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Sample records for early holocene site

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

    USGS Publications Warehouse

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

    2008-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2004-07-01

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

  3. The paleo-environment of the first early-Holocene inhabitants of the Bolivian Amazon

    NASA Astrophysics Data System (ADS)

    Lombardo, Umberto; Veit, Heinz; Capriles, José

    2013-04-01

    The Llanos de Moxos (LM), in the Bolivian lowlands, is a seasonally flooded savannah which has been inhabited since the beginning of the Holocene. Early Holocene archaeological sites, mostly shell middens, are nowadays hidden under forest islands: patches of forest surrounded by savannah. Despite their similar aspect, these archaeological sites are located in very different geomorphological and stratigraphic settings. Preliminary results of geo-archaeological research on two early-Holocene sites and their surroundings will be presented. The data suggests that the early Holocene landscape of the LM was significantly different from what we see nowadays. One of the sites, associated with an early to mid-Holocene paleosol, has been almost totally buried by fluvial sediments and only its topmost 30-40 cm has remained above the alluvium that forms the current savannah. The second site, currently outcropping in the middle of a flat swamp, was actually located on a sandy fluvial levee and subsequently flooded and partially buried by peat-like sediments. The events that lead to the burial of these sites, and probably caused the abandonment of the area, are still not completely understood. Linking together paleo-ecological reconstructions and archaeology, this research hopes to shed some light on the large scale environmental changes that took place in south-western Amazonia during the Holocene, the nature of human-environment interactions at the time and the potential value of these sites as paleo-environmental proxies.

  4. 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.

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

    PubMed

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  8. Early and middle holocene hunter-gatherer occupations in western Amazonia: the hidden shell middens.

    PubMed

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

    2013-01-01

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

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

    PubMed Central

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

    2013-01-01

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

  10. 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. PMID:20368451

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  15. Early Holocene chicken domestication in northern China.

    PubMed

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

    2014-12-01

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

  16. Early Holocene chicken domestication in northern China

    PubMed Central

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

    2014-01-01

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

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

    USGS Publications Warehouse

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

    1990-01-01

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

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

    USGS Publications Warehouse

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

    2013-01-01

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

  19. 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.

  20. Early Holocene Great Salt Lake, USA

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  1. Early Holocene meltwater events in the Labrador Sea

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    PubMed

    Stojanowski, Christopher M; Knudson, Kelly J

    2011-09-01

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

  3. Early Holocene glaciation on Mount Baker, Washington State, USA

    NASA Astrophysics Data System (ADS)

    Thomas, Paul A.; Easterbrook, Don J.; Clark, Peter U.

    2000-07-01

    The relation between radiocarbon-dated tephras and glacial moraines on the south flank of Mount Baker, Washington, records evidence of an early Holocene glacier advance. Scoria that erupted from a local cinder cone 8420±70 14C yr BP (9450±100 cal yr) occurs immediately in front of, but not on, a complex of moraines overlain by Mazama ash. Radiocarbon ages of 7670±130 14C yr BP (8415±110 cal yr) and 7045±65 14C yr BP (7890±90 cal yr) were obtained from charred wood below the Mazama ash and above till of the moraines, bracketing the age of the glacial advance between ˜7700 and 8400 14C yr BP (˜8400 and 9450 cal yr). Well-preserved Little Ice Age moraines occur proximal to the maximum Holocene positions. Assuming that precipitation regimes were similar, depression of former equilibrium line altitudes suggests that climate during the early Holocene event was at most ˜2°C cooler than present, and ˜0.5°C cooler than the Little Ice Age.

  4. Pine nut use in the Early Holocene and beyond: The danger cave archaeobotanical record

    USGS Publications Warehouse

    Rhode, D.; Madsen, D.B.

    1998-01-01

    Nuts of limber pine (Pinus flexilis) from Early Holocene strata in Danger Cave, Utah, are distinguishable by seed-coat sculpturing from pine nuts of single-needled pinyon (Pinus monophylla), which occur in strata dating <7000 years BP. Owls and other taphonomic agents may deposit pine nuts in archaeological sites, but the morphology of the pine nuts in Danger Cave strongly indicate they were deposited by human foragers who brought small quantities with them for food for at least the last 7500 years. Large-scale transport of pine nuts to Danger Cave from distant hinterlands is unlikely, however. The seamless transition from limber pine to pinyon pine nuts in the Danger Cave record suggests that foragers who had utilized limber pine as a food resource easily switched to using pinyon pine nuts when pinyon pine migrated into the region at the close of the Early Holocene.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  6. An early Holocene Greenland whale from Melville Bugt, Greenland

    NASA Astrophysics Data System (ADS)

    Bennike, Ole

    2008-01-01

    Radiocarbon age determination of a Greenland whale ( Balaena mysticetus) vertebra from Melville Bugt in northwestern Greenland yields an age of 9259-8989 cal yr BP. The margin of the Greenland Ice Sheet in Melville Bugt was situated behind its AD 1950-2000 position in the early Holocene, at a similar position to that being reached following rapid retreat in recent years. Such an early deglaciation of areas close to the Greenland Ice Sheet is unusual. This probably reflects the unique glaciological setting resulting from the narrow fringe of ice-free islands and peninsulas and offshore waters with deep areas that characterize this part of Greenland. The timing of Greenland Ice Sheet retreat to its present margin varies significantly around Greenland.

  7. Impact of a drier Early-Mid-Holocene climate upon Amazonian forests.

    PubMed

    Mayle, Francis E; Power, Mitchell J

    2008-05-27

    This paper uses a palaeoecological approach to examine the impact of drier climatic conditions of the Early-Mid-Holocene (ca 8000-4000 years ago) upon Amazonia's forests and their fire regimes. Palaeovegetation (pollen data) and palaeofire (charcoal) records are synthesized from 20 sites within the present tropical forest biome, and the underlying causes of any emergent patterns or changes are explored by reference to independent palaeoclimate data and present-day patterns of precipitation, forest cover and fire activity across Amazonia. During the Early-Mid-Holocene, Andean cloud forest taxa were replaced by lowland tree taxa as the cloud base rose while lowland ecotonal areas, which are presently covered by evergreen rainforest, were instead dominated by savannahs and/or semi-deciduous dry forests. Elsewhere in the Amazon Basin there is considerable spatial and temporal variation in patterns of vegetation disturbance and fire, which probably reflects the complex heterogeneous patterns in precipitation and seasonality across the basin, and the interactions between climate change, drought- and fire susceptibility of the forests, and Palaeo-Indian land use. Our analysis shows that the forest biome in most parts of Amazonia appears to have been remarkably resilient to climatic conditions significantly drier than those of today, despite widespread evidence of forest burning. Only in ecotonal areas is there evidence of biome replacement in the Holocene. From this palaeoecological perspective, we argue against the Amazon forest 'dieback' scenario simulated for the future.

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

    NASA Astrophysics Data System (ADS)

    Kemp, Melissa E.; Hadly, Elizabeth A.

    2016-03-01

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

  9. Was the Black Sea catastrophically flooded in the early Holocene?

    NASA Astrophysics Data System (ADS)

    Giosan, Liviu; Filip, Florin; Constatinescu, Stefan

    2009-01-01

    A catastrophic flooding of the Black Sea basin was proposed to have occurred during its reconnection to the ocean in the early Holocene. Possible cultural consequences of the flood include the migration of Neolithic farmers from around the Black Sea towards central Europe as well as the creation of flood myths. Stratigraphic and paleo-geomorphologic information from Danube delta aided by radiocarbon ages on articulated mollusks constrain the level in the Black Sea before the marine reconnection to ca 30 m below the present sea level rather than 80 m or lower. If the flood occurred at all, the sea level increase and the flooded area during the reconnection were significantly smaller than previously proposed.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  13. Insolation forcing of early Holocene climate in Southern East Africa?

    NASA Astrophysics Data System (ADS)

    Barker, P. A.; Leng, M. J.; Gasse, F.; Johnson, T. C.

    2003-04-01

    Palaeoclimatic investigations in southern Tanzania and from Lake Malawi, has forced a re-evaluation of the processes controlling long-term climate changes in the region (Gasse et al., 2002; Johnson et al., 2002). In Lake Malawi at the last glacial maximum (LGM) abundant diatom periphyton (up to 30% at the LGM) and reduced biogenic silica accumulation in cores M98-1P and M98-2P suggests a low lake level and a relatively dry climate (Gasse et al., 2002). The implication is that orbital forcing of southern hemisphere climate was subservient to glacial boundary conditions (Johnson et al., 2002), in contrast to parts of southern tropical South America (Baker, 2002). The situation during the early Holocene, when orbital configuration should produce dry conditions in the southern tropics, is ambiguous. Carbonates precipitated in the southern basin of Lake Malawi, indicating a lowering of lake level and geochemical proxies from the north basin (biogenic silica and total phosphorus) suggest productivity fell, yet the diatom records from the northern basin are complacent, showing only shifts between different planktonic species. Here we present preliminary oxygen isotope data from diatom silica in an attempt to address the lake’s status at this time and implications for the precipitation-evaporation ratio (P-E). This is the first time this method has been applied to the sediments of a large African lake and some of the issues regarding the climatic calibration of the oxygen isotope ratios will be addressed. We will compare the isotope changes to other indicators from Lake Malawi and elsewhere in the region to investigate to what extent reduced insolation moderated the water balance of lakes in the southern tropics in contrast to the wet phase experienced by the equatorial lakes.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    SciTech Connect

    Gajewski, K. ); Garralla, S.

    1992-11-01

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

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

    SciTech Connect

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

    1985-06-01

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

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

    PubMed

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

    2010-10-01

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

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

    PubMed

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  3. 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.

  4. Possible Signatures of Hominin Hybridization from the Early Holocene of Southwest China.

    PubMed

    Curnoe, Darren; Ji, Xueping; Taçon, Paul S C; Yaozheng, Ge

    2015-01-01

    We have previously described hominin remains with numerous archaic traits from two localities (Maludong and Longlin Cave) in Southwest China dating to the Pleistocene-Holocene transition. If correct, this finding has important implications for understanding the late phases of human evolution. Alternative interpretations have suggested these fossils instead fit within the normal range of variation for early modern humans in East Asia. Here we test this proposition, consider the role of size-shape scaling, and more broadly assess the affinities of the Longlin 1 (LL1) cranium by comparing it to modern human and archaic hominin crania. The shape of LL1 is found to be highly unusual, but on balance shows strongest affinities to early modern humans, lacking obvious similarities to early East Asians specifically. We conclude that a scenario of hybridization with archaic hominins best explains the highly unusual morphology of LL1, possibly even occurring as late as the early Holocene. PMID:26202835

  5. Abrupt changes in North American climate during early Holocene times

    NASA Astrophysics Data System (ADS)

    Hu, F. S.; Slawinski, D.; Wright, H. E.; Ito, E.; Johnson, R. G.; Kelts, K. R.; McEwan, R. F.; Boedigheimer, A.

    1999-07-01

    Recent studies of the Greenland ice cores have offered many insights into Holocene climatic dynamics at decadal to century timescales. Despite the abundance of continental records of Holocene climate, few have sufficient chronological control and sampling resolution to compare with the Greenland findings. Butannually laminated sediments (varves) from lakes can provide high-resolution continental palaeoclimate data with secure chronologies. Here we present analyses of varved sediments from Deep Lake in Minnesota, USA. Trends in the stable oxygen-isotope composition of the sedimentary carbonate indicate a pronounced climate cooling from 8.9 to 8.3kyr before present, probably characterized by increased outbreaks of polar air, decreased precipitation temperatures, and a higher fraction of the annual precipitation falling as snow. The abrupt onset of this climate reversal, over several decades, was probably caused by a reorganization of atmospheric circulation and cooling of the Arctic airmass in summer that resulted from the final collapse of the Laurentide ice near Hudson Bay and the discharge of icebergs from the Quebec and Keewatin centres into the Tyrell Sea. The timing and duration of this climate reversal suggest that it is distinct from the prominent widespread cold snap that occurred 8,200 years ago in Greenland and other regions,,. No shifts in the oxygen-isotope composition of sediment carbonate occurred at 8.2kyr before present at Deep Lake, but varve thickness increased dramatically, probably as a result of increased deposition of aeolian dust. Taken together, our data suggest that two separate regional-scale climate reversals occurred between 9,000 and 8,000 years ago, and that they were driven by different mechanisms.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  9. Early mid-Holocene SST variability and surface-ocean water balance in the southwest Pacific

    NASA Astrophysics Data System (ADS)

    Duprey, N.; Lazareth, C. E.; CorrèGe, T.; Le Cornec, F.; Maes, C.; Pujol, N.; Madeng-Yogo, M.; Caquineau, S.; Soares Derome, C.; Cabioch, G.

    2012-12-01

    We present early mid-Holocene records of Sr/Ca,δ18O and δ18Osw from marine archives collected in Vanuatu: two Porites sp. corals (6.7-6.5 ka BP) and a Tridacna maxima giant clam (6.2-6.0 ka BP). Sr/Ca, δ18O, and δ18Osw were used as proxies for sea surface temperature (SST) and sea surface salinity (SSS). The fossil geochemical records were compared to modern Porites sp. and T. maxima records. Reconstructed mean SSTs from the two fossil Porites sp.and from the modern coral are similar, implying that the Western Pacific Warm Pool (WPWP)' southern edge had reached its modern location by 6.7-6.5 ka BP. The post-glacial SST rise in the Southwest Pacific was thus completed by the early mid-Holocene. The two early mid-Holocene corals and the giant clam recorded saltier conditions than modern related to 1) a decoupling between the precipitation regime and the SPCZ due to a northerly position of this climatic feature and 2) an increase of the moisture transport to the extra-tropics, driven by a strengthened or extended Hadley cell. The longestδ18O coral profile displays an El Niño Southern Oscillation (ENSO) signal reduced by 20-30% compared to the period 1928-1992, in concordance with the reduced ENSO variability observed in the Pacific area during the first half of the Holocene. However, the decoupling between the SPCZ and the precipitation regime may have also contributed to the weak ENSO signal recorded in the early mid-Holocene coralδ18O profile.

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

    PubMed

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

    2009-03-31

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

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

    NASA Technical Reports Server (NTRS)

    Kneller, Margaret; Peteet, Dorothy

    1997-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  13. Morphological and genetic evidence for early Holocene cattle management in northeastern China.

    PubMed

    Zhang, Hucai; Paijmans, Johanna L A; Chang, Fengqin; Wu, Xiaohong; Chen, Guangjie; Lei, Chuzhao; Yang, Xiujuan; Wei, Zhenyi; Bradley, Daniel G; Orlando, Ludovic; O'Connor, Terry; Hofreiter, Michael

    2013-01-01

    The domestication of cattle is generally accepted to have taken place in two independent centres: around 10,500 years ago in the Near East, giving rise to modern taurine cattle, and two millennia later in southern Asia, giving rise to zebu cattle. Here we provide firmly dated morphological and genetic evidence for early Holocene management of taurine cattle in northeastern China. We describe conjoining mandibles from this region that show evidence of oral stereotypy, dated to the early Holocene by two independent ¹⁴C dates. Using Illumina high-throughput sequencing coupled with DNA hybridization capture, we characterize 15,406 bp of the mitogenome with on average 16.7-fold coverage. Phylogenetic analyses reveal a hitherto unknown mitochondrial haplogroup that falls outside the known taurine diversity. Our data suggest that the first attempts to manage cattle in northern China predate the introduction of domestic cattle that gave rise to the current stock by several thousand years.

  14. Holocene climate and cultural evolution in late prehistoric-early historic West Asia

    NASA Astrophysics Data System (ADS)

    Staubwasser, Michael; Weiss, Harvey

    2006-11-01

    The precipitation climatology and the underlying climate mechanisms of the eastern Mediterranean, West Asia, and the Indian subcontinent are reviewed, with emphasis on upper and middle tropospheric flow in the subtropics and its steering of precipitation. Holocene climate change of the region is summarized from proxy records. The Indian monsoon weakened during the Holocene over its northernmost region, the Ganges and Indus catchments and the western Arabian Sea. Southern regions, the Indian Peninsula, do not show a reduction, but an increase of summer monsoon rain across the Holocene. The long-term trend towards drier conditions in the eastern Mediterranean can be linked to a regionally complex monsoon evolution. Abrupt climate change events, such as the widespread droughts around 8200, 5200 and 4200 cal yr BP, are suggested to be the result of altered subtropical upper-level flow over the eastern Mediterranean and Asia. The abrupt climate change events of the Holocene radically altered precipitation, fundamental for cereal agriculture, across the expanse of late prehistoric-early historic cultures known from the archaeological record in these regions. Social adaptations to reduced agro-production, in both dry-farming and irrigation agriculture regions, are visible in the archaeological record during each abrupt climate change event in West Asia. Chronological refinement, in both the paleoclimate and archaeological records, and transfer functions for both precipitation and agro-production are needed to understand precisely the evident causal linkages.

  15. Faunal reorganisation in terrestrial mammalian communities: evidence from France during the Lateglacial-Early Holocene transition

    NASA Astrophysics Data System (ADS)

    Bridault, Anne

    2010-05-01

    The Lateglacial-Early Holocene transition is characterized by rapid oscillations between warm and cold episodes. Their impact on ecosystem dynamics was particularly pronounced in north-western Europe where hunter-gatherer societies experienced a succession of environmental transformations, including the expansion and dispersal of biotic communities and changing herbivore habitats. Recent archaeozoological studies and AMS direct dating on mammalian bones/or bone collagen allow to map and precise this process at a supra-regional scale (France). At regional scales (i.e. Paris Basin & Jura-Northern French Alps), results indicate a rapid faunal reorganisation at the end of Lateglacial that will be presented in detail. Composition of faunal assemblages remains then unchanged during the Early Holocene. By contrast, significant herbivore habitat changes are recorded during the Early Holocene by other proxies (pollen data and isotopic data) and a decrease in Red Deer size through time is evidenced by osteometrical analyses. Hypotheses regarding the kind of adaptation process experienced by the faunal communities through time will be presented. Factors that may have controlled the observed changes will be discussed.

  16. Decadal-resolution early Holocene temperature and precipitation reconstruction near Disko Bugt, western Greenland

    NASA Astrophysics Data System (ADS)

    Thomas, E. K.; Castañeda, I. S.; Briner, J. P.; Schweinsberg, A.; Nguyen, K.; Salacup, J. M.

    2015-12-01

    Quantifying ice sheet responses to climate change is critical for predicting sea level rise in a warming world. In particular, increased precipitation may play an important role in offsetting ice sheet mass balance losses caused by rising temperatures. Past intervals of rapid climate change on human-relevant timescales provide natural experiments for quantifying ice sheet response to temperature and precipitation. During the early Holocene, western Greenland Ice Sheet retreat in the Disko Bugt region was punctuated by rapid and dramatic advances, likely in response to abrupt climate changes at 9.3 and 8.2 ka. The character of early Holocene decadal-scale temperature and precipitation changes in western Greenland remains unknown, however, so direct comparison of climate and ice sheet reconstructions currently is not possible. Leaf wax hydrogen isotopes reflect temperature and precipitation changes in the Arctic. We will present a decadal-resolution multiproxy record of early Holocene terrestrial temperature and precipitation using leaf wax hydrogen isotopes and other organic and inorganic proxies from a well-dated lake sediment sequence in the Disko Bugt region of western Greenland.

  17. Rapid vegetation response to Lateglacial and early Holocene climatic fluctuation in the South Carpathian Mountains (Romania)

    NASA Astrophysics Data System (ADS)

    Magyari, E. K.; Jakab, G.; Bálint, M.; Kern, Z.; Buczkó, K.; Braun, M.

    2012-03-01

    High-resolution pollen, conifer stomata and plant macrofossil analyses of two glacial lake sediments (1740 and 1990 m a.s.l.) are used to reconstruct Lateglacial (LG) and early Holocene (EH) vegetation and tree line changes in the Retezat Mountains. Our results show that during the LG, tree line was between 1750 and 1800 m a.s.l. formed by Larix decidua, Pinus mugo and Picea abies. Early LG spread to high altitudes suggests refugia of these tree species in the mountain. The Younger Dryas cooling resulted in regional steppe-tundra expansion, but tree line position and composition showed little change. The abundance of trees and shrubs decreased at 1740 m a.s.l., but species richness increased with the arrival of Pinus cembra. Our data support climate-model hindcasts for only modest decrease in accumulated growing season heat at mid-high altitudes. Regionally the pollen records suggest enhanced aridity and seasonality. In the EH, tree line reached 2000 m a.s.l. (higher than today) by ˜11,100 cal yr BP. P. mugo, P. cembra, P. abies established around the upper lake suggesting rapid increase in summer temperatures. The EH maximum of L. decidua between 11,200-10,600 cal yr BP was connected to high summer insolation. High altitude expansion of Abies alba between 10,600-10,300 cal yr BP suggested summer mean temperatures ˜2.8 °C higher then today. In comparison with other mountain sites in Europe, LG interstadial tree line was at similar altitude in the S Alps and ˜350 m higher in the Pirin Mountains. LG tree line fluctuation had similar low amplitude in the SE Alps, Retezat and Pirin Mts suggesting relatively weak influence of the North Atlantic thermohaline circulation changes on growing season temperatures.

  18. Early and mid-Holocene age for the Tempanos moraines, Laguna San Rafael, Patagonian Chile

    NASA Astrophysics Data System (ADS)

    Harrison, Stephan; Glasser, Neil F.; Duller, Geoff A. T.; Jansson, Krister N.

    2012-01-01

    Data about the nature and timing of Holocene events from the Southern Hemisphere, especially in southern South America, are required to provide insight into the extent and nature of past climate change in a region where land-based records are restricted. Here we present the first use of single grain Optically Stimulated Luminescence (OSL) dating of a moraine sequence recording glacial advance along the western side of the Patagonian Icefields. Dates from the Tempanos moraines at Laguna San Rafael (LSR) show that the San Rafael Glacier (SRG) advanced to maximum Holocene positions during the period 9.3 to 9.7 ka and at 5.7 ka. Outwash lying beneath the moraine in its northern portion, dated to 7.7 ka, indicates that the glacier front was also advanced at this time. Since these advances span both the regional early Holocene warm-dry phase (11.5 ka to 7.8 ka) and the subsequent cooling and rise in precipitation in the mid-late Holocene (since 6.6 ka) we infer that the advances of the SRG are not simply climate-driven, but that the glacier has also probably responded strongly to non-climatic stimuli such as internal ice dynamics and the transition between calving and non-calving. Many westwards-flowing glaciers in Patagonia were probably calving during much of the Late Pleistocene and Holocene, so we conclude that establishing robust glacial chronologies where climatic and non-climatic factors cannot be distinguished is likely to remain a challenge.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  20. Skeletal variation among early Holocene North American humans: implications for origins and diversity in the Americas.

    PubMed

    Auerbach, Benjamin M

    2012-12-01

    The movement of humans into the Americas remains a major topic of debate among scientific disciplines. Central to this discussion is ascertaining the timing and migratory routes of the earliest colonizers, in addition to understanding their ancestry. Molecular studies have recently argued that the colonizing population was isolated from other Asian populations for an extended period before proceeding to colonize the Americas. This research has suggested that Beringia was the location of this "incubation," though archaeological and skeletal data have not yet supported this hypothesis. This study employs the remains of the five most complete North American male early Holocene skeletons to examine patterns of human morphology at the earliest observable time period. Stature, body mass, body breadth, and limb proportions are examined in the context of male skeletal samples representing the range of morphological variation in North America in the last two millennia of the Holocene. These are also compared with a global sample. Results indicate that early Holocene males have variable postcranial morphologies, but all share the common trait of wide bodies. This trait, which is retained in more recent indigenous North American groups, is associated with adaptations to cold climates. Peoples from the Americas exhibit wider bodies than other populations sampled globally. This pattern suggests the common ancestral population of all of these indigenous American groups had reduced morphological variation in this trait. Furthermore, this provides support for a single, possibly high latitude location for the genetic isolation of ancestors of the human colonizers of the Americas.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    SciTech Connect

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

    1992-01-01

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

  3. Early Holocene pinyon ( Pinus monophylla) in the northeastern Great Basin

    NASA Astrophysics Data System (ADS)

    Madsen, David B.; Rhode, David

    1990-01-01

    Fine-grained excavation and analysis of a stratigraphic column from Danger Cave, northeastern Great Basin, suggests prehistoric hunter-gatherers were collecting and using singleleaf pinyon ( Pinus monophylla) near the site for at least the last 7500 yr. Human use of the cave began after the retreat of Lake Bonneville from the Gilbert level, shortly before 10,000 yr B.P. In stratum 9, culturally deposited pine nut hulls appear in the sequence by about 7900 yr B.P. and are continuously present thereafter. A hull fragment in stratum 10 is directly dated to 7410 ± 120 yr B.P. These dates are at least 2000 yr earlier than expected by extrapolation to macrofossil records from the east-central and central Great Basin, and necessitate some revision of current biogeographical models of late Quaternary pinyon migration.

  4. Early Holocene Meltwater Routing in the Labrador Sea

    NASA Astrophysics Data System (ADS)

    Jennings, A. E.; Pearce, C.; Andrews, J. T.; Hillaire-Marcel, C.; Seidenkrantz, M. S.; Lewis, M. C. F.

    2015-12-01

    The purpose of this study is to use the detrital carbonate (DC) records in sediment cores from the Labrador Sea western margin to study the spatial variability of the carbonate events and inferred sources and routing of glacial meltwater originating from Hudson Strait (HS) as well as potential contributions from Northern Baffin Bay (NBB) ice sheet margins. We use DC in sediment cores as a proxy for glacial meltwater and ice berg drift from these areas. More than 15 sediment cores with published DC, stable oxygen isotope, and radiocarbon stratigraphies provide the data for this study. Marine sediment core MD99-2236 from Cartwright Saddle is used as a template for freshwater forcing from HS outlet. Our hypothesis is that the complex interplay of current systems, shelf and slope bathymetry and location of meltwater and ice berg injection points will affect the spatial distribution of the DC events. In addition, differences in local ocean reservoir age for shelf, slope and open ocean sites may also contribute to offsets in the apparent ages of DC events. Identification of DC peaks also is influenced by sedimentation rates and sampling resolution. Quantitative x-ray diffraction is applied to differentiate the carbonate provenance between HS (calcite dominated) and NBB (dolomite dominated). To objectively correlate DC events, we study mostly published core data, removing all earlier assumptions about marine reservoir age and assess all core chronologies with their associated errors. Our results so far show that none of the DC events is found in all sites and no record captures all of the DC events. Despite this, some of the larger events occur in several records and are found along the entire Labrador margin allowing robust temporal and spatial mapping of the meltwater pathways. The end product will be a temporal and spatial reconstruction of meltwater and ice berg routing from HS and NBB outlets to the western N. Atlantic and serve as a contribution to modeling studies

  5. Iwo Eleru's place among Late Pleistocene and Early Holocene populations of North and East Africa.

    PubMed

    Stojanowski, Christopher M

    2014-10-01

    The Iwo Eleru site in Nigeria preserves the only terminal Pleistocene fossil from tropical West Africa. The peoples of this region contributed to significant population movements throughout the continent during the Holocene. As such, characterizing the phenotype of Late Pleistocene West African populations is critical for disentangling the evolutionary signatures of a highly complex African population history and structure. Previous research approached the calvaria's morphology from a paleoanthropological perspective, noting its mosaic of archaic and modern neurocranial features and distinctiveness from Pleistocene fossil taxa and contemporary modern human samples. In this paper, I compare Iwo Eleru with contemporary Late Pleistocene Africans and also consider the specimen's affinities with Holocene populations of the central and western Sahara, Nile Valley, and East Africa. Craniometric data were recorded for 22 neurocranial dimensions and subjected to principal components analysis and Mahalanobis distance estimation. Multidimensional scaling of distances indicated that Iwo Eleru fell outside the observed range of variation of other terminal Pleistocene supra-equatorial African populations, confirming previous results that documented its divergence from Neanderthals, Upper Paleolithic Europeans, and modern Africans. The calvaria was also distinct from Holocene Saharan, Nile Valley, and East African populations, which suggests limited West African input into the Sahara during the African Humid Period. Results presented here bolster previous research that suggested Iwo Eleru's anatomy reflected either admixture with archaic humans or the long-term survival of populations with more archaic neurocranial anatomy until the end of the Pleistocene.

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

    SciTech Connect

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

    2005-02-08

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

  7. Holocene faulting near closed landfill Pit 6, Lawrence Livermore National Laboratory Site 300

    SciTech Connect

    Carpenter, D.W.; Taffet, M.J.; Copland, J.R.; Mateik, R.S.; Wade, W.M.

    1992-02-01

    Lawrence Livermore National Laboratory`s Site 300 test facility, an 11 mi{sup 2} area, is located in the rugged, semiarid Altamont Hills southwest of Tracy, California. Geologic studies conducted at the site in support of environmental assessments of closed landfill Pit 6 reveal the presence of a fault strand showing evidence of repeated movements during late Pleistocene and Holocene time. These studies included airphoto interpretation, geologic mapping, and logging of four exploratory trenches and other exposures. The fault was traced from west of Pit 6 to southeast of the pit, a distance of about 1,500 ft; regional reconnaissance suggests that the fault extends beyond the limits of the area studied in detail. The identified fault strand is not coincident with any previously mapped fault. It occurs within a band of highly deformed Tertiary rocks that is bounded by the Carnegie fault on the north and the Corral Hollow fault on the south. Evidence of Holocene movement within the larger Corral Hollow-Carnegie fault zone indicates that this fault zone should be considered active and could be a source of future strong earthquake motion. Regressions relating total fault length, segment length, and fault plane area suggest that the Corral Hollow-Carnegie fault zone may be capable of generating an earthquake in the range of M{sub s} 6.3 to 7.1. Effects of a strong earthquake on closed landfill Pit 6 would be expected to be slight since the identified Holocene fault trace passes at least 100 ft south of the outer limits of the pit area. However, the effects of strong ground shaking from a local source upon buildings, slopes, and other structures within Site 300 and vicinity should receive further consideration.

  8. Holocene faulting near closed landfill Pit 6, Lawrence Livermore National Laboratory Site 300

    SciTech Connect

    Carpenter, D.W.; Taffet, M.J. ); Copland, J.R. ); Mateik, R.S.; Wade, W.M. )

    1992-02-01

    Lawrence Livermore National Laboratory's Site 300 test facility, an 11 mi[sup 2] area, is located in the rugged, semiarid Altamont Hills southwest of Tracy, California. Geologic studies conducted at the site in support of environmental assessments of closed landfill Pit 6 reveal the presence of a fault strand showing evidence of repeated movements during late Pleistocene and Holocene time. These studies included airphoto interpretation, geologic mapping, and logging of four exploratory trenches and other exposures. The fault was traced from west of Pit 6 to southeast of the pit, a distance of about 1,500 ft; regional reconnaissance suggests that the fault extends beyond the limits of the area studied in detail. The identified fault strand is not coincident with any previously mapped fault. It occurs within a band of highly deformed Tertiary rocks that is bounded by the Carnegie fault on the north and the Corral Hollow fault on the south. Evidence of Holocene movement within the larger Corral Hollow-Carnegie fault zone indicates that this fault zone should be considered active and could be a source of future strong earthquake motion. Regressions relating total fault length, segment length, and fault plane area suggest that the Corral Hollow-Carnegie fault zone may be capable of generating an earthquake in the range of M[sub s] 6.3 to 7.1. Effects of a strong earthquake on closed landfill Pit 6 would be expected to be slight since the identified Holocene fault trace passes at least 100 ft south of the outer limits of the pit area. However, the effects of strong ground shaking from a local source upon buildings, slopes, and other structures within Site 300 and vicinity should receive further consideration.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

    zhang, yurui; Renssen, Hans; Seppä, Heikki

    2016-04-01

    The early Holocene is an important climatological period, as it marked the final transition from the last deglaciation to the relatively warm and stable Holocene. Previous studies have analyzed the influence of the demise of the ice sheets and other forcings on the climate system during the Holocene. However, the climate response to the forcings together with the internal feedbacks before 9 ka remains not fully comprehended. In this study, we therefore disentangle how these forcings contributed to climate change during the earliest part of Holocene (11.5-7 ka) by employing the LOVECLIM climate model for both equilibrium and transient experiments. The results of our equilibrium experiments for 11.5 ka reveal that the annual mean temperature at the onset of the Holocene was lower than in the preindustrial era over most of the extratropical Northern Hemisphere. The magnitude of this cooler climate varies regionally and this spatial pattern is suggested by the biologically based proxies as well. In eastern N America and NW Europe the temperatures were 2-5 °C lower than in the preindustrial era as the climate was strongly influenced by the cooling effects of the ice sheets at here. This cooling of the ice-sheet surface was caused both by the enhanced surface albedo and by the orography of the ice sheets. In contrast, in Alaska, temperatures in all seasons were 0.5-3 °C higher than in the control run primarily due to the orbitally induced positive insolation anomaly and the enhanced southerly winds which advected warm air from the South as a response to the high air pressure over the Laurentide Ice Sheet (LIS). Our transient experiments indicate that the Holocene temperature evolution and the early Holocene warming were also geographically heterogeneous. In Alaska, the climate is constantly cooling over the whole Holocene. In contrast, in N Canada, there was an overall warming during the early Holocene up to 1.88 °C ka-1 in summer as a consequence of the progressive

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

    USGS Publications Warehouse

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

    1982-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    PubMed Central

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Zhang, Yurui; Renssen, Hans; Seppä, Heikki

    2016-05-01

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

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

    USGS Publications Warehouse

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

    2009-01-01

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

  19. A lacustrine record of early Holocene watershed events and vegetation history, Corvara in Badia, Dolomites (Italy)

    NASA Astrophysics Data System (ADS)

    Borgatti, Lisa; Ravazzi, Cesare; Donegana, Marta; Corsini, Alessandro; Marchetti, Mauro; Soldati, Mauro

    2007-02-01

    The early-middle Holocene lacustrine succession of Corvara in Badia (Italian Dolomites, 1521 m a.s.l.) records landslides and other watershed events before the onset of human pressure. The sensitivity of this archive to relate climate change, watershed processes and vegetation dynamics in the catchment has been explored through a stratigraphic study, including the analysis of sedimentological features, magnetic properties, palaeobotanical records and radiocarbon dating. A palaeolake existed between 10.1 k and 7 k cal. yr BP and was surrounded by a dense conifer forest. Long-term forest dynamics driven by ecological processes and by climatic conditions favourable to upward forest expansion is recorded throughout the pollen record. Within the fine clastic sedimentation, distinct layers enriched in organic debris of terrestrial origin have been attributed to instant events produced by mass movements. Their age fits the chronology of large landslide events already known in the catchment, enabling correlation of the field evidence of landslides with the lacustrine record. Landslide frequency is controlled by geological and structural factors, but it is significantly modulated by the centennial-millennial climatic phases that characterise the Holocene in the Alps. The taphonomical properties of pollen and macroremains provided valuable insight on the mechanism of watershed processes. Copyright

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  1. Stratigraphy and paleoenvironments of the early to middle Holocene Chipalamawamba Beds (Malawi Basin, Africa)

    NASA Astrophysics Data System (ADS)

    Van Bocxlaer, B.; Salenbien, W.; Praet, N.; Verniers, J.

    2012-05-01

    We describe the Chipalamawamba Beds, early to middle Holocene deposits at the southern margin of long-lived Lake Malawi. The beds are exposed because of downcutting of the upper Shire River. The Chipalamawamba sediments are medium to coarse, yellow to brown sands deposited in lenses varying in horizontal extent from a few meters to several hundreds of meters. Four units are recognized; the first three mainly contain lacustrine sediments deposited during lake high-stands about 10.6-9.7 cal ka BP (Unit 1), 7.6-6.5 cal ka BP (Unit 2) and 5.9-5.3 cal ka BP. Sediments of Unit 4 top units 1 to 3, are coarser and display regular foresets and oblique-bedding, suggesting deposition in riverine environments after installation of the Shire River (~5.0 ka BP). Freshwater mollusk assemblages and bioturbations regularly occur in the lacustrine sediments, but are largely absent from Unit 4. Diverse and often contradicting hypotheses on the lake levels of Lake Malawi have been proposed for the early and middle Holocene. The Chipalamawamba Beds allow straight-forward recognition of water levels and provide strong evidence for oscillating lake levels during this period, rather than continuous high or low levels. Sedimentation rates have been high and individual shell beds have typically been deposited during a few decades. Because the Chipalamawamba Beds contain a sequence of mollusk assemblages with intervals between subsequent shell beds ranging from a century to a few millennia, they enable paleontological analysis of the fauna with unusually high temporal resolution. That some mollusk lineages inhabiting Lake Malawi are in the early stages of diversification and radiation increases the paleobiological relevance of these beds.

  2. Stratigraphy and paleoenvironments of the early to middle Holocene Chipalamawamba Beds (Malawi Basin, Africa)

    NASA Astrophysics Data System (ADS)

    Van Bocxlaer, B.; Salenbien, W.; Praet, N.; Verniers, J.

    2012-11-01

    We describe the Chipalamawamba Beds, early to middle Holocene deposits at the southern margin of long-lived Lake Malawi. The beds are exposed because of downcutting of the upper Shire River. The Chipalamawamba sediments are medium to coarse, yellow to brown sands deposited in lenses varying in horizontal extent from a few meters to several hundreds of meters. Four units are recognized; the first three mainly contain lacustrine sediments deposited during lake high stands about 10.6-9.7 cal ka BP (Unit 1), 7.6-6.5 cal ka BP (Unit 2) and 5.9-5.3 cal ka BP (Unit 3). Sediments of Unit 4 overlay Units 1 to 3, are coarser and display regular foresets and oblique-bedding, suggesting deposition in riverine environments after installation of the Shire River (~ 5.5-5.0 ka BP). Freshwater mollusk assemblages and bioturbation regularly occur in the lacustrine sediments, but are largely absent from Unit 4. Diverse and often contradicting hypotheses on the lake levels of Lake Malawi have been proposed for the early and middle Holocene. The Chipalamawamba Beds allow straightforward recognition of water levels and provide strong evidence for oscillating lake levels during this period, rather than continuous high or low levels. Sedimentation rates have been high and individual shell beds have typically been deposited during a few decades. Because the Chipalamawamba Beds contain a sequence of mollusk assemblages with intervals between subsequent shell beds ranging from a century to a few millennia, they enable paleontological analysis of the fauna with an unusually high temporal resolution. That some mollusk lineages inhabiting Lake Malawi are in the early stages of diversification and radiation increases the paleobiological relevance of these beds.

  3. Paleoceanographic development in the SW Barents Sea during the Late Weichselian-Early Holocene transition

    NASA Astrophysics Data System (ADS)

    Aagaard-Sørensen, S.; Husum, K.; Hald, M.; Knies, J.

    2010-12-01

    The Late Weichselian-Early Holocene variability of the North Atlantic Current has been studied with focus on the zonal component of this meridional transport during the transition from glacial to interglacial conditions. The investigated sediment core is from 409 m water depth in the SW Barents Sea. Eight Accelerator mass spectrometry (AMS) 14C dates show that the core covers the last 20,000 cal yr B.P. with a centennial scale resolution during Late Weichselian-Early Holocene. Planktic foraminiferal assemblages were analyzed using the >100 μm size fraction and foraminiferal planktic and benthic δ 13C and δ 18O isotopes were measured. Furthermore, a range of physical and chemical analyses has been carried out on the bulk sediment samples. Four time periods have been identified which represent the varying oceanographic conditions in Ingøydjupet, a glacial trough located off the north coast of Norway in the SW Barents Sea. 1) The late glacial (before ca 15,000 cal yr B.P.) influenced by the nearby ice sheets with high amounts of sea ice- or iceberg-transported detritus. 2) The late Oldest Dryas stadial and the Bølling-Allerød interstadial (ca 15,000-12,700 cal yr B.P.) with cold surface water conditions influenced by the collapse of the nearby ice sheets, high amounts of sea ice- or iceberg-transported detritus and melt water and weak subsurface inflow of Atlantic Water. 3) The Younger Dryas cold stadial (12,700-11,650 cal yr B.P.) with low primary productivity and extensive sea ice cover and 4) The Preboreal and Early Holocene (11,650-6800 cal yr B.P. cal yr B.P.) with strong influx of Atlantic Water into the area, near absence of ice rafted debris and generally ameliorated conditions in both surface and bottom water masses as seen from a high flux of foraminifera and increased marine primary production.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  5. New insights into broad spectrum communities of the Early Holocene Near East: The birds of Hallan Çemi

    NASA Astrophysics Data System (ADS)

    Zeder, Melinda A.; Spitzer, Megan D.

    2016-11-01

    The Early Holocene in Near East was a pivotal transitional period that witnessed dramatic changes in climate and environment, human settlement, major changes in subsistence strategies focusing on a broad range of different plant and animal resources, and a radical restructuring of social relations. The remarkable corpus of avifauna from the Early Holocene site of Hallan Çemi in southeastern Turkey sheds new light on key issues about this dynamic period that has been termed the "Broad Spectrum Revolution". The avifauna from this important site demonstrate how Hallan Çemi occupants took advantage of the site's strategic location at the junction of multiple environmental zones by extracting a diverse range of seasonally available resources from both near-by and more distant eco-zones to cobble together a stable subsistence economy capable of supporting this small community throughout the year. They give testimony to the impacts of resource utilization over time, especially on species unable to rebound from sustained human hunting. At the same time, they show how Hallan Çemi residents mitigated these impacts by replacing depleted resources with alternative, more resilient ones that could be more sustainably harvested. They open a window onto the growing investment in feasting and ritual activity that helped bind this community together. In so doing they provide a means of empirically evaluating the efficacy of contrasting explanatory frameworks for the Broad Spectrum Revolution that gave rise to the subsequent domestication of plant and animals in the Near East. Contrary to frameworks that cast these developments as responses to resource depression, lessons learned from the Hallan Çemi avifauna lend support to frameworks that emphasize the human capacity to strategically target, capitalize, and improve upon circumscribed resource rich environments in a way that permits more permanent occupation of these niches. And they underscore the degree to which social and

  6. Lateglacial and early Holocene palaeoenvironmental 'events' in Sluggan Bog, Northern Ireland: comparisons with the Greenland NGRIP GICC05 event stratigraphy

    NASA Astrophysics Data System (ADS)

    Walker, Mike; Lowe, John; Blockley, Simon P. E.; Bryant, Charlotte; Coombes, Paul; Davies, Siwan; Hardiman, Mark; Turney, Chris S. M.; Watson, Jenny

    2012-03-01

    A multi-proxy Lateglacial environmental record is described from Sluggan Bog in County Antrim, Northern Ireland. Pollen, plant macrofossil, charcoal, sediment chemistry, stable isotope and sedimentological data provide a multi-faceted picture of local and regional environmental changes during the transition from the Last Cold Stage to the beginning of the present interglacial, and enable a series of distinctive palaeoenvironmental 'events' to be identified. A combination of radiometric and AMS radiocarbon dates on both humic and humin sediment fractions, and on charcoal fragments and plant macrofossils, provides one of the most closely-constrained radiocarbon timescales for any Lateglacial site in the British Isles. The evidence suggests that an initial period of warm conditions, beginning in the Sluggan record around 14.2 ka b2k (before AD 2000), and when open Salix-Betula woodland was locally present, was succeeded first by a heathland phase, then by a re-establishment of wood and scrub, before this was replaced during the later part of the Lateglacial (Woodgrange) Interstadial by species-rich grassland. In terms of timing, this sequence corresponds very closely to the GI-1e, GI-1d, GI-1c series of events in the Greenland NGRIP ice core. A short-lived Betula phase towards the end of the interstadial in the Sluggan sequence may reflect the short-lived climatic warming of GI-1a, although the radiocarbon age model suggests that it occurred prior to that event. There is a similar age discrepancy between the two sequences at the end of the interstadial with the onset of the Nahanagan (Younger Dryas) Stadial in Sluggan appearing to predate that in NGRIP by up to 200 yrs. By contrast, there is a very close correspondence between the date on the onset of the Holocene inferred from the pollen record in Sluggan (11.69 ka b2k) and the age of the Pleistocene-Holocene boundary (11.7 ka b2k) in NGRIP. While uncertainties remain over the climatic signals in the later

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

    PubMed

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

    2016-01-21

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

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

    PubMed

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

    2016-01-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Aceituno, Francisco J.; Loaiza, Nicolás

    2014-02-01

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

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Cremaschi, Mauro; Zerboni, Andrea

    2009-08-01

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

  14. 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.

  15. Early Holocene Change in Atmospheric Circulation in the North-Central USA

    NASA Astrophysics Data System (ADS)

    Dean, W. E.

    2005-12-01

    Numerous proxies in cores from Elk Lake, northwestern Minnesota, have provided a record of climatic and environmental change with annual resolution for the last 10,000 years. The proxies that allow reconstruction of the lake's physical and chemical paleolimnology (diatoms, redox-sensitive trace metals, and 18O values) show that that prior to about 8.2 cal ka the lake was a stable, dimictic lake that was strongly stratified. The same proxies show that after 8.2 cal. ka the lake was turbulent, well-mixed and shallower. The proxies that are related to climate factors external to the lake (dust as % Al and % Si, varve thickness, and pollen) show that prior to 8.2 cal. ka the lake was receiving relatively little dust, implying little wind activity. After 8.2 cal ka, there was a marked increase in the influx of dust indicating an increase in westerly winds. Lastly, the ostracode faunal assemblages, which provide information about the limnology and watershed characteristics, indicate that, for 1000 years prior to 8.2 cal. ka, the lake was stable and dilute with characteristics typical of lakes in boreal forests. At 8.2 cal. ka, the ostracode assemblage abruptly shifted to an assemblage typical of Canadian prairie lakes that exhibit large seasonal variability in physical characteristics. This marks the northward displacement of the polar front and beginning of westerlies. The Elk Lake record further shows that the so-called 8.2 cal. yr cold event, recognized in ice-core and other records from the circum-North Atlantic, and thought by some to be caused by catastrophic drainage of freshwater from proglacial lakes Agassiz and Ojibway, was but a brief manifestation of a more fundamental and lasting change in the climate of North America. This fundamental climate change was the result of changes in atmospheric circulation in response to marked changes in the relative proportions of land, water, and, especially, glacial ice in North America during the early Holocene, the

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    USGS Publications Warehouse

    Borchardt, G.; Lienkaemper, J.J.

    1999-01-01

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

  20. Reconstructing erosion distribution during the early Holocene Indian Summer Monsoon in the NW Himalaya

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    The Himalaya is a dynamic orogenic system characterized by rapid erosion and exhumation. Recent studies using detrital zircon fission track data, combined with geomorphic models informed by Tropical Rainfall Measuring Mission (TRMM) (Bookhagen and Burbank, 2006) data and thermal-kinematic models (e.g. Brewer and Burbank, 2006) show a strong correlation between regions of high precipitation and rapid erosion in the modern Himalaya. In order to unravel past patterns of erosion, we use detrital minerals from the Sutlej River in the NW Himalaya as tracers to investigate a spatial shift in the locus of erosion. Presently, the Indian Summer Monsoon (ISM) is responsible for over 80% of annual precipitation in the Himalaya and is the dominant erosional force on the range front. In the early-to-mid Holocene, the ISM is believed to have been much stronger, bringing larger amounts of rainfall to the range front and distributing rainfall farther into river valleys (Bookhagen et al., 2005; Goodbred and Kuehl, 2000), thus eroding a larger area. This study examines this spatial shift in erosion by using detrital zircon (U-Th)/He analysis in both modern bedload, and paleo-fluvial fill terrace sediments which were formed during the early Holocene strengthened ISM. Zircon (U-Th)/He thermochonology is used because i) it is a low temperature thermochronometer that is modeled to be sensitive enough to the landscape to yield a “cooling age gradient” across the Himalayan front, and ii) zircon is abundant in many rock types and resistant to chemical and mechanical weathering. We present 156 (U-Th)/He detrital grain-ages, from the modern-day Sutlej bedload (n=76) and an adjacent fluvial-fill terrace surface (n=80) dated ~8.5ka (Bookhagen et al., 2006). The probability density function (PDF) of the paleo-fluvial fill terrace population demonstrates a ~3-4 Ma older “peak-age” than the modern bedload population, implying a shift in the locus of maximum erosion and redistribution of

  1. Interactions between climate change and human activities during the early to mid-Holocene in the eastern Mediterranean basins

    NASA Astrophysics Data System (ADS)

    Berger, Jean-Francois; Lespez, Laurent; Kuzucuoğlu, Catherine; Glais, Arthur; Hourani, Fuad; Barra, Adrien; Guilaine, Jean

    2016-09-01

    This paper focuses on early Holocene rapid climate change (RCC) records in the Mediterranean zone, which are under-represented in continental archives (9.2 to 8.2 ka events) and on their impact on prehistoric societies. This lack of data handicaps the general interpretation of climate impacts on human societies, which flourished in recent years. Key questions remain about the impact of early Holocene cooling events on the Mediterranean climate, ecosystems and human societies. In this paper, we discuss some examples from river and lake systems from the eastern to central Mediterranean area (central Anatolia, Cyprus, northeastern and northwestern Greece) that illustrate some palaeohydrological and erosion variations that modified the sustainability of the first Neolithic populations in this region. Results allow us to present direct land-sea correlations and to reconstruct regional long-term trends as well as millennial- to centennial-scale climatic changes. In this context, we question the socio-economic and geographical adaptation capacities of these societies (mobility, technology, economic practices, social organisation) during the "early Holocene" interval (11.7 to 8.2 ka), which corresponds partly to the Sapropel 1 deposition in the eastern Mediterranean sea.

  2. Unexpected early extinction of the European pond turtle (Emys orbicularis) in Sweden and climatic impact on its Holocene range.

    PubMed

    Sommer, Robert S; Lindqvist, Charlotte; Persson, Arne; Bringsøe, Henrik; Rhodin, Anders G J; Schneeweiss, Norbert; Siroký, Pavel; Bachmann, Lutz; Fritz, Uwe

    2009-03-01

    Using ancient DNA sequences of subfossil European pond turtles (Emys orbicularis) from Britain, Central and North Europe and accelerator mass spectrometry radiocarbon dating for turtle remains from most Swedish sites, we provide evidence for a Holocene range expansion of the pond turtle from the southeastern Balkans into Britain, Central Europe and Scandinavia, according to the 'grasshopper pattern' of Hewitt. Northeastern Europe and adjacent Asia were colonized from another refuge located further east. With increasing annual mean temperatures, pond turtles reached southern Sweden approximately 9800 years ago. Until approximately 5500 years ago, rising temperatures facilitated a further range expansion up to Ostergötland, Sweden (approximately 58 degrees 30'N). However, around 5500 years ago pond turtle records suddenly terminate in Sweden, some 1500 years before the Holocene thermal maximum ended in Scandinavia and distinctly earlier than previously thought. This extinction coincides with a temporary cooling oscillation during the Holocene thermal maximum and is likely related to lower summer temperatures deteriorating reproductive success. Although climatic conditions improved later again, recolonization of Sweden from southern source populations was prevented by the Holocene submergence of the previous land connection via the Danish Straits that occurred approximately 8500 years ago.

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

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Renssen, H.; Seppä, H.

    2015-11-01

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

  4. Early Holocene dune activity linked with final destruction of Glacial Lake Minong, eastern Upper Michigan, USA

    NASA Astrophysics Data System (ADS)

    Loope, Henry M.; Loope, Walter L.; Goble, Ronald J.; Fisher, Timothy G.; Jol, Harry M.; Seong, J. C.

    2010-07-01

    The early Holocene final drainage of glacial Lake Minong is documented by 21 OSL ages on quartz sand from parabolic dunes and littoral terraces and one radiocarbon age from a lake sediment core adjacent to mapped paleoshorelines in interior eastern Upper Michigan. We employ a simple model wherein lake-level decline exposes unvegetated littoral sediment to deflation, resulting in dune building. Dunes formed subsequent to lake-level decline prior to stabilization by vegetation and provide minimum ages for lake-level decline. Optical ages range from 10.3 to 7.7 ka; 15 ages on dunes adjacent to the lowest Lake Minong shoreline suggest final water-level decline ˜ 9.1 ka. The clustering of optical ages from vertically separated dunes on both sides of the Nadoway-Gros Cap Barrier around 8.8 ka and a basal radiocarbon date behind the barrier (8120 ± 40 14C yr BP [9.1 cal ka BP]) support the hypothesis that the barrier was breached and the final lake-level drop to the Houghton Low occurred coincident with (1) high meltwater flux into the Superior basin and (2) an abrupt, negative shift in oxygen isotope values in Lake Huron.

  5. Climate and vegetation change during the late-glacial/early-Holocene transition inferred from multiple proxy records from Blacktail Pond, Yellowstone National Park, USA

    NASA Astrophysics Data System (ADS)

    Krause, Teresa R.; Whitlock, Cathy

    2013-05-01

    A series of environmental changes from late-glacial ice recession through the early Holocene are revealed in a 7000-yr-long record of pollen, charcoal, geochemistry, and stable isotopes from Blacktail Pond, a closed-basin lake in Yellowstone National Park. Prior to 11,500 cal yr BP, cool conditions dominated, fire activity was low, and alpine tundra and Picea parkland grew on the landscape. A step-like climate change to warm summer conditions occurred at 11,500 cal yr BP. In response, fire activity increased facilitating a transition from Picea parkland to closed Pinus forest. From 11,500 to 8280 cal yr BP, warm summers and abundant moisture mostly likely from high winter snowfall supported closed Pinus contorta forests. Cooler drier summer conditions prevailed beginning 8280 cal yr BP due to decreased summer insolation and winter snowpack, and lower parkland developed. The timing of vegetation change in the Blacktail Pond record is similar to other low- and middle-elevation sites in the northern Rocky Mountains during the late-glacial period, suggesting local plant communities responded to regional-scale climate change; however, the timing of vegetation changes was spatially variable during the early and middle Holocene due to the varying influences of strengthened summer monsoons and subtropical high on regional precipitation patterns.

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

    NASA Astrophysics Data System (ADS)

    Vos, Peter

    2013-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Blaschek, M.; Renssen, H.

    2012-04-01

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

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

    USGS Publications Warehouse

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

    2013-01-01

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

  9. 10Be dating reveals early-middle Holocene age of the Drygalski Moraines in central West Greenland

    NASA Astrophysics Data System (ADS)

    Cronauer, Sandra L.; Briner, Jason P.; Kelley, Samuel E.; Zimmerman, Susan R. H.; Morlighem, Mathieu

    2016-09-01

    We reconstruct the history of the Greenland Ice Sheet margin on the Nuussuaq Peninsula in central West Greenland through the Holocene using lake sediment analysis and cosmogenic 10Be exposure dating of the prominent Drygalski Moraines. Erratics perched on bedrock outboard of the Drygalski Moraines constrain local deglaciation to ∼9.9 ± 0.6 ka (n = 2). Three Drygalski Moraine crests yield mean 10Be ages of 8.6 ± 0.4 ka (n = 2), 8.5 ± 0.2 ka (n = 3), and 7.6 ± 0.1 ka (n = 2) from outer to inner. Perched erratics between the inner two moraines average 7.8 ± 0.1 ka (n = 2) and are consistent with the moraine ages. Sediments from a proglacial lake with a catchment area extending an estimated 2 km beneath (inland of) the present ice sheet terminus constrain an ice sheet minimum extent from 5.4 ka to 0.6 ka. The moraine chronology paired with the lake sediment stratigraphy reveals that the ice margin likely remained within ∼2 km of its present position from ∼9.9 to 5.4 ka. This unexpected early Holocene stability, preceded by rapid ice retreat and followed by minimum ice extent between ∼5.4 and 0.6 ka, contrasts with many records of early Holocene warmth and the Northern Hemisphere summer insolation maximum. We suggest ice margin stability may instead be tied to adjacent ocean temperatures, which reached an optimum in the middle Holocene.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  11. Vegetation response to early holocene warming as an analog for current and future changes: Special section

    USGS Publications Warehouse

    Cole, K.L.

    2010-01-01

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

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

    PubMed

    Cole, Kenneth L

    2010-02-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  19. Terminal Pleistocene—Early Holocene occupation in northeast Asia and the Zhokhov assemblage

    NASA Astrophysics Data System (ADS)

    Pitul'ko, Vladimir

    2001-01-01

    A knowledge of the history of ancient human occupation in the eastern Siberian Arctic differs distinctly from that of areas south of the Arctic Circle, where numerous sites are located (Fig. 1). A study of the latter provided a basis for a framework of cultural development, which was later applied to the archaeological materials of the arctic regions of eastern Siberia. Accordingly, the ideas on the chronology and the cultural interpretation of the northern sites are based essentially on the southern materials. The number of sites representing different stages of the Polar Stone Age is extremely small compared to that of the southern regions. If there are some dozens of Neolithic sites in the continental regions of the East Siberian Arctic, the early sites are significantly rare. Thus, there are very few sites presumed to be of the Dyuktai or Sumnagin culture, and the connection of these sites with the Late Paleolithic (or the Mesolithic) culture is rather questionable. The Late Pleistocene stage of human occupation of northeast Asia is considered to be related to a spreading and development of the Paleolithic Dyuktai culture.

  20. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

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

    USGS Publications Warehouse

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

    1999-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    USGS Publications Warehouse

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

    2002-01-01

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

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

    USGS Publications Warehouse

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

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

  7. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

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

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

    SciTech Connect

    Not Available

    1993-03-24

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

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

    1994-01-28

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

  10. 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.

  11. Regulatory Review of Early Site Permit Applications

    SciTech Connect

    Scott, Michael L.

    2004-07-01

    The U.S. Nuclear Regulatory Commission (NRC) has received and is reviewing three applications for early site permits (ESPs). The ESP process allows early resolution of site-related issues affecting possible construction and operation of a new nuclear power plant. The nuclear industry views a successful and predictable ESP process as an important step in assessing whether to seek authorization to construct and operate a new generation of nuclear power reactors in the United States. Because consideration of ESP applications is a first-of-a-kind activity, a number of issues have emerged prior to and during the reviews of the first three applications. Issues have included the need for design information at the ESP stage, accident analyses, quality assurance, and seismic analyses. The NRC has been working to resolve identified issues to support a Commission decision on whether to issue an ESP approximately 33-37 months after receipt of each ESP application. (authors)

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  13. Holocene radiocarbon-dated sites in northeastern Siberia: issues of temporal frequency, reservoir age, and human-nature interaction.

    PubMed

    Kuzmin, Yaroslav V

    2010-01-01

    The existing corpus of data on radiocarbon dates for Holocene sites in Northeastern Siberia was used as proxy to reconstruct the chronology of human occupation of the region. The problem of reservoir age correction in the Bering Sea region complicated this task and this issue needs to be solved in order to obtain more reliable age determinations for coastal archaeological sites. Using a chronology built after excluding the questionable dates from the database, the major patterns of human population dynamics and their possible correlation with climatic fluctuations were examined. No direct relationship appears to exist between these two processes. Additional archaeological and paleo environmental work needs to be carried out in this region of the North.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    USGS Publications Warehouse

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

    2002-01-01

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

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

    USGS Publications Warehouse

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

    1986-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

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

    USGS Publications Warehouse

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

    2014-01-01

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

  4. Cathodoluminescence of carbonate-cemented Holocene beachrock from the Togo coastline (West Africa): an approach to early diagenesis

    NASA Astrophysics Data System (ADS)

    Amieux, Pascal; Bernier, Paul; Dalongeville, Remi; Medwecki(de), Vincent

    1989-12-01

    Carbonate-cemented Holocene beachrock outcrops sporadically along more than 100 km of the Togo and Benin coasts. The sands are siliciclastic with subsidiary carbonate skeletal fragments and intraclasts. 14C radiometric dating indicates the sand deposits have formed within the last 5000 years. Beachrock has been indurated in phreatic environments undergoing, afterwards, several stages of burial and subaerial exposure. Cathodoluminescence (CL) proved a useful tool in unravelling the intricate cementation of this beachrock which can be subdivided into three stages. Firstly, magnesian calcite was precipitated in a marine-phreatic active zone. Very dull orange and very dull blue colours emitted in isopachous rims of needle-like crystals and peloidal micrite (CL1-fabric) reveal different Eh and pH precipitating conditions in this environment. Secondly, bright yellow-orange luminescing acicular and equant spar cement (CL2-fabric) is interpreted to have formed in a mixed-water phreatic zone. The third stage of cementation occurred dominantly in the landward part of the beachrock and accompanied neomorphism of the earlier marine cements. The resultant CL3-fabric, dull blue, medium orange luminescing equant spar is typical of continental fresh-water phreatic zones. The progression from marine to fresh-water pore fillings accompanied sand-bar progradation during a stable sea-level stage. Ultimately there was erosion stage of the sand-bar deposits which led to subaerial exposure and partial erosion of the beachrock. Recognition of the effects of repeated shoreline progradation during the early diagenesis of this Holocene beachrock indicates the potential value of diagenetic studies in aiding recognition of marine regressions and transgressions in the geological record.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  6. The impact of early Holocene Arctic shelf flooding on climate in an atmosphere-ocean-sea-ice model

    NASA Astrophysics Data System (ADS)

    Blaschek, M.; Renssen, H.

    2013-11-01

    Glacial terminations are characterized by a strong rise in sea level related to melting ice sheets. This rise in sea level is not uniform all over the world, because regional effects (uplift and subsidence of coastal zones) are superimposed on global trends. During the early Holocene the Siberian Shelf became flooded before 7.5 ka BP and the coastline reached modern-day high stands at 5 ka BP. This area is currently known as a sea-ice production area and contributes significantly to the sea-ice exported from the Arctic through the Fram Strait. This leads to the following hypothesis: during times of rising sea levels, shelves become flooded, increasing sea-ice production on these shelves, increasing sea-ice volume and export through the Fram Strait and causing the sea-ice extent to advance in the Nordic Seas, yielding cooler and fresher sea surface conditions. We have tested this hypothesis in an atmosphere-ocean-sea-ice coupled model of intermediate complexity (LOVECLIM). Our experiment on early Holocene Siberian Shelf flooding shows that in our model sea-ice production in the Northern Hemisphere increases (15%) and that sea-ice extent in the Northern Hemisphere increases (14%) but sea-ice export decreases (-15%) contrary to our hypothesis. The reason of this unexpected behaviour has its origin in a weakened polar vortex, induced by the land-ocean changes due to the shelf flooding, and a resulting decrease of zonality in the Nordic Seas pressure regime. Hence the winter Greenland high and the Icelandic low strengthen, yielding stronger winds on both sides of the Nordic Seas. Increased winds along the East Greenland Current support local sea-ice production and transport towards the South, resulting in a wider sea-ice cover and a southward shift of convection areas. The overall strength of the Atlantic meridional overturning circulation is reduced by 4% and the heat transport in the Atlantic basin by 7%, resulting in an annual cooling pattern over the Nordic Seas by

  7. The impact of early Holocene Arctic Shelf flooding on climate in an atmosphere-ocean-sea-ice model

    NASA Astrophysics Data System (ADS)

    Blaschek, M.; Renssen, H.

    2013-07-01

    Glacial terminations are characterized by a strong rise in sea level related to melting ice sheets. This rise in sea level is not uniform all over the world, because regional effects (uplift and subsidence of coastal zones) are superimposed on global trends. During the early Holocene the Siberian Shelf became flooded before 7.5 ka BP and the coastline reached modern-day high stands at 5 ka BP. This area is currently known as a sea-ice production area and contributes significantly to the sea-ice exported from the Arctic through the Fram Strait. This leads to the following hypothesis: during times of rising sea levels, shelves become flooded, increasing sea-ice production on these shelves, increasing sea-ice volume and export through Fram Strait and causing the sea-ice extent to advance in the Nordic Seas, yielding cooler and fresher sea surface conditions. We have tested this hypothesis in an ocean-sea-ice-atmosphere coupled model of intermediate complexity (LOVECLIM). Our results of an early Holocene Siberian Shelf flooding show that in our model the Northern Hemisphere sea-ice production is increased (15%) and that the Northern Hemisphere sea-ice extent increases (14%) contrary to our hypothesis with lower sea-ice export through Fram Strait (-15%). The reason of this unexpected behaviour has its origin in a weakened polar vortex, induced by the land-ocean changes due to the shelf flooding, and a resulting decrease of zonality in the Nordic Seas pressure regime. Hence the winter Greenland high and the Icelandic low strengthen, yielding stronger winds on both sides of the Nordic Seas. Increased winds along the East Greenland Current support local sea-ice production and transport towards the south, resulting in a wider sea-ice cover and a southward shift of convection areas. The overall strength of the Atlantic Meridional Overturning Circulation is reduced by 4% and the heat transport in the Atlantic basin by 7%, resulting in an annual cooling pattern over the Nordic

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

    USGS Publications Warehouse

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    PubMed Central

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

    2015-01-01

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

  11. The PUFA-enriched fatty acid profiles of some frozen bison from the early Holocene found in the Siberian permafrost.

    PubMed

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

    2015-01-21

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

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

    Code of Federal Regulations, 2012 CFR

    2012-01-01

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

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

    Code of Federal Regulations, 2011 CFR

    2011-01-01

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

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

    Code of Federal Regulations, 2014 CFR

    2014-01-01

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

  15. Holocene Vegetation and Climate History of the Northern Bighorn Basin, Southern Montana

    NASA Astrophysics Data System (ADS)

    Lyford, Mark E.; Betancourt, Julio L.; Jackson, Stephen T.

    2002-09-01

    Records of Holocene vegetation and climate change at low elevations (<2000 m) are rare in the central Rocky Mountain region. We developed a record of Holocene vegetation and climate change from 55 14C-dated woodrat middens at two low-elevation sites (1275 to 1590 m), currently vegetated by Juniperus osteosperma woodlands, in the northern Bighorn Basin. Macrofossil and pollen analyses show that the early Holocene was cooler than today, with warming and drying in the middle Holocene. During the Holocene, boreal ( Juniperus communis, J. horizontalis) and montane species ( J. scopulorum) were replaced by a Great Basin species ( J. osteosperma). J. osteosperma colonized the east side of the Pryor Mountains 4700 14C yr B.P. Downward movement of lower treeline indicates wetter conditions between 4400 and 2700 14C yr B.P. Increased aridity after 2700 14C yr B.P. initiated expansion of J. osteosperma from the east to west side of the Pryor Mountains.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  17. Early Holocene catastrophic mass-wasting event and fan-delta development on the Hua-tung coast, eastern Taiwan

    NASA Astrophysics Data System (ADS)

    Hsieh, Meng-Long; Liew, Ping-Mei; Chen, Hua-Wen

    2011-11-01

    Landslides and debris flows rarely occurred during historical times in the tectonically active Coastal Range of eastern Taiwan. This topographic stability, however, contrasts greatly with the widespread existence of terraced alluvial fans and fan-deltas on the Hua-tung coast which fringes the range. This study focuses on the two largest fan-terrace systems on the Hua-tung coast, both of which consist of alluvial fans (plane-view areas up to 8 km 2) larger than their contributing catchments. Stratigraphic data show that both systems were in sandy, wave-dominated settings during de-glacial times. The systems were then disturbed by a catastrophic landslide/debris-flow event (or events), which brought enormous amounts of gravel (Facies Gm) into the systems, deforming previously-deposited marine sands (Facies Sm) and shallowing the seafloor. The combined Gm/Sm complex yields multiple radiocarbon dates ranging from 11.3 to 8.3 ka cal BP, with a cluster around 8.6 ka cal BP. This mass-wasting event has been unique since the emergence of its contributing catchment 0.2-0.3 Ma ago. The low frequency of such an event could reflect the great resistance of rock mass in the source areas to weathering and erosion. The common blockage of valley floors by giant-boulder piles, which limits channel incision and sediment transport, could also increase the apparent stability of the mountain. The trigger of landslides in the Coastal Range has been linked to large earthquakes. Additionally, we propose that the great magnitude and duration of the observed early Holocene event were caused by the contemporaneous prolonged rainfall (and/or high frequency of typhoons) associated with the East Asian summer monsoon maximum.

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

    PubMed Central

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

    2015-01-01

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

  19. 10 CFR 52.24 - Issuance of early site permit.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS... planning, are necessary and sufficient, within the scope of the early site permit, to provide reasonable... required by subpart A of 10 CFR part 51 have been made. (b) The early site permit must specify the...

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

    NASA Astrophysics Data System (ADS)

    Yu, Zicheng

    2000-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Hudak, Curtis M.

    1984-05-01

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

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

    USGS Publications Warehouse

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

    2008-01-01

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

  4. Attractiveness of the landscape: Reconstruction of Early to Middle Holocene landscape and occupation history of Flevoland (central Netherlands)

    NASA Astrophysics Data System (ADS)

    Van den Biggelaar, Don; Kluiving, Sjoerd; Van Balen, Ronald; Kasse, Kees; Kolen, Jan

    2013-04-01

    The onset of the Holocene (11 500 BP) is marked by climate warming. Climate warming induced the growth of vegetation, which in combination with precipitation and a long period of non-deposition resulted in the formation of soils at the top of the Pleistocene deposits. As these soils have been present at the surface in Flevoland (central Netherlands) during most of the Mesolithic and Neolithic period, the top Pleistocene is an important archaeological level. Prior to the 1990s, prehistoric occupation in wetland areas, such as the Flevoland region, was seen as a challenging living environment due to its marginal nature. However, since the early 1990s a different approach was raised concerning the suitability of wetland occupation by Mesolithic and Neolithic people. Instead of adapting to the natural conditions, prehistoric people selected an area suitable to their way of life. The question remains why it took so long (Mesolithic-Neolithic transition period: 5300-4600 cal BC) for the inhabitants of the Lower Rhine Basin to adapt to the Neolithic lifestyle, in contrast to the adaptation in the loess zone and later in Britain. This difference in adaptation of the Neolithic lifestyle during this transition period cannot be solely explained by a difference in attitude or other cultural arguments. As postglacial sea-level rise caused large parts of Flevoland (central Netherlands) to inundate during the Late Mesolithic and Early Neolithic, the availability of natural resources also changed. It is hypothesized that the availability of a wide range of natural resources, and not exclusively the soil type, predominantly determined the suitability and attractiveness of a region for hunter/gatherers and therefore delayed the transition to a Neolithic lifestyle. To test this hypothesis we have compared two selected areas on the basis of the following parameters: elevation, slope gradient relative to sea-level rise, soil type, past vegetation and the number of archaeological

  5. Reconstruction of the past flow channels in the early Holocene at Lake Tonle Sap, Cambodia

    NASA Astrophysics Data System (ADS)

    Haraguchi, T.; Yonenobu, H.; Tokunaga, T.; Shimoda, I.

    2013-05-01

    Lake Tonle Sap is located at the central part of Cambodia, South-East Asia. In rainy season, the water body swells with the water depth accordingly increasing from 1 up to 10 meters due to a pulsive intrusion from the Mekong River. The lake is therefore a vital reservoir that protects the region from flooding. It is paleolimnologically important to better understand how the lake has gained the function controlling water balance of this region. We undertook an extensive echo-sounding exploration at the lake in order to clarify the subsurface structure of Lake Tonle Sap. The survey was conducted in rainy seasons from 2009 to 2012. Sediment cores were collected at three sites at the middle part of the lake. Echo sounding was undertaken over the whole part of the lake using a single-channel sub-bottom profiling system (Stratabox, SyQwest Inc.). A prominent sound frequency of 10 KHz was selected in order to observe structure of reflectance planes up to the 40-m depth. In consequence, we discovered deposited valleys forming a complex network of past flow channels. The subsurface structure of the lake bed was mostly complacent showing a strongly reflecting plane observed at the depth of 1-2 meters; the sediments mainly consisted of mud. A number of valley-shaped reflecting planes were observed at the depth of 10-14 meters. Radiocarbon dates of carbonaceous materials collected at the vally bottom were around 10 ka calBP. A 3-D reconstruction presented a complex network of deposited flow channels.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  10. Late Glaciation to early Holocene records of climatic and vegetation changes from Onepoto Crater, Auckland New Zealand: a biomarker and isotopic approach

    NASA Astrophysics Data System (ADS)

    Sikes, E. L.; Medeiros, P. M.; Makou, M. C.; Augustinas, P.

    2007-12-01

    A core taken from Onepoto Crater, a maar lake from the Auckland region of New Zealand, has excellent stratigraphy and robust age control based on well-dated and chemically distinguishable fallout tephra from the Taupo Volcanic Zone (TVZ). We present here a multi-proxy record including biomarkers and compound-specific isotopes on fatty acids that document ecological and climatological changes from the last glaciation to the early Holocene in northern New Zealand. All proxies indicate a drier and cooler climate in the glaciation followed by a rapid shift to warmer and wetter conditions at 17.6 ka that persisted until the early Holocene. The inferred arid conditions in the early part of the record are supported by markers such as charcoal abundances, but charcoal is absent after the climatic shift at 17.6 ka. New records of biomarkers and compound-specific isotopes on fatty acids from Onepoto Crater clarify changes in aridity associated with the glacial to interglacial climate shift documented by other proxies such as charcoal and pollen. Elevated abundances of marker lipids derived from biomass burning, such as dehydroabietic acid (a proxy for forest fires and by implication, aridity) and decreased 13C in terrestrially derived fatty acids indicate a return to somewhat dryer conditions during the Antarctic Cold Reversal (ACR) not present in other proxy records. The biomarker and isotopic data suggest drier conditions in the ACR that were not as intense as in the glaciation and remain unresolved by other proxies.

  11. The Hanford Site: An anthology of early histories

    SciTech Connect

    Gerber, M.S.

    1993-10-01

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

  12. Early Man Site Found in Highland Ecuador.

    PubMed

    Mayer-Oakes, W J; Bell, R E

    1960-06-17

    Field investigations in Ecuador have produced archeological evidence for the occupation of the northern Andes by early nomadic hunters. Surface collections and test excavations have demonstrated a complex of stone tools with typological relationships to level I at Fell's Cave in southern Chile, and technological relationships to the late Pleistocene "fluted point" complexes of North America. The date of these materials is estimated at 7000 to 8000 B.C.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  15. From climate change to diet change - biochemistry investigations on Late Glacial and Early Holocene brown bear remains from caves in the Alpine region

    NASA Astrophysics Data System (ADS)

    Döppes, Doris; Rosendahl, Wilfried; Pacher, Martina; Bocherens, Hervé

    2010-05-01

    Bones of brown bears from caves in the Alpine region in Germany, Austria, Italy and Switzerland were examined and dated in the last years. The finds originate from the transition from the Bölling/Alleröd to the Early Holocene. In total we analyzed 15 samples from bones and teeth of directly radiocarbon dated brown bears from the alpine region for isotopic analyses. All collagen considered here exhibit carbon and nitrogen content similar to that of collagen extracted from fresh bones, and most of the bones and teeth contained almost the same quantity of collagen than fresh bone (around 25% weight). Atomic C/N ratios range from 3.1 to 3.4, well within the acceptable range (2.9-3.6). The d13C values are rather high during the Late Glacial then a clear decrease is observed at the beginning of the Holocene. This trend coincides with the development of dense forests at low altitudes and the shift of timberline towards higher altitudes. The d15N values are relatively low in Bölling-Alleröd, then quite high during the Younger Dryas, and they decrease again during the Boreal and more recent periods. For the first time a more precise picture of the former habitat of the brown bears during the transition from the Bölling/Alleröd to the Early Holocene in the Alpine region could be reconstructed. The described investigation can also give an outlook of the coexistence of the herbivore cave bears and the omnivore/carnivore brown bears during the late Upper Pleistocene.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  17. A revised Holocene geochronology for the Lower Mississippi Valley

    NASA Astrophysics Data System (ADS)

    Kesel, Richard H.

    2008-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  20. Lateglacial and Early Holocene vegetation history of the northern Wetterau and the Amöneburger Basin (Hessen), central-west Germany.

    PubMed

    Bos, J A.A.

    2001-06-01

    The Lateglacial and Early Holocene vegetation history of the northern Wetterau and Amöneburger Basin, two intra-montane basins in Hessen, central-west Germany, is reconstructed by means of pollen and macrofossil analyses. Regional pollen assemblage zones are defined for the Lateglacial and Early Holocene. After calibration of the radiocarbon dates and establishment of age/depth relationships, the ages of the pollen zone boundaries are calculated. The regional vegetation changes correlate closely with the major fluctuations in the delta18O curve of the Greenland ice cores spanning the same time period. During the early Lateglacial, the open herbaceous vegetation with dwarf shrubs in the northern Wetterau was replaced by woodlands. Initially these woodlands consisted of birch, but after the immigration of pine, mixed forests of pine and birch developed. Soon after its immigration pine became dominant and pine woodlands largely replaced the birch forests. Only on the locally wetter substrates of the river floodplain did Betula stands persist. Gradually the importance of herbaceous communities declined and the pine woodlands lost their open character. During the Lateglacial two regressive phases in the vegetation succession are reflected in the data which are equated with the Older- and Younger Dryas biozones. At the beginning of the Younger Dryas, the forest-limit was lowered and the importance of herbaceous communities increased. Later, pine woodlands thinned and Ericales became part of the vegetation, indicating the development of more acid, nutrient-poor soils. A subdivision of the Younger Dryas biozone into a wetter, colder first part and a drier, warmer second part is suggested. At the beginning of the Early Holocene, pine woodlands became more closed and soils more stabilised. The transition between the Younger Dryas and Preboreal biozones is indicated by a lithological change to organic (-rich) deposits. Betula stands persisted on the locally wetter substrates

  1. Holocene, subrecent and contemporary source-to-sink fluxes in a valley-fjord system, Erdalen and Bødalen site project (SedyMONT - Norway)

    NASA Astrophysics Data System (ADS)

    Beylich, Achim A.

    2010-05-01

    The focus of this ESF-NFR funded Norwegian Individual Project (IP5, 2008-2013) within the European Science Foundation (ESF) SedyMONT (EUROCORES TOPO-EUROPE) Programme (http://www.esf.org/topoeurope) is on Holocene, subrecent and contemporary sedimentary fluxes and budgets in the Erdalen and Bødalen catchments in Nordfjord, western Norway (http://www.ngu.no/sedymont). The innovative approach of this research project is the integrated quantitative study of longer-term (Holocene), subrecent and contemporary source-to-sink fluxes and process rates using a novel combination of advanced methods and techniques. With respect to the main aims and objectives of ESF SedyMONT, the following main aims of the Erdalen and Bødalen site project can be stressed: - Analyse how the inheritance of the landscape due to the influence of the Last Glacial Maximum (LGM) has affected process rates over time (paraglacial system), - Document changes in process rates over different timescales by combining quantitative knowledge on Holocene process rates with newly generated data on subrecent and contemporary process rates. Monitoring of surface processes in Erdalen and Bødalen, in combination with repeated analyses of surface water chemistry, atmospheric solute inputs and granulometric analyses of suspended sediments provide high-resolution data to analyse and quantify present-day sedimentary and solute fluxes as well as sediment sources, denudation rates, and meteorological and topographic / landscape morphometric controls of denudative processes. In addition to standard methods for monitoring bedload transport, innovative techniques like impact sensors, PIT tags and biofilm analysis are applied to analyse channel stability / mobility and to estimate bedload transport rates in both valleys. The volume and composition of lake sediments are studied using echo-sounder, georadar and different coring techniques. Investigations on volumes and architecture of storage elements (talus cones, valley

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

    USGS Publications Warehouse

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

    2014-01-01

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

  3. 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

  4. Holocene Palaeoenvironment on Kamchatka

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

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

    1992-01-01

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

  9. 88. Overhead view of clear air station site at early ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    88. Overhead view of clear air station site at early stage of construction. View is from south 30 degrees west showing DR 3 in foreground with DR 2 in middle and DR 1 out of view. Official photograph BMEWS Project by unknown photographer, 5 October, 1959, Photographic Services, Riverton, NJ, BMEWS, clear as negative no. A-27. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

  10. Stepwise transition from deglacial/Early Holocene to modern-like conditions in the eastern Fram Strait, sub-Arctic north, inferred from planktic foraminifer fauna and sea surface temperatures

    NASA Astrophysics Data System (ADS)

    Werner, K.; Spielhagen, R. F.; Kandiano, E.; Hass, H. C.

    2012-04-01

    The heat content of the Arctic Ocean is mainly controlled by the inflow of north-heading warm and saline Atlantic Water through eastern Fram Strait. The eastern Fram Strait is therefore ice-free all year, opposite to its perennially ice-covered western part where large amounts of Arctic sea ice are exported year-round to the Nordic Seas. The Early and Mid-Holocene phases (ca 12 to 5 cal ka BP) in the (sub-)Arctic have been especially marked not only by high summer insolation but also by rising sea level and the final disintegration of large ice sheets that had been established during the preceding glacial phase. Two sediment cores with multidecadal resolution from the Western Svalbard margin have been investigated for its planktic foraminiferal distribution, sea surface temperatures, planktic and benthic stable isotope ratios, and lithological parameters to derive information on the Holocene variability of the heat transport to the Arctic Ocean and related fluctuations of the marginal ice zone in the eastern Fram Strait. Planktic foraminifer fauna and a summer sea surface temperature reconstruction based on the modern analogue technique imply a stepwise transition from deglacial/Early Holocene to modern-like conditions in the eastern Fram Strait. Repeated short-term advances of the sea ice margin accompanied the generally strong heat transport to the Arctic Ocean during the Early to Mid-Holocene. Consistent with the decreasing solar insolation, cooler (sub-)surface conditions established after ca 5 cal ka BP most likely related to both a weakening of the Atlantic Water inflow and strong export of Arctic sea ice through Fram Strait. The Late Holocene Neoglacial phase was characterized by high contents of ice-rafted material and dominance of the cold water-indicating planktic foraminifer species Neogloboquadrina pachyderma. Cool Late Holocene conditions are reversed by a strong warming event likely caused by a significant strengthening of Atlantic heat advection to

  11. Some early astronomical sites in the Kashmir region

    NASA Astrophysics Data System (ADS)

    Iqbal, Naseer; Vahia, M. N.; Masood, Tabasum; Ahmad, Aijaz

    2009-03-01

    We discuss a number of early rock art sites in the Kashmir Valley in northern India and neighbouring Pakistan, and suggest that some of these contain depictions of astronomical objects or events. The sites are in the Srinagar and Sopore regions and in or near the Ladakh region, and date to Neolithic or Upper Paleolithic times. Our studies suggest that during this period some of the ancient astronomers recorded supernovae, meteorite impacts, the Sun, the Moon and the seasons in their rock art.

  12. Early and late surgical site infections in ear surgery.

    PubMed

    Bastier, P L; Leroyer, C; Lashéras, A; Rogues, A-M; Darrouzet, V; Franco-Vidal, V

    2016-04-01

    A retroauricular approach is routinely used for treating chronic otitis media. The incidence of surgical site infections after ear surgery is around 10% in contaminated or dirty procedures. This observational prospective study describes surgical site infections after chronic otitis media surgery with the retroauricular approach and investigated their potential predictive factors. This observational prospective study included patients suffering from chronic otitis media and eligible for therapeutic surgery with a retroauricular approach. During follow-up, surgical site infections were defined as "early" if occurring within 30 days after surgery or as "late" if occurring thereafter. The data of 102 patients were analysed. Concerning early surgical site infections, four cases were diagnosed (3.9%) and a significant association was found with preoperative antibiotic therapy, wet ear at pre-operative examination, class III (contaminated) in the surgical wound classification, NNIS (National Nosocomial Infection Surveillance) index > 1, and oral post-operative antibiotic use. Seven late surgical site infections were diagnosed (7.1%) between 90 and 160 days after surgery and were significantly correlated to otorrhoea during the 6 months before surgery, surgery duration ≤60 minutes, canal wall down technique and use of fibrin glue. Surgical site infections after chronic otitis media surgery seem to be associated with factors related to the inflammatory state of the middle ear at the time of surgery in early infections and with chronic inflammation in late infections.

  13. Prompt transgression and gradual salinisation of the Black Sea during the early Holocene constrained by amino acid racemization and radiocarbon dating

    NASA Astrophysics Data System (ADS)

    Nicholas, William Anthony; Chivas, Allan R.; Murray-Wallace, Colin V.; Fink, David

    2011-12-01

    The restricted environment of the Black Sea is particularly sensitive to climatic and oceanographic fluctuations, owing to its connection with the Mediterranean Sea via the narrow Bosphorus Strait. The exact mechanism and timing of the most recent connection between these water bodies is controversial with debate on the post-glacial history of the Black Sea being dependent on radiocarbon dating for numerical ages. Here we present new 23 accelerator mass spectrometer (AMS) radiocarbon ages on peat and bivalve molluscs, supported by the first amino acid racemization (AAR) dating of bivalve molluscs ( n = 66) in the Black Sea. These data indicate infilling of the Black Sea during the early Holocene from an initial depth 107 m below sea-level, and 72 m below that of the Bosphorus Sill. These data combined with a review of previous radiocarbon ages has enabled a unique perspective on the post-glacial Black Sea. A sea-level curve based on conventional and AMS radiocarbon ages on peat and AMS-based ages on Dreissena sp. shells indicate the water-level in the earlier lake phase continued, until the early Holocene, to be lower than the Bosphorus Sill after the Younger Dryas ended. However, the absence of AMS-dated mollusc ages from the shelves of this basin older than the Younger Dryas is suggestive of sub-aerial exposure of the shelves, and comparatively lower water-levels when the Younger Dryas began. Thus post-glacial outflow from the Black Sea occurred through a lowered or open Bosphorus seaway. Basin-wide radiocarbon ages on peat indicate a prompt increase in water-level from that of the pre-existing and unconnected palaeo-lake during the earliest Holocene (9600-9200 cal a BP). Mass colonisation of the Black Sea by Mediterranean taxa did not occur until salinity had risen sufficiently, a process which took 1000 a or more from the initial transgressive event. This gradual change in salinity contrasts with the prompt transgression which would have taken ˜400 a to occur.

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

    USGS Publications Warehouse

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

    1977-01-01

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

  15. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 2 2011-01-01 2011-01-01 false Transfer of early site permit. 52.28 Section 52.28 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS... permit will be processed under 10 CFR 50.80....

  16. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 2 2010-01-01 2010-01-01 false Transfer of early site permit. 52.28 Section 52.28 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS... permit will be processed under 10 CFR 50.80....

  17. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 2 2012-01-01 2012-01-01 false Transfer of early site permit. 52.28 Section 52.28 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS... permit will be processed under 10 CFR 50.80....

  18. 10 CFR 52.28 - Transfer of early site permit.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 2 2014-01-01 2014-01-01 false Transfer of early site permit. 52.28 Section 52.28 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS... permit will be processed under 10 CFR 50.80....

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

    SciTech Connect

    Not Available

    1993-01-27

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

  20. Holocene Lake Productivity and Inferred Climate Histories From High-Altitude Sites Within the Baroon Taiga Mountains, Northern Mongolia

    NASA Astrophysics Data System (ADS)

    Robinson, K. D.; Rosenmeier, M. F.; Ortiz, J. D.

    2007-12-01

    Diffuse reflectance spectroscopy, biogenic silica, and standard loss-on-ignition (LOI) analyses of radiocarbon- dated sediment core samples from Sanjin, Asgat, Ganbold, and Mustei Nuur provide a nearly 11,000 year history of aquatic productivity changes within lakes of the Baroon Taiga Mountains, northern Mongolia. Productivity within these lakes is most sensitive to temperature fluctuations because the catchments are small, nutrient poor, and located at relatively high elevations (greater than 2200 m) with very low annual average temperatures. Within the Mustei Nuur basin, long-term decreases in reflectance and LOI-inferred algal productivity follow orbitally-forced reductions in northern hemisphere solar insolation (i.e., energy receipt) after 8000 years before present (B.P.). Prior to 8000 years ago, enhanced algal productivity within the lake likely reflects increasing northern hemisphere temperature trends following late glacial conditions. Higher frequency (decadal to centennial-scale) changes in biogenic silica, organic matter, and reflectance-inferred algal pigment concentrations within the late Holocene sediment sequences of Sanjin, Asgat, and Ganbold Nuur are interpreted as representing aquatic productivity variations influenced by the length of the ice-free growing season and, by further inference, local temperature variations. Reduced productivity and inferred lower temperatures are documented between 300 and 100 years B.P., roughly coincident with the Little Ice Age, whereas warmer conditions existed from 900-1100 years B.P., and between (roughly) 100 years B.P. and the present. Inferred warming over the last century parallels instrumental data trends, numerous high-latitude (arctic) paleoenvironmental records, and several other notable northern hemisphere temperature reconstructions. Correlations between late Holocene reflectance, biogenic silica, and LOI-inferred aquatic productivity records from the Baroon Taiga alpine lakes and nearby temperature

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

    USGS Publications Warehouse

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Goldsmith, Yonaton; Enzel, Yehouda; Stein, Mordechai

    2012-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    PubMed Central

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

    2010-01-01

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

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

    USGS Publications Warehouse

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

    2015-01-01

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

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

    PubMed Central

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

    2008-01-01

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

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

    SciTech Connect

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

    2008-05-20

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

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

    SciTech Connect

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

    1992-11-01

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

  10. DISTRIBUTION COEFFICIENTS FOR THE VOGTLE EARLY SITE PERMIT

    SciTech Connect

    Kaplan, D; Margaret Millings, M

    2006-07-18

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

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

    PubMed

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

    2016-07-01

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

  12. A Holocene Chronology of Alpine Glaciation for the Western United States

    NASA Astrophysics Data System (ADS)

    Marcott, S. A.; Clark, P. U.; Shakun, J. D.; Brook, E. J.

    2007-12-01

    Our research will develop a Holocene glacial chronology based on cosmogenic dating of boulders from moraine crests at several sites across the western United States. The chronology will address spatial and temporal glacier variability in response to postulated Holocene climate forcings. A number of studies have interpreted several Holocene glacial advances in the western U.S. (e.g., LIA, Neoglacial, Early-Holocene) (see, Burke and Birkeland, 1983; Davis, 1988 and Osborn and Bevis, 2001) but age control is based largely on relative dating techniques. Surface exposure dating using cosmogenic nuclides now provides a robust method to reevaluate and re-date several of these poorly defined glacial chronologies and develop a high-precision glacial record across the western U.S. for the Holocene epoch. Development of this chronology will provide new constrains on the extent of major Holocene climate forcings and their effects on the mass balance of western North America alpine glaciers as well as providing a better framework for understanding climate forcing during deglaciation. We will present initial data from three cirque moraines in the Medicine Bow Mountains, Wyoming as well as ongoing and future work in the western United States.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  19. Late Pleistocene--Early Holocene paleochannel systems and the episodic sea level framework on the continental shelf, south of Chesapeake Bay entrance, Virginia

    SciTech Connect

    Chen, Z.Q.; Hobbs, C.H. III ); Kimball, S.M. . Dept. of Environmental Science)

    1993-03-01

    More than 600 km of closely-spaced, high-resolution seismic lines on the continental shelf south of the Chesapeake Bay entrance enables recognition of three major paleochannel systems. Fourteen aminostratigraphic samples from paleochannel fill, an overlying barrier-spit complex, and basal strata in a suite of vibracores yield A/I values ranging from 0.01 to 0.55. Ages for the three paleochannel systems are thus assigned to oxygen isotope stages 2, 6, and 8 from top to bottom, corresponding to 30 [plus minus]10 ka, 150 [plus minus]20 ka, and 260 [plus minus] 20 ka BP respectively. These paleochannel systems are apparently compatible in age with the ancient valley systems identified recently beneath Chesapeake Bay. Based on the examination of lithology, sedimentary structure, sedimentologic character, and stratigraphic correlation among the vibracores, a preliminary reconstruction of depositional environments for the fill sequences is attempted. The spatial and temporal variation of the multilayered fill sequences is tested and further simplified using a Q-mode factor analysis. The analysis results a schematic picture of depositional environmental evolution of the fill sequences from fluvial-estuarine dominated environments, through a transitional stage, into shallow marine (beach-surf zone-shoreface-inner shelf) environments during the late Pleistocene to early Holocene time.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  1. Holocene Paleoenvironmental Change in the Kenyan Central Rift as Indicated by Micromammals from Enkapune Ya Muto Rockshelter

    NASA Astrophysics Data System (ADS)

    Marean, Curtis W.; Mudida, Nina; Reed, Kaye E.

    1994-05-01

    An assemblage of micromammals, recovered from the Holocene levels of a rockshelter at 2400 m in the montane forest of the Mau Escarpment, were examined with the goal of testing and contributing to prior reconstructions of paleoenvironments in the Central Rift Valley of Kenya. Species representation in the assemblage is consistent with a drying of the Rift Valley lakes in the middle Holocene and suggests a decrease in forest accompanied by expanding grasslands near the site. Changes in the abundance of grassland species suggests an increase in the frequency of fires, probably the result of pastoral burning. The body size of the root rat ( Tachyoryctes splendens) decreases from the early Holocene to the middle Holocene, and this may indicate increasing aridity or increasing temperature. We compare measures of species diversity (number of taxa, species richness, and the Shannon diversity index) for both micromammals and macromammals since species diversity may change with paleoenvironmental change. The macromammals show no changes in species diversity that are assignable to paleoenvironmental change, while the micromammals show a trend toward decreasing diversity from the early to middle Holocene, and then show an increase in diversity during the peak of the middle Holocene dry phase, though sample size effects may be confounding the patterning.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  3. 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

  4. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  8. 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.

  9. Midwestern holocene paleoenvironments revealed by floodplain deposits in northeastern iowa.

    PubMed

    Chumbley, C A; Baker, R G; Bettis, E A

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

    USGS Publications Warehouse

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

    2005-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Benson, Larry; Kashgarian, Michaele; Rye, Robert; Lund, Steve; Paillet, Fred; Smoot, Joseph; Kester, Cynthia; Mensing, Scott; Meko, Dave; Lindström, Susan

    2002-02-01

    Continuous, high-resolution δ18O 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 Malpais 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 δ18O value of CaCO 3 precipitated between 6500 and 3430 cal yr BP was 1.6‰ less than the mean value of CaCO 3 precipitated after 2740 cal yr BP. Numerical calculations indicate that the shift in the δ18O 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 δ18O records from Owens Lake indicate that the first interval in the early Holocene

  12. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    SciTech Connect

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

    1992-03-01

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

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

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

    SciTech Connect

    Huber, J.K. . Archaeometry Lab.)

    1993-03-01

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

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

    USGS Publications Warehouse

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  1. Tracing Late Holocene Warm Periods in the Galician Continental Margin (NW Spain): Detrital Control vs. Early Diagenetic Modulation.

    NASA Astrophysics Data System (ADS)

    Mohamed, K.; Rey, D.; Rubio, B.; Vilas, F.

    2007-12-01

    The sediments of the Galician continental margin (NW Spain) exhibit great but variable degrees of early diagenetic dissolution of magnetic minerals. This process completely erases any detrital magnetic signal at time-scales that range from about 1,000 years to less than 50 years in the highly productive estuarine-like environment of the Galician Rias Baixas. The more open marine conditions encountered in the adjoining continental shelf exhibit however a significantly different behavior. The singular balance between early diagenetic dissolution and lower sedimentation rates allows partial and variable preservation of the also variable detritally controlled magnetic inputs. In this context it is possible to reconstruct the recent environmental history of the area attending to the changes in the concentration of magnetically-interesting iron oxides. High-resolution magnetic and geochemical measurements carried out in 6 cores from the continental self evidenced the occurrence of correlatable peaks of magnetic mineral concentration that were interpreted as periods of enhanced detrital input. Magnetically depleted sediments were related to lower detrital input and/or to enhanced productivity that intensified the reductive conditions. The magnetic concentration peaks occurred within the Medieval (MWP) and Roman Warm Periods. Similar concentrations of hematite in the MWP and the RWP suggest that the lower concentration-dependent magnetic properties in the RWP are most likely caused by a greater degree of dissolution of magnetic detrital oxides due to a longer exposure to reducing conditions. These features could be traced over all the studied area, despite the great heterogeneity of the shelf sediments. This highlights the potential of magnetic properties as proxies of paleoenvironmental conditions in areas of similar complexity. This approach can be used as a rapid and cost-effective tool to screen large areas in the search for suitable settings for more precise, but time

  2. Earliest Holocene south Greenland ice sheet retreat within its late Holocene extent

    NASA Astrophysics Data System (ADS)

    Carlson, Anders E.; Winsor, Kelsey; Ullman, David J.; Brook, Edward J.; Rood, Dylan H.; Axford, Yarrow; LeGrande, Allegra N.; Anslow, Faron S.; Sinclair, Gaylen

    2014-08-01

    Early Holocene summer warmth drove dramatic Greenland ice sheet (GIS) retreat. Subsequent insolation-driven cooling caused GIS margin readvance to late Holocene maxima, from which ice margins are now retreating. We use 10Be surface exposure ages from four locations between 69.4°N and 61.2°N to date when in the early Holocene south to west GIS margins retreated to within these late Holocene maximum extents. We find that this occurred at 11.1 ± 0.2 ka to 10.6 ± 0.5 ka in south Greenland, significantly earlier than previous estimates, and 6.8 ± 0.1 ka to 7.9 ± 0.1 ka in southwest to west Greenland, consistent with existing 10Be ages. At least in south Greenland, these 10Be ages likely provide a minimum constraint for when on a multicentury timescale summer temperatures after the last deglaciation warmed above late Holocene temperatures in the early Holocene. Current south Greenland ice margin retreat suggests that south Greenland may have now warmed to or above earliest Holocene summer temperatures.

  3. Evidence for an early land use in the Rhône delta (Mediterranean France) as recorded by late Holocene fluvial paleoenvironments (1640-100 BC)

    NASA Astrophysics Data System (ADS)

    Arnaud-Fassetta, Gilles; De Beaulieu, Jacques-Louis; Suc, Jean-Pierre; Provansal, Mireille; Williamson, David; Leveau, Philippe; Aloïsi, Jean-Claude; Gadel, François; Giresse, Pierre; Oberlin, Christine; Duzer, Danièle

    The overall objective of this paper is to describe the late Holocene (1640-100 BC) sedimentary and biological evolution of the Rhône-delta-plain, to interpret the sedimentary facies and palynofacies as the result of the effects of fluvial dynamic fluctuations and relative sea level change and to evaluate the paleohydrological constraints in the development of the land use and settlements of the Camargue. Focus is made on the upper part of V III core drilled on NE of the Vaccarès lagoon. By combining sedimentology, palynology, magnetic susceptibility and archeological data, this study allowed to identify the superposition of three types of paleo-environments (marsh, fluvial floodplain, levee/crevasse splay). This sequence indicates a gradual extension of fluvial environments between the end of the second millennium BC and the 1st century BC. The variability of fluvial dynamic is evident during this period with important flood events which contrast with periods of low flow. Pollen record can be a good marker of the fluvial dynamic variability. The expression of the riparian tree pollen grains in the coarser floodplain deposits could correspond to increased fluvial influence and probably to erosion of riverbank during flood events. The local plants are associated to the low energy sedimentary environments. Focuses are made on the relations between the evolution of the environment and land use. The development of the cereal culture in the floodplain of the Rhône delta has been demonstrated between 1640-1410 and 100 BC. The last alluviation of the Rhône perturbs the research of the archaeological sites in the central part of the delta but the existence of the rural villages from the first part of the first millennium BC is highly possible.

  4. 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.

  5. Holocene vegetation and climate history of the northern Bighorn Basin, southern Montana

    USGS Publications Warehouse

    Lyford, M.E.; Betancourt, J.L.; Jackson, S.T.

    2002-01-01

    Records of Holocene vegetation and climate change at low elevations (<2000 m) are rare in the central Rocky Mountain region. We developed a record of Holocene vegetation and climate change from 55 14C-dated woodrat middens at two low-elevation sites (1275 to 1590 m, currently vegetated by Juniperus osteosperma woodlands, in the northern Bighorn Basin. Macrofossil and pollen analyses show that the early Holocene was cooler than today, with warming and drying in the middle Holocene. During the Holocene, boreal (Juniperus communis, J. horizontalis) and montane species (J. scopulorum) were replaced by a Great Basin species (J. osteosperma). J. osteosperma colonized the east side of the Pryor Mountains 4700 14C yr B.P. Downward movement of lower treeline indicates wetter conditions between 4400 and 2700 14C yr B.P. Increased aridity after 2700 14C yr B.P. initiated expansion of J. osteosperma from the east to west side of the Pryor Mountains. ?? 2002 University of Washington.

  6. 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.

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

    PubMed

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

    2015-03-24

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

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

    PubMed

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

    2015-03-24

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

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

    PubMed Central

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

    2015-01-01

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

  10. Holocene fire and vegetation dynamics in a montane forest, North Cascade Range, Washington, USA

    NASA Astrophysics Data System (ADS)

    Prichard, Susan J.; Gedalof, Ze'ev; Oswald, W. Wyatt; Peterson, David L.

    2009-07-01

    We reconstructed a 10,500-yr fire and vegetation history of a montane site in the North Cascade Range, Washington State based on lake sediment charcoal, macrofossil and pollen records. High-resolution sampling and abundant macrofossils made it possible to analyze relationships between fire and vegetation. During the early Holocene (> 10,500 to ca. 8000 cal yr BP) forests were subalpine woodlands dominated by Pinus contorta. Around 8000 cal yr BP, P. contorta sharply declined in the macrofossil record. Shade tolerant, mesic species first appeared ca. 4500 cal yr BP. Cupressus nootkatensis appeared most recently at 2000 cal yr BP. Fire frequency varies throughout the record, with significantly shorter mean fire return intervals in the early Holocene than the mid and late Holocene. Charcoal peaks are significantly correlated with an initial increase in macrofossil accumulation rates followed by a decrease, likely corresponding to tree mortality following fire. Climate appears to be a key driver in vegetation and fire regimes over millennial time scales. Fire and other disturbances altered forest vegetation at shorter time scales, and vegetation may have mediated local fire regimes. For example, dominance of P. contorta in the early Holocene forests may have been reinforced by its susceptibility to frequent, stand-replacing fire events.

  11. Holocene climate changes in eastern Beringia (NW North America) - A systematic review of multi-proxy evidence

    NASA Astrophysics Data System (ADS)

    Kaufman, Darrell S.; Axford, Yarrow L.; Henderson, Andrew C. G.; McKay, Nicholas P.; Oswald, W. Wyatt; Saenger, Casey; Anderson, R. Scott; Bailey, Hannah L.; Clegg, Benjamin; Gajewski, Konrad; Hu, Feng Sheng; Jones, Miriam C.; Massa, Charly; Routson, Cody C.; Werner, Al; Wooller, Matthew J.; Yu, Zicheng

    2016-09-01

    Reconstructing climates of the past relies on a variety of evidence from a large number of sites to capture the varied features of climate and the spatial heterogeneity of climate change. This review summarizes available information from diverse Holocene paleoenvironmental records across eastern Beringia (Alaska, westernmost Canada and adjacent seas), and it quantifies the primary trends of temperature- and moisture-sensitive records based in part on midges, pollen, and biogeochemical indicators (compiled in the recently published Arctic Holocene database, and updated here to v2.1). The composite time series from these proxy records 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 to clarify multi-centennial- to millennial-scale trends in Holocene climate change. To focus the synthesis, the paleo data are used to frame specific questions that can be addressed with simulations by Earth system models to investigate the causes and dynamics of past and future climate change. This systematic review shows that, during the early Holocene (11.7-8.2 ka; 1 ka = 1000 cal yr BP), rather than a prominent thermal maximum as suggested previously, temperatures were highly variable, at times both higher and lower than present (approximate mid-20th-century average), with no clear spatial pattern. Composited pollen, midge and other proxy records average out the variability and show the overall lowest summer and mean-annual temperatures across the study region during the earliest Holocene, followed by warming over the early Holocene. The sparse data available on early Holocene glaciation show that glaciers in southern Alaska were as extensive then as they were during the late Holocene. Early Holocene lake levels were low in interior Alaska, but moisture indicators show pronounced differences across the region. The highest

  12. Holocene vegetation changes through Lac Ledro sediments (Trentino, Italy).

    NASA Astrophysics Data System (ADS)

    Joannin, Sebastien; Vannière, Boris; Galop, Didier; Magny, Michel; Gilli, Adrian; Chapron, Emmanuel; Wirth, Stéfanie; Anselmetti, Flavio; Desmet, Marc

    2010-05-01

    Lake Ledro is part of the French program ANR LAMA (coordinators: M. Magny and N. Combourieu Nebout) which aims to link Holocene paleoenvironmental changes along a north-south transect in Italy. Lake Ledro (652 m a.s.l.; Trentino, north-eastern Italy) is the northward component of the transect. It is located on the southern slope of the Alps and its catchment area covers 131 km2 with mountains culminating at 1500-2000 m. A multi-proxy approach based on biotic and abiotic indicators (lake-level, palynology, geochemistry and geophysic) was developed from deep and littoral cores, including sediment sequences in Early and Middle Bronze Age lake-shore archaeological sites. We aim reconstructing paleoenvironmental changes resulting from both climate and anthropic influences trough the entire Holocene. A deep master core was built after extracting twin cores from a non disturbed sediment zone recognised by seismic-reflexion investigations. The age-depth model is based on 13 AMS 14C ages measured on terrestrial plant macrofossils and the mean temporal resolution for analyses is ca 60 years. Palynological study shows the usual vegetation succession for the southern slope of the Alps. During the first part of the Holocene, abrupt changes are observed in pollen assemblages in relation to changes in other proxies (XRF and Magnetic Susceptibility) and correlate with cold events associated to the deglaciation in the North-Atlantic area. Cool episodes corresponding to the PreBoreal Oscillation (ca 11.3 ka cal BP) and 8.2 ka event are respectively characterized by stopping afforestation and a strong development of Abies in the local ecosystem. During the second part of the Holocene, two declines of arboreal pollen abundance are observed in relation with occurrences in both cereal and anthropic pollen indicators. These two phases are confirmed by increase in soil erosion as indicated by abiotic proxies. They give evidence of two successive steps for human settlement (Early

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  14. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... proceeding: (i) The nuclear power reactor proposed to be built does not fit within one or more of the site... NUCLEAR POWER PLANTS Early Site Permits § 52.39 Finality of early site permit determinations. (a... approved an emergency plan (or major features thereof) that is in use by a licensee of a nuclear...

  15. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... proceeding: (i) The nuclear power reactor proposed to be built does not fit within one or more of the site... NUCLEAR POWER PLANTS Early Site Permits § 52.39 Finality of early site permit determinations. (a... approved an emergency plan (or major features thereof) that is in use by a licensee of a nuclear...

  16. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... proceeding: (i) The nuclear power reactor proposed to be built does not fit within one or more of the site... NUCLEAR POWER PLANTS Early Site Permits § 52.39 Finality of early site permit determinations. (a... approved an emergency plan (or major features thereof) that is in use by a licensee of a nuclear...

  17. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... proceeding: (i) The nuclear power reactor proposed to be built does not fit within one or more of the site... NUCLEAR POWER PLANTS Early Site Permits § 52.39 Finality of early site permit determinations. (a... approved an emergency plan (or major features thereof) that is in use by a licensee of a nuclear...

  18. 10 CFR 52.39 - Finality of early site permit determinations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... proceeding: (i) The nuclear power reactor proposed to be built does not fit within one or more of the site... NUCLEAR POWER PLANTS Early Site Permits § 52.39 Finality of early site permit determinations. (a... approved an emergency plan (or major features thereof) that is in use by a licensee of a nuclear...

  19. 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.

  20. Phosphorylation Site Dynamics of Early T-cell Receptor Signaling

    PubMed Central

    Rigbolt, Kristoffer T. G.; Hu, Bin; Hlavacek, William S.; Blagoev, Blagoy

    2014-01-01

    In adaptive immune responses, T-cell receptor (TCR) signaling impacts multiple cellular processes and results in T-cell differentiation, proliferation, and cytokine production. Although individual protein–protein interactions and phosphorylation events have been studied extensively, we lack a systems-level understanding of how these components cooperate to control signaling dynamics, especially during the crucial first seconds of stimulation. Here, we used quantitative proteomics to characterize reshaping of the T-cell phosphoproteome in response to TCR/CD28 co-stimulation, and found that diverse dynamic patterns emerge within seconds. We detected phosphorylation dynamics as early as 5 s and observed widespread regulation of key TCR signaling proteins by 30 s. Development of a computational model pointed to the presence of novel regulatory mechanisms controlling phosphorylation of sites with central roles in TCR signaling. The model was used to generate predictions suggesting unexpected roles for the phosphatase PTPN6 (SHP-1) and shortcut recruitment of the actin regulator WAS. Predictions were validated experimentally. This integration of proteomics and modeling illustrates a novel, generalizable framework for solidifying quantitative understanding of a signaling network and for elucidating missing links. PMID:25147952

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  4. Late Weichselian and Holocene paleoceanography of Storfjordrenna, southern Svalbard

    NASA Astrophysics Data System (ADS)

    Łącka, M.; Zajączkowski, M.; Forwick, M.; Szczuciński, W.

    2014-08-01

    Multiproxy analyses (incl. benthic and planktonic foraminifera, δ18O and δ13C records, grain-size distribution, ice-rafted debris, XRF geochemistry and magnetic susceptibility) were performed on a 14C dated marine sediment core from Storfjordrenna, off southern Svalbard. The sediments in the core cover the termination of Bølling-Allerød, the Younger Dryas and the Holocene, and they reflect general changes in the hydrology/climate of the European Arctic after the last glaciation. Grounded ice of the last Svalbard- Barents Sea Ice Sheet retreated from the coring site ca. 13 850 cal yr BP. During the transition from the sub-glacial to glacimarine setting, Arctic Waters dominated the hydrography in Storfjordrenna. However, the waters were not uniformly cold and experienced several warmer spells. A progressive warming and marked change in the nature of hydrology occurred during the early Holocene. Relatively warm and saline Atlantic Water started to dominate the hydrography from approx. 9500 cal yr BP. Even though the climate in eastern Svalbard was milder at that time than at present (smaller glaciers), there were two slight coolings observed in the periods of 9000-8000 cal yr BP and 6000-5500 cal yr BP. A change of the Storfjordrenna hydrology occurred at the beginning of late Holocene synchronously with glacier growth on land and enhanced bottom current velocities. Although cooling was observed in the surface water, Atlantic Water remained present in the deeper part of water column of Storfjordrenna.

  5. Holocene coastal glaciation of Alaska

    NASA Astrophysics Data System (ADS)

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  7. Holocene to contemporary source-to-sink fluxes in a valley-fjord system in western Norway: Erdalen and Bødalen site project (SedyMONT - IP Norway)

    NASA Astrophysics Data System (ADS)

    Beylich, A. A.; Laute, K.; Liermann, S.

    2012-04-01

    The focus of this Norwegian Research Council (NFR) funded Norwegian Individual Project (IP) (http://www.ngu.no/sedymont) within the European Science Foundation (ESF) SedyMONT (http://www.sedymont.eu) (EUROCORES TOPO-EUROPE) Programme (http://www.esf.org/topoeurope) is on Holocene, subrecent and contemporary sedimentary fluxes and budgets in the Erdalen and Bødalen valley systems in Nordfjord, western Norway. The innovative approach of this international research project is the integrated quantitative study of longer-term (Holocene), subrecent and contemporary source-to-sink fluxes and geomorphic process rates in selected representative valley-fjord systems using a novel combination of advanced methods and techniques. With respect to the main aims and objectives of ESF SedyMONT, the following main aims of the Erdalen and Bødalen site project can be stressed: - Analyse how the inheritance of the landscape due to the influence of the Last Glacial Maximum (LGM) has affected process rates over time (paraglacial system), - Document changes in process rates over different timescales by combining quantitative knowledge on Holocene process rates with newly generated data on subrecent and contemporary process rates. High-resolution monitoring of denudative surface processes in Erdalen and Bødalen, in combination with repeated analyses of surface water chemistry, atmospheric solute inputs and granulometric as well as shape analyses of suspended sediments provide high-resolution data to analyse and quantify present-day sedimentary and solute fluxes as well as sediment sources, denudation rates, and meteorological and topographical / landscape morphometric controls of denudative processes. In addition to standard methods for monitoring bedload transport, innovative techniques like horizontally installed impact sensors and biofilm analysis are applied in combination with advanced flume experiments (for calibration of field data) to analyse channel stability / mobility and to

  8. 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

  9. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Liu, Tanzhuo; Broecker, Wallace S.

    2007-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  13. Missing-Presumed Eroded: Holocene Sedimentation Patterns in Seneca Lake, NY

    NASA Astrophysics Data System (ADS)

    Loddengaard, K.; Curtin, T. M.

    2006-12-01

    The Finger Lakes of New York underwent a significant change in climate during the transition from the Hypsithermal to the Neoglacial at ~5 ka. To determine the effects of changes in climate on sedimentation patterns in the northern region of Seneca Lake, NY, we analyzed three cores that were collected along a shallow to deep water transect. Analyses of magnetic susceptibility, organic matter and carbonate content, fossil content, and grain size at a 1-cm interval were used to correlate cores, identify periods of erosion or non- deposition and assess the relative truncation of the Holocene sediment record. The stratigraphy and sedimentology of the cores indicate the lake contains a spatially and temporally discontinuous sediment record. Preliminary results indicate that the early to mid-Holocene sediment record was preferentially eroded in the deepwater cores, between 20 and 50 m water depth. At the deepwater sites, there is a gap in the sediment record that spans between ~12 and ~5 ka. Conversely, the late Holocene record is more complete in the deepwater cores than in the shallow water cores (12-20 m water depth). This data suggests a significant change on the controls and location of erosion and deposition in the lake during the Holocene. We hypothesize that the early to mid-Holocene sediment may have been eroded by strong internal seiches during stormy conditions that were initiated by cooler temperatures and a change in the position of the jet stream during the Hypsithermal-Neoglacial transition. Erosion occurred primarily in shallow water sites (<~30 m) during the Neoglacial, perhaps as a result of a change in the number and frequency of storms or strength of the internal seiche.

  14. Sensitivity of northern peatland carbon dynamics to Holocene climate change

    NASA Astrophysics Data System (ADS)

    Yu, Zicheng; Beilman, David W.; Jones, Miriam C.

    In this paper, we evaluate the long-term climate sensitivity and global carbon (C) cycle implications of northern peatland C dynamics by synthesizing available data and providing a conceptual framework for understanding the dominant controls, processes, and interactions of peatland initiation and C accumulation. Northern peatlands are distributed throughout the climate domain of the boreal forest/taiga biome, but important differences between peatland regions are evident in annual temperature vs. precipitation (T-P) space, suggesting complex hydroclimatic controls through various seasonal thermal-moisture associations. Of 2380 available basal peat dates from northern peatlands, nearly half show initiation before 8000 calendar years (cal years) B.P. Peat-core data from sites spanning peatland T-P space show large variations in apparent C accumulation rates during the Holocene, ranging from 8.4 in the Arctic to 38.0 g C m-2 a-1 in west Siberia, with an overall time-weighted average rate of 18.6 g C m-2 a-1. Sites with multiple age determinations show millennial-scale variations, with the highest C accumulation generally at 11,000-8000 cal years B.P. The early Holocene was likely a period of rapid peatland expansion and C accumulation. For example, maximum peat expansion and accumulation in Alaska occurred at this time when climate was warmest and possibly driest, suggesting the dominant role of productivity over decomposition processes or a difference in precipitation seasonality. Northern peatland C dynamics contributed to the peak in atmospheric CH4 and the decrease in CO2 concentrations in the early Holocene. This synthesis of data, processes, and ideas provides baselines for understanding the sensitivity of these C-rich ecosystems in a changing climate.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  16. 10 CFR 52.27 - Limited work authorization after issuance of early site permit.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 2 2011-01-01 2011-01-01 false Limited work authorization after issuance of early site permit. 52.27 Section 52.27 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS Early Site Permits § 52.27 Limited work authorization...

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  18. 10 CFR 52.27 - Limited work authorization after issuance of early site permit.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 2 2012-01-01 2012-01-01 false Limited work authorization after issuance of early site permit. 52.27 Section 52.27 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS Early Site Permits § 52.27 Limited work authorization...

  19. 10 CFR 52.27 - Limited work authorization after issuance of early site permit.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 2 2014-01-01 2014-01-01 false Limited work authorization after issuance of early site permit. 52.27 Section 52.27 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS Early Site Permits § 52.27 Limited work authorization...

  20. Holocene subsurface transport between subpolar and subtropical gyre in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Repschläger, J.; Garbe-Schoenberg, C. D.; Weinelt, M.; Schneider, R. R.

    2014-12-01

    The transport of warm waters from the subtropics into the subpolar North Atlantic (NA) strongly affects the climate variability of Europe and governs the strength of NA deepwater convection and the resulting AMOC strength. Modern oceanographic studies and climate models propose that this transport is mainly driven by the interaction between the subtropical (STG) and the subpolar (STG) gyre via subsurface pathways. Paleoceanographic studies postulate that subsurface transport of warm saline water from the STG may counterbalance freshening of the SPG and stabilize the Holocene AMOC mode. We tested this hypothesis, with new stable isotope and Mg/Ca analyses from surface and subsurface dwelling foraminifera obtained from a core site situated at the northern boundary of the STG. Our new dataset indicates stable sea surface conditions and stronger variability in the subsurface temperature and salinities. During early Holocene similar subsurface temperatures and salinities in STG and SPG indicate that both regions were directly influenced by the same water mass that probably originated from NH meltwater discharges (e.g. Thornalley et al., 2009). This period is followed by a strong Mid-Holocene divergence between subpolar and STG salinity and temperature records, while the latter two properties in the STG converge towards the records from the subtropical source region (Bahr et al., 2013). We infer that this convergence was driven by a change in the source of subsurface waters due to the expansion of subtropical water masses in the Mid-Holocene. The Mid- to late Holocene (after 6 ka BP) is characterized again by in phase variations of subsurface subpolar and STG records although both temperatures and salinities differ in absolute values. This resemblance indicates a strong connection via subsurface transport between the STG and the subpolar region that probably stabilized the late Holocene NA gyre circulation.

  1. Holocene Lake Records on Kamchatka

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  2. Holocene changes in vegetation composition in northern Europe: why quantitative pollen-based vegetation reconstructions matter

    NASA Astrophysics Data System (ADS)

    Marquer, Laurent; Gaillard, Marie-José; Sugita, Shinya; Trondman, Anna-Kari; Mazier, Florence; Nielsen, Anne Birgitte; Fyfe, Ralph M.; Odgaard, Bent Vad; Alenius, Teija; Birks, H. John B.; Bjune, Anne E.; Christiansen, Jörg; Dodson, John; Edwards, Kevin J.; Giesecke, Thomas; Herzschuh, Ulrike; Kangur, Mihkel; Lorenz, Sebastian; Poska, Anneli; Schult, Manuela; Seppä, Heikki

    2014-04-01

    We present pollen-based reconstructions of the spatio-temporal dynamics of northern European regional vegetation abundance through the Holocene. We apply the Regional Estimates of VEgetation Abundance from Large Sites (REVEALS) model using fossil pollen records from eighteen sites within five modern biomes in the region. The eighteen sites are classified into four time-trajectory types on the basis of principal components analysis of both the REVEALS-based vegetation estimates (RVs) and the pollen percentage (PPs). The four trajectory types are more clearly separated for RVs than PPs. Further, the timing of major Holocene shifts, rates of compositional change, and diversity indices (turnover and evenness) differ between RVs and PPs. The differences are due to the reduction by REVEALS of biases in fossil pollen assemblages caused by different basin size, and inter-taxonomic differences in pollen productivity and dispersal properties. For example, in comparison to the PPs, the RVs show an earlier increase in Corylus and Ulmus in the early-Holocene and a more pronounced increase in grassland and deforested areas since the mid-Holocene. The results suggest that the influence of deforestation and agricultural activities on plant composition and abundance from Neolithic times was stronger than previously inferred from PPs. Relative to PPs, RVs show a more rapid compositional change, a largest decrease in turnover, and less variable evenness in most of northern Europe since 5200 cal yr BP. All these changes are primarily related to the strong impact of human activities on the vegetation. This study demonstrates that RV-based estimates of diversity indices, timing of shifts, and rates of change in reconstructed vegetation provide new insights into the timing and magnitude of major human disturbance on Holocene regional vegetation, features that are critical in the assessment of human impact on vegetation, land-cover, biodiversity, and climate in the past.

  3. Late Glacial, Early Holocene and Late Holocene life at the interface of a distinct landscape — relationship of humans and environments in the Sub-Carpathian region (N Hungary)

    NASA Astrophysics Data System (ADS)

    Bácsmegi, Gábor; Sümegi, Pál; Törőcsik, Tünde

    2012-12-01

    Relationships between the communities and environment surrounding these communities can be disclosed by the application of different archeological, geological and environmental historical methods. This includes the deployment of numerous tools in scientific investigation including the application of chronological, sedimentological, geochemical and paleoecological analytical methods on sequences accumulated in historical catchment basins of peat-bog. The Nádas-tó at Nagybárkány is a small peatbog in the northern part of Hungary, on the Sub-Carpathian region. The formation of the lake can be traced back to the Late Glacial period. The sediments deposited in the lakebed provide a record of climatic and hydrologic changes. A higher water level could be demonstrated from the Late Glacial to the Mid-Holocene, when the reed-beds covered a small area only. This was followed by a hiatus spanning ca. 4400 years, caused by the deepening and cleaning of the lakebed during the Late Iron / Imperial Age, between 2100 - 1900 cal BP years. After this change the water level decreased and the water quality was more eutrophic. A reed-bed evolved around the lake. Paludification started with a bulrush floating mat phase at the close of the Middle Age, ca. 1500 cal AD years. The endowments and settlement pattern persisted from the Neolithic onwards until the terminal Modern Age, when measures aimed to ordain the area substantially altered the natural landscape. Although some anthropogenic disturbances can be reconstructed in the development of the peatland, some climatic effects and authogenic processes might be separated by paleoecological analyses.

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

    USGS Publications Warehouse

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

    2004-01-01

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

  5. Holocene dynamics of North Atlantic Deep Water Masses

    NASA Astrophysics Data System (ADS)

    Hoogakker, B.; Chapman, M.; McCave, I. N.; Hillaire-Marcel, C.

    2012-12-01

    The Atlantic Meridional Overturning Circulation (AMOC) is a key component in latitudinal heat and salt transport, comprising northward flow of salty warm near-surface waters in the North Atlantic Current, and its compensating cool return flow at depth. During the early Holocene high summer insolation and strong inflow of North Atlantic surface waters into the Nordic Seas and the Arctic Ocean may have contributed to increased deep-water formation. To assess the effect of increased deep-water formation in the Nordic Seas and the Arctic Ocean on AMOC we reconstructed and assessed bottom flow vigour (using the mean grain size of the sortable silt) and hydrographic properties (using benthic foraminiferal isotopes) at key locations in the deep North Atlantic. The core sites of MD99-2251 and ODP 980 are currently influenced by North East Atlantic Deep Water (NEADW-origin Iceland Scotland Overflow Water), whilst that of MD95-2024 is under the influence of North West Atlantic Bottom Water (NWABW-currently densest North Atlantic Deep Water mass, origin Denmark Strait Overflow). When exiting the Labrador Sea, NEADW and NWABW mix to make up Lower North Atlantic Deep Water. Our results show that NEADW at Gardar Drift in the northeast Atlantic was considerably enhanced and denser (comparable to NWABW) during the early Holocene, until ~6.5 ka. The density increase is attributed to NEADW mainly consisting of Iceland Scotland Overflow Water, lacking significant contributions of Labrador Sea Water or Lower Deep Water (LDW-origin Antarctic Bottom Water) that it contains at present. This implies there was no density gradient between these two deep-water masses during the early Holocene, contrary to today. A subsequent weakening of NEADW accompanied with a reduction in its density after 6.5 ka allowed a shoaling of LDW and deeper eastward advection of Labrador Sea Water into the northeast Atlantic basin. The density gradient observed between current NEADW and NWABW might have been

  6. The Construction Site Project: Transforming Early Childhood Teacher Practice

    ERIC Educational Resources Information Center

    McNaughton, Kathryn; Krentz, Caroline

    2007-01-01

    The work of Malaguzzi (in Edwards, Gandini, & Forman, 1998; Fraser, 2006) has made the fundamentals of the preschools of Reggio Emilia familiar to many early childhood educators. The article describes an authentic project that enhanced undergraduate and postgraduate participants' understanding of the impact of collaboration, conversation, and…

  7. 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

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

    SciTech Connect

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

    2011-03-07

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

  9. 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.

  10. 7300 years of vegetation history and climate for NW Malta: a Holocene perspective

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  11. 7300 years of vegetation history and climate for NW Malta: a Holocene perspective

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  12. Charcoal analysis and Holocene vegetation history in southern Syria

    NASA Astrophysics Data System (ADS)

    Willcox, George

    1999-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Mood, Bryan J.; Smith, Dan J.

    2015-11-01

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

  14. Early Site Permit Demonstration Program: Regulatory criteria evaluation report

    SciTech Connect

    Not Available

    1993-03-01

    The primary objective of the ESPDP is to demonstrate successfully the use of 10CFR52 to obtain ESPs for one or more US sites for one (or more) ALWR nuclear power plants. It is anticipated that preparation of the ESP application and interaction with NRC during the application review process will result not only in an ESP for the applicant(s) but also in the development of criteria and definition of processes, setting the precedent that facilitates ESPs for subsequent ESP applications. Because siting regulatory processes and acceptance criteria are contained in over 100 separate documents, comprehensive licensing and technical reviews were performed to establish whether the requirements and documentation are self-consistent, whether the acceptance criteria are sufficiently well-defined and clear, and whether the licensing process leading to the issuance of an ESP is unambiguously specified. The results of the technical and licensing evaluations are presented in this report. The purpose, background, and organization of the ESPDP is delineated in Section 1. Section 11 contains flowcharts defining siting application requirements, environmental report requirements, and emergency planning/preparedness requirements for ALWRS. The licensing and technical review results are presented in Section III.

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

    ERIC Educational Resources Information Center

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

    2016-01-01

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

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

    USGS Publications Warehouse

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

    2012-01-01

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

  17. Origin and dynamics of the northern South American coastal savanna belt during the Holocene - the role of climate, sea-level, fire and humans

    NASA Astrophysics Data System (ADS)

    Alizadeh, Kamaleddin; Cohen, Marcelo; Behling, Hermann

    2015-08-01

    Presence of a coastal savanna belt expanding from British Guiana to northeastern Brazil cannot be explained by present-day climate. Using pollen and charcoal analyses on an 11.6 k old sediment core from a coastal depression in the savanna belt near the mouth of the Amazon River we investigated the paleoenvironmental history to shed light on this question. Results indicate that small areas of savanna accompanied by a forest type composed primarily by the genus Micropholis (Sapotaceae) that has no modern analog existed at the beginning of the Holocene. After 11,200 cal yr BP, savanna accompanied by few trees replaced the forest. In depressions swamp forest developed and by ca 10,000 cal yr BP replaced by Mauritia swamps. Between 8500 and 5600 cal yr BP gallery forest (composed mainly of Euphorbiaceae) and swamp forest succeeded the treeless savanna. The modern vegetation with alternating gallery forest and savanna developed after 5600 cal yr BP. We suggest that the early Holocene no-analog forest is a relict of previously more extensive forest under cooler and moister Lateglacial conditions. The early Holocene savanna expansion indicates a drier phase probably related to the shift of the Intertropical Convergence Zone (ITCZ) towards its northernmost position. The mid-Holocene forest expansion is probably a result of the combined influence of equatorwards shift of ITCZ joining the South Atlantic Convergence Zone (SACZ). The ecosystem variability during the last 5600 cal yr BP, formed perhaps under influence of intensified ENSO condition. High charcoal concentrations, especially during the early Holocene, indicate that natural and/or anthropogenic fires may have maintained the savanna. However, our results propose that climate change is the main driving factor for the formation of the coastal savanna in this region. Our results also show that the early Holocene sea level rise established mangroves near the study site until 7500 cal yr BP and promoted swamp formation in

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

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

    PubMed

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

    2015-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Dyke, Arthur S.; Savelle, James M.

    2001-05-01

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

  2. Late Weichselian and Holocene palaeoceanography of Storfjordrenna, southern Svalbard

    NASA Astrophysics Data System (ADS)

    Łącka, M.; Zajączkowski, M.; Forwick, M.; Szczuciński, W.

    2015-03-01

    Multiproxy analyses (including benthic and planktonic foraminifera, δ18O and δ13C records, grain-size distribution, ice-rafted debris, XRF geochemistry and magnetic susceptibility) were performed on a 14C-dated marine sediment core from Storfjordrenna, located off of southern Svalbard. The sediments in the core cover the termination of Bølling-Allerød, the Younger Dryas and the Holocene and reflect general changes in the oceanography/climate of the European Arctic after the last glaciation. Grounded ice of the last Svalbard-Barents Sea Ice Sheet retreated from the coring site ca. 13 950 cal yr BP. During the transition from the subglacial to glaciomarine setting, Arctic Waters dominated the hydrography in Storfjordrenna. However, the waters were not uniformly cold and experienced several warmer spells. A progressive warming and marked change in the nature of the hydrology occurred during the early Holocene. Relatively warm and saline Atlantic Water began to dominate the hydrography starting from approximately 9600 cal yr BP. Although the climate in eastern Svalbard was milder at that time than at present (smaller glaciers), two periods of slight cooling were observed in 9000-8000 and 6000-5500 cal yr BP. A change in the Storfjordrenna oceanography occurred at the beginning of the late Holocene (i.e. 3600 cal yr BP) synchronously with glacier growth on land and enhanced bottom current velocities. Although cooling was observed in the Surface Water, Atlantic Water remained present in the deeper portion of the water column of Storfjordrenna.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  4. Early Site Permit Demonstration Program: Plant parameters envelope report. Volume 1

    SciTech Connect

    Not Available

    1993-03-01

    The Early Site Permit (ESP) Demonstration Program is the nuclear industry`s initiative for piloting the early resolution of siting-related issues before the detailed design proceedings of the combined operating license review. The ESP Demonstration Program consists of three phases. The plant parameters envelopes task is part of Phase 1, which addresses the generic review of applicable federal regulations and develops criteria for safety and environmental assessment of potential sites. The plant parameters envelopes identify parameters that characterize the interface between an ALWR design and a potential site, and quantify the interface through values selected from the Utility Requirements Documents, vendor design information, or engineering assessments. When augmented with site-specific information, the plant parameters envelopes provide sufficient information to allow ESPs to be granted based on individual ALWR design information or enveloping design information for the evolutionary, passive, or generic ALWR plants. This document is expected to become a living document when used by future applicants.

  5. Sediment trace metals as a recorder of bottom water redox conditions in the Baltic Sea over the Holocene

    NASA Astrophysics Data System (ADS)

    Slomp, C. P.; Jilbert, T.; van Riel, K. P. G. L.; Mort, H. P.; Conley, D. J.; Gustafsson, B. G.

    2012-04-01

    Increased inputs of nutrients from waste water and fertilizer have driven enhanced algal growth in the surface waters of the Baltic Sea over the past century. The sinking of this organic matter to the seafloor and subsequent decay has led to an oxygen demand in the bottom water that outpaces oxygen supply. Water column records indicate that this has resulted in a major redox shift in bottom water conditions from oxic to sulfidic (euxinic) in the late 1970's and early 1980's. Here, we show that this redox shift is recorded in sediment trace metal records throughout the Baltic Proper. We demonstrate that while rhenium (Re) tracks suboxia, molybdenum (Mo) is an accurate indicator of euxinia in the Baltic Sea. We subsequently use sediment Mo data for two long cores to assess changes in redox conditions over the Holocene. At one site, our results confirm earlier work showing three distinct periods of bottom water euxinia, namely during modern and medieval times and the early Holocene. The second site, in contrast, was euxinic throughout most of the Holocene. We suggest that the variable trends in redox observed at the first site are representative for most of the Baltic Proper and long-term bottom water euxinia in the Baltic Sea is limited to several small restricted basins.

  6. Late Devensian and Holocene relative sea-level changes on the Isle of Skye, Scotland, UK

    NASA Astrophysics Data System (ADS)

    Selby, Katherine A.; Smith, David E.

    2007-02-01

    Detailed litho- and biostratigraphical analyses from three coastal sites in contrasting coastal settings on the Isle of Skye, Scotland, UK, reveal evidence for several changes in relative sea level during the Late Devensian and Holocene. At the start of the record, relative sea level in the area was high at ca. 12 500 14C (ca. 14 800 cal.) yr BP but then fell, reaching a low point during the Younger Dryas, at ca. 11 000-10 000 14C (ca. 13 000-11 600 cal.) yr BP, when a rock platform, correlated with the Main Rock Platform, was formed. In the early-middle Holocene, relative sea level was rising by ca. 8000 14C (ca. 8800 cal.) yr BP and in northeast Skye a lagoonal surface, correlated with the Main Postglacial Shoreline, was formed at ca. 6600 14C (ca. 7500 cal.) yr BP. By the late Holocene, relative sea level was again falling, but a rise, registered at at least two sites, began probably before ca. 4000 14C (ca. 4500 cal.) yr BP, and a second lagoonal surface in northeast Skye, correlated with the Blairdrummond Shoreline, was formed, although by ca. 3000 14C (ca. 3200 cal.) yr BP relative sea level in the area had resumed its downward trend. The pattern of relative sea-level changes disclosed is compared with evidence elsewhere in Scotland. Copyright

  7. Holocene sea-level change and the emergence of Neolithic seafaring in the Fuzhou Basin (Fujian, China)

    NASA Astrophysics Data System (ADS)

    Rolett, Barry V.; Zheng, Zhuo; Yue, Yuanfu

    2011-04-01

    Neolithic seafaring across the Taiwan Strait began approximately 5000 years ago and involved open-sea voyages over distances of at least 130 km. Rapid sea-level rise preceded the emergence of open-sea voyaging, but the possible role of environmental change as a stimulus for the development of seafaring is poorly understood. We investigate this problem by presenting a record of Holocene sea-level change and coastal transformation based on sediment cores obtained from the Fuzhou Basin on the coast of Fujian, China. The cores are located in direct proximity to archaeological sites of the Tanshishan Neolithic culture (5000-4300 cal BP), which is significant for its similarity to the earliest Neolithic cultures of Taiwan. Multiple lines of evidence record the early Holocene inundation of the Fuzhou Basin around 9000 cal BP, the mid-Holocene sea-level highstand, and the final Holocene marine transgression. This final transition is precisely documented, with AMS dates showing the change occurred close to 1900 cal BP. Our paleogeographic reconstruction shows that a large estuary filled the Fuzhou Basin during the mid-Holocene. Tanshishan and Zhuangbianshan, two of the major Fuzhou Basin Neolithic sites, are located today on hills nearly 80 km from the modern coastline. However, when the sites were settled around 5500-5000 cal BP, the marine transgression had transformed these hills into islands in the upper estuary. We suggest that the Neolithic era estuary setting, together with the lack of land suitable for rice paddy agriculture, inhibited intensive food production but favored a maritime orientation and the development of seafaring.

  8. Latest Pleistocene and Holocene glacier fluctuations in southernmost Tierra del Fuego, Argentina

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Clague, John J.; Osborn, Gerald; Davis, P. Thompson; Ponce, Federico; Goehring, Brent; Maurer, Malyssa; Rabassa, Jorge; Coronato, Andrea; Marr, Rob

    2013-10-01

    Some researchers propose that summer insolation controls long-term changes in glacier extent during the Holocene. If this hypothesis is correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Although the chronology of Holocene glacier fluctuations in the Northern Hemisphere is well established, much uncertainty remains in the ages of Holocene glacier fluctuations in the Southern Hemisphere, especially South America. Here we report on latest Pleistocene and Holocene glacier fluctuations at the southern end of the Andes north and west of Ushuaia, Argentina. Surface exposure ages (10Be) from glaciated bedrock beyond cirque moraines indicate that alpine areas were free of ice by ca 16.9 ka. One, and in some cases two, closely spaced moraines extend up to 2 km beyond Little Ice Age moraines within many of the cirques in the region. The mean age of five 10Be ages from two pre-Little Ice Age moraines is 14.27-12.67 ka, whereas a minimum limiting radiocarbon age for a smaller, recessional moraine in one cirque is 12.38-12.01 ka. Our ages imply that, following glacier retreat beginning about 18.52-17.17 ka, cirque glaciers first advanced during the Antarctic Cold Reversal (14.5-12.9 ka) and may have later advanced or stabilized in the Younger Dryas Chronozone (12.9-11.7 ka). Based on the distribution of thick, geochemically distinct, and well-dated Hudson tephra, no Holocene moraines appear to be older than 7.96-7.34 ka. At some sites, there is evidence for one or more advances of glaciers sometime between 7.96-7.34 ka and 5.29-5.05 ka to limits only tens of meters beyond Little Ice Age maximum positions. Taken together, the data: 1) do not support the summer insolation hypothesis to explain Holocene glacier fluctuations in southernmost Patagonia; 2) confirm paleobotanical evidence for a warm, dry early Holocene; and 3) suggest that some glaciers in the region reached extents comparable to

  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. The conservation of Holocene sediment archives in the Mediterranean and its relevance for geo-archaeology.

    NASA Astrophysics Data System (ADS)

    Sevink, J.; van Leusen, M.

    2012-04-01

    Mediterranean countries have laws and regulations that ensure the protection of their heritage, which often includes their 'geological heritage', such as in Italy where this geology is protected to an extent that is unknown to most Central and Northern European countries. This protection or geo-conservation, however, pertains largely to mineral and fossil bearing areas and sites, and rarely to relatively recent (Holocene to Late Quaternary) sediment archives. Such sediment archives play an increasingly important role in geo-archeology, allowing for precise dating and description of early cultures and their environment, as well as of the impact of man on his environment in connection with early land use and past climate changes. Holocene paleoecological archives are relatively scarce in the mediterranean, because of the climatic conditions which promote rapid and strong decomposition of organic remains. Current high quality archives pertain largely to crater lake and deep sea cores, which are hardly relevant for geo-archeology. Excellent archives may be available in coastal plains as was recently demonstrated for the Agro Pontino, allowing for detailed paleoecological studies as well as tephrochronological dating. Such archives are crucial for modern integrated geo-archeological studies and merit to be protected against degradation brought about by the often intensive agriculture in these plains that is marked by deep drainage and ploughing. In the Agro Pontino, such agriculture has already led to a virtually complete destruction of the Late Holocene (Roman and later) record in its former marshes. Based on this experience, authorities are strongly advised to include areas with important Holocene geo-archives in the geo-heritage to be conserved.

  11. Patterns and drivers of Holocene vegetational change near the prairie-forest ecotone in Minnesota: revisiting McAndrews' transect.

    PubMed

    Nelson, David M; Hu, Feng Sheng

    2008-07-01

    Holocene vegetational dynamics along the prairie-forest border of Minnesota were first documented in McAndrews' classic work. Despite numerous subsequent paleo-studies, a number of questions remain unanswered about the vegetation history of the region. Here, pollen, stable-isotope, mineral, and charcoal data are described from three lakes near McAndrews' sites. These data were compared with other paleoenvironmental records to reconstruct vegetation, aridity, and fire. The climate was relatively wet with increasing summer temperatures before approximately 8000 yr before present (BP). The rates of changes were asymmetric for the onset and termination of middle-Holocene aridity, with an abrupt increase at approximately 8000 yr BP and a gradual, but variable, decline from approximately 7800 to 4000 yr BP. Early-Holocene coniferous forests changed to mixed-grass prairie without an intervening period of tallgrass prairie or deciduous forest, whereas the retreat of prairie was characterized by transitions from mixed-grass to tallgrass prairie to deciduous forest and finally to coniferous forest. Within the middle Holocene, the composition and structures of grass-dominated vegetation varied both temporally and spatially. Fire primarily responded to changes in climate and fuel loads. Vegetation was more strongly influenced by climatic changes than by fire-regime shifts.

  12. Holocene aeolian sediments on the NE Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Stauch, G.; Lehmkuhl, F.; Hilgers, A.; Zhao, H.

    2012-04-01

    The semiarid climate of the northeastern Tibetan Plateau supports the formation of different types of aeolian sediments and landforms during the Holocene. Aeolians silts and sands in the catchment of the Donggi Cona in an elevation above 4000m to 4800 m asl reflect variable climate conditions during that time as well as different sediment sources. Based on 51 OSL datings and catchment wide geomorphological mapping a complex pattern of long and short distance sediment transport has been reconstructed. Only few aeolian archives are preserved from the late Pleistocene in this mountain environment indicating cold and dry climate conditions which prevented a continuous accumulation. During the early Holocene a phase of increased aeolian sedimentation of sand at the slopes of the mountains has been reconstructed. The sand originated from a large alluvial fan which was highly active during the Pleistocene. In addition, a thin loess cover is preserved at a few sites in the neighboring mountains ranges. The sedimentation of the loess started around 2000 years later than the sedimentation of the sand at the foot slope. Both archives are related to an increase in precipitation at the northern margin of the Tibetan Plateau which was related to a strengthening of the Asian Monsoon during that time. The wetter climate conditions favored the development of a vegetation cover which leads to the trapping and fixation of the aeolian sediments. However, with a further strengthening of the Monsoon systems these archives subsequently eroded due to higher run off and accumulated as colluvial and fluvial deposits in the basins. These phase lasted until 6 ka. A second aeolian period started at around 3 ka with the formation new dunes in the basins. This period can be associated with dry and cold climate of the late Holocene supporting the reactivation of the sand in the area. This might be further enhanced by an increased human impact by grazing during the late Holocene and resulting

  13. The late devensian and holocene evolution of Barmouth Bay, Wales

    NASA Astrophysics Data System (ADS)

    Larcombe, Piers; Jago, Colin F.

    1994-03-01

    A marine seismic and sedimentological investigation of the Late-Devensian and Holocene sediments of Barmouth Bay, North Wales, was undertaken to reconstruct late-glacial and Holocene sedimentary environments, and to evaluate post-glacial sedimentation rates. In the last glacial, the Devensian, many Welsh estuaries were the sites of valley glaciers flowing from the Welsh Ice cap onto the modern inner-shelf. At Barmouth, the Mawddach valley glacier flowed into the present inner-shelf of Cardigan Bay. The modern courses of the Mawddach Estuary and the river Gwril were overdeepened by erosive sub-glacial flows, and are later infilled by a coarse-grained sub-glacial and pro-glacial infill sequence. With late-glacial relative sea-level rise and retreat of the Welsh Ice, the Mawddach valley tidewater glacier became grounded and confined to the valley. Re-equilibration of the ice profile occurred, and a morainal complex was formed at its toe. In the early Holocene, the morainal complex formed the seaward boundary of a sheltered nearshore basin where fine-grained, partly organic, sediments were deposited in a lagoonal or estuarine environment. Holocene reworking of the sediments by shallow-marine processes has formed a lag surface to the morainal complex, and has introduced gravel of Irish Sea Ice character from offshore. Wave action has formed a shingle coastal barrier, narrowing the mouth of the modern estuary. A shoreface-attached sand wedge, which attains a maximum thickness of 4 m beneath the modern ebb-tidal delta, overlies the lag surface and onlaps the coastal barrier. Since 8-9 ky BP, the mean sediment accumulation rate of estuarine and shallow-marine sediments has been 2.3-3.1 mm/yr, roughly equivalent to the long-term mean rate of sea-level rise for Cardigan Bay. This mean rate masks rapidly increasing accumulation rates in the Mawddach Estuary in the last 5-6 ky, which now may be 82 mm/yr, and which are due to reworking of shoreface and barrier sands into the

  14. 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

  15. Late Holocene and recent rainforest cultural landscapes of North Queensland, Australia

    NASA Astrophysics Data System (ADS)

    Steinberger, L. M.; Moss, P. T.; Haberle, S.; Cosgrove, R.; Ferrier

    2011-12-01

    The tropical rainforests of North Queensland, Australia, have been environments of significant human activity for several thousand years. Palaeoecological research has highlighted the long-term effects of Quaternary climate change on these environments at a broad spatial scale, including the expansion of tropical rainforest across the region following the termination of the Last Glacial Maximum. However, identifying the effects of a hunter-gatherer Aboriginal population has been more difficult. Palaeoecological suggestions of Pleistocene Aboriginal burning, based on pollen and charcoal records, have relied on coincident timing with a general narrative of colonisation rather than direct links with archaeological evidence. Current research is explicitly examining the environmental consequences of human activity in North Queensland rainforests by producing local palaeoecological data directly linked to sites and periods of human occupation. Pollen, macrocharcoal and phytolith records have been produced from sites of human activity within the rainforest. Late Holocene Aboriginal occupation of the rainforest is demonstrated to have had significant cultural links to patches of open vegetation that existed within the rainforest. While these patches are likely to have originated as edaphically controlled remnants of Pleistocene vegetation, their expansion and maintenance in the late Holocene is associated with increasing intensity of Aboriginal occupation of the rainforest. Late Holocene Aboriginal rainforest occupation is also contrasted with the historical European colonisation of the rainforest in the late 19th century, which resulted in the most significant environmental changes in the region since the early Holocene. Historical and ethnographic records provide important cultural context for understanding the transition between Aboriginal and European cultural landscapes of the rainforest.

  16. Holocene growth of a mid-Pacific atoll: Tarawa, Kiribati

    NASA Astrophysics Data System (ADS)

    Marshall, J. F.; Jacobson, G.

    1985-04-01

    Cores from ten holes, drilled to a maximum depth of 30 m, on Tarawa atoll in the central Pacific have been utilised in a study of the Holocene development of the atoll. Four dominant lithologies, in descending order, are cay rock, unconsolidated sediment, corals and leached limestone. Petrographic and radiometric age analyses indicate that the Holocene reef has developed on a previous (last interglacial) reef; the latter shows the effects of both vadose and phreatic freshwater diagenesis. Hydrological investigations beneath the present islands indicate the presence of freshwater lenses up to 29 m thick; the modern lenses are unrelated to freshwater diagenetic imprints preserved within the limestones. Vertical accretion rates of 5 8 m/1000 years for the Holocene reef section on Tarawa are significantly higher than rates measured for other Pacific atolls. The dated coral sequences suggest a more rapid rate of sea level rise during the early Holocene, and a relatively earlier stabilisation of sea level than has been suggested previously.

  17. Environmental evolution of the southern Chukchi Sea in the Holocene

    NASA Astrophysics Data System (ADS)

    Gusev, E. A.; Anikina, N. Yu.; Derevyanko, L. G.; Klyuvitkina, T. S.; Polyak, L. V.; Polyakova, E. I.; Rekant, P. V.; Stepanova, A. Yu.

    2014-07-01

    The molluscan shells from three drill and two piston cores obtained in the southern Russian sector of the Chukchi Sea are dated by the AMS 14C measurement method back to 0.8-3.5 and 9.2-10.5 ka. The period of 9-10 ka was marked by increased sedimentation rates related to the transgression onset. The fossils in the lower Holocene section exhibit the successive upward replacement of brackish-water organisms by their marine counterparts. After the opening of the Bering Strait in the middle Holocene, the sedimentation was under influence of the increased bioproductivity of the waters. The climatic optimum in the Chukotka region corresponds to the early Holocene, while the late Holocene was characterized by the wider development of the ice cover on the shelf.

  18. Tracking Nile Delta Vulnerability to Holocene Change

    PubMed Central

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

    2013-01-01

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

  19. Saugus Iron Works: Life and Work at an Early American Industrial Site. Teaching with Historic Places.

    ERIC Educational Resources Information Center

    Whitman, Maryann

    In 1948 archeologists verified that a now overgrown and urbanized landscape along the Saugus River (Massachusetts) was the site of the Saugus Iron Works from 1646 until 1648. That discovery led to a careful, though partly conjectural, reconstruction of the first successful integrated ironmaking plant in the colonial America. The early Puritan…

  20. The Holocene warm-humid phases in the North China Plain as recorded by multi-proxy records

    NASA Astrophysics Data System (ADS)

    Cui, Jianxin; Zhou, Shangzhe; Chang, Hong

    2009-02-01

    The grain size and palinology of sediment and the frequency of 14C dada provide an integrated reconstruction of the Holocene warm-humid phases of the North China Plain. Two clear intense and long-lasting warm-humid phases were identified by comprehensive research in this region. The first phase was dated back to the early Holocene (9 000-7 000 a BP), and the second was centered at 5 000-3 000 a BP. The warm-humid episode between 9 000 and 7 000 a BP was also recognized at other sites showing global climatic trends rather than local events. Compared with the concern to the warm-humid phase of the early Holocene, the second one was not paid enough attention in the last few decades. The compilation of the Holocene paleoclimate data suggests that perhaps the second warm-humid phase was pervasive in monsoon region of China. In perspective of environmental archaeology, much attention should be devoted to it, because the flourish and adaptation of the Neolithic cultures and the building up of the first state seem to corresponding to the general warm-humid climatic conditions of this period. In addition, a warm-humid interval at 7 200-6 500 a BP was recognized by the grain size data from three sites. However, this warm-humid event was not shown in pollen assemblage and temporal distribution of 14C data. Perhaps, the resolution for climatic reconstruction from pollen and temporal distribution of 14C data cited here is relatively low and small-amplitude and short-period climatic events cannot be well reflected by the data. Due to the difference in locality and elevation of sampling site, as well as in resolution of proxy records, it is difficult to make precise correlation. Further work is needed in the future.

  1. Inside the "African cattle complex": animal burials in the holocene central Sahara.

    PubMed

    di Lernia, Savino; Tafuri, Mary Anne; Gallinaro, Marina; Alhaique, Francesca; Balasse, Marie; Cavorsi, Lucia; Fullagar, Paul D; Mercuri, Anna Maria; Monaco, Andrea; Perego, Alessandro; Zerboni, Andrea

    2013-01-01

    Cattle pastoralism is an important trait of African cultures. Ethnographic studies describe the central role played by domestic cattle within many societies, highlighting its social and ideological value well beyond its mere function as 'walking larder'. Historical depth of this African legacy has been repeatedly assessed in an archaeological perspective, mostly emphasizing a continental vision. Nevertheless, in-depth site-specific studies, with a few exceptions, are lacking. Despite the long tradition of a multi-disciplinary approach to the analysis of pastoral systems in Africa, rarely do early and middle Holocene archaeological contexts feature in the same area the combination of settlement, ceremonial and rock art features so as to be multi-dimensionally explored: the Messak plateau in the Libyan central Sahara represents an outstanding exception. Known for its rich Pleistocene occupation and abundant Holocene rock art, the region, through our research, has also shown to preserve the material evidence of a complex ritual dated to the Middle Pastoral (6080-5120 BP or 5200-3800 BC). This was centred on the frequent deposition in stone monuments of disarticulated animal remains, mostly cattle. Animal burials are known also from other African contexts, but regional extent of the phenomenon, state of preservation of monuments, and associated rock art make the Messak case unique. GIS analysis, excavation data, radiocarbon dating, zooarchaeological and isotopic (Sr, C, O) analyses of animal remains, and botanical information are used to explore this highly formalized ritual and the lifeways of a pastoral community in the Holocene Sahara.

  2. Fossil insects may provide unique information on structures and disturbances in past forest ecosystems - examples from Holocene studies in southern Sweden

    NASA Astrophysics Data System (ADS)

    Lemdahl, Geoffrey; Gustavsson, Gunnar; Olsson, Fredrik; Gaillard, Marie-José

    2010-05-01

    Insects are complex organisms that play an important role in all types of forest ecosystems. Insect remains are often abundant in waterlogged sediments and peat, and the majority of the fossils may be identified to species level, thus contributing with specific information. The occurrence of species feeding or confined to one or a few species of herbaceous plants, shrubs and trees may confirm or improve/refine the interpretations based on pollen and plant macrofossil analyses. Many insects, particularly ground living animals, select open, sun exposed habitats or closed shaded areas. Such indicators are valuable for reconstructions of forest/landscape openness. However, unique information can be provided by fossil insect assemblages. Insect studies carried out at two natural sites in southern Sweden with complete Holocene peat stratigraphies (Olsson and Lemdahl 2009) and a number of sites covering parts of the Holocene (e.g. Gaillard and Lemdahl 1994, Gustavsson et al. 2009) provide strong evidence on changes in forest structure and the occurrence and nature of disturbances. Studies in Britain have yielded similar results (e.g. Whitehouse 2006). Saproxylic beetles indicate the presence of dead wood, which clearly was a more prominent component in ancient woodlands than in present forests, and beetles confined to wood mould suggest the presence of large hollow trees. Finds of pyrophilic species, of which some are very rare in European woodlands today, together with layers of charcoal, suggest that fire was a major disturbance factor during most of the Holocene in southern Sweden. Whereas macroscopic charcoal fragments indicate local fires, the presence of pyrophilic insects is an indication of continuous fire activity at the regional spatial scale. Remains of dung beetles indicate extensive grazing by megaherbivores during early Holocene, and more intensive grazing during late Holocene, whereas such indicators are absent from mid Holocene records, which correlates

  3. 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.

  4. Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus

    PubMed Central

    Reisz, Robert R.; Evans, David C.; Roberts, Eric M.; Sues, Hans-Dieter; Yates, Adam M.

    2012-01-01

    The extensive Early Jurassic continental strata of southern Africa have yielded an exceptional record of dinosaurs that includes scores of partial to complete skeletons of the sauropodomorph Massospondylus, ranging from embryos to large adults. In 1976 an incomplete egg clutch including in ovo embryos of this dinosaur, the oldest known example in the fossil record, was collected from a road-cut talus, but its exact provenance was uncertain. An excavation program at the site started in 2006 has yielded multiple in situ egg clutches, documenting the oldest known dinosaurian nesting site, predating other similar sites by more than 100 million years. The presence of numerous clutches of eggs, some of which contain embryonic remains, in at least four distinct horizons within a small area, provides the earliest known evidence of complex reproductive behavior including site fidelity and colonial nesting in a terrestrial vertebrate. Thus, fossil and sedimentological evidence from this nesting site provides empirical data on reproductive strategies in early dinosaurs. A temporally calibrated optimization of dinosaurian reproductive biology not only demonstrates the primary significance of the Massospondylus nesting site, but also provides additional insights into the initial stages of the evolutionary history of dinosaurs, including evidence that deposition of eggs in a tightly organized single layer in a nest evolved independently from brooding. PMID:22308330

  5. Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus.

    PubMed

    Reisz, Robert R; Evans, David C; Roberts, Eric M; Sues, Hans-Dieter; Yates, Adam M

    2012-02-14

    The extensive Early Jurassic continental strata of southern Africa have yielded an exceptional record of dinosaurs that includes scores of partial to complete skeletons of the sauropodomorph Massospondylus, ranging from embryos to large adults. In 1976 an incomplete egg clutch including in ovo embryos of this dinosaur, the oldest known example in the fossil record, was collected from a road-cut talus, but its exact provenance was uncertain. An excavation program at the site started in 2006 has yielded multiple in situ egg clutches, documenting the oldest known dinosaurian nesting site, predating other similar sites by more than 100 million years. The presence of numerous clutches of eggs, some of which contain embryonic remains, in at least four distinct horizons within a small area, provides the earliest known evidence of complex reproductive behavior including site fidelity and colonial nesting in a terrestrial vertebrate. Thus, fossil and sedimentological evidence from this nesting site provides empirical data on reproductive strategies in early dinosaurs. A temporally calibrated optimization of dinosaurian reproductive biology not only demonstrates the primary significance of the Massospondylus nesting site, but also provides additional insights into the initial stages of the evolutionary history of dinosaurs, including evidence that deposition of eggs in a tightly organized single layer in a nest evolved independently from brooding.

  6. Early reproductive success of the hard clam (Mercenaria mercenaria) from Five Sites in Long Island Sound

    SciTech Connect

    Stiles, S.; Choromanski, J.; Nelson, D.; Miller, J.; Greig, R.; Sennefelder, G. )

    1991-09-01

    Early reproductive success of hard clams (Mercenaria mercenaria) in Long Island Sound was measured to determine whether pollution may have adverse effects on fragile recruitment to fisheries. Clams were collected at five sites in 1987 when ready to spawn naturally, along with water from within 39 cm of the bottom. Levels of polychlorinated biphenyls (PCBs), copper, and cadmium were measured in the mature gonad and were found to be generally low. Clams were spawned and the gametes were collected and cultured both in their respective site waters and in reference laboratory seawater. In both site and reference seawater, embryos of clams from the most highly industrialized area (Bridgeport) with higher contaminant levels exhibited more irregularity in chromosome numbers and greater larval abnormality, possible indicators of long-term sublethal effects. Fertilization and early meiotic success at 1 to 1 1/2 h were significantly lower for clams from Norwalk than for those from Greenwich. At 48 h, mortality was lowest for Greenwich larvae and highest for Norwalk larvae in their respective site waters, but the mortality for these two sites was significantly lower than for other sites in reference water. This suggests sporadically poor environmental quality. Milford larvae also had significant mortality. Population-level significance of pollution effects on clam reproduction will depend on how contaminated the environment is over the entire reproductive season of the clams in Long Island Sound, and over how large a portion of the spawning grounds.

  7. Climate-driven expansion of blanket bogs in Britain during the Holocene

    NASA Astrophysics Data System (ADS)

    Gallego-Sala, A. V.; Charman, D. J.; Harrison, S. P.; Li, G.; Prentice, I. C.

    2016-01-01

    Blanket bog occupies approximately 6 % of the area of the UK today. The Holocene expansion of this hyperoceanic biome has previously been explained as a consequence of Neolithic forest clearance. However, the present distribution of blanket bog in Great Britain can be predicted accurately with a simple model (PeatStash) based on summer temperature and moisture index thresholds, and the same model correctly predicts the highly disjunct distribution of blanket bog worldwide. This finding suggests that climate, rather than land-use history, controls blanket-bog distribution in the UK and everywhere else. We set out to test this hypothesis for blanket bogs in the UK using bioclimate envelope modelling compared with a database of peat initiation age estimates. We used both pollen-based reconstructions and climate model simulations of climate changes between the mid-Holocene (6000 yr BP, 6 ka) and modern climate to drive PeatStash and predict areas of blanket bog. We compiled data on the timing of blanket-bog initiation, based on 228 age determinations at sites where peat directly overlies mineral soil. The model predicts that large areas of northern Britain would have had blanket bog by 6000 yr BP, and the area suitable for peat growth extended to the south after this time. A similar pattern is shown by the basal peat ages and new blanket bog appeared over a larger area during the late Holocene, the greatest expansion being in Ireland, Wales, and southwest England, as the model predicts. The expansion was driven by a summer cooling of about 2 °C, shown by both pollen-based reconstructions and climate models. The data show early Holocene (pre-Neolithic) blanket-bog initiation at over half of the sites in the core areas of Scotland and northern England. The temporal patterns and concurrence of the bioclimate model predictions and initiation data suggest that climate change provides a parsimonious explanation for the early Holocene distribution and later expansion of

  8. Climate-driven expansion of blanket bogs in Britain during the Holocene

    NASA Astrophysics Data System (ADS)

    Gallego-Sala, A. V.; Charman, D. J.; Harrison, S. P.; Li, G.; Prentice, I. C.

    2015-10-01

    Blanket bog occupies approximately 6 % of the area of the UK today. The Holocene expansion of this hyperoceanic biome has previously been explained as a consequence of Neolithic forest clearance. However, the present distribution of blanket bog in Great Britain can be predicted accurately with a simple model (PeatStash) based on summer temperature and moisture index thresholds, and the same model correctly predicts the highly disjunct distribution of blanket bog worldwide. This finding suggests that climate, rather than land-use history, controls blanket-bog distribution in the UK and everywhere else. We set out to test this hypothesis for blanket bogs in the UK using bioclimate envelope modelling compared with a database of peat initiation age estimates. We used both pollen-based reconstructions and climate model simulations of climate changes between the mid-Holocene (6000 yr BP, 6 ka) and modern climate to drive PeatStash and predict areas of blanket bog. We compiled data on the timing of blanket-bog initiation, based on 228 age determinations at sites where peat directly overlies mineral soil. The model predicts large areas of northern Britain would have had blanket bog by 6000 yr BP, and the area suitable for peat growth extended to the south after this time. A similar pattern is shown by the basal peat ages and new blanket bog appeared over a larger area during the late Holocene, the greatest expansion being in Ireland, Wales and southwest England, as the model predicts. The expansion was driven by a summer cooling of about 2 °C, shown by both pollen-based reconstructions and climate models. The data show early Holocene (pre-Neolithic) blanket-bog initiation at over half of the sites in the core areas of Scotland, and northern England. The temporal patterns and concurrence of the bioclimate model predictions and initiation data suggest that climate change provides a parsimonious explanation for the early Holocene distribution and later expansion of blanket

  9. Holocene environmental conditions in South Georgia - a multi-proxy study on a coastal marine record

    NASA Astrophysics Data System (ADS)

    Berg, Sonja; Jivcov, Sandra; Groten, Sonja; Viehberg, Finn; Rethemeyer, Janet; Melles, Martin

    2014-05-01

    The Holocene environmental history of the sub-Antarctic island of South Georgia so far has been reconstructed from lake sediments, peat records and geomorphological observations. The data available indicate a postglacial ice retreat, which reached the coastal areas around the early Holocene. Climate reconstructions for the Holocene, on the other hand, provide a more complex picture, which may partly result from the influence of local effects. We present preliminary results of a multi-proxy study on a sediment core recovered in early 2013 from a coastal marine inlet (Little Jason Lagoon) in Cumberland West Bay. The results include elemental data (high resolution XRF-scans, total organic carbon (TOC), nitrogen, and sulphur, lipid biomarkers, and macrofossil data. The sediment core comprises a c. 11m long sequence, which contains a complete record of postglacial sedimentation in the inlet. Its base is formed by a diamicton, indicating a former glaciation of the site, which is overlain by well-stratified sediments passing over into more massive muds in the upper past. A radiocarbon age from the organic-rich sediments above the diamicton provides a first estimate of 9700 14C years BP for a minimum age of ice retreat. We use the elemental data to infer changes in clastic input (e.g., K/Ti ratios), productivity (TOC) and water salinity (Cl counts) in the course of the Holocene. While Little Jason Lagoon has a connection to the sea today (sill depth c. 1 m), a decrease in Cl counts downcore points to fresher conditions in the early part of the record. This could be an indicator for changing relative sea level and/or changes in the amounts of freshwater inflow from the catchment. Macroscopic plant remains and lipid biomarkers (n-alkanes, n-fatty acids and sterols) provide information on the terrestrial vegetation in the catchment and its changes through time as well as on the influence of marine conditions in the lagoon. We suggest that the record from Little Jason Lagoon

  10. Holocene zooarchaeology and global change: Examples from the western US

    SciTech Connect

    Lyman, R.L. . Dept. of Anthropology)

    1993-03-01

    Mammalian faunal remains recovered from archaeological sites in the western US indicate that during the Holocene some taxa altered their ranges in response to climatic change whereas other taxa altered their ranges or migrational patterns due to historic commercial activities. The range of pygmy cottontail (Brachylagus idahoensis) in eastern Washington state shrank during the last 4,000 yrs in concert with a decrease in the range of big sagebrush (Artemisia tridentata). Recent biological surveys indicate that this taxon no longer occupies areas where it was found early in the 20th century, suggesting modern agricultural practices of burning and plowing sagebrush resulted in their local extirpation. Remains of newborn and female California sea lions (Zalophus californianus) and northern fur seals (Callorhinus ursinus) from late Holocene sites on the Oregon coast indicate that these species bred and pupped on this coast until the end of the 19 century. The absence of historical reports of these behaviors suggests that commercial exploitation of these species around the turn of the century resulted in the extirpation of local resident populations. In 1925 mountain goats (Oreamnos americanus) were introduced to what was to become Olympic National Park in Washington in 1938. Modern wildlife management policy calls for removal of this exotic, non-native species from Park lands. However, biogeographic data from archaeological excavations indicate great potential that mountain goats were extant on Park lands prehistorically. While conclusive evidence is not yet available, debates presently underway clearly indicate that the fossil record must play a role in modern wildlife management decisions.

  11. Centrosome movement in the early divisions of Caenorhabditis elegans: A cortical site determining centrosome position

    SciTech Connect

    Hyman, A.A. )

    1989-09-01

    In Caenorhabditis elegans embryos, early blastomeres of the P cell lineage divide successively on the same axis. This axis is a consequence of the specific rotational movement of the pair of centrosomes and nucleus. A laser has been used to perturb the centrosome movements that determine the pattern of early embryonic divisions. The results support a previously proposed model in which a centrosome rotates towards its correct position by shortening of connections, possibly microtubules, between a centrosome and a defined site on the cortex of the embryo.

  12. Centrosome movement in the early divisions of Caenorhabditis elegans: a cortical site determining centrosome position

    PubMed Central

    1989-01-01

    In Caenorhabditis elegans embryos, early blastomeres of the P cell lineage divide successively on the same axis. This axis is a consequence of the specific rotational movement of the pair of centrosomes and nucleus (Hyman, A. A., and J. G. White. 1987. J. Cell Biol. 105:2123-2135). A laser has been used to perturb the centrosome movements that determine the pattern of early embryonic divisions. The results support a previously proposed model in which a centrosome rotates towards its correct position by shortening of connections, possibly microtubules, between a centrosome and a defined site on the cortex of the embryo. PMID:2768338

  13. Report of the Peer Review Panel on the early site suitability evaluation of the Potential Repository Site at Yucca Mountain, Nevada; Yucca Mountain Site Characterization Project

    SciTech Connect

    1992-01-01

    The US Department of Energy (DOE) Yucca mountain Site Characterization Project Office (YMPO) assigned Science Applications International Corporation (SAIC), the Technical and Management Support Services (T&MSS) contractor to the YmPo, the task of conducting an Early Site Suitability Evaluation (ESSE) of the Yucca mountain site as a potential site for a high-level radioactive waste repository. First, the assignment called for the development of a method to evaluate a single site against the DOE General Guidelines for Recommendation of Sites for Nuclear Waste Repositories, 10 CFR Part 960. Then, using this method, an evaluation team, the ESSE Core Team, of senior YMP scientists, engineers, and technical experts, evaluated new information obtained about the site since publication of the final Environmental Assessment (DOE, 1986) to determine if new suitability/unsuitability findings could be recommended. Finally, the Core Team identified further information and analyses needed to make final determinations for each of the guidelines. As part of the task, an independent peer review of the ESSE report has been conducted. Expertise was solicited that covered the entire spectrum of siting guidelines in 10 CFR Part 960 in order to provide a complete, in-depth critical review of the data evaluated and cited in the ESSE report, the methods used to evaluate the data, and the conclusions and recommendations offered by the report. Fourteen nationally recognized technical experts (Table 2) served on the Peer Review Panel. The comments from the Panel and the responses prepared by the ESSE Core Team, documented on formal Comment Response Forms, constitute the body of this document.

  14. Holocene fire regimes and treeline migration rates in sub-arctic Canada

    NASA Astrophysics Data System (ADS)

    Sulphur, Kyle C.; Goldsmith, Shantal A.; Galloway, Jennifer M.; Macumber, Andrew; Griffith, Fritz; Swindles, Graeme T.; Patterson, R. Timothy; Falck, Hendrik; Clark, Ian D.

    2016-10-01

    Holocene climate change resulted in major vegetation reorganization in sub-arctic Canada near modern treeline. However, little is known of the effects of long-term climate change on boreal forest composition and fire regimes below treeline in this region. We present a high-resolution vegetation and fire history from two sites within the modern boreal forest in the central Northwest Territories, Canada, to provide new insight on sub-arctic vegetation response to Holocene climate dynamics and the role of fire in boreal ecosystems. Palynological analysis of sediments retrieved from Waite and Danny's lakes (informal) is used to reconstruct regional vegetation dynamics and boreal fire regimes. The longer Danny's Lake record documents treeline expansion beginning at ca. 7430-7220 cal yr BP. Integration of our new data with previous work shows that treeline expanded between ca. 4050 cal. yr BP and ca. 3840 cal yr BP at a rate of ca. 50 m/yr in response to the 1-2 °C increase in temperature estimated for the Holocene Thermal Maximum. Forest fires were relatively frequent during the early Holocene, before declining in frequency in response to development of cooler and wetter climate conditions associated with the Neoglacial (beginning after ca. 2200-2320 cal yr BP). We document a trend of increasing fire frequency in the 20th century that is correlated with warming at this time. These dynamics south of modern treeline provide insight into factors creating heterogeneity in plant community responses to large-scale climate events in high northern latitudes and suggest that large scale reorganization of boreal vegetation and fire regimes can be expected over the coming decades.

  15. Elucidating the Holocene Relative Sea-Level History of the US Atlantic Coast

    NASA Astrophysics Data System (ADS)

    Engelhart, S. E.; Anderson, C.; Hill, D.; Horton, B. P.; Peltier, W. R.; van de Plassche, O.; Shennan, I.; Thieler, E. R.; Tornqvist, T. E.

    2007-12-01

    There is an urgent need for a re-assessment of the quality of Holocene relative sea-level (RSL) observations from the Atlantic and Gulf coasts of the United States. Holocene RSL data provide an essential benchmark to compare against other records of RSL change in the last 100-150 years. Only high quality sea-level data reveal spatial and temporal variations in crustal movements since the Last Glacial Maximum and provide a vital constraint upon dynamical models of the Glacial Isostatic Adjustment (GIA) process. We require an accurate model of the GIA process to inform the global data set currently being produced on the time dependence of the gravitational field of the planet by the Gravity Recovery and Climate Experiment (GRACE). We have compiled database of 1400 possible sea-level index points for the Atlantic coast of the United States. These unvalidated data contain much scatter due to concepts inherent in their original interpretation. They rarely allow for other factors such as sediment compaction and tidal range variation. Following validation, results from Delaware and North Carolina show a rapid rise in RSL from the early to mid Holocene, with no evidence of sea- level above present. They also differ somewhat from GIA model predictions. Rates of RSL change during the late Holocene divide into three broad zones: (1) Maine to Boston, MA ~ RSL rise of less than 1 mm yr-1; (2) Cape Cod, MA to Maryland ~ RSL rise between 1 and 3 mm yr-1; and (3) North Carolina to South Carolina ~ RSL rise less than 1 mm yr-1. Comparison with tide-gauge records demonstrate an increase of at least 1 mm yr-1 at all sites since AD 1900.

  16. The chin as a donor site in early secondary osteoplasty: a retrospective clinical and radiological evaluation.

    PubMed

    Hoppenreijs, T J; Nijdam, E S; Freihofer, H P

    1992-04-01

    26 unilateral cleft palate patients received an autogenous bicortical chin bone graft for early reconstruction of the alveolar process. In the evaluation of the donor site, 4% of the anterior teeth showed a negative pulpal sensibility, less than 1% a peri-apical granuloma and 12% pulp canal obliteration. The tooth buds of the canines showed developmental disturbances in 6%. Exposure of unerupted canines should be avoided, and a 5 mm safety margin is advised. Based on its architecture, topographic accessibility, minimal post-operative morbidity and absence of visible scars, the chin can be considered to be a very useful donor site in bone grafting procedures.

  17. 10 CFR 51.75 - Draft environmental impact statement-construction permit, early site permit, or combined license.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... evaluation of alternative energy sources, unless these matters are addressed in the early site permit... 10 Energy 2 2012-01-01 2012-01-01 false Draft environmental impact statement-construction permit, early site permit, or combined license. 51.75 Section 51.75 Energy NUCLEAR REGULATORY...

  18. 10 CFR 2.623 - Notice of hearing on application for early review of site suitability issues in combined license...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Notice of hearing on application for early review of site suitability issues in combined license proceeding. 2.623 Section 2.623 Energy NUCLEAR REGULATORY COMMISSION... Limited Work Authorizations Early Partial Decisions on Site Suitability-Combined License Under 10 Cfr...

  19. Long-term deforestation in NW Spain: linking the Holocene fire history to vegetation change and human activities

    NASA Astrophysics Data System (ADS)

    Kaal, Joeri; Carrión Marco, Yolanda; Asouti, Eleni; Martín Seijo, Maria; Martínez Cortizas, Antonio; Costa Casáis, Manuela; Criado Boado, Felipe

    2011-01-01

    The Holocene fire regime is thought to have had a key role in deforestation and shrubland expansion in Galicia (NW Spain) but the contribution of past societies to vegetation burning remains poorly understood. This may be, in part, due to the fact that detailed fire records from areas in close proximity to archaeological sites are scarce. To fill this gap, we performed charcoal analysis in five colluvial soils from an archaeological area (Campo Lameiro) and compared the results to earlier studies from this area and palaeo-ecological literature from NW Spain. This analysis allowed for the reconstruction of the vegetation and fire dynamics in the area during the last ca 11 000 yrs. In the Early Holocene, Fabaceae and Betula sp. were dominant in the charcoal record. Quercus sp. started to replace these species around 10 000 cal BP, forming a deciduous forest that prevailed during the Holocene Thermal Maximum until ˜5500 cal BP. Following that, several cycles of potentially fire-induced forest regression with subsequent incomplete recovery eventually led to the formation of an open landscape dominated by shrubs (Erica sp. and Fabaceae). Major episodes of forest regression were (1) ˜5500-5000 cal BP, which marks the mid-Holocene cooling after the Holocene Thermal Maximum, but also the period during which agropastoral activities in NW Spain became widespread, and (2) ˜2000-1500 cal BP, which corresponds roughly to the end of the Roman Warm Period and the transition from the Roman to the Germanic period. The low degree of chronological precision, which is inherent in fire history reconstructions from colluvial soils, made it impossible to distinguish climatic from human-induced fires. Nonetheless, the abundance of synanthropic pollen indicators (e.g. Plantago lanceolata and Urtica dioica) since at least ˜6000 cal BP strongly suggests that humans used fire to generate and maintain pasture.

  20. Holocene Sea Surface and Subsurface Water Mass Variability Reconstructed from Temperature and Sea-ice Proxies in Fram Strait

    NASA Astrophysics Data System (ADS)

    Werner, Kirstin; Spielhagen, Robert F.; Müller, Juliane; Husum, Katrine; Kandiano, Evgenia S.; Polyak, Leonid

    2016-04-01

    In two high-resolution sediment cores from the West Spitsbergen continental margin we investigated planktic foraminiferal, biomarker and dinocyst proxy data in order to reconstruct surface and subsurface water mass variability during the Holocene. The two study sites are today influenced by northward flowing warm and saline Atlantic Water. Both foraminiferal and dinocyst (de Vernal et al., 2013) temperature reconstructions indicate a less-stratified, ice-free, nutrient-rich summer surface ocean with strong Atlantic Water advection between 10.6 and 8.5 cal ka BP, likely related to maximum July insolation during the early Holocene. Sea surface to subsurface water temperatures of up to 6°C prevailed until ca 5 cal ka BP. A weakened contribution of Atlantic Water is found when subsurface temperatures strongly decreased with minimum values between ca 4 and 3 cal ka BP. High planktic foraminifer shell fragmentation and increased oxygen isotope values of the subpolar planktic foraminifer species Turborotalita quinqueloba as well as increasing concentrations of the sea ice biomarker IP25 further indicate cool conditions. Indices associated with IP25 as well as dinocyst data suggest a sustained cooling and consequently sea-ice increase during the late Holocene. However, planktic foraminiferal data indicate a slight return of stronger subsurface influx of Atlantic Water since ca 3 cal ka BP. The observed decoupling of cooling surface and warming subsurface waters during the later Holocene might be attributed to a strong pycnocline layer separating cold sea-ice fed surface waters from enhanced subsurface Atlantic Water advection. Reference: de Vernal, A., Hillaire-Marcel, C., Rochon, A., Fréchette, B., Henry, M., Solignac, S., Bonnet, S., 2013. Dinocyst-based reconstructions of sea ice cover concentration during the Holocene in the Arctic Ocean, the northern North Atlantic Ocean and its adjacent seas. Quaternary Science Reviews 79, 111-121.

  1. Peatland Carbon Dynamics on the North Slope of Alaska During the Holocene: The Role of Climate, Sea Ice, and Buried Peat

    NASA Astrophysics Data System (ADS)

    Yu, Zicheng; Massa, Charly; Cleary, Kathleen; Jones, Benjamin; Grosse, Guido

    2014-05-01

    Our recent and ongoing data syntheses indicate that peatlands accumulated more carbon (C) during past warm climate intervals in the circum-Arctic region, including Alaska. In particular, peak C accumulations have been observed during the Holocene Thermal Maximum (HTM) in the early Holocene when summer insolation was higher. However, we do not know the regional patterns and impacts of sea-ice change on Holocene peat C accumulation, especially around the Arctic Ocean where increased vegetation productivity has already been linked to sea ice declines in recent decades. Here we review Holocene peatland and tundra C accumulation records on the North Slope, along with our preliminary results, to investigate spatiotemporal pattern of C accumulation and the possible role of sea-ice change. As in many other northern high-latitude regions, most peatlands on the North Slope initiated in the early Holocene. Several discontinuous and low-resolution peat accumulation records from the region appear to show high accumulation rates or high C content in the early Holocene. In addition, we note that many peatlands that existed during the earlier Holocene on the North Slope have disappeared and are presently covered by mineral soils under tundra or eolian sandy deposits, indicating that current peatland extent is only a fraction of early Holocene extent. In contrast to highest C accumulation rates in the early Holocene, our preliminary results from a 70-cm-long peat core (lat. 70.71 N; long. 153.87 W) from northwest Teshekpuk Lake, near the Teshekpuk Lake Observatory on the Arctic Coastal Plain, about 10 km from the Arctic Ocean, shows a very different pattern. The highest C accumulation of 12.7 gC/m2/yr is observed after 2.9 ka, much higher than the rate of 3.8 gC/m2/yr at 8.1-2.9 ka. Furthermore, the period with high C rates after 2.9 ka at this site was dominated by well-preserved peat mosses (Sphagnum) and with abundant leaf fragments, likely from dwarf birch (Betula nana). This

  2. Mass-spectrometric U-series dates for Israeli Neanderthal/early modern hominid sites.

    PubMed

    McDermott, F; Grün, R; Stringer, C B; Hawkesworth, C J

    1993-05-20

    The nature of the relationship between Neanderthals and early modern Homo sapiens is controversial, yet it is fundamental to our understanding of early human evolution. The Middle Palaeolithic sites of Israel are critical to this debate, because unlike those of western Europe and Africa they contain both Neanderthal (at Tabun and Kebara for example) and anatomically modern hominids (as at Skhul and Qafzeh). Here we present new mass spectrometric 230Th/234U dates for dental fragments from the Middle Palaeolithic burial sites of Tabun, Qafzeh and Skhul. These data, combined with published ages from electron spin resonance (ESR), provide compelling evidence that the Tabun Neanderthals and Qafzeh early modern Homo sapiens were approximately coeval in the southern Levant some 100 +/- 5 kyr ago, but indicate that some of the Skhul material is younger. The study also shows that combined mass-spectrometric 230Th/234U and ESR dating is an invaluable technique for dating archaeological sites beyond the range of radiocarbon dating.

  3. Early atmospheric detection of carbon dioxide from carbon capture and storage sites

    PubMed Central

    Pak, Nasrin Mostafavi; Rempillo, Ofelia; Norman, Ann-Lise; Layzell, David B.

    2016-01-01

    ABSTRACT The early atmospheric detection of carbon dioxide (CO2) leaks from carbon capture and storage (CCS) sites is important both to inform remediation efforts and to build and maintain public support for CCS in mitigating greenhouse gas emissions. A gas analysis system was developed to assess the origin of plumes of air enriched in CO2, as to whether CO2 is from a CCS site or from the oxidation of carbon compounds. The system measured CO2 and O2 concentrations for different plume samples relative to background air and calculated the gas differential concentration ratio (GDCR = −ΔO2/ΔCO2). The experimental results were in good agreement with theoretical calculations that placed GDCR values for a CO2 leak at 0.21, compared with GDCR values of 1–1.8 for the combustion of carbon compounds. Although some combustion plume samples deviated in GDCR from theoretical, the very low GDCR values associated with plumes from CO2 leaks provided confidence that this technology holds promise in providing a tool for the early detection of CO2 leaks from CCS sites.  Implications: This work contributes to the development of a cost-effective technology for the early detection of leaks from sites where CO2 has been injected into the subsurface to enhance oil recovery or to permanently store the gas as a strategy for mitigating climate change. Such technology will be important in building public confidence regarding the safety and security of carbon capture and storage sites. PMID:27111469

  4. Early Holocene and Late Pleistocene slip rates of the southern Dead Sea Fault determined from 10Be cosmogenic dating of offset alluvial deposits

    NASA Astrophysics Data System (ADS)

    Le BéOn, Maryline; Klinger, Yann; Al-Qaryouti, Mahmoud; MéRiaux, Anne-Sophie; Finkel, Robert C.; Elias, Ata; Mayyas, Omar; Ryerson, Frederick J.; Tapponnier, Paul

    2010-11-01

    Two sites located along the Wadi Araba Fault (WAF) segment of the Dead Sea Fault are targeted for tectonic-morphological analysis. 10Be cosmogenic radionuclide (CRN) dating of embedded cobbles is used to constrain the age of offset alluvial surfaces. At the first site a 48 ± 7 m offset alluvial fan, for which 10Be CRN model ages average 11.1 ± 4.3 ka, yield a slip rate of 5.4 ± 2.7 mm/a, with conservative bounds of 1.3-16.4 mm/a. At the second site the scattered distributions of the 10Be CRN ages from an offset bajada attest to the complex processes involved in sediment transport and emplacement. There, two offsets were identified. The 160 ± 8 m offset of an incised alluvial fan dated at 37 ± 5 ka shows a slip rate of 4.5 ± 0.9 mm/a, with a conservative minimum value of 3.2 mm/a. A larger offset, 626 ± 37 m, is derived from a prominent channel incised into the bajada. Cobbles from the bajada surface have ages from 33 to 141 ka, with a mean of 87 ± 26 ka. A slip rate of 8.1 ± 2.9 mm/a is derived from the mean age, with conservative bounds of 3.8-22.1 mm/a. These results and other published slip rates along the linear WAF segment, from GPS to geological time scales, lack the resolution to fully resolve the question of temporal variations versus consistency of the fault slip rate of the WAF. Yet, given the uncertainties, they are not inconsistent with each other.

  5. A high resolution Late Glacial to Holocene record of climatic and environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania)

    NASA Astrophysics Data System (ADS)

    Lacey, Jack; Francke, Alexander; Leng, Melanie; Vane, Chris; Wagner, Bernd

    2015-04-01

    Lake Ohrid (Macedonia/Albania) is one of the world's oldest lakes and is renowned for its high degree of biological diversity. It is the target site for the ICDP SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) project, an international research initiative to study the links between geology, environment and the evolution of endemic taxa. In 2011 a 10-meter core was recovered from the western shore of Lake Ohrid adjacent to the Lini Peninsula. Here we present high-resolution stable isotope and geochemical data from this core through the Late Glacial to Holocene to reconstruct past climate and hydrology (TIC, δ18Ocalcite, δ13Ccalcite) as well as the terrestrial and aquatic vegetation response to climate (TOC, TOC/N, δ13Corganic, Rock-Eval pyrolysis). The data identify 3 main zones: (1) the Late Glacial-Holocene transition represented by low TIC, TOC and higher isotope values, (2) the early to mid-Holocene characterised by higher TOC, TOC/N and lower δ18Ocalcite, and (3) the late Holocene which shows a marked decrease in TIC and TOC. In general there is an overall trend of increasing δ18Ocalcite from 9 ka to present, suggesting progressive aridification through the Holocene, which is consistent with previous records from Lake Ohrid and the wider Mediterranean region. Several proxies show commensurate excursions that imply the impact of short-term climate oscillations, such as the 8.2 ka event and the Little Ice Age. This is the best-dated and highest resolution archive of Late Glacial and Holocene climate from Lake Ohrid and confirms the overriding influence of the North Atlantic in the north-eastern Mediterranean. The data presented set the context for the SCOPSCO project cores recovered in spring-summer 2013 dating back into the Lower Pleistocene, and will act as a recent calibration to reconstruct climate and hydrology over the entire lake history.

  6. Precipitation variability of the Grand Canyon region, 1893 through 2009, and its implications for studying effects of gullying of Holocene terraces and associated archeological sites in Grand Canyon, Arizona

    USGS Publications Warehouse

    Hereford, Richard; Bennett, Glenn E.; Fairley, Helen C.

    2014-01-01

    A daily precipitation dataset covering a large part of the American Southwest was compiled for online electronic distribution (http://pubs.usgs.gov/of/2014/1006/). The dataset contains 10.8 million observations spanning January 1893 through January 2009 from 846 weather stations in six states and 13 climate divisions. In addition to processing the data for distribution, water-year totals and other statistical parameters were calculated for each station with more than 2 years of observations. Division-wide total precipitation, expressed as the average deviation from the individual station means of a climate division, shows that the region—including the Grand Canyon, Arizona, area—has been affected by alternating multidecadal episodes of drought and wet conditions. In addition to compiling and analyzing the long-term regional precipitation data, a second dataset consisting of high-temporal-resolution precipitation measurements collected between November 2003 and January 2009 from 10 localities along the Colorado River in Grand Canyon was compiled. An exploratory study of these high-temporal-resolution precipitation measurements suggests that on a daily basis precipitation patterns are generally similar to those at a long-term weather station in the canyon, which in turn resembles the patterns at other long-term stations on the canyon rims; however, precipitation amounts recorded by the individual inner canyon weather stations can vary substantially from station to station. Daily and seasonal rainfall patterns apparent in these data are not random. For example, the inner canyon record, although short and fragmented, reveals three episodes of widespread, heavy precipitation in late summer 2004, early winter 2005, and summer 2007. The 2004 event and several others had sufficient rainfall to initiate potentially pervasive erosion of the late Holocene terraces and related archeological features located along the Colorado River in Grand Canyon.

  7. Extraction of Functional Binding Sites from Unique Regulatory Regions: The Drosophila Early Developmental Enhancers

    PubMed Central

    Papatsenko, Dmitri A.; Makeev, Vsevolod J.; Lifanov, Alex P.; Régnier, Mireille; Nazina, Anna G.; Desplan, Claude

    2002-01-01

    The early developmental enhancers of Drosophila melanogaster comprise one of the most sophisticated regulatory systems in higher eukaryotes. An elaborate code in their DNA sequence translates both maternal and early embryonic regulatory signals into spatial distribution of transcription factors. One of the most striking features of this code is the redundancy of binding sites for these transcription factors (BSTF). Using this redundancy, we explored the possibility of predicting functional binding sites in a single enhancer region without any prior consensus/matrix description or evolutionary sequence comparisons. We developed a conceptually simple algorithm, Scanseq, that employs an original statistical evaluation for identifying the most redundant motifs and locates the position of potential BSTF in a given regulatory region. To estimate the biological relevance of our predictions, we built thorough literature-based annotations for the best-known Drosophila developmental enhancers and we generated detailed distribution maps for the most robust binding sites. The high statistical correlation between the location of BSTF in these experiment-based maps and the location predicted in silico by Scanseq confirmed the relevance of our approach. We also discuss the definition of true binding sites and the possible biological principles that govern patterning of regulatory regions and the distribution of transcriptional signals. PMID:11875036

  8. High-resolution multi-molecular stratigraphic records from North Atlantic drift sediments (ODP Sites 980, 984) reflecting Holocene climate and ocean dynamics

    NASA Astrophysics Data System (ADS)

    Holtvoeth, J.; Wagner, T.; Montlucon, D.; Mollenhauer, G.; McManus, J. F.; Oppo, D. W.; Eglinton, T. I.

    2005-12-01

    The North Atlantic plays an important role as the source region for northern component waters of thermohaline circulation. The hydrological system is highly sensitive to climatic changes. Underlying drift sediments record both changes in the hydrological system (lateral advection) and in `direct' material input from surface waters (primary production and eolian supply), and therefore represent excellent archives for past ocean and regional climate variability. Two sediment cores from North Atlantic drift sediments were taken during ODP Leg 162 (Site 980, Feni Drift, 55°N 15°W, water depth 2179 m, and Site 984, Bjorn Drift, 61°N 24°W, water depth 1648 m). While both sites experience similar atmospheric forcing, the present-day Bjorn Drift is bathed by Iceland-Scotland Overflow Water, while the Feni Drift is influenced by more southern sourced waters. Both sites exhibit exceptionally high sedimentation rates and thus enable reconstruction of climate-related changes within the North Atlantic with high temporal resolution. The composition of the organic matter (OM) in these sediments is closely coupled to the dynamics of the environment. Key factors that control quantity and quality of OM from marine and terrigenous sources in the drift sediments are surface water temperature and nutrient supply (marine primary productivity), wind speed (eolian supply of terrigenous OM), and strength and direction of bottom water currents (lateral redistribution of OM and export from continental margins). This study seeks evidence for rapid climate changes through development of high-resolution multi-molecular stratigraphic records of the sedimentary OM using Gas Chromatography/Time-Of-Flight Mass Spectrometry (GC-TOF-MS) analysis of total lipid extracts. We present high-resolution (< 100 yr) molecular proxy records from both ODP sites that indicate changes in heat transport, marine productivity, and terrigenous supply from the Last Glacial Maximum to the present. Alkenones

  9. 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.

  10. 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

  11. Changes in Colorado Subalpine Fen Peat Stratigraphy and Humification During the Holocene

    NASA Astrophysics Data System (ADS)

    Sullivan, D. G.

    2013-12-01

    This project focuses on the record of peat stratigraphy and decomposition preserved in cores taken from minerotrophic peatlands in Colorado. Subalpine peatlands in the Colorado Rocky Mountains and in the Colorado Plateau cover only about 2% of the state's land area, yet these wetlands provide important wildlife habitat and ecosystem services. The peatlands in Colorado are fens, and, while summer precipitation contributes to the local hydrology, the fens are only found in locations where winter snowpack persists long enough into the summers to maintain sufficiently high water tables to preserve the peat. We hypothesized that changes in summer precipitation and winter snowpack through the Holocene would be evident in the degree of peat humification and stratigraphy. We were interested in determining how warmer summer conditions early in the Holocene influenced precipitation, particularly summer monsoons, and thus, groundwater. In addition, our research using lake sediment cores in the region indicates that sediment organic content may fluctuate with paleotemperature. We sought to determine whether fens likewise preserve evidence of relatively low magnitude temperature changes, including those associated with the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). Since fens persist in the region only under marginal conditions, they are very sensitive to fluctuations in climate and consequent hydrological responses. Nine fens were sampled in the study. Fen stratigraphy was studied at all of the sites. Humification analysis and bulk density and organic content determinations were conducted at one-centimeter intervals on cores from four of the fens. Core chronology was established using radiocarbon dating. Our results suggest that warmer summers in the early Holocene led to earlier snowmelt at lower elevations. Fens located near the lower margins of the subalpine zone (<3100 m elevation) ceased to accumulate peat during this period, changing to alluvial

  12. Geophysical prospection on an Early Iron Age Cult Site near Frankfurt/Oder, Germany

    NASA Astrophysics Data System (ADS)

    Ullrich, Burkart; Kaufmann, Georg; Beilke-Voigt, Ines

    2010-05-01

    The Free University of Berlin and the Humboldt University of Berlin hosts the excellence cluster 264 Topoi, "The Formation and Transformation of Space and Knowledge in Ancient Civilizations". The Excellence Cluster pursues the goal of researching the interdependence of space and knowledge in the civilizations of the Ancient Near East, the Mediterranean, and Black Sea region and parts of the Eurasian steppe from the 6th millennium BC to around AD 500. Within this excellence cluster, the project A-I-11 "Lossow near Frankfurt/Oder - An Early Iron Age Cult Site of the Ancient Peripheral Zone" examines the evolution of an important cult site in Central Europe. The castle mound of Lossow was built as a fortified settlement in the late Bronze Age (10th century B.C.). After a phase of around 200 years, a supra-regionally significant, early Iron Age cult centre developed on this site (8th-6th century B.C.). Several pieces of evidence indicate that the locality had a central-site character. Typical for the site are well-shapes shafts, filled with large amounts of human and animal bones. The shafts with a diameter of about 1 meter and a depth of about 5 to 7 meters are a great challenge to near surface geophysics. Here, geophysical methods (geomagnetic gradiometry, geoelectric imaging, georadar survey) have been used to obtain a large-scale conclusive picture of the sub-surface both within the castle mount and around the perimeter. While the magnetic results reveal numerous archaeological artefacts, geoelectric imaging decipers the subsurface structure of the site.

  13. Reconstructing Past Vegetation Types During the Late Holocene Using Stable Carbon Isotopes of Leporids from Archaeological Sites in the American Southwest

    NASA Astrophysics Data System (ADS)

    Mauldin, R. P.; Munoz, C.; Kemp, L.; Hard, R.

    2012-12-01

    Stable carbon isotopes (δ13C) from bone collagen in leporids provide high-resolution vegetation reconstruction. Leporids [e.g., cottontails (Sylvilagus sp.), jackrabbits (Lepus sp.)] die young (ca. 2 years) and use small home ranges (< 1 km2). They consume a variety of vegetation, including plants that use both C3 and C4/CAM photosynthetic pathways. Leporids appear to focus on new growth as it becomes available throughout the year, perhaps as a function of water content. Their diet, and their bone collagen, provides a high-resolution view of the carbon isotopic values present in their local plant community. Here we provide an example of the use of leporid bone collagen for reconstruction of past vegetation types using data from several archaeological sites as well as modern collections. All samples are from a basin and range setting within the Chihuahuan Desert in far west Texas and southern New Mexico, USA. The sites span a period back to roughly 1350 BP. Isotopic patterns in leporid collagen show clear evidence of change in vegetation from around 775 BP to the modern period, with a dramatic shift of 4.2‰ in median δ13C values over this period in jackrabbit collagen and a 7.3‰ decrease in median carbon isotopic values in cottontail rabbits. These data suggest a significant increase in C3 plants in leporid diet, and by extension a relative increase in these plant types in the local environment sampled by leporids. This shift is consistent with historic accounts of more C3 mesquite, possibly because of historic land use and ranching practices in the 1800s. However, while this shift may have been accelerated by historic land use changes, our data suggest that the vegetation shift began several hundred years earlier during the prehistoric period. The prehistoric collagen isotopic record also shows increased sample variability through time in both species, suggesting that year-to-year variability in vegetation may have increased late in that sequence. Our results

  14. 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.

  15. 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.

  16. North Atlantic forcing of moisture delivery to Europe throughout the Holocene.

    PubMed

    Smith, Andrew C; Wynn, Peter M; Barker, Philip A; Leng, Melanie J; Noble, Stephen R; Tych, Wlodek

    2016-01-01

    Century-to-millennial scale fluctuations in precipitation and temperature are an established feature of European Holocene climates. Changes in moisture delivery are driven by complex interactions between ocean moisture sources and atmospheric circulation modes, making it difficult to resolve the drivers behind millennial scale variability in European precipitation. Here, we present two overlapping decadal resolution speleothem oxygen isotope (δ(18)O) records from a cave on the Atlantic coastline of northern Iberia, covering the period 12.1-0 ka. Speleothem δ(18)O reveals nine quasi-cyclical events of relatively wet-to-dry climatic conditions during the Holocene. Dynamic Harmonic Regression modelling indicates that changes in precipitation occurred with a ~1500 year frequency during the late Holocene and at a shorter length during the early Holocene. The timing of these cycles coincides with changes in North Atlantic Ocean conditions, indicating a connectivity between ocean conditions and Holocene moisture delivery. Early Holocene climate is potentially dominated by freshwater outburst events, whilst ~1500 year cycles in the late Holocene are more likely driven by changes internal to the ocean system. This is the first continental record of its type that clearly demonstrates millennial scale connectivity between the pulse of the ocean and precipitation over Europe through the entirety of the Holocene. PMID:27109216

  17. 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

  18. Early prediction of eruption site using lightning location data: Estimates of accuracy during past eruptions

    NASA Astrophysics Data System (ADS)

    Nína Petersen, Guðrún; Arason, Þórður; Bjornsson, Halldór

    2013-04-01

    Eruption of subglacial volcanoes may lead to catastrophic floods and therefore early determination of the exact eruption site may be critical to civil protection evacuation plans. Poor visibility due to weather or darkness often inhibit positive identification of exact eruption location for many hours. However, because of the proximity and abundance of water in powerful subglacial volcanic eruptions, they are probably always accompanied by early lightning activity in the volcanic column. Lightning location systems, designed for weather thunderstorm monitoring, based on remote detection of electromagnetic waves from lightning, can provide valuable real-time information on location of eruption site. Important aspect of such remote detection is its independence of weather, apart from thunderstorms close to the volcano. Individual lightning strikes can be 5-10 km in length and are sometimes tilted and to the side of the volcanic column. This adds to the lightning location uncertainty, which is often a few km. Furthermore, the volcanic column may be swayed by the local wind to one side. Therefore, location of a single lightning can be misleading but by calculating average location of many lightning strikes and applying wind correction a more accurate eruption site location can be obtained. In an effort to assess the expected accuracy, the average lightning locations during the past five volcanic eruptions in Iceland (1998-2011) were compared to the exact site of the eruption vent. Simultaneous weather thunderstorms might have complicated this analysis, but there were no signs of ordinary thunderstorms in Iceland during these eruptions. To identify a suitable wind correction, the vector wind at the 500 hPa pressure level (5-6 km altitude) was compared to mean lightning locations during the eruptions. The essential elements of a system, which predicts the eruption site during the first hour(s) of an eruption, will be described.

  19. Implications for a rapid early to mid-Holocene sea-level rise from the Mekong River incised-valley system

    NASA Astrophysics Data System (ADS)

    Tjallingii, R.; Stattegger, K.; Wetzel, A.

    2009-12-01

    The abrupt transition from fluvial to marine deposition of incised-valley-infill sediments retrieved from the SE Vietnamese shelf, accurately records the postglacial transgression after 14 ka before present (BP). Incised-valley-infill sediments deposited prior to the transgression consist of fluvial mud, whereas sedimentation after the transgression is characterized by shallow-marine carbonate sands. Intertidal sedimentation at this transgressive surface is further suggested by the appearance of Glossifungites ichnofacies borrows. High resolution XRF core scanning was used to accurately locate the stratigraphical transition indicating the transgressive flooding surface in the incised-valley system and in deeper shelf sediment. Detailed XRF records reveal that infilling of the incised-valley system kept up with sea-level rise until the valley system was nearly completely filled, and after which the system stepped back. The deeper shelf records reveal that lithogenic sedimentation on the deeper shelf reduced after the accumulation of fluvial sediments in the valley system started. The sedimentological response of the Mekong river-mouth system on the transgression between 14 and 6 ka BP is completed by the comparison with land-based drill sites. This compilation of SE Asian sediment records suggest an alternative interpretation of the deglacial sea-level evolution with respect to the melt-water pulses retrieved from coral records. These records do not support a sea-level jump during melt water pulse (MWP) 1B, but strongly suggest a sea-level jump of around 14 m between 9.1 ka and 8.7 ka BP corresponding with MWP 1C. This latter sea-level jump contributed to the vast inland shore line transgression from the present-day Vietnamese coastline to the Cambodian lowlands.

  20. A P-wave based, on-site method for Earthquake Early Warning

    NASA Astrophysics Data System (ADS)

    Zollo, Aldo

    2016-04-01

    Can we rapidly predict the potential damage of earthquakes by-passing the estimation of its location and magnitude? One possible approach is to predict the expected peak ground shaking at the site and the earthquake magnitude from the initial P-peak amplitude and characteristic period, respectively. The idea, first developed by Wu and Kanamori (2005), is to combine the two parameters for declaring the alert once the real-time measured quantities have passed pre-defined thresholds. Our proposed on-site early warning method generalized this approach, based on the analysis of strong motion data from modern accelerograph networks in Japan, Taiwan and Italy (Zollo et al., 2010). It is based on the real-time measurement of the period (τc) and peak displacement (Pd) parameters at one or more co-located stations at a given target site to be protected against the earthquake effects. By converting these real-time proxies in predicted values of Peak Ground Velocity (PGV) or instrumental intensity (IMM) and magnitude, an alert level is issued at the recording site based on a decisional table with four entries defined upon threshold values of the parameters Pd and Tc. The latter ones are set according to the error bounds estimated on the derived prediction equations. A near-source network of stations running the onsite method can provide the event location and transmit the information about the alert levels recorded at near-source stations to more distant sites, before the arrival of the most destructive phase. The network-based approach allows for the rapid and robust estimation of the Potential Damage Zone (PDZ), that is the area where most of earthquake damage is expected (Colombelli et al., 2012). A new strategy for a P-wave based, on-site earthquake early warning system has been developed and tested on Japanese strong motion data and under testing on Italian data. The key elements are the real-time, continuous measurement of three peak amplitude parameters and their

  1. Holocene evolution of summer winds and marine productivity in the tropical Indian Ocean in response to insolation forcing: data-model comparison

    NASA Astrophysics Data System (ADS)

    Bassinot, F. C.; Marzin, C.; Braconnot, P.; Marti, O.; Mathien-Blard, E.; Lombard, F.; Bopp, L.

    2011-07-01

    The relative abundance of Globigerinoides bulloides was used to infer Holocene paleo-productivity changes on the Oman margin and at the southern tip of India. Today, the primary productivity at both sites reaches its maximum during the summer season, when monsoon winds result in local Eckman pumping, which brings more nutrients to the surface. On a millennium time-scale, however, the % G. bulloides records indicate an opposite evolution of paleo-productivity at these sites through the Holocene. The Oman Margin productivity was maximal at ~9 ka (boreal summer insolation maximum) and has decreased since then, suggesting a direct response to insolation forcing. On the contrary, the productivity at the southern tip of India was minimum at ~9 ka, and strengthened towards the present. Paleo-reconstructions of wind patterns, marine productivity and foraminifera assemblages were obtained using the IPSL-CM4 climate model coupled to the PISCES marine biogeochemical model and the FORAMCLIM ecophysiological model. These reconstructions are fully coherent with the marine core data. They confirm that the evolution of particulate export production and foraminifera assemblages at our two sites were directly linked with the strength of the upwelling. Model simulations at 9 ka and 6 ka BP show that the relative evolution between the two sites since the early Holocene can be explained by the weakening but also the southward shift of monsoon winds over the Arabian Sea during boreal summer.

  2. 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.

  3. Palaeotectonic implications of increased late Eocene-early Oligocene volcanism from South Pacific DSDP sites

    USGS Publications Warehouse

    Kennett, J.P.; Von Der Borch, C.; Baker, P.A.; Barton, C.E.; Boersma, A.; Cauler, J.P.; Dudley, W.C.; Gardner, J.V.; Jenkins, D.G.; Lohman, W.H.; Martini, E.; Merrill, R.B.; Morin, R.; Nelson, Campbell S.; Robert, C.; Srinivasan, M.S.; Stein, R.; Takeuchi, A.; Murphy, M.G.

    1985-01-01

    Late Eocene-early Oligocene (42-35 Myr) sediments cored at two DSDP sites in the south-west Pacific contain evidence of a pronounced increase in local volcanic activity, particularly in close association with the Eocene-Oligocene boundary. This pulse of volcanism is coeval with that in New Zealand and resulted from the development of an Indo- Australian / Pacific Plate boundary through the region during the late Eocene. The late Eocene / earliest Oligocene was marked by widespread volcanism and tectonism throughout the Pacific and elsewhere, and by one of the most important episodes of Cenozoic climatic cooling. ?? 1985 Nature Publishing Group.

  4. Brief communication: Gladysvale: first early hominid site discovered in South Africa since 1948.

    PubMed

    Berger, L R; Keyser, A W; Tobias, P V

    1993-09-01

    We report here the discovery of fossil hominid teeth at Gladysvale, near Johannesburg in the southern Transvaal. This find makes the site the seventh in South Africa to yield australopithecine remains and the first new early hominid-bearing locality to be found in this region since 1948. Apart from the hominid specimens, our excavations at Gladysvale have added appreciably to the abundant Plio-Pleistocene fauna previously recorded from the cave deposit. The fauna indicates that savanna conditions prevailed during deposition of at least part of the fill. Preliminary faunal dating gives an age of deposition of between c1.7 and c2.5 mya. PMID:8238287

  5. Towards a Circum-Antarctic Holocene Paleointensity Record

    NASA Astrophysics Data System (ADS)

    Brachfeld, S.; Kissel, C.; Laj, C.; Willmott, V.

    2005-12-01

    New Holocene geomagnetic paleointensity records have been constructed from the Western Antarctic Peninsula (WAP), Eastern Antarctic Peninsula (EAP), and from the East Antarctic Margin (EAM). The goal of this work is to develop Antarctic paleointensity reference curves for correlation and dating of Antarctic continental shelf sediments. Sediment sequences deposited in fjords and inner shelf basins contain Holocene sections of 3-meters to more than 20-meters, recording the last deglaciation, the paleohistory of ice shelves, and shifting paleoceanographic conditions. However, these records suffer from a lack biogenic calcite for radiocarbon dating. Diatomaceous mud contains sufficient acid insoluble organic matter (aiom) for radiocarbon dating and hence an independent chronology. However, laminated oozes yield shallow inclinations, hence the remanence vector is suspect. Bioturbated diatomaceous mud and diatom-poor muds yield excellent directional records and satisfy the criteria for magnetic uniformity, however the organic content is low and aiom dates can be problematic. Our paleointensity records show the broad pattern of higher intensity during the late Holocene, and lower intensity during the early to middle Holocene, similar to the sinusoidal intensity pattern seen in global absolute and relative paleointensity stacks. Several of the records contain 3 to 4 late Holocene peaks with 1000-year wavelengths that are similar in amplitude and duration to features seen in northern hemisphere lacustrine and marine records. Here we evaluate the local versus regional character of the Antarctic paleointensity records, and the consistency of aiom-dated versus paleointensity-tuned chronologies.

  6. Vegetation changes and timberline fluctuations in the Central Alps as indicators of holocene climatic oscillations

    SciTech Connect

    Wick, L.; Tinner, W.

    1997-11-01

    Pollen and plant-macrofossil data are presented for two lakes near the timberline in the Italian (Lago Basso, 2250 m) and Swiss Central Alps (Gouille Rion, 2343 m). The reforestation at both sites started at 9700-9500 BP with Pinus cembra, Larix decidua, and Betula. The timberline reached its highest elevation between 8700 and 5000 BP and retreated after 5000 BP, due to a mid-Holocene climatic change and increasing human impact since about 3500 BP (Bronze Age). The expansion of Picea abies at Lago Basso between ca. 7500 and 6200 BP was probably favored by cold phases accompanied by increased oceanicity, whereas in the area of Gouille Rion, where spruce expanded rather late (between 4500 and 3500 BP), human influence equality might have been important. The mass expansion of Alnus viridis between ca. 5000 and 3500 BP probably can be related to both climatic change and human activity at timberline. During the early and middle Holocene a series of timberline fluctuations is recorded as declines in pollen and macrofossil concentrations of the major tree species, and as increases in nonarboreal pollen in the pollen percentage diagram of Gouille Rion. Most of the periods of low timberline can be correlated by radiocarbon dating the climatic changes in the Alps as indicated by glacier advances in combination with palynological records, solifluction, and dendroclimatical data. Lago Basso and Gouille Rion are the only sites in the Alps showing complete palaeobotanical records of cold phases between 10,000 and 2000 BP with very good time control. The altitudinal range of the Holocene treeline fluctuations caused by climate most likely was not more than 100 to 150 m. A possible correlation of a cold period at ca. 7500-6500 BP (Misox oscillation) in the Alps is made with paleoecological data from North American and Scandinavia and a climate signal in the GRIP ice core from central Greenland 8200 yr ago (ca. 7400 yr uncal. BP).

  7. Holocene variations in peatland methane cycling associated with the Asian summer monsoon system

    PubMed Central

    Zheng, Yanhong; Singarayer, Joy S.; Cheng, Peng; Yu, Xuefeng; Liu, Zhao; Valdes, Paul J.; Pancost, Richard D.

    2014-01-01

    Atmospheric methane concentrations decreased during the early to middle Holocene; however, the governing mechanisms remain controversial. Although it has been suggested that the mid-Holocene minimum methane emissions are associated with hydrological change, direct evidence is lacking. Here we report a new independent approach, linking hydrological change in peat sediments from the Tibetan Plateau to changes in archaeal diether concentrations and diploptene δ13C values as tracers for methanogenesis and methanotrophy, respectively. A minimum in inferred methanogenesis occurred during the mid-Holocene, which, locally, corresponds with the driest conditions of the Holocene, reflecting a minimum in Asian monsoon precipitation. The close coupling between precipitation and methanogenesis is validated by climate simulations, which also suggest a regionally widespread impact. Importantly, the minimum in methanogenesis is associated with a maximum in methanotrophy. Therefore, methane emissions in the Tibetan Plateau region were apparently lower during the mid-Holocene and partially controlled by interactions of large-scale atmospheric circulation. PMID:25135106

  8. Late Holocene Sea-levels, Climate and Ice Sheet Dynamics in West Greenland

    NASA Astrophysics Data System (ADS)

    Long, A. J.; Woodroffe, S. A.; Bryant, C.

    2007-12-01

    At the end of the Holocene altithermal, c. 5 ka cal. yr BP, the Greenland Ice Sheet (GIS) had retreated 10-30 km inland of its present position. During the subsequent neoglacial, from c. 4 ka cal yr BP onwards, the GIS re-grew, advancing to reach a maximum extent during the "Little Ice Age". This re-growth saw an increase in load on the earth's surface that, throughout West Greenland, was accompanied by a switch from early and mid Holocene relative sea-level (RSL) fall to late Holocene RSL rise. Evidence for this rise includes drowned archaeological sites, submerged freshwater peats and flooded lake basins. Recently collected sediment cores from flooded lake basins in Disko Bugt and Kangerlussuaq (and from elsewhere in West Greenland) define millennial scale trends in mid and late Holocene RSL that reflect increased ice load during the neoglacial. They provide powerful constraints on geophysical models of Holocene ice sheet history. However, such records lack the resolution required to explore the short-term dynamic interactions between the ice sheet and RSL during the last millennia. In this paper we present a high resolution RSL record from Kangerlussuaq from this period. Our approach uses thin, radiocarbon-dated salt marsh deposits that overlie bedrock. We reconstruct RSL change between c. AD 1400 and the present using seventeen radiocarbon dates on terrestrial plant macrofossils, together with an extensive database of fossil and modern diatom assemblages. Our data indicate a long-term rate of RSL rise over this period of c. 1.3 mm yr-1, close to that suggested by recent GPS observations (when corrected for a twentieth century "eustatic" sea-level rise of c. 1.5-2 mm yr-1). We also identify higher frequency variability in our record that may reflect changes in ice load associated with the "Little Ice Age" in West Greenland. High resolution RSL records, such as this, provide a new target for geophysical models of ice sheet mass balance change and a long term

  9. Oldest playable musical instruments found at Jiahu early Neolithic site in China.

    PubMed

    Zhang, J; Harbottle, G; Wang, C; Kong, Z

    1999-09-23

    Excavations at the early Neolithic site of Jiahu in Henan Province, China have produced what may be the earliest complete, playable, tightly-dated multinote musical instruments. Jiahu was occupied from 7000 BC to 5700 BC, considerably antedating the well known Peiligang culture. Here we describe six exquisitely made complete flutes which were found in radiocarbon-dated excavation layers, along with fragments of perhaps 30 more. The flutes are made from the ulnae of the red-crowned crane (Grus japonensis Millen) and have 5, 6, 7 and 8 holes. The best preserved flute has been played and tonally analysed. In addition to early musical artefacts, the archaeological record at Jiahu contains important information on the very foundations of Chinese society. We describe the archaeological characteristics of the Jiahu site, details concerning its dating, its place in the prehistory of the Chinese Neolithic, the ethnicity of its population and the results of a tonal analysis of a nearly 9,000-year-old musical instrument found there.

  10. An Early Pleistocene high-resolution paleoclimate reconstruction from the West Turkana (Kenya) HSPDP drill site

    NASA Astrophysics Data System (ADS)

    Stockhecke, Mona; Beck, Catherine; Brown, Erik T.; Cohen, Andrew; Deocampo, Daniel M.; Feibel, Craig S.; Pelletier, Jon D.; Rabideaux, Nathane M.; Sier, Mark

    2016-04-01

    The Hominin Sites and Paleolakes Drilling Project (HSPDP), and the related Olorgesailie Drilling Project (ODP), recovered ~2 km of drill core since 2012. At the HSPDP West Turkana Kaitio (WTK) site a 216 m-long core that covers the Early Pleistocene time window (1.3 to 1.87 Ma) during which hominids first expanded out of Africa and marine records document reorganization of tropical climate and the development of the strong Walker circulation. WTK carries particular interest for paleoclimate and paleoenvironmental reconstructions as it is located only 2.5 km from the location of one of the most complete hominin skeletons ever recovered (Nariokotome Boy). XRF core scanning data provide a means of evaluating records of past environmental conditions continuously and at high resolution. However, the record contains complex lithologies reflecting repeated episodes of inundation and desiccation along a dynamic lake margin. Here we present a methodological approach to address the highly variable lithostratigraphy of the East African records to establish comprehensive paleoclimate timeseries. The power spectrum of the presented hydroclimate record peaks at Milankovitch cycles, qualifying HSPDP drill cores from the Turkana Basin to be used as high-resolution Early Pleistocene paleoclimate archive. Comparing these data with marine climate reconstructions sheds light into athmospheric processes and continental climate dynamics.

  11. Report on Lessons Learned from the NP 2010 Early Site Permit Program FINAL REPORT

    SciTech Connect

    2008-03-26

    This report provides a summary of lessons learned from the demonstration of the licensing process for three Early Site Permit (ESP) applications supported as part of the Department of Energy’s (DOE) Nuclear Power 2010 (NP 2010) program. The ESP process was established by the Nuclear Regulatory Commission (NRC) to enable completion of the site evaluation component of nuclear power plant licensing under 10 CFR Part 52 before a utility makes a decision to build a plant. Early Site Permits are valid for 10 to 20 years and can be renewed for an additional 10 to 20 years. NRC review of an ESP application addresses site safety issues, environmental protection issues, and plans for coping with emergencies. Successful completion of the ESP process will establish that a site is suitable for possible future construction and operation of a nuclear power plant. Most importantly, an ESP resolves significant site-related safety and environmental issues early in the decision process and helps achieve acceptance by the public. DOE competitively selected Dominion Nuclear Energy North Anna, LLC (Dominion); System Energy Resources, Inc. (an Entergy subsidiary); and Exelon Generation Company, LLC (Exelon) in 2002 to demonstrate the ESP process and provided cost-shared support through the NP 2010 program. Dominion pursued an ESP for the North Anna site in Virginia; System Energy Resources, Inc. pursued an ESP for the Grand Gulf site in Mississippi; and Exelon pursued an ESP for the Clinton site in Illinois. After successfully demonstrating the process, the NRC issued an ESP for Clinton on March 17, 2007; Grand Gulf on April 5, 2007; and North Anna on November 27, 2007. As with all successful projects, there are lessons to be learned from the NP 2010 early site permitting demonstration that can help improve future implementation guidance documents and regulatory review standards. In general, these lessons pertain to the effectiveness of the regulatory process, experience related to

  12. Transcriptionally active immediate-early protein of pseudorabies virus binds to specific sites on class II gene promoters.

    PubMed Central

    Cromlish, W A; Abmayr, S M; Workman, J L; Horikoshi, M; Roeder, R G

    1989-01-01

    In the presence of partially purified pseudorabies virus immediate-early protein, multiple sites of DNase I protection were observed on the adenovirus major late and human hsp 70 promoters. Southwestern (DNA-protein blot) analysis demonstrated that the immediate-early protein bound directly to the sequences contained in these sites. These sequences share only limited homology, differ in their affinities for the immediate-early protein, and are located at different positions on these two promoters. In addition, the site-specific binding of a temperature-sensitive immediate-early protein was eliminated by the same heat treatment which eliminates its transcriptional activating function, whereas the binding of the wild-type protein was unaffected by heat treatment. Thus, site-specific binding requires a functionally active immediate-early protein. Furthermore, immediate-early-protein-dependent in vitro transcription from the major late promoter was preferentially inhibited by oligonucleotides which are homologous to the high-affinity binding sites on the major late or hsp 70 promoters. These observations suggest that transcriptional stimulation by the immediate-early protein involves binding to cis-acting elements. Images PMID:2539489

  13. Holocene cooling culminates in sea ice oscillations in Fram Strait

    NASA Astrophysics Data System (ADS)

    Müller, Juliane; Werner, Kirstin; Stein, Ruediger; Fahl, Kirsten; Moros, Matthias; Jansen, Eystein

    2012-07-01

    A reconstruction of Holocene sea ice conditions in the Fram Strait provides insight into the palaeoenvironmental and palaeoceanographic development of this climate sensitive area during the past 8500 years BP. Organic geochemical analyses of sediment cores from eastern and western Fram Strait enable the identification of variations in the ice coverage that can be linked to changes in the oceanic (and atmospheric) circulation system. By means of the sea ice proxy IP25, phytoplankton-derived biomarkers and ice rafted detritus (IRD) increasing sea ice occurrences are traced along the western continental margin of Spitsbergen throughout the Holocene, which supports previous palaeoenvironmental reconstructions that document a general cooling. A further significant ice advance during the Neoglacial is accompanied by distinct sea ice fluctuations, which point to short-term perturbations in either the Atlantic Water advection or Arctic Water outflow at this site. At the continental shelf of East Greenland, the general Holocene cooling, however, seems to be less pronounced and sea ice conditions remained rather stable. Here, a major Neoglacial increase in sea ice coverage did not occur before 1000 years BP. Phytoplankton-IP25 indices ("PIP25-Index") are used for more explicit sea ice estimates and display a Mid Holocene shift from a minor sea ice coverage to stable ice margin conditions in eastern Fram Strait, while the inner East Greenland shelf experienced less severe to marginal sea ice occurrences throughout the entire Holocene.

  14. 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.

  15. Early Site Permit Demonstration Program, plant parameters envelopes: Comparison with ranges of values for four hypothetical sites. Volume 2

    SciTech Connect

    Not Available

    1992-09-01

    The purpose of this volume is to report the results of the comparison of the ALWR plan parameters envelope with values of site characteristics developed for our hypothetical sites that generally represent conditions encountered within the United States. This effort is not intended to identify or address the suitability of any existing site, site area, or region in the United States. Also included in this volume is Appendix F, SERCH Summaries Regarding Siting.

  16. Holocene fire history in Western China - relationships with climate and human impact, and the role of fire in vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Cui, Q.

    2015-12-01

    It is well recognised that studies of past fire regimes and their causes (human and/or climatic) are useful to understand the long-term ecological effects of fire on vegetation communities. Further, information on the long-term fire history and its effect on vegetation dynamics may provide useful insights for vegetation management in fragile eco-environment of Western China. The main aim of this study is to quantitatively reconstruct high-resolution fire history in West China based on charcoal records from peatlands in Zoige basin (Tibet) and Altai Mountains (Xinjiang). We investigate the long-term relationships between fire, climate, human-impact and the history of biodiversity based on four Holocene macro- and micro- charcoal records and a synthesis on previously published pollen data and geochemistry data. Three hypotheses based on global charcoal records and former studies on palaeofire carried out in China need to be test by this study: 1) during early-mid Holocene period, fire frequency in the study area is relative low and best explained by the changes of regional climate; 2) during the late Holocene, fire activities in the study area increased might due to impacts of the human activities over the climate changes, and human activities is responsible for the temporal and spatial variations in fire regime; 3) the difference of fire histories can be explained by the difference of vegetation composition at site.

  17. Rectilinear evolution in arvicoline rodents and numerical dating of Iberian Early Pleistocene sites

    NASA Astrophysics Data System (ADS)

    Palmqvist, Paul; González-Donoso, José María; De Renzi, Miquel

    2014-08-01

    Lozano-Fernández et al. (2013a) have recently published a method intended for numerical dating of Early Pleistocene sites, which is based on the assumption of uniform, constant rate increase through time of mean lower molar tooth length of water voles (Mimomys savini) in a number of levels sampled in the stratigraphic sequence of Atapuerca TD site. They suggest that the regression equation obtained in this local section for site chronology on tooth size could be useful for estimating the numerical age of other localities from southwestern Europe. However, in our opinion this biostratigraphic approach has severe conceptual and methodological problems, which discourage its use as a chronometric tool. These problems include that: (1) the logic behind their approach represents a ‘fallacy of hasty generalization', because the results obtained for a local section are generalized to all possible stratigraphic sequences; (2) the study is based on tooth measurements from a limited set of samples taken in a single locality, which are represented by small numbers of specimens, cover a short time span and have a high level of age uncertainty; (3) the samples analyzed show small, statistically non-significant differences between their mean tooth length values; (4) the approach assumes a linear-straight, orthoevolutionary model of change at constant, monotonic rate for the apparent trend to increasing tooth size in the M. savini lineage; (5) these changes are better described in the Atapuerca TD section by a random walk, or even by a series of independent events, than by a model of rectilinear change; and (6) the application of this methodology to other localities such as the Orce sites, which preserve the oldest evidence of human presence in Europe, would mean that an equation adjusted within a restricted chronological range (1.01-0.8 Ma) is used for extrapolating the ages of sites that are clearly older (˜1.4 Ma).

  18. Takarkori rock shelter (SW Libya): an archive of Holocene climate and environmental changes in the central Sahara

    NASA Astrophysics Data System (ADS)

    Cremaschi, Mauro; Zerboni, Andrea; Mercuri, Anna Maria; Olmi, Linda; Biagetti, Stefano; di Lernia, Savino

    2014-10-01

    Rock shelters in the central Saharan massifs preserve anthropogenic stratigraphic sequences that represent both a precious archive for the prehistory of the region and a powerful proxy data for Holocene palaeoenvironments. The geoarchaeological (micromorphology) and archaeobotanical (pollen analysis) approaches were integrated to investigate the anthropogenic sedimentary sequence preserved within the Takarkori rock shelter, a Holocene archaeological site located in the Libyan central Sahara (southern Tadrart Acacus massif). The site was occupied throughout the Early and Middle Holocene (African Humid Period) by groups of hunter-gatherers before and by pastoral communities later. The investigation on the inner part of the sequence allows to recognize the anthropogenic contribution to sedimentation process, and to reconstruct the major changes in the Holocene climate. At the bottom of the stratigraphic sequence, evidence for the earliest frequentation of the site by hunters and gatherers has been recognized; it is dated to c. 10,170 cal yr BP and is characterized by high availability of water, freshwater habitats and sparsely wooded savannah vegetation. A second Early Holocene occupation ended at c. 8180 cal yr BP; this phase is marked by increased aridity: sediments progressively richer in organics, testifying to a more intense occupation of the site, and pollen spectra indicating a decrease of grassland and the spreading of cattails, which followed a general lowering of lake level or widening of shallow-water marginal habitats near the site. After this period, a new occupational phase is dated between c. 8180 and 5610 cal yr BP; this period saw the beginning of the frequentation of pastoral groups and is marked by an important change in the forming processes of the sequence. Sediments and pollen spectra confirm a new increase in water availability, which led to a change in the landscape surrounding the Takarkori rock shelter with the spreading of water bodies. The

  19. Early Regulatory Engagement for Successful Site Remediation: the UK Experience - 13173

    SciTech Connect

    Maitland, R.P.; Senior, D.

    2013-07-01

    The Office for Nuclear Regulation (ONR) is an independent safety, security and transport regulator of the UK nuclear industry. ONR regulates all civil nuclear reactor power stations, fuel manufacture, enrichment, spent fuel reprocessing, most defence sites and installations that store and process legacy spent fuel and radioactive waste. The responsibility for funding and strategic direction of decommissioning and radioactive waste management of state owned legacy sites has rested solely with the Nuclear Decommissioning Authority (NDA) since 2005. A key component of NDA's mandate was to encourage new strategic approaches and innovation to dealing with the UK's waste legacy and which deliver value-for-money to the UK taxpayer. ONR, as an agency of the Health and Safety Executive, is entirely independent of NDA and regulates all prescribed activities on NDA's sites. NDA's competition of site management and closure contracts has attracted significant international interest and the formation of consortia comprised of major British, US, French and Swedish organizations bidding for those contracts. The prominence of US organizations in each of those consortia reflects the scale and breadth of existing waste management and D and D projects in the US. This paper will articulate, in broad terms, the challenges faced by international organizations seeking to employ 'off-the-shelf' technology and D and D techniques, successfully employed elsewhere, into the UK regulatory context. The predominantly 'goal-setting' regulatory framework in the UK does not generally prescribe a minimum standard to which a licensee must adhere. The legal onus on licensees in the UK is to demonstrate, whatever technology is selected, that in its applications, risks are reduced 'So Far As Is Reasonably Practicable' or 'SFAIRP'. By the nature of its role, ONR adopts a conservative approach to regulation; however ONR also recognises that in the decommissioning (and ultimately the site closure) domain

  20. Early Site Permit Demonstration Program: Regulatory criteria evaluation report. Appendix E

    SciTech Connect

    Not Available

    1993-03-01

    The primary objective of the Early Site Permit Demonstration Program (ESPDP) is to demonstrate successfully the use of 10CFR52 to obtain ESPs for one or more US sites for one (or more) ALWR nuclear power plants. It is anticipated that preparation of the ESP application and interaction with NRC during the application review process will result not only in an ESP for the applicant(s) but also in the development of criteria and definition of processes, setting the precedent that facilitates ESPs for subsequent ESP applications. Because siting regulatory processes and acceptance criteria are contained in over 100 separate documents, comprehensive licensing and technical reviews were performed to establish whether the requirements and documentation are self-consistent, whether the acceptance criteria are sufficiently well-defined and clear, and whether the licensing process leading to the issuance of an ESP is unambiguously specified. This document provides Appendix E which contains a population density report. In this study the proposed US Nuclear Regulatory Commission (NRC) population density and exclusion zone size criteria were evaluated for their potential effectiveness to meet the quantitative public health and safety objectives associated with the NRC Safety Goal Policy. In addition, the individual and societal risks from postulated accidents (based on NUREG-1150 methods) were determined and compared to the quantitative prompt and latent health objective of the safety goal policy.

  1. Reappraisal of early CT signs to predict the arterial occlusion site in acute embolic stroke

    PubMed Central

    Koga, M; Saku, Y; Toyoda, K; Takaba, H; Ibayashi, S; Iida, M

    2003-01-01

    Patients: 105 consecutive patients with acute embolic stroke affecting the anterior circulation. Methods: Four early signs were evaluated on cranial CT within six hours of stroke onset: loss of the insular ribbon (LIR); attenuation of the lentiform nucleus (ALN); hemispherical sulcus effacement (HSE); and the hyperdense middle cerebral artery sign (HMCAS). The arterial occlusion site was definitively identified on cerebral angiography within two hours of the CT examination. Results: LIR was present in 55% of patients with internal carotid artery occlusion. ALN was present in 65% of patients with occlusion of the sphenoidal portion (M1) of the middle cerebral artery. HSE was present in 47% of patients with middle cerebral artery branch occlusion. LIR was related independently to internal carotid artery occlusion (odds ratio (OR) 2.8 (95% confidence interval, 1.2 to 6.8)), ALN to M1 occlusion (OR 2.9 (1.2 to 7.4)), and isolated HSE without ALN or LIR to branch occlusion (OR 12.8 (3.2 to 51.5)). The combined presence of the three signs was indicative of internal carotid artery occlusion (p < 0.05), and the presence of ALN and LIR without HSE was indicative of M1 occlusion (p < 0.05) by univariate analysis. HMCAS bore no relation to either arterial occlusion site. Conclusions: LIR, ALS, HSE, and combinations of these were useful predictors of the arterial occlusion site. PMID:12700311

  2. Anthropogenic and geomorphic controls on peatland dynamics in contrasting floodplain environments during the Holocene and its impact on carbon storage

    NASA Astrophysics Data System (ADS)

    Verstraeten, Gert; Broothaerts, Nils; Notebaert, Bastiaan

    2016-04-01

    Peatlands are an important store of carbon in terrestrial environments, and scientific interest in peatlands has increased strongly in the light of the recent global climatic changes. Much attention has been paid to peatland dynamics in extensive arctic and boreal wetlands or to blanket peat in temperate regions. Nevertheless, long-term dynamics of peat in alluvial wetlands in temperate regions remains largely underresearched. In this study, data from three contrasting environments were used to provide more insights in the anthropogenic and geomorphic controls on peatland dynamics. The results show a high variability in alluvial peatland dynamics between the different study sites. In the central Belgian Loess Belt, alluvial peatlands developed during the early Holocene but gradually disappeared from the Mid-Holocene onwards due to the gradual intensification of agricultural activities in the catchment and consequent higher sedimentation rates in the floodplain system. The end of peat growth is shown to be diachronous at catchment scale, ranging between 6500 and 500 cal a BP. The disappearance of the alluvial peatlands has important implications since it potentially reduces the storage of locally produced C. Nevertheless, it was shown that this reduced production of local C but was outbalanced by the burial of hillslope derived C. Also within the sandy catchments of the Belgian Campine region alluvial peatlands initiated in the early Holocene but, here, they abruptly disappeared in the Mid-Holocene before the onset of intense agricultural activities in the catchment. This suggests that for the sandy regions, anthropogenic impact on peatland dynamics is less important compared to natural factors. For these regions, the disappearance of alluvial peatland formation resulted in a sharp decline in alluvial carbon storage as there is no compensation through hillslope derived C input. For the upper Dee catchment in NE Scotland, Holocene carbon floodplain storage varies

  3. Spatial Heterogeneity of Holocene Tsunami Deposits As Preserved on Koh Phra Thong Island, Thailand

    NASA Astrophysics Data System (ADS)

    Kirby, M. E.; Rhodes, B. P.; Choowong, M.; Frady, W.; Leeper, R.

    2010-12-01

    Thailand’s Koh Phra Thong Island is characterized by ridge-swale topography. Unlike the ridges, swales often hold water during the wet season, which allows for the deposition and preservation of sediment. As a result, swales are potential archives for past tsunami deposits. Seven different swale sites spanning 1.9km horizontal distance were excavated to investigate the occurrence, and distribution, of paleo-tsunami deposits across the island. Five of the seven sites were trenched across the breadth of their swale to a depth that exposed the early-mid Holocene highstand beach sands; the remaining two sites were examined by pits. These seven sites are located approximately 2km north of sites previously developed by Jankaew et al. (2008) and 1km or less north of sediment probe cores taken by Fujino et al. (2009). Our results reveal a highly heterogeneous spatial distribution of probable pre-2004 A.D. tsunami event deposits with a range from one to possibly four events. At almost every site, the event deposits are characterized by sharply bordered, sandy sediment units that taper in decreasing thickness away from the seaward side of the swale. Interestingly, there is no apparent relationship between swale size (depth or width) or distance from present beach front and the number or preservation “quality” of pre-2004 deposits. Future research will examine the timing of these events in relationship to our seven sites as well as other sites (Jankaew, Fujino) across the island.

  4. Origin and dynamics of the northern South American coastal savanna belt during the Holocene - the role of climate, sea-level, fire and humans

    NASA Astrophysics Data System (ADS)

    Alizadeh, Kamaleddin; Cohen, Marcelo; Behling, Hermann

    2015-08-01

    Presence of a coastal savanna belt expanding from British Guiana to northeastern Brazil cannot be explained by present-day climate. Using pollen and charcoal analyses on an 11.6 k old sediment core from a coastal depression in the savanna belt near the mouth of the Amazon River we investigated the paleoenvironmental history to shed light on this question. Results indicate that small areas of savanna accompanied by a forest type composed primarily by the genus Micropholis (Sapotaceae) that has no modern analog existed at the beginning of the Holocene. After 11,200 cal yr BP, savanna accompanied by few trees replaced the forest. In depressions swamp forest developed and by ca 10,000 cal yr BP replaced by Mauritia swamps. Between 8500 and 5600 cal yr BP gallery forest (composed mainly of Euphorbiaceae) and swamp forest succeeded the treeless savanna. The modern vegetation with alternating gallery forest and savanna developed after 5600 cal yr BP. We suggest that the early Holocene no-analog forest is a relict of previously more extensive forest under cooler and moister Lateglacial conditions. The early Holocene savanna expansion indicates a drier phase probably related to the shift of the Intertropical Convergence Zone (ITCZ) towards its northernmost position. The mid-Holocene forest expansion is probably a result of the combined influence of equatorwards shift of ITCZ joining the South Atlantic Convergence Zone (SACZ). The ecosystem variability during the last 5600 cal yr BP, formed perhaps under influence of intensified ENSO condition. High charcoal concentrations, especially during the early Holocene, indicate that natural and/or anthropogenic fires may have maintained the savanna. However, our results propose that climate change is the main driving factor for the formation of the coastal savanna in this region. Our results also show that the early Holocene sea level rise established mangroves near the study site until 7500 cal yr BP and promoted

  5. 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

  6. 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

  7. Radiocarbon dating of interstratified Neanderthal and early modern human occupations at the Chatelperronian type-site.

    PubMed

    Gravina, Brad; Mellars, Paul; Ramsey, Christopher Bronk

    2005-11-01

    The question of the coexistence and potential interaction between the last Neanderthal and the earliest intrusive populations of anatomically modern humans in Europe has recently emerged as a topic of lively debate in the archaeological and anthropological literature. Here we report the results of radiocarbon accelerator dating for what has been reported as an interstratified sequence of late Neanderthal and early anatomically modern occupations at the French type-site of the Chatelperronian, the Grotte des Fées de Châtelperron, in east-central France. The radiocarbon measurements seem to provide the earliest secure dates for the presence of Aurignacian technology--and from this, we infer the presence of anatomically modern human populations--in France.

  8. A Mid-Holocene Shift and Millennial-Scale Variations in North Pacific Intermediate Water Oxygenation and Upper Ocean Hydrography

    NASA Astrophysics Data System (ADS)

    Lembke-Jene, L.; Tiedemann, R.; Gong, X.; Nuernberg, D.; Max, L.; Lohmann, G.; Gorbarenko, S. A.

    2014-12-01

    The subarctic North Pacific and its marginal seas constitute a key area in which rapid environmental changes over the past decades have been observed in instrumental records, like sea ice decreases, or alterations of nutrient inventories and oxygenation of mid-depth water masses. However, knowledge about the past climatic and oceanographic variability beyond instrumental time series in the subarctic North Pacific and its marginal seas is limited. Few temporally and spatially well-resolved high-resolution and spatially well datasets exist, with spatial and temporal coverage being insufficient to gain a detailed picture of past variations. Our proxydata-based study focuses on a collection of sediment records from the Okhotsk Sea as major source area for well ventilated North Pacific Intermediate Water (NPIW) that cover the last ca. 12,000 years with high temporal and adequate spatial resolution. We decipher rapid changes in NPIW ventilation patterns on centennial to millennial time scales and show that the current ventilation of the mid-depth North Pacific has likely only been prevalent for the last 2 ka. We further provide evidence for a Mid-Holocene shift in mid-depth NPIW ventilation characteristics. Additionally, changes in North Atlantic Deep Water flow speed and patterns are reflected in our records of North Pacific mid-depth water mass dynamics, thus indicating a hemispheric-wide connection between the Atlantic and Pacific regions during the Holocene. Planktic oxygen isotope data suggest a high variability in the stratification of local surface water masses and the formation of sea ice, influencing the formation of new, well ventilated water masses near to our core sites. We compare the main Holocene baseline changes evidenced in our proxy reconstructions to Early Holocene and Pre-Industrial time slice results from the fully-coupled MPI-ESM (COSMOS) Earth System Model, with a focus on the Pacific Ocean to better understand NPIW and upper ocean dynamic changes.

  9. Posterior archaeomagnetic dating for the early Medieval site Thunau am Kamp, Austria

    NASA Astrophysics Data System (ADS)

    Schnepp, Elisabeth; Lanos, Philippe; Obenaus, Martin

    2014-05-01

    The early medieval site Thunau am Kamp consists of a hill fort and a settlement with large burial ground at the bank of river Kamp. All these features are under archaeological investigation since many years. The settlement comprises many pit houses, some with stratigraphic order. Every pit house was equipped with at least one cupola oven and/or a hearth or fireplace. Sometimes the entire cupola was preserved. The site was occupied during the 9th and 10th AD according to potshards which seem to indicate two phases: In the older phase ovens were placed in the corner of the houses while during the younger phase they are found in the middle of the wall. In order to increase the archaeomagnetic data base 14 ovens have been sampled. They fill the temporal gap in the data base for Austria around 900 AD. Laboratory treatment included alternation field and thermal demagnetisations as well as rock magnetic experiments. The baked clay with was formed from a loess sediment has preserved stable directions. Apart from one exception the mean characteristic remanent magnetization directions are concentrated around 900 AD on the early medieval part of the directional archaeomagnetic reference curve of Austria (Schnepp & Lanos, GJI, 2006). Using this curve archaeomagnetic dating with RenDate provides ages between 800 and 1100 AD which are in agreement with archaeological dating. In one case archaeomagnetic dating is even more precise. Together with the archaeological age estimates and stratigraphic information the new data have been included into the database of the Austrian curve. It has been recalculated using a new version of RenCurve. The new data confine the curve and its error band considerably in the time interval 800 to 1100 AD. The curve calibration process also provides a probability density distribution for each structure which allows for posterior dating. This refines temporal errors considerably. Usefulness of such an approach and archaeological implications will be

  10. Structured Regions of Alpha-synuclein Fibrils Include the Early Onset Parkinson's Disease Mutation Sites

    SciTech Connect

    Comellas Canal, Gemma; Lemkau, Luisel R.; Nieuwkoop, Andrew J.; Kloepper, Kathryn D.; Ladror, Daniel T.; Ebisu, Reika; Woods, Wendy S.; Lipton, Andrew S.; George, Julia M.; Rienstra, Chad M.

    2011-08-26

    Alpha-Synuclein (AS) fibrils constitute the major proteinaceous component of Lewy bodies (LBs), the pathological hallmark of Parkinson’s disease (PD) and other neurodegenerative diseases. Three single point mutations in the AS gene, as well as multiplication of the wild-type (WT) AS allele, have been previously identified in families with early-onset PD. Although AS fibrils have been the subject of intense study, critical details about their structure including the precise location of the B-strands and the extent of the core, the three-dimensional structure and the effects of the mutations—remain unknown. Here, we have used magic-angle spinning solid-state NMR spectroscopy to present a detailed characterization of the full-length WT AS fibrils. With improved sample preparations, isotopic labeling patterns and NMR experiments, we have confidently assigned more than 90% of the 13C and 15N backbone and sidechain chemical shifts of the detected residues from residue 39 to 97, and quantified the conformational dynamics throughout this region. Our results demonstrate that the core of AS fibrils extends with a repeated motif and that residues 30, 46 and 53-the early-onset PD mutant sites-are located in structured regions of AS fibrils.

  11. Drivers of Holocene peatland carbon accumulation across a climate gradient in northeastern North America

    NASA Astrophysics Data System (ADS)

    Charman, Dan J.; Amesbury, Matthew J.; Hinchliffe, William; Hughes, Paul D. M.; Mallon, Gunnar; Blake, William H.; Daley, Tim J.; Gallego-Sala, Angela V.; Mauquoy, Dmitri

    2015-08-01

    Peatlands are an important component of the Holocene global carbon (C) cycle and the rate of C sequestration and storage is driven by the balance between net primary productivity and decay. A number of studies now suggest that climate is a key driver of peatland C accumulation at large spatial scales and over long timescales, with warmer conditions associated with higher rates of C accumulation. However, other factors are also likely to play a significant role in determining local carbon accumulation rates and these may modify past, present and future peatland carbon sequestration. Here, we test the importance of climate as a driver of C accumulation, compared with hydrological change, fire, nitrogen content and vegetation type, from records of C accumulation at three sites in northeastern North America, across the N-S climate gradient of raised bog distribution. Radiocarbon age models, bulk density values and %C measurements from each site are used to construct C accumulation histories commencing between 11,200 and 8000 cal. years BP. The relationship between C accumulation and environmental variables (past water table depth, fire, peat forming vegetation and nitrogen content) is assessed with linear and multivariate regression analyses. Differences in long-term rates of carbon accumulation between sites support the contention that a warmer climate with longer growing seasons results in faster rates of long-term carbon accumulation. However, mid-late Holocene accumulation rates show divergent trends, decreasing in the north but rising in the south. We hypothesise that sites close to the moisture threshold for raised bog distribution increased their growth rate in response to a cooler climate with lower evapotranspiration in the late Holocene, but net primary productivity declined over the same period in northern areas causing a decrease in C accumulation. There was no clear relationship between C accumulation and hydrological change, vegetation, nitrogen content

  12. Holocene paleoclimates of southern Arabia from lacustrine deposits of the Dhamar highlands, Yemen

    NASA Astrophysics Data System (ADS)

    Davies, Caroline Pickens

    2006-11-01

    This paper presents new evidence from the Dhamar highlands, Yemen, of paleohydrologic response to fluctuations in Holocene climate. Stratigraphic, geochemical, and chronological analyses of highland peat and lacustrine deposits contribute to knowledge of the timing of early Holocene moisture changes on the Arabian Peninsula, providing a backdrop to understanding early cultural development in the Arabian highlands. The location of the Dhamar highlands, characterized by intermontane valleys surrounded by the highest mountains on the Arabian Peninsula and adjacent to the Indian Ocean is ideal for examining the influence of the Indian Ocean Monsoon (IOM) on the moisture history of this region. Fluctuations in the lacustrine and paleosol records of the Dhamar highlands reflect both local changes in paleohydrology and regional influences on the Holocene paleoclimatic conditions in southwest Arabia. In addition, a peat deposit with a radiocarbon age of 10,253 - 10,560 cal yr BP documents some of the earliest Holocene high moisture conditions on the Arabian Peninsula.

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

    NASA Astrophysics Data System (ADS)

    Carre, Matthieu; Sachs, Julian; Braconnot, Pascale; Purca, Sara; Schauer, Andrew; Falcon, Rommel Angeles; Julien, Michèle; Lavallée, Danièle

    2014-05-01

    Understanding how El Niño-Southern Oscillation (ENSO) is affected by natural and anthropogenic climate forcings requires studying its behavior under contrasted climate conditions. We present a reconstruction of ENSO characteristics in the eastern tropical Pacific during the Holocene based on the statistics of sea surface temperature (SST) variability derived from oxygen isotopes in fossil mollusk shells from Peru. ENSO variance was close to modern level in the early Holocene, and at its lowest level ~4-5 thousand years ago (ka). A shift in ENSO asymmetry indicates a persistent predominance of the central Pacific mode 6.7-7.5 ka. The modern ENSO regime was established ~3 ka. From climate models sensitivity experiments, we attribute the large variability of ENSO in the early Holocene to the wasting of continental ice sheets. These results demonstrate that both variance and spatial structure of ENSO are sensitive to external forcings but that insolation was not the prevailing forcing in the Holocene.

  14. Paleoclimatic Implications of Holocene Plant Remains from the Sierra Bacha, Sonora, Mexico

    NASA Astrophysics Data System (ADS)

    Van Devender, Thomas R.; Burgess, Tony L.; Piper, Jessie C.; Turner, Raymond M.

    1994-01-01

    A total of 93 plant taxa were identified from 11 packrat ( Neotoma sp.) midden samples from the Sierra Bacha on the coast of the Gulf of California near Puerto Libertad, Sonora, Mexico. Nine indurated samples have radiocarbon dates ranging from 9970 to 320 yr B.P. Sonoran desertscrub was present on rocky slopes throughout the Holocene. Early Holocene assemblages dominated by Fouquieria columnaris (boojum tree) reflect vegetation and climate more like modern Baja California with greater winter rainfall and cooler summers. Middle Holocene vegetation was essentially modern with modest indications of greater monsoonal rainfall even though cold-water upwelling locally inhibits summer precipitation. The results are similar to all previous midden reconstructions of early and middle Holocene climates in the Sonoran Desert, but contradict general atmospheric circulation model simulations.

  15. Collaborative community hazard exposure mapping: Distant Early Warning radar sites in Alaska's North Slope

    NASA Astrophysics Data System (ADS)

    Brady, M.

    2015-12-01

    A method to produce hazard exposure maps that are developed in collaboration with local coastal communities is the focus of this research. Typically efforts to map community exposure to climate threats over large areas have limited consideration of local perspectives about associated risks, constraining their utility for local management. This problem is especially acute in remote locations such as the Arctic where there are unique vulnerabilities to coastal threats that can be fully understood only through inclusion of community stakeholders. Through collaboration with community members, this study identifies important coastal assets and places and surveys local perspectives of exposure to climate threats along Alaska's vast North Slope coastline spanning multiple municipalities. To model physical exposure, the study adapts the U.S. Geological Survey's (USGS) coastal vulnerability index (CVI) to the Arctic context by incorporating the effects of open water distance determined by sea ice extent, and assigning CVI values to coastal assets and places according to direction and proximity. The study found that in addition to concerns about exposed municipal and industrial assets, North Slope communities viewed exposure of traditional activity sites as presenting a particular risk for communities. Highly exposed legacy Cold War Distant Early Warning Line sites are of particular concern with impacts ranging from financial risk to contamination of sensitive coastal marine environments. This research demonstrates a method to collaboratively map community exposure to coastal climate threats to better understand local risks and produce locally usable exposure maps.

  16. The Holocene climate variability in Southwestern Morocco and its link to the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    SHA, L.; Cheng, H.; Cai, Y.; Edwards, R.; Yin, J.; Sifeddine, A.; Cruz, F.; Bouchaou, L.; Beraaouz, E.; Apaéstegui, J. E.

    2013-12-01

    Southwestern Morocco is located at the southeast side of the Azores High and thus the local climate is sensitive to the changes in the North Atlantic Oscillation (NAO). Two stalagmite oxygen isotope (δ18O) records from Ifoulki and Win Timdouine Caves, Agadir, Morocco provide a high-resolution and absolutely dated climate history over the entire Holocene (last 11.5 ka). The broad similarity between the Ifoulki and Win Timdouine records for the past two millennia indicates that both records are not likely affected significantly by many possible local factors. The Win Timdouine record characterizes the full Holocene: a moderately wet early Holocene (~11.5 to 9 ka BP), wet mid-Holocene (~ 9 to 3 ka BP) and relatively dry late Holocene (~3 ka BP to present). Superimposed on the long-term trend of Holocene climate variations are eight climate events (wet) on millennial- centennial timescales that can be well linked to the Bond events documented primarily from fluctuations in ice-rafted debris throughout the Holocene in the North Atlantic Ocean. Furthermore, both records inferred a relatively dry Medieval Warm Period (high δ18O values),which is consistent with previous tree-ring records from Morocco. In addition, the oscillated δ18O values indicate an unstable climate in this area during the LIA period. Comparing with the NAO proxy records, dryer Medieval Warm Period and relatively wetter Little Ice Age agree with positive and negative NAO conditions, respectively. This linkage may potentially be extrapolated to entire Holocene and therefore put the NAO variability in the context of Holocene climate change and probe its connection with climate changes in adjacent regions throughout the Holocene.

  17. Inside the “African Cattle Complex”: Animal Burials in the Holocene Central Sahara

    PubMed Central

    di Lernia, Savino; Tafuri, Mary Anne; Gallinaro, Marina; Alhaique, Francesca; Balasse, Marie; Cavorsi, Lucia; Fullagar, Paul D.; Mercuri, Anna Maria; Monaco, Andrea; Perego, Alessandro; Zerboni, Andrea

    2013-01-01

    Cattle pastoralism is an important trait of African cultures. Ethnographic studies describe the central role played by domestic cattle within many societies, highlighting its social and ideological value well beyond its mere function as ‘walking larder’. Historical depth of this African legacy has been repeatedly assessed in an archaeological perspective, mostly emphasizing a continental vision. Nevertheless, in-depth site-specific studies, with a few exceptions, are lacking. Despite the long tradition of a multi-disciplinary approach to the analysis of pastoral systems in Africa, rarely do early and middle Holocene archaeological contexts feature in the same area the combination of settlement, ceremonial and rock art features so as to be multi-dimensionally explored: the Messak plateau in the Libyan central Sahara represents an outstanding exception. Known for its rich Pleistocene occupation and abundant Holocene rock art, the region, through our research, has also shown to preserve the material evidence of a complex ritual dated to the Middle Pastoral (6080–5120 BP or 5200–3800 BC). This was centred on the frequent deposition in stone monuments of disarticulated animal remains, mostly cattle. Animal burials are known also from other African contexts, but regional extent of the phenomenon, state of preservation of monuments, and associated rock art make the Messak case unique. GIS analysis, excavation data, radiocarbon dating, zooarchaeological and isotopic (Sr, C, O) analyses of animal remains, and botanical information are used to explore this highly formalized ritual and the lifeways of a pastoral community in the Holocene Sahara. PMID:23437260

  18. Holocene Deglaciation of the Scandinavian Ice Sheet: Preliminary 10Be Ages

    NASA Astrophysics Data System (ADS)

    Cuzzone, J. K.; Clark, P. U.; Marcott, S. A.; Pekka Lunka, J.; Wohlfarth, B.; Carlson, A. E.

    2012-12-01

    The response of ice sheets to a warming climate is not well understood. Because we are limited in our understanding of present dynamics, reconstructing the deglaciation of former ice sheets allows for a better understanding of how past ice sheets responded to a warming climate along with their contribution to sea-level rise. These reconstructions also serve as critical constraints for ice sheet modeling efforts. Here, we present a suite of new 10Be ages from erratic boulders along three transects spanning southern to northern Sweden and Finland, that improve our understanding of the deglaciation of the Scandinavian Ice Sheet (SIS) beginning ~ 11.7ka through its final demise during the early Holocene. Preliminary dates from southern Finland, beginning at the Salpausselka Youngers Dryas moraine (11.5 ± 0.7 ka, n=2), inland southern Finland near Jyvaskyla (11.5 ± 0.5ka, n=2), and coastal Finland (~60km from Gulf of Bothnia) near Vimpeli (11.5 ± 0.4ka, n=1) indicate a rapid retreat following the Younger Dryas for Southern Finland (~500km within uncertainty of ages). Preliminary dates also exist for Northern Finland, near Inari (10.3 ± 0.5ka, n=2). Additional ages now being processed at PRIME Lab, Purdue University, which will establish a basis for SIS retreat from all sampled sites, will also be presented. These new data will help to constrain the Holocene deglaciation of the SIS and its associated retreat rates, and establish the SIS contribution to Holocene sea level rise, which will improve our understanding of ice-sheet response to a warming climate.

  19. The Temporal Scale of Holocene Climatic Variability: From the Galapagos to Amazonia

    NASA Astrophysics Data System (ADS)

    Bush, M. B.; Restrepo, A.; Correa, A.; Ford, R.; Valencia, B.; Gosling, W.; Silman, M.; Conroy, J.; Overpeck, J. T.

    2006-12-01

    High-resolution lake cores from the Andes and Amazonian lowlands of W. South America and the Galapagos Islands provide new insights into the Holocene climate history of this region and its interactions with Pacific climate drivers. Our data reveal that a major drought event reported broadly from the Andes and Amazonia in the early to mid-Holocene is actually a complex series of droughts with wet interludes. These results suggest strong climatic instability prior to c. 5600 cal. yr BP. Establishment of wetter conditions at our Andean study site at c. 5600 cal. yr BP correspond to the start of Quinoa cultivation. A similar pattern of higher lake levels coinciding with the local spread of agriculture is also evident in the lowlands. Within an overall pattern of progressively wetter conditions over the last 4000 years there are periods of pronounced climatic instability (drought and flood). Fossil pollen, charcoal, sediment color, and carbon content identify periods of peak erosion between c. 900 and 1100 cal. yr BP. On the Galapagos Islands, a subdecadally resolved analysis of fossil pollen provides a striking pattern of climatic change and human-induced alteration of the landscape. Prior to the period of transforming human activity, the fossil pollen record contains a multidecadal oscillation, with wavlet analysis evealing a quasi- periodicty of c. 60 years. Andean pollen are readily identifible in the Galapagos record and transport of mainland pollen to the islands has varied markedly within the past millennium. These multiproxy records reveal the dynamic nature of Holocene climates in the tropics and the impact those changes have had on people and landscapes.

  20. A Holocene molluscan succession from floodplain sediments of the upper Lena River (Lake Baikal region), Siberia

    NASA Astrophysics Data System (ADS)

    White, Dustin; Preece, Richard C.; Shchetnikov, Alexander A.; Parfitt, Simon A.; Dlussky, Konstantin G.

    2008-05-01

    Floodplain sediments of the upper Lena River near Basovo in south-central Siberia have yielded the most detailed Holocene molluscan succession yet reported from the entire eastern Palaearctic. Over 72,500 shells from at least 28 species of terrestrial and 23 species of freshwater mollusc have been recovered, an abundance and diversity far higher than previously reported from the region. The molluscan assemblages are dominated by land snails, especially members of the genus Vallonia, represented by five species including Vallonia tenuilabris and two poorly known species Vallonia kamtschatica and Vallonia cf. chinensis. Other noteworthy species recovered include Gastrocopta theeli, Carychium pessimum, Vertigo extima (southernmost record), Vertigo microsphaera and the first Asian records of three other taxa ( Vertigo geyeri, Vertigo genesii and Vertigo parcedentata). Illustrations are provided for the critical species, since opinions differ about the status of various taxa and the correct names that should be used. The molluscan assemblages show clear successional trends during the early to mid-Holocene, reflecting episodes of dryness/wetness on the floodplain. Drier conditions at ca 6350 14C yr BP coincide with major changes in the archaeological record seen at other sites in the region but it remains unclear whether the two are linked. A prominent charcoal-rich horizon dated to ca 2800 14C yr BP marks a burning event in the catchment, which resulted in a two-fold increase in sediment accumulation rate. Remains of small mammals occurred throughout the sequence including a tooth of Microtus cf. maximowiczii, possibly the first occurrence of Ungar vole west of Lake Baikal. The faunal analyses have been integrated with a detailed pedological study of the sedimentary profile and a chronology was obtained by means of 12 AMS radiocarbon dates. This study provides the first detailed palaeoecological information relating to Holocene molluscan assemblages from the Cis

  1. ALERTES-SC3 Early Warning System prototype for South Iberian Peninsula: on-site approach.

    NASA Astrophysics Data System (ADS)

    Pazos, Antonio; Lopez de Mesa, Mireya; Gallego Carrasco, Javier; Martín Davila, José; Rioja del Rio, Carlos; Morgado, Arturo; Vera, Angel; Ciberia, Angel; Cabieces, Roberto; Strollo, Angelo; Hanka, Winfried; Carranza, Marta

    2016-04-01

    In recent years several Earthquake Early Warning Systems (EEWS) have been developed for different parts of the world. The area between SW Cape St. Vicente and the Strait of Gibraltar is one of the most seismically active zones in the Ibero-Maghrebian region, with predominantly moderate and superficial seismicity, but also big events with associated tsunamis are well documented in the area, like the 1755 Lisbon earthquake. In the frame of the ALERT-ES (2011-2013) and ALERTES-RIM (2014-2016) Spanish projects, the ALERTES-SC3 EEWS, regional approach, prototype has been developed at the Royal Spanish Navy Observatory (ROA) and is being tested in near real time for south Iberia. This prototype, based on the SeisComP3 software package, is largely based on algorithms derived from the analysis of the first seconds of the P wave records. Calculation of several parameters are carried out, mainly the characteristic period (τc) and the displacement peak (Pd), but also the velocity peak (Pv), the maximum period (τPmáx), among others. In order to warm the areas closest to the hypocentre, places located inside the "blind zone", a on-site EEWS has also been developed by ROA and integrated in the ALERTES-SC3 prototype. From the on-site approach, a warm level is declared from one station as a function of the estimated characteristic period (τc) and the displacement Peak (Pd), although the earthquake location and therefore the lead time available remains unknown. This on-site EEWS is being tested in several Western Mediterranean net (WM) stations as ARNO (Arenosillo, Huelva,Spain) or CHAS (Chafarinas island, North Africa, Spain). Also an on-site low cost station is being developed based in low cost accelerometers. In this work the current state of the on-site EEWS developed, its integration in the ALERTES-SC3 EEWS system and the low cost seismic stations are shown.

  2. Early hominin dental remains from the Plio-Pleistocene site of Drimolen, South Africa.

    PubMed

    Moggi-Cecchi, Jacopo; Menter, Colin; Boccone, Silvia; Keyser, André

    2010-05-01

    The Plio-Pleistocene fossil hominin site of Drimolen is located approximately 5.5km north of the other well-known South African Plio-Pleistocene sites (Sterkfontein, Swartkrans, Kromdraai, Coopers). It was discovered by A.W. Keyser in 1992. Systematic excavations led to the recovery of a remarkable number of fossil vertebrate taxa, including hominins. Most of the specimens collected consist of isolated teeth or those in jaws. The aim of this paper is to provide a morphological description of the dental specimens. The taxonomic allocation of each specimen is also reported, either confirming or revising previous provisional attributions. The analysis confirms the occurrence of two hominin species, Paranthropus robustus and Homo sp. With over 80 fossil hominin specimens recovered so far, Drimolen is the second largest sample of P. robustus, after Swartkrans. At Drimolen, P. robustus is represented mostly by craniodental specimens (63) among which are 47 isolated teeth and the remainder are maxillary and mandibular fragments with teeth. The assemblage markedly increases the dental sample of P. robustus. Furthermore, the Drimolen sample includes tooth classes not present in the Swartkrans or Kromdraai samples. The new tooth classes include both deciduous upper lateral incisors (DNH 31) and canines (DNH 23). In the dental sample described here there are nine specimens probably attributable to Homo, although a specific attribution is not yet possible. These specimens expand the small sample of early Homo from South African sites. Basic dimensions (MD and BL) of the Drimolen dental remains are compared in a preliminary analysis with other hominin samples. This analysis delineates the Drimolen P. robustus dental sample as characterized by smaller teeth overall than the Swartkrans sample (and in some cases also smaller than the Kromdraai sample), as well as a greater size range. PMID:20362324

  3. Holocene fluctuations of Quelccaya Ice Cap, Peru based on lacustrine and surficial geologic archives

    NASA Astrophysics Data System (ADS)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.

    2013-12-01

    Peru's Quelccaya Ice Cap (QIC; 13.9°S, 70.8°W, ~5200-5670 m asl) is an important site for understanding tropical paleoclimate, mainly because of annually layered ice cores that provide an ~1800 year long record of tropical paleoclimatic conditions (e.g., Thompson et al., 2013). Here, we present a detailed record of QIC fluctuations using surficial deposits and lake sediments that extend back to late glacial time. We compare the late Holocene records of QIC 10Be-dated moraines and ice core data with lake sediments from a nearby glacially fed lake to establish the framework we use to interpret a Holocene long sediment record from a glacially fed lake. We also examine sediments from a nearby non-glacial lake to constrain non-glacial clastic input. We collected two ~5 m-long sediment cores, one from Laguna Challpacocha, which is currently fed by QIC meltwater, and one from the Laguna Yanacocha, which has not received QIC meltwater since ~12.3 ka. Changes in magnetic susceptibility, loss on ignition, bulk density and X-ray fluorescence chemistry combined with 14C and 210Pb chronologies provide information about sediment transported to the lakes. Retreat from the late Holocene extent defined by the 10Be-dated moraine record (~0.52 ka) is contemporaneous with a sharp transition from organic to clastic sedimentation in the Challpacocha core at ~ 0.52 ka. This implies that glacially-sourced clastic sedimentation, as tracked by loss on ignition, Ti counts and bulk density, increased during ice cap recession. Based on these same proxy data, we suggest the following Holocene history of QIC: QIC receded from the Challpacocha basin by ~10.6 ka. Increased clastic sedimentation at 8.2 - 4.1, 3.6 - 2.7 ka and from 0.55 ka - present are interpreted as times of ice cap recession. The increased clastic sedimentation at ~8.2 - 4.1 ka is consistent with surficial deposits near the present-day ice margin that indicate that at ~7.0 - 4.6 ka QIC was smaller than at present (Buffen et al

  4. An Early Cenozoic Ichthyolith Record from Demerara Rise (ODP Site 1258: Equatorial Atlantic Ocean)

    NASA Astrophysics Data System (ADS)

    Bryant, R. M.; Sibert, E. C.; Norris, R. D.

    2014-12-01

    Peak global warmth during the early Eocene is a partial analog to the future structure of marine ecosystems in a high pCO2 world. Early Eocene oceans are generally regarded as supporting warmer oceans with lower overall productivity than today owing to the low concentrations of preserved organic matter in pelagic sediments. It has also been proposed that Eocene oceans were about as productive as now, but higher respiration rates in a warmer-than-modern ocean more efficiently recycled organic matter and nutrients. We investigated Eocene export productivity and its link to taxonomic diversity using the pelagic ichthyolith record. Ichthyoliths are calcium phosphate microfossils including fish teeth and shark denticles and their fragments, and are a unique paleoceanographic proxy because they represent a fossil record for marine vertebrates, a charismatic and tangible part of the ecosystem that generally goes unrepresented in the fossil record. Analysis of the ichthyolith record in Ocean Drilling Program Site 1258 (NE South America) shows a remarkable increase in accumulation rate of ichthyoliths from the Paleocene into the Eocene, suggesting that onset of the Early Eocene Climatic Optimum in the equatorial Atlantic was favorable to fish production. Our results suggest that, if anything, the early Eocene maintained higher productivity than in the late Paleocene. These results compare favorably with a record of ichthyolith accumulation in the South Pacific (DSDP 596), which also indicates unusually high rates of fish productivity in the peak of Eocene warm climates. Low resolution data sets from the Pacific suggest an explosion of morphotypes during the warm period associated with an increase in ichthyolith mass accumulation rates. Peak global warmth, therefore, appears to be associated with both higher fish production and higher taxonomic diversity than suggested by previous reconstructions of Eocene primary production. Increasing the amount of continuous records of

  5. Late Pleistocene and Holocene depositional trends, processes, and history of Astoria deep-sea fan, Northeast Pacific

    USGS Publications Warehouse

    Nelson, H.

    1976-01-01

    The asymmetrical Astoria Fan (110 ?? 180 km) developed off the Columbia River and Astoria submarine canyon during the Pleistocene. Morphology, stratigraphy, and lithology have been outlined for a Pleistocene turbidite, and a Holocene hemipelagic sedimentary regime to generate geologically significant criteria for comparison with ancient equivalent deposits. Both gray silty clay of the Late Pleistocene and olive-gray clay of the Early Holocene are interrupted by turbidites. The few deeply incised fan valleys of the more steeply sloping upper fan contain thick, muddy and very poorly sorted sand and gravel beds that usually have poorly developed internal sedimentary structures. The numerous shallower fan valleys and distributaries of the flatter middle and lower fan contain thick, clean, and moderately sorted medium to fine sands that are vertically graded in texture, composition and well-developed internal sedimentary structures. Tuffaceous turbidites (containing Mazama ash, 6600 B.P.) can be traced as thick deposits (ca. 30-40 cm) throughout the Astoria Channel system and as thin correlative interbeds (ca. 1-2 cm) in interchannel areas. Similarly, sand/shale ratios are high throughout the fan valleys and the middle and lower fan areas of distributaries, but are low in the upper-fan interchannel areas. These depositional trends indicate that high-density turbidity currents carry coarse traction loads that remain confined in upper but not lower fan valleys. Fine debris selectively sorts out from channelized flows into overbank suspension flows that spread over the fan and deposit clayey silt. A high content of mica, plant fragments, and glass shards (if present) characterizes deposits of the overbank flows, a major process in the building of upper fan levees and interchannel areas. In the Late Pleistocene, turbidity currents funneled most coarse-grained debris through upper channels to depositional sites in middle and lower fan distributaries that periodically shifted

  6. Holocene disturbance dynamics from a pine-dominated forest in central British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Brown, K. J.; Hebda, N.; Condor, N.; Hebda, R.; Hawkes, B.

    2013-12-01

    A lake sediment record was retrieved from the Sub-Boreal Pine-Spruce biogeoclimatic zone on the Chilcotin Plateau in central British Columbia, Canada. The record is being analyzed for charcoal, pollen, and magnetic susceptibility, as well as insect and mollusc content. The oldest radiocarbon age is 9.2 cal BP, illustrating that the record spans most of the Holocene. Regarding fire disturbance, charcoal fragments are persistent throughout the core, revealing that fire disturbance has characterized the site for millennia. In total, 74 fire events were recognized. During the warm dry early Holocene, fire frequency was 12-15 fires 2000 yr-1 and peak magnitudes were low, possibly in response to a more open landscape. A change in fire regime occurred at ca. 5000 cal BP, as fire frequency increased, peaking at ca. 20 fires 2000 yr-1 by 3000 cal BP. Peak magnitude likewise increased notably, possibly in response to the development of denser forest cover. On-going analysis of pollen will better constrain the vegetation history in this poorly sampled region. In contrast to charcoal, which was pervasive, Dendroctonus ponderosae (mountain pine beetle) remains were absent in both modern and paleo samples. Given that several insect outbreaks have occurred in the region in the last 100 years, the scarcity of remains is likely related to taphonomic issues.

  7. The Birougou Mountains: Forested throughout the Holocene

    NASA Astrophysics Data System (ADS)

    Pietsch, S. A.; Tanga, J.-J.; Ngok-Banak, L.

    2009-04-01

    The Congo basin with an area of ~400 million ha harbours the second largest tropical forest complex of the world which covers ~60% of the area. Besides tropical rain forest the savannah biome comprises the second naturally abundant ecosystem type. During the Holocene (20.000 yrs. BP - Modern Times) the distribution of forest and savannas changed with changing climate and during the last glacial maximum (~20.000 yrs. BP) most of the Congo basin was covered by savannas and the Congolian rain forests were confined to refuge areas. Later the distribution between savannas and rainforest changed with changing climate, whereby in some regions rainforest and savannas replaced each other while on some sites one vegetation type persisted. During drier periods of the Holocene the rain forest biome was confined to refuge areas, which formed a conservation reservoir for forest re-extension during more humid, i.e. forest favourable, climatic periods. In order to understand the dynamics of the forest/savannah replacement process reference states of patches of stable savannah or stable rain forest are needed. Within this paper we will describe a patch of stable rain forest vegetation located at the Birougou Mountains in Gabon, and demonstrate that rain forest vegetation has continuously persisted since the Holocene climate optimum dated at around ~6.000 yrs. B.P. by using the signature of stable Carbon isotope discrimination of photosynthesis. Savannah grasses follow the C4-type of photosynthesis while forest vegetation exhibits C3 photosynthesis. Accordingly they differ in the d13C ratios of carbon incorporated into biomass. Soil organic Carbon originates from decomposition of litter inputs. d13C values along a vertical soil profile thus indicate persistence or past changes in vegetation cover. 14C age of soil humic acids, indicate the mean residence time of soil organic carbon. Results indicate that at the Birougou mountains (in contrast to other parts of the Congo basin) litter

  8. [Chemical composition analysis of early neolithic pottery unearthed from Xiaohuangshang site, Zhejiang Province and Jiahu site, Henan Province by energy disperse X-ray fluorescence].

    PubMed

    Chen, Qian-Qian; Yang, Yu-Zhang; Zhang, Ju-Zhong; Cui, Wei

    2011-11-01

    The major elements in the early neolithic potteries unearthed from Xiaohuangshan site, Zhejiang Province and Jiahu site, Henan Province were determined by energy disperse X-ray fluorescence (EDXRF). The results show that the chemical compositions of the potteries from these two sites possess obvious regional features respectively. Compared with the specimen from Jiahu site, the potteries from Xiaohuangshan site have the common feature of ancient Chinese southern ceramics with high silicon and low aluminum contents. Simultaneously, the chemical composition of Xiaohuangshan pottery samples nearly unchanged from its early stage to the last stage. This phenomenon indicates that the source of the ceramic raw materials of Xiaohuangshan site was stable, and the continuous improvement of its pottery quality was mainly due to the progress in sintering techniques. However, the chemical composition of Jiahu potteries changed a lot in its three different periods. This change occurred because a large number of admixtures were added to the pottery bodies to improve their operating performances. These results also show that the improvements of pottery making techniques in different Chinese areas may have their own evolution directions respectively for the different geographical environments.

  9. Mid-Holocene Climate and Culture Change in the Atacama Desert, Northern Chile

    NASA Astrophysics Data System (ADS)

    Grosjean, Martin; Núñez, Lautaro; Cartajena, Isabel; Messerli, Bruno

    1997-09-01

    Twenty archaeological campsites intercalated between more than 30 debris flows caused by heavy rainfall events between 6200 and 3100 14C yr B.P. have recently been discovered at Quebrada Puripica in the Atacama Desert of northern Chile. This record provides detailed information about extreme, short-lived climatic events during the hyperarid mid-Holocene period. For the first time, we found evidence of continuous human occupation in this area, filling the regional hiatus in the Atacama basin ("Silencio Arqueologico") between 8000 and 4800 14C yr B.P. The transformation of Early Archaic hunters into the complex Late Archaic cultural tradition was an adaptive process. During this time, the site was a local ecological refuge with abundant resources in a generally hostile environment.

  10. Holocene fire history reconstruction using Tibetan lacustrine sediments

    NASA Astrophysics Data System (ADS)

    Callegaro, Alice; Kirchgeorg, Torben; Battistel, Dario; Bird, Broxton; Barbante, Carlo

    2016-04-01

    The important role that biomass burning playsin influencing the Holocene'sclimate is still under discussion. The present work gives information about past biomass burning events in the Tibetan Plateau and helps to increase the understanding of the interaction between climate, humans and fire activity during Holocene. Asiatic area is one of the centers of the advent of agriculture and pastoralism, and it is a strategic area for understanding the interaction between human and fire during the Holocene. We reconstructed past biomass burning events and vegetation from sediments collected from lake Paru Co, a small moraine dammed lake located in the Tibetan Plateau at 4845 m above sea level. We extracted lake sediment samples by accelerate solvent extraction and analysed different organic molecular proxies by GC-MS and IC-MS. We used monosaccharide anhydrides, levoglucosan and its isomers, as proxies for biomass burning. These are specific molecular markers originated from the pyrolysis of cellulose showing significant fire events and indicate changes in burned fuel. Furthermore we analysed polycyclic aromatic hydrocarbons (PAH) as additional combustion proxies. For a better understanding of changes in vegetation andof human habitation at the lake shore we analysed n-alkanes and sterols. Comparing the data of this multi-proxy approach used in the studied area with climatic and meteorological literature data, reconstruction and contextualization of past fire events are possible: we can see the agreement between dry climate period and presence of more intense fire events, especially in the Early Holocene.

  11. Site fidelity and condition metrics suggest sequential habitat use by early juvenile snook

    USGS Publications Warehouse

    Brame, Adam B.; McIvor, Carole; Peebles, Ernst B; Hollander, David J.

    2014-01-01

    The common snook Centropomus undecimalis is an estuarine-dependent fish that relies on landward wetlands as nursery habitat. Despite its economic importance, portions of the snook's early life history are poorly understood. We compared habitat use of young-of-the-year (YOY) snook in 2 geomorphic mesohabitats (tidal pond and tidal creek) along an estuarine gradient (upstream vs. downstream) within a single wetland during fall recruitment. We used abundance, length, condition indices, and stable isotopes to assess ontogenetic mesohabitat use and site fidelity. We found that (1) YOY snook were more abundant within the upstream creek and ponds; (2) the smallest snook were found only in ponds; (3) snook from ponds had lower condition (Fulton's K and hepatosomatic index); (4) snook began moving from ponds to the creek at ~40 mm standard length; and (5) snook from the 2 mesohabitats were isotopically distinct, indicating high site fidelity at rather small spatial scales. Collectively, these data identified sequential use of mesohabitats, wherein seaward-spawned YOY snook moved landward and recruited to pond habitats, where they dedicated energy to growth (as length) before making an ontogenetic habitat shift to the creek. Once in the creek, YOY snook condition improved as they approached maturity and started the downstream return towards seaward locations. The wetland network that was previously viewed as generalized nursery habitat instead consists of mesohabitats that support different life stages in sequence. This represents ontogenetic habitat complementation, in which lower availability of a required mesohabitat type may limit the entire wetland's contribution to the adult population.

  12. Mass safe male circumcision: early lessons from a Ugandan urban site - a case study

    PubMed Central

    Galukande, Moses; Sekavuga, Denis Bbaale; Duffy, Kevin; Wooding, Nicholas; Rackara, Sam; Nakaggwa, Florence; Nagaddya, Teddy; Elobu, Alex Emmanuel; Coutinho, Alex

    2012-01-01

    Introduction It has been proven in several randomized clinical trials that HIV transmission from female to male is reduced by 60% and more among circumcised males. The national target for Uganda by 2015 is to circumcise 4.2 million adult males, an unprecedented number requiring a pragmatic approach and effective model(s) to deliver this target. The objective of the study was to describe early lessons learnt at a start up of a mass safe male circumcision (SMC) program in an urban Ugandan site, implemented through task shifting and a private public partnership approach. Methods A case study of an urban SMC site in Uganda's capital, Kampala with a catchment population of approximately 0.8 million adult males aged between 15 and 49 years. Client enrollment was voluntary; mobilization was by word of mouth and through the media. Non Physician clinicians (NPC) carried out the majority of the SMCs. The SMC and voluntary counseling and testing (VCT), adverse events (AE) management and follow up were done as per set national guidelines. The supervision was by a public and private service provider. All clients were consented. Results A total of 3000 males were circumcised in 27 days spread over four months. The AE rate was 2.1% all AEs were mild and reversible. No deaths occurred. The work rate was 111 SMCs per day. There was sufficient demand for SMC despite minimal mobilization effort. The bulk of the SMC work was successfully carried out by the NPCs. Conclusion Private Public Partnership and task shifting approaches were successful at the start up phase and we anticipate will be feasible for the scale up. PMID:23396906

  13. Pleistocene and Holocene geomorphological development in the Algarve, southern Portugal

    NASA Astrophysics Data System (ADS)

    Chester, David K.

    2012-06-01

    A detailed chronological framework for Pleistocene and Holocene geomorphology and landscape evolution in the Algarve is proposed. With regards to the Pleistocene, attention has focused on the origin, dating and stratigraphy of the Ludo Formation. Subsuming the classifications of earlier writers, it is now proposed that during the Pliocene a marine transgression occurred across a tectonically controlled basin that was constrained by the mountains of the Algarve interior to the north. Fluvial sands were then deposited in a regressive phase during the late Pliocene/early Pleistocene, while braided streams operating under semi-arid conditions subsequently laid down sands and gravels in the middle and upper Pleistocene. Lying unconformably over the Ludo Formation is an alluvial deposit (Odiáxere gravels and Loulé sands) of late Pleistocene/early Holocene date that is found within the river valleys of the Algarve. In the early-Holocene (ca.10, 000-ca.7000 BP) and early late-Holocene (ca.5000-ca.3000 BP), the situation in the Algarve was one of climatic amelioration (i.e., warmer and wetter conditions), rising sea levels, vegetation colonization, soil development and towards the end of this period trenching of the Odiáxere gravels and Loulé sands. From ca.3000 BP evidence is abundant that humans became important geomorphological agents either acting on their own or in combination with climatic factors. From around 5000 BP, conditions became dryer and, between ca.3000 BP and ca.700 BP, clearance of land by pre-Roman, Roman, and especially Islamic agricultural settlers caused widespread erosion and the deposition of extensive spreads of topsoil dominated sediment within river valleys (i.e., the Holocene terrace) and in coastal estuaries. A period followed up to 1900 CE when agricultural practices were less damaging to the soil, erosion was reduced and the Holocene terrace - together with coastal and estuarine deposits - was incised. In the past century and under

  14. Advancing family health through the Garden of Eatin': on-site food gardens in early childhood education.

    PubMed

    Chaufan, Claudia; Yeh, Jarmin; Sigal, Byron

    2015-04-01

    Nutritional practices develop over the life course. Developing healthy habits at an early age can contribute to combating increasing child obesity rates. Through a range of activities that rely on the presence of an on-site food garden, North Bay Children's Center (NBCC), an early childhood education program, has enacted a "culture of health" into all aspects of the curriculum to promote healthy eating practices among children, families, teachers and staff. NBCC's garden program serves as a model in early childhood education and as a community-based intervention to improve family health and prevent child obesity. PMID:25713934

  15. Advancing family health through the Garden of Eatin': on-site food gardens in early childhood education.

    PubMed

    Chaufan, Claudia; Yeh, Jarmin; Sigal, Byron

    2015-04-01

    Nutritional practices develop over the life course. Developing healthy habits at an early age can contribute to combating increasing child obesity rates. Through a range of activities that rely on the presence of an on-site food garden, North Bay Children's Center (NBCC), an early childhood education program, has enacted a "culture of health" into all aspects of the curriculum to promote healthy eating practices among children, families, teachers and staff. NBCC's garden program serves as a model in early childhood education and as a community-based intervention to improve family health and prevent child obesity.

  16. Effects of Holocene vegetation change on soils across the forest-grassland transition, northern Minnesota, and implications for erosion processes

    NASA Astrophysics Data System (ADS)

    Mason, Joseph; Kasmerchak, Chase; Keita, Hawa; Liang, Mengyu; Gruley, Kristine

    2016-04-01

    Boundaries between forest and grassland in the midlatitudes and their shifts in response to Holocene climatic change, provide opportunities to detect effects of life on landscapes. In northern Minnesota, USA, paleoecological research has documented that grassland and/or savanna expanded eastward in the dry early to middle Holocene. In the late Holocene, forest cover expanded westward at the expense of savanna and grassland. We studied soils at 20 sites spanning the forest-grassland transition. A dramatic change in soil morphology coincides approximately, though not exactly, with that transition as recorded in 1870s-1880s land surveys, suggesting that soils change rapidly in response to forest expansion (we are attempting to constrain the timescale of response through radiocarbon dating of deep soil organic matter in which stable C isotopes record past presence of grassland). The key changes from grassland to forest are loss of organic matter below a thin surface A horizon and greatly enhanced mobility and downward translocation of clay - particularly smectite - in forest soils. This results in upper soil horizons that have relatively low smectite content and low microaggregate stability (as detected through laser diffraction analysis of aggregate disintegration in laboratory experiments), especially below the thin A horizon. The best explanation for this change appears to involve differences in how OM is added to and accumulated in the soil under forest and grassland; soil acidity and base saturation change more gradually eastward along a gradient more likely to reflect climate than vegetation. Evidence of bioturbation (especially gopher burrowing) is much more common at former grassland sites. In addition to mixing OM downward in the soil, burrowing moves detrital carbonates upward, probably enhancing OM accumulation and aggregate stability. Research on geomorphic response to Holocene climatic change in the Midwestern US has often emphasized higher potential

  17. Hand and foot remains from the Gran Dolina Early Pleistocene site (Sierra de Atapuerca, Spain).

    PubMed

    Lorenzo, C; Arsuaga, J L; Carretero, J M

    1999-01-01

    We report here the study of the 22 hand and foot remains from the Early Pleistocene level TD6 of the Gran Dolina site at Sierra de Atapuerca (Burgos, Spain) recovered from 1994 to 1996. These remains are paratypes of Homo antecessor. All of the elements are briefly described and compared with other fossil hominids. The capitate has a constricted neck, well developed head, strong attachment for the ligamentum interosseum trapezoid-capitate, a palmarly placed trapezoid facet with a distinctive small dorsal trapezoid facet, a highly curved and oblique orientation of the second metacarpal facet, and a transversally oriented dorsodistal border. A hamate with a moderately projecting and lightly built hamulus; an inferred reduced styloid process on the third metacarpal base; a wide second metacarpal head; and middle phalanges with well marked insertions for the flexor digitorum superficialis muscle and wide heads. The morphology and dimensions of the pedal remains from TD6 are very similar to modern humans; but the base, proximal articular surface and shafts of the proximal hallucal phalanges are more rounded and the midshaft of the proximal toe phalanx is wider. PMID:10496998

  18. Integrated Geophysycal Prospecting in Late Antiquity and Early Medieval Sites in Italy

    NASA Astrophysics Data System (ADS)

    Giannotta, Maria Teresa; Leucci, Giovanni; De Giorgi, Lara; Matera, Loredana; Persico, Raffaele; Muci, Giuseppe

    2016-04-01

    In this contribution, the results of some integrated geophysical prospecting (magnetometric and GPR) are exposed. This work has been performed in collaboration between archaeologists and geophysicists within the research project "History and Global Archaeology of the Rural Landascapes in Italy, between Late Antiquity and Medieval period. Integrated systems of sources, methodologies, and technologies for a sustainable development", financed by the Italian Ministry for Instruction, University and Research MIUR. In particular, the archaeological sites of Badia and San Giovanni in Malcantone, both in the Apulia Region (eastern-southern Italy) have been prospect. The sites have been identified on the basis of available documents, archaeological surveys and testimonies. In particular, we know that in Badia [1] it was probable the presence of an ancient roman villa of the late ancient period (strongly damaged by the subsequent ploughing activities). Whereas in San Giovanni there is still, today, a small chapel (deconsecrated) that was likely to be part of a previous larger church (probably a basilica of the early Christian period) restricted in the subsequent centuries (probably in more phases). The Saracen raids of the XVI centuries made the site ruined and abandoned. In both sites integrated prospecting have been performed [2-6] with a the integration of archaeological, magnetometer and a GPR data have provided some interesting results, allowing to overcome the difficulties relative to an extensive GPR prospecting, that could not be performed because of the intrinsic superficial roughness and/or the intensive ploughing activities. The prospecting activities, in particular, have added elements that seem to confirm the main archaeological hypothesis that motivate their performing, as it will be show at the conference. References [1] M. T, Giannotta, G. Leucci, R. Persico, M. Leo Imperiale, The archaeological site of Badia in terra d'Otranto: contribution of the

  19. Holocene environmental evolution of the SE Greenland Shelf North and South of the Denmark Strait: Irminger and East Greenland current interactions

    NASA Astrophysics Data System (ADS)

    Jennings, A.; Andrews, J.; Wilson, L.

    2011-04-01

    Holocene climatic and paleoceanographic development of the SE Greenland Shelf is studied from cores MD99-2317 and MD99-2322, at sites north and south of the Denmark Strait, respectively. Lithofacies, IRD counts, calcium carbonate percentages, benthic and planktic foraminiferal assemblages and oxygen isotope analyses, and summer SSTs reveal significant climate variations in the Holocene driven by declining solar insolation and its interaction with waning continental ice sheets, and changing atmospheric pressure patterns. Large changes in the East Greenland and Irminger Currents and the Greenland Ice Sheet are manifested as a 4-part division of the Holocene. An early Holocene cold interval dominated by melting of the Greenland Ice Sheet and Polar Front retreat extends from 11.8 to 9.5 cal kyr BP. A cold interval from 9.5 to 8.1 cal kyr BP involved episodic cooling of the Irminger Current resulting from the last phases of Laurentide Ice Sheet deglaciation and delayed the Holocene optimum off East Greenland by 3 kyr relative to peak summer solar insolation, which likely helped to limit the early Holocene melting of the Greenland Ice Sheet. The period 8.1-3.5 cal kyr BP represents a climatic optimum interval of maximum Greenland Ice Sheet retreat and strong Irminger Current inflow to the Denmark Strait. Between 6.8 and 3.5 cal kyr BP, the Irminger Current penetrated further North into the Nordic Seas than has been observed in recent decades. This signal is consistent with diminished northerly winds, a weaker Greenland High and contracted subpolar gyre. By 5 cal kyr BP, periods of increased Polar Water and decreasing salinity in the Irminger Current suggest a transition toward expansion of the subpolar gyre and increased Polar Water in the EGC. The Neoglacial interval from 3.5 to 0.2 cal kyr BP was cold and variable with increased freshwater forcing from the Arctic Ocean, advance of the Greenland Ice Sheet and southward advance of the Polar Front. Enhanced northerly

  20. A pollen-based environmental reconstruction in Lake Hazar (Eastern Turkey) during the Late Pleistocene-Holocene: Example for the Eastern Mediterranean Realm

    NASA Astrophysics Data System (ADS)

    Biltekin, Demet; Kadir Eris, Kürsad; Namik Cagatay, Memet; Nagihan Arslan, Tugce; Akcer On, Sena; Acar, Dursun

    2016-04-01

    difference between Lake Hazar and some Near East sites is found concerning the delay during the early Holocene expansion of Quercus pollen. Such delay from the other studied sites in the Eastern Mediterranean has not been recorded in Lake Hazar. This can be explained by the existence of a warm and humid climate which provided favorable conditions for spreading of deciduous Quercus, starting in the early Holocene.

  1. 10 CFR 51.105 - Public hearings in proceedings for issuance of construction permits or early site permits...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... concerning the benefits assessment (e.g., need for power) or alternative energy sources if those issues were... 10 Energy 2 2011-01-01 2011-01-01 false Public hearings in proceedings for issuance of construction permits or early site permits; limited work authorizations. 51.105 Section 51.105 Energy...

  2. 10 CFR 51.105 - Public hearings in proceedings for issuance of construction permits or early site permits...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... concerning the benefits assessment (e.g., need for power) or alternative energy sources if those issues were... 10 Energy 2 2014-01-01 2014-01-01 false Public hearings in proceedings for issuance of construction permits or early site permits; limited work authorizations. 51.105 Section 51.105 Energy...

  3. 10 CFR 51.105 - Public hearings in proceedings for issuance of construction permits or early site permits...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... concerning the benefits assessment (e.g., need for power) or alternative energy sources if those issues were... 10 Energy 2 2012-01-01 2012-01-01 false Public hearings in proceedings for issuance of construction permits or early site permits; limited work authorizations. 51.105 Section 51.105 Energy...

  4. 10 CFR 51.50 - Environmental report-construction permit, early site permit, or combined license stage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... costs of the proposed action or an evaluation of alternative energy sources. (3) For other than light... 10 Energy 2 2012-01-01 2012-01-01 false Environmental report-construction permit, early site permit, or combined license stage. 51.50 Section 51.50 Energy NUCLEAR REGULATORY COMMISSION...

  5. 10 CFR 51.105 - Public hearings in proceedings for issuance of construction permits or early site permits...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... concerning the benefits assessment (e.g., need for power) or alternative energy sources if those issues were... 10 Energy 2 2010-01-01 2010-01-01 false Public hearings in proceedings for issuance of construction permits or early site permits; limited work authorizations. 51.105 Section 51.105 Energy...

  6. 10 CFR 51.50 - Environmental report-construction permit, early site permit, or combined license stage.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... costs of the proposed action or an evaluation of alternative energy sources. (3) For other than light... 10 Energy 2 2010-01-01 2010-01-01 false Environmental report-construction permit, early site permit, or combined license stage. 51.50 Section 51.50 Energy NUCLEAR REGULATORY COMMISSION...

  7. 10 CFR 51.50 - Environmental report-construction permit, early site permit, or combined license stage.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... costs of the proposed action or an evaluation of alternative energy sources. (3) For other than light... 10 Energy 2 2014-01-01 2014-01-01 false Environmental report-construction permit, early site permit, or combined license stage. 51.50 Section 51.50 Energy NUCLEAR REGULATORY COMMISSION...

  8. 10 CFR 51.50 - Environmental report-construction permit, early site permit, or combined license stage.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... costs of the proposed action or an evaluation of alternative energy sources. (3) For other than light... 10 Energy 2 2013-01-01 2013-01-01 false Environmental report-construction permit, early site permit, or combined license stage. 51.50 Section 51.50 Energy NUCLEAR REGULATORY COMMISSION...

  9. 10 CFR 51.105 - Public hearings in proceedings for issuance of construction permits or early site permits...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... concerning the benefits assessment (e.g., need for power) or alternative energy sources if those issues were... 10 Energy 2 2013-01-01 2013-01-01 false Public hearings in proceedings for issuance of construction permits or early site permits; limited work authorizations. 51.105 Section 51.105 Energy...

  10. 10 CFR 51.50 - Environmental report-construction permit, early site permit, or combined license stage.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... costs of the proposed action or an evaluation of alternative energy sources. (3) For other than light... 10 Energy 2 2011-01-01 2011-01-01 false Environmental report-construction permit, early site permit, or combined license stage. 51.50 Section 51.50 Energy NUCLEAR REGULATORY COMMISSION...

  11. 10 CFR 2.604 - Notice of hearing on application for early review of site suitability issues in construction...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Notice of hearing on application for early review of site suitability issues in construction permit proceeding. 2.604 Section 2.604 Energy NUCLEAR REGULATORY COMMISSION... practicable, the membership of any atomic safety and licensing board designated to preside in the...

  12. 75 FR 71467 - Exelon Nuclear Texas Holdings, LLC, Early Site Permit Application for the Victoria County Station...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-23

    ..., BWR Projects Branch, Division of New Reactor Licensing, Office of New Reactors, U.S. Nuclear... From the Federal Register Online via the Government Publishing Office NUCLEAR REGULATORY COMMISSION Exelon Nuclear Texas Holdings, LLC, Early Site Permit Application for the Victoria County...

  13. Dynamics of North Atlantic Deep Water masses during the Holocene

    NASA Astrophysics Data System (ADS)

    Hoogakker, Babette A. A.; Chapman, Mark R.; McCave, I. Nick; Hillaire-Marcel, Claude; Ellison, Christopher R. W.; Hall, Ian R.; Telford, Richard J.

    2011-12-01

    High resolution flow speed reconstructions of two core sites located on Gardar Drift in the northeast Atlantic Basin and Orphan Knoll in the northwest Atlantic Basin reveal a long-term decrease in flow speed of Northeast Atlantic Deep Water (NEADW) after 6,500 years. Benthic foraminiferal oxygen isotopes of sites currently bathed in NEADW show a 0.2‰ depletion after 6,500 years, shortly after the start of the development of a carbon isotope gradient between NEADW and Norwegian Sea Deep Water. We consider these changes in near-bottom flow vigor and benthic foraminiferal isotope records to mark a significant reorganization of the Holocene deep ocean circulation, and attribute the changes to a weakening of NEADW flow during the mid to late Holocene that allowed the shoaling of Lower Deep Water and deeper eastward advection of Labrador Sea Water into the northeast Atlantic Basin.

  14. Jobs-Plus Site-by-Site: An Early Look at Program Implementation. A Jobs-Plus Working Paper.

    ERIC Educational Resources Information Center

    Bloom, Susan Philipson, Ed.

    This working paper assembles chapters written by onsite researchers about program implementation in each of seven cities included in the Job-Plus Community Revitalization Initiative for Public Housing Families. This report, which provides a "snapshot" of each site, documents the nature and extent of implementation as of that point in time. Chapter…

  15. Holocene peatland shifts in vegetation, carbon, and climate at Imnavait, Alaska

    NASA Astrophysics Data System (ADS)

    Peteet, D. M.; Nichols, J. E.; Ouni, S.; Pavia, F.; Pearl, Y.

    2012-12-01

    The Imnavait Creek basin (68 40'N, 149 20'W; elevation 875-945 m) in the foothills of the Brooks Range, AK has been well studied in terms of modern vegetational communities, hydrology, and soils. But paleoclimate and paleovegetation reconstructions are limited. We retrieved a 2-m peatland core to examine the macrofossil/biomarker/carbon sequestration history throughout the Holocene and late-glacial. AMS 14C dates of the macrofossil remains will allow us to calculate carbon sequestration rates. The Holocene history (the top meter) records marked shifts in vascular plant as well as bryophyte history. A tri-partite sequence is apparent, with Andromeda/Sphagnum remains abundant in the early Holocene. The absence of bryophytes and the presence of Eriophorum and Carex achenes characterize the mid-Holocene. Andromeda and Betula nana with Sphagnum remains are abundant in the upper 30 cm of the core. Hydrogen isotope ratios of leaf wax alkanes record higher effective moisture in the early and late Holocene, suggesting more evaporative loss in the mid-Holocene which is characterized by Eriophorum. We compare our results with previously observed palynological shifts from lakes in the region and place this Arctic paleorecord in a larger perspective of peatland histories in a N-S transect covering nearly 10 degrees of latitude across Alaska. This tripartite pattern of effective moisture appears to be the same throughout the Alaskan transect, suggesting strong climatic control.

  16. 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.

  17. Two Holocene paleofire records from Peten, Guatemala: Implications for natural fire regime and prehispanic Maya land use

    NASA Astrophysics Data System (ADS)

    Anderson, Lysanna; Wahl, David

    2016-03-01

    Although fire was arguably the primary tool used by the Maya to alter the landscape and extract resources, little attention has been paid to biomass burning in paleoenvironmental reconstructions from the Maya lowlands. Here we report two new well-dated, high-resolution records of biomass burning based on analysis of macroscopic fossil charcoal recovered from lacustrine sediment cores. The records extend from the early Holocene, through the full arc of Maya prehistory, the Colonial, and post-Colonial periods (~ 9000 cal yr BP to the present). (Hereafter BP) The study sites, Lago Paixban and Lago Puerto Arturo, are located in northern Peten, Guatemala. Results provide the first quantitative analysis from the region demonstrating that frequent fires have occurred in the closed canopy forests since at least the early Holocene (~ 9000 BP), prior to occupation by sedentary agriculturalists. Following the arrival of agriculture around 4600 BP, the system transitioned from climate controlled to anthropogenic control. During the Maya period, changes in fire regime are muted and do not appear to be driven by changes in climate conditions. Low charcoal influx and fire frequency in the Earliest Preclassic period suggest that land use strategies may have included intensive agriculture much earlier than previously thought. Preliminary results showing concentrations of soot/black-carbon during the middle and late Preclassic periods are lower than modern background values, providing intriguing implications regarding the efficiency of Maya fuel consumption.

  18. Two Holocene paleofire records from Peten, Guatemala: Implications for natural fire regime and prehispanic Maya land use

    USGS Publications Warehouse

    Anderson, Lysanna; Wahl, David B.

    2015-01-01

    Although fire was arguably the primary tool used by the Maya to alter the landscape and extract resources, little attention has been paid to biomass burning in paleoenvironmental reconstructions from the Maya lowlands. Here we report two new well-dated, high-resolution records of biomass burning based on analysis of macroscopic fossil charcoal recovered from lacustrine sediment cores. The records extend from the early Holocene, through the full arc of Maya prehistory, the Colonial, and post-Colonial periods (~ 9000 cal yr BP to the present). (Hereafter BP) The study sites, Lago Paixban and Lago Puerto Arturo, are located in northern Peten, Guatemala. Results provide the first quantitative analysis from the region demonstrating that frequent fires have occurred in the closed canopy forests since at least the early Holocene (~ 9000 BP), prior to occupation by sedentary agriculturalists. Following the arrival of agriculture around 4600 BP, the system transitioned from climate controlled to anthropogenic control. During the Maya period, changes in fire regime are muted and do not appear to be driven by changes in climate conditions. Low charcoal influx and fire frequency in the Earliest Preclassic period suggest that land use strategies may have included intensive agriculture much earlier than previously thought. Preliminary results showing concentrations of soot/black-carbon during the middle and late Preclassic periods are lower than modern background values, providing intriguing implications regarding the efficiency of Maya fuel consumption.

  19. The climate of Europe during the Holocene: a gridded pollen-based reconstruction and its multi-proxy evaluation

    NASA Astrophysics Data System (ADS)

    Mauri, A.; Davis, B. A. S.; Collins, P. M.; Kaplan, J. O.

    2015-03-01

    We present a new gridded climate reconstruction for Europe for the last 12,000 years based on pollen data. The reconstruction is an update of Davis et al. (2003) using the same methodology, but with a greatly expanded fossil and surface-sample dataset and more rigorous quality-control. The modern pollen dataset has been increased by more than 80%, and the fossil pollen dataset by more than 50%, representing almost 60,000 individual pollen samples. The climate parameters reconstructed include summer/winter and annual temperatures and precipitation, as well as a measure of moisture balance, and growing degree-days above 5 °C. Confidence limits were established for the reconstruction based on transfer function and interpolation uncertainties. The reconstruction takes account of post-glacial isostatic readjustment which resulted in a potential warming bias of up to +1-2 °C for parts of Fennoscandia in the early Holocene, as well as changes in palaeogeography resulting from decaying ice sheets and rising post-glacial sea-levels. This new dataset has been evaluated against previously published independent quantitative climate reconstructions from a variety of archives on a site-by-site basis across Europe. The results of this comparison are generally very good; only chironomid-based reconstructions showed substantial differences with our values. Our reconstruction is available for download as gridded maps throughout the Holocene on a 1000-year time-step. The gridded format makes our reconstructions suitable for comparison with climate model output and for other applications such as vegetation and land-use modelling. Our new climate reconstruction suggests that warming in Europe during the mid-Holocene was greater in winter than in summer, an apparent paradox that is not consistent with current climate model simulations and traditional interpretations of Milankovitch theory.

  20. Multiproxy evidence of Holocene climate variability from estuarine sediments, eastern North America

    USGS Publications Warehouse

    Cronin, T. M.; Thunell, R.; Dwyer, G.S.; Saenger, C.; Mann, M.E.; Vann, C.; Seal, R.R.

    2005-01-01

    We reconstructed paleoclimate patterns from oxygen and carbon isotope records from the fossil estuarine benthic foraminifera Elphidium and Mg/ Ca ratios from the ostracode Loxoconcha from sediment cores from Chesapeake Bay to examine the Holocene evolution of North Atlantic Oscillation (NAO)-type climate variability. Precipitation-driven river discharge and regional temperature variability are the primary influences on Chesapeake Bay salinity and water temperature, respectively. We first calibrated modern ??18 Owater to salinity and applied this relationship to calculate trends in paleosalinity from the ??18 Oforam, correcting for changes in water temperature estimated from ostracode Mg /Ca ratios. The results indicate a much drier early Holocene in which mean paleosalinity was ???28 ppt in the northern bay, falling ???25% to ???20 ppt during the late Holocene. Early Holocene Mg/Ca-derived temperatures varied in a relatively narrow range of 13?? to 16??C with a mean temperature of 14.2??C and excursions above 16??C; the late Holocene was on average cooler (mean temperature of 12.8??C). In addition to the large contrast between early and late Holocene regional climate conditions, multidecadal (20-40 years) salinity and temperature variability is an inherent part of the region's climate during both the early and late Holocene, including the Medieval Warm Period and Little Ice Age. These patterns are similar to those observed during the twentieth century caused by NAO-related processes. Comparison of the midlatitude Chesapeake Bay salinity record with tropical climate records of Intertropical Convergence Zone fluctuations inferred from the Cariaco Basin titanium record suggests an anticorrelation between precipitation in the two regions at both millennial and centennial timescales. Copyright 2005 by the American Geophysical Union.

  1. Configuration and specifications of an Unmanned Aerial Vehicle (UAV) for early site specific weed management.

    PubMed

    Torres-Sánchez, Jorge; López-Granados, Francisca; De Castro, Ana Isabel; Peña-Barragán, José Manuel

    2013-01-01

    A new aerial platform has risen recently for image acquisition, the Unmanned Aerial Vehicle (UAV). This article describes the technical specifications and configuration of a UAV used to capture remote images for early season site- specific weed management (ESSWM). Image spatial and spectral properties required for weed seedling discrimination were also evaluated. Two different sensors, a still visible camera and a six-band multispectral camera, and three flight altitudes (30, 60 and 100 m) were tested over a naturally infested sunflower field. The main phases of the UAV workflow were the following: 1) mission planning, 2) UAV flight and image acquisition, and 3) image pre-processing. Three different aspects were needed to plan the route: flight area, camera specifications and UAV tasks. The pre-processing phase included the correct alignment of the six bands of the multispectral imagery and the orthorectification and mosaicking of the individual images captured in each flight. The image pixel size, area covered by each image and flight timing were very sensitive to flight altitude. At a lower altitude, the UAV captured images of finer spatial resolution, although the number of images needed to cover the whole field may be a limiting factor due to the energy required for a greater flight length and computational requirements for the further mosaicking process. Spectral differences between weeds, crop and bare soil were significant in the vegetation indices studied (Excess Green Index, Normalised Green-Red Difference Index and Normalised Difference Vegetation Index), mainly at a 30 m altitude. However, greater spectral separability was obtained between vegetation and bare soil with the index NDVI. These results suggest that an agreement among spectral and spatial resolutions is needed to optimise the flight mission according to every agronomical objective as affected by the size of the smaller object to be discriminated (weed plants or weed patches).

  2. Configuration and specifications of an Unmanned Aerial Vehicle (UAV) for early site specific weed management.

    PubMed

    Torres-Sánchez, Jorge; López-Granados, Francisca; De Castro, Ana Isabel; Peña-Barragán, José Manuel

    2013-01-01

    A new aerial platform has risen recently for image acquisition, the Unmanned Aerial Vehicle (UAV). This article describes the technical specifications and configuration of a UAV used to capture remote images for early season site- specific weed management (ESSWM). Image spatial and spectral properties required for weed seedling discrimination were also evaluated. Two different sensors, a still visible camera and a six-band multispectral camera, and three flight altitudes (30, 60 and 100 m) were tested over a naturally infested sunflower field. The main phases of the UAV workflow were the following: 1) mission planning, 2) UAV flight and image acquisition, and 3) image pre-processing. Three different aspects were needed to plan the route: flight area, camera specifications and UAV tasks. The pre-processing phase included the correct alignment of the six bands of the multispectral imagery and the orthorectification and mosaicking of the individual imag