Journal of Quaternary Science最新文献

Southeastern China's coastal region is considered one of the key areas for studying prehistoric human–land relationships in the Western Pacific region. This region, which is rich in records of marine civilization, provides an ideal location for recording coastal environmental evolution. In this study, the chronological framework of three borehole cores recovered from Haitan Island, South China, near the Keqiutou group of sites, was established using both optically stimulated luminescence (OSL) and accelerator mass spectrometry radiocarbon (AMS ¹⁴C) dating techniques. Various analyses, including lithologic characteristics, chroma, clay–water electric conductivity (EC), grain size and elemental geochemistry, were conducted to elaborate the sedimentary sequence and its paleoenvironmental implications. The findings suggest that (i) since the late Quaternary, the Haitan Island sedimentary sequence can be divided into three deposition stages: Old Red Sand formed during Marine Isotope Stage 3 (MIS3), intermittent sedimentation during the Last Glacial Maximum and coastal aeolian deposition during the Holocene. Furthermore, the study reveals that terrestrial debris was significant as a material source for Haitan Island. (ii) Due to the absence of tectonic uplift, Haitan Island has no thick marine sedimentary record during the Holocene period of high sea level. The Luyangpu coastal sand sheet can be dated to 2.78 ka, which is consistent with previous reports giving dates of 2.4 ka. Prior to the formation of the sand sheet, the sedimentary environment in the area was characterized by lagoon or marsh facies. (iii) Paleoanthropological activities were influenced by sedimentary environmental evolution and geomorphic processes, among others. The Keqiutou Culture experienced high sea levels, which created an intertidal environment near the site and facilitated fishing. However, regression at 5.7 ka led to terrestrial environments, which prompted the inhabitants to migrate. Approximately 3 ka ago, sea levels rose again, coinciding with the initiation of rice cultivation. These factors may have influenced the transition from the Neolithic to Bronze Age culture. This study reconstructs evolution of the sedimentary sequence since the late Quaternary, enhancing our understanding of past human–terrestrial relationship in the region.

Organic matter is the material basis of shale gas. The Qaidam Basin is a key exploration and development area for shallow biogenic shale gas in China. In this study, we have focused on Quaternary Pleistocene shale in the Qaidam Basin, and the mechanism of organic matter enrichment was investigated in terms of water column stratification and paleoclimate. The results show that the K9–K7 section has greater biological productivity than the K5–K4 section. During the early–middle Pleistocene (K9–K7 deposition period), due to a warm and humid climate, the water column was strongly stratified and herbaceous plants developed, resulting in increased biological productivity. Stronger stratification also led to a reducing environment in the lower layer, which was conducive to the preservation of organic matter from the upper layer. During the late Pleistocene (K5–K4 deposition period), with a dry and hot climate, stratification became weaker and the vegetation evolved into woody plants, reducing biological productivity. Weaker stratification led to destruction of the reducing environment, which was not conducive to enrichment of the sedimentary organic matter. Moreover, the increased temperatures increased the activity of methanogenic bacteria, which consumed a lot of the organic matter.

The vertebrate assemblage recovered from the Toropí/Yupoí Formation (Late Pleistocene) in the Arroyo Toropí area, Bella Vista (Corrientes Province, Argentina), has been subjected to taphonomic evaluation. The fossil-bearing levels have been dated to ~53 ka (MIS 3) based on Optically Stimulated Luminescence dating. This assemblage primarily comprises mammal remains, with a notable prevalence of herbivorous megamammals. Also, reptiles and birds have been documented. Sedimentological analysis suggests that the skeletal remains were preserved within a floodplain environment influenced by the dynamics of the adjacent fluvial system, and taphonomic features observed in the assemblage support this interpretation. The assemblage resulted from the deposition of disarticulated mammal remains and local dispersion over a relatively short period. Rapid burial is evident, but several processes such as weathering and breakage have contributed to the observed patterns. The loss of several skeletal elements within the assemblage may be attributed to sporadic water flows occurring on the floodplain. During the post-burial stage, the specimens were affected by diagenetic processes, including filling, impregnation, deformation and breakage. In summary, the taphonomic evaluation of the Toropí/Yupoí Formation offers valuable comparison with other fossil fluvial assemblages. This research contributes to our understanding of the processes and environmental conditions that shaped this Late Pleistocene ecosystem.

The response of aquatic ecosystems in the Sierra Nevada (California, USA) to late Quaternary hydroclimate changes remains mostly unknown. Mono Lake, a large endorheic lake just east of the Sierra Nevada, contains an expanded archive of laminated sediments that can be used to examine the response of benthos to environmental changes. Fossil ostracodes from a radiocarbon-dated core were used to examine paleoecologic changes from ~16.6 to 4.3k cal a bp. Seven species were identified, with the co-occurrence of Limnocythere ceriotuberosa and Limnocythere staplini indicating a large SO₄²⁻-rich lake in the Pleistocene. The Younger Dryas was complex, with Fabaeformiscandona caudata reflecting a cold and deep lake ~13.0–12.2k cal a bp, followed by an interval of extensive littoral habitat from ~12.2–11.6k cal a bp. Ostracode diversity, valves g^–1 and the ratio of adult:juvenile valves declined after ~10.7k cal a bp due to regression, altered hydrochemistry and seasonal anoxia. Strong seasonality during the Early Holocene is suggested by the presence of reworked ostracodes and macrocharcoal, delivered to Mono Lake by erosion of ancient lake beds in the basin. A depauperate ostracode fauna in the Middle Holocene suggests a strong sensitivity to drought in this ecosystem, which has implications for biodiversity in the future.

While humic lakes are common in northern Europe, in central Europe they are rare and our understanding of their ontogeny is insufficient. Here, we present the reconstruction of the development of a humic lake in the Tatra Mountains (Slovakia) over the last 8000 years using chironomids along with diatoms, pollen and non-pollen palynomorphs. The compositional changes in aquatic proxies suggest three developmental stages. Since its formation the lake has been oligotrophic (phase 1), and its chemistry was controlled by subsurface waters rich in base cations buffering the effect of acid humic substances from forest and peat that were already present in the catchment. The beginning of the transition to phase 2 (~4400 cal a bp) is marked by simultaneous alterations in all proxies. Climate change combined with the local geochemistry was able to alter the limnological conditions supporting unique chironomid assemblages that have no analogues in recent Carpathian lakes. At ~3400 cal a bp the lake shifted to a phase when acidophilic/acidotolerant taxa indicate characteristic humic lake conditions (phase 3). Some chironomid taxa appearing ~2000 years ago for the first time indicate a dystrophic state in which the lake has remained until now. Human activities have been detected in the area since the Aeneolithic but had no direct influence on the lake.

Knowledge of bone pathologies in South American native ungulates is very scarce, which contrasts with other groups of megamammals such as xenarthrans and proboscideans. In this paper, based on morphological and histological analysis, we describe different bone pathologies in two specimens of Toxodon platensis Owen (Notoungulata), one of the most common taxa in the Late Pleistocene faunistic associations of northeastern Argentina. Subchondral erosions on the metacarpus and magnum, non-marginal syndesmophytes and enthesitis on the vertebral body, the neural column and the zygapophyseal joint of the lumbar vertebrae, as well as a particular periosteal reaction on the ribs, have been interpreted as manifestations of spondyloarthropathies in one of the analyzed individuals. In the same individual, a process of fusion and bone neoformation is observed in the caudal vertebrae, which seems to correspond both to the aforementioned spondyloarthropathy and to an infectious process. A lesion on the fourth metatarsus of a second individual with an evident cloaca is suggestive of osteomyelitis; this is the first report of this pathology in notoungulates. It seems possible that some of these pathologies may have been facilitated by factors such as body mass, mode of locomotion and/or environment. These findings provide insight into some aspects of the ecology of this particular group of extinct South American megamammals.

Dental calculus, or tartar, is a mineralized biofilm that develops on the teeth, and is often observed on the teeth of the South American proboscidean Notiomastodon platensis. This structure can provide details on paleoecological, paleoenvironmental and paleopathological aspects of a species. However, characterization of tartar in N. platensis is lacking. The aim of this study was to provide a macromorphological characterization of tartar on N. platensis molars, and evaluate its prevalence, distribution patterns and severity. A total of 117 molariforms from Brazilian Quaternary fossiliferous assemblages were analyzed. Thirty-five (29.9%) molars presented tartar. The majority displayed moderate severity. Calculus was present at least on one inteloph(id) of each molar, and prevailed on the posterior region. It predominated on lower and third molars. Adult individuals showed a predominance compared to juveniles. These patterns in N. platensis are probably due to the susceptible oral environment, molar morphology, mature age and tooth replacement. These results suggest that N. platensis and probably other proboscideans were relatively susceptible to tartar development.