- Email: [email protected]
Impact of the environment on nomad migrations in the northern Black Sea region
Abstracts / Quaternary International 279-280 (2012) 233–345
chlorophyll waters , and resultant drawdown of atmospheric CO2. A strong direct correlation exists between the records of Antarctic dust flux and the magnetic susceptibility of Southern Ocean sediments. To identify the source of the variations in sediment magnetic content and provenance, detailed mineral magnetic analyses have been performed on particle-sized fractions of both a subset of the sediment samples and a range of potential source materials, including present dust source areas in Patagonia and the Altiplano region, and marine sediments, spanning the W. Patagonian and Antarctic continental margins. Quantitative source identification and attribution enables detailed estimation of past changes in dust fluxes, and their possible significance with regard to iron flux and pathways of atmospheric circulation. STABLE OXYGEN AND SILICON ISOTOPES OF BIOGENIC SILICA – NEW PROXIES FOR RECONSTRUCTING PLEISTOCENE CHANGES IN WATER MASS STRUCTURES AND NUTRIENT UTILIZATION IN THE POLAR NORTH PACIFIC (SO202-INOPEX)
301
their origin. Wherever we record habitants (traces of life) we trace habitation (paleosols). Evolution of soils and biota may be understood as an evolution of ecosystems, that is a new paradigm for geosciences (Zavarzin, 1995). Co-evolution of life and soils is a large-scale biogeochemical succession with an increased role of biological cycles in a geological cycle. Paleosols record a broad number of parameters (qualitative and increasing number of quantitative) and environmental links of former ecosystems, even if bio fossils are extinct. Co-evolution is especially obvious for revolutionary changes in weathering, like oxygenation of the atmosphere, radiation of higher plants and grasses. Paleosols comprise the major record in Quaternary terrestrial archives and are in the center of such multidisciplinary challenges like global climate change, carbon sequestration and cryobiosphere. Considerable part of present-day pedosphere consists of surface paleosols with their profiles keeping record of final stages of sedimentation and former environments. TRANSBOUNDARY FACTOR EFFECT ON MANAGEMENT IN THE AMUR RIVER BASIN
WATER
RESOURCE
Edith Maier. Alfred Wegener Institute, Germany E-mail address: [email protected]
Stable oxygen (d18O) and silicon (d30Si) isotopes of biogenic silica (diatoms and radiolarians) will be analysed on opal-rich sediments from the Patton Seamounts (SO202-27-6), Gulf of Alaska. This new methodological approach will be used to get new insights in the hydrography and nutrient utilization of the polar North Pacific on glacial-interglacial timescales. The studied core records the time since the last glacial period. Dating will be based on a combination of AMS-14C measurements and isotope stratigraphy on foraminifera. Combined d18O-analyses on surface dwelling photosynthetic diatoms and deeper living heterotrophic radiolarians shall provide information on surface water hydrography, especially on changes in salinity and surface water stratification. The Gulf of Alaska has been the catchment area of glaciers from the North American Cordilleran Ice Sheet during the last glacial. By reconstructing its salinity history meltwater events from the Cordilleran Ice Sheet may be identified, which might help decipher the influence of (de)glacial meltwater input on water mass structures in the polar North Pacific. Diatom ?30Si-analyses will be used to gain information on local surface water silicic acid utilization and the marine silicon cycle on glacial-interglacial timescales. Being the main siliceous constituent in marine polar sediments, dominating the modern marine silicon cycle and playing an important role in the modern polar North Pacific all makes diatoms the ideal candidates for paleo-nutrient studies. The newly developed method allows routine measurements of d18O- and d30Si- values from the same aliquot and enables a coupled interpretation of both proxies. This is particularly important concerning a possible connection between water mass structure and nutrient utilization. Along with other paleoceanographical proxies, d18O-and d30Si-studies add to a comprehensive understanding regarding past ocean circulation and nutrient utilization in the polar North Pacific.
A. Makhinov. Institute of Water and Ecology Problems FEB RAS, Russian Federation E-mail address: [email protected]
Management of water-resource systems becomes very important in the natural resource system of the eastern regions of Russia. Due to the geographical location of the Amur Basin significant amounts of river water and atmospheric precipitation are transported across the country borders. 260 km3 of the Amur runoff are formed in the Russian part of the basin and 105 km3 are formed in China and Mongolia, which means that 46.2% of river water come to Russia from the neighboring countries. Hydropower stations cause most changes of the hydrological regime. There are three major hydropower stations in the Amur Basin: one in China and two in Russia. They regulate 10% of the basin area. However, the water regime of the Middle and Lower Amur has changed significantly and the conditions of navigation and operations of municipal water intakes became more difficult. Transboundary impacts on the Amur hydrological regime should be considered to manage ecological problems in the Amur Basin more effectively. One of the processes, which hampers economic activities in the basin, is a constant redistribution of water flow between sub-channels coupled with highly intensive river-bed deformations. These processes tend to accelerate in the river passages near the cities and at the junctures of big tributaries, where many factors affect the river regime. Waterworks make water resource management in the Amur Basin highly effective. The construction of overflow dams at the entrance of Pemzenskaya and Beshenaya sub-channels improved the river-bed situation near Khabarovsk. The temporal dam that blocked the Kazakevicheva (Amurskaya) subchannel was very effective to prevent further pollution of the river after the technogenic accident on the Sungari River in 2005. Big water reservoirs in Russia may be used as additional water supplies to mitigate negative consequences in the mostly ecologically vulnerable Lower Amur.
PALEOPEDOLOGY: NEW MEANING FOR GEOSCIENCES
IMPACT OF THE ENVIRONMENT ON NOMAD MIGRATIONS IN THE NORTHERN BLACK SEA REGION
Alexander Makeev. Institute of ecological soil science, Moscow Unive, Russian Federation
Sergey Makhortykh. Institute of Archaeology Ukrainian Academy of Scie, Ukraine
E-mail address: [email protected]
E-mail address: [email protected]
Due to recent advances paleopedology is absorbing many branches in soil science and other geosciences. Modern soilscape is one of innumerable temporal cuts in the evolution of pedosphere from Precambrian to Holocene. The role of paleosols in the evolution of bio-geosphere cycles is based on the fact that more than 90% of all living organisms occur in soils. Biogeochemical record extends far beyond the existing definition of paleosol and includes, following Vernadski, all products influenced by terrestrial biota that constitute pedolithosphere (after Glazovskaya: terrestial sedimentary rocks, weathering crusts, etc., being paleosols, transformed in geo-cycles). Actually paleopedology is a science studying pedolithospheres of the past. With this approach we have continuous record in which newly discovered paleosols are enclosed like new cells in the periodic table. Paleosols determine biosphere-geosphere cycles from
The beginning of the 1st millennium BC was characterized by the formation of nomad pastoralism throughout the Eurasian steppes. It was connected with a long climate aridity, which began in the Pontic region about the 11th century BC. The collapse of such the late Bronze Age cultures as the Belozerka and Post-Srubnaya ones with their mixed pastoral-agricultural economy was a result of this ecological crisis. Early nomads created their own economic system – cattle breeding with horizontal and vertical migrations, in which the structure of herds was basically formed of horses and sheep. At the same time, the transition to nomadism in the different regions of Eurasia had local distinctive features, which promoted the emergence of diverse cultural formations. During the period of increasing climate aridity and decreasing steppe productivity, the nomadic economy experienced a crisis, too. A part of the
302
Abstracts / Quaternary International 279-280 (2012) 233–345
population was forced to leave the Pontic steppe and to move into areas with wetter climate: in the first place - the Dnieper forest-steppe zone and the Northern Caucasus. These new cultural centers played an important role in the history of Eastern Europe within the Early Iron Age. The Cimmerians and Scythians concentrated in these areas mainly during the aridity and penetrated to the south of the Pontic steppe during humidity of climate. The archaeological materials allow us to reconstruct the nomadic economy with horizontal season movements along the Black Sea and Azov Sea shores during weak period of damping of climate and predominance of vertical season movements during long dry period.
the highly centralised Achaemenid state (4th c. BC). Our findings support the hypothesis that they were built instead by the non-centralised and loosely organised Kushan society.
HURRICANES AND CLIMATE IN THE CARIBBEAN DURING THE PAST 3700 YEARS B.P
Subtropical regions are key areas to understand the dynamics of the subtropical anticyclones in the past. However, there is a lack of paleoclimatic information from these areas due mainly to the scarcity of sites to obtain suitable fossil records. In the semiarid zone of Chile (32oS) the presence of swamp forests provide an excellent fossil record to evaluate changes in precipitation linked to the Southern Westerlies wind belt which is modulated in this zone by the annual and interannual dynamic of the South-East Pacific subtropical anticyclone. We present a palaeoenvironmental and palaeoclimatic reconstruction of the semiarid coast of Chile since 13,000 yrs BP. based on the joint analysis of pollen, charcoal and oxygen isotopes (shells) records from swamp forests and archaeological sites. Furthermore, the broad archaeological record allowed comparing human occupations since the first inhabitants to environmental changes. Wet conditions in the area during the Late Pleistocene were followed by a series of dry and wet phases in the early Holocene that recorded the driest period for the whole Holocene between 7700-6200 years BP. Subsequently, the environmental conditions seem to have been gradually more humid with little reversal dry periods between 3000-2000 yrs BP. High proportions of the humidity indicator Myrtaceae between 2000-700 yrs BP suggest a wet general context. Between 550-300 yrs BP, there is a decrease in the humidity indicators which may correspond either to climate or anthropic activity. The charcoal record suggests that the fire dynamics in the area was more strongly associated with human activity than to climate variability. In fact, the largest amounts of charcoal particles were recorded simultaneously with some important cultural events such as the shift from the hunter-gatherer period to the ceramic one and the European settlement. On the other hand, human occupations tend to be more stable during the most humid phases.
Bruno Malaizé. Université Bordeaux I / EPOC, France E-mail address: [email protected]
A multiproxy analysis of lacustrine sediments cored in Grand-Case Pond at Saint-Martin, north of the lesser Antilles archipelago, reveals three distinct climatic periods for the last 3700 years. From 3700 to w2500 a cal. BP and from 1150 a cal. BP to the present, carbonate mud deposition occurred in connection with pond lowstands. These periods were also punctuated by severe drought events, marked by gypsum laminae, and high intensity hurricane landfalls. The intermediate time interval, from 2500 to 1150 a cal. BP, is typified by black organic mud deposition suggesting hypoxic to anoxic conditions which are probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today. The carbon isotopic composition of the ostracod Perissocytheridea bisulcata confirms this pond sedimentation model. Such a climatic history agrees closely with that documented from other records in the Caribbean area, such as the Cariaco Basin, paleo archives from the Yucatan Peninsula or the Barbados. By contrast, discrepancies seem to emerge from the comparison between hurricane activity and paleoclimate history recorded at Saint-Martin on the one hand and Vieques (Puerto Rico) on the other hand. We explain this apparent contradiction by a balance between two distinct storm paths in response to latitudinal shifts of the Inter-tropical Convergence Zone (ITCZ). Stronger storm activity over the Gulf coast and the inner Caribbean Sea is favoured by a southern position of the ITCZ in connection with dryer climatic conditions.
LATE PLEISTOCENE- HOLOCENE CLIMATIC CHANGES AND HUMAN OCCUPATION IN SUBTROPICAL SEMIARID REGION OF CHILE (32OS) Antonio Maldonado. Universidad de La Serena - Centro de Estudios Avan, Chile E-mail address: [email protected]
POLITICAL POWER AND CLIMATIC VARIABILITY IN WESTERN CENTRAL ASIA; RESULTS FROM A GEOARCHAEOLOGICAL STUDY IN SAMARKAND, UZBEKISTAN
PALEOSEISMIC AND PALEO-TSUNAMI SIGNATURES FROM THE WEST COAST OF SOUTH ANDAMAN, A&N ISLAND, INDIA
Luca C. Malatesta. ETH Zurich, Switzerland
E-mail address: [email protected]
Javed N. Malik. Indian Institute of Technology, Kanpur, India E-mail address: [email protected]
The dense human History of the Central Asian Silk Road provides us with a rich insight in the social, political as well as climatic development of the region. Several archaeological sites document the various irrigation schemes that were designed to support human presence in and around the Tian Shan during the arid late Holocene (ca. 300 BC - 500 AD). This is particularly striking in the Zeravshan Valley in Uzbekistan. From the 4th c. BC onwards, it was one of the Silk Road main paths and extensive irrigation works were engineered to sustain the agriculture around the historical city of Afrosiab, now Samarkand. The irrigation system upstream of the historical city of Afrosiab consisted of two main canals, the Dargom and the Jangi Aryk. We studied deposits of a destructive flood, found in a particularly well studied dwelling next to the Dargom, with sedimentological and surface processes methods. We thus obtained original constraints on the nature of extreme precipitation events at this time (16080 AD, 14C dating). We estimated that an intense precipitation event of at least 65 mm/h for at least 2 hours allowed for a 0.6 m high flooding of the archaeological site based on a numerical model surface overland flow. Elevated dwellings, the usual construction type in the valley at this time and the recurrence of flood horizons in the stratigraphy attest a repetition of floods during the first centuries AD in western Central Asia. We also established a new precise quantitative timeframe for the canals construction time. XRD analysis of the flood-related sediments and further radiocarbon ages confirmed the presence of the two canals in the 2nd c. AD. Furthermore, we could discredit the idea that the canals were a product of
Sediment succession from west coast of Andaman Island around Collinpur (site-1) and Collinpur-4 (site-2) village suggests that the coarse sand+broken shell fragments (unit a) from site-2 is the oldest tsunami (?) deposit (Event I), capped by a peaty unit (unit b). Unit c with coarse sand+broken shells, suggest another tsunami (Event II). This unit is capped by a weak-strongly developed peaty unit d. A thick (28 cm) yellowish coarse sand unit e marks penultimate tsunami event (Event III). Similar w30 cm thick tsunami deposit comprising coarse sand with gravel fragments (corals, shells, rock clasts etc.) in swale portion, and coarse sand+broken shells, peaty material and rip-up clasts of soil on the backlimb of the beach ridge was also identified at site-1. This unit shows sharp contact with underlying peaty unit d. Overlying unit f with partially developed peaty layer suggests probable uplift during Event-III. The couplets of peaty units (b, d and f) representing marshy environment and tsunami (?) sand (units a, c and e) suggests marginal land-level change occurred. Overlying silty-clay (unit g) suggests sub-tidal environment; change from marshy – Event-IV. Thick silty-sand unit (unit h) and overlying humic soil (unit i) of 2004 indicates land-level change, suggesting a gradual uplift during inter-seismic period. Medium to coarse yellowish sand (Unit j) with prominent laminations and sharp contact with unit i marks deposition during 2004 Sumatra-Andaman earthquake (Event-V). AMS ages suggest that Event-I marked by tsunami deposits occurred before 800 AD and Event-II at around 687-877 AD, Event-III 1200-1300 AD with marginal uplift (?) and tsunami deposition; Event-IV marked by subsidence occurred during 1300-1800 AD. It is inferred that the gradual
chlorophyll waters , and resultant drawdown of atmospheric CO2. A strong direct correlation exists between the records of Antarctic dust flux and the magnetic susceptibility of Southern Ocean sediments. To identify the source of the variations in sediment magnetic content and provenance, detailed mineral magnetic analyses have been performed on particle-sized fractions of both a subset of the sediment samples and a range of potential source materials, including present dust source areas in Patagonia and the Altiplano region, and marine sediments, spanning the W. Patagonian and Antarctic continental margins. Quantitative source identification and attribution enables detailed estimation of past changes in dust fluxes, and their possible significance with regard to iron flux and pathways of atmospheric circulation. STABLE OXYGEN AND SILICON ISOTOPES OF BIOGENIC SILICA – NEW PROXIES FOR RECONSTRUCTING PLEISTOCENE CHANGES IN WATER MASS STRUCTURES AND NUTRIENT UTILIZATION IN THE POLAR NORTH PACIFIC (SO202-INOPEX)
301
their origin. Wherever we record habitants (traces of life) we trace habitation (paleosols). Evolution of soils and biota may be understood as an evolution of ecosystems, that is a new paradigm for geosciences (Zavarzin, 1995). Co-evolution of life and soils is a large-scale biogeochemical succession with an increased role of biological cycles in a geological cycle. Paleosols record a broad number of parameters (qualitative and increasing number of quantitative) and environmental links of former ecosystems, even if bio fossils are extinct. Co-evolution is especially obvious for revolutionary changes in weathering, like oxygenation of the atmosphere, radiation of higher plants and grasses. Paleosols comprise the major record in Quaternary terrestrial archives and are in the center of such multidisciplinary challenges like global climate change, carbon sequestration and cryobiosphere. Considerable part of present-day pedosphere consists of surface paleosols with their profiles keeping record of final stages of sedimentation and former environments. TRANSBOUNDARY FACTOR EFFECT ON MANAGEMENT IN THE AMUR RIVER BASIN
WATER
RESOURCE
Edith Maier. Alfred Wegener Institute, Germany E-mail address: [email protected]
Stable oxygen (d18O) and silicon (d30Si) isotopes of biogenic silica (diatoms and radiolarians) will be analysed on opal-rich sediments from the Patton Seamounts (SO202-27-6), Gulf of Alaska. This new methodological approach will be used to get new insights in the hydrography and nutrient utilization of the polar North Pacific on glacial-interglacial timescales. The studied core records the time since the last glacial period. Dating will be based on a combination of AMS-14C measurements and isotope stratigraphy on foraminifera. Combined d18O-analyses on surface dwelling photosynthetic diatoms and deeper living heterotrophic radiolarians shall provide information on surface water hydrography, especially on changes in salinity and surface water stratification. The Gulf of Alaska has been the catchment area of glaciers from the North American Cordilleran Ice Sheet during the last glacial. By reconstructing its salinity history meltwater events from the Cordilleran Ice Sheet may be identified, which might help decipher the influence of (de)glacial meltwater input on water mass structures in the polar North Pacific. Diatom ?30Si-analyses will be used to gain information on local surface water silicic acid utilization and the marine silicon cycle on glacial-interglacial timescales. Being the main siliceous constituent in marine polar sediments, dominating the modern marine silicon cycle and playing an important role in the modern polar North Pacific all makes diatoms the ideal candidates for paleo-nutrient studies. The newly developed method allows routine measurements of d18O- and d30Si- values from the same aliquot and enables a coupled interpretation of both proxies. This is particularly important concerning a possible connection between water mass structure and nutrient utilization. Along with other paleoceanographical proxies, d18O-and d30Si-studies add to a comprehensive understanding regarding past ocean circulation and nutrient utilization in the polar North Pacific.
A. Makhinov. Institute of Water and Ecology Problems FEB RAS, Russian Federation E-mail address: [email protected]
Management of water-resource systems becomes very important in the natural resource system of the eastern regions of Russia. Due to the geographical location of the Amur Basin significant amounts of river water and atmospheric precipitation are transported across the country borders. 260 km3 of the Amur runoff are formed in the Russian part of the basin and 105 km3 are formed in China and Mongolia, which means that 46.2% of river water come to Russia from the neighboring countries. Hydropower stations cause most changes of the hydrological regime. There are three major hydropower stations in the Amur Basin: one in China and two in Russia. They regulate 10% of the basin area. However, the water regime of the Middle and Lower Amur has changed significantly and the conditions of navigation and operations of municipal water intakes became more difficult. Transboundary impacts on the Amur hydrological regime should be considered to manage ecological problems in the Amur Basin more effectively. One of the processes, which hampers economic activities in the basin, is a constant redistribution of water flow between sub-channels coupled with highly intensive river-bed deformations. These processes tend to accelerate in the river passages near the cities and at the junctures of big tributaries, where many factors affect the river regime. Waterworks make water resource management in the Amur Basin highly effective. The construction of overflow dams at the entrance of Pemzenskaya and Beshenaya sub-channels improved the river-bed situation near Khabarovsk. The temporal dam that blocked the Kazakevicheva (Amurskaya) subchannel was very effective to prevent further pollution of the river after the technogenic accident on the Sungari River in 2005. Big water reservoirs in Russia may be used as additional water supplies to mitigate negative consequences in the mostly ecologically vulnerable Lower Amur.
PALEOPEDOLOGY: NEW MEANING FOR GEOSCIENCES
IMPACT OF THE ENVIRONMENT ON NOMAD MIGRATIONS IN THE NORTHERN BLACK SEA REGION
Alexander Makeev. Institute of ecological soil science, Moscow Unive, Russian Federation
Sergey Makhortykh. Institute of Archaeology Ukrainian Academy of Scie, Ukraine
E-mail address: [email protected]
E-mail address: [email protected]
Due to recent advances paleopedology is absorbing many branches in soil science and other geosciences. Modern soilscape is one of innumerable temporal cuts in the evolution of pedosphere from Precambrian to Holocene. The role of paleosols in the evolution of bio-geosphere cycles is based on the fact that more than 90% of all living organisms occur in soils. Biogeochemical record extends far beyond the existing definition of paleosol and includes, following Vernadski, all products influenced by terrestrial biota that constitute pedolithosphere (after Glazovskaya: terrestial sedimentary rocks, weathering crusts, etc., being paleosols, transformed in geo-cycles). Actually paleopedology is a science studying pedolithospheres of the past. With this approach we have continuous record in which newly discovered paleosols are enclosed like new cells in the periodic table. Paleosols determine biosphere-geosphere cycles from
The beginning of the 1st millennium BC was characterized by the formation of nomad pastoralism throughout the Eurasian steppes. It was connected with a long climate aridity, which began in the Pontic region about the 11th century BC. The collapse of such the late Bronze Age cultures as the Belozerka and Post-Srubnaya ones with their mixed pastoral-agricultural economy was a result of this ecological crisis. Early nomads created their own economic system – cattle breeding with horizontal and vertical migrations, in which the structure of herds was basically formed of horses and sheep. At the same time, the transition to nomadism in the different regions of Eurasia had local distinctive features, which promoted the emergence of diverse cultural formations. During the period of increasing climate aridity and decreasing steppe productivity, the nomadic economy experienced a crisis, too. A part of the
302
Abstracts / Quaternary International 279-280 (2012) 233–345
population was forced to leave the Pontic steppe and to move into areas with wetter climate: in the first place - the Dnieper forest-steppe zone and the Northern Caucasus. These new cultural centers played an important role in the history of Eastern Europe within the Early Iron Age. The Cimmerians and Scythians concentrated in these areas mainly during the aridity and penetrated to the south of the Pontic steppe during humidity of climate. The archaeological materials allow us to reconstruct the nomadic economy with horizontal season movements along the Black Sea and Azov Sea shores during weak period of damping of climate and predominance of vertical season movements during long dry period.
the highly centralised Achaemenid state (4th c. BC). Our findings support the hypothesis that they were built instead by the non-centralised and loosely organised Kushan society.
HURRICANES AND CLIMATE IN THE CARIBBEAN DURING THE PAST 3700 YEARS B.P
Subtropical regions are key areas to understand the dynamics of the subtropical anticyclones in the past. However, there is a lack of paleoclimatic information from these areas due mainly to the scarcity of sites to obtain suitable fossil records. In the semiarid zone of Chile (32oS) the presence of swamp forests provide an excellent fossil record to evaluate changes in precipitation linked to the Southern Westerlies wind belt which is modulated in this zone by the annual and interannual dynamic of the South-East Pacific subtropical anticyclone. We present a palaeoenvironmental and palaeoclimatic reconstruction of the semiarid coast of Chile since 13,000 yrs BP. based on the joint analysis of pollen, charcoal and oxygen isotopes (shells) records from swamp forests and archaeological sites. Furthermore, the broad archaeological record allowed comparing human occupations since the first inhabitants to environmental changes. Wet conditions in the area during the Late Pleistocene were followed by a series of dry and wet phases in the early Holocene that recorded the driest period for the whole Holocene between 7700-6200 years BP. Subsequently, the environmental conditions seem to have been gradually more humid with little reversal dry periods between 3000-2000 yrs BP. High proportions of the humidity indicator Myrtaceae between 2000-700 yrs BP suggest a wet general context. Between 550-300 yrs BP, there is a decrease in the humidity indicators which may correspond either to climate or anthropic activity. The charcoal record suggests that the fire dynamics in the area was more strongly associated with human activity than to climate variability. In fact, the largest amounts of charcoal particles were recorded simultaneously with some important cultural events such as the shift from the hunter-gatherer period to the ceramic one and the European settlement. On the other hand, human occupations tend to be more stable during the most humid phases.
Bruno Malaizé. Université Bordeaux I / EPOC, France E-mail address: [email protected]
A multiproxy analysis of lacustrine sediments cored in Grand-Case Pond at Saint-Martin, north of the lesser Antilles archipelago, reveals three distinct climatic periods for the last 3700 years. From 3700 to w2500 a cal. BP and from 1150 a cal. BP to the present, carbonate mud deposition occurred in connection with pond lowstands. These periods were also punctuated by severe drought events, marked by gypsum laminae, and high intensity hurricane landfalls. The intermediate time interval, from 2500 to 1150 a cal. BP, is typified by black organic mud deposition suggesting hypoxic to anoxic conditions which are probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today. The carbon isotopic composition of the ostracod Perissocytheridea bisulcata confirms this pond sedimentation model. Such a climatic history agrees closely with that documented from other records in the Caribbean area, such as the Cariaco Basin, paleo archives from the Yucatan Peninsula or the Barbados. By contrast, discrepancies seem to emerge from the comparison between hurricane activity and paleoclimate history recorded at Saint-Martin on the one hand and Vieques (Puerto Rico) on the other hand. We explain this apparent contradiction by a balance between two distinct storm paths in response to latitudinal shifts of the Inter-tropical Convergence Zone (ITCZ). Stronger storm activity over the Gulf coast and the inner Caribbean Sea is favoured by a southern position of the ITCZ in connection with dryer climatic conditions.
LATE PLEISTOCENE- HOLOCENE CLIMATIC CHANGES AND HUMAN OCCUPATION IN SUBTROPICAL SEMIARID REGION OF CHILE (32OS) Antonio Maldonado. Universidad de La Serena - Centro de Estudios Avan, Chile E-mail address: [email protected]
POLITICAL POWER AND CLIMATIC VARIABILITY IN WESTERN CENTRAL ASIA; RESULTS FROM A GEOARCHAEOLOGICAL STUDY IN SAMARKAND, UZBEKISTAN
PALEOSEISMIC AND PALEO-TSUNAMI SIGNATURES FROM THE WEST COAST OF SOUTH ANDAMAN, A&N ISLAND, INDIA
Luca C. Malatesta. ETH Zurich, Switzerland
E-mail address: [email protected]
Javed N. Malik. Indian Institute of Technology, Kanpur, India E-mail address: [email protected]
The dense human History of the Central Asian Silk Road provides us with a rich insight in the social, political as well as climatic development of the region. Several archaeological sites document the various irrigation schemes that were designed to support human presence in and around the Tian Shan during the arid late Holocene (ca. 300 BC - 500 AD). This is particularly striking in the Zeravshan Valley in Uzbekistan. From the 4th c. BC onwards, it was one of the Silk Road main paths and extensive irrigation works were engineered to sustain the agriculture around the historical city of Afrosiab, now Samarkand. The irrigation system upstream of the historical city of Afrosiab consisted of two main canals, the Dargom and the Jangi Aryk. We studied deposits of a destructive flood, found in a particularly well studied dwelling next to the Dargom, with sedimentological and surface processes methods. We thus obtained original constraints on the nature of extreme precipitation events at this time (16080 AD, 14C dating). We estimated that an intense precipitation event of at least 65 mm/h for at least 2 hours allowed for a 0.6 m high flooding of the archaeological site based on a numerical model surface overland flow. Elevated dwellings, the usual construction type in the valley at this time and the recurrence of flood horizons in the stratigraphy attest a repetition of floods during the first centuries AD in western Central Asia. We also established a new precise quantitative timeframe for the canals construction time. XRD analysis of the flood-related sediments and further radiocarbon ages confirmed the presence of the two canals in the 2nd c. AD. Furthermore, we could discredit the idea that the canals were a product of
Sediment succession from west coast of Andaman Island around Collinpur (site-1) and Collinpur-4 (site-2) village suggests that the coarse sand+broken shell fragments (unit a) from site-2 is the oldest tsunami (?) deposit (Event I), capped by a peaty unit (unit b). Unit c with coarse sand+broken shells, suggest another tsunami (Event II). This unit is capped by a weak-strongly developed peaty unit d. A thick (28 cm) yellowish coarse sand unit e marks penultimate tsunami event (Event III). Similar w30 cm thick tsunami deposit comprising coarse sand with gravel fragments (corals, shells, rock clasts etc.) in swale portion, and coarse sand+broken shells, peaty material and rip-up clasts of soil on the backlimb of the beach ridge was also identified at site-1. This unit shows sharp contact with underlying peaty unit d. Overlying unit f with partially developed peaty layer suggests probable uplift during Event-III. The couplets of peaty units (b, d and f) representing marshy environment and tsunami (?) sand (units a, c and e) suggests marginal land-level change occurred. Overlying silty-clay (unit g) suggests sub-tidal environment; change from marshy – Event-IV. Thick silty-sand unit (unit h) and overlying humic soil (unit i) of 2004 indicates land-level change, suggesting a gradual uplift during inter-seismic period. Medium to coarse yellowish sand (Unit j) with prominent laminations and sharp contact with unit i marks deposition during 2004 Sumatra-Andaman earthquake (Event-V). AMS ages suggest that Event-I marked by tsunami deposits occurred before 800 AD and Event-II at around 687-877 AD, Event-III 1200-1300 AD with marginal uplift (?) and tsunami deposition; Event-IV marked by subsidence occurred during 1300-1800 AD. It is inferred that the gradual