A stratigraphic section made of Quaternary alluvial–lacustrine sediments belonging to the Baza Formation (South Spain) has been logged and studied for paleomagnetism, rock magnetic cyclostratigraphy, and electron spin resonance (ESR) quartz dating. Our results indicate that the section, which is found in the vicinity of a number of paleontological and archaeological localities, falls within the mid-Early Pleistocene (Calabrian), within the Matuyama Chron, and runs to the Jaramillo Subchron, encompassing the Cobb Mountain Subchron. The magnetostratigraphic results combined with rock magnetic cyclostratigraphy and ESR provide solid timelines, which allow gross accumulation rates to be estimated, and revealing an upsection decrease of sedimentation in accordance with the lithological and paleodepositional changes. Our study furnishes new chronologies to better understand the timing of the latest stages of endorheic sedimentation that precedes the capture of the Baza Basin by the Gualdalquivir River in the Middle Pleistocene.

Paleolake coring initiatives result in large datasets from various proxies taken at different resolutions, ranging from continuous scans to samples collected at coarser intervals. Higher-resolution data (e.g., core-scan X-ray fluorescence [XRF]) can detect short-duration changes in the paleolake and help identify unit boundaries with precision; however, interpreting the causes of such changes may require sampling and more intensive laboratory analysis like X-ray diffraction (XRD). This study applies a published wide and deep learning model, developed for the Olduvai Gorge Coring Project (OGCP) 2014 cores from the Pleistocene Olduvai basin, Tanzania, to reconstruct the mineral assemblages from saline-alkaline paleolake Olduvai using core-scan XRF data and core lithology. A classification model (predicting mineral presence or absence) and a regression model (predicting relative abundances of minerals) yielded predictions for two OGCP cores (2A and 3A), which were compared with published XRD mineral data and detailed core sedimentological descriptions. The models were excellent at identifying dolomite-rich layers, carbonate-rich intervals, intervals of sandstone within claystone, and altered tuffs within claystone and at predicting whether illitic or smectitic clays dominate. The models struggled with less-altered tuffs and with zeolites in non-tuff sediments, especially when XRD identified chabazite and erionite (rather than phillipsite) as the dominant, non-analcime zeolite.

Our analysis of 61 versions of the Great Basin (GB) Indigenous oral-history narrative, Theft of Pine Nuts, provides valuable new paleoecological insights into late Pleistocene (LP) and Holocene biogeography of pinyon pine (Pinus monophylla). Pinyon homelands indicated by Indigenous sources were located not only within the current pinyon distribution but also north of the known range, in northern California and Nevada, southern Oregon and Idaho, and western Wyoming. These extramarginal pinyon locations corroborate and expand a Western science hypothesis that proposed LP or Early Holocene refugial populations for pinyon in northern GB that subsequently became extirpated. The narratives also provide new evidence for pre-contact distributions of native mammals in the GB. From analysis of the “ice-barrier” accounts in the Indigenous narratives, we propose parts of this oral-history narrative may have been transmitted since LP times. Whereas most prior efforts have assessed Indigenous oral histories that describe catastrophic geologic events, we document that important ecological dynamics are also embedded in these stories. Our analysis joins other studies in recognizing that oral-history narratives can contain reliable eyewitness observations that are useful for reconstructing paleoenvironmental events and conditions.

An ∼0.2-km-long gravel spit (1398 m above sea level) at Sunstone Knoll in the Sevier basin, Utah, prograded into Lake Gunnison, a shallow lake in the Sevier basin that overflowed northward into the Great Salt Lake basin during the regressive phase of Lake Bonneville. Six radiocarbon dates for Anodonta shells and one optically stimulated luminescence age, which overlaps with the uncertainty range of the radiocarbon dates, yield an age for spit development and therefore, the initiation of Lake Gunnison overflow, at ∼15.5 cal ka. This age is older than the age of a larger spit 8 m lower in elevation that ended its progradation in Lake Gunnison about 12 cal ka. Strontium isotope ratios of the Anodonta shells from Sunstone Knoll (0.71049, 0.71059, 0.71064) are within the range of values for Lake Gunnison. The new date from Sunstone Knoll is consistent with cosmogenic dates from the Provo shoreline for the initiation of the regressive phase of Lake Bonneville (about 70 m higher than the spit). The major climatic shift, which caused the lake water budget and hydrology to change from overflowing while the Provo shoreline was forming to closed-basin conditions during the regressive phase, occurred by about 16.5 cal ka.

Mountain permafrost is a climatically sensitive but poorly constrained component of the terrestrial cryosphere. We use 108 U-Th dates from speleothems in two limestone caves in the Uinta Mountains of northern Utah, USA, to reconstruct a 600,000 year history of permafrost presence and absence in this alpine setting. Speleothem growth in both caves is confined almost entirely to discrete intervals that align with interglacial conditions of Marine Isotope Stages (MIS) 5e, 7e, 9e, 11c, and 13. In contrast, growth hiatuses correspond to glacial periods, when permafrost apparently inhibited infiltration of liquid water. Regional lapse rates indicate that cooling of ∼3°C to 5°C relative to present would be sufficient to generate permafrost above the caves. The persistence of age clustering across multiple speleothems in two independent cave systems suggests that mountain permafrost repeatedly formed and degraded in concert with orbitally paced climate cycles. Comparison with nearby paleoclimate records confirms that these changes reflect regional-scale climate forcing. Our results provide rare empirical evidence for the extent of alpine permafrost over Quaternary timescales. As mountain permafrost degrades under modern warming, such records are essential for refining climate models, assessing geomorphic and hydrologic risks, and placing recent changes within the context of natural variability.

Lake sediments record past hydrologic variability, but natural lakes are often sparse in semiarid and arid regions, making the calibration of paleohydrologic models a challenge. At Lake Elsinore, the largest of the few natural lakes in Southern California, we explore and develop a novel transfer function approach for reconstructing lake depth. Using 32 modern surface sediment samples spanning Lake Elsinore’s littoral to profundal zones, we establish a statistical relationship between lake depth and sediment elemental geochemistry composition analyzed via X-ray fluorescence (XRF). We develop lake depth transfer functions using weighted averaging-partial least squares (WA-PLS) and modern analog technique (MAT). Application of the WA-PLS C5 elemental geochemistry-based transfer function to Lake Elsinore sediment cores reveals a climatically sensitive and variable lake hydrology over the past 32,000 years. The reconstruction suggests a prolonged shallowing during an early Marine Isotope Stage 2 (MIS 2) mega-drought between 28,000 and 25,000 cal yr BP, a deep lake spanning the last glacial maximum, a wet–dry response to the Younger Dryas, and a highly dynamic MIS 1/Holocene lake. This single-lake elemental geochemistry technique may be useful in similar settings for reconstructing lake depth and inferring past hydrologic changes.

We examined trends in sediment deposition, organic carbon sourcing, and carbon and nitrogen isotopes in a transect of four lake sediment cores from eastern Glacier National Park (GNP), Montana, USA to understand how a connected chain of subalpine lakes downvalley from a retreating Grinnell Glacier have responded to environmental change over the last two centuries. Based on 210Pb ages, all three lakes showed a two- to five-fold increase in mass accumulation rate (MAR), with increased MAR beginning at most sites just prior to when GNP was established in 1910 CE, and again at the start of “The Great Acceleration.” Changes in MAR as a result of glacier retreat occurred at the most upvalley site, complicated by shifts in lake size and hydrology. A decrease in C:N ratios and slightly enriched δ13C values since ∼1850s CE reflect a shift toward decreasing terrestrial organic contributions and increased lake productivity. Concurrently, δ15N values were increasingly depleted across all sites over time. The most downvalley site captured spikes in MAR, C:N, and δ13C coincident with recorded flood events. This work demonstrates how organic geochemical and isotopic proxies together capture evolving connectivity between glaciers, catchments, lakes, and human activity under a warming climate.

The results of the taxonomic, taphonomic, and paleoecological analyses of Late Pleistocene micromammals from the Salto de Piedra paleontological locality are presented in this paper. Our results support the conclusion that the microfaunal remains were mainly accumulated by diurnal raptors in areas close to where the remains were deposited, as there is no evidence of transport. Taxonomically, the recovered micromammals include rodents currently inhabiting the Humid Pampa (Calomys cf. C. musculinus-laucha, Ctenomys sp., and Reithrodon auritus) and species that became extinct during the Late Pleistocene (Microcavia cf. M. robusta) and Holocene (Galea tixiensis). Additionally, remains of the Patagonian marsupial Lestodelphys halli and the amphibious sigmodontine Holochilus brasiliensis were identified. These analyses, along with the paleoecological and malacological studies at Salto de Piedra, confirm a trend toward increased humidity, consistent with the paleoenvironmental evidence documented for the region at the end of the Pleistocene. This study of the central Humid Pampa based on this small mammal record is of particular interest for interpreting the paleoenvironmental and paleoecological scenario, coinciding with the arrival of the first humans in the area and the extinction of the megafauna.

Bender’s Cave on the Edwards Plateau of Texas contains evidence of Late Pleistocene biodiversity that contrasts with the record from 17 regional sites dating to the last glacial interval, Marine Isotope Stage 2 (MIS 2). Bender’s Cave is a groundwater conduit system with an underground stream. Fossils occur in the cave primarily as an underwater lag assemblage and represent taxa that are typical of the Rancholabrean Land Mammal Age and common to central Texas (e.g., Bison, Mammuthus, Camelops). Megalonyx jeffersonii and Mammutidae also occur in Bender’s Cave but are rare elsewhere in the region. Other fossils provide the first regional records of Holmesina septentrionalis and a species of giant Hesperotestudo. The paleoecology of those novel taxa is inconsistent with regional paleoenvironmental proxies for MIS 2, which document a relatively open, dry grassland and cool climate. The novel composition of the assemblage may be the product of sample bias, and the fossils may be vastly time-averaged. However, the identified taxa frequently co-occur in other Texas sites interpreted as dating to interstadial/interglacial intervals of the late Pleistocene (i.e., MIS 3 or MIS 5), suggesting that fossils in Bender’s Cave may also date to one of those earlier warm periods.

We report a new relative sea level curve from Inglefield Land, northwest Greenland, to investigate the transition from maximum to minimum loading across Nares Strait. We sampled marine bivalves and terrestrial macrofossils for radiocarbon dating from raised marine terraces in Rensselaer Valley, Inglefield Land (78.58°N, 70.71°W) to constrain relative sea level through the Holocene. The oldest terrestrial macrofossil of 9010–8650 cal yr BP provides a minimum-limiting constraint for the deglaciation. Sea level fell rapidly from the marine limit at 85 ± 4 m to 37.5 ± 4 m above sea level (m asl) between 9010–8650 and 7970–7790 cal yr BP at a rate of 49 m/ka. The rate of sea -level fall decreased to 11 m/ka between 7970–7790 and 5320–5060 cal yr BP, when it fell from 37.5 ± 4 to 9 ± 4 m asl. After 5,320–5,060 cal yr BP, we estimate sea level fell at a lower rate of 2 m/ka to modern sea level. The period of fastest emergence in Inglefield Land is earlier in time than in Hall Land, reflecting earlier deglaciation, and is steeper than in Hall Land and Washington Land. This sea-level history captures the transition from the style of emergence from Pituffik to Hall Land.

The northeastern Arabian Peninsula has an extreme arid climate. To establish past variations in precipitation intensity during the late Quaternary, the oxygen isotope ratios (δ18O) of meteoric calcite cements of the late Quaternary aeolianites of the Ghayathi Formation in Abu Dhabi and Dubai have been analysed. The Ghayathi Formation is a carbonate-rich aeolianite, stabilised by calcite cement precipitated from rising groundwater during humid intervals. The calcite cements are well developed inside and outside a thin micrite rim of now hollow grains, formed by leaching of unstable carbonate grains. The δ18O values of cement analysed in thin sections by secondary ion mass spectrometry vary from −9.1‰ (VPDB) in coastal to +12.7‰ (VPDB) inland areas. This exceptionally wide range of the otherwise petrographically uniform aeolianite is due to the contrasts in humidity and evaporation rate between the coastal and inland areas. The δ18O values as low as −9.1‰ suggest intense precipitation in the late Quaternary, possibly due to the northward expansion of the intertropical convergence zone and intensified Indian summer monsoon. The exceptionally high values must be due to intense evaporation at low humidity in low-salinity, playa-type environments during intermittent arid intervals.