- Email: [email protected]
East-west gradient of temperature and environmental changes during the Weichselian Lateglacial in NW-Europe
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Abstracts / Quaternary International 279-280 (2012) 462–565
groundwaters in northern marginal part of Baltic Basin. Increased hydraulic gradients from melting of km-thick Pleistocene ice sheet reorganized regional-scale groundwater flow in sedimentaryaquifers of the northern Baltic coast. Here we present an overview of the status and origin of groundwaters in the shallowly buried marginal part of the Cambrian-Vendian (Edicaran) confined aquifer of the Baltic Basin, which is characterised by fresh and isotopically depleted d18O composition of water, whereas the deeply settled parts of the aquifer are characterized by typical Na-Ca-Cl basinal brines. Spatial variation in water geochemistry and stable isotope composition suggest mixing origin of the diluted water of three endmembers – undersaturated glacial melt water of Weichelian Ice Age, NaCa-Cl composition basin brine and modern meteoric water. In a temporal scale the mixing has occurred in two stages. First, the intrusion and mixing of depleted glacial waters with basinal brines occurred during the Pleistocene glacial periods when the subglacial melt-water with high hydraulic gradient penetrated into the aquifer. The second stage of mixing takes place today by intrusion of meteoric waters through deep valley systems that incise the protecting aquitard in northern Estonia. The freshened water at the northern margin of the basin has acquired a partial equilibrium with rock matrix of the aquifer. The Ca2+ and Mg2+ activities of water agrees with the equilibrium boundary of (sedimentary disordered) dolomite and calcite suggesting that the water has attained or is nearly in the equilibrium with these phases that are common cement minerals in Cambrian-Ediacaran sediments. HYDROSTRATIGRAPHY OF PLEISTOCENE ALLUVIAL FAN AND RIVER PLAIN DEPOSITS OF THE PO FORELAND BASIN Renzo Valloni. University of Parma, Italy E-mail address: [email protected]
In the southern active margin of the Po river foreland basin the Middle Pleistocene-Holocene basin fill is controlled by thrust faults and subsidence affecting the front of the advancing Apennines chain and by glacioeustaic climatic cycles. The extensive study of cored boreholes allowed the recognition of bipartite depositional units constituting the building elements of the basin fill. In Middle-Late Pleistocene times the stacking of these stratigraphic elements was basically controlled by tectonics modulated by climate over the astronomically driven 100 ka cycles. In the southern margin of the Po river basin these building elements average 30 m thickness and are neatly subdivided in a lower portion representing the alluvial fan gravels and an upper portion representing the overbank muds. The age constraints provided by radiocarbon dates indicate the development of coalescent alluvial fans in cold climatic phases, destined to become aquifers, and the aggradation of the alluvial plain in warm climatic phases, with river-channel avulsion and overbank sedimentation forming the laterally continuous fine-grained deposits destined to become permeability barriers. Aggradation during interglacials is of the utmost importance to hydrostratigraphy since river channels build up topographically elevated alluvial ridges causing river avulsion and the ultimate draping of aquifer bodies by a laterally continuous confining layer. THE IMPACT OF TEMPERATURE CHANGES ON THE VEGETATION DEVELOPMENT IN IRELAND DURING THE WEICHSELIAN LATEGLACIAL Nelleke Van Asch. Department of Physical Geography, Utrecht University, Netherlands E-mail address: [email protected]
A lacustrine carbonate record from western Ireland has been studied to reconstruct climatic and environmental changes during the Weichselian Lateglacial (14.7-11.7 ka cal BP). Climate is reconstructed based on a combination of lithology, oxygen isotopes and chironomids, while the vegetation development is reconstructed by means of pollen analysis. These proxies indicate that warm conditions prevailed during the Interstadial, followed by a strong temperature decline at the transition to the Younger Dryas. This prolonged cold period is succeeded by rapid warming at the onset of the Holocene. A summer temperature decline of 6-7 degrees during the Younger Dryas is inferred from the chironomid record. This temperature decline led to an expansion of tundra vegetation throughout Ireland.
In more detail, the available proxies show that at least two distinct cold events occurred during the Interstadial, which have been correlated to Greenland Interstadial 1b and 1d. The first oscillation (GI-1d) seems to have been the most severe in Ireland. Comparison with the pollen record shows that both cold events led to a temporary opening of the vegetation cover, predominantly as a decline in woody vegetation (Juniperus and Betula). It appears the first oscillation had the most distinct effect on the vegetation, mainly because woody vegetation was more abundant in Ireland during that phase. THE YOUNGER DRYAS COOLING IN NE-GERMANY: MULTI-PROXY RECONSTRUCTION OF TEMPERATURE AND VEGETATION CHANGES Nelleke Van Asch. Department of Physical Geography, Utrecht University, Netherlands E-mail address: [email protected]
Multi-proxy analyses were carried out on a lacustrine carbonate sediment record from NE-Germany to reconstruct summer temperature and associated environmental changes during the Younger Dryas. The record encompasses the Allerød to early Holocene, and is analysed for lithology, oxygen and carbon isotopes, pollen and chironomids. The Allerød and Younger Dryas deposits reach an exceptional thickness of w5 m in the examined sequence. Multiple occurrences of the presumed Laacher See Tephra in the later part of the Allerød section indicate the record may have been influenced by reworking and redeposition. The chironomid record indicates warm conditions during the first part of the record. The vegetation, inferred from pollen assemblages, consisted of mixed birch-pine forest, which developed into a pine dominated forest. During the Younger Dryas, cold water chironomids expanded and carbonate precipitation decreased. Furthermore, the pine forests became more open, and erosion led to the input of sand into the basin. At the transition to the Holocene, both the oxygen isotope record and the chironomid record indicate a rapid shift to warm conditions. As a result of climatic warming, lake marl formation resumed and closed forests re-established. The application of a chironomid-temperature transfer function results in a quantitative reconstruction of changes in summer temperature associated with the onset and termination of the Younger Dryas. EAST-WEST GRADIENT OF TEMPERATURE AND ENVIRONMENTAL CHANGES DURING THE WEICHSELIAN LATEGLACIAL IN NW-EUROPE Nelleke Van Asch. Department of Physical Geography, Utrecht University, Netherlands E-mail address: [email protected]
The Weichselian Lateglacial (14.7-11.7 ka cal BP) is marked by rapid climatic changes in the North Atlantic region. In addition to the Greenland Stadial 1 (or Younger Dryas), at least two centennial-scale cold events, GI1b and GI-1d, occurred during the Lateglacial. These cold events are thought to originate from meltwater pulses into the Atlantic Ocean, which led to changes in the North Atlantic thermohaline circulation. It is therefore expected that temperature changes were most pronounced at sites close to the Atlantic Ocean. Understanding how these changes propagated further inland will provide insights into the influence of the Atlantic Ocean on European climate and associated environmental changes. For that reason, multiple lacustrine carbonate records along a west-east transect through NW-Europe were studied. Records from Ireland, the Netherlands and Germany were analysed for lithology, oxygen isotopes, pollen and chironomids. These records enable identification of spatial patterns in temperature and associated environmental changes. Results indicate a west-east decrease in the magnitude of summer temperature changes during the Lateglacial period. Environmental changes associated with cold oscillations during the Lateglacial appeared to be most pronounced in Ireland. PEOPLE, PREY AND PREDATORS: COMMUNITY DYNAMICS AND CLIMATIC PROCESSES IN THE LAST INTERGLACIAL Eline N. van Asperen. Liverpool John Moores University, United Kingdom E-mail address: [email protected]
Abstracts / Quaternary International 279-280 (2012) 462–565
groundwaters in northern marginal part of Baltic Basin. Increased hydraulic gradients from melting of km-thick Pleistocene ice sheet reorganized regional-scale groundwater flow in sedimentaryaquifers of the northern Baltic coast. Here we present an overview of the status and origin of groundwaters in the shallowly buried marginal part of the Cambrian-Vendian (Edicaran) confined aquifer of the Baltic Basin, which is characterised by fresh and isotopically depleted d18O composition of water, whereas the deeply settled parts of the aquifer are characterized by typical Na-Ca-Cl basinal brines. Spatial variation in water geochemistry and stable isotope composition suggest mixing origin of the diluted water of three endmembers – undersaturated glacial melt water of Weichelian Ice Age, NaCa-Cl composition basin brine and modern meteoric water. In a temporal scale the mixing has occurred in two stages. First, the intrusion and mixing of depleted glacial waters with basinal brines occurred during the Pleistocene glacial periods when the subglacial melt-water with high hydraulic gradient penetrated into the aquifer. The second stage of mixing takes place today by intrusion of meteoric waters through deep valley systems that incise the protecting aquitard in northern Estonia. The freshened water at the northern margin of the basin has acquired a partial equilibrium with rock matrix of the aquifer. The Ca2+ and Mg2+ activities of water agrees with the equilibrium boundary of (sedimentary disordered) dolomite and calcite suggesting that the water has attained or is nearly in the equilibrium with these phases that are common cement minerals in Cambrian-Ediacaran sediments. HYDROSTRATIGRAPHY OF PLEISTOCENE ALLUVIAL FAN AND RIVER PLAIN DEPOSITS OF THE PO FORELAND BASIN Renzo Valloni. University of Parma, Italy E-mail address: [email protected]
In the southern active margin of the Po river foreland basin the Middle Pleistocene-Holocene basin fill is controlled by thrust faults and subsidence affecting the front of the advancing Apennines chain and by glacioeustaic climatic cycles. The extensive study of cored boreholes allowed the recognition of bipartite depositional units constituting the building elements of the basin fill. In Middle-Late Pleistocene times the stacking of these stratigraphic elements was basically controlled by tectonics modulated by climate over the astronomically driven 100 ka cycles. In the southern margin of the Po river basin these building elements average 30 m thickness and are neatly subdivided in a lower portion representing the alluvial fan gravels and an upper portion representing the overbank muds. The age constraints provided by radiocarbon dates indicate the development of coalescent alluvial fans in cold climatic phases, destined to become aquifers, and the aggradation of the alluvial plain in warm climatic phases, with river-channel avulsion and overbank sedimentation forming the laterally continuous fine-grained deposits destined to become permeability barriers. Aggradation during interglacials is of the utmost importance to hydrostratigraphy since river channels build up topographically elevated alluvial ridges causing river avulsion and the ultimate draping of aquifer bodies by a laterally continuous confining layer. THE IMPACT OF TEMPERATURE CHANGES ON THE VEGETATION DEVELOPMENT IN IRELAND DURING THE WEICHSELIAN LATEGLACIAL Nelleke Van Asch. Department of Physical Geography, Utrecht University, Netherlands E-mail address: [email protected]
A lacustrine carbonate record from western Ireland has been studied to reconstruct climatic and environmental changes during the Weichselian Lateglacial (14.7-11.7 ka cal BP). Climate is reconstructed based on a combination of lithology, oxygen isotopes and chironomids, while the vegetation development is reconstructed by means of pollen analysis. These proxies indicate that warm conditions prevailed during the Interstadial, followed by a strong temperature decline at the transition to the Younger Dryas. This prolonged cold period is succeeded by rapid warming at the onset of the Holocene. A summer temperature decline of 6-7 degrees during the Younger Dryas is inferred from the chironomid record. This temperature decline led to an expansion of tundra vegetation throughout Ireland.
In more detail, the available proxies show that at least two distinct cold events occurred during the Interstadial, which have been correlated to Greenland Interstadial 1b and 1d. The first oscillation (GI-1d) seems to have been the most severe in Ireland. Comparison with the pollen record shows that both cold events led to a temporary opening of the vegetation cover, predominantly as a decline in woody vegetation (Juniperus and Betula). It appears the first oscillation had the most distinct effect on the vegetation, mainly because woody vegetation was more abundant in Ireland during that phase. THE YOUNGER DRYAS COOLING IN NE-GERMANY: MULTI-PROXY RECONSTRUCTION OF TEMPERATURE AND VEGETATION CHANGES Nelleke Van Asch. Department of Physical Geography, Utrecht University, Netherlands E-mail address: [email protected]
Multi-proxy analyses were carried out on a lacustrine carbonate sediment record from NE-Germany to reconstruct summer temperature and associated environmental changes during the Younger Dryas. The record encompasses the Allerød to early Holocene, and is analysed for lithology, oxygen and carbon isotopes, pollen and chironomids. The Allerød and Younger Dryas deposits reach an exceptional thickness of w5 m in the examined sequence. Multiple occurrences of the presumed Laacher See Tephra in the later part of the Allerød section indicate the record may have been influenced by reworking and redeposition. The chironomid record indicates warm conditions during the first part of the record. The vegetation, inferred from pollen assemblages, consisted of mixed birch-pine forest, which developed into a pine dominated forest. During the Younger Dryas, cold water chironomids expanded and carbonate precipitation decreased. Furthermore, the pine forests became more open, and erosion led to the input of sand into the basin. At the transition to the Holocene, both the oxygen isotope record and the chironomid record indicate a rapid shift to warm conditions. As a result of climatic warming, lake marl formation resumed and closed forests re-established. The application of a chironomid-temperature transfer function results in a quantitative reconstruction of changes in summer temperature associated with the onset and termination of the Younger Dryas. EAST-WEST GRADIENT OF TEMPERATURE AND ENVIRONMENTAL CHANGES DURING THE WEICHSELIAN LATEGLACIAL IN NW-EUROPE Nelleke Van Asch. Department of Physical Geography, Utrecht University, Netherlands E-mail address: [email protected]
The Weichselian Lateglacial (14.7-11.7 ka cal BP) is marked by rapid climatic changes in the North Atlantic region. In addition to the Greenland Stadial 1 (or Younger Dryas), at least two centennial-scale cold events, GI1b and GI-1d, occurred during the Lateglacial. These cold events are thought to originate from meltwater pulses into the Atlantic Ocean, which led to changes in the North Atlantic thermohaline circulation. It is therefore expected that temperature changes were most pronounced at sites close to the Atlantic Ocean. Understanding how these changes propagated further inland will provide insights into the influence of the Atlantic Ocean on European climate and associated environmental changes. For that reason, multiple lacustrine carbonate records along a west-east transect through NW-Europe were studied. Records from Ireland, the Netherlands and Germany were analysed for lithology, oxygen isotopes, pollen and chironomids. These records enable identification of spatial patterns in temperature and associated environmental changes. Results indicate a west-east decrease in the magnitude of summer temperature changes during the Lateglacial period. Environmental changes associated with cold oscillations during the Lateglacial appeared to be most pronounced in Ireland. PEOPLE, PREY AND PREDATORS: COMMUNITY DYNAMICS AND CLIMATIC PROCESSES IN THE LAST INTERGLACIAL Eline N. van Asperen. Liverpool John Moores University, United Kingdom E-mail address: [email protected]