The Mission Creek fault strand (MCF) of the San Andreas Fault is proposed to be the primary strand accommodating slip between the Pacific and North American plates in Southern California, but its Holocene activity northwest of Indio is debated. This study presents new depositional ages for alluvial deposits near the mouth of the Mission Creek drainage to investigate potential Holocene activity of the MCF. We estimate a mean depositional age of 0.7 ± 0.2 ka for the alluvium deposited in the drainage valley, contradicting previously inferred ages of >3–18 ka. The young ages for alluvium, often indistinguishable from the age of modern alluvium, suggest that grains are transported during high-energy flash flood–like events. A comparison of luminescence and cosmogenic 10Be ages from alluvial surfaces adjacent to the Mission Creek suggests a possible reworking event at ∼30 ka. Young alluvium ages, together with evidence for frequent flash floods, suggest that this site is rapidly resurfacing and therefore unlikely to preserve surficial rupture signatures older than a few hundred years. Therefore, the lack of observable offsets in deposits overlying the MCF does not imply Holocene inactivity.

Climate oscillations may strongly modify continental precipitation and temperature patterns, therefore understanding their history is relevant for comprehending effects of past and ongoing climate changes. For this purpose, temperature and precipitation reconstructions beyond the instrumental record are extremely useful. As widespread terrestrial archives, loess–paleosol sequences are viable targets for such analyses. Consequently, cost-efficient geophysical proxies have gained increasing attention, but little is known about their capability to reflect even narrow climatic differences. Here we assess the sensitivity of rock-magnetic and photo-spectrometric properties of topsoil samples (n = 50) along uncorrelated, mean annual precipitation (MAP: 525±1 mm/yr to 584±1 mm/yr) and mean annual temperature (MAT: 10.8±0.1 °C to 11.2±0.1 °C) gradients across the Bačka Loess Plateau (Serbia) and test a multivariate approach. Most proxies are sensitive to MAP <565±1 mm/yr, especially anhysteretic remanent magnetization (r2 = 0.81). Applying a multivariate approach to hysteresis data reveals a robust relationship between precipitation (r2 = 0.63), aridity (r2 = 0.67) and physical properties over the entire MAP range. Although the approach needs to be further tested considering different climates, regression analyses, and timescales, our study indicates that multi-proxy approaches may increase the robustness with respect to single-proxy measurements for MAP and aridity reconstructions.

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.

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.

The prehistoric cultural material at the Lodoso Site, a Middle Archaic to Late Prehistoric campsite near Driscoll, Texas, is dominated by irregularly shaped heat-hardened fragments of earth called burned clay objects (BCOs). These artifacts are a common component of coastal plain archaeology in Texas and elsewhere in the state. Many such sites, especially those situated in sandy soils, do not preserve charcoal well, which renders dating the occupations challenging. The clayey matrix of the Lodoso Site does preserve charcoal, which presents an opportunity to assess the suitability of luminescence dating of burned clay objects by thermoluminescence (TL) and optically stimulated luminescence (OSL), and directly compare those results with charcoal collected from the same excavation provenience, as well as OSL dating of the sedimentary matrix. The TL and OSL results generally track together well but are consistently slightly older than charcoal collected from the same level. The charcoal dates suggest the midden formed between approximately 1500 and 2300 years ago, whereas the luminescence ages suggest formation occurred between 2000 and 3000 years ago. Where the luminescence ages occur out of stratigraphic order, so do the paired charcoal samples, indicating that this is a result of pedoturbation. The results of both radiocarbon and luminescence dating indicate that the midden is a diachronic feature resulting from use over a prolonged period rather than the product of a single burning event.

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.

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.

Luminescence dating has developed over the last ∼60 years as a powerful technique for placing environmental and anthropogenic change into a secure temporal framework. However, over time, many have forgotten, or were never introduced to, the history of how of the method developed, particularly the role of unique instruments built in-house that enabled key methodological advances. In this paper we provide a concise history of the technique’s evolution, drawing on our own experiences.

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.

The East Asian monsoon is a key component of the global climate system; our understanding of its long-term variability and seasonal dynamics remains incomplete. Here we evaluate calcified root cells (CRCs) as a novel paleoenvironmental proxy. We apply this approach to the Fanshan loess–paleosol sequence, northeast China, on the northern margins of East Asian monsoon influence. We present the first continuous down-profile record of CRC concentrations together with carbonates, stable isotopes (δ1⁸Ocarb, δ13Ccarb), and organic matter (δ13Corg) and compare these with grain-size and stratigraphic indicators. CRC concentrations correlate with glacial–interglacial variability: high concentrations within paleosol reflect enhanced vegetation and moisture availability, and low values within primary loess units reflect colder, drier conditions. The estimations of δ1⁸O values of precipitation during the Marine Isotope Stage 5 (MIS 5) indicate an intensification of the monsoon rainfall as compared with present-day scenarios. The δ13Ccarb values are unusually low, which is attributed to kinetic isotope effects, thereby suggesting that CRC formation occurs under quasi-closed conditions dominated by soil organic matter respiration. Internal isotopic variability and CRC concentrations within the MIS 5 paleosol point to multiple episodes of pedogenesis. Our results demonstrate the potential of CRCs to record both long-term monsoon variability and short-term hydroclimatic seasonality, informing past East Asian monsoon dynamics.

Understanding the local to regional history of extreme events such as debris flows and floods provides context to plan for and mitigate these hazards to life, property, and infrastructure. The Klamath Mountains of northwestern California have experienced both debris flows and devastating wildfires. Whiskeytown National Recreation Area (WHIS) is at the heart of this range and has a wealth of debris flow–related landforms. Gaining an understanding of prehistoric flows and their relationship with fire or other potential triggers can help mitigate future problems. Optically stimulated luminescence and radiocarbon analyses from sediment and entrained organics in undisturbed facies, including beneath partially buried boulders, establishes a chronology of paleo-events in WHIS. The levee deposits indicate a repetition of debris flows during the latest Holocene, every 125–150 years, since 850 yr. Larger flows occurred, with a record elucidated from debris-flow deposits along Clear Creek, with Middle Holocene ages, ca. 2600 to 5500 yr, most of which have sufficient concentrations of charcoal to indicate origins as postfire debris flows. Deposits at higher elevations show events from the latest Pleistocene ca. 13,000 yr. This geochronology indicates that these are not singular events but are relatively common and inherent to the geomorphic processes shaping this landscape.

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.

The chronology of Late Pleistocene and Holocene aeolian sand activity in midcontinent North America provides important insight into paleoenvironmental change and associated surface processes. Near the limit of Marine Isotope Stage 2 glaciation of the Huron-Erie Lobe (Laurentide Ice Sheet) in south-central Indiana, aeolian sand deposits found along the eastern margin of outwash plains in the East Fork and West Fork White River valleys provide an opportunity to test the causal mechanisms for aeolian sand activity. Twenty-five optically stimulated luminescence ages on aeolian sand and four radiocarbon ages on gastropod shells document two phases of aeolian sand activity. The first phase, between 26 and 19 ka, records deflation from active outwash plains in the East Fork and West Fork White River valleys during and after the local glacial maximum. These ages overlap with the chronology of Huron-Erie Lobe advance into and out of the White River drainage basin based on a radiocarbon-dated slackwater succession. The second phase, between 16 and 12 ka, records reworking of older aeolian sand and outwash during a period of no-analog vegetation during the Bølling-Allerød/Younger Dryas and is in general agreement with the timing of dune activity from previous studies in the Great Lakes region.

Loess–paleosol sequences (LPSs) provide valuable archives of Quaternary paleoenvironments. Here we present new data from the Baix LPS, comprising the entire Late Pleistocene. The Baix LPS is located at the western edge of the Rhône Rift Valley, France, in the transition zone from the presently temperate to the Mediterranean region of Europe. This LPS provides a missing link between the analyzed LPSs in the presently temperate regions farther north and those in the Mediterranean region. Reddish Btg horizons of a Stagnic Luvisol at the base of the Baix LPS represent the remains of an MIS 5 pedocomplex formed under warm and, at least temporarily, relatively moist conditions. Two brown Bw horizons of truncated Cambisols have been preserved in the overlying MIS 5a/4 to MIS 3 deposits. The upper Bw horizon is associated with large carbonate nodules, indicating that considerable amounts of calcium carbonate were leached from a former MIS 3 Cambisol and accumulated in the underlying loess unit. This truncated MIS 3 Cambisol is very similar to the MIS 3 paleosol remains in the LPS Collias that we investigated 87 km farther south in the present Mediterranean climate. No paleosols were observed in the late MIS 2 deposits.

The optically stimulated luminescence (OSL) sensitivity of quartz ranges across five orders of magnitude. Previous studies suggested that quartz OSL sensitivity is enhanced by solar exposure–burial irradiation cycles. Spatially resolved luminescence measurements and laboratory illumination–irradiation experiments were used to investigate the OSL sensitivity of quartz crystals from a granodiorite cobble and quartz grains from a fluvial sand. Quartz from the granodiorite cobble has low OSL sensitivity, showing an approximately linear sensitization path that resulted from laboratory illumination–irradiation cycles. The mean OSL sensitivity of quartz sand grains (100 grains) increased from ∼40 to 80 counts after 1260 illumination–irradiation cycles. Each grain has a specific sensitization trajectory due to illumination–irradiation cycles, suggesting that quartz crystal composition heterogeneities drive the OSL sensitization of their daughter sediment grains. Maximum OSL sensitivity of quartz sand grains is reached after illumination–irradiation cycles representing an accumulated dose of around 4000 Gy. This dose corresponds to sediment burial time of 2–4 Ma, which is unlikely to occur during a single sediment transport route. This study suggests that illumination–irradiation cycles are unable to produce quartz sand grains with OSL sensitivity up to five orders of magnitude higher than the sensitivity of parent crystals in igneous or metamorphic rocks.

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.

Hydrothermal explosions are a significant geological hazard in some active volcanic systems; however, the timing and triggering mechanisms of these explosions are poorly constrained. This study applies luminescence dating techniques to hydrothermal explosion deposits in the Yellowstone Plateau volcanic field to constrain explosion chronologies and evaluate potential triggering mechanisms. We tested four luminescence dating techniques: K-feldspar post-infrared infrared stimulated luminescence (pIRIR225), quartz blue light optically stimulated luminescence (BLOSL), quartz blue thermoluminescence (BTL), and quartz red thermoluminescence (RTL). The pIRIR225 and RTL protocols produce consistent age estimates that agree with independent radiocarbon ages and with the timing of the Pinedale deglaciation. This study focuses on two craters, Mary Bay, along the northern shore of Yellowstone Lake, and Pocket Basin in Lower Geyser Basin. The mean pIRIR225 ages from Mary Bay deposits (11.99 ± 0.68 ka) agree with previous radiocarbon constraints. The mean pIRIR225 results from Pocket Basin deposits (13.44 ± 1.06 ka) suggest a history of explosion following Pinedale deglaciation, followed by recent hydrothermal alteration. Luminescence dating techniques are a promising tool for reconstructing the timing of hydrothermal explosions in the Late Pleistocene and Holocene, helping to constrain recurrence intervals of the largest hydrothermal systems, informing risk, and improving hazard assessments.