- Email: [email protected]
The use of lipid biomarkers from cave sediments as palaeoenvironmental indicators in South-East Asia
Abstracts / Quaternary International 279-280 (2012) 233–345
293
analyses in the sequence indicate the presence of the Blake event w 120,000 years at w75 m depth. Geochemical data including total carbon (TOC), total inorganic carbon (TIC) and C/N ratios document variations along the cores. C/N ratio permits to detect the organic matter origin and TIC variability in the carbonate production, high C/N ratios and TIC values correlate with the last interglacial. Only a few records covering the last glacial/interglacial cycles are available from the American tropics. This high altitude record will provide information of millennial variability. Presently, this study is in progress and intends to generate a high resolution record that includes pollen, charcoal, diatoms, magnetic and geochemical analysis.
pollen can provide reliable estimates of the primary climatic parameters. The application of the LWWA model to the fossil records of Chen Co Lake allowed quantitative inferences to be made about Holocene climatic changes in the southern Tibetan Plateau, suggesting that LWWA is a robust calibration method for quantitative palaeo-environmental reconstruction based on pollen data in the regions.
CLIMATIC VARIABILITY AND HUMAN IMPACT DURING THE LAST CA. 2,500 YEARS IN LAKE SANTA MARÌA DEL ORO, WESTERN MEXICO
Huayu Lu. Nanjing University, China
Socorro Lozano Garcia. Instituto de Geologia, UNAM, Mexico
Because of high relief and significant surface erosion in northeastern Qinghai-Tibetan Plateau, an entire Quaternary record of climatic changes is difficult to reconstruct. In this study, two long cores are obtained from thick loess deposits of the northeastern Qinghai-Tibetan Plateau. Both cores contain clear alternations of loess and paleosols, indicating distinct climate changes during Quaternary. The palaeomagnetic stratigraphy and optically stimulated luminescence dating results indicate that loess accumulation began approximate 2.0 Ma ago, with continuous accumulation to Holocene. Dust accumulation rates in this region are much higher than that in Chinese Loess Plateau, revealing a plentiful dust source and/or robust transport agent. Variations of magnetic susceptibility are a good proxy index of warm-wet and cold-dry periods, which are correlated with intensity of soil pedogensis. The magnetic susceptibility record reveals that a cold and dry climate dominated the northeastern Qinghai-Tibetan Plateau in the Quaternary, punctuated by warm-wet phases. The core reveals a stepwise strengthening of plateau summer monsoon, with a significant strengthening at around 1000-800 ka; the core also reveals at least 8 phases of strengthening of the plateau summer monsoon in the past 800 ka. Both cores provide evidence that strengthened warm-wet climates occurred at around 80-100 ka, 115-130 ka, 330-340 ka and 515-600 ka, which may correlate to warm and wet phases in the Qinghai-Tibetan Plateau. The palaeoclimate changes probably were regulated by the glacial-interglacial alternations in north Hemisphere. The loess sequences may contain information on advance and retreat of glaciers of the QinghaiTibetan Plateau, of which timing and extent is not well known.
E-mail address: [email protected]
In the last decades lacustrine records in central Mexico have documented changes in vegetation and lacustirne conditions interpreted in terms of climatic changes and human impact. Most of these changes have been recorded in the high altitude basins of central Mexico or in the eastern lowlands, including the Maya area; few studies have focus on western Mexico. We present pollen, charcoal, diatom and geochemical data from Santa María del Oro, a crater lake on the western Mexico lowlands (750 m asl). This lake lies in a transition zone between the arid climates of northern Mexico and the moister climates of the central highlands, has a tropical sub-humid climate (1250 mm/yr, 21 C) with a short summer rainy season related to the Mexican Monsoon. Two 9 m long sequences were collected: the SMO02 cores, with nine 14-C dates and a basal age of 600 BC and the MOLE cores, with six 14-C dates and a basal age of 2600 BC. Abundant pollen of Teosinte was recovered from ca. 2350 to 100 BC, suggesting early agricultural activity in the area, the first record of maize in the western region of Mesoamerica. Five stages of alternating moister and drier conditions have been identified; the presence of high abundance of Quercus, Eolimna minima, Amphora líbica, ostracodes and carbonates during the late Classic period (AD 650–1100) indicates that this was a time of shallow lake levels and drier conditions. The late Classic has been identified as a time of reduced moisture in other areas of Mesoamerica, where it correlates with a demographic maximum. In SMOit is until the Postclassic that the presence of charcoal particles, maize allow to infer important human impact. Since AD 1400 several drought episodes have been identified using Ti concentrations. Low percentages of Ti correlate with the drought episodes and suggest that this element it is a good indicator of runoff. These droughts are in agreement with those recorded by other proxies such as tree rings, historical documents. MODERN POLLEN DISTRIBUTIONS IN QINGHAI-TIBETAN PLATEAU AND THE DEVELOPMENT OF TRANSFER FUNCTIONS FOR RECONSTRUCTING HOLOCENE ENVIRONMENTAL CHANGES Houyuan Lu. Key Laboratory of Cenozoic Geology and Environment, China E-mail address: [email protected]
This study investigates the distribution of modern pollen assemblages in the Qinghai-Tibetan Plateau, China, based on surface soil samples collected at 1,202 sites along an altitudinal gradient of 10 – 5,500 m asl, where mean annual precipitation (MAP) ranges from 12 to 1,840 mm and mean annual temperature (MAT) from -7 to 21.5 oC. A total of 153 pollen taxa were found with relative abundances greater than 1 % in at least two samples. Canonical correspondence analysis (CCA) was used to determine the main environmental variables influencing pollen distributions. The results reveal that MAP is the most significant dominant variable. However, MAT, altitude (ALT), July temperature (MT7), and relative humidity (HHH) are also significant variables that clearly follow the gradients in the CCA ordination, suggesting that pollen assemblages probably not only reflect a single climatic parameter, but also a variety of other climatic inter-related parameters. Transfer functions, based on locally weighted weighted averaging (LWWA), were developed for MAP (R2-boot ¼ 0.89, RMSEP ¼ 109 mm), MAT (R2-boot ¼ 0.78, RMSEP ¼ 2.3oC), ALT (R2-boot ¼ 0.73, RMSEP ¼ 597m), HHH (R2-boot ¼ 0.82, RMSEP ¼ 4.5%), and July mean precipitation (MP7) (R2-boot ¼ 0.87, RMSEP ¼ 23 mm). Overall, our results confirm that
PALAEOCLIMATIC CHANGES IN NORTHEASTERN QINGHAI-TIBETAN PLATEAU REVEALED BY MAGNETOSTRATIGRAPHY AND MAGNETIC SUSCEPTIBILITY ANALYSIS OF THICK LOESS DEPOSITS
E-mail address: [email protected]
THE NEOGLACIAL HISTORY OF ROBSON GLACIER, BRITISH COLUMBIA, CANADA Brian H. Luckman. University of Western Ontario, Canada E-mail address: [email protected]
Glacier recession in the Canadian Rockies continues to reveal evidence of Holocene glacier advances prior to the Little Ice Age (LIA) maximum. Robson Glacier is unique in the Canadian Rockies with evidence of in-situ stumps overridden by three distinct glacier advances. Calendar (tree-ring dated) stumps and detrital wood with kill dates of between 1150 and 1350 A.D. represent the initial phase of the LIA at this site. Two buried forest sites were exposed close to the 1993-2000 position of the glacier snout yielding 14C-dated wood between 3300 and 3700 14C yr BP. Subsequently, wood from these two sites has been crossdated into a single chronology over 450 years. An in situ Pinus albicaulis snag ablated out of the glacier about 3km upglacier, near Extinguisher Tower at ca 2050m. Most recently wood was exposed in stream sections below a bedrock cliff, 150m below and half a km down ice of the Extinguisher site. This site contains a paleosol and logs >70cm diameter with >350 rings yielding a 14C date of 4780 +/-60 from the outermost rings. Eight of these trees crossdated to give a chronology of 560 years. The overlying till marks the earliest Neoglacial advance with in-situ material yet reported from the Rockies. The latter two events are older than Neoglacial events previously reported from sites in the Rockies at ca 2800-3000 yr BP (Peyto Advance) and 1500-1900 yr BP. THE USE OF LIPID BIOMARKERS FROM CAVE SEDIMENTS AS PALAEOENVIRONMENTAL INDICATORS IN SOUTH-EAST ASIA Natalie Ludgate. The Open University, United Kingdom E-mail address: [email protected]
294
Abstracts / Quaternary International 279-280 (2012) 233–345
Clastic cave sediments form in sheltered environments, collect material from airborne, water, and faunal sources, and are important to archaeology and palaeontology. Novel tools for palaeoenvironmental reconstruction in this context are therefore of interest to Quaternary research. This study forms the first comprehensive investigation of lipid biomarkers preserved in cave sediments. Lipid biomarkers are molecules such as plant waxes, which derive from living organisms, therefore forming a valuable tool for investigating changes in past ecosystems, independent of and complementary to existing techniques such as pollen analysis. Lipid biomarkers have been recovered from samples from two caves in Vietnam; Hang Boi, and Hang Trong. These sites which lie in the Ninh Bình province are both dominated by anthropogenic shell middens interspersed with sedimentation from windblown sands and bedrock breakdown. Hang Boi is an open cave situated at 78m a.s.l.; radiocarbon dates from charcoal from the section indicate the sediment ranges from 12,100cal. yrs. b.p. to 12,400cal. yrs. b.p. at the base, approximately 1 m depth. The second site, Hang Trong, is situated 142m a.s.l. and has two openings on opposite sides of a karst tower making it a good site to investigate airborne deposition. Radiocarbon dates from charcoal indicate the sub-surface sediment is recent and at approximately 1.5m from the surface, 18,500yrs. b.p. A wide range of compounds have been found, including those derived from plants, midden shells, and microbes. Stratigraphic sequences, covering 300 years from Hang Boi and 20,000 years from Hang Trong, demonstrate how the biomarkers change through time. Future work will focus on investigating the integrity of the proxy, especially post-depositional movement of organic molecules. To address this, compound-specific radiocarbon dating, will be used to investigate the ages of different biomarkers compared to the established chronology.
landscape records of deglaciated Pleistocene ice sheets, yet the origins of these enigmatic landforms and associated glacial geologic frameworks are not well understood. Analysis of geologic maps, subsurface framework, and surface morphology from North American glacial records show relations between forms and geology that (along with geophysics and continuity) constrain processes relevant to the subglacial origin of these features. For example, the morphologically concordant occurrence of bedrock-cored drumlins within drumlin fields provides evidence that subglacial erosional processes are necessary to their development. Aligned with similar orientations as bedrock-cored forms, drumlins and fluted forms with cores of unconsolidated sediment are a combination of erosional remnants of preexisting substrate (similar to bedrock cores) and later secondary accretionary mantle. Such a mantle is not essential to the drumlin form, but was accreted from debris-rich basal ice and/or advected subglacial sediment after the erosion of the swales that surround and created the core of the drumlins. In many areas, inter-drumlin networks of swales have a more deeply incised tunnel valley network superimposed upon them. Morphologic relations provide evidence that tunnel valley formation occurred during relatively late stages of glaciations and after drumlin formation. Drumlin form and dimensions generally do not vary in relation to proximity to tunnel valley margins, except for individual drumlins that adjoin and appear to be truncated at the margins of larger tunnel valleys. These relations indicate a transformation of erosional subglacial hydraulic conditions from a partially but not entirely distributed system (possibly linked cavity; but not sheetflow) to a more channelized regime of the tunnel valley network.
PHASES OF GLACIER RETREAT DETECTED IN ALPINE SPELEOTHEMS, UPPER GRINDELWALD GLACIER (SWITZERLAND)
EURO-MED 2K PAGES CONSORTIUM: REVIEW OF CURRENT KNOWLEDGE, AVAILABLE DATA COVERING THE PAST 2K IN THE EUROPEAN/MEDITERRANEAN AREA AND PLANS FOR MULTIPROXY INTEGRATION AND MODEL/DATA COMPARISON
Marc Luetscher. University of Innsbruck, Austria
Jürg Luterbacher. Univ. Giessen, Dept. für Geographie, Germany
E-mail address: [email protected]
E-mail address: [email protected]
Mountain valley glaciers and their sediments are prominent witnesses of climate change, responding sensitively to even small changes in meteorological parameters. Advances and retreats of the Upper and Lower Grindelwald Glaciers during the last w3 ka have been documented extensively (e.g. Holzhauser & Zumbühl, 1996; 1999). However, little is known about the early Holocene due to progressive erosion and mixing of palaeoenvironmental evidences. Here we explore a novel and continuous archive of glacier fluctuations in a cave system adjacent to the Upper Grindelwald Glacier. Four coeval stalagmites show consistent petrographic and stable isotopic changes between 9.2 and 2.0 ka which can be tied to abrupt modifications in the cave environment as a result of the closing and opening of multiple cave entrances by the waxing and waning of the nearby glacier. During periods of glacier advances, columnar calcite fabric is characterized by d18O values of about -8& indicative of speleothem growth under quasi-equilibrium conditions, i.e. only little affected by kinetic effects related to forced degassing or biogeochemical processes. In contrast, bacterially mediated calcite fabrics formed during periods of glacier minima are typical of precipitation within caves overlain by an alpine soil cover. This characteristic petrography is repeatedly observed before 5.8 ka pointing towards longer phases of glacier recession as compared to today where only scarce soil is present. Subsequent to 3.8 ka the tongue of the Upper Grindelwald Glacier was close to its Holocene maximum extent with retreat phases limited to some 20% of the total amplitude. The late 20th century was, however, characterized by massive down-wasting, reaching levels in 2010 similar or even lower than those attained during the early Holocene.
Focus 2 (Regional Climate Dynamics) of PAGES places a strong emphasis on regional studies that consider past climate dynamics on seasonal to millennial timescales and (sub) continental or ocean-basin spatial scales. The Europe/Mediterranean 2k (Euro-Med 2k) consortium reviews the current knowledge and the availability of documentary sources and high and low resolved terrestrial and marine archives covering the past two 2000 years from the European-Mediterranean area and discuss their interpretation and the prospects for their improved integration. A critical assessment of the proxies strengths and weaknesses and challenges and opportunities for climate reconstructions are presented. We also report on potential statistical methodologies that can integrate multiproxy data and that provide an estimate of the full covariance structure of the temperature and hydrologic reconstructions over the European-Mediterranean area for the past 2k, as well as diagnostic measures that indicate the utility of the different proxy time series for successful reconstruction. We will also provide preliminary analyses of new millennial long coupled climate model results and ways how to compare continental scale multiproxy climate reconstructions with coupled palaeo climate model output. The Euro-Med 2k consortium would also like to involve and integrate the wider community to share data and participate in the initiative, and the plans for the next couple of years of this group will be presented
GEOLOGIC AND GEOMORPHIC RELATIONS BETWEEN TUNNEL VALLEY NETWORKS AND DRUMLIN/FLUTE FIELDS: CONTRAINTS ON ASSOCIATED FORMATIVE SUBGLACIAL PROCESSES
Christopher Lüthgens. Freie Universität Berlin, Germany
Scott Lundstrom. U.S. Geological Survey, United States E-mail address: [email protected]
Tunnel valley networks and subglacial flow-field bedforms, including drumlin/flute fields, form common and overlapping elements within
A NEW DEGLACIATION CHRONOLOGY FOR NORTH-EASTERN GERMANY INFERRED FROM OSL DATING OF SANDUR SEDIMENTS AND A REINTERPRETATION OF SURFACE EXPOSURE AGES OF ERRATIC BOULDERS
E-mail address: [email protected]
During the last 130 years, the classification of the Weichselian Pleniglacial in north-eastern Germany has mainly been based on morphostratigraphical interpretations. In general, three main ice marginal positions are differentiated: The ice advance to the southernmost, relatively weakly developed ice marginal position of the Brandenburg phase has traditionally been ascribed to the LGM. The Frankfurt phase is usually interpreted as
293
analyses in the sequence indicate the presence of the Blake event w 120,000 years at w75 m depth. Geochemical data including total carbon (TOC), total inorganic carbon (TIC) and C/N ratios document variations along the cores. C/N ratio permits to detect the organic matter origin and TIC variability in the carbonate production, high C/N ratios and TIC values correlate with the last interglacial. Only a few records covering the last glacial/interglacial cycles are available from the American tropics. This high altitude record will provide information of millennial variability. Presently, this study is in progress and intends to generate a high resolution record that includes pollen, charcoal, diatoms, magnetic and geochemical analysis.
pollen can provide reliable estimates of the primary climatic parameters. The application of the LWWA model to the fossil records of Chen Co Lake allowed quantitative inferences to be made about Holocene climatic changes in the southern Tibetan Plateau, suggesting that LWWA is a robust calibration method for quantitative palaeo-environmental reconstruction based on pollen data in the regions.
CLIMATIC VARIABILITY AND HUMAN IMPACT DURING THE LAST CA. 2,500 YEARS IN LAKE SANTA MARÌA DEL ORO, WESTERN MEXICO
Huayu Lu. Nanjing University, China
Socorro Lozano Garcia. Instituto de Geologia, UNAM, Mexico
Because of high relief and significant surface erosion in northeastern Qinghai-Tibetan Plateau, an entire Quaternary record of climatic changes is difficult to reconstruct. In this study, two long cores are obtained from thick loess deposits of the northeastern Qinghai-Tibetan Plateau. Both cores contain clear alternations of loess and paleosols, indicating distinct climate changes during Quaternary. The palaeomagnetic stratigraphy and optically stimulated luminescence dating results indicate that loess accumulation began approximate 2.0 Ma ago, with continuous accumulation to Holocene. Dust accumulation rates in this region are much higher than that in Chinese Loess Plateau, revealing a plentiful dust source and/or robust transport agent. Variations of magnetic susceptibility are a good proxy index of warm-wet and cold-dry periods, which are correlated with intensity of soil pedogensis. The magnetic susceptibility record reveals that a cold and dry climate dominated the northeastern Qinghai-Tibetan Plateau in the Quaternary, punctuated by warm-wet phases. The core reveals a stepwise strengthening of plateau summer monsoon, with a significant strengthening at around 1000-800 ka; the core also reveals at least 8 phases of strengthening of the plateau summer monsoon in the past 800 ka. Both cores provide evidence that strengthened warm-wet climates occurred at around 80-100 ka, 115-130 ka, 330-340 ka and 515-600 ka, which may correlate to warm and wet phases in the Qinghai-Tibetan Plateau. The palaeoclimate changes probably were regulated by the glacial-interglacial alternations in north Hemisphere. The loess sequences may contain information on advance and retreat of glaciers of the QinghaiTibetan Plateau, of which timing and extent is not well known.
E-mail address: [email protected]
In the last decades lacustrine records in central Mexico have documented changes in vegetation and lacustirne conditions interpreted in terms of climatic changes and human impact. Most of these changes have been recorded in the high altitude basins of central Mexico or in the eastern lowlands, including the Maya area; few studies have focus on western Mexico. We present pollen, charcoal, diatom and geochemical data from Santa María del Oro, a crater lake on the western Mexico lowlands (750 m asl). This lake lies in a transition zone between the arid climates of northern Mexico and the moister climates of the central highlands, has a tropical sub-humid climate (1250 mm/yr, 21 C) with a short summer rainy season related to the Mexican Monsoon. Two 9 m long sequences were collected: the SMO02 cores, with nine 14-C dates and a basal age of 600 BC and the MOLE cores, with six 14-C dates and a basal age of 2600 BC. Abundant pollen of Teosinte was recovered from ca. 2350 to 100 BC, suggesting early agricultural activity in the area, the first record of maize in the western region of Mesoamerica. Five stages of alternating moister and drier conditions have been identified; the presence of high abundance of Quercus, Eolimna minima, Amphora líbica, ostracodes and carbonates during the late Classic period (AD 650–1100) indicates that this was a time of shallow lake levels and drier conditions. The late Classic has been identified as a time of reduced moisture in other areas of Mesoamerica, where it correlates with a demographic maximum. In SMOit is until the Postclassic that the presence of charcoal particles, maize allow to infer important human impact. Since AD 1400 several drought episodes have been identified using Ti concentrations. Low percentages of Ti correlate with the drought episodes and suggest that this element it is a good indicator of runoff. These droughts are in agreement with those recorded by other proxies such as tree rings, historical documents. MODERN POLLEN DISTRIBUTIONS IN QINGHAI-TIBETAN PLATEAU AND THE DEVELOPMENT OF TRANSFER FUNCTIONS FOR RECONSTRUCTING HOLOCENE ENVIRONMENTAL CHANGES Houyuan Lu. Key Laboratory of Cenozoic Geology and Environment, China E-mail address: [email protected]
This study investigates the distribution of modern pollen assemblages in the Qinghai-Tibetan Plateau, China, based on surface soil samples collected at 1,202 sites along an altitudinal gradient of 10 – 5,500 m asl, where mean annual precipitation (MAP) ranges from 12 to 1,840 mm and mean annual temperature (MAT) from -7 to 21.5 oC. A total of 153 pollen taxa were found with relative abundances greater than 1 % in at least two samples. Canonical correspondence analysis (CCA) was used to determine the main environmental variables influencing pollen distributions. The results reveal that MAP is the most significant dominant variable. However, MAT, altitude (ALT), July temperature (MT7), and relative humidity (HHH) are also significant variables that clearly follow the gradients in the CCA ordination, suggesting that pollen assemblages probably not only reflect a single climatic parameter, but also a variety of other climatic inter-related parameters. Transfer functions, based on locally weighted weighted averaging (LWWA), were developed for MAP (R2-boot ¼ 0.89, RMSEP ¼ 109 mm), MAT (R2-boot ¼ 0.78, RMSEP ¼ 2.3oC), ALT (R2-boot ¼ 0.73, RMSEP ¼ 597m), HHH (R2-boot ¼ 0.82, RMSEP ¼ 4.5%), and July mean precipitation (MP7) (R2-boot ¼ 0.87, RMSEP ¼ 23 mm). Overall, our results confirm that
PALAEOCLIMATIC CHANGES IN NORTHEASTERN QINGHAI-TIBETAN PLATEAU REVEALED BY MAGNETOSTRATIGRAPHY AND MAGNETIC SUSCEPTIBILITY ANALYSIS OF THICK LOESS DEPOSITS
E-mail address: [email protected]
THE NEOGLACIAL HISTORY OF ROBSON GLACIER, BRITISH COLUMBIA, CANADA Brian H. Luckman. University of Western Ontario, Canada E-mail address: [email protected]
Glacier recession in the Canadian Rockies continues to reveal evidence of Holocene glacier advances prior to the Little Ice Age (LIA) maximum. Robson Glacier is unique in the Canadian Rockies with evidence of in-situ stumps overridden by three distinct glacier advances. Calendar (tree-ring dated) stumps and detrital wood with kill dates of between 1150 and 1350 A.D. represent the initial phase of the LIA at this site. Two buried forest sites were exposed close to the 1993-2000 position of the glacier snout yielding 14C-dated wood between 3300 and 3700 14C yr BP. Subsequently, wood from these two sites has been crossdated into a single chronology over 450 years. An in situ Pinus albicaulis snag ablated out of the glacier about 3km upglacier, near Extinguisher Tower at ca 2050m. Most recently wood was exposed in stream sections below a bedrock cliff, 150m below and half a km down ice of the Extinguisher site. This site contains a paleosol and logs >70cm diameter with >350 rings yielding a 14C date of 4780 +/-60 from the outermost rings. Eight of these trees crossdated to give a chronology of 560 years. The overlying till marks the earliest Neoglacial advance with in-situ material yet reported from the Rockies. The latter two events are older than Neoglacial events previously reported from sites in the Rockies at ca 2800-3000 yr BP (Peyto Advance) and 1500-1900 yr BP. THE USE OF LIPID BIOMARKERS FROM CAVE SEDIMENTS AS PALAEOENVIRONMENTAL INDICATORS IN SOUTH-EAST ASIA Natalie Ludgate. The Open University, United Kingdom E-mail address: [email protected]
294
Abstracts / Quaternary International 279-280 (2012) 233–345
Clastic cave sediments form in sheltered environments, collect material from airborne, water, and faunal sources, and are important to archaeology and palaeontology. Novel tools for palaeoenvironmental reconstruction in this context are therefore of interest to Quaternary research. This study forms the first comprehensive investigation of lipid biomarkers preserved in cave sediments. Lipid biomarkers are molecules such as plant waxes, which derive from living organisms, therefore forming a valuable tool for investigating changes in past ecosystems, independent of and complementary to existing techniques such as pollen analysis. Lipid biomarkers have been recovered from samples from two caves in Vietnam; Hang Boi, and Hang Trong. These sites which lie in the Ninh Bình province are both dominated by anthropogenic shell middens interspersed with sedimentation from windblown sands and bedrock breakdown. Hang Boi is an open cave situated at 78m a.s.l.; radiocarbon dates from charcoal from the section indicate the sediment ranges from 12,100cal. yrs. b.p. to 12,400cal. yrs. b.p. at the base, approximately 1 m depth. The second site, Hang Trong, is situated 142m a.s.l. and has two openings on opposite sides of a karst tower making it a good site to investigate airborne deposition. Radiocarbon dates from charcoal indicate the sub-surface sediment is recent and at approximately 1.5m from the surface, 18,500yrs. b.p. A wide range of compounds have been found, including those derived from plants, midden shells, and microbes. Stratigraphic sequences, covering 300 years from Hang Boi and 20,000 years from Hang Trong, demonstrate how the biomarkers change through time. Future work will focus on investigating the integrity of the proxy, especially post-depositional movement of organic molecules. To address this, compound-specific radiocarbon dating, will be used to investigate the ages of different biomarkers compared to the established chronology.
landscape records of deglaciated Pleistocene ice sheets, yet the origins of these enigmatic landforms and associated glacial geologic frameworks are not well understood. Analysis of geologic maps, subsurface framework, and surface morphology from North American glacial records show relations between forms and geology that (along with geophysics and continuity) constrain processes relevant to the subglacial origin of these features. For example, the morphologically concordant occurrence of bedrock-cored drumlins within drumlin fields provides evidence that subglacial erosional processes are necessary to their development. Aligned with similar orientations as bedrock-cored forms, drumlins and fluted forms with cores of unconsolidated sediment are a combination of erosional remnants of preexisting substrate (similar to bedrock cores) and later secondary accretionary mantle. Such a mantle is not essential to the drumlin form, but was accreted from debris-rich basal ice and/or advected subglacial sediment after the erosion of the swales that surround and created the core of the drumlins. In many areas, inter-drumlin networks of swales have a more deeply incised tunnel valley network superimposed upon them. Morphologic relations provide evidence that tunnel valley formation occurred during relatively late stages of glaciations and after drumlin formation. Drumlin form and dimensions generally do not vary in relation to proximity to tunnel valley margins, except for individual drumlins that adjoin and appear to be truncated at the margins of larger tunnel valleys. These relations indicate a transformation of erosional subglacial hydraulic conditions from a partially but not entirely distributed system (possibly linked cavity; but not sheetflow) to a more channelized regime of the tunnel valley network.
PHASES OF GLACIER RETREAT DETECTED IN ALPINE SPELEOTHEMS, UPPER GRINDELWALD GLACIER (SWITZERLAND)
EURO-MED 2K PAGES CONSORTIUM: REVIEW OF CURRENT KNOWLEDGE, AVAILABLE DATA COVERING THE PAST 2K IN THE EUROPEAN/MEDITERRANEAN AREA AND PLANS FOR MULTIPROXY INTEGRATION AND MODEL/DATA COMPARISON
Marc Luetscher. University of Innsbruck, Austria
Jürg Luterbacher. Univ. Giessen, Dept. für Geographie, Germany
E-mail address: [email protected]
E-mail address: [email protected]
Mountain valley glaciers and their sediments are prominent witnesses of climate change, responding sensitively to even small changes in meteorological parameters. Advances and retreats of the Upper and Lower Grindelwald Glaciers during the last w3 ka have been documented extensively (e.g. Holzhauser & Zumbühl, 1996; 1999). However, little is known about the early Holocene due to progressive erosion and mixing of palaeoenvironmental evidences. Here we explore a novel and continuous archive of glacier fluctuations in a cave system adjacent to the Upper Grindelwald Glacier. Four coeval stalagmites show consistent petrographic and stable isotopic changes between 9.2 and 2.0 ka which can be tied to abrupt modifications in the cave environment as a result of the closing and opening of multiple cave entrances by the waxing and waning of the nearby glacier. During periods of glacier advances, columnar calcite fabric is characterized by d18O values of about -8& indicative of speleothem growth under quasi-equilibrium conditions, i.e. only little affected by kinetic effects related to forced degassing or biogeochemical processes. In contrast, bacterially mediated calcite fabrics formed during periods of glacier minima are typical of precipitation within caves overlain by an alpine soil cover. This characteristic petrography is repeatedly observed before 5.8 ka pointing towards longer phases of glacier recession as compared to today where only scarce soil is present. Subsequent to 3.8 ka the tongue of the Upper Grindelwald Glacier was close to its Holocene maximum extent with retreat phases limited to some 20% of the total amplitude. The late 20th century was, however, characterized by massive down-wasting, reaching levels in 2010 similar or even lower than those attained during the early Holocene.
Focus 2 (Regional Climate Dynamics) of PAGES places a strong emphasis on regional studies that consider past climate dynamics on seasonal to millennial timescales and (sub) continental or ocean-basin spatial scales. The Europe/Mediterranean 2k (Euro-Med 2k) consortium reviews the current knowledge and the availability of documentary sources and high and low resolved terrestrial and marine archives covering the past two 2000 years from the European-Mediterranean area and discuss their interpretation and the prospects for their improved integration. A critical assessment of the proxies strengths and weaknesses and challenges and opportunities for climate reconstructions are presented. We also report on potential statistical methodologies that can integrate multiproxy data and that provide an estimate of the full covariance structure of the temperature and hydrologic reconstructions over the European-Mediterranean area for the past 2k, as well as diagnostic measures that indicate the utility of the different proxy time series for successful reconstruction. We will also provide preliminary analyses of new millennial long coupled climate model results and ways how to compare continental scale multiproxy climate reconstructions with coupled palaeo climate model output. The Euro-Med 2k consortium would also like to involve and integrate the wider community to share data and participate in the initiative, and the plans for the next couple of years of this group will be presented
GEOLOGIC AND GEOMORPHIC RELATIONS BETWEEN TUNNEL VALLEY NETWORKS AND DRUMLIN/FLUTE FIELDS: CONTRAINTS ON ASSOCIATED FORMATIVE SUBGLACIAL PROCESSES
Christopher Lüthgens. Freie Universität Berlin, Germany
Scott Lundstrom. U.S. Geological Survey, United States E-mail address: [email protected]
Tunnel valley networks and subglacial flow-field bedforms, including drumlin/flute fields, form common and overlapping elements within
A NEW DEGLACIATION CHRONOLOGY FOR NORTH-EASTERN GERMANY INFERRED FROM OSL DATING OF SANDUR SEDIMENTS AND A REINTERPRETATION OF SURFACE EXPOSURE AGES OF ERRATIC BOULDERS
E-mail address: [email protected]
During the last 130 years, the classification of the Weichselian Pleniglacial in north-eastern Germany has mainly been based on morphostratigraphical interpretations. In general, three main ice marginal positions are differentiated: The ice advance to the southernmost, relatively weakly developed ice marginal position of the Brandenburg phase has traditionally been ascribed to the LGM. The Frankfurt phase is usually interpreted as