Journal of Quaternary Science最新文献

Since the publication of Megafauna: Giant Beasts of Pleistocene South America by Fariña et al. in 2013, much has been published on this fascinating subject. Here, we sum up those contributions according to their aim: taxonomic, geographical and phylogenetic novelty, new approaches to the natural history of those species, and extinction and its aftermath. The traditional centres of interest since the 19th century, especially the Río de la Plata region, have now been complemented as a source of information by many other regions in South America, and the remains are now being studied by biogeochemistry and molecular biology, as well as with finite element analysis and constantly refined statistics. Finally, scholars and the public are becoming more interested in the demise of the megamammals as the starting point of the current process of biodiversity loss.

Myrmecophaga tridactyla Linnaeus, 1758 is the largest extant anteater, being distributed in most biomes from southern Central America and northern South America. Herein, we analyzed cranial and postcranial elements of three partial skeletons of M. tridactyla found submerged in Abismo Anhumas cave (Bonito, Mato Grosso do Sul, Brazil). The bones collected were the skull (LEG 2598), left humerus (LEG 2601), ungueal phalanx (LEG 2602), and lumbar vertebrae (LEG 2599; LEG 2600). Radiocarbon dating and isotope analyses indicate that these animals lived between 360 and 560 cal a BP in an arboreal to open savanna habitat associated with the Cerrado, a Seasonal Dry Forest. Radiocarbon-dated oxygen isotopes are possibly in agreement with dated oxygen isotopes found in stalagmites, suggesting a wet period between 442–364 cal a BP in the region. Finally, we created paleo-species distribution models, which allowed the generation of a consensus map showing a historically stable area between 21 and 6 ka for this species. Currently, more than 50% of this area has been destroyed by human activity.

Marine Isotope Stage (MIS) 5c, between ~106 000 and ~93 000 years ago, represents an important warm period in which the current anthropogenic warming can be contextualized. Although viewed as a pronounced interstadial, its climate expression is regionally disparate, with different regions on Earth showing evidence of either cooler or warmer conditions than modern-day. It is therefore important to expand temperature reconstructions to different regions on Earth to gain a better picture of climate dynamics during MIS 5c. In Alaska, there are no quantitative temperature reconstructions for MIS 5c, limiting our knowledge of temperature changes in this climatically sensitive high-latitude region. Here, we fill this gap by providing the first quantitative temperature estimates from MIS 5c in Alaska using hydrogen isotopes of fluid inclusions in precisely dated speleothems. We find that regional temperatures during MIS 5c were within error of the modern-day reference period (1929–1989 ce) temperatures, possibly representing the most recent time period that regional temperatures were as high as modern-day.

Grotta Polesini is one of the most famous paleontological and archaeological sites of central Italy, which testifies to its human occupation during the Lateglacial. The site comprises a cave system where systematic excavation campaigns have been carried out since the 1950s. In 1974, 656 mammal remains were collected but never studied. This fossil collection is here described for the first time through taxonomic and stable isotope analyses of the enamel of selected mammal teeth. The aim is to reconstruct the paleoenvironmental and climatic conditions of the site and to offer new information on terrestrial ecosystems during the Lateglacial in central Italy. The faunal assemblage studied herein, in addition to other species reported in previous works, suggests cold climate conditions. We also describe a right radius of an adult individual of Homo sapiens, increasing the human fossil record of the site. Carbon isotope data point to a scenario dominated by C3 plants in open and dry habitats, such as grasslands and steppes, in accordance with the pollen data from central Italy. The oxygen isotope data suggest the use of water resources with a local origin, i.e. local precipitation and surface waters with a provenance from the nearby Apennine chain. The ecology of the taxa influenced the oxygen isotope values, especially in the case of semi-obligate to non-obligate drinker species.

The concept of seasonal forests groups structural types of vegetation that are related to climatic seasonality in the tropics of South America. Consequently, this determines the physiognomy of the vegetation, from semi-deciduous to strongly deciduous. The strongest link between seasonally dry tropical forests (SDTFs) is their floristic composition, where Leguminosae and Anacardiaceae dominate the woody flora. The fossil records of the Neogene of northwestern Argentina reveal a list of species found in various locations and formations of the Miocene–Lower Pleistocene obtained from studies of pollen, woods (logs), cuticles, impressions of leaves and fruits. The analysis of sediments and woody structures from the Tapebicuá, Toropí/Yupoí and El Palmar Formations (Upper Pleistocene) of the Mesopotamia region allowed us to identify several pollen taxa and silicified wood fragments (mineralized). The woody and shrubby association whose current relatives characterize the SDTF is composed of the 16 fossil species described here belonging to seven families. In our samples, Anadenanthera colubrina and Myracrodruon balansae are the most significant members of the families Leguminosae and Anacardiaceae, which are dominant in the SDTF. The paleobotanical species described in this study confirm the extension of the SDTF to the province of Corrientes, coinciding with various climatic events (dry subtropical, semi-desert and warm-humid climate) that would have favored the development of these forests during the Pleistocene in this region. The absolute dates obtained for the Toropí/Yupoí and Tapebicuá Formations confirm their synchronicity and correlation to Marine Isotope Stage 5. The palynological analysis, the presence of Menendoxylon and the sedimentological data allow us to infer the existence of a seasonally dry humid paleoclimate in northeastern Argentina during the Late Pleistocene favorable to the development of the SDTF.

Hydroclimate variation and vegetation changes of the Nile River watershed area in northeast Africa since the Last Glacial Maximum (LGM) were reconstructed based on n-alkanes, their carbon isotope ratios (δ¹³C_n-alkanes), and their hydrogen isotope ratios (δ²H_n-alkanes) in sediments from ODP Site 967 in the Eastern Mediterranean Sea. The results were compared with the present vegetation cover in the watershed areas using ArcGIS. The average proportion of current grassland in the Equatorial Lake and Ethiopian Highland Plateaus watershed areas was 45.8 and 64.7%, respectively. δ²H_n-alkanes ranged from −199 to −127‰ and co-varied with insolation change response to orbital forcing. Depleted δ²H_n-alkanes were found from deglaciation to the middle Holocene, suggesting increased precipitation during the African Humid Period (AHP) from 15 to 5 ka caused by northward migration of the Intertropical Convergence Zone. However, lower precipitation was inferred by enriched δ²H_n-alkanes during the LGM and late Holocene. δ¹³C_n-alkanes at Site 967 did not show a trend in harmony with δ²H_n-alkanes and instead exhibited millennial-scale variations ranging from –25.9 to –33.2‰. These δ¹³C_n-alkanes values consistently indicated a C4 grass-dominated environment in the watershed areas of the River Nile since the LGM, persisting through the AHP and into the present. Reconstructions demonstrated orbital and abrupt forcing of hydroclimate variability while maintaining generally grass-dominated vegetation with weak precipitation feedback over the late Quaternary.