- Email: [email protected]
Glacial history of northern Russia – a modern view
Abstracts / Quaternary International 279-280 (2012) 9–120
LINEARITY AND NON-LINEARITY IN TROPICAL FOREST RESPONSE TO CLIMATE CHANGE: THE MONTANE FORESTS OF CAMEROON DURING THE LAST 20 000 YEARS Chimène Assi-Kaudjhis. LSCE, France E-mail address: [email protected]
Tropical mountains are known to be both museums and cradles of biodiversity. However, their great diversity is particularly vulnerable to the combined effects of habitat fragmentation by people and climate change. They have experienced above-average warming during the last century and thus can be considered to be disproportionately sensitive to climate change compared to lowland habitats. The biological response of these ecosystems to climate change is poorly understood, in particular due to the lack of continuous, long-term, high-resolution archives. Here we present the first continuous and well-resolved pollen record of montane forest response to climate change during the past 20,000 years in Atlantic Equatorial Africa. Pollen data from Lake Bambili in the Cameroon Volcanic Line show that the forest expanded gradually in response to more favourable post-glacial climate conditions beginning at 15.5 ka, then suddenly collapsed at 3.3 ka. This dramatic switch occurred within three centuries following a long period of forest degradation starting from the “8.2 ka” event and continuing in response to superimposed climate fluctuations. These included the long-term gradual decrease of insolation, the short-term variability in El Niño/Southern Oscillation (ENSO), which progressively increased from the mid-Holocene (4), and SST changes in the tropical Atlantic. GLACIAL HISTORY OF NORTHERN RUSSIA – A MODERN VIEW Valery Astakhov. St. Petersburg State University, Russian Federation E-mail address: [email protected]
The ideas on extent and chronology of former glaciers in the huge area of northern Russia between 48 and 114oE have considerably changed over the last 15 years. Traditionally there have always been two alternative views on Pleistocene glaciation: i) the Atlantic model derived from the better studied examples of western Europe and North America, ii) the continental concept which took into account the formidable size of the Eurasian landmass and its eternally continental climate. The ice limits by geological surveys naturally gravitated towards the native continental model. However, the advent of radiometric dating in the 1960-80s pushed the scale towards the Atlantic paradigm, sometimes even in the extreme form of enormous ice sheets suggested for the LGM time. The extremist models were eagerly adopted by geophysicists who were anxious to balance sea level changes with appropriate volumes of Siberian land ice. The reverse trend started in the 1990-s when seemingly reliable 'old' finite radiocarbon dates proved to be spurious leaving extremist models without a chronological support. Since then modeled Late Weichselian ice sheets have drastically shrunk to virtually disappear east of Fennoscandia and the Barents Sea shelf. New geochronometric methods, especially optically stimulated luminescence, facilitated this process suggesting older and smaller glaciers for the Late Pleistocene. Other radiometric techniques employed in the last 5 years such as cosmogenic exposure, Th/U and ESR dating, have only deepened the continental trend in glacial thinking. The new geochronometric results have also changed the chronological position of the interglacials of the two last cycles. OSL and Th/U dating: i) proved an Eemian age of the Karginsky temperate event conventionally attributed to MIS 3 and ii) pushed the preceding interglacial with mild climate and thick peats towards MIS 7. In the modern view the really large ice sheets developed only in the more humid Middle Pleistocene. SUBSISTENCE AND THE ISOTOPIC SIGNATURE OF HERDING IN THE BRONZE AGE HEXI CORRIDOR, NW GANSU Pia Atahan. Institute for Environmental Research, Australian N, Australia E-mail address: [email protected]
The Asian millets (Panicum miliaceum and Setaria italica) have short growing seasons, are tolerant of cold and arid conditions, and are commonly cultivated in marginally arable areas of north China. Previous
27
work finds these plants to have dominated the diets of agriculturalists and livestock there at various times since the Yangshao Period (ca. 7000-5000 BP). Intensive millet cultivation in this region may have helped societies persist when climatic conditions were less agriculturally favourable, however, heavy reliance on the cereal may have affected population health, as people adopted less varied diets. Carbon and nitrogen stable isotope values for bone collagen from sites in the Hexi Corridor, dating to approximately 2292-1692 BC, are presented. The isotope results show human and most domestic omnivore fauna shared diets dominated by millet (a C4 plant), and consumed only minimal amounts of animal protein (flesh, milk or blood products). These findings contrast with the archaeological assemblages which include abundant faunal bones and hunting tools. The minimal proportions of C4 plants detected in the diets of the Bos and Caprinae sampled suggests that herded animals were mostly taken beyond the agricultural zone to graze. The wide range in herbivore d15N values (4.1& to 11.8&) indicate individual grazing ranges were varied and were probably in distinctly different ecological zones. HOLOCENE VEGETATION HISTORY IN THE NSW CENTRAL COAST OF AUSTRALIA: PHYTOLITH ANALYSIS FROM MUSSEL SHELTER, UPPER MANGROVE CREEK Val Attenbrow. Australian Museum, Australia E-mail address: [email protected]
In south-eastern Australia during the second half of the Holocene a strong correlation exists between climate proxies indicating cooler and drier conditions and the proliferation of small stone tools called backed artefacts. Production of backed artefacts increased significantly between 400035000 years BP and their production subsequently declined w1500 years BP. A causal link between the backed artefact proliferation and a climatic shift, during which climate variability increased as El Nino conditions intensified, is often hypothesised. However, there are no clear indicators as to how the environment (and thus the resources exploited by Aborigines) changed in a way that promoted this modification to stone tool assemblages. We present evidence that clarifies the nature of those changes in environmental resources. Our study focuses on Upper Mangrove Creek in the NSW central coast. Here changes in faunal assemblages were identified in late Holocene levels of three excavated rockshelter sites. Our question is whether these faunal changes were associated with vegetation shifts produced by climate change. To identify vegetation histories for this area, we analysed plant biogenic silica phytoliths and other microfossil samples from a 10,000 year stratified sediment series at Mussel Shelter. Results show an abundance of as-yet unidentified tree and few understory plant species from w10,000 to w4000 years BP. A dramatic change of vegetation then occurs. Phytoliths from younger sediments indicate a progressive opening of the canopy and increasing varieties of shrubs, forbs and grasses. A further climate signal is provided by a wet/dry index constructed from phytoliths and other microfossil hydrophilic indicators. These data show periods with high hydrophilic indicator counts between w4000 and w1500 years BP reflecting greater climatic variability during the time that backed artefact production was high. A CHIRONOMID-BASED RECONSTRUCTION OF HOLOCENE TEMPERATURE HISTORY IN THE RWENZORI MOUNTAINS (UGANDA) Leen Audenaert. Ghent University, Belgium E-mail address: [email protected]
The Rwenzori Mountains (Uganda–DR Congo) are holding one of the most extensive glaciers in tropical Africa but will probably melt completely in the next few decades. Detailed knowledge of the past climate history of East Africa may be useful to better understand the underlying drivers of climate change which potentially can be translated to the future. Postglacial retreat of the Rwenzori glaciers created numerous lakes, which have in earlier research on short sediment cores (with basal dates within or shortly after the Little Ice Age) proved to be sensitive to temperature change. High-resolution reconstructions of Holocene changes in the temperature history of tropical Africa are barely available, and associated dynamics of the Rwenzori glaciers can provide crucial insights in regional
LINEARITY AND NON-LINEARITY IN TROPICAL FOREST RESPONSE TO CLIMATE CHANGE: THE MONTANE FORESTS OF CAMEROON DURING THE LAST 20 000 YEARS Chimène Assi-Kaudjhis. LSCE, France E-mail address: [email protected]
Tropical mountains are known to be both museums and cradles of biodiversity. However, their great diversity is particularly vulnerable to the combined effects of habitat fragmentation by people and climate change. They have experienced above-average warming during the last century and thus can be considered to be disproportionately sensitive to climate change compared to lowland habitats. The biological response of these ecosystems to climate change is poorly understood, in particular due to the lack of continuous, long-term, high-resolution archives. Here we present the first continuous and well-resolved pollen record of montane forest response to climate change during the past 20,000 years in Atlantic Equatorial Africa. Pollen data from Lake Bambili in the Cameroon Volcanic Line show that the forest expanded gradually in response to more favourable post-glacial climate conditions beginning at 15.5 ka, then suddenly collapsed at 3.3 ka. This dramatic switch occurred within three centuries following a long period of forest degradation starting from the “8.2 ka” event and continuing in response to superimposed climate fluctuations. These included the long-term gradual decrease of insolation, the short-term variability in El Niño/Southern Oscillation (ENSO), which progressively increased from the mid-Holocene (4), and SST changes in the tropical Atlantic. GLACIAL HISTORY OF NORTHERN RUSSIA – A MODERN VIEW Valery Astakhov. St. Petersburg State University, Russian Federation E-mail address: [email protected]
The ideas on extent and chronology of former glaciers in the huge area of northern Russia between 48 and 114oE have considerably changed over the last 15 years. Traditionally there have always been two alternative views on Pleistocene glaciation: i) the Atlantic model derived from the better studied examples of western Europe and North America, ii) the continental concept which took into account the formidable size of the Eurasian landmass and its eternally continental climate. The ice limits by geological surveys naturally gravitated towards the native continental model. However, the advent of radiometric dating in the 1960-80s pushed the scale towards the Atlantic paradigm, sometimes even in the extreme form of enormous ice sheets suggested for the LGM time. The extremist models were eagerly adopted by geophysicists who were anxious to balance sea level changes with appropriate volumes of Siberian land ice. The reverse trend started in the 1990-s when seemingly reliable 'old' finite radiocarbon dates proved to be spurious leaving extremist models without a chronological support. Since then modeled Late Weichselian ice sheets have drastically shrunk to virtually disappear east of Fennoscandia and the Barents Sea shelf. New geochronometric methods, especially optically stimulated luminescence, facilitated this process suggesting older and smaller glaciers for the Late Pleistocene. Other radiometric techniques employed in the last 5 years such as cosmogenic exposure, Th/U and ESR dating, have only deepened the continental trend in glacial thinking. The new geochronometric results have also changed the chronological position of the interglacials of the two last cycles. OSL and Th/U dating: i) proved an Eemian age of the Karginsky temperate event conventionally attributed to MIS 3 and ii) pushed the preceding interglacial with mild climate and thick peats towards MIS 7. In the modern view the really large ice sheets developed only in the more humid Middle Pleistocene. SUBSISTENCE AND THE ISOTOPIC SIGNATURE OF HERDING IN THE BRONZE AGE HEXI CORRIDOR, NW GANSU Pia Atahan. Institute for Environmental Research, Australian N, Australia E-mail address: [email protected]
The Asian millets (Panicum miliaceum and Setaria italica) have short growing seasons, are tolerant of cold and arid conditions, and are commonly cultivated in marginally arable areas of north China. Previous
27
work finds these plants to have dominated the diets of agriculturalists and livestock there at various times since the Yangshao Period (ca. 7000-5000 BP). Intensive millet cultivation in this region may have helped societies persist when climatic conditions were less agriculturally favourable, however, heavy reliance on the cereal may have affected population health, as people adopted less varied diets. Carbon and nitrogen stable isotope values for bone collagen from sites in the Hexi Corridor, dating to approximately 2292-1692 BC, are presented. The isotope results show human and most domestic omnivore fauna shared diets dominated by millet (a C4 plant), and consumed only minimal amounts of animal protein (flesh, milk or blood products). These findings contrast with the archaeological assemblages which include abundant faunal bones and hunting tools. The minimal proportions of C4 plants detected in the diets of the Bos and Caprinae sampled suggests that herded animals were mostly taken beyond the agricultural zone to graze. The wide range in herbivore d15N values (4.1& to 11.8&) indicate individual grazing ranges were varied and were probably in distinctly different ecological zones. HOLOCENE VEGETATION HISTORY IN THE NSW CENTRAL COAST OF AUSTRALIA: PHYTOLITH ANALYSIS FROM MUSSEL SHELTER, UPPER MANGROVE CREEK Val Attenbrow. Australian Museum, Australia E-mail address: [email protected]
In south-eastern Australia during the second half of the Holocene a strong correlation exists between climate proxies indicating cooler and drier conditions and the proliferation of small stone tools called backed artefacts. Production of backed artefacts increased significantly between 400035000 years BP and their production subsequently declined w1500 years BP. A causal link between the backed artefact proliferation and a climatic shift, during which climate variability increased as El Nino conditions intensified, is often hypothesised. However, there are no clear indicators as to how the environment (and thus the resources exploited by Aborigines) changed in a way that promoted this modification to stone tool assemblages. We present evidence that clarifies the nature of those changes in environmental resources. Our study focuses on Upper Mangrove Creek in the NSW central coast. Here changes in faunal assemblages were identified in late Holocene levels of three excavated rockshelter sites. Our question is whether these faunal changes were associated with vegetation shifts produced by climate change. To identify vegetation histories for this area, we analysed plant biogenic silica phytoliths and other microfossil samples from a 10,000 year stratified sediment series at Mussel Shelter. Results show an abundance of as-yet unidentified tree and few understory plant species from w10,000 to w4000 years BP. A dramatic change of vegetation then occurs. Phytoliths from younger sediments indicate a progressive opening of the canopy and increasing varieties of shrubs, forbs and grasses. A further climate signal is provided by a wet/dry index constructed from phytoliths and other microfossil hydrophilic indicators. These data show periods with high hydrophilic indicator counts between w4000 and w1500 years BP reflecting greater climatic variability during the time that backed artefact production was high. A CHIRONOMID-BASED RECONSTRUCTION OF HOLOCENE TEMPERATURE HISTORY IN THE RWENZORI MOUNTAINS (UGANDA) Leen Audenaert. Ghent University, Belgium E-mail address: [email protected]
The Rwenzori Mountains (Uganda–DR Congo) are holding one of the most extensive glaciers in tropical Africa but will probably melt completely in the next few decades. Detailed knowledge of the past climate history of East Africa may be useful to better understand the underlying drivers of climate change which potentially can be translated to the future. Postglacial retreat of the Rwenzori glaciers created numerous lakes, which have in earlier research on short sediment cores (with basal dates within or shortly after the Little Ice Age) proved to be sensitive to temperature change. High-resolution reconstructions of Holocene changes in the temperature history of tropical Africa are barely available, and associated dynamics of the Rwenzori glaciers can provide crucial insights in regional