In this study we describe the dentition of cave hyena Crocuta spelaea (Goldfuss, 1823) from Tip-Tugai cave (Southern Urals, Late Pleistocene) using morphometric and morphological analysis and investigate its dietary preferences using analysis of dental microwear and taphonomy of the locality. Crocuta spelaea from Tip-Tugai cave are generally similar to other C. spelaea in tooth morphology and size, but one p4 specimen of the Tip-Tugai hyena is larger than any other cave hyena p4 specimen used for comparison. The combined sample of Ural C. spelaea differs from some of the European C. spelaea in having longer p2, p3, and P3, suggesting a higher degree of bone-cracking adaptation. Microwear analysis of C. spelaea carnassials from Tip-Tugai cave showed that both adult and juvenile individuals had a significant amount of bone in their diet. Most large herbivore bones from Tip-Tugai have hyena teeth marks, also from both adult and juvenile individuals. Microwear analysis additionally revealed a possible link between hierarchical position of C. spelaea and microwear parameters.
The Mammoth Site (MS) at Hot Springs, South Dakota, provides a unique opportunity to reconstruct paleoenvironmental conditions on the Northern Great Plains of the United States. Previous radiocarbon analyses of mammoth bone apatite suggested the MS sinkhole was deposited similar to 42-23 cal ka BP. However, two U-series ages and one thermoluminescence (TL) age ranged between 150 and 101 ka, suggesting the bones were considerably older. We analyzed six samples from the bone bed using infrared-stimulated luminescence (IRSL) on feldspars, because the quartz luminescence was saturated; the ages ranged from approximately 232 to 160 ka, showing better agreement with previous U-series and TL analyses. In addition, we dated three samples on two terraces that are at lower elevation than the MS. Our new IRSL ages show that the sediments of the MS were likely well bleached, derived from pond margin runoff events, and deposited as sandy-silt laminae couplets. Our chronology indicates that the 6-m-thick bone-bearing sediments accumulated at a rate of approximately 12 mm/yr and that deposition occurred during Marine Isotope Stage (MIS) 6 and MIS 7, not MIS 2 and MIS 3 as previously published.
The sandy Barrier III of the southern Brazilian coast was formed by sea-level high stands correlated to Marine Isotope Stage (MIS) 5, but little is still known about its behavior and evolution between the last glacial period (MIS 4-2, 71-11.7 ka) and the Holocene (MIS 1). A study on luminescence-dated continental sedimentary successions directly overlying MIS 5c (105.9-92.8 ka) marine deposits shows a wet, partially vegetated aeolian system developed between <104 and >82 ka, succeeded by a dry aeolian system accumulated mainly as transgressive sand sheets (TSSs) on interdune flats between similar to 82 and 10.5 ka. Protosols interbedded with TSSs indicate episodic vegetation expansion between similar to 71 and 46 ka. Sediment accumulation was apparently controlled by autogenic (cannibalization, migration of bedforms) and allogenic (sea-level oscillations, climate) processes. Weathering and pedogenesis promoted changes in color and magnetic susceptibility (MS), and the development of redoximorphic features involving Fe and Mn released from weathered minerals. Strong pedogenesis after similar to 10.5 ka, probably related to the Holocene climatic optimum (HCO) and orbitally driven increased seasonality and dryness, produced rubification similar to red beds on the barrier top. This study contributes to the understanding of long-term evolution and sedimentary dynamics of coastal barriers and aeolian systems on glacial-interglacial timescales.
Understanding past relative sea level (RSL) is important for constraining the timing and magnitude of changes in the cryosphere, providing critical benchmarks for models used to project future sea-level change, and supplying a datum for constraining past vertical motion. Past sea-level records from Antarctica can help determine the extent to which small or large changes in ice cover induce a response of the solid Earth in tectonically active settings. Here, we examine raised beaches located at Duthoit Point, Nelson Island, Antarctica. We combine geomorphic mapping and high-resolution topographic surveys to reconstruct RSL change and glacial fluctuations during the Holocene. Our study is the first record from Duthoit Point and identifies sea-level changes associated with up to four Holocene ice advances, likely occurring between similar to 7000 and similar to 4800 cal yr BP, at similar to 2000 cal yr BP, at similar to 500 cal yr BP, and during a more recent advance younger than similar to 500 cal yr BP. Our findings support assertions that uplift rates are primarily driven by glacial isostatic adjustment and changes in ice extent modulate isostatic responses at centennial to millennial timescales. Improved constraints on Holocene uplift histories provide important benchmarks for evaluating isostatic adjustment models used to reconstruct past ice-sheet change and project future sea-level change.
Continuous, high-resolution sedimentary records from the Great Basin are rare. By combining physical sedimentology with charcoal analysis to document changes in lake level and biomass burning, we explore the coevolution of climate and fire ecology over the past 7000 years. Elemental data from scanning X-ray fluorescence (XRF) measurements suggest persistently low lake levels during the Middle Holocene (7000-4000 cal yr BP). Two prolonged low lake stands between 4200-3800 cal yr BP and 2600-2400 cal yr BP occurred during widely documented periods of abrupt environmental change throughout the Great Basin. Significant correlations between the first principal component of the XRF record (which explains >75% of the variance) and a bristlecone pine-derived temperature reconstruction suggest warmer temperatures were a major driver of reduced precipitation-evaporation balance. Spectral analysis shows interannual and multidecadal periodicities typical of Pacific Ocean-atmosphere systems have been influential across the region after 4000 cal yr BP. Severe fire events became more commonplace as precipitation increased, highlighting the role of fuel availability on biomass burning in this semiarid region. These results suggest that while near-term warming will likely lead to increased biomass burning, prolonged periods of warmth and aridity will catalyze returns to the fire regimes of the Middle Holocene.
