the planets, that is to say the planetary torque that has a non-negligible effect on the causes of the solar magnetic cycle. Acknowledgements:The support of the Grants PID-UTN1351, UBACYT N_:20020100101049, CONICET PIP PIP 114-201001-00250 and MINCYT-MEYS ARC/11/09. References Cionco, R.G.; Compagnucci,R.H. (2012) Dynamical characterization of the last prolonged solar minima , Advances in Space Research 50(10), 1434

  4. North Siberian Permafrost reveals Holocene Arctic Winter Warming

    NASA Astrophysics Data System (ADS)

    Meyer, H.; Opel, T.; Laepple, T.; Alexander, D.; Hoffmann, K.; Werner, M.

    2014-12-01

    The Arctic climate has experienced a major warming over the past decades, which is unprecedented in the last 2000 yrs. There are, however, still major uncertainties about the temperature evolution during the Holocene. Most proxy reconstructions suggest a cooling in mid-and late Holocene (e.g. Wanner, 2008), whereas climate model simulations show only weak changes or even a moderate warming (e.g. Lohmann et al., 2013). In this study, we used ice wedges as promising permafrost climate archive studied by stable water isotope methods. Ice wedges may be identified by vertically oriented foliations, and they form by the repeated filling of winter thermal contraction cracks by snow melt water in spring. Therefore, the isotopic composition of wedge ice may be attributed to the climate conditions of the cold season (i.e. winter and spring). 42 samples of organic material enclosed in ice wedges have been directly dated by Radiocarbon methods. Here, we present the first terrestrial stable oxygen isotope record of Holocene winter temperatures in up to centennial-scale resolution based on permafrost ice wedges (Lena River Delta; Siberian Arctic). The Lena ice-wedge record shows that the recent isotopic temperatures are the highest of the past 7000 years. Despite similarities to Arctic temperature reconstructions of the last two millennia (Kaufman et al., 2009), it suggests a winter warming throughout the mid and late Holocene, opposite to most existing other proxy records (Wanner, 2008). This apparent contradiction can be explained by the seasonality of the ice-wedge genesis in combination with orbital and greenhouse gas forcing and is consistent with climate model simulations. We conclude that the present model-data mismatch might be an artefact of the summer bias of the existing proxy records and thus, our record helps to reconcile the understanding of the northern hemisphere Holocene temperature evolution. This is particular true for the Russian Arctic significantly

  5. Holocene Activity of the Quelccaya Ice Cap: A Working Model

    NASA Astrophysics Data System (ADS)

    Lowell, T. V.; Smith, C. A.; Kelly, M. A.; Stroup, J. S.

    2012-12-01

    The patterns and magnitudes of past climate change in the topics are still under discussion. We contribute here by reporting on patterns of glacier length changes of the largest glacier in the tropics, Quelccaya Ice Cap (~13.9°S, 70.9°W, summit at 5645 m). This ice cap has several local domes that may have different patterns of length changes because of differing elevations of the domes (high to the north, lower to the south). Prior work (Mark et al. 2003, Abbott et al., 2004; Thompson et al., 2005; Buffen, et al., 2009), new radiocarbon ages, and stratigraphic and geomorphic relationships are used to determine the general pattern of length changes for the outlets from this ice cap. We exploit geomorphic relationships and present new radiocarbon ages on interpreted stratigraphic sections to determine the pattern of length changes for this ice cap. Ice retreated during late glacial times (Rodbell and Seltzer, 2000; Kelly et al., in press). By 11,400 yr BP it had reached a position ~1.2 km beyond its present (2000 AD) extent. While length during the early Holocene is problematic, present evidence permits, but does not prove, extents of 0.5 to 1.0 km down-valley from the present margin. Between 6400 and 4400 yr BP the ice cap was smaller than present, but it advanced multiple times during the late Holocene. Lengths of up to 1 km beyond present were achieved at 3400 yr BP and ~500 yr BP. Additionally, the ice advanced to 0.8 km beyond its present margin at 1600 yr BP. Because these glaciers were temperate, we take these lengths to represent primarily changes in temperature. This may suggest that lowering insolation values in the northern hemisphere during the Holocene provide a first order control on tropical temperatures. Alternatively, it may be that major reorganization of the topical circulation belts about 5000 yr BP yields two configurations of the QIC and hence Holocene temperatures - one at the present ice margin and and the second about 1 km beyond the

  6. 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

  7. Multiproxy Reconstruction of Tropical Pacific Holocene Mean State Variability

    NASA Astrophysics Data System (ADS)

    Arbuszewski, J. A.; Oppo, D.; Huang, K. F.; Galy, V.; Dubois, N.; Mohtadi, M.; Herbert, T.; Rosenthal, Y.; Linsley, B. K.; Lynch-Stieglitz, J.; Koutavas, A.; Rustic, G. T.

    2014-12-01

    The El Niño-Southern Oscillation (ENSO) is the most prominent mode of tropical Pacific climate variability, significantly impacting both regional and global climate. In the past, the mean state of the Pacific Ocean has differed from today as evidenced by variability in the zonal water column structure. Recent paleoproxy based studies of tropical Pacific hydrology and surface temperature variability have hypothesized that observed climatological changes over the Holocene are directly linked to ENSO and/or mean state variability, complementing studies that dynamically relate centennial scale ENSO variability to mean state changes. These studies have suggested that mid Holocene ENSO variability was low and the mean state was more "La Niña" like. In the late Holocene, data have been interpreted as indicating an increase in ENSO variability with a more moderate mean state. Here, we test the hypothesis that observed climatological changes in the eastern tropical Pacific are related to mean state or ENSO variability during the Holocene. We focus our study on three sediment core locations from the equatorial Pacific: the Indo-Pacific Warm Pool (BJ803-119 GGC, 117MC), the Line Islands in the central Pacific (ML1208-18GC) and the Galapagos Islands in the Eastern Cold Tongue (KNR195-5 43 GGC, 42MC). These sites lie in regions poised to provide evidence of basin-wide equatorial water column structure changes in response to mean state and/or long-term ENSO variability. We use a multiproxy approach with data from both organic (sterol abundances) and inorganic proxies (Mg/Ca and δ18O of 4 planktonic foraminiferal species, % G. bulloides) to reconstruct zonal tropical Pacific (sub)surface temperature and stratification gradients over the Holocene. This approach enables us to combine the strengths of each individual proxy to derive more robust records. To put our data in the context of the broader Pacific and Indo-Pacific regions, we compare our new data to published records.

  8. Glacier response to North Atlantic climate variability during the Holocene

    NASA Astrophysics Data System (ADS)

    Balascio, N. L.; D'Andrea, W. J.; Bradley, R. S.

    2015-12-01

    Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher-frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial-scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the "8.2 ka" cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting ~100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansion during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a normal feature of

  9. A review of coastal palaeoclimate and relative sea-level reconstructions using δ13C and C/N ratios in organic material

    NASA Astrophysics Data System (ADS)

    Lamb, Angela L.; Wilson, Graham P.; Leng, Melanie J.

    2006-03-01

    Holocene reconstructions of relative sea-level (RSL) and environmental change in the coastal zone have become progressively more numerous since the importance of assessing possible future sea-level rises has become apparent. Traditionally this has been achieved using a combination of biological and physical indicators (e.g. pollen, diatoms, foraminifera, grain size, etc.). In some circumstances, microfossils can be rare or absent from Holocene sediments and in these cases carbon isotope ratios ( δ13C) and organic carbon to total nitrogen ratios (C/N) can be used because they have the potential to provide information as to the origin of organic material preserved in coastal environments. The distinction in δ13C and C/N of the various sources of carbon to estuarine sediments has led to its wide use as a tracer of carbon pathways and storage in estuaries. More recently these techniques have been applied to Holocene sediments to decipher changes in palaeocoastal environments and thus position relative to sea-level and/or palaeoriver discharge, which have direct relevance to palaeoclimate. This paper reviews the studies that have utilised this technique and explores examples from a wide range of coastal environments (saltmarshes, estuaries, lagoons, isolation basins and fjords). It also discusses the potential alteration of geochemical signatures as a result of decompositional processes. Organic matter decomposition has been shown to change sediment δ13C and C/N values and thus an understanding of the processes involved is necessary in order to have confidence in the palaeoenvironmental interpretation of Holocene δ13C and C/N. Decompositional shifts in C/N, and particularly δ13C, can occur over a relatively short time-period, however it is the direction of change in δ13C and C/N, rather than absolute values, that is key for interpreting changes in relative sea-level and thus such changes are commonly preserved.

  10. Holocene environmental and parasequence development of the St. Jones Estuary, Delaware (USA): Foraminiferal proxies of natural climatic and anthropogenic change

    USGS Publications Warehouse

    Leorri, E.; Martin, R.; McLaughlin, P.

    2006-01-01

    The benthic foraminiferal record of marshes located along western Delaware Bay (St. Jones Estuary, USA) reflects the response of estuaries to sea-level and paleoclimate change during the Holocene. System tracts are recognized and within them parasequences based on sedimentological and foraminiferal assemblages identification. The parasequences defined by foraminiferal assemblages appear correlative with rapid Holocene climate changes that are of worldwide significance: 6000-5000, 4200-3800, 3500-2500, 1200-1000, and 600??cal years BP. Following postglacial sea-level rise, modern subestuaries and marshes in the region began to develop between 6000 and 4000??years BP, depending on their proximity to the mouth of Delaware Bay and coastal geomorphology. Initial sediments were fluvial in origin, with freshwater marshes established around 4000??years BP. The subsequent sea-level transgression occurred sufficiently slowly that freshwater marshes alternated with salt marshes at the same sites to around 3000??years BP. Locally another two transgressions are identified at 1800 and 1000??years BP respectively. Marine influence increased in the estuaries until 600??years BP (Little Ice Age), when regression occurred. Sea-level began to rise again during the mid-19th Century at the end of the Little Ice Age, when marshes became established. The presence of a sand lens in the upper and middle estuary and the reduction in the number of tests in the top samples in cores from the same area also suggest an anthropogenic influence. The estuary infill resulted in a sharp transgressive sequence, represented by salt marsh foraminiferal assemblages in the upper part of the cores. The increase in marsh foraminifera in both areas suggests an increase in marine influence that might be due to the transgression beginning at the end of the Little Ice Age about 150-180??years ago coupled with anthropogenic straightening of the channel in 1913. ?? 2006 Elsevier B.V. All rights reserved.

  11. Holocene Sedimentation Pattern in the Backarc-Opening Ilan Plain, Taiwan: Implications for Regional Tectonic Subsidence and Basin Shape

    NASA Astrophysics Data System (ADS)

    Chan, Y. C.; Hsieh, Y. C.

    2015-12-01

    The triangular Ilan Plain in northern Taiwan has well-preserved sedimentary records which provide opportunities for understanding the subsidence and sedimentary processes at the southernmost tip of the backarc-opening Okinawa Trough. To better examine the deposition and tectonic history of the Ilan Plain, we analyzed data from 13 boreholes and used 14C dates to reconstruct basin sedimentary layers during the Holocene time. The borehole depths and their correspondent 14C ages are used to reconstruct the overall age models in the Ilan Plain. The sedimentation rates from the borehole locations vary significantly from 0.5 to 2.0 cm/yr. Age models were fitted using quadratic equations instead of linear equations. The linear age models, although commonly used by previous studies, may not be desirable because most age distributions show decreasing sedimentation rates, particularly after 6 ka BP. Six boreholes show very good fit using quadratic equations in the age models and five boreholes, mostly located along the coastal areas, show relatively linear relations. Two other boreholes do not have enough 14C dates and the reconstructed age models are less reliable in the two locations. Contour maps of the apparent sedimentation rates every thousand years are derived from the interpolated apparent sedimentation rates through the quadratic age models. Based on our 3D reconstruction of age models, the pattern of sedimentary layers in the Ilan Plain can be explained by the seaward-dipping basin shape and the propagation of sediment fronts during the Holocene time. The analyzed sedimentation pattern does not prefer noticeably localized faults or large estimates of tectonic subsidence rates in the backarc-opening environment.

  12. Mid Holocene lake level and shoreline behavior during the Nipissing phase of the upper Great Lakes at Alpena, Michigan, USA

    USGS Publications Warehouse

    Thompson, T.A.; Lepper, K.; Endres, A.L.; Johnston, J.W.; Baedke, S.J.; Argyilan, E.P.; Booth, R.K.; Wilcox, D.A.

    2011-01-01

    The Nipissing phase was the last pre-modern high-water stage of the upper Great Lakes. Represented as either a one- or two-peak highstand, the Nipissing occurred following a long-term lake-level rise. This transgression was primarily an erosional event with only the final stage of the transgression preserved as barriers, spits, and strandplains of beach ridges. South of Alpena, Michigan, mid to late Holocene coastal deposits occur as a strandplain between Devils Lake and Lake Huron. The landward part of this strandplain is a higher elevation platform that formed during the final stage of lake-level rise to the Nipissing peak. The pre-Nipissing shoreline transgressed over Devils Lake lagoonal deposits from 6.4 to 6.1. ka. The first beach ridge formed ~ 6. ka, and then the shoreline advanced toward Lake Huron, producing beach ridges about every 70. years. This depositional regression produced a slightly thickening wedge of sediment during a lake-level rise that formed 20 beach ridges. The rise ended at 4.5. ka at the Nipissing peak. This peak was short-lived, as lake level fell > 4. m during the following 500. years. During this lake-level rise and subsequent fall, the shoreline underwent several forms of shoreline behavior, including erosional transgression, aggradation, depositional transgression, depositional regression, and forced regression. Other upper Great Lakes Nipissing platforms indicate that the lake-level change observed at Alpena of a rapid pre-Nipissing lake-level rise followed by a slower rise to the Nipissing peak, and a post-Nipissing rapid lake-level fall is representative of mid Holocene lake level in the upper Great Lakes. ?? 2011 Elsevier B.V.

  13. Portable coastal observatories

    USGS Publications Warehouse

    Frye, Daniel; Butman, Bradford; Johnson, Mark; von der Heydt, Keith; Lerner, Steven

    2000-01-01

    Ocean observational science is in the midst of a paradigm shift from an expeditionary science centered on short research cruises and deployments of internally recording instruments to a sustained observational science where the ocean is monitored on a regular basis, much the way the atmosphere is monitored. While satellite remote sensing is one key way of meeting the challenge of real-time monitoring of large ocean regions, new technologies are required for in situ observations to measure conditions below the ocean surface and to measure ocean characteristics not observable from space. One method of making sustained observations in the coastal ocean is to install a fiber optic cable from shore to the area of interest. This approach has the advantage of providing power to offshore instruments and essentially unlimited bandwidth for data. The LEO-15 observatory offshore of New Jersey (yon Alt et al., 1997) and the planned Katama observatory offshore of Martha's Vineyard (Edson et al., 2000) use this approach. These sites, along with other cabled sites, will play an important role in coastal ocean science in the next decade. Cabled observatories, however, have two drawbacks that limit the number of sites that are likely to be installed. First, the cable and the cable installation are expensive and the shore station needed at the cable terminus is often in an environmentally sensitive area where competing interests must be resolved. Second, cabled sites are inherently limited geographically to sites within reach of the cable, so it is difficult to cover large areas of the coastal ocean.

  14. Sinking coastal cities

    NASA Astrophysics Data System (ADS)

    Erkens, Gilles; Bucx, Tom; Dam, Rien; De Lange, Ger; Lambert, John

    2014-05-01

    In many coastal and delta cities land subsidence now exceeds absolute sea level rise up to a factor of ten. Without action, parts of Jakarta, Ho Chi Minh City, Bangkok and numerous other coastal cities will sink below sea level. Land subsidence increases flood vulnerability (frequency, inundation depth and duration of floods), with floods causing major economic damage and loss of lives. In addition, differential land movement causes significant economic losses in the form of structural damage and high maintenance costs. This effects roads and transportation networks, hydraulic infrastructure - such as river embankments, sluice gates, flood barriers and pumping stations -, sewage systems, buildings and foundations. The total damage worldwide is estimated at billions of dollars annually. Excessive groundwater extraction after rapid urbanization and population growth is the main cause of severe land subsidence. In addition, coastal cities are often faced with larger natural subsidence, as they are built on thick sequences of soft soil. Because of ongoing urbanization and population growth in delta areas, in particular in coastal megacities, there is, and will be, more economic development in subsidence-prone areas. The impacts of subsidence are further exacerbated by extreme weather events (short term) and rising sea levels (long term).Consequently, detrimental impacts will increase in the near future, making it necessary to address subsidence related problems now. Subsidence is an issue that involves many policy fields, complex technical aspects and governance embedment. There is a need for an integrated approach in order to manage subsidence and to develop appropriate strategies and measures that are effective and efficient on both the short and long term. Urban (ground)water management, adaptive flood risk management and related spatial planning strategies are just examples of the options available. A major rethink is needed to deal with the 'hidden' but urgent

  15. Late Quaternary development of the Croatan Beach Ridge Complex, Bogue Sound, Bogue Banks, NC, USA and implications for coastal evolution

    NASA Astrophysics Data System (ADS)

    Lazar, Kelly B.; Mallinson, David J.; Culver, Stephen J.

    2016-06-01

    Foraminiferal, sedimentological, geophysical, and geochronologic data were utilized to elucidate the late Quaternary geologic development of the Croatan Beach Ridge Complex (CBRC), Bogue Sound, and Bogue Banks, North Carolina, USA. The CBRC is a relict beach ridge feature located on the mainland. It is separated from the modern barrier island, Bogue Banks, by Bogue Sound. Seventeen cores along shore-normal and shore-parallel transects provided material for sedimentologic and foraminiferal analysis and resulted in the recognition of seven depositional facies representing a variety of coastal depositional environments. Chronologic and depositional facies data suggest the CBRC was initiated during MIS 5a and rapid southward progradation produced a cape structure. Eolian reactivation of the upper sand of the CBRC occurred during the last glacial maximum (∼18 ka). The age of flood tide delta deposits in Bogue Sound suggests that the Holocene barrier island, Bogue Banks, had formed by ∼6 ka. Shoreface ravinement resulted in a shoreface landward of the present shoreline by ∼3.5 ka. Seaward and westward spit progradation of Bogue Banks began ∼1.7 ka and continued to ∼1.3 ka. Normal marine salinity conditions were present in Bogue Sound ∼1.1 ka, suggesting removal of at least the narrowest parts of the barrier island, coeval with a previously documented segmentation of the southern Outer Banks barrier islands. Previous work has linked this segmentation to climate warming and increased tropical storm activity during the Medieval Climate Anomaly. This study illustrates the complex response of this coastal system to Pleistocene and Holocene sea-level and climate change over two major sea-level cycles. In particular, the regional geomorphology during MIS5a and the Holocene sea-level highstand differ significantly and this, in large part, was controlled by the antecedent geologic framework, resulted in the contrasting more localized coastal geomorphic response.

  16. Holocene Scarp on the Sawtooth Normal Fault, Central Idaho

    NASA Astrophysics Data System (ADS)

    Thackray, G. D.; Rodgers, D. W.; Streutker, D. R.; Kemp, C. D.; Drabick, A. J.

    2006-12-01

    Analysis of LiDAR, air photo, and field data indicates the east-dipping, range-front normal fault of the Sawtooth Mountains has previously unrecognized Holocene offset. A fault scarp is most clearly represented in a bare- earth digital elevation model (DEM) derived from high-resolution LiDAR data. First and last pulse LiDAR data with an average post spacing of 0.5 m were used to compute both bare-earth elevation and local slope values. As the area is forested, vegetation removal was performed using an iterative interpolation method. Holocene fault offset likely extends along at least 23 km of the range front. In the vicinity of Redfish Lake, the scarp can be traced discontinuously for ca. 13 km (the length of LiDAR coverage) along the eastern range-front and cuts glacial, fluvial, and hillslope landforms of Late Pleistocene to Holocene age. Air photo analysis of the range-front north and south of the LiDAR coverage area yields strong evidence, such as topographic offsets, vegetation lineaments, and stream alignments, that late Pleistocene and Holocene faulting likely extends ca. 23 km along the range front, from Decker Creek to Stanley Lake. This zone of clearest postglacial offset corresponds with the highest range front topography in the Sawtooth Range. Weaker evidence suggests that postglacial faulting may extend as much as 10 km further NW of and 17 km further SE of that 23 km section. Scarp geometry and offset vary with location. The fault scarp generally strikes 025 deg. but changes to 040 deg. north of Goat Creek. A single, east-facing scarp is present in some places, such as at Bench Lakes, but more commonly en echelon scarps define a fault zone about 20 m wide. Scarp height, as measured from LiDAR data, ranges from 2.5 to 8 m (typically 3-5 m). Late Pleistocene glacial landforms are offset 4-8 m, while uncommon Holocene fluvial surfaces (e.g., at Fishhook Creek) are offset 2.5 to 3 m. These relationships potentially document two fault ruptures since

  17. Geophysical Evidence for Holocene Lake-Level Change in Southern California (Dry Lake): Additional Evidence for a Regional Early Holocene High Stand

    NASA Astrophysics Data System (ADS)

    Kirby, M. E.; Bird, B. W.; Howat, I. M.; Tulaczyk, S.

    2007-12-01

    Ground penetrating radar data are used to develop a Holocene history of basin sedimentation in a small, alpine lake in Southern California (Dry Lake). We define three depositional sequences spanning the past 9,000 calendar years before present (cy BP). Although, the basin contains sediments clearly older than the Holocene, we focus on the past 9,000 cy BP to match our similarly aged sediment cores. Sequence I represents the first phase of an early Holocene high stand. A major regression, perhaps following the 8,200 year cold event, separates Sequence I from Sequence II. The timing of this regression is approximately coeval with major regressions at Owens Lake (Bacon et al., 2006) in southeastern California and Tulare Lake (Negrini et al., 2006) in the southern Central Valley of California. Sequence II represents the second phase of the early Holocene high stand. This second high stand phase is also observed at Tulare Lake but not at Owens Lake. Sequence III represents a permanent shift to low or dry lake stands. By 4,000 cy BP, the lake earns rightfully its appellation of Dry Lake as indicated by a permanently contracted central basin. The similarity in ages of early Holocene lake level change across the greater region of Southern California suggests a similar external forcing - perhaps modulation of early Holocene storm activity by insolation (Kirby et al., 2007). The lake level records are less congruous for the mid-to-late Holocene across the region. Specifically for Dry Lake, it is not clear what caused the apparently rapid shift from a deep, early Holocene lake to a permanent shallow or dry lake by the mid-Holocene.

  18. Mid-late Holocene climate and ecology reconstruction around the Lagoon Mae-ho, East Korea based on diatom assemblage

    NASA Astrophysics Data System (ADS)

    Katsuki, K.; Lim, J.; Nahm, W.; Nakanishi, T.

    2012-12-01

    Diatom assemblage analysis in core sediment samples, PMR-2, from around Lagoon Mae-ho was examined for the purpose of evaluating the climate and local ecosystem change during the mid-late Holocene. Core PMR-2 is approximately 11 m length core, which was obtained from a front of reclaimed land around Lagoon Mae-ho in northeastern coast of Korea. Except for the top 2.5 m, preserved condition of diatom remain was well throughout the core. Radiocarbon ages were measured by a 1MV AMS facility at KIGAM. In particularly, high diatom remains were contained in obvious lamina layer between 7.0-9.5 m depth. Based on the diatom assemblage analysis, core PMR-2 was probably located under the small channel before 5,800 cal yr BP, which was under the lamina layer. Diatom assemblage was composed by the fresh and brackish taxa at that layer. Eutrophic lagoon was formed along the sea level increasing about 5,800 cal yr BP. Since 5,800 cal yr BP, location of core PMR-2 was covered by lagoon condition. Dominant taxa were eutrophic brackish diatom such as Cyclotella caspia and Cyclotella striata. Obvious lamina layer was composed under this condition. Since 4,000 cal yr BP, water exchange rate between the sea and paleo-lagoon Mae-ho was increased. This was indicated by the increasing marine-brackish diatom taxa. Anoxic bottom condition of the paleo-lagoon Mae-ho was resolved due to the increasing sea water inflow, and lamina layer was disappeared. After then, water depth of lagoon Mae-ho had become shallow gradually. Coring site was located around coastal marsh, and finally the site was reclaimed by human activity in recent. As mention above, obvious lamina was composed under the eutropic lagoon condition between 4,000 and 5,800 cal yr BP (7.0-9.5 m depth). These lamina were annual layers, was set of spring diatom bloom layer and other season's layer. In this presentation, we will discuss not only late to mid Holocene environmental change, but also discuss the short term climate

  19. West Antarctic Ice Sheet retreat from Pine Island Bay during the Holocene: New insights into forcing mechanisms

    NASA Astrophysics Data System (ADS)

    Hillenbrand, Claus-Dieter; Smith, James; Kuhn, Gerhard; Poole, Chris; Hodell, David; Elderfield, Harry; Kender, Sev; Williams, Mark; Peck, Victoria; Larter, Robert; Klages, Johann; Graham, Alastair; Forwick, Matthias; Gohl, Karsten

    2013-04-01

    The Amundsen Sea sector of the largely marine-based and therefore conditionally unstable West Antarctic Ice Sheet (WAIS) contains enough ice to raise global sea level by ca. 1.5 metres. At present, ice streams draining this sector into the Southern Ocean, especially glaciers flowing into Pine Island Bay in the eastern Amundsen Sea embayment, are undergoing considerable mass loss characterised by major thinning, flow acceleration and rapid grounding-line retreat. Sub-ice shelf melting by relatively warm Circumpolar Deep Water (CDW) upwelling onto the continental shelf is held responsible for these dynamical changes but atmospheric warming in West Antarctica may also have contributed to them. In contrast to the modern situation, the long-term history of the Amundsen Sea sector and the mechanisms forcing its deglaciation during the Holocene are only poorly constrained. We will present new palaeoenvironmenal data obtained from marine sediment cores collected in Pine Island Bay. The cores targeted shallow sites on the inner continental shelf and successfully recovered sedimentary sequences bearing calcareous microfossils. Radiocarbon ages on these microfossils demonstrate that the grounding line of the WAIS retreated to within ~100 km of its modern position before ca. 10 kyr BP (thousand years before present), which is consistent with an early WAIS retreat from near-coastal locations in the western Amundsen Sea embayment. Currently, there is no evidence that the grounding line had retreated landward of its modern position during the Holocene. Therefore, the chronological constraints may imply that during the last 10 kyr any episodes of fast grounding-line retreat similar to those observed today were short-lived and rare. Preliminary geochemical data from benthic and planktonic foraminifera tests in the cores from Pine Island Bay reveals that intense CDW upwelling coincided with and may have forced the deglaciation of the inner continental shelf. Furthermore, we observe

  20. Three Storm Surge Events during Late Holocene in Shelly Gravel Sediments of the most Southern Coast of Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Yang, Dong Yoon

    2015-04-01

    pattern are likely to be related with high contents of gravels and cobbles in units 2 and 4. There have been more than three stronger storms to deliver the marine gravels and shells to the erosion face of 2.2m in elevation. Erosion process pronounced by basement erosion of tuffaceous rock, followed by sedimentation process of Pleistocene debris flows, subsequently Holocene erosion, and finally Holocene gravels and shells by reflected waves near beach. The sedimentation is not controlled by the influence of break water, but is affected by the reflected water from coastal zone.

  1. NATIONAL COASTAL CONDITION REPORT IV

    EPA Science Inventory

    The National Coastal Condition Report IV (NCCR IV) is the fourth in a series of environmental assessments of U.S. coastal waters and the Great Lakes. The report includes assessments of all the nation’s estuaries in the contiguous 48 states and Puerto Rico, south-eastern Alaska, ...

  2. Non-energy resources, Connecticut and Rhode Island coastal waters

    USGS Publications Warehouse

    Neff, N.F.; Lewis, R.S.

    1989-01-01

    Cores collected from Long Island Sound, Connecticut, were used to establish control on the geologic framework of the area. Lithologic and stratigraphic analyses verified the presence of the following units: (1) Cretaceous coastal plain, (2) Pleistocene glacial till, (3) late Pleistocene glacial lake, (4) late Pleistocene glacial outwash, and (5) Holocene fluvial, estuarine and marine deposits. Cores collected in Block Island Sound, Rhode Island, were obtained from inferred, relict shoreline features and were analyzed for heavy mineral content. Concentrations ranged from 0.3 to 3.4%; no significant downcore changes were found. The results indicated that surficial sediments in areas of high-velocity tidal flow yield greater amounts of heavy minerals than do inferred placer deposits. During the second phase of the program of study, Connecticut and Rhode Island pooled resources to develop a study plan for the comprehensive quantification of all non-energy resources in the adjacent waters of the states. A literature and data survey was conducted to assess the occurrence, extent, and accessibility of these resources. Sand and gravel and heavy minerals were found in concentrations offering potential for resource exploitation. Constraints on exploitation include (1) water depth restrictions for the protection of shellfish beds and public beaches, (2) fishing activities, (3) military, commercial, and fishing vessel traffic, (4) seafloor cable routes and (5) dump sites. Deposits composed of Pleistocene glacial sediments and/or Holocene marine sediments in regions of little or no user conflict were identified as sites potentially suitable for resource exploitation. The study plan stated additional data needs (geophysical profiling and vibracore sampling) at these sites. Subsequent to these recommendations, high-resolution seismic profiles and sidescan sonographs were obtained from these sites. Seismic stratigraphic analyses confirm the presence of extensive deposits of

  3. Sinking coastal cities

    NASA Astrophysics Data System (ADS)

    Erkens, G.; Bucx, T.; Dam, R.; de Lange, G.; Lambert, J.

    2015-11-01

    In many coastal and delta cities land subsidence now exceeds absolute sea level rise up to a factor of ten. A major cause for severe land subsidence is excessive groundwater extraction related to rapid urbanization and population growth. Without action, parts of Jakarta, Ho Chi Minh City, Bangkok and numerous other coastal cities will sink below sea level. Land subsidence increases flood vulnerability (frequency, inundation depth and duration of floods), with floods causing major economic damage and loss of lives. In addition, differential land movement causes significant economic losses in the form of structural damage and high maintenance costs for (infra)structure. The total damage worldwide is estimated at billions of dollars annually. As subsidence is often spatially variable and can be caused by multiple processes, an assessment of subsidence in delta cities needs to answer questions such as: what are the main causes? What is the current subsidence rate and what are future scenarios (and interaction with other major environmental issues)? Where are the vulnerable areas? What are the impacts and risks? How can adverse impacts be mitigated or compensated for? Who is involved and responsible to act? In this study a quick-assessment of subsidence is performed on the following mega-cities: Jakarta, Ho Chi Minh City, Dhaka, New Orleans and Bangkok. Results of these case studies will be presented and compared, and a (generic) approach how to deal with subsidence in current and future subsidence-prone areas is provided.

  4. Coastal Zone Color Scanner

    NASA Technical Reports Server (NTRS)

    Johnson, B.

    1988-01-01

    The Coastal Zone Color Scanner (CZCS) spacecraft ocean color instrument is capable of measuring and mapping global ocean surface chlorophyll concentration. It is a scanning radiometer with multiband capability. With new electronics and some mechanical, and optical re-work, it probably can be made flight worthy. Some additional components of a second flight model are also available. An engineering study and further tests are necessary to determine exactly what effort is required to properly prepare the instrument for spaceflight and the nature of interfaces to prospective spacecraft. The CZCS provides operational instrument capability for monitoring of ocean productivity and currents. It could be a simple, low cost alternative to developing new instruments for ocean color imaging. Researchers have determined that with global ocean color data they can: specify quantitatively the role of oceans in the global carbon cycle and other major biogeochemical cycles; determine the magnitude and variability of annual primary production by marine phytoplankton on a global scale; understand the fate of fluvial nutrients and their possible affect on carbon budgets; elucidate the coupling mechanism between upwelling and large scale patterns in ocean basins; answer questions concerning the large scale distribution and timing of spring blooms in the global ocean; acquire a better understanding of the processes associated with mixing along the edge of eddies, coastal currents, western boundary currents, etc., and acquire global data on marine optical properties.

  5. Climatic-eustatic control of Holocene nearshore parasequence development, southeastern Texas coast

    USGS Publications Warehouse

    Morton, Robert A.; Kindinger, Jack G.; Flocks, James G.; Stewart, Laura B.

    1999-01-01

    Sediment cores, seismic profiles, radiocarbon dates, and faunal assemblages were used to interpret the depositional setting and geological evolution of the southeastern Texas coast during the last glacio-eustatic cycle. Discrete lithofacies and biofacies zones in the ebb-dominated Sabine Lake estuary and adjacent chenier plain record alternating periods of rapid marine flooding and gradual shoaling related to linked climatic/eustatic fluctuations. Monospecific zones of the mollusks Rangia cuneata and Crassostrea virginica, respectively, indicate high fresh water outflow followed by invasion of marine water, whereas intervening organic-rich zones record bayhead delta deposition. High-frequency parasequence stacking patterns within the valley fill and across the adjacent interfluve reflect an initial rapid rise in sea level about 9 ka that flooded abandoned alluvial terraces and caused onlap of Holocene marsh in the incised valley. The rapid rise was followed by slowly rising and oscillating sea level that filled the deepest portions of the incised valleys with fluvially dominated estuarine deposits, and then a maximum highstand (+1 m msl) about 5 ka that flooded the former subaerial coastal plain between the incised valleys and constructed the highest beach ridges. Between 3.5 and 1.5 ka, sea level oscillated and gradually fell, causing a forced regression and rapid progradation of both the chenier plain and accretionary barrier islands. The only significant sands in the valley fill are (1) falling-stage and lowstand-fluvial sediments between the basal sequence boundary and transgressive surface unconformity, and (2) highstand beach-ridge sediments of the chenier plain.

  6. Holocene vegetation and fire history of the mountains of northern Sicily (Italy)

    USGS Publications Warehouse

    Tinner, Willy; Vescovi, Elisa; Van Leeuwen, Jacqueline; Colombaroli, Daniele; Henne, Paul; Kaltenrieder, Petra; Morales-Molino, Cesar; Beffa, Giorgia; Gnaegi, Bettina; Van der Knaap, Pim W O; La Mantia, Tommaso; Pasta, Salvatore

    2016-01-01

    Knowledge about vegetation and fire history of the mountains of Northern Sicily is scanty. We analysed five sites to fill this gap and used terrestrial plant macrofossils to establish robust radiocarbon chronologies. Palynological records from Gorgo Tondo, Gorgo Lungo, Marcato Cixé, Urgo Pietra Giordano and Gorgo Pollicino show that under natural or near natural conditions, deciduous forests (Quercus pubescens, Q. cerris, Fraxinus ornus, Ulmus), that included a substantial portion of evergreen broadleaved species (Q. suber, Q. ilex, Hedera helix), prevailed in the upper meso-mediterranean belt. Mesophilous deciduous and evergreen broadleaved trees (Fagus sylvatica, Ilex aquifolium) dominated in the natural or quasi-natural forests of the oro-mediterranean belt. Forests were repeatedly opened for agricultural purposes. Fire activity was closely associated with farming, providing evidence that burning was a primary land use tool since Neolithic times. Land use and fire activity intensified during the Early Neolithic at 5000 bc, at the onset of the Bronze Age at 2500 bc and at the onset of the Iron Age at 800 bc. Our data and previous studies suggest that the large majority of open land communities in Sicily, from the coastal lowlands to the mountain areas below the thorny-cushion Astragalus belt (ca. 1,800 m a.s.l.), would rapidly develop into forests if land use ceased. Mesophilous Fagus-Ilex forests developed under warm mid Holocene conditions and were resilient to the combined impacts of humans and climate. The past ecology suggests a resilience of these summer-drought adapted communities to climate warming of about 2 °C. Hence, they may be particularly suited to provide heat and drought-adaptedFagus sylvatica ecotypes for maintaining drought-sensitive Central European beech forests under global warming conditions.

  7. Holocene evolution of diatom and silicoflagellate paleoceanography in Slocum Arm, a fjord in southeastern Alaska

    USGS Publications Warehouse

    Barron, John A.; Bukry, John D.; Addison, Jason A.; Ager, Thomas A.

    2016-01-01

    Diatom and silicoflagellate assemblages in cores EW0408-47JC, -47TC, -46MC (57° 34.5278′ N, 136° 3.7764′ W, 114 m water depth) taken from the outer portion of Slocum Arm, a post-glacial fjord in southeastern Alaska, reveal the paleoclimatic and paleoceanographic evolution of the eastern margin of the Gulf of Alaska (GoA) during the past 10,000 years. Between ~ 10 and 6.8 cal ka, periods of low salinity and cool water conditions alternated with brief intervals marked by the increased influx of oceanic, more saline and likely warmer waters. Increased surface water stability characterized by a middle Holocene interval between ~ 6.8 and 3.2 cal ka is typified by increased abundances of northeastern Pacific Thalassiosira spp. that are indicative of spring coastal blooms and decreased abundances of warm and higher salinity oceanic diatoms. At ~ 3.2 cal ka, an abrupt increase in both the relative contribution of oceanic diatoms and silicoflagellates suggestive of cooler upwelling conditions occurred in the -47JC record. A stepwise increase in alkenone sea surface temperature in northern GoA core EW0408-85JC and increase in southern sourced precipitation in the carbonate δ18O record of Jellybean Lake (Yukon) present evidence that this ~ 3.2 cal ka event coincided with the onset of enhanced positive Pacific Decadal Oscillation-like (PDO) conditions in the GoA. These positive PDO-like conditions persisted until ~ 1.0 cal ka and were followed by high amplitude fluctuations in the relative abundance of diatom and silicoflagellate assemblages.

  8. Short organic carbon turnover time and narrow 14C age spectra in early Holocene wetland paleosols

    NASA Astrophysics Data System (ADS)

    Vetter, Lael; Rosenheim, Brad E.; Fernandez, Alvaro; Törnqvist, Torbjörn E.

    2017-01-01

    Paleosols contain information about the rates of soil organic carbon turnover when the soil was actively forming. However, this temporal information is often difficult to interpret without tight stratigraphic control on the age of the paleosol. Here we apply ramped pyrolysis/oxidation (Ramped PyrOx) 14C analyses to evaluate age spectra of transgressive early Holocene paleosols from the Mississippi Delta in southeastern Louisiana, USA. We find 14C age spectra from soil organic matter (SOM) in both paleosols and overlying basal peats that represent variability in age that is close to, or only slightly greater than, analytical uncertainty of 14C measurements, despite different sources of carbon with likely disparate ages. Such age spectra have not previously been observed in the sedimentary record. Here they indicate vigorous soil carbon turnover prior to burial, which homogenized 14C ages within SOM across the entire thermochemical spectrum. The weighted bulk 14C ages from Ramped PyrOx of paleosols and overlying peats are identical within analytical and process-associated uncertainty, and corroborate 14C ages from charcoal fragments and plant macrofossils from the overlying peat. The youngest ages from Ramped PyrOx age spectra may also potentially be applied as chronometers for stratigraphic burial ages. Our results suggest rapid turnover (≪300 years) of carbon in these soils relative to input of allochthonous carbon, indicating that the 14C age of different soil components is decoupled from thermochemical stability and instead reflects vigorous turnover processes. The concurrence of paleosol and peat 14C ages also suggests that pedogenic processes were linked with the development of coastal marshes, and that the priming effect potentially masked the signal of allochthonous carbon inputs during sea level rise.

  9. Holocene siliciclastic-carbonate facies mosaics, Northern Belize: Exploration analog to some midcontinent Pennsylvanian (Morrowan) reservoirs

    SciTech Connect

    Lowe, D.B.; Mazzullo, S.J.

    1995-09-01

    Midwinter Lagoon is a large, shallow coastal lagoon, bordered on its seaward side by a barrier, along the mainland coast of northern Belize. As much as 19 ft of Holocene sediments, deposited on karsted Tertiary limestones during the Flandrian transgression, consist of a complex mosaic of mixed siliciclastic and carbonate facies. Basal transgressive marine, intra-lagoonal facies are variously siliciclastic-rich carbonates to carbonate-rich siliciclastics, locally with layers of shoreline mangrove peat. These facies shallow-upward to either siliciclastic or carbonate-dominated sands or muds. Lagoonal facies were deposited within a broad topographic low, locally punctuated by bedrock highs, on the underlying limestone. The seaward edge of the barrier bar complex, which was deposited on a linear topographic high, consists mostly of quartz sands, whereas the lagoonal side is a mixture of quartzose and carbonate sediments (sands and muds). The barrier bar appears to have accreted southward in response to southerly longshore drift as a tidal inlet-spit complex; quartz sands are being transported into the lagoon from its seaward side. In terms of geometry, modern and buried, intra-lagoonal carbonate sands occur as lobes deposited proximal to extant and older tidal inlets. Either carbonate or siliciclastic sands variously occur as erratically distributed, anastomosing beach deposits around small mangrove islands and along the irregular mainland coast. In contrast, siliciclastic sands on the seaward side of the barrier define a narrow but areally persistent linear trend. Similar complex facies associations and geometries are typical of many Pennsylvanian (Morrowan) reservoirs in the midcontinent US.

  10. Annual layers revealed by GPR in the subsurface of a prograding coastal barrier, southwest Washington, U.S.A

    USGS Publications Warehouse

    Moore, L.J.; Jol, H.M.; Kruse, S.; Vanderburgh, S.; Kaminsky, G.M.

    2004-01-01

    The southwest Washington coastline has experienced extremely high rates of progradation during the late Holocene. Subsurface stratigraphy, preserved because of progradation and interpreted using ground-penetrating radar (GPR), has previously been used successfully to document coastal response to prehistoric storm and earthquake events. New GPR data collected at Ocean Shores, Washington, suggest that the historic stratigraphy of the coastal barrier in this area represents a higher resolution record of coastal behavior than previously thought. GPR records for this location at 200 MHz reveal a series of gently sloping, seaward-dipping reflections with slopes similar to the modern beach and spacings on the order of 20-45 cm. Field evidence and model results suggest that thin (1-10 cm), possibly magnetite-rich, heavy-mineral lags or low-porosity layers left by winter storms and separated by thick (20-40 cm) summer progradational sequences are responsible for generating the GPR reflections. These results indicate that a record of annual progradation is preserved in the subsurface of the prograding barrier and can be quantified using GPR. Such records of annual coastal behavior, where available, will be invaluable in understanding past coastal response to climatic and tectonic forcing. ?? 2004.

  11. 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

    2016-04-25

    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.

  12. 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

  13. Comparison of Pleistocene and Holocene barrier island beach-to-offshore sequences, Georgia and northeast Florida coasts, U.S.A.

    NASA Astrophysics Data System (ADS)

    Howard, James D.; Scott, Richard M.

    1983-03-01

    Well-exposed vertical sequences of Pleistocene shoreline deposits are rare on the coastal plain of the southeastern United States. An important exception is an exposure along the St. Mary's River on the Georgia-Florida state line. This outcrop contains an excellent depositional strike section of a prograding offshore, shoreface, foreshore and backshore sequence with well-preserved physical and biogenic sedimentary structures. Offshore sediments are composed of highly bioturbated, muddy fine sand. Distinct burrows and bedding become progressively more abundant upward through a transition zone into shoreface deposits. The shoreface is dominated by the trace fossil Ophiomorpha nodosa and physical sedimentary structures are poorly preserved. Foreshore sediments contain low-angle seaward dipping beds, high-angle landward dipping beds and ripple laminae. Heavy-mineral accumulations in the backshore accentuate bedding and biogenic structures such as ghost crab and insect burrows and bioturbation by amphipods. Direct correlation of most primary physical and biogenic sedimentary structures and textures can be made between the Pleistocene and Holocene beach-to-offshore facies as