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Weichselian Glaciation in Estonia
268
Abstracts / Quaternary International 279-280 (2012) 233–345
Laminated sediments from the proglacial lake Hvítárvatn (422 m asl) are used to construct a continuous record of environmental change and the activity of Langjökull for the past 10.2 ka. Lake sediment cores were collected from multiple locations using the DOSECC GLAD-200 core rig, and the position of the Saksunarvatn tephra layer (ca. 10.2 ka) at a depth of w18 m, confirms that the cores span the Holocene. Sedimentological analysis and tephrochronology verify the presence of clastic annual varves, and an age model is constructed by splicing a varve chronology of the past 3 ka with a tephra-constrained, paleomagnetic secular variation derived chronology for older sediments. Multiple proxies, including sedimentation rate, bulk density, IRD, TOC, C:N, 13C, and BSi, evaluated at high resolution (annual to multi-decadal) reveal a dynamic Holocene terrestrial climate. The proxy data indicate that, following regional deglaciation of the main Iceland ice sheet, glacial ice had either disappeared from the basin entirely, or was contributing an insignificant volume of sediment to the lake. A pronounced increase in sedimentation rate, sediment density, C:N, and TOC between 8.5 and 8.0 ka suggest cold summers with glacier growth and/ or landscape destabilization within the catchment. Subsequently, Holocene thermal maximum (HTM) conditions were achieved, resulting in high within-lake productivity and little/no glacier ice in the watershed. Neoglaciation is recorded as a broad trend toward cooler summers and the regrowth and expansion of Langjökull that began by ca. 6 ka, with a notable increase in ice-cap size and landscape instability at 4.2 ka. The past millennium is characterized by the abrupt onset of sustained cold periods at ca. 550 and 1250 AD, separated by an interval of relative warmth from ca. 950 to 1150 AD. The greatest Holocene extent of Langjökull occurred in the nineteenth century and is coincident with peak landscape instability. WEICHSELIAN GLACIATION IN ESTONIA Katrin Lasberg. University of Tartu, Institute of Ecology and Eart, Estonia E-mail address: [email protected]
Knowledge of the chronology and palaeogeography of the Weichselian Glaciation in Estonia has developed considerably and has been supported by new chronological, biostratigraphical and palaeogeographical data. Both marine and continental Eemian interglacial deposits are present in Estonia and pollen assemblages indicate that the entire Eemian vegetation cycle is present in the sediments. Recent OSL ages from Weichselian Stage lacustrine and stream sediments indicate that Estonia was ice-free at least between 115 – 68 ka and 44 – 27 ka ago which leaves 24 ka (68 – 44 ka) for a possible early Middle Weichselian glaciation. The beginning of the Late Weichselian glaciation in Estonia has not been directly dated but the available data from Eastern Finland and Western Latvia suggest that the onset may have occurred ca 22 ka ago. The last deglaciation of Estonia from the oldest, the Haanja (North Lithuanian, Luga) ice-marginal zone, to the recession of ice from the youngest, the Palivere zone, took place between ca 14.7 - 12.7 ka or between 14 675 – 12 675 varve years ago. The mean annual rate of ice recession in Estonia from the Haanja to the Palivere icemarginal zone is calculated to be ca 110 m/year. As the onset of the Late Weichselian glaciation in Estonia occurred no earlier than 22 ka ago, and the ice retreated from the Palivere zone at 12.7 ka, the maximum duration of the Late Weichselian glaciation in Estonia was ca 9.3 ka. ARCHAEOLOGICAL AND PALEOENVIRONMENTAL EVIDENCE FOR A LATE PLEISTOCENE HUMAN SETTLEMENT IN THE HYPERARID CORE OF THE ATACAMA DESERT (21 S) Claudio Latorre. CASEB, Universidad Catolica de Chile, Chile E-mail address: [email protected]
The antiquity and radiocarbon chronology of the first human settlements of South America is one of the most widely debated topics in American archaeology. Issues include points of entry, dispersal mechanisms and the process of initial human settlement that then diversified into regional cultural processes. The immigration paths taken, including the coastal or inland routes, as well as the cultural diversity present in these early settlements are also heavily disputed. Despite evidence for the earliest occupations of South America as old as 14.6 ka, there is a notable absence of dates >11 ka along the coast of southern Peru as well as in the central Atacama. Here, we propose that extensive areas in the foreboding Atacama
Desert have been overlooked regarding their potential for harboring such early sites. Spanning over 1500 km, the hyperarid core of the Atacama Desert is truly one of the driest places on Earth. Paleoecological, stratigraphical and geomorphological evidence, however, indicate that portions of this desert contained in-stream wetlands and/or riparian woodlands between 17 to 11 ka, coeval with extensive wet phases across the central Andes. Increased summer rainfall over the regional highlands became manifest in the lower desert as increased runoff and heightened groundwater tables and the extensive aggradation of fluvial terraces covered with vegetation. Such resources would have been ideal areas for early settlements. One particular such settlement was recently uncovered by our research team at site Quebrada Mani 12 (S21.09 ; W69.43 ; 900 m). Six radiocarbon dates on charcoal excavated from one test pit containing bifaces and other lithic artifacts span from 14.5 to 11.8 ka. These ages indicate that site QM12 is perhaps one of the oldest known archaeological sites from northern Chile. Our study also reveals the vast untapped potential of this region for finding even more such early sites by linking archaeological surveys to regional paleoenvironmental change. OSL- AND INFRARED RADIOFLUORESCENCE (IR-RF) DATING OF UPPERAND MIDDLE PLEISTOCENE FLUVIAL UNITS FROM THE HEIDELBERG BASIN, SOUTHERN GERMANY Tobias Lauer. Geographisches Institut, Germany E-mail address: [email protected]
The Upper Rhine Graben (URG) hosts more than 500 m thick Quaternary fluvial and limnic-fluvial deposits. These sediments are characterised by thick gravel and sand layers which can be correlated with cold periods and by intercalated finer grained peat-rich layers representing warmer periods. In the framework of the Heidelberg Basin Drilling Project, we applied quartz optical stimulated luminescence (OSL) dating to Upper Pleistocene deposits and Infrared Radiofluorescence (IR-RF) dating using K-feldspar to Middle Pleistocene fluvial units. The aim of the present study is to provide a more reliable chronology for such sediments yielding the records of climate changes und tectonic processes. Samples were taken from two sediment cores drilled into the Heidelberg Basin infill near the city of Viernheim and at Ludwigshafen. The results show that Eemian sediments are not exposed at the study area and that there is a significant chronological gap between the Upper Pleistocene (last glacial) fluvial records and the first finer grained intercalated horizon. It is also found that periods of aggradation were frequently interrupted by phases of erosion most likely triggered by periods of increased tectonic activity and climatic impact. Using the IR-RF technique it was possible to date up to w 640 ka. FLUVIAL SEDIMENTATION AND HYDROLOGIC RESPONSE TO HOLOCENE ENVIRONMENTAL CHANGE IN THE LOW MARNE VALLEY (PARIS BASIN, FRANCE) Yann Le Jeune. CNRS, UMR 8591, Laboratoire de Géographie Physique, France E-mail address: [email protected]
Within the last twenty years many multidisciplinary studies have been initiated in the low valley of Marne to understand the relationships between alluvial stratigraphy, climate variability and environmental changes through time. Our results have shown connections and differences between morphosedimentary responses and paleoenvironmental recordings. The alluvial deposits have been divided into sequences and an overall chrono-typology and paleohydrological synthesis was build from various sites in the valley. At the beginning of the Holocene prior to 9650 BP, a strong river incision has occurred. During the Preboreal and the Boreal phases, the river level has risen slowly. Organic deposits have been left on the bank while laminated calcareous muds were deposited in deeper waters. Palynological datas show low and local impact of the mesolithics on the environment. The Atlantic phase is represented by calcareous tufa (oncoliths) and organic deposits. During the second part of that phase, the river rose to a level that permits the re-use of late glacial oxbows. Pollen data show the development of agricultural activities during the early Neolithic whereas no silt sedimentation can be found in the floodplain. The end of Atlantic and the first part of the Subboreal show organic infillings. During this period of time, pollen data argue in favour of
Abstracts / Quaternary International 279-280 (2012) 233–345
Laminated sediments from the proglacial lake Hvítárvatn (422 m asl) are used to construct a continuous record of environmental change and the activity of Langjökull for the past 10.2 ka. Lake sediment cores were collected from multiple locations using the DOSECC GLAD-200 core rig, and the position of the Saksunarvatn tephra layer (ca. 10.2 ka) at a depth of w18 m, confirms that the cores span the Holocene. Sedimentological analysis and tephrochronology verify the presence of clastic annual varves, and an age model is constructed by splicing a varve chronology of the past 3 ka with a tephra-constrained, paleomagnetic secular variation derived chronology for older sediments. Multiple proxies, including sedimentation rate, bulk density, IRD, TOC, C:N, 13C, and BSi, evaluated at high resolution (annual to multi-decadal) reveal a dynamic Holocene terrestrial climate. The proxy data indicate that, following regional deglaciation of the main Iceland ice sheet, glacial ice had either disappeared from the basin entirely, or was contributing an insignificant volume of sediment to the lake. A pronounced increase in sedimentation rate, sediment density, C:N, and TOC between 8.5 and 8.0 ka suggest cold summers with glacier growth and/ or landscape destabilization within the catchment. Subsequently, Holocene thermal maximum (HTM) conditions were achieved, resulting in high within-lake productivity and little/no glacier ice in the watershed. Neoglaciation is recorded as a broad trend toward cooler summers and the regrowth and expansion of Langjökull that began by ca. 6 ka, with a notable increase in ice-cap size and landscape instability at 4.2 ka. The past millennium is characterized by the abrupt onset of sustained cold periods at ca. 550 and 1250 AD, separated by an interval of relative warmth from ca. 950 to 1150 AD. The greatest Holocene extent of Langjökull occurred in the nineteenth century and is coincident with peak landscape instability. WEICHSELIAN GLACIATION IN ESTONIA Katrin Lasberg. University of Tartu, Institute of Ecology and Eart, Estonia E-mail address: [email protected]
Knowledge of the chronology and palaeogeography of the Weichselian Glaciation in Estonia has developed considerably and has been supported by new chronological, biostratigraphical and palaeogeographical data. Both marine and continental Eemian interglacial deposits are present in Estonia and pollen assemblages indicate that the entire Eemian vegetation cycle is present in the sediments. Recent OSL ages from Weichselian Stage lacustrine and stream sediments indicate that Estonia was ice-free at least between 115 – 68 ka and 44 – 27 ka ago which leaves 24 ka (68 – 44 ka) for a possible early Middle Weichselian glaciation. The beginning of the Late Weichselian glaciation in Estonia has not been directly dated but the available data from Eastern Finland and Western Latvia suggest that the onset may have occurred ca 22 ka ago. The last deglaciation of Estonia from the oldest, the Haanja (North Lithuanian, Luga) ice-marginal zone, to the recession of ice from the youngest, the Palivere zone, took place between ca 14.7 - 12.7 ka or between 14 675 – 12 675 varve years ago. The mean annual rate of ice recession in Estonia from the Haanja to the Palivere icemarginal zone is calculated to be ca 110 m/year. As the onset of the Late Weichselian glaciation in Estonia occurred no earlier than 22 ka ago, and the ice retreated from the Palivere zone at 12.7 ka, the maximum duration of the Late Weichselian glaciation in Estonia was ca 9.3 ka. ARCHAEOLOGICAL AND PALEOENVIRONMENTAL EVIDENCE FOR A LATE PLEISTOCENE HUMAN SETTLEMENT IN THE HYPERARID CORE OF THE ATACAMA DESERT (21 S) Claudio Latorre. CASEB, Universidad Catolica de Chile, Chile E-mail address: [email protected]
The antiquity and radiocarbon chronology of the first human settlements of South America is one of the most widely debated topics in American archaeology. Issues include points of entry, dispersal mechanisms and the process of initial human settlement that then diversified into regional cultural processes. The immigration paths taken, including the coastal or inland routes, as well as the cultural diversity present in these early settlements are also heavily disputed. Despite evidence for the earliest occupations of South America as old as 14.6 ka, there is a notable absence of dates >11 ka along the coast of southern Peru as well as in the central Atacama. Here, we propose that extensive areas in the foreboding Atacama
Desert have been overlooked regarding their potential for harboring such early sites. Spanning over 1500 km, the hyperarid core of the Atacama Desert is truly one of the driest places on Earth. Paleoecological, stratigraphical and geomorphological evidence, however, indicate that portions of this desert contained in-stream wetlands and/or riparian woodlands between 17 to 11 ka, coeval with extensive wet phases across the central Andes. Increased summer rainfall over the regional highlands became manifest in the lower desert as increased runoff and heightened groundwater tables and the extensive aggradation of fluvial terraces covered with vegetation. Such resources would have been ideal areas for early settlements. One particular such settlement was recently uncovered by our research team at site Quebrada Mani 12 (S21.09 ; W69.43 ; 900 m). Six radiocarbon dates on charcoal excavated from one test pit containing bifaces and other lithic artifacts span from 14.5 to 11.8 ka. These ages indicate that site QM12 is perhaps one of the oldest known archaeological sites from northern Chile. Our study also reveals the vast untapped potential of this region for finding even more such early sites by linking archaeological surveys to regional paleoenvironmental change. OSL- AND INFRARED RADIOFLUORESCENCE (IR-RF) DATING OF UPPERAND MIDDLE PLEISTOCENE FLUVIAL UNITS FROM THE HEIDELBERG BASIN, SOUTHERN GERMANY Tobias Lauer. Geographisches Institut, Germany E-mail address: [email protected]
The Upper Rhine Graben (URG) hosts more than 500 m thick Quaternary fluvial and limnic-fluvial deposits. These sediments are characterised by thick gravel and sand layers which can be correlated with cold periods and by intercalated finer grained peat-rich layers representing warmer periods. In the framework of the Heidelberg Basin Drilling Project, we applied quartz optical stimulated luminescence (OSL) dating to Upper Pleistocene deposits and Infrared Radiofluorescence (IR-RF) dating using K-feldspar to Middle Pleistocene fluvial units. The aim of the present study is to provide a more reliable chronology for such sediments yielding the records of climate changes und tectonic processes. Samples were taken from two sediment cores drilled into the Heidelberg Basin infill near the city of Viernheim and at Ludwigshafen. The results show that Eemian sediments are not exposed at the study area and that there is a significant chronological gap between the Upper Pleistocene (last glacial) fluvial records and the first finer grained intercalated horizon. It is also found that periods of aggradation were frequently interrupted by phases of erosion most likely triggered by periods of increased tectonic activity and climatic impact. Using the IR-RF technique it was possible to date up to w 640 ka. FLUVIAL SEDIMENTATION AND HYDROLOGIC RESPONSE TO HOLOCENE ENVIRONMENTAL CHANGE IN THE LOW MARNE VALLEY (PARIS BASIN, FRANCE) Yann Le Jeune. CNRS, UMR 8591, Laboratoire de Géographie Physique, France E-mail address: [email protected]
Within the last twenty years many multidisciplinary studies have been initiated in the low valley of Marne to understand the relationships between alluvial stratigraphy, climate variability and environmental changes through time. Our results have shown connections and differences between morphosedimentary responses and paleoenvironmental recordings. The alluvial deposits have been divided into sequences and an overall chrono-typology and paleohydrological synthesis was build from various sites in the valley. At the beginning of the Holocene prior to 9650 BP, a strong river incision has occurred. During the Preboreal and the Boreal phases, the river level has risen slowly. Organic deposits have been left on the bank while laminated calcareous muds were deposited in deeper waters. Palynological datas show low and local impact of the mesolithics on the environment. The Atlantic phase is represented by calcareous tufa (oncoliths) and organic deposits. During the second part of that phase, the river rose to a level that permits the re-use of late glacial oxbows. Pollen data show the development of agricultural activities during the early Neolithic whereas no silt sedimentation can be found in the floodplain. The end of Atlantic and the first part of the Subboreal show organic infillings. During this period of time, pollen data argue in favour of