- Email: [email protected]
United States Quaternary coastal sequences and molluscan racemization geochronology – what have they meant for each other over the past 45 years?
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Abstracts / Quaternary International 279-280 (2012) 462–565
Sea. The third phase relates to Meltwater Pulse 1A; the fourth phase falls roughly into period of the Younger Dryas. We interpret all four phases as ice-sheet retreat. Also, Antarctica contributed a substantial amount of meltwater to the global sea-level rise at those times. Apparently, Weddell and Scotia Sea records, temperature rise over East Antarctica, global sea-level rise, and NH deglaciation are closely related, with possibly severe impacts on future climate and ice-sheet modeling studies. MAASVLAKTE 2 (PORT OF ROTTERDAM), A SHOWCASE INTERDISCIPLINARY RESEARCH OF DROWNED LANDSCAPES
OF
Henk J.T. Weerts. Cultural Heritage Agency, Netherlands E-mail address: [email protected]
The Port of Rotterdam (PoR) is presently expanding the Rotterdam harbour to the west into the North Sea. More than 200 million m3 sand is dredged from the North Sea floor several kilometres offshore to build the harbour. A new 20 m deep harbour canal will connect Maasvlakte 2, the new harbour, with the existing harbour. Weichselian and Early Holocene landscapes are being removed in the process of dredging and digging. From artefacts found earlier in the vicinity, it is known that Palaeolithic and Mesolithic hunter-gatherers were present in the area at stake. According to the Valetta convention, investigations had to be done to assess the possible loss of evidence of human activity in the affected areas. The offshore location of the drowned landscapes and the considerable water depth (20 to over 30 m), the conventional Dutch guidelines for (geo)archaeological research are not fully applicable. Hence, the Port of Rotterdam authorities and the Cultural Heritage Agency (CHA) signed an agreement for the investigations that are funded by the PoR and carried out by a consortium of research institutions, museums and universities under supervision of CHA and BOOR. For fossil remains, that are not under the Valetta jurisdiction, a separate agreement was signed between the PoR and the Rotterdam Museum of Natural History. The focus of the research programme is on palaeo-landscape reconstruction, palaeontology and archaeology. Methods used are (a.o.) vibracore drilling, seismic surveys, trawler fishing for large bones and artefacts, palaeo-ecology, absolute dating (OSL, 14C) and a combination of mechanised sieving and hand picking of small objects of the top of the outcropping part of the sand that was used to build Maasvlakte 2. This research programme serves as a test-case to develop new methods and techniques which can be applied in a more systematic way in offshore research in future. We present here the first results of the research programme that is now in full swing. CHANGES IN THE PHASE LAG OF DUST CONCENTRATION AND SIZE IN THE EPICA-DML ICE CORE DURING THE LAST TRANSITION Anna Wegner. Alfred Wegener Institute, Germany E-mail address: [email protected]
Mineral dust measured in ice core from Antarctica provides unique information about climate variability in the past. During cold stages the dust concentration in the atmosphere as reflected in the dust flux is about 2 orders of magnitude higher than during warm stages, which is explained by higher aridity and storminess. Within the EPICA project two deep ice cores were drilled in Antarctica, one of them in Dronning Maud Land (EDML). Here, we present a continuous record of dust concentration and size measured in the EDML ice core covering the time interval from the last glacial stage to the Holocene. We find synchronous phasing of dust concentration and size during cold stages and no clear phase relation during warm stages. Different explanations for these findings are discussed: One explanation for this is a different seasonality of active source areas and the intensity of the transport. Another explanation is the activation of additional sources during warm stages. UNITED STATES QUATERNARY COASTAL SEQUENCES AND MOLLUSCAN RACEMIZATION GEOCHRONOLOGY – WHAT HAVE THEY MEANT FOR EACH OTHER OVER THE PAST 45 YEARS?
Mollusks from United States coastal Quaternary deposits have been studied for the extent of amino acid racemization (AAR) for over 40 years, beginning with the pioneering work by Hare and Abelson in the mid-1960’s. These and later studies usually focus on the geochronological applications of AAR, either for relative or numerical dating, but implicit in many of these studies is the use of field-collected samples to understand more about the geochemistry of AAR. AAR data from superposed sequences (outcrop, core, or terrace flights) demonstrate that D/L values usually increase with increasing stratigraphic age, a basic criterion for the reliability of AAR as a dating tool. Factors affecting this trend include age mixing and poor shell preservation. Independent calibration for AAR numerical ages is provided by U-series coral dates for last interglacial (MIS5) deposits at several sites on both the US Pacific and Atlantic coasts. These calibrations also define trends of D/L values vs. latitude (isochrons) for samples of known equal age, another important test of the fundamentals of AAR. Additional calibration or testing of optional kinetic models is possible in selected situations using Sr-isotopes, paleomagnetics, or volcanic ash chronologies. Comparison of D/L values in Holocene and late Pleistocene (MIS 5) samples yield modeldependent estimates of full-glacial temperature reductions. Thick basin sequences in North Carolina and Southern California reveal numerous aminozones, often in direct superposition in single cores. Similarly, vertical terrace sequences at several California sites provide stratigraphic tests and insights into long term tectonic uplift rates. Broad latitude distribution of AAR results provides a framework for testing regional aminozone correlation. This approach identifies regions of rapid uplift in Southern California and major contrasts in the preservation of the Quaternary coastal record on the low uplift coastal plain of North Carolina. CALIBRATION OF AMINO ACID RACEMIZATION (AAR) KINETICS IN U. S. ATLANTIC COASTAL PLAIN QUATERNARY MOLLUSKS USING 87/86SR ANALYSES John Wehmiller. University of Delaware, United States E-mail address: [email protected]
Age estimates based on amino acid racemization (AAR) depend on factors such as genus, temperature history, and kinetic models. These variables can be minimized by analysis of a single taxon and by using samples from geographic regions with similar effective temperatures. Two racemization kinetic models, usually identified as “parabolic” and “non-linear” models, are tested for the amino acid leucine (frequently used in aminostratigraphic studies) by paired AAR and Sr 87/86 analysis of Mercenaria samples from early and middle Pleistocene strata from the North Carolina coastal plain. Stratigraphic control is provided by superposition, seismic stratigraphic correlation, biostratigraphy and paleoenvironmental analysis. Four distinct aminozones, identified as AZ3+, AZ3.5, AZ4, and AZ4+, are found in superposition in the older part of the section (Wehmiller et al., 2010). Mean Sr 87/ 86 age estimates (MacArthur et al., 2001) for shells from these four aminozones are 0.3, 0.6, 1.2, and 1.5 Ma, respectively. These four aminozones have non-linear model age estimates of 0.36, 0.65, 1.2 and 1.53 Ma, respectively. The parabolic model ages are much younger: 0.20, 0.29, 0.40, and 0.46 Ma, respectively. Although both AAR and Sr- age estimates have large uncertainties, the paired AAR-Sr 87/86 analyses of individual shells leads to the important conclusion that the parabolic model is not applicable to the interpretation of leucine D/L values in Quaternary Mercenaria specimens from the Coastal Plain. Parabolic kinetics closely approximate the racemization pathways for D/L valine and D-alloisoleucine/L-isoleucine values, but logarithmic equations yield even better correlation coefficients for these and the other amino acids alanine, aspartic acid, glutamic acid, and phenylalanine. The observed Sr-calibrated leucine racemization pathway, when compared with predicted non-linear model curves, indicates an integrated effective temperature for these samples of approximately 11o C. LANDSCAPE TRANSFORMATIONS OF EARLY RICE AGRICULTURE: METHODOLOGICAL DEVELOPMENTS AND NEW RESULTS IN THE ARCHAEOLOGICAL IDENTIFICATION OF ARABLE RICE SYSTEMS IN PREHISTORY
John Wehmiller. University of Delaware, United States
Alison Weisskopf. Institute of Archaeology, University College London, United Kingdom
E-mail address: [email protected]
E-mail address: [email protected]
Abstracts / Quaternary International 279-280 (2012) 462–565
Sea. The third phase relates to Meltwater Pulse 1A; the fourth phase falls roughly into period of the Younger Dryas. We interpret all four phases as ice-sheet retreat. Also, Antarctica contributed a substantial amount of meltwater to the global sea-level rise at those times. Apparently, Weddell and Scotia Sea records, temperature rise over East Antarctica, global sea-level rise, and NH deglaciation are closely related, with possibly severe impacts on future climate and ice-sheet modeling studies. MAASVLAKTE 2 (PORT OF ROTTERDAM), A SHOWCASE INTERDISCIPLINARY RESEARCH OF DROWNED LANDSCAPES
OF
Henk J.T. Weerts. Cultural Heritage Agency, Netherlands E-mail address: [email protected]
The Port of Rotterdam (PoR) is presently expanding the Rotterdam harbour to the west into the North Sea. More than 200 million m3 sand is dredged from the North Sea floor several kilometres offshore to build the harbour. A new 20 m deep harbour canal will connect Maasvlakte 2, the new harbour, with the existing harbour. Weichselian and Early Holocene landscapes are being removed in the process of dredging and digging. From artefacts found earlier in the vicinity, it is known that Palaeolithic and Mesolithic hunter-gatherers were present in the area at stake. According to the Valetta convention, investigations had to be done to assess the possible loss of evidence of human activity in the affected areas. The offshore location of the drowned landscapes and the considerable water depth (20 to over 30 m), the conventional Dutch guidelines for (geo)archaeological research are not fully applicable. Hence, the Port of Rotterdam authorities and the Cultural Heritage Agency (CHA) signed an agreement for the investigations that are funded by the PoR and carried out by a consortium of research institutions, museums and universities under supervision of CHA and BOOR. For fossil remains, that are not under the Valetta jurisdiction, a separate agreement was signed between the PoR and the Rotterdam Museum of Natural History. The focus of the research programme is on palaeo-landscape reconstruction, palaeontology and archaeology. Methods used are (a.o.) vibracore drilling, seismic surveys, trawler fishing for large bones and artefacts, palaeo-ecology, absolute dating (OSL, 14C) and a combination of mechanised sieving and hand picking of small objects of the top of the outcropping part of the sand that was used to build Maasvlakte 2. This research programme serves as a test-case to develop new methods and techniques which can be applied in a more systematic way in offshore research in future. We present here the first results of the research programme that is now in full swing. CHANGES IN THE PHASE LAG OF DUST CONCENTRATION AND SIZE IN THE EPICA-DML ICE CORE DURING THE LAST TRANSITION Anna Wegner. Alfred Wegener Institute, Germany E-mail address: [email protected]
Mineral dust measured in ice core from Antarctica provides unique information about climate variability in the past. During cold stages the dust concentration in the atmosphere as reflected in the dust flux is about 2 orders of magnitude higher than during warm stages, which is explained by higher aridity and storminess. Within the EPICA project two deep ice cores were drilled in Antarctica, one of them in Dronning Maud Land (EDML). Here, we present a continuous record of dust concentration and size measured in the EDML ice core covering the time interval from the last glacial stage to the Holocene. We find synchronous phasing of dust concentration and size during cold stages and no clear phase relation during warm stages. Different explanations for these findings are discussed: One explanation for this is a different seasonality of active source areas and the intensity of the transport. Another explanation is the activation of additional sources during warm stages. UNITED STATES QUATERNARY COASTAL SEQUENCES AND MOLLUSCAN RACEMIZATION GEOCHRONOLOGY – WHAT HAVE THEY MEANT FOR EACH OTHER OVER THE PAST 45 YEARS?
Mollusks from United States coastal Quaternary deposits have been studied for the extent of amino acid racemization (AAR) for over 40 years, beginning with the pioneering work by Hare and Abelson in the mid-1960’s. These and later studies usually focus on the geochronological applications of AAR, either for relative or numerical dating, but implicit in many of these studies is the use of field-collected samples to understand more about the geochemistry of AAR. AAR data from superposed sequences (outcrop, core, or terrace flights) demonstrate that D/L values usually increase with increasing stratigraphic age, a basic criterion for the reliability of AAR as a dating tool. Factors affecting this trend include age mixing and poor shell preservation. Independent calibration for AAR numerical ages is provided by U-series coral dates for last interglacial (MIS5) deposits at several sites on both the US Pacific and Atlantic coasts. These calibrations also define trends of D/L values vs. latitude (isochrons) for samples of known equal age, another important test of the fundamentals of AAR. Additional calibration or testing of optional kinetic models is possible in selected situations using Sr-isotopes, paleomagnetics, or volcanic ash chronologies. Comparison of D/L values in Holocene and late Pleistocene (MIS 5) samples yield modeldependent estimates of full-glacial temperature reductions. Thick basin sequences in North Carolina and Southern California reveal numerous aminozones, often in direct superposition in single cores. Similarly, vertical terrace sequences at several California sites provide stratigraphic tests and insights into long term tectonic uplift rates. Broad latitude distribution of AAR results provides a framework for testing regional aminozone correlation. This approach identifies regions of rapid uplift in Southern California and major contrasts in the preservation of the Quaternary coastal record on the low uplift coastal plain of North Carolina. CALIBRATION OF AMINO ACID RACEMIZATION (AAR) KINETICS IN U. S. ATLANTIC COASTAL PLAIN QUATERNARY MOLLUSKS USING 87/86SR ANALYSES John Wehmiller. University of Delaware, United States E-mail address: [email protected]
Age estimates based on amino acid racemization (AAR) depend on factors such as genus, temperature history, and kinetic models. These variables can be minimized by analysis of a single taxon and by using samples from geographic regions with similar effective temperatures. Two racemization kinetic models, usually identified as “parabolic” and “non-linear” models, are tested for the amino acid leucine (frequently used in aminostratigraphic studies) by paired AAR and Sr 87/86 analysis of Mercenaria samples from early and middle Pleistocene strata from the North Carolina coastal plain. Stratigraphic control is provided by superposition, seismic stratigraphic correlation, biostratigraphy and paleoenvironmental analysis. Four distinct aminozones, identified as AZ3+, AZ3.5, AZ4, and AZ4+, are found in superposition in the older part of the section (Wehmiller et al., 2010). Mean Sr 87/ 86 age estimates (MacArthur et al., 2001) for shells from these four aminozones are 0.3, 0.6, 1.2, and 1.5 Ma, respectively. These four aminozones have non-linear model age estimates of 0.36, 0.65, 1.2 and 1.53 Ma, respectively. The parabolic model ages are much younger: 0.20, 0.29, 0.40, and 0.46 Ma, respectively. Although both AAR and Sr- age estimates have large uncertainties, the paired AAR-Sr 87/86 analyses of individual shells leads to the important conclusion that the parabolic model is not applicable to the interpretation of leucine D/L values in Quaternary Mercenaria specimens from the Coastal Plain. Parabolic kinetics closely approximate the racemization pathways for D/L valine and D-alloisoleucine/L-isoleucine values, but logarithmic equations yield even better correlation coefficients for these and the other amino acids alanine, aspartic acid, glutamic acid, and phenylalanine. The observed Sr-calibrated leucine racemization pathway, when compared with predicted non-linear model curves, indicates an integrated effective temperature for these samples of approximately 11o C. LANDSCAPE TRANSFORMATIONS OF EARLY RICE AGRICULTURE: METHODOLOGICAL DEVELOPMENTS AND NEW RESULTS IN THE ARCHAEOLOGICAL IDENTIFICATION OF ARABLE RICE SYSTEMS IN PREHISTORY
John Wehmiller. University of Delaware, United States
Alison Weisskopf. Institute of Archaeology, University College London, United Kingdom
E-mail address: [email protected]
E-mail address: [email protected]