- Email: [email protected]
Evidence for pre-Holocene humid phases from lacustrine deposits on the Arabian Peninsula
412
Abstracts / Quaternary International 279-280 (2012) 346–461
geomorphology, micromorphology, archaeology and palaeobotany allow a detailed interpretation of individual anthropogenic fire activities. The results will be compared with archaeological and palynological data including microscopic charcoal inferred fire history which detect several distinct settlement phases from Early Bronze Age (18/17th c. BC) till the beginning of the High Middle Ages (Krause 2007).This research was applied within the interdisciplinary project “The History of Mining Activities in the Tyrol and Adjacent Areas - Impact on Environment & Human Societies” (HiMAT) between Archaeologists and Geoarchaeologists (Frankfurt), Archaeobotanists (Innsbruck) and Archaeometallurgists (Tübingen) to investigate the colonization of the valley and to reconstruct human-environment interactions. ‘POSTGLACIAL PALAEOENVIRONMENTAL EVOLUTION AND SEDIMEN TATION IN THE CONTINENTAL SHELF OFF THE GUADIANA RIVER (SW IBERIA)’ Francisca Rosa. CIMA/University of Algarve, Portugal
Atlantic, the so-called Benguela Niños. At present these events are represented by intermittent southward flows of warm water. These episodes are in many respects similar to the El Niño phenomena of the South-East Pacific Ocean, but do not seem to be synchronized with them. They therefore have been assumed to have different forcing factors. Their occurrence has catastrophic effects on the local marine ecosystem as well as on regional rainfall. We show however that in parallel to the Pacific, in the South Atlantic the onset of the modern BUS probably meant the cessation of Benguela El Niño-like conditions during the early Pleistocene and Pliocene. NEW INSIGHTS ON THE PHASING OF ATMOSPHERIC METHANE AND TEMPERATURE CHANGE DURING THE BØLLING TRANSITION FROM THE NORTH GREENLAND EEMIAN (NEEM) ICE CORE Julia Rosen. Department of Geosciences, Oregon State University, United States E-mail address: [email protected]
E-mail address: [email protected]
Continental shelf sedimentary sequences result from the interaction between continental and marine processes, making them highly susceptible to environmental changes. The continental shelf deposits off Guadiana River were formed under influence of the postglacial sea-level rise, in a transitional coastal-to-shelf setting. They have been controlled by Holocene climatic variability and human impact in the region. The Guadiana river discharges have been the main sediment source to the coast and adjacent shelf, with fines dominating the total amount of river supply. Present-day dispersal patterns indicate that fluvial-transported bedload sediments (sand) deposit mainly in the inner shelf, close to the river mouth. Re-suspended fines accumulate in deeper and less hydrodynamic areas of the middle shelf, where they have formed an important mud body. Five vibrocores collected in the Guadiana shelf (middle shelf mud body and inner shelf west of the river mouth) were set for sedimentary analysis (grain-size, coarse-grained/sand sediment components, quartz shape and morphoscopy) to reconstruct the drowning history and depositional evolution of the shelf. Radiocarbon dating indicated ages of ca. 15 000 cal. years B.P. for the oldest core sediments. Some of the older deposits of the mud patch cores contain specific terrigenous components and quartz grain features currently occurring in inner shelf areas under direct influence of the Guadiana River bedload discharges. They seem to have deposited in this area of the middle shelf when sea level was lower than today and the river drainage extended to actual drowned areas of the shelf. Important depositional changes are evident ca. 5000 cal. years B.P., with enhanced fine deposition and increasing bioclasts pointing to a more stable marine domain established after sea-level stabilization. At ca. 1000 cal. years B.P. fines dominate deposition, generating the mud patch enriched in benthic foraminifera and mollusks in the middle shelf. PERSISTENT BENGUELA EL-NIÑO LIKE CONDITIONS DURING THE PLIOCENE-PLEISTOCENE?
The phasing of changes in temperature, precipitation, and other environmental variables between different regions of the globe during the abrupt climate transitions of the last glacial period provides a valuable constraint on the possible mechanisms that drive such changes. However, determining precise temporal relationships between records remains a challenge in paleoclimate research. In some cases, this difficulty can be overcome when multiple variables recorded in the same paleoclimate record reflect geographically distinct processes. We apply such an approach to new, very high-resolution measurements of gases from the North Greenland Eemian (NEEM) ice core across the Bølling Transition (14.67 ky BP). We capitalize on the fact that changes in atmospheric methane, a gas with widely distributed sources, can be compared with the isotopic composition of atmospheric nitrogen, a proxy for local temperature change and climate-dependent firn properties, with essentially no relative age uncertainty (Severinghaus et al., 1998; Severinghaus and Brook, 1999). Our data include 95 methane measurements made at Oregon State University and 110 measurements of d15N made at the Scripps Institution of Oceanography, University of California, San Diego. Both records are sampled at less than 15 cm (w10 year) resolution over a 13 m interval encompassing the entire transition. The isotope record is augmented by eleven additional measurements at 5 cm increments over the first 40 years of the transition. By comparing the onset of d15N enrichment with atmospheric CH4 concentrations, we find that the increase in methane at the Bølling onset is synchronous with warming at the NEEM site. Interpretation of the record is complicated by short-term reversals in the isotopic trends that may be due to firn processes, for example fluctuations in the depth at which the atmospheric signal is trapped. Modeling to investigate such effects is underway. EVIDENCE FOR PRE-HOLOCENE HUMID PHASES FROM LACUSTRINE DEPOSITS ON THE ARABIAN PENINSULA Thomas M. Rosenberg. University of Bern, Switzerland
Antoni Rosell-Melé. Autonomous University of Barcelona, Spain
E-mail address: [email protected]
E-mail address: [email protected]
The transition between the Pliocene and Pleistocene epochs is marked by a shift toward a globally cooler state, the development of extensive bipolar glaciations, and the strengthening of ocean-atmosphere circulation systems. In the relative warmth of the Pliocene epoch, global ice volume was largely contained in the Antarctic ice-sheet, the thermohaline circulation system was relatively strong, and the tropical Pacific had a weak ‘El Nino’-like Walker circulation system. A comparison of a suite of records from the tropics, subtropics and high latitudes has highlighted the possibility that the Pliocene-Pleistocene transition was not a simple, globally synchronous series of events. To provide new perspectives on the southern Atlantic response to the Pliocene-Pleistocene and impacts on the climate of South Africa, we examine the Benguela upwelling system (BUS) over the last 3 Myrs and draw parallelisms with the events described for the Pacific related to the onset of the modern cold tongue and the cessation of permanent El Niño-like conditions, and their possible analogs in the
One of the greatest mysteries in prehistory is how and when modern humans (Homo sapiens) moved out of Africa and spread over the planet. Regardless whether modern humans took the southern route across the Bab al Mandab Strait to Arabia or followed the northern route across the Sinai Peninsula, favorable environmental conditions providing enough fresh water and food must have been a key factor allowing or limiting migration. However, so far it has been difficult to take account of in the discussion about when and where human dispersal took place, primarily due to a lack of paleo-environmental data. We revisited the remains of fossil lake deposit in the western part of the Rub al-Khali in SW Saudi Arabia, originally investigated by McClure (McClure 1976; McClure 1984) and Whitney (Whitney 1983a; Whitney et al., 1983b) in the Al-Mundafan and the Al-Khuyejmah region. The deposits have been dated using radiocarbon and optically stimulated luminescence (OSL). Environmental conditions during lake formation were reconstructed using faunal remains and geomorphologic evidence.
Abstracts / Quaternary International 279-280 (2012) 346–461
OSL dating revealed humid phases during the last interglacial (MIS 5e), around 100 ka (MIS 5c), just after ca. 80 ka (MIS 5a) and during part of the Holocene (ca. 9’600-7’800 years ago). None of our OSL ages support the previously declared humid phase between 35 and 20 ka, which was dated using radiocarbon on carbonate of the same deposits. Our OSL dates are the first firm evidence for substantial lake formation in Arabia during the early part of the Late Pleistocene. The paleo-environmental information indicates large bodies of fresh water, probably surrounded by savannah-like vegetation, as has been reconstructed for the Holocene. The periods of relatively favorable environmental conditions indentified here concur with the time frame when human migration out of Africa must have occurred. It is therefore clear that the Arabian Peninsula was not acting as a permanent natural barrier for human dispersal.
SUBMERGED STONE AGE SETTLEMENTS AND POSTGLACIAL DEVE LOPMENT OF THE BALTIC SEA IN SOUTHWEST ESTONIA Alar Rosentau. Department of Geology, University of Tartu, Estonia E-mail address: [email protected]
Southwestern Estonia in the eastern coast of Gulf of Riga is characterized by slow post-glacial isostatic uplift (about 1mm/yr) and slowly undulating low topography. Therefore even small increases in sea-level can easily lead to the flooding of substantial areas. The complex deglaciation history of the Baltic Sea area, with up-dammed lakes and early phases of post-glacial seas has, at times, left southwestern Estonia submerged, while at other times, it emerged as terrestrial land. Therefore, transgressive deposition of water-laid sediments of the Ancylus Lake and the Litorina Sea have lead to repeated burial of soil, peat and gyttja deposits and associated settlement layers. The authors combined geological, geodetic and archaeological shore displacement evidence to create a temporal and spatial water-level change model for the SW Estonian coast of the Baltic Sea to examine the relationships between coastline change and submerged Stone Age settlements including the oldest Estonia human occupation in Pulli (10.8-10.2 cal. ka BP). The Baltic Sea shoreline database for Estonian territory was used for the modeling work and contained about 1200 sites from the Baltic Ice Lake, Ancylus Lake and Litorina Sea stages. This database was combined with a compiled shore displacement curve. The curve was reconstructed on the basis of palaeocoastline elevations and radiocarbon dated peat and soil sequences and ecofacts from archeological sites recording three regressive phases of the past Baltic Sea, interrupted by Ancylus Lake (ca 10.8-10.2 cal ka BP) and Litorina Sea (ca 8.5-7.3 cal ka BP) transgressions with magnitudes of 12 m and 10 m, respectively. A water-level change model was applied together with a digital terrain model for reconstruction of coastline development during the Ancylus Lake and Litorina Sea stages in order to understand the preferences of habitation of Stone Age people in the region. PALAEOGEOGRAPHIC RECONSTRUCTION OF THE BALTIC ICE LAKE IN THE EASTERN BALTIC Alar Rosenta. Department of Geology, University of Tartu, Estonia E-mail address: [email protected]
A GIS-based palaeogeographic reconstruction of the development of the Baltic Ice Lake (BIL) in the eastern Baltic during the deglaciation of the Scandinavian Ice Sheet is presented in this study. A Late Glacial shoreline database containing more than 1000 sites from Finland, NW Russia, Estonia, Latvia and modern digital terrain models were used for palaeoreconstructions. The BIL occupied five different levels, represented by 492 shoreline features. The study shows that at about 13.3 cal. ka BP the BIL extended to the ice-free areas of Latvia, Estonia and NW Russia, represented by the highest shoreline in this region. Reconstructions demonstrate that BIL initially had the same water level as the Glacial Lakes Peipsi and Võrtsjärv, because these water bodies were connected via strait systems in central Estonia. These strait systems were closed at about 12.8–11.7 cal. ka BP prior to the final drainage of the BIL due to isostatic uplift. Glacial Lake Võrtsjärv was isolated from the BIL at about 12.4–12.0 cal. ka BP. Exact timing of Glacial Lake Peipsi isolation is not
413
clear, but according to the altitude of the threshold in northeast Estonia and shore displacement data it was completed at about 12.4–11.7 cal. ka BP (Rosentau et al., 2009). DEVELOPMENT OF THE LITTORINA SEA AND ITS RELATIONS WITH NEOLITHIC HUMAN OCCUPATIONS IN NARVA-LUGA KLINT BAY AREA IN THE EASTERN BALTIC SEA Alar Rosentau. Department of Geology, University of Tartu, Estonia E-mail address: [email protected]
The published and new shore displacement evidences from NW Russia and NE Estonia were used to reconstruct past sea-level changes of the Baltic Sea in the Narva-Luga Klint Bay area. For the sea-level reconstruction the Littorina Sea coastal landform elevations and shore displacement data from six uplifted lake basins were used. Reconstructed shore displacement curve displays the Littorina Sea transgression with magnitude of 8 m at about 8.5-7.5 cal ka BP and its later regression. Due to the uneven glacioisostatic land-uplift the highest coastal landforms of the Littorina Sea are locating at altitude of 14 m a.s.l. in the north and 6 m a.s.l. in the southern part of the Klint Bay area. After 7.5 cal ka BP the relative sea level rise was turned to the sea level fall as the eustatic sea level rise was slowed down and the land-uplift started to prevail. Spatial and temporal paleogeographic model was developed for the Narva-Luga Klint Bay area using the shore displacement curve and the land-uplift data and digital terrain model. This model was used to investigate relationships between shore displacement and displacement of Neolithic human occupations in our study area. Comparison of settlement sites locations with paleogeographic reconstructions show that Littorina Sea lagoon shores were the most preferred living environments for Neolithic human occupations during the period between ca 7.1-6.0 cal ka BP. Later, due to the ongoing regression of the Littorina Sea, the lagoon was gradually isolated from the sea, forming several small lakes which finally turned into mires. Overgrowing of lagoon made the people abandon their traditional coastal settlement sites and forced them to find new suitable living environments. Thus at the end of the Neolithic period and at the beginning of the Early Metal Age the settlement sites were mostly concentrated along the ancient rivers in the Narva-Luga Klint Bay area.
LATE PLEISTOCENE - HOLOCENE IN ALTO RIBATEJO (WESTERN IBERIA), DEPOSITS AND PALEOENVIRONMENT CHANGES Pierluigi Rosina. Instituto Politécncico de Tomar, Quaternary and Pr, Portugal E-mail address: [email protected]
The Alto Ribatejo region (central Portugal) is under the influence of both Mediterranean and Atlantic climatic conditions. In the region, the Tagus River flows across three geological and geomorphological units: the Hesperic massif (Pre-Cambrian and Paleozoic metamorphic basement), a Mesozoic limestone massif, and a Cenozoic sedimentary basin. So, in this relatively small area (2,500 Km2), the landscape is quite diversified. The regional Quaternary deposits are represented by: a) the Holocene alluvial sediments, b) the Pleistocene wide fluvial terraces, c) the karstic cave fillings (in limestone massif), d) Aeolian sediments and e) the detritical coverings (colluviums). Sedimentological analysis, performed mostly in deposits associated with archaeological sites documenting the last w25,000 years, show the influence of climatic variations and of anthropic activities. Archaeobotanic remains show that during the Holocene a spread of shrubs in relation to the arborean vegetation, with decrease of oaks and pines woodlands, occurred. Holocene climatic oscillations and the human influence on the landscape, particularly the adoption of agro-pastoralism subsistence system, could be responsible for this evolution. Available data on cerealia and graminacea pollens point out for an increasing human impact on the landscape during the Holocene. First anthropic markers are dating back to 6,000 BC. Paleontological remains were found only in anthropic contexts, showing relationship between hunting activities and pastoralism
Abstracts / Quaternary International 279-280 (2012) 346–461
geomorphology, micromorphology, archaeology and palaeobotany allow a detailed interpretation of individual anthropogenic fire activities. The results will be compared with archaeological and palynological data including microscopic charcoal inferred fire history which detect several distinct settlement phases from Early Bronze Age (18/17th c. BC) till the beginning of the High Middle Ages (Krause 2007).This research was applied within the interdisciplinary project “The History of Mining Activities in the Tyrol and Adjacent Areas - Impact on Environment & Human Societies” (HiMAT) between Archaeologists and Geoarchaeologists (Frankfurt), Archaeobotanists (Innsbruck) and Archaeometallurgists (Tübingen) to investigate the colonization of the valley and to reconstruct human-environment interactions. ‘POSTGLACIAL PALAEOENVIRONMENTAL EVOLUTION AND SEDIMEN TATION IN THE CONTINENTAL SHELF OFF THE GUADIANA RIVER (SW IBERIA)’ Francisca Rosa. CIMA/University of Algarve, Portugal
Atlantic, the so-called Benguela Niños. At present these events are represented by intermittent southward flows of warm water. These episodes are in many respects similar to the El Niño phenomena of the South-East Pacific Ocean, but do not seem to be synchronized with them. They therefore have been assumed to have different forcing factors. Their occurrence has catastrophic effects on the local marine ecosystem as well as on regional rainfall. We show however that in parallel to the Pacific, in the South Atlantic the onset of the modern BUS probably meant the cessation of Benguela El Niño-like conditions during the early Pleistocene and Pliocene. NEW INSIGHTS ON THE PHASING OF ATMOSPHERIC METHANE AND TEMPERATURE CHANGE DURING THE BØLLING TRANSITION FROM THE NORTH GREENLAND EEMIAN (NEEM) ICE CORE Julia Rosen. Department of Geosciences, Oregon State University, United States E-mail address: [email protected]
E-mail address: [email protected]
Continental shelf sedimentary sequences result from the interaction between continental and marine processes, making them highly susceptible to environmental changes. The continental shelf deposits off Guadiana River were formed under influence of the postglacial sea-level rise, in a transitional coastal-to-shelf setting. They have been controlled by Holocene climatic variability and human impact in the region. The Guadiana river discharges have been the main sediment source to the coast and adjacent shelf, with fines dominating the total amount of river supply. Present-day dispersal patterns indicate that fluvial-transported bedload sediments (sand) deposit mainly in the inner shelf, close to the river mouth. Re-suspended fines accumulate in deeper and less hydrodynamic areas of the middle shelf, where they have formed an important mud body. Five vibrocores collected in the Guadiana shelf (middle shelf mud body and inner shelf west of the river mouth) were set for sedimentary analysis (grain-size, coarse-grained/sand sediment components, quartz shape and morphoscopy) to reconstruct the drowning history and depositional evolution of the shelf. Radiocarbon dating indicated ages of ca. 15 000 cal. years B.P. for the oldest core sediments. Some of the older deposits of the mud patch cores contain specific terrigenous components and quartz grain features currently occurring in inner shelf areas under direct influence of the Guadiana River bedload discharges. They seem to have deposited in this area of the middle shelf when sea level was lower than today and the river drainage extended to actual drowned areas of the shelf. Important depositional changes are evident ca. 5000 cal. years B.P., with enhanced fine deposition and increasing bioclasts pointing to a more stable marine domain established after sea-level stabilization. At ca. 1000 cal. years B.P. fines dominate deposition, generating the mud patch enriched in benthic foraminifera and mollusks in the middle shelf. PERSISTENT BENGUELA EL-NIÑO LIKE CONDITIONS DURING THE PLIOCENE-PLEISTOCENE?
The phasing of changes in temperature, precipitation, and other environmental variables between different regions of the globe during the abrupt climate transitions of the last glacial period provides a valuable constraint on the possible mechanisms that drive such changes. However, determining precise temporal relationships between records remains a challenge in paleoclimate research. In some cases, this difficulty can be overcome when multiple variables recorded in the same paleoclimate record reflect geographically distinct processes. We apply such an approach to new, very high-resolution measurements of gases from the North Greenland Eemian (NEEM) ice core across the Bølling Transition (14.67 ky BP). We capitalize on the fact that changes in atmospheric methane, a gas with widely distributed sources, can be compared with the isotopic composition of atmospheric nitrogen, a proxy for local temperature change and climate-dependent firn properties, with essentially no relative age uncertainty (Severinghaus et al., 1998; Severinghaus and Brook, 1999). Our data include 95 methane measurements made at Oregon State University and 110 measurements of d15N made at the Scripps Institution of Oceanography, University of California, San Diego. Both records are sampled at less than 15 cm (w10 year) resolution over a 13 m interval encompassing the entire transition. The isotope record is augmented by eleven additional measurements at 5 cm increments over the first 40 years of the transition. By comparing the onset of d15N enrichment with atmospheric CH4 concentrations, we find that the increase in methane at the Bølling onset is synchronous with warming at the NEEM site. Interpretation of the record is complicated by short-term reversals in the isotopic trends that may be due to firn processes, for example fluctuations in the depth at which the atmospheric signal is trapped. Modeling to investigate such effects is underway. EVIDENCE FOR PRE-HOLOCENE HUMID PHASES FROM LACUSTRINE DEPOSITS ON THE ARABIAN PENINSULA Thomas M. Rosenberg. University of Bern, Switzerland
Antoni Rosell-Melé. Autonomous University of Barcelona, Spain
E-mail address: [email protected]
E-mail address: [email protected]
The transition between the Pliocene and Pleistocene epochs is marked by a shift toward a globally cooler state, the development of extensive bipolar glaciations, and the strengthening of ocean-atmosphere circulation systems. In the relative warmth of the Pliocene epoch, global ice volume was largely contained in the Antarctic ice-sheet, the thermohaline circulation system was relatively strong, and the tropical Pacific had a weak ‘El Nino’-like Walker circulation system. A comparison of a suite of records from the tropics, subtropics and high latitudes has highlighted the possibility that the Pliocene-Pleistocene transition was not a simple, globally synchronous series of events. To provide new perspectives on the southern Atlantic response to the Pliocene-Pleistocene and impacts on the climate of South Africa, we examine the Benguela upwelling system (BUS) over the last 3 Myrs and draw parallelisms with the events described for the Pacific related to the onset of the modern cold tongue and the cessation of permanent El Niño-like conditions, and their possible analogs in the
One of the greatest mysteries in prehistory is how and when modern humans (Homo sapiens) moved out of Africa and spread over the planet. Regardless whether modern humans took the southern route across the Bab al Mandab Strait to Arabia or followed the northern route across the Sinai Peninsula, favorable environmental conditions providing enough fresh water and food must have been a key factor allowing or limiting migration. However, so far it has been difficult to take account of in the discussion about when and where human dispersal took place, primarily due to a lack of paleo-environmental data. We revisited the remains of fossil lake deposit in the western part of the Rub al-Khali in SW Saudi Arabia, originally investigated by McClure (McClure 1976; McClure 1984) and Whitney (Whitney 1983a; Whitney et al., 1983b) in the Al-Mundafan and the Al-Khuyejmah region. The deposits have been dated using radiocarbon and optically stimulated luminescence (OSL). Environmental conditions during lake formation were reconstructed using faunal remains and geomorphologic evidence.
Abstracts / Quaternary International 279-280 (2012) 346–461
OSL dating revealed humid phases during the last interglacial (MIS 5e), around 100 ka (MIS 5c), just after ca. 80 ka (MIS 5a) and during part of the Holocene (ca. 9’600-7’800 years ago). None of our OSL ages support the previously declared humid phase between 35 and 20 ka, which was dated using radiocarbon on carbonate of the same deposits. Our OSL dates are the first firm evidence for substantial lake formation in Arabia during the early part of the Late Pleistocene. The paleo-environmental information indicates large bodies of fresh water, probably surrounded by savannah-like vegetation, as has been reconstructed for the Holocene. The periods of relatively favorable environmental conditions indentified here concur with the time frame when human migration out of Africa must have occurred. It is therefore clear that the Arabian Peninsula was not acting as a permanent natural barrier for human dispersal.
SUBMERGED STONE AGE SETTLEMENTS AND POSTGLACIAL DEVE LOPMENT OF THE BALTIC SEA IN SOUTHWEST ESTONIA Alar Rosentau. Department of Geology, University of Tartu, Estonia E-mail address: [email protected]
Southwestern Estonia in the eastern coast of Gulf of Riga is characterized by slow post-glacial isostatic uplift (about 1mm/yr) and slowly undulating low topography. Therefore even small increases in sea-level can easily lead to the flooding of substantial areas. The complex deglaciation history of the Baltic Sea area, with up-dammed lakes and early phases of post-glacial seas has, at times, left southwestern Estonia submerged, while at other times, it emerged as terrestrial land. Therefore, transgressive deposition of water-laid sediments of the Ancylus Lake and the Litorina Sea have lead to repeated burial of soil, peat and gyttja deposits and associated settlement layers. The authors combined geological, geodetic and archaeological shore displacement evidence to create a temporal and spatial water-level change model for the SW Estonian coast of the Baltic Sea to examine the relationships between coastline change and submerged Stone Age settlements including the oldest Estonia human occupation in Pulli (10.8-10.2 cal. ka BP). The Baltic Sea shoreline database for Estonian territory was used for the modeling work and contained about 1200 sites from the Baltic Ice Lake, Ancylus Lake and Litorina Sea stages. This database was combined with a compiled shore displacement curve. The curve was reconstructed on the basis of palaeocoastline elevations and radiocarbon dated peat and soil sequences and ecofacts from archeological sites recording three regressive phases of the past Baltic Sea, interrupted by Ancylus Lake (ca 10.8-10.2 cal ka BP) and Litorina Sea (ca 8.5-7.3 cal ka BP) transgressions with magnitudes of 12 m and 10 m, respectively. A water-level change model was applied together with a digital terrain model for reconstruction of coastline development during the Ancylus Lake and Litorina Sea stages in order to understand the preferences of habitation of Stone Age people in the region. PALAEOGEOGRAPHIC RECONSTRUCTION OF THE BALTIC ICE LAKE IN THE EASTERN BALTIC Alar Rosenta. Department of Geology, University of Tartu, Estonia E-mail address: [email protected]
A GIS-based palaeogeographic reconstruction of the development of the Baltic Ice Lake (BIL) in the eastern Baltic during the deglaciation of the Scandinavian Ice Sheet is presented in this study. A Late Glacial shoreline database containing more than 1000 sites from Finland, NW Russia, Estonia, Latvia and modern digital terrain models were used for palaeoreconstructions. The BIL occupied five different levels, represented by 492 shoreline features. The study shows that at about 13.3 cal. ka BP the BIL extended to the ice-free areas of Latvia, Estonia and NW Russia, represented by the highest shoreline in this region. Reconstructions demonstrate that BIL initially had the same water level as the Glacial Lakes Peipsi and Võrtsjärv, because these water bodies were connected via strait systems in central Estonia. These strait systems were closed at about 12.8–11.7 cal. ka BP prior to the final drainage of the BIL due to isostatic uplift. Glacial Lake Võrtsjärv was isolated from the BIL at about 12.4–12.0 cal. ka BP. Exact timing of Glacial Lake Peipsi isolation is not
413
clear, but according to the altitude of the threshold in northeast Estonia and shore displacement data it was completed at about 12.4–11.7 cal. ka BP (Rosentau et al., 2009). DEVELOPMENT OF THE LITTORINA SEA AND ITS RELATIONS WITH NEOLITHIC HUMAN OCCUPATIONS IN NARVA-LUGA KLINT BAY AREA IN THE EASTERN BALTIC SEA Alar Rosentau. Department of Geology, University of Tartu, Estonia E-mail address: [email protected]
The published and new shore displacement evidences from NW Russia and NE Estonia were used to reconstruct past sea-level changes of the Baltic Sea in the Narva-Luga Klint Bay area. For the sea-level reconstruction the Littorina Sea coastal landform elevations and shore displacement data from six uplifted lake basins were used. Reconstructed shore displacement curve displays the Littorina Sea transgression with magnitude of 8 m at about 8.5-7.5 cal ka BP and its later regression. Due to the uneven glacioisostatic land-uplift the highest coastal landforms of the Littorina Sea are locating at altitude of 14 m a.s.l. in the north and 6 m a.s.l. in the southern part of the Klint Bay area. After 7.5 cal ka BP the relative sea level rise was turned to the sea level fall as the eustatic sea level rise was slowed down and the land-uplift started to prevail. Spatial and temporal paleogeographic model was developed for the Narva-Luga Klint Bay area using the shore displacement curve and the land-uplift data and digital terrain model. This model was used to investigate relationships between shore displacement and displacement of Neolithic human occupations in our study area. Comparison of settlement sites locations with paleogeographic reconstructions show that Littorina Sea lagoon shores were the most preferred living environments for Neolithic human occupations during the period between ca 7.1-6.0 cal ka BP. Later, due to the ongoing regression of the Littorina Sea, the lagoon was gradually isolated from the sea, forming several small lakes which finally turned into mires. Overgrowing of lagoon made the people abandon their traditional coastal settlement sites and forced them to find new suitable living environments. Thus at the end of the Neolithic period and at the beginning of the Early Metal Age the settlement sites were mostly concentrated along the ancient rivers in the Narva-Luga Klint Bay area.
LATE PLEISTOCENE - HOLOCENE IN ALTO RIBATEJO (WESTERN IBERIA), DEPOSITS AND PALEOENVIRONMENT CHANGES Pierluigi Rosina. Instituto Politécncico de Tomar, Quaternary and Pr, Portugal E-mail address: [email protected]
The Alto Ribatejo region (central Portugal) is under the influence of both Mediterranean and Atlantic climatic conditions. In the region, the Tagus River flows across three geological and geomorphological units: the Hesperic massif (Pre-Cambrian and Paleozoic metamorphic basement), a Mesozoic limestone massif, and a Cenozoic sedimentary basin. So, in this relatively small area (2,500 Km2), the landscape is quite diversified. The regional Quaternary deposits are represented by: a) the Holocene alluvial sediments, b) the Pleistocene wide fluvial terraces, c) the karstic cave fillings (in limestone massif), d) Aeolian sediments and e) the detritical coverings (colluviums). Sedimentological analysis, performed mostly in deposits associated with archaeological sites documenting the last w25,000 years, show the influence of climatic variations and of anthropic activities. Archaeobotanic remains show that during the Holocene a spread of shrubs in relation to the arborean vegetation, with decrease of oaks and pines woodlands, occurred. Holocene climatic oscillations and the human influence on the landscape, particularly the adoption of agro-pastoralism subsistence system, could be responsible for this evolution. Available data on cerealia and graminacea pollens point out for an increasing human impact on the landscape during the Holocene. First anthropic markers are dating back to 6,000 BC. Paleontological remains were found only in anthropic contexts, showing relationship between hunting activities and pastoralism