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Oxygen Isotope Stage (oxygen + isotope_stage)
Selected AbstractsStratigraphy and formation processes of the Upper Pleistocene deposit at Gruta da Oliveira, Almonda karstic system, Torres Novas, PortugalGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2009Diego E. Angelucci Gruta da Oliveira is a cave located in the Almonda karstic system in central Portugal. Its Upper Pleistocene fill is made up of gravitational sediments with varied biogenic and anthropogenic inputs. The archaeological sequence (35,70 ka) is fairly homogeneous, reflecting a predominantly moist climatic context modulated by millennial-scale variations. Human occupation was almost continuous throughout. In the richer archaeological layers (8,14), the anthropogenic components are in primary position, and post-depositional processes are restricted, although penecontemporaneous biological activity,such as hyena scavenging,overprinted the record. In layers 15,19, the excavated area corresponds to the footslope of a talus, where accumulation proceeded mainly through runoff and where the lithics and bones derive from occupations situated ca. 5m outward. The base of the deposit is >2m from the current base of the excavation, suggesting that Oxygen Isotope Stage (OIS)-4 and OIS-5 sediments underlay the deposit already exposed. This study confirms the archaeological integrity of the Mousterian assemblages found in the different layers, and, given the dates for layer 8, supports the hypothesis that Neanderthals survived in western Iberia until at least 35,000,38,000 calendar years ago. © 2009 Wiley Periodicals, Inc. [source] Late Mousterian subsistence and cave use in Dalmatia: the zooarchaeology of Mujina Pe,ina, CroatiaINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 2 2005P. Miracle Abstract The faunal assemblage from Mujina Pe,ina provides an initial glimpse of Late Middle Palaeolithic food procurement, management, and site use, in Dalmatia, Croatia. Radiometric dates place the entire sequence at about 42,kyr in the middle of OIS 3 (Oxygen Isotope Stage 3) (Rink et al., 2002). Mujina Pe,ina is located along a potential migration corridor for hominin populations moving into Europe from western Asia. The faunal composition shifts from a co-dominance of red deer and chamois,+,ibex in Layer D1,+,D2 that formed during relatively cold conditions to a clear dominance of wild caprids followed by large bovids and equids in Layer B,+,C that formed during relatively warm conditions. Although non-hominin carnivores played a significant role in the modification of the faunal assemblages throughout the stratigraphic sequence, the Late Mousterian faunal assemblage from Mujina Pe,ina shows the hominins to be competent hunters within a context of considerable competition from non-hominin carnivores. These ,mixed' hominin-carnivore signatures are pulled apart through a detailed taphonomic analysis of this well-excavated assemblage. The Mujina Pe,ina assemblage thus provides a significant point of reference for a broader-scale study of variability in Mousterian subsistence practices in their own right as well as within the context of the Initial Upper Palaeolithic in southeastern Europe. Copyright © 2005 John Wiley & Sons, Ltd. [source] DIGITAL CEMENTUM LUMINANCE ANALYSIS AND THE HAUA FTEAH HOMININS: HOW SEASONALITY AND SEASON OF USE CHANGED THROUGH TIME,ARCHAEOMETRY, Issue 4 2007C. M. WALL-SCHEFFLER The importance of environmental seasonality and the seasonal cycling of resources to human populations make studies of human responses to seasonality useful to test hypotheses about short- and long-term changes in human behaviour. This paper utilizes digital dental cementum luminance analysis in order to better understand patterns of the seasons of death of Ammotragus lervia at Haua Fteah, Cyrenaica, and to test whether long-term climatic changes can be detected in dental cement. The overall pattern of the season of death of A. lervia at Haua Fteah is that of year-round utilization, with a slight increase over time in A. lervia use during the growth period/summer time. The use of digital cementum luminance analysis (DCLA) to detect changes in the seasonal differences between temperatures indicates a trend for increased seasonality in temperature over the past 40 000 years at Haua Fteah. Furthermore, DCLA patterns in the more recent assemblages indicate a shift to a warmer climate from Marine Oxygen Isotope Stage (MIS) 3 to MIS 1. [source] Amino-acid geochronology and the British Pleistocene: secure stratigraphical framework or a case of circular reasoning?JOURNAL OF QUATERNARY SCIENCE, Issue 7 2002Danny McCarroll Abstract Aminostratigraphy is central to the recently revised correlation of Quaternary deposits in the British Isles, providing a link between terrestrial deposits and marine Oxygen Isotope Stages. The central tenet of British aminostratigraphy, however, that shells from the same interglacial yield very similar ratios, so that the characteristic ratios from different interglacials are distinct, remains uncertain. The data available suggest that amino-acid ratios from different interglacials do not fall into discrete groups, but overlap considerably. It is therefore not valid to assign individual shells to Oxygen Isotope Stages simply on the basis of their amino-acid ratios, which means that filtering data to remove high or low values, on the assumption that they represent reworked shells, is unacceptable. The range of ,characteristic ratios' assigned to British warm stages may have been underestimated and the degree of separation between them overestimated. Amino-acid ratios should be treated as sample data that are naturally variable. Copyright © 2002 John Wiley & Sons, Ltd. [source] A lock-in model for the complex Matuyama-Brunhes boundary record of the loess/palaeosol sequence at Lingtai (Central Chinese Loess Plateau)GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2003S. Spassov SUMMARY In most marine sedimentary records, the Matuyama-Brunhes boundary (MBB) has been found in interglacial oxygen isotope stage 19. In the magnetostratigraphic records of most Chinese loess/palaeosol profiles the MBB is located in loess layer L8, which was deposited during a glacial period. The MBB at Lingtai (central Chinese Loess Plateau) also occurs in L8 and is characterized by multiple polarity flips. The natural remanent magnetization is mainly carried by two coexisting components. The higher coercivity (harder) component dominates in loess layers and is thought to be of detrital origin. The lower coercivity (softer) component prevails in palaeosols and was most probably formed in situ by (bio-)chemical processes. A lock-in model for the Lingtai MBB record has been developed by extending the lithologically controlled PDRM model of Bleil & von Dobeneck (1999). It assumes two lock-in zones. The NRM of the magnetically harder component is physically locked by consolidation shortly after loess deposition, whereas the softer component is formed at greater depth by pedogenesis and acquires a chemical remanent magnetization of younger age. At polarity boundaries, grains carrying reversed and normal directions may therefore occur together within a single horizon. The model uses ARM coercivity spectra to estimate the relative contributions of the two components. It is able to explain the observed rapid multiple polarity flips and low magnetization intensities as well as the stratigraphic shift of the Lingtai MBB with respect to the marine records. [source] Late Weichselian glacial history and postglacial emergence of Phippsøya, Sjuøyane, northern Svalbard: a comparison of modelled and empirical estimates of a glacial-rebound hinge lineBOREAS, Issue 1 2000STEVEN L. FORMAN Field research on Phippsøya, the largest island in the Sjuøyane archipelago, defines the course and timing of postglacial emergence, documents past-glacier movements, and reinterprets deglacial sedimentary sequences. Previously described tills were not identified in sections exposed along the northeast shore of Phippsøya, but instead sublittoral sediments with rock-fall concentrations derived from the adjacent slope. A glacio-isostatically higher sea level >40 ka deposited sublittoral sediment and is possibly correlative to a deglacial event in oxygen isotope stage 4 or 5 identified at other sites on Svalbard. The postglacial marine limit is 22 ± 1 m aht and occurs as an escarpment or washing limit into a stony drift. This drift contains granite and quartzite erratics from Nordaustlandet that indicate coverage by a northward flowing ice sheet during the Late Weichselian. Datable material on the raised-beach sequence was rare and a 14C age of c. 9.2 ka on an articulated Balanus balanus from 10 m aht provides a minimum constraining age on the marine limit. A mild transgression occurred by 6.2 ka, with sea level falling close to present levels by c. 5.0 ka. The zone of zero emergence (hinge line) lies 10 to 20 km north of Sjuøyane and is approximately coincident with the last glacial maximum limit on the continental shelf. There is an approximately 75 to 100 km offset between observed and modelled zone of zero emergence, indicating a need to refine earth rheology-based ice-sheet models. [source] | |||||||||||||