Quaternary Research最新文献

The fluvial capture of endorheic basins represents a milestone in basin chronology, implying a profound disequilibrium that triggers critical geomorphological, sedimentological, paleogeographic, and even paleoecological transformations. The primary goal of many geomorphological studies is to determine the timing of endorheic-to-exorheic transitions with the objective of unveiling the dynamics that follow the capture event. The age of the Guadix-Baza Basin capture in the Central Betic Cordillera (S Spain) remains a subject of controversy, with proposed estimates ranging from 17 to 600 ka. In this study, we present new 234U/230Th and optically stimulated luminescence ages from exorheic deposits exposed within the basin's main fluvial valley, the Guadiana Menor River. We acquired the oldest numerical age recorded to date for a postcapture deposit within the basin. This age corresponds to a travertine platform formed 240.8 ± 25 ka on a surface level that was already incised into the glacis surface at approximately 250 m. Using these data, we estimate that basin capture took place earlier than ca. 240 ka, plus the time required for the river to incise 250 m to the position of the travertine. Furthermore, the proximity of the Matuyama-Brunhes reversal (781 ka) to the top of the endorheic succession and the ages of the paleontological sites (> ca. 750 ka) throughout the basin suggest that the capture could have occurred earlier than the oldest previously proposed age of 600 ka.

This study explores patterning in δ18O values of tooth enamel in contemporary African herbivores from mainly C3-dominated ecosystems. Evapotranspiration causes plants to lose H216O to a greater extent than H218O, leaving leaves enriched in 18O. In eastern Africa, ES species (evaporation-sensitive species: those obtaining water from food) tend to have more positive δ18Oenamel values than EI species (evaporation-insensitive species: those heavily dependent on drinking water); the magnitude of the difference increases with increasing aridity. We find the same pattern applies in the winter and year-round rainfall region of southern Africa, allowing us to use δ18Oenamel in fossil animals to examine paleo-aridity. We apply this approach to infer aridity at Quaternary fossil assemblages from present-day winter and year-round rainfall zones, including Elandsfontein (ca. 1–0.6 Ma), Hoedjiespunt (ca. 300–130 ka), and Nelson Bay Cave (23.5–3 ka). This analysis suggests that (1) at various times during the Pleistocene, Elandsfontein and Hoedjiespunt environments were wetter than last glacial maximum (LGM) to Holocene environments at Nelson Bay Cave (year-round rainfall zone); and (2) considered alongside other evidence from the year-round rainfall zone, wetter conditions across the Pleistocene–Holocene transition at Nelson Bay Cave suggests that climate changes at near-coastal sites may be out of phase with the adjacent interior.

Late Pleistocene deposits in the southern Kola Peninsula, adjacent to the White Sea, evidence the complex alternation between marine transgressions and glacial expansions in northern Europe during successive late Pleistocene warm and cold stages. According to lithostratigraphic and chronological data from key sections, southern Kola Peninsula underwent two phases of the Boreal marine transgression during Marine Isotope Stage (MIS) 5; marine environments, encompassing the very end of MIS 4 and almost the entirety of MIS 3, were also recognized. Age determinations using electron spin resonance (ESR) and infrared optically stimulated luminescence (IR-OSL) techniques reveal marine sediments with ages ranging from 138–128 ka to 72.4 ± 5.6 ka in the Varzuga, Chavanga, Chapoma 1 and 2, and Bolshaya Kumzhevaya sections, indicating initial and second phases of the Boreal transgression. The presence of marine deposits with ages ranging from ca. 59 ka to 37 ka in the Chavanga, Kamenka, Chapoma 2, and Bolshaya Kumzhevaya sections also suggests an accumulation stage in the marine environment. The research material from the studied sections provides evidence of a short glacier expansion into coastal areas of the White Sea during early MIS 4 and a continuous glaciation from the late MIS 3 and throughout MIS 2.