- Email: [email protected]
Holocene transgressions of the Caspian Sea
478
Abstracts / Quaternary International 279-280 (2012) 462–565
RECOGNITION OF HAKONE-TAU11 TEPHRA AND SEA-LEVEL CHANGE FROM MIS 6 TO 5 AROUND MITO, NORTHEAST KANTO, CENTRAL JAPAN Takehiko Suzuki. Tokyo Metropolitan University, Japan E-mail address: [email protected]
Ascending of sea-level from MIS 6 to 5.5 is one of the most prominent sealevel changes in late Quaternary, equivalent to that from MIS 2 to 1. However, reconstruction of detailed process of the sea-level rise in this period is not enough, comparing to numerous studies on sea-level changes from MIS 2 to 1. Here, we present new tephrochronological data on sealevel change from MIS 6 to 5.5 in northeast part of the Kanto Plain, central Japan. In this area a MIS 5.5 to 5.3 marine terrace and younger fluvial terraces are widely developed. Beneath these terraces, several buried valleys were developed. Previous studies reported several different ages on these buried valleys, suggesting complexity of formation of valleys responding to sea-level changes. All-core boring was carried out at Mito 1st High School on fluvial Uwaichi Terrace, showing terrace deposit, the Lower part of the Miwa Formation (LMF; Sakamoto, 1972) and basement rock. We recognized a thin glassy ash tephra (1 cm) in LMF at 13.6 m asl. This tephra, here named Mito 1st High School Tephra (MHS), contains pumice type of glass shards (77.8 wt.% of SiO2, high content of CaO and low content of K2O). At Miyamae, ca. 10 km south of Mito 1st High School, the Middle part of the Miwa Formation (MMF; Sakamoto, 1972) exposes. Suzuki (1990) described a thin glassy ash tephra (1 cm) in this silt, here newly named Miyamae Tephra (MT). MT contains pumice type of glass shards with similar properties of MHS. This suggests that they are identical. We attempted to look for the proximal tephra, and it is clarified that TAu11 derived from Hakone Volcano can be correlated to MHS-MT. Arai et al. (1977) concluded that the period of successive Hakone eruptions producing tephras from TAu10 to KlP1 was the same as the transgression from MIS 6 to MIS 5.5. Presence of TAu11 (just above TAu10) in LMF and MMF indicates that they were deposited with filling paleo-valley formed at the low stand of sea-level of MIS 6. ADVANCEMENT OF SUBARCTIC FORESTS DURING THE LITTLE ICE AGE IN THE SOUTH HOKKAIDO, JAPAN - VEGETATION CHANGE AND TEPHROCHRONOLOGY Masaaki Suzuki. Dohto University, Japan E-mail address: [email protected]
1. Tephra sequence in peat sections In studied area, there are three main active volcanoes. However, no volcanic eruptions had occurred in at least 600 years before 1640, when Komagatake volcano erupted and produced Ko-d tephra . Then, 4 more big eruptions continued ; from Usu volcano Us-b pumice, and Us-b-ash in 1663, from Tarumae volcano Ta-b pumice/ash in1667, from Komagatake Ko-c2 pumice in 1694, and from Tarumae volcano Ta-a pumice in 1739. These tephras deposited in marsh land along the coast of Shiraoi-Yufutsu, so we can observe them clearly in peat sections in several gravel pits. These tephras determine the ages of peat sections precisely, and enable to reconstruct vegetation change.
Minimum (sunspot absence from 1645 to 1715). It is also the term of frequent volcanic eruptions occurred from Komagatake, Usu, and Tarumae volcanoes. These eruptions must damage the forests severely. However, in the peatland along the Shiraoi-Yufutsu coast, except for Us-b pumice(1663) of thick pumice fall, four tephras are very thin layers of very fine pumice or volcanic ash, those may give minor effect on vegetation. Therefore, we need to consider cold climate in Little Ice Age, probably attributing to weak solar activity in Maunder minimum, or volcanic aerosol from such eruptions, as a cause of revival of arctic forest. GLACIAL AND CLIMATE HISTORY OF THE POLAR URALS, ARCTIC RUSSIA, DURING THE LAST ICE AGE John Inge Svendsen. University of Bergen/Department of Earth Science a, Norway E-mail address: [email protected]
Field based research the Polar Urals has been carried out within the framework of the international IPY-project “The Ice Age Development and Human Settlement in Northern Eurasia” (ICEHUS). A principal aim has been to reconstruct the dimensions and timing of local glaciers and their interaction with the much larger shelf-centered ice sheets. Aerial photos as well as satellite images have been used to map out moraines and other iceproximal deposits. The chronology is based on optically stimulated luminescence dating (OSL), cosmogenic isotopes (10Be) and 14C-dating. We have also collected seismic records and sediment cores from selected mountain lakes. The results demonstrate that the northernmost part of the mountain chain was inundated by the Barents-Kara Ice Sheet at least twice during early stages (MIS 5b and 4) of the last Ice Age. The shelf-centered ice sheets were then squeezing far into some of the valleys forming distinct horseshoe-shaped facing up-valley moraines. At around 60–70 ka (MIS 4) extended local glaciers existed in the interior of the mountain chains, at places forming local ice caps. Following a major deglaciation during MIS 3 the glaciers started to grow again culminating around 25–20 ka (LGM). However, the glaciers were significantly smaller than during MIS 4 and they did not reach the lowland. In this respect the glacial history stand out from the development in the “Atlantic” region further to the west. However, the timing of the main events may have nevertheless been more or less synchronous across the entire hemisphere. The local glaciers melted away soon after 15 ka and during Early/Mid Holocene there were probably no glaciers at all in the Ural Mountains. THE MISSING TEPHRA HORIZONS IN THE GREENLAND ICE CORES Anders Svensson. University of Copenhagen, Denmark E-mail address: [email protected]
In three peat sections we have analyzed evolution in pollen assemblages. From the result, marsh to hill elements of Alnus, Betula and Quercus were dominant throughout the section. On the other hand, subarctic (mountain) elements show important trend. After Ko-d (1640), Abies, Picea and Pinus were increasing, around Ko-c2 (1694) mostly dominated, especially Picea increased to 9%, and decreased before Ta-a (1739). Betula shows the similar trend.
Tephra horizons remain one of the more robust ways of linking paleoarchives of various types. Currently, good progress is made in the identification of tephra and cryptotephra in the Greenland ice cores and this provides valuable references for stratigraphic linking of paleoarchives mainly in the North Atlantic region. There are, however, a number of key volcanic horizons which have not yet been identified as tephra layers in the Greenland ice cores and some may never be identified if tephra did not make its way to Greenland. Those horizons include the Laacher See Tephra (LST, Germany, 12.9 ka BP), the Campanian Ignimbrite (CI) tephra (Italy, ca. 40 ka BP), and the Toba eruption (Indonesia, ca. 74 ka BP). Although no tephra has been identified for these volcanic events, they have still been recorded in the ice cores as distinct acidity spikes. Whereas tephra layers are relatively rare in the ice cores, acidity spikes of volcanic origin are quite common. The problem remains, of course, to identify the source of the layers. In this paper, we discuss the potential of assigning an acidity spike and thereby an age to some of those ‘missing tephra horizons’ in the ice cores. The location of the ‘right’ acidity spike in the ice core may for example be constrained by closely matching the ice core record to another paleorecord in which the tephra is identified.
3. Discussion
HOLOCENE TRANSGRESSIONS OF THE CASPIAN SEA
Above-mentioned vegetation change in the south Hokkaido, increase and decrease of subarctic forests, is corresponding to the term of Maunder
E-mail address: [email protected]
2. Reconstruction of the former vegetation
Alexander Svitoch. Moscow State University, Russian Federation
Abstracts / Quaternary International 279-280 (2012) 462–565
Caspian Sea is a regressive water basin. This regressive stage in its evolution started in the Early Holocene at the end of the Khvalinian transgression and considerable sea-level lowstand. Since those times periodical sea-level rises never reached positive absolute heights. These rises can be classified as low-order sea-level rhythms (stages, phases, oscillations, convulsions). The Caspian Sea Holocene is characterized by transgressiveregressive sea-level changes of different amplitude reflected in the series of facies of various age. Their stratigraphical subdivision is largely based on fossil molluscan assemblages and absolute age estimations together with geomorphological setting. Numerous radiocarbon datings (more than 170) have been so far obtained for Holocene deposits of the Caspian Sea. Given the present Caspian Sea level of -28 m, when analyzing radiocarbon dates we assume that all datings of the coastal sediments reflect transgressive rhythms of the Caspian Sea during Post-Khvalinian regression, while the datings from shelf and basin depressions just record various sea-level lowstands. Numerous radiocarbon datings (more than 170) have been so far obtained for Holocene deposits of the Caspian Sea. Given the present Caspian Sea level of -28 m, when analyzing radiocarbon dates we assume that all datings of the coastal sediments reflect transgressive rhythms of the Caspian Sea during Post-Khvalinian regression, while the datings from shelf and basin depressions just record various sea-level lowstands. THE CASPIAN-MANYCH-PONT SYSTEM DURING PLEISTOCENE Alexander Svitoch. Moscow State University, Russian Federation
479
advantages of using the varve sequences are that diatoms are already somewhat separated into mono-taxic layers, the preservation is excellent minimising the impact of silica maturation and we can investigate vital effects by looking at quasi year-on-year sequences. Further, we will present a preliminary record for the whole Holocene (w11-0 cal kyr BP) and will interpret the results in terms of changes in melt water input to the west Antarctic Peninsula margin. REGULATION OF ATMOSPHERIC PCO2 BY THE SUBARCTIC NORTH WEST PACIFIC OCEAN SINCE THE LAST INTERGLACIAL George Swann. University of Nottingham, United Kingdom E-mail address: [email protected]
The large 80-100 ppmv variations in atmospheric pCO2 documented in icecores from Antarctica over the last 1 Ma, provide an essential forcing mechanism in driving the glacial-interglacial climate system. Existing research on the terrestrial biosphere as well as the low latitude and Southern Oceans are capable of explaining c. 50% of this variability. Diatom isotope and other proxy records are presented here showing that changes in the strength of the subarctic North West Pacific Ocean biological pump and the regional halocline also played a key role in regulating atmospheric pCO2 between Marine Isotope Stage (MIS) 5e, the last interglacial, and MIS 4. In conjunction with research focused on other sectors of the terrestrial and marine system, these results provide a means of further explaining long-term global changes in atmospheric pCO2.
E-mail address: [email protected]
Caspian and Black seas represent the system of midland basins - the relicts of East Parathetis which have broken up in the end of Neogene on semiisolated and isolated basins with different in history. During considerable part of the Pleistocene the Caspian Sea was a closing basin with sharp sea level fluctuations and with periodical drain on the Manych passage. During the epochs of transgressions the area of the Caspian Sea was increased by 2,5; the level was raised by almost 80 m. The maximum sea level (+50 m) was controlled by the height of the east bridge of the Manych. During regressions the sea level fell to-50 m (and more low). The history of the Black Sea consisted in periodic change of flowing and closing regimen. The flowing basin was characteristic for late Chauda. The drain of waters across the Bosporus was carried out in the end of Late Chauda, Uzunlar, Karangat and the Black Sea time. The closing basins existed in the New Euxinian epoch and (possibly) during the maximum of regressions. The amplitude of sea level fluctuations was about 100 m. The role of the Manych in the development of the Pont and Caspian basins was different, caused by the existence of the passage in the Manych depression, or an overland bridge. The Influence of the Caspian waters on the Pont Pleistocene basins was almost unilateral. The consequences of the Caspian drain in the Pont basins were the changes of the Black Sea and Caspian Sea levels, the water composition and fauna migration. THE FIRST LATE QUATERNARY DIATOM d18O RECORD FROM THE WEST ANTARCTIC PENINSULA CONTINENTAL MARGIN George Swann. University of Nottingham, United Kingdom E-mail address: [email protected]
Exceptional high resolution Antarctic shelf sediment cores recovered during the last 15 years contain remarkable archives of ice-oceanclimate interactions through the last deglaciation (w13-11 cal kyr BP). In many of these cores, such as that from Palmer Deep, west Antarctic Peninsula, deglacial sediment sequences are laminated and laminations are dominated by well-preserved fossil planktonic diatom assemblages; individual species of which are sensitive to sea surface conditions including sea ice concentration, fresh water influx, and open ocean influence upon the margin. The deglacial laminations are seasonal in origin and have been established as marine varves. For the first time, we are applying diatom d18O measurements to west Antarctic Peninsula shelf sediments. Specifically, we are targeting the Palmer Deep varves in order to construct seasonal isotope records and have analysed single taxa sequences of spring laminations (dominated by Hyalochaete Chaetocerosresting spores) and autumnal laminations (dominated by Thalassiosira antarctica resting spores) through the deglaciation. The
HIGH VARIABILITY OF EUROPEAN FLOODS DURING THE LAST 4000 YEARS: A SEASONAL RECORD OF RUNOFF EVENTS FROM VARVED SEDIMENTS OF LAKE MONDSEE (UPPER AUSTRIA) Tina Swierczynski. GFZ-German Research Centre for Geosciences, Germany E-mail address: [email protected]
The natural magnitude and frequency of floods are increasingly debated concerning a possible intensification of the water cycle affected by global warming. Geoarchives such as lake sediments are used to extend instrumental and historical data recording runoff events on longer time scales. Annually laminated (varved) lake sediments of Lake Mondsee provide a long and continuous seasonal record of past environmental changes. Detrital catchment material (minerogenic and organic debris) intercalated within biogenic calcite varves, has been supplied by extreme discharge events in spring and summer, i.e. floods and debris flows. In order to distinguish flood layers from debris flow layers, a combination of detailed sediment microfacies analysis on large-scale petrographic thin sections and magnetic susceptibility, X-ray diffraction and micro X-ray fluorescence measurements has been applied (see also Brauer et al., 2009). A 4000-year record of spring/summer floods and debris flows preserved in the Lake Mondsee reveals a clear non-stationarity of runoff events through time. Spring/summer flood periods occur in intervals of 30-50 years, with a recurrence time of ca 4-6.6 years for floods and ca 90 years for debris flows. Highest flood frequencies occur during the onset of the Little Ice Age (AD 1300-1500), the Migration Period (AD 350-750), Iron Age (AD 100400) and Bronze Age (BC 1300-1600). Lowest flood activity is detected e.g. during the Roman climatic optimum (AD 0-200) as well as during the coldest stage within the Little Ice Age (Maunder Minimum ca AD 16451715). We suggest a close correspondence of increased flood activity during the transition towards cooling climate conditions. In contrast, less frequent floods are detected during both coldest and warmest climate conditions suggesting substantial changes in atmospheric circulation patterns generating less flood prone weather regimes in the North-Eastern Alps. THE OVERDEEPENED GLACIER LANDSYSTEM: A NEW LANDSYSTEM MODEL BASED ON OBSERVATIONS FROM SOUTHEAST ICELAND Darrel A. Swift. University of Sheffield, United Kingdom E-mail address: D.A.Swift@Sheffield.ac.uk
Observations from two glaciers in southeast Iceland (Svínafellsjökull and Kvíárjökull) are used to propose a new landsystem model that is unique to glaciers with terminal overdeepenings. The model is characterised by the
Abstracts / Quaternary International 279-280 (2012) 462–565
RECOGNITION OF HAKONE-TAU11 TEPHRA AND SEA-LEVEL CHANGE FROM MIS 6 TO 5 AROUND MITO, NORTHEAST KANTO, CENTRAL JAPAN Takehiko Suzuki. Tokyo Metropolitan University, Japan E-mail address: [email protected]
Ascending of sea-level from MIS 6 to 5.5 is one of the most prominent sealevel changes in late Quaternary, equivalent to that from MIS 2 to 1. However, reconstruction of detailed process of the sea-level rise in this period is not enough, comparing to numerous studies on sea-level changes from MIS 2 to 1. Here, we present new tephrochronological data on sealevel change from MIS 6 to 5.5 in northeast part of the Kanto Plain, central Japan. In this area a MIS 5.5 to 5.3 marine terrace and younger fluvial terraces are widely developed. Beneath these terraces, several buried valleys were developed. Previous studies reported several different ages on these buried valleys, suggesting complexity of formation of valleys responding to sea-level changes. All-core boring was carried out at Mito 1st High School on fluvial Uwaichi Terrace, showing terrace deposit, the Lower part of the Miwa Formation (LMF; Sakamoto, 1972) and basement rock. We recognized a thin glassy ash tephra (1 cm) in LMF at 13.6 m asl. This tephra, here named Mito 1st High School Tephra (MHS), contains pumice type of glass shards (77.8 wt.% of SiO2, high content of CaO and low content of K2O). At Miyamae, ca. 10 km south of Mito 1st High School, the Middle part of the Miwa Formation (MMF; Sakamoto, 1972) exposes. Suzuki (1990) described a thin glassy ash tephra (1 cm) in this silt, here newly named Miyamae Tephra (MT). MT contains pumice type of glass shards with similar properties of MHS. This suggests that they are identical. We attempted to look for the proximal tephra, and it is clarified that TAu11 derived from Hakone Volcano can be correlated to MHS-MT. Arai et al. (1977) concluded that the period of successive Hakone eruptions producing tephras from TAu10 to KlP1 was the same as the transgression from MIS 6 to MIS 5.5. Presence of TAu11 (just above TAu10) in LMF and MMF indicates that they were deposited with filling paleo-valley formed at the low stand of sea-level of MIS 6. ADVANCEMENT OF SUBARCTIC FORESTS DURING THE LITTLE ICE AGE IN THE SOUTH HOKKAIDO, JAPAN - VEGETATION CHANGE AND TEPHROCHRONOLOGY Masaaki Suzuki. Dohto University, Japan E-mail address: [email protected]
1. Tephra sequence in peat sections In studied area, there are three main active volcanoes. However, no volcanic eruptions had occurred in at least 600 years before 1640, when Komagatake volcano erupted and produced Ko-d tephra . Then, 4 more big eruptions continued ; from Usu volcano Us-b pumice, and Us-b-ash in 1663, from Tarumae volcano Ta-b pumice/ash in1667, from Komagatake Ko-c2 pumice in 1694, and from Tarumae volcano Ta-a pumice in 1739. These tephras deposited in marsh land along the coast of Shiraoi-Yufutsu, so we can observe them clearly in peat sections in several gravel pits. These tephras determine the ages of peat sections precisely, and enable to reconstruct vegetation change.
Minimum (sunspot absence from 1645 to 1715). It is also the term of frequent volcanic eruptions occurred from Komagatake, Usu, and Tarumae volcanoes. These eruptions must damage the forests severely. However, in the peatland along the Shiraoi-Yufutsu coast, except for Us-b pumice(1663) of thick pumice fall, four tephras are very thin layers of very fine pumice or volcanic ash, those may give minor effect on vegetation. Therefore, we need to consider cold climate in Little Ice Age, probably attributing to weak solar activity in Maunder minimum, or volcanic aerosol from such eruptions, as a cause of revival of arctic forest. GLACIAL AND CLIMATE HISTORY OF THE POLAR URALS, ARCTIC RUSSIA, DURING THE LAST ICE AGE John Inge Svendsen. University of Bergen/Department of Earth Science a, Norway E-mail address: [email protected]
Field based research the Polar Urals has been carried out within the framework of the international IPY-project “The Ice Age Development and Human Settlement in Northern Eurasia” (ICEHUS). A principal aim has been to reconstruct the dimensions and timing of local glaciers and their interaction with the much larger shelf-centered ice sheets. Aerial photos as well as satellite images have been used to map out moraines and other iceproximal deposits. The chronology is based on optically stimulated luminescence dating (OSL), cosmogenic isotopes (10Be) and 14C-dating. We have also collected seismic records and sediment cores from selected mountain lakes. The results demonstrate that the northernmost part of the mountain chain was inundated by the Barents-Kara Ice Sheet at least twice during early stages (MIS 5b and 4) of the last Ice Age. The shelf-centered ice sheets were then squeezing far into some of the valleys forming distinct horseshoe-shaped facing up-valley moraines. At around 60–70 ka (MIS 4) extended local glaciers existed in the interior of the mountain chains, at places forming local ice caps. Following a major deglaciation during MIS 3 the glaciers started to grow again culminating around 25–20 ka (LGM). However, the glaciers were significantly smaller than during MIS 4 and they did not reach the lowland. In this respect the glacial history stand out from the development in the “Atlantic” region further to the west. However, the timing of the main events may have nevertheless been more or less synchronous across the entire hemisphere. The local glaciers melted away soon after 15 ka and during Early/Mid Holocene there were probably no glaciers at all in the Ural Mountains. THE MISSING TEPHRA HORIZONS IN THE GREENLAND ICE CORES Anders Svensson. University of Copenhagen, Denmark E-mail address: [email protected]
In three peat sections we have analyzed evolution in pollen assemblages. From the result, marsh to hill elements of Alnus, Betula and Quercus were dominant throughout the section. On the other hand, subarctic (mountain) elements show important trend. After Ko-d (1640), Abies, Picea and Pinus were increasing, around Ko-c2 (1694) mostly dominated, especially Picea increased to 9%, and decreased before Ta-a (1739). Betula shows the similar trend.
Tephra horizons remain one of the more robust ways of linking paleoarchives of various types. Currently, good progress is made in the identification of tephra and cryptotephra in the Greenland ice cores and this provides valuable references for stratigraphic linking of paleoarchives mainly in the North Atlantic region. There are, however, a number of key volcanic horizons which have not yet been identified as tephra layers in the Greenland ice cores and some may never be identified if tephra did not make its way to Greenland. Those horizons include the Laacher See Tephra (LST, Germany, 12.9 ka BP), the Campanian Ignimbrite (CI) tephra (Italy, ca. 40 ka BP), and the Toba eruption (Indonesia, ca. 74 ka BP). Although no tephra has been identified for these volcanic events, they have still been recorded in the ice cores as distinct acidity spikes. Whereas tephra layers are relatively rare in the ice cores, acidity spikes of volcanic origin are quite common. The problem remains, of course, to identify the source of the layers. In this paper, we discuss the potential of assigning an acidity spike and thereby an age to some of those ‘missing tephra horizons’ in the ice cores. The location of the ‘right’ acidity spike in the ice core may for example be constrained by closely matching the ice core record to another paleorecord in which the tephra is identified.
3. Discussion
HOLOCENE TRANSGRESSIONS OF THE CASPIAN SEA
Above-mentioned vegetation change in the south Hokkaido, increase and decrease of subarctic forests, is corresponding to the term of Maunder
E-mail address: [email protected]
2. Reconstruction of the former vegetation
Alexander Svitoch. Moscow State University, Russian Federation
Abstracts / Quaternary International 279-280 (2012) 462–565
Caspian Sea is a regressive water basin. This regressive stage in its evolution started in the Early Holocene at the end of the Khvalinian transgression and considerable sea-level lowstand. Since those times periodical sea-level rises never reached positive absolute heights. These rises can be classified as low-order sea-level rhythms (stages, phases, oscillations, convulsions). The Caspian Sea Holocene is characterized by transgressiveregressive sea-level changes of different amplitude reflected in the series of facies of various age. Their stratigraphical subdivision is largely based on fossil molluscan assemblages and absolute age estimations together with geomorphological setting. Numerous radiocarbon datings (more than 170) have been so far obtained for Holocene deposits of the Caspian Sea. Given the present Caspian Sea level of -28 m, when analyzing radiocarbon dates we assume that all datings of the coastal sediments reflect transgressive rhythms of the Caspian Sea during Post-Khvalinian regression, while the datings from shelf and basin depressions just record various sea-level lowstands. Numerous radiocarbon datings (more than 170) have been so far obtained for Holocene deposits of the Caspian Sea. Given the present Caspian Sea level of -28 m, when analyzing radiocarbon dates we assume that all datings of the coastal sediments reflect transgressive rhythms of the Caspian Sea during Post-Khvalinian regression, while the datings from shelf and basin depressions just record various sea-level lowstands. THE CASPIAN-MANYCH-PONT SYSTEM DURING PLEISTOCENE Alexander Svitoch. Moscow State University, Russian Federation
479
advantages of using the varve sequences are that diatoms are already somewhat separated into mono-taxic layers, the preservation is excellent minimising the impact of silica maturation and we can investigate vital effects by looking at quasi year-on-year sequences. Further, we will present a preliminary record for the whole Holocene (w11-0 cal kyr BP) and will interpret the results in terms of changes in melt water input to the west Antarctic Peninsula margin. REGULATION OF ATMOSPHERIC PCO2 BY THE SUBARCTIC NORTH WEST PACIFIC OCEAN SINCE THE LAST INTERGLACIAL George Swann. University of Nottingham, United Kingdom E-mail address: [email protected]
The large 80-100 ppmv variations in atmospheric pCO2 documented in icecores from Antarctica over the last 1 Ma, provide an essential forcing mechanism in driving the glacial-interglacial climate system. Existing research on the terrestrial biosphere as well as the low latitude and Southern Oceans are capable of explaining c. 50% of this variability. Diatom isotope and other proxy records are presented here showing that changes in the strength of the subarctic North West Pacific Ocean biological pump and the regional halocline also played a key role in regulating atmospheric pCO2 between Marine Isotope Stage (MIS) 5e, the last interglacial, and MIS 4. In conjunction with research focused on other sectors of the terrestrial and marine system, these results provide a means of further explaining long-term global changes in atmospheric pCO2.
E-mail address: [email protected]
Caspian and Black seas represent the system of midland basins - the relicts of East Parathetis which have broken up in the end of Neogene on semiisolated and isolated basins with different in history. During considerable part of the Pleistocene the Caspian Sea was a closing basin with sharp sea level fluctuations and with periodical drain on the Manych passage. During the epochs of transgressions the area of the Caspian Sea was increased by 2,5; the level was raised by almost 80 m. The maximum sea level (+50 m) was controlled by the height of the east bridge of the Manych. During regressions the sea level fell to-50 m (and more low). The history of the Black Sea consisted in periodic change of flowing and closing regimen. The flowing basin was characteristic for late Chauda. The drain of waters across the Bosporus was carried out in the end of Late Chauda, Uzunlar, Karangat and the Black Sea time. The closing basins existed in the New Euxinian epoch and (possibly) during the maximum of regressions. The amplitude of sea level fluctuations was about 100 m. The role of the Manych in the development of the Pont and Caspian basins was different, caused by the existence of the passage in the Manych depression, or an overland bridge. The Influence of the Caspian waters on the Pont Pleistocene basins was almost unilateral. The consequences of the Caspian drain in the Pont basins were the changes of the Black Sea and Caspian Sea levels, the water composition and fauna migration. THE FIRST LATE QUATERNARY DIATOM d18O RECORD FROM THE WEST ANTARCTIC PENINSULA CONTINENTAL MARGIN George Swann. University of Nottingham, United Kingdom E-mail address: [email protected]
Exceptional high resolution Antarctic shelf sediment cores recovered during the last 15 years contain remarkable archives of ice-oceanclimate interactions through the last deglaciation (w13-11 cal kyr BP). In many of these cores, such as that from Palmer Deep, west Antarctic Peninsula, deglacial sediment sequences are laminated and laminations are dominated by well-preserved fossil planktonic diatom assemblages; individual species of which are sensitive to sea surface conditions including sea ice concentration, fresh water influx, and open ocean influence upon the margin. The deglacial laminations are seasonal in origin and have been established as marine varves. For the first time, we are applying diatom d18O measurements to west Antarctic Peninsula shelf sediments. Specifically, we are targeting the Palmer Deep varves in order to construct seasonal isotope records and have analysed single taxa sequences of spring laminations (dominated by Hyalochaete Chaetocerosresting spores) and autumnal laminations (dominated by Thalassiosira antarctica resting spores) through the deglaciation. The
HIGH VARIABILITY OF EUROPEAN FLOODS DURING THE LAST 4000 YEARS: A SEASONAL RECORD OF RUNOFF EVENTS FROM VARVED SEDIMENTS OF LAKE MONDSEE (UPPER AUSTRIA) Tina Swierczynski. GFZ-German Research Centre for Geosciences, Germany E-mail address: [email protected]
The natural magnitude and frequency of floods are increasingly debated concerning a possible intensification of the water cycle affected by global warming. Geoarchives such as lake sediments are used to extend instrumental and historical data recording runoff events on longer time scales. Annually laminated (varved) lake sediments of Lake Mondsee provide a long and continuous seasonal record of past environmental changes. Detrital catchment material (minerogenic and organic debris) intercalated within biogenic calcite varves, has been supplied by extreme discharge events in spring and summer, i.e. floods and debris flows. In order to distinguish flood layers from debris flow layers, a combination of detailed sediment microfacies analysis on large-scale petrographic thin sections and magnetic susceptibility, X-ray diffraction and micro X-ray fluorescence measurements has been applied (see also Brauer et al., 2009). A 4000-year record of spring/summer floods and debris flows preserved in the Lake Mondsee reveals a clear non-stationarity of runoff events through time. Spring/summer flood periods occur in intervals of 30-50 years, with a recurrence time of ca 4-6.6 years for floods and ca 90 years for debris flows. Highest flood frequencies occur during the onset of the Little Ice Age (AD 1300-1500), the Migration Period (AD 350-750), Iron Age (AD 100400) and Bronze Age (BC 1300-1600). Lowest flood activity is detected e.g. during the Roman climatic optimum (AD 0-200) as well as during the coldest stage within the Little Ice Age (Maunder Minimum ca AD 16451715). We suggest a close correspondence of increased flood activity during the transition towards cooling climate conditions. In contrast, less frequent floods are detected during both coldest and warmest climate conditions suggesting substantial changes in atmospheric circulation patterns generating less flood prone weather regimes in the North-Eastern Alps. THE OVERDEEPENED GLACIER LANDSYSTEM: A NEW LANDSYSTEM MODEL BASED ON OBSERVATIONS FROM SOUTHEAST ICELAND Darrel A. Swift. University of Sheffield, United Kingdom E-mail address: D.A.Swift@Sheffield.ac.uk
Observations from two glaciers in southeast Iceland (Svínafellsjökull and Kvíárjökull) are used to propose a new landsystem model that is unique to glaciers with terminal overdeepenings. The model is characterised by the