Journal of Quaternary Science最新文献

Northern Australia experiences extreme seasonality via the Indo-Australian summer monsoon, with high inter-annual variability in hydroclimate. Understanding the influence of hydrological variability on the landscape through the period of human occupation provides important environmental context to support the interpretation of the rich archaeological and rock art records of the region. The development of terrestrial records of environmental change has remained challenging due to the limited traditional palaeoenvironmental archives in the region. This study reports on the potential of sediments from ecologically significant monsoon rainforest patches to further elucidate the palaeoenvironmental history of the Kimberley. An ~19 000-year record of monsoon rainforest variability is presented, inferred from pollen, charcoal and major element geochemical analysis. Monsoon rainforest-associated taxa vary in abundance through the deglacial and the Holocene, which is compared to broad-scale hydroclimate variability inferred from previous studies in the region. The persistence of arboreal, riparian and monsoon rainforest-associated taxa suggest a positive moisture balance at the site throughout the period archived. Fire activity inferred from micro- and macrocharcoal is greatest over the last ~6000 years, and broadly corresponds to periods when monsoon rainforest-associated taxa are less abundant. Challenges remain in using this type of site as an archive of environmental change, but they also present an opportunity to extend previous records both spatially and temporally with thousands of monsoon rainforest patches present across the Kimberley, and similar ecosystems found across northern Australia.

The North Sea Basin has been covered by ice sheets originating from both the British Isles and Scandinavia at multiple times during the Pleistocene. The Witch Ground Basin (WGB) in the central northern North Sea is a critical location in terms of interpreting Late Pleistocene glacial to glacimarine history of the North Sea since it was the location of the Witch Ground Ice Stream that was active on multiple occasions during the Mid to Late Pleistocene. We map five mega-scale glacial lineation flowsets corresponding to the changing ice flow direction of the Witch Ground Ice Stream and investigate the sedimentological fingerprint and corresponding subglacial depositional processes of this palaeo-ice stream. We show that sorted sand layers within a subglacial traction till represent periodic hydraulic jacking and ice–bed decoupling at the base of the Witch Ground Ice Stream. In contrast to previous studies that have described glacitectonites deposited below the most recent grounded ice in the WGB, we present analysis of sediment cores that recovered primarily massive diamictons without any obvious deformation structures. The most recent ice cover in the WGB (~18–16 ka) was thought to have been sourced from a localized ice cap over Orkney and Shetland. The presence of chalk clasts sourced from NW of the WGB described in this study from the stratigraphically youngest till confirms this interpretation. The transition from subglacial to glacimarine deposition, while acoustically well defined (from opaque to laminated acoustic units), appears surprisingly uniform in the recovered sediment cores, but can be differentiated based on a change in colour including mottling and banding, presence of whole intact shells, and the increased number of silt and sand lenses. ¹⁴C dating of glacimarine muds indicate high sedimentation rates of between 80 and 260 cm ka⁻¹. The transition from glacimarine to marine deposition is represented by a comparative decrease in sedimentation rate and deposition of Holocene age sandy mud. This study demonstrates a highly dynamic Witch Ground Ice Stream in the northern North Sea during the Late Pleistocene with evolving subglacial hydrology and depositional processes at the ice stream bed that left a distinct geomorphological and sedimentological fingerprint within the WGB.

Diatom analysis of sediments obtained from five cores drilled in Lake Mariout and the ‘Marea’/Philoxenite archeological site southwest of Alexandria, Egypt, allows us to reconstruct the lake's environmental history during the Hellenistic–early Islamic periods. The distribution pattern and the variation in relative abundance of recognized diatoms differentiated each core section into characteristic zones. These zones are interrupted by periods of poor preservation or non-diatom deposition that coincide with fluctuating lake phases of freshwater flooding of the Nile during humid warm episodes and arid phases associated with a reduction in the Nile's water influx that provides Lake Mariout with fresh water. A rising water level of Lake Mariout is estimated from the great abundance of riverine, planktonic Aulacoseira species. A lowering of water level was linked to a high abundance of brackish water taxa and/or periods of non-diatom deposition. Furthermore, the absence of diatoms at two intervals in Core 1 is associated with silty clay with an abundance of gypsum crystals which point to falling water lake levels with increasing temperature during dry periods. However, the intervals of poor preservation or no diatoms in other cores at ‘Marea’/Philoxenite are presumably related to the coarser nature of the sediment that indicate a major lake level lowstand, a high-energy depositional environment together with increased salinity and alkalinity. By comparing the diatom data in the examined cores, it is clear that the Aulacoseira granulata assemblage zone is characteristic of the Roman and Byzantine periods, which reflects relatively rising water levels due to Nile water inflow via the Canopic Nile branch and thus the connection between the canal and lake during this time. Furthermore, the predominance of Aulacoseira granulata with some pollution-tolerant taxa indicates extensive human occupation during the Roman–Byzantine periods, which is evidenced by increased nutrient concentration with higher input of humic substances due to human activities and their influence on the lake ecosystem.

A multiproxy study of a sediment sequence from a Québec peatbog characterises the rapid and significant environmental responses to changing climatic conditions from the deglaciation of the Laurentide Ice Sheet to the early Holocene period. Scotstown Bog (45°30'45.0“N, 71°11'42.0“W) is an ombrotrophic peatland on the edge of the Appalachian Uplands in southern Québec, Canada. We reconstructed its Late-glacial and early Holocene palaeoenvironments for 14 000–6 000 cal a bp using palaeobotanical (plant macrofossil, macrocharcoal, pollen analyses), faunal (chironomid analysis), sedimentological (grain-size analysis, sediment organic content), and geochemical (sedimentary n-alkanes and hydrogen isotope analyses) methods. We targeted our multiproxy reconstruction on the Late-glacial period, which provides an example of how biota can respond to profound changes in climatic and environmental conditions. A major transition occurred between 13 000 and 12 900 cal a bp, which is recorded in all palaeoecological proxies. Our reconstruction reveals two major environmental changes at this time. First, the Scotstown basin became isolated from a larger proglacial lake, as shown by sedimentological changes, sediment grain size and chironomid assemblage shift. Second, plant macrofossils and pollen influx show contemporaneous major shifts in the vegetation composition from tundra to tree-line to closed-canopy forested communities.

There is currently substantial debate over the use of prehension or hafting of tools by hominins. Many studies have been carried out to understand the prehension and hafting of hominin tools through experiments and through study of the anatomy and muscle system of both non-human primates and humans. This paper discusses the results of the analyses of macro-traces and micro-residues of prehension found on small flakes from the late Acheulean sites of Revadim (Israel), Jaljulia (Israel) and Fontana Ranuccio (Italy). Small flakes are ubiquitous in many Late Lower Palaeolithic sites where they were used for various activities, including butchering. Their reduced size leads us to consider how they were handled and if solutions including hafting techniques were adopted. In this paper, the experimental protocol adopted, and the results obtained from macro-traces and micro-residues allowed us to develop hypotheses regarding free-hand gripping of the small flakes by hominins at Revadim, Jaljulia and Fontana Ranuccio and the role that strength and pressure played in ensuring a good grip to enable the optimal use of these tools.