- Email: [email protected]
Holocene Mangrove Dynamics and Environmental Changes in the Coastal region of South Western Nigeria
360
Abstracts / Quaternary International 279-280 (2012) 346–461
present 76 new AMS14C dates of planktonic foraminifera covering Marine Isotope Stage 3 from the LINK15 core taken from the Faroe-Shetland channel. The Faroe-Shetland channel is situated in the main path of the warm North Atlantic Drift current and further provides an escape route for the cold Norwegian Sea Deep Water. Hence LINK15 has an ideal position for studying paleo variability of 14C reservoir ages. Based on N. Pachyderma d18O, magnetic susceptibility and IRD the LINK15 sediment core has been correlated to the NGRIP ice core (GICC05 age scale). The correlated GICC05 ages of the LINK15 sediment core are then used to calculate marine reservoir ages (DR) using the marine radiocarbon calibration curve (Marine09). Our results show significant DR variability through the course of 6 D-O events. MAJORCA CAVES, SEA-LEVEL CHANGES, AND ASTRONOMICAL FORCING Bogdan P. Onac. Department of Geology, University of South Florida, United States E-mail address: [email protected]
The littoral caves of Mallorca have formed by the mixing of freshwater and seawater in the coastal phreatic zone, and are highly decorated with speleothems that formed during Quaternary time when the caves were airfilled chambers. Throughout the middle and upper Pleistocene, the caves were repeatedly flooded by glacio-eustatic sea level oscillations. The water level of each flooding event was recorded by a distinct encrustation (also known as phreatic overgrowths on speleothems, POS) of calcite or aragonite over existing speleothems and along cave walls. We have identified several well-defined encrustation horizons below and above the present-day sea level corresponding to older sea level events. Sea level chronologies based on POS that formed at the water table avoid at least three of the major problems encountered when reconstructing past sea level using corals: 1) assumptions about the water depth above the reef, 2) questions concerning the provenance of corals, and 3) uncertainties regarding the relationship between sea level position and the timing of coral reef or terrace formation. The carbonate encrustation mechanism allows for sub-meter sea level precision of documenting past sea levels. Using high-precision U/Th ages on the Mallorcan POS, we pinpoint western Mediterranean sea level at w1 m above modern at w81 ka during marine isotope stage (MIS) 5a. Dates of 116 and 121 ka (MIS 5e) on encrustations from the same cave at an elevation of 2.6 m imply that the w1 m highstand during MIS 5a primarily represents eustatic ice equivalent sea level, and has been negligibly affected by tectonic and isostatic effects. Our findings corroborate the minority view that MIS 5a was at least as ice-free as present. If, indeed, sea level was higher than present at 81 ka as our data suggests, the apparent 100 ka ice-age cycle seen to dominate the last 700 ka in deep sea sediments may not apply so directly to the growth and decay of the Quaternary ice sheets. MIDDLE STONE AGE EXPOSURES AT MORICHO, NEAR KILOMBE, KENYA Isaya Onjala. National Museums of Kenya, Kenya E-mail address: [email protected]
The extinct early Pleistocene volcano of Kilombe, Kenya, is the focus of several suites of sediments. At Moricho 2km NW of the main Kilombe Acheulean site, Middle and Upper Pleistocene sediments are found extending in a series of spectacular amphitheatre-like exposures. In initial exploration these have yielded MSA (Middle Stone Age) points on the surface, of both obsidian and lava; and also occasional flakes in situ, again including finds of lava as well as obsidian. The sediments are largely ‘red beds’, composed of thin tuffs and interposed weathering products, deriving in part from the slopes of the Kilombe volcano. In one case artefacts have been found between tuffs separated by as little as 60 cm, offering the prospect of studying assemblages with high stratigraphic resolution. At the base of the Moricho sequence a thick tuff resembles the ashflow tuff capping the Acheulean site exposures. A similar massive tuff also occurs within the caldera or crater of the Kilombe volcano, there overlying a series of lacustrine sediments. The poster gives details of stratigraphy, artefacts and sediment sampling.
OBSIDIAN EXPLOITAION AND PALAEOECOLOGY OF THE JAPANESE ISLANDS DURING MIS3 AND MIS2 Akira Ono. Meiji University, Japan E-mail address: [email protected]
Explicit evidence of human occupation that has based both on stratigraphy and morpho-typology of lithic artifacts is possible to trace back to the middle of MIS3 in the Japanese islands. The presentation focuses on obsidian exploitation patterns in the Kozu island, and the Mattobara Upper Palaeolithic site on the mountainous river terrace, with reference to the climatic changes during 70ka – 10ka from the boring data of the Lake Nojiri, Central North Japan. Generally, lithic assemblages continue from uppermost Palaeolithic Layer down to the Layer X in Kanto area, but a single artifact is available beneath the Layer X. This suggests the first peopling of the Japanese islands connected with this time period, ca. 38000 cal BP. The earliest evidence of obsidian procurement from Kozu island, was recognized in the Layer VII (Black band) of Ashitaka area dated as ca. 38000 cal BP. No land bridge was formed between Izu islands and Honshu, and also between Korean peninsula and Japanese islands even in the LGM. This implies a possibility of human migration from Asian mainland to the Japanese islands across the seawater in the middle of MIS3. Obsidian raw material exploitation strategy in the Upper Palaeolithic has been modeled in various ways. First, long distance direct procurement; second, indirect procurement through exchange network systems; and third, the raw material is programmed in the year-round scheduled socalled as an embedded strategy. Even though no single integrated explanatory model may applicable, raw material exploitation strategies are reflecting the different environmental settings of mountainous and isolated islands. POSTGLACIAL DETRITAL SEDIMENT SOURCES AND TRANSPORT PROCESSES IN LAKE DONGGI CONA, NORTHEASTERN TIBETAN PLATEAU, REVEALED BY MULTIVARIANTE STATISTICAL ENDMEMBERMODELLING (EMMA) OF SEDIMENTOLOGICAL DATA Stephan Opitz. Alfred Wegener Institute for Polar and Marine Rese, Germany E-mail address: [email protected]
Donggi Cona is a 95 m deep fresh-water lake, situated on the north-eastern Tibetan Plateau at an elevation of 4090 m a.s. The intramontane lake basin is part of several pull-apart structures associated with the east west oriented Kunlun Fault. The region is influenced by monsoonal air-mass systems of different origin, highly variable in space and time. The main objective of our joint Chinese-German research is the reconstruction of palaeoenvironmental changes of Lake Donggi Cona and its catchment area during the last 18-20 kyr. Here we report on the temporal variability of detrital sediment fluxes to the lake, as recorded in five up to 6.4 m long sediment cores, retrieved from water depths between 40 and 2 metres. To understand climate-related processes in the lake system, it is necessary to recognize the different sediment sources and modes of sedimentary transport into the lake. The study builds on a multi-proxy approach, using grain size, XRF, XRD, CNS and TOC data. With an end-member modelling algorithm (EMMA), based on principal component analyses and factor analyses, we separate (“unmix”) the multimodal distributed grain-size classes into several unimodal-process-classes. Empirical end-members are derived and compared to natural end-members, i.e. terrestrial surface samples from locations dominated by a single geomorphological process regime or sediment source. We present the results of this “unmixing” approach in relation to the interpretation of the sedimentological, mineralogical and geochemical findings of Lake Donggi Cona. HOLOCENE MANGROVE DYNAMICS AND ENVIRONMENTAL CHANGES IN THE COASTAL REGION OF SOUTH WESTERN NIGERIA Emuobosa Akpo Orijemie. University of Ibadan, Nigeria E-mail address: [email protected]
An 8m-core drilled in Ikorigho in the coastal region of South-Western Nigeria, has provided evidence of Holocene mangrove dynamics and
Abstracts / Quaternary International 279-280 (2012) 346–461
environmental changes. The pollen and spore assemblages indicate that the vegetation throughout the core was characterized by mangrove swamp forest (MSF) dominated by Rhizophora spp., Avicennia and Acrostichum aureum; Freshwater swamp forest (Uapaca, Mitragyna ciliata and Symphonia globulifera) and few lowland rainforest taxa (Celtis cf. brownii, Pycnanthus angolensis). However, there were certain periods when marked reductions in Rhizophora almost always coincided with upsurge in Poaceae and Cyperaceae. This was indicative of prevailing drier climate, and possibly lowered relative sea level. But unlike the vegetation changes noted for Ahanve in the South-westernmost part of Nigeria where the mangrove swamp forest became reduced and completely disappeared ca. 3100yrs B.P., Rhizophora spp. at Ikorigho recovered, and remain the dominant taxa in the vegetation at the study area. The anthracological results reveal few charcoal particles at the lowest sections, and significant increase in charcoal particles in the topmost sections of the core. These anthracological details provide evidence of a relatively recent history of human interactions with, and impacts on the MSF at Ikorigho. This is in sharp contrast to that noted for Ahanve, South-westernmost part of Nigeria where human occupation there is at least 3000yrs old, and the disappearance of the MSF is partly attributed to human activities such as tree felling, bush burning and agriculture. SEASONAL RESOLUTION OF EASTERN MEDITERRANEAN CLIMATE CHANGE SINCE 34 KA FROM A SOREQ CAVE SPELEOTHEM Ian J. Orland. University of Wisconsin, United States E-mail address: [email protected]
Ion microprobe analysis of d18O in Soreq Cave (Israel) stalactite sample 2N (U-Th-dated, 34-4 ka) provides new information about regional climate and seasonality. We use the WiscSIMS CAMECA 1280 ion microprobe to measure d18O at sub-annual resolution (10 mm spots) with a precision of w0.3& (2 SD) and confocal laser fluorescence microscopy (CLFM) to image growth bands. Combined analyses of d18O and CLFM show that couplets of bright and dark fluorescent calcite in Soreq speleothems represent annual growth bands. The fluorescence is caused by organic molecules (e.g. humic acid) that, in the Holocene, flush into the cave during the annual wet season. Values of d18O (n¼1223) along a radius of sample 2N reveal: 1) long-term climate changes over the last 34 ka, and 2) rapid climate changes during the last deglaciation, in particular, at the onset and termination of the Younger Dryas (YD). A quantitative measure of seasonality (D18O ¼ jd18O[dark calcite] – d18O[bright calcite]j in a single band) in 187 annual bands also reveals both long-term trends and abrupt changes. The mean value of D18O decreases from 1.0& prior to the YD to 0.7& for the Holocene (>99% confidence mean values not equal). The change in D18O correlates with a shift in the fluorescent patterns of annual bands; the fluorescence of calcite formed prior to the YD is consistently reversed within an annual band (dark precedes bright) relative to Holocene bands (bright precedes dark). Coupled differences in D18O and fluorescence are likely caused by changes in seasonal rainfall patterns, vegetation, organic acid production, or winter snow-cover. Both the onset and termination of the YD are marked by distinct shifts in the d18O of bright calcite, suggesting rapid (decadal-scale) changes in rainfall amount. Values of d18O in dark calcite also shift at the YD, but lag the changes in bright calcite due to cave hydrology. PALAEOGENOMICS AND TRUE SINGLE MOLECULE SEQUENCING Ludovic Orlando. Natural History Museum of Denmark, Copenhagen Univ, Denmark E-mail address: [email protected]
Ancient DNA offers the unique opportunity to literally catch evolution redhanded by accessing to the genetic information of past individuals. While most paleogenetic studies have focused on short hypervariable mitochondrial fragments, second-generation sequencing technologies have open the way to large-scale analyses of the nuclear genome, giving rise to the brand-new field of palaeogenomics. At the same time, second-generation sequencing technologies have revealed biochemical features of
361
ancient DNA molecules shedding light on the process of post-mortem DNA decay. Based on these data, the first reliable in silico models of DNA degradation have been developed which provided a statistical framework for evaluating data accuracy as well as new criteria for assessing ancient DNA authenticity. Here we will present how we take advantage of a thirdgeneration sequencing technology to sequence the complete genome of a Pleistocene mammal. Current data confirm some features of ancient DNA molecules but at the same time reveal specific characteristics that could not have been detected by second-generation sequencing. A comparative genomic analysis of the modern reference and this pre-domesticated genome is expected to identify the genetic changes that were specifically selected in the course of domestication. A RECORD OF STORMINESS FROM THE BRITISH ISLES COVERING THE LAST 4,400 YEARS Lisa Orme. Exeter University, United Kingdom E-mail address: [email protected]
Future anthropogenic climate forcing is forecast to increase storm intensity and frequency over the Atlantic through its influence on the North Atlantic Oscillation (NAO) and other modes of climatic variability. However, understanding the significance of such an increase is difficult since the natural variability in the frequency of storm events beyond the range of instrumental data is poorly known. Empirical knowledge of longer-term extreme variations in climate will also aid GCM model calibration because large-scale boundary conditions during the Late Holocene were similar to modern conditions (AD1963-1990) and the influence of orbital forcing is well understood. Here, we present a record of storminess covering the Late Holocene based on a 4 m long peat core taken from Cors Fochno in mid-Wales, UK. The 4400 year record encompasses several periods of known climatic variability; namely the Medieval Climate Anomaly, the Little Ice Age and the last three Holocene Bond Events (1500 yr cycle). The record has been sampled at 1 cm intervals giving a decadal resolution. Storminess is indicated by variations in the minerogenic content (ignition residue) and the Aeolian Sediment Influx (ASI). Eleven episodes of enhanced storm activity are identified in the period covered by the core. The elemental composition of this core has also been analysed using an XRF core scanner, giving a far higher resolution (200mm) than was possible by subsampling, and an assessment is made of XRF scanning as a potential technique for providing a proxy record of storminess. AMINO ACID RACEMIZATION RATES IN DIFFERENT GENERA OF OSTRACODES José E. Ortiz. Biomolecular Stratigraphy Laboratory, E.T.S.I.Mina, Spain E-mail address: [email protected]
Ostracodes have certain characteristics that make them particularly useful for amino acid racemization dating. Among these, they show excellent preservation and abundance of amino acids in their valves, thus allowing the analysis of a small sample size (even a single ostracode valve w0.01 mg) compared with that required for other organisms, e.g. molluscs (5 mg), probably because ostracode valves are made of low-magnesiumcalcite, which is a more stable mineral than aragonite. Thus, analysis of many samples from a single bed allows anomalous results to be identified and time-averaging of the dated event to be calculated. Monogeneric samples are necessary in order to reduce taxonomically controlled variability in D/L ratios, as amino acid racemization is known to be a genus-dependent process (together with time and temperature). However, different ostracode genera are generally used together to establish the age of the same locality, assuming slight differences between D/L ratios in distinct genera. To quantify the differences between the amino acid racemization ratios of the four main ostracode genera present in sediments from the Iberian Peninsula, we performed an extensive study including 43 localities. Our results show that Herpetocypris shells had slightly higher aspartic acid D/L ratios than Candona specimens in younger localities (D/L<0.25; <40ka), while values from 0.25 to 0.45 (40-220 ka), differences increased to 0.05 or
Abstracts / Quaternary International 279-280 (2012) 346–461
present 76 new AMS14C dates of planktonic foraminifera covering Marine Isotope Stage 3 from the LINK15 core taken from the Faroe-Shetland channel. The Faroe-Shetland channel is situated in the main path of the warm North Atlantic Drift current and further provides an escape route for the cold Norwegian Sea Deep Water. Hence LINK15 has an ideal position for studying paleo variability of 14C reservoir ages. Based on N. Pachyderma d18O, magnetic susceptibility and IRD the LINK15 sediment core has been correlated to the NGRIP ice core (GICC05 age scale). The correlated GICC05 ages of the LINK15 sediment core are then used to calculate marine reservoir ages (DR) using the marine radiocarbon calibration curve (Marine09). Our results show significant DR variability through the course of 6 D-O events. MAJORCA CAVES, SEA-LEVEL CHANGES, AND ASTRONOMICAL FORCING Bogdan P. Onac. Department of Geology, University of South Florida, United States E-mail address: [email protected]
The littoral caves of Mallorca have formed by the mixing of freshwater and seawater in the coastal phreatic zone, and are highly decorated with speleothems that formed during Quaternary time when the caves were airfilled chambers. Throughout the middle and upper Pleistocene, the caves were repeatedly flooded by glacio-eustatic sea level oscillations. The water level of each flooding event was recorded by a distinct encrustation (also known as phreatic overgrowths on speleothems, POS) of calcite or aragonite over existing speleothems and along cave walls. We have identified several well-defined encrustation horizons below and above the present-day sea level corresponding to older sea level events. Sea level chronologies based on POS that formed at the water table avoid at least three of the major problems encountered when reconstructing past sea level using corals: 1) assumptions about the water depth above the reef, 2) questions concerning the provenance of corals, and 3) uncertainties regarding the relationship between sea level position and the timing of coral reef or terrace formation. The carbonate encrustation mechanism allows for sub-meter sea level precision of documenting past sea levels. Using high-precision U/Th ages on the Mallorcan POS, we pinpoint western Mediterranean sea level at w1 m above modern at w81 ka during marine isotope stage (MIS) 5a. Dates of 116 and 121 ka (MIS 5e) on encrustations from the same cave at an elevation of 2.6 m imply that the w1 m highstand during MIS 5a primarily represents eustatic ice equivalent sea level, and has been negligibly affected by tectonic and isostatic effects. Our findings corroborate the minority view that MIS 5a was at least as ice-free as present. If, indeed, sea level was higher than present at 81 ka as our data suggests, the apparent 100 ka ice-age cycle seen to dominate the last 700 ka in deep sea sediments may not apply so directly to the growth and decay of the Quaternary ice sheets. MIDDLE STONE AGE EXPOSURES AT MORICHO, NEAR KILOMBE, KENYA Isaya Onjala. National Museums of Kenya, Kenya E-mail address: [email protected]
The extinct early Pleistocene volcano of Kilombe, Kenya, is the focus of several suites of sediments. At Moricho 2km NW of the main Kilombe Acheulean site, Middle and Upper Pleistocene sediments are found extending in a series of spectacular amphitheatre-like exposures. In initial exploration these have yielded MSA (Middle Stone Age) points on the surface, of both obsidian and lava; and also occasional flakes in situ, again including finds of lava as well as obsidian. The sediments are largely ‘red beds’, composed of thin tuffs and interposed weathering products, deriving in part from the slopes of the Kilombe volcano. In one case artefacts have been found between tuffs separated by as little as 60 cm, offering the prospect of studying assemblages with high stratigraphic resolution. At the base of the Moricho sequence a thick tuff resembles the ashflow tuff capping the Acheulean site exposures. A similar massive tuff also occurs within the caldera or crater of the Kilombe volcano, there overlying a series of lacustrine sediments. The poster gives details of stratigraphy, artefacts and sediment sampling.
OBSIDIAN EXPLOITAION AND PALAEOECOLOGY OF THE JAPANESE ISLANDS DURING MIS3 AND MIS2 Akira Ono. Meiji University, Japan E-mail address: [email protected]
Explicit evidence of human occupation that has based both on stratigraphy and morpho-typology of lithic artifacts is possible to trace back to the middle of MIS3 in the Japanese islands. The presentation focuses on obsidian exploitation patterns in the Kozu island, and the Mattobara Upper Palaeolithic site on the mountainous river terrace, with reference to the climatic changes during 70ka – 10ka from the boring data of the Lake Nojiri, Central North Japan. Generally, lithic assemblages continue from uppermost Palaeolithic Layer down to the Layer X in Kanto area, but a single artifact is available beneath the Layer X. This suggests the first peopling of the Japanese islands connected with this time period, ca. 38000 cal BP. The earliest evidence of obsidian procurement from Kozu island, was recognized in the Layer VII (Black band) of Ashitaka area dated as ca. 38000 cal BP. No land bridge was formed between Izu islands and Honshu, and also between Korean peninsula and Japanese islands even in the LGM. This implies a possibility of human migration from Asian mainland to the Japanese islands across the seawater in the middle of MIS3. Obsidian raw material exploitation strategy in the Upper Palaeolithic has been modeled in various ways. First, long distance direct procurement; second, indirect procurement through exchange network systems; and third, the raw material is programmed in the year-round scheduled socalled as an embedded strategy. Even though no single integrated explanatory model may applicable, raw material exploitation strategies are reflecting the different environmental settings of mountainous and isolated islands. POSTGLACIAL DETRITAL SEDIMENT SOURCES AND TRANSPORT PROCESSES IN LAKE DONGGI CONA, NORTHEASTERN TIBETAN PLATEAU, REVEALED BY MULTIVARIANTE STATISTICAL ENDMEMBERMODELLING (EMMA) OF SEDIMENTOLOGICAL DATA Stephan Opitz. Alfred Wegener Institute for Polar and Marine Rese, Germany E-mail address: [email protected]
Donggi Cona is a 95 m deep fresh-water lake, situated on the north-eastern Tibetan Plateau at an elevation of 4090 m a.s. The intramontane lake basin is part of several pull-apart structures associated with the east west oriented Kunlun Fault. The region is influenced by monsoonal air-mass systems of different origin, highly variable in space and time. The main objective of our joint Chinese-German research is the reconstruction of palaeoenvironmental changes of Lake Donggi Cona and its catchment area during the last 18-20 kyr. Here we report on the temporal variability of detrital sediment fluxes to the lake, as recorded in five up to 6.4 m long sediment cores, retrieved from water depths between 40 and 2 metres. To understand climate-related processes in the lake system, it is necessary to recognize the different sediment sources and modes of sedimentary transport into the lake. The study builds on a multi-proxy approach, using grain size, XRF, XRD, CNS and TOC data. With an end-member modelling algorithm (EMMA), based on principal component analyses and factor analyses, we separate (“unmix”) the multimodal distributed grain-size classes into several unimodal-process-classes. Empirical end-members are derived and compared to natural end-members, i.e. terrestrial surface samples from locations dominated by a single geomorphological process regime or sediment source. We present the results of this “unmixing” approach in relation to the interpretation of the sedimentological, mineralogical and geochemical findings of Lake Donggi Cona. HOLOCENE MANGROVE DYNAMICS AND ENVIRONMENTAL CHANGES IN THE COASTAL REGION OF SOUTH WESTERN NIGERIA Emuobosa Akpo Orijemie. University of Ibadan, Nigeria E-mail address: [email protected]
An 8m-core drilled in Ikorigho in the coastal region of South-Western Nigeria, has provided evidence of Holocene mangrove dynamics and
Abstracts / Quaternary International 279-280 (2012) 346–461
environmental changes. The pollen and spore assemblages indicate that the vegetation throughout the core was characterized by mangrove swamp forest (MSF) dominated by Rhizophora spp., Avicennia and Acrostichum aureum; Freshwater swamp forest (Uapaca, Mitragyna ciliata and Symphonia globulifera) and few lowland rainforest taxa (Celtis cf. brownii, Pycnanthus angolensis). However, there were certain periods when marked reductions in Rhizophora almost always coincided with upsurge in Poaceae and Cyperaceae. This was indicative of prevailing drier climate, and possibly lowered relative sea level. But unlike the vegetation changes noted for Ahanve in the South-westernmost part of Nigeria where the mangrove swamp forest became reduced and completely disappeared ca. 3100yrs B.P., Rhizophora spp. at Ikorigho recovered, and remain the dominant taxa in the vegetation at the study area. The anthracological results reveal few charcoal particles at the lowest sections, and significant increase in charcoal particles in the topmost sections of the core. These anthracological details provide evidence of a relatively recent history of human interactions with, and impacts on the MSF at Ikorigho. This is in sharp contrast to that noted for Ahanve, South-westernmost part of Nigeria where human occupation there is at least 3000yrs old, and the disappearance of the MSF is partly attributed to human activities such as tree felling, bush burning and agriculture. SEASONAL RESOLUTION OF EASTERN MEDITERRANEAN CLIMATE CHANGE SINCE 34 KA FROM A SOREQ CAVE SPELEOTHEM Ian J. Orland. University of Wisconsin, United States E-mail address: [email protected]
Ion microprobe analysis of d18O in Soreq Cave (Israel) stalactite sample 2N (U-Th-dated, 34-4 ka) provides new information about regional climate and seasonality. We use the WiscSIMS CAMECA 1280 ion microprobe to measure d18O at sub-annual resolution (10 mm spots) with a precision of w0.3& (2 SD) and confocal laser fluorescence microscopy (CLFM) to image growth bands. Combined analyses of d18O and CLFM show that couplets of bright and dark fluorescent calcite in Soreq speleothems represent annual growth bands. The fluorescence is caused by organic molecules (e.g. humic acid) that, in the Holocene, flush into the cave during the annual wet season. Values of d18O (n¼1223) along a radius of sample 2N reveal: 1) long-term climate changes over the last 34 ka, and 2) rapid climate changes during the last deglaciation, in particular, at the onset and termination of the Younger Dryas (YD). A quantitative measure of seasonality (D18O ¼ jd18O[dark calcite] – d18O[bright calcite]j in a single band) in 187 annual bands also reveals both long-term trends and abrupt changes. The mean value of D18O decreases from 1.0& prior to the YD to 0.7& for the Holocene (>99% confidence mean values not equal). The change in D18O correlates with a shift in the fluorescent patterns of annual bands; the fluorescence of calcite formed prior to the YD is consistently reversed within an annual band (dark precedes bright) relative to Holocene bands (bright precedes dark). Coupled differences in D18O and fluorescence are likely caused by changes in seasonal rainfall patterns, vegetation, organic acid production, or winter snow-cover. Both the onset and termination of the YD are marked by distinct shifts in the d18O of bright calcite, suggesting rapid (decadal-scale) changes in rainfall amount. Values of d18O in dark calcite also shift at the YD, but lag the changes in bright calcite due to cave hydrology. PALAEOGENOMICS AND TRUE SINGLE MOLECULE SEQUENCING Ludovic Orlando. Natural History Museum of Denmark, Copenhagen Univ, Denmark E-mail address: [email protected]
Ancient DNA offers the unique opportunity to literally catch evolution redhanded by accessing to the genetic information of past individuals. While most paleogenetic studies have focused on short hypervariable mitochondrial fragments, second-generation sequencing technologies have open the way to large-scale analyses of the nuclear genome, giving rise to the brand-new field of palaeogenomics. At the same time, second-generation sequencing technologies have revealed biochemical features of
361
ancient DNA molecules shedding light on the process of post-mortem DNA decay. Based on these data, the first reliable in silico models of DNA degradation have been developed which provided a statistical framework for evaluating data accuracy as well as new criteria for assessing ancient DNA authenticity. Here we will present how we take advantage of a thirdgeneration sequencing technology to sequence the complete genome of a Pleistocene mammal. Current data confirm some features of ancient DNA molecules but at the same time reveal specific characteristics that could not have been detected by second-generation sequencing. A comparative genomic analysis of the modern reference and this pre-domesticated genome is expected to identify the genetic changes that were specifically selected in the course of domestication. A RECORD OF STORMINESS FROM THE BRITISH ISLES COVERING THE LAST 4,400 YEARS Lisa Orme. Exeter University, United Kingdom E-mail address: [email protected]
Future anthropogenic climate forcing is forecast to increase storm intensity and frequency over the Atlantic through its influence on the North Atlantic Oscillation (NAO) and other modes of climatic variability. However, understanding the significance of such an increase is difficult since the natural variability in the frequency of storm events beyond the range of instrumental data is poorly known. Empirical knowledge of longer-term extreme variations in climate will also aid GCM model calibration because large-scale boundary conditions during the Late Holocene were similar to modern conditions (AD1963-1990) and the influence of orbital forcing is well understood. Here, we present a record of storminess covering the Late Holocene based on a 4 m long peat core taken from Cors Fochno in mid-Wales, UK. The 4400 year record encompasses several periods of known climatic variability; namely the Medieval Climate Anomaly, the Little Ice Age and the last three Holocene Bond Events (1500 yr cycle). The record has been sampled at 1 cm intervals giving a decadal resolution. Storminess is indicated by variations in the minerogenic content (ignition residue) and the Aeolian Sediment Influx (ASI). Eleven episodes of enhanced storm activity are identified in the period covered by the core. The elemental composition of this core has also been analysed using an XRF core scanner, giving a far higher resolution (200mm) than was possible by subsampling, and an assessment is made of XRF scanning as a potential technique for providing a proxy record of storminess. AMINO ACID RACEMIZATION RATES IN DIFFERENT GENERA OF OSTRACODES José E. Ortiz. Biomolecular Stratigraphy Laboratory, E.T.S.I.Mina, Spain E-mail address: [email protected]
Ostracodes have certain characteristics that make them particularly useful for amino acid racemization dating. Among these, they show excellent preservation and abundance of amino acids in their valves, thus allowing the analysis of a small sample size (even a single ostracode valve w0.01 mg) compared with that required for other organisms, e.g. molluscs (5 mg), probably because ostracode valves are made of low-magnesiumcalcite, which is a more stable mineral than aragonite. Thus, analysis of many samples from a single bed allows anomalous results to be identified and time-averaging of the dated event to be calculated. Monogeneric samples are necessary in order to reduce taxonomically controlled variability in D/L ratios, as amino acid racemization is known to be a genus-dependent process (together with time and temperature). However, different ostracode genera are generally used together to establish the age of the same locality, assuming slight differences between D/L ratios in distinct genera. To quantify the differences between the amino acid racemization ratios of the four main ostracode genera present in sediments from the Iberian Peninsula, we performed an extensive study including 43 localities. Our results show that Herpetocypris shells had slightly higher aspartic acid D/L ratios than Candona specimens in younger localities (D/L<0.25; <40ka), while values from 0.25 to 0.45 (40-220 ka), differences increased to 0.05 or