Journal of Quaternary Science最新文献

Here we estimate the body mass of 10 iconic species of extinct xenarthrans (cingulates and sloths) from the Quaternary of Brazil using two sets of predictive equations based on postcranial variables. Our results revealed that one of these methods is more reliable in estimating the body mass of the evaluated taxa, even though both methods provide accurate results. The body mass estimates for cingulates indicate that they would have been heavier than previously proposed. Among extinct sloths, the results appear to be within the range of previous estimates. Compared to previously proposed body mass estimates for the same species, we suggest that the results presented in this study are more robust due to using predictive equations with high predictive power and developed using a broader phylogenetic dataset, including extant relatives.

Teeth and bone remains belonging to the juvenile Megalonychidae family were found in Engrunado cave (Nova Redenção, Bahia, Brazil). We propose an index between the mesiodistal/vestibulo-lingual measurements of caniniforms and molariforms (I_md/_vl) to differentiate isolated teeth of Ahytherium aureum and Australonyx aquae, and based on this index, we suggest that the fossil material belonged to A. aureum. The diaphysis of the right humerus of A. aureum presents biogenic marks assigned to the ichnospecies Nihilichnus nihilicus, suggesting dietary interactions and potential predation by a large felid. Radiocarbon dating and carbon and oxygen isotopic analyses suggest that this individual lived in the region between 36 181 and 41 094 Cal yr bp, feeding on C₃ plant resources (fruit and leaves) in a low-density forest. The revision of radiocarbon dating and carbon and oxygen isotopes for some species found in the Engrunado cave and in the nearby Marota cave enables a climate reconstruction and indicates the maintenance of a forested environment in the region between 15 and 40 kyr.

An integrated taphonomic analysis was applied to a tank deposit from the Zabelê Palaeontological Site (ZPS) in northeast Brazil. The unique sedimentological evidence documents the origin of the mammal assemblage via debris flow. Optically stimulated luminescence (OSL) dates put the ZPS in the later Marine Isotope Stage (MIS) 3, which was a time when it was colder and there were fewer trees. The study revealed that the Zabelê's periphery accumulation was the result of the short transport of specimens and their entrainment by debris flow. This hydraulic transport caused the preferential orientation of the bioclasts (north–southwest). Comparisons were made with other Pleistocene tank deposits, suggesting the occurrence of common megamammal taxa. Temporal mixing was evidenced by the long time interval recorded by OSL ages and the co-occurrence of distinct degrees of fragmentation, weathering, and fossil diagenesis. Permineralization and staining of Fe³⁺ and Mn colour patterns were identified as fossilization processes with preservation of the original bone hydroxyapatite without substitution. The comparison with other tank deposits revealed common signatures (disarticulated and fragmented with moderate abrasion) and signs of reworking. Finally, the savanna-adapted herbivore megamammals from ZPS, such as Eremotherium, Notiomastodon, Toxodon, and Glyptotherium, are congruent with the forest decline from MIS 3 to the Last Glacial Maximum.

The scarcity of high-resolution palaeoclimate records from the interior of West Asia has limited our understanding of the mechanisms of past climate change and their potential impacts on early human societies of the Eastern Fertile Crescent. Here, we present a multiproxy sedimentological, geochemical and palynological record from the Hashilan Wetland in the central Zagros Mountains, spanning the time interval from 22 to 2.2 kcal bp. Our results indicate a cold, dry climate for the last deglaciation (22 to 10 kcal bp) with amplified aridity during the Last Glacial Maximum, Heinrich Stadial 1, the Younger Dryas and the 8.2 and 3.2 ka events. The Early Holocene (11.6 to 7.8 kcal bp) is characterised by prolonged dry summers, frequent spring/summer dust storms and restricted oak woodlands that gradually expanded as summers shortened toward the second half of the Holocene (<6 kcal bp). We show an out-of-phase Holocene moisture variation between the interior of West Asia and the Indian Summer Monsoon domain and conclude that summer insolation-driven latitudinal shifts of the Hadley cell played a key role in seasonality changes in the interior of West Asia by modulating the strength and pathway of the subtropical high-pressure cells. Finally, we explore possible impacts of these changes on regional prehistoric human communities.

The Santa Elina rock shelter (Central Brazil) stands out with two human occupation layers with ground sloth fossil remains from the Late Pleistocene. Here, we explore the palaeontological aspect of this site. We update the taxonomic assignment of the ground sloth found in the shelter to Glossotherium phoenesis. Radiocarbon dating performed on bioapatite (¹⁴C_bioapatite) from two tooth specimens reveal the minimum ages of 14 944–15 239 cal a bp (unit II2) and 22 339–22 534 cal a bp (unit III4), which were converted to collagen using a novel approach and presented the calibrated ages of 17 450–17 906 cal a bp (¹⁴C_collagen = 14 547 ± 40) and 25 994–26 396 cal a bp (¹⁴C_collagen = 22 042 ± 40). We reinforce the chronology of the oldest unit of Santa Elina with material culture in association with megafauna bones to the Last Glacial Maximum. Carbon isotopic signatures suggest a mixed feeding diet for both specimens. The most recent ground sloth presents a higher isotopic value (δ¹³C = −1.8‰) and narrower niche breadth (B_A = 0.50) than the oldest one (δ¹³C = −3.3‰; B_A = 0.74). We conclude that G. phoenesis lived in an arboreal savanna habitat during the phases studied. Slightly different oxygen isotopic values (δ¹⁸O = 26.2‰ and 27.9‰) might suggest a decrease in humidity over time. Our results provide insights into the palaeoecology of the tropical Pleistocene G. phoenesis and the palaeoenvironmental setting of Santa Elina when occupied by early humans and megafauna during the Late Pleistocene.

Major shifts in hydroclimate have been documented during the last deglacial period and the Holocene in south-central Alaska. Rare freshwater calcium carbonate (marl) deposits in lakes on the Kenai Peninsula can be used to reconstruct past changes in hydroclimate, including the influence of groundwater inflow to lakes. Here, the postglacial sediment sequence from groundwater-fed Kelly Lake (60.514°N, 150.374°W) was analyzed for multiple proxies including isotopes of carbon and oxygen in marl calcite (δ¹³C_marl and δ¹⁸O_marl), and isotopes of carbon (ẟ¹³C_OM) and abundances of C and N in organic matter. Bulk sediment analyses include organic matter and calcium carbonate (CaCO₃) contents, visual stratigraphy and sediment flux. These analyses extend those of a previous paleoenvironmental reconstruction from Kelly Lake, which focused on sedimentary diatom oxygen isotopes and mass balance modeling over the past 10 000 years. Here, we show that Kelly Lake was deglaciated prior to 14.6 ka, and that by 14.0 ka marl dominated the sediments, with CaCO₃ precipitation probably driven by groundwater input and mediated by shallow-water charophytes. Marl accumulation decreased as organic and clastic inputs increased between ~12.2 and 11.5 ka. This shift, together with an increase in both δ¹³C_marl and δ¹⁸O_marl values and a decrease in CaCO₃ content, indicates an increase in the influence of meteoric water on the hydrologic budget under wet conditions, possibly driven by a strengthened Aleutian Low atmospheric pressure cell. A shift to lower δ¹³C_marl and δ¹⁸O_marl values at ~11.5 ka is interpreted as an increase in the proportion of groundwater relative to meteoric water in the lake. Beginning around 9 ka, the proportion of meteoric water input continued to increase, the surrounding coniferous forest was established, and by 8 ka, CaCO₃ accumulation ended. Our results elucidate the environmental conditions under which marl was deposited during the Lateglacial and early Holocene in this part of Alaska, and demonstrate how a variety of synoptic- and local-scale climatic variables can converge to influence sedimentation in a groundwater-fed lake.