This study presents the geoarchaeological and chronometric analysis of two Late Pleistocene to Early Holocene archaeological sites: El Peregrino (PAIC-88) and Colina Castor (PAIC-91), located on Cedros Island, Baja California, Mexico. Both sites are situated at the base of fossil spring localities above modern sea level and contain stratified cultural materials associated with now-extinct freshwater sources that likely played a critical role in supporting early human occupation within an otherwise arid coastal setting. Bayesian chronological modelling, predicated on > 40 new radiocarbon measurements, places the onset of occupation at El Peregrino and Colina Castor during the Younger Dryas, with El Peregrino dating from 12,905 to 12,050 cal BP and Colina Castor from 12,780 to 12,105 cal BP. Stratigraphic and sedimentological data indicate site formation through a combination of alluvial fan deposition, aeolian input, and localised floralturbation around spring margins. Marine shell and lithic artifacts were transported inland as far as 15 km from the paleo-coastline during periods of lower sea level. These findings expand the known spatial and temporal range of Late Pleistocene coastal foragers in North America and highlight the importance of freshwater availability in structuring early human mobility and site selection along the Pacific coast. The Cedros Island record provides a rare inland perspective on early maritime adaptations during the transition from the Pleistocene to the Holocene.

Geoarchaeological excavations at the Cerro Pedregoso site on Cedros Island, Baja California, Mexico, uncovered a stratified alluvial fan deposit containing well-preserved evidence of repeated human occupation during the Early Holocene, between similar to 12,000 and 9600 cal BP. We used radiocarbon dating of wood charcoal and marine shell from multiple excavation units to establish a secure chronology for these early coastal forager occupations. These cultural materials lie within the landscape-scale Deposit 3, a unit formed by a combination of alluvial and aeolian processes. Beneath this deposit, a previously unknown paleosol (S1), exposed in excavation Unit 9, suggests the presence of even older sediments that may predate 12,000 cal BP. Although the archaeological content of this paleosol is sparse and affected by floralturbation, it offers a promising target for future investigations into the earliest coastal occupations of the Americas. The Cerro Pedregoso site thus provides a valuable stratified record of Early Holocene human activity and highlights the potential for even earlier evidence to be found in buried landforms on Cedros Island.

Nevada lies in one of the driest parts of North America. The region has long grappled with droughts and also with extended periods in which the already dry climate aridified for decades or centuries. Here we place Nevada’s most recent statewide drought (2020 – present) in the context of historical, archaeological and paleoclimate records dating back through the Mid-Holocene. The current drought is distinct from historical droughts that impacted the state in the 1930s, 1950s, and 1970’s and 1980s. It is notably warmer than droughts of the 20th century and more spatially extensive than any of these, although the 1930s drought also impacted much of the West. The early 2020s drought is also embedded within a two-decade long dry period, raising important questions about whether it is (1) drought, a relatively short period of abnormal dryness; (2) megadrought, a longer and typically more severe period of unusually dry conditions; (3) the manifestation of aridification, a shift toward a generally drier climate because of long-term precipitation declines and/or warming; or (4) some combination of the three. A broader view suggests that at least some aspects of drought since 2020 may not be unique. Paleoclimate evidence from cave deposits, lake and meadow sediments, animal middens, dead wood and tree rings indicate that Nevada and much of the western United States experienced decadal and centennial long dry periods in the Middle Holocene (5000 – 7000 years ago), the Late Holocene, (1800 – 3100 years ago), during the Medieval Climate Anomaly (1000 – 650 years ago) and again 600 – 500 years ago. The archaeological record shows that Indigenous Nevadans responded by repeatedly adapting to changing paleoenvironmental conditions. However, some key questions about fine-scale temporal and spatial variability in the experience of drought remain. Limitations in the spatial, seasonal and temporal resolutions of climate reconstructions—and in the observational record—may obscure the evidence for short or seasonally specific wet periods within longer dry periods or spatial variability in precipitation. Nonetheless, proxy and archaeological evidence from the last 10,000 years shows that understanding and responding to drought requires viewing drought on these time spans with an appreciation for the details that appear in modern observations.

We provide evidence from pollen and radiocarbon dating of wet meadow sediments for the presence of multi-centennial drought, termed the Late Holocene Dry Period (LHDP), in the central Great Basin be-tween 3100 and 1800 cal yr BP. We examine four sites along a south to north transect between 39 degrees N and 42 degrees N latitude, spanning the boundary of the anti-phasing dipole pattern of precipitation associated with ENSO. The LHDP conforms to the dipole pattern but contains three different phases, an initial 900-year dry period, followed by 200 years of wetter climate and then another 200 years of extreme drought. The dipole boundary appears to have shifted to a new semi-stable position with each period. Between 3100 and 2200 cal yr BP, the boundary seems to conform to the 40 degrees N parallel across central Nevada, and trending to 42 degrees N in northwest Nevada. Between 2200 and 2000 cal yr BP the boundary shifted south of 40 degrees N, when all sites predominantly record wet conditions. Between 2000 and 1800 cal yr BP the boundary shifts north to-41 degrees N, representing the driest phase which was widespread across central Nevada. A review of lake levels, tree-rings, and submerged stumps suggest that the drought between 2000 and 1800 cal yr BP was of greater magnitude than that recorded during the MCA megadrought. We do not yet have sufficient information to establish a cause for megadroughts, however it is important to note that the climate system periodically locks into a pattern with a consistently northward shifted storm track that persists for multiple decades to centuries, bringing persistent drought to the American Southwest. Indigenous human societies adapted to severe droughts through a variety of responses, suggesting a pattern of resilience and mobility in response to recurring climate change across the Great Basin.(c) 2022 Elsevier Ltd. All rights reserved.

The ancient human footprints in valley-bottom sediments in Tularosa Valley, New Mexico, are fascinating and potentially important because they suggest interactions between Pleistocene megafauna as well as great antiquity. The dating of those footprints is crucial in interpretations of when humans first came to North America from Asia, but the ages have larger uncertainties than has been reported. Some of that uncertainty is related to the possibility of a radiocarbon reservoir in the water in which the dated propagules of Ruppia cirrhosa grew. As a test of that possibility, Ruppia specimens collected in 1947 from nearby Malpais Spring returned a radiocarbon age of ca. 7400 cal yr BP. We think it would be appropriate to devise and implement independent means for dating the footprints, thus lowering the uncertainty in the proposed age of the footprints and leading to a better understanding of when humans first arrived in the Americas.

AbstractThe Late Holocene Dry Period (LHDP) was a one-plus millennial megadrought (3100–1800 cal BP) that delivered challenges and windfalls to Indigenous communities of the central Great Basin (United States). New pollen and sedimentation rate studies, combined with existing tree-ring data, submerged stump ages, and lake-level evidence, demonstrate that the LHDP was the driest Great Basin climate within the last 6,000 years—more extreme than the well-known Medieval Climatic Anomaly. New evidence reported here documents that most Great Basin archaeological sites south of 40° N latitude were abandoned during the long dry phase of the LHDP (3100–2200 cal BP), sometimes reoccupied during a wet interval (2200–2000 cal BP), and abandoned again during the most extreme drought (2000–1800 cal BP). Even in the face of epic drought, this is a story of remarkable survivance by some people who adjusted to their drought-stricken landscape where they had lived for millennia. Some moved on, but other resilient foragers refused to abandon their homeland, taking advantage of glacier-fed mountain springs with cooler alpine temperatures and greater moisture retention at high altitude, a result of early Neoglaciation conditions across many Great Basin ranges, despite epic drought conditions in the lowlands.

The place of the Clovis techno-complex in Great Basin culture history remains enigmatic, both in relation to the Western Stemmed Tradition - the dominant Paleoindian artifact complex in the Intermountain West - and to the range of late Pleistocene/early Holocene habitats that people employing Clovis toolkits utilized. Here we describe the Nye Canyon Paleo Site (26Ly930), located in the Pine Grove Hills in western Nevada. The Nye Canyon Paleo Site stands alone in the Great Basin because it contains both fluted points and Clovis-style blades alongside Western Stemmed Tradition points and other tools, sits at a relatively high elevation, and potentially contains buried cultural deposits. Recent test excavations failed to locate an intact buried Paleoindian component, but the Nye Canyon Paleo Site nevertheless demonstrates the use of Clovis and Western Stemmed technology at a single upper montane locality in the western Great Basin and highlights regional Paleoindian upper montane land use.

Understanding long-term responses of subalpine forest-parklands to Holocene climate variability in local context is critical for better managing those ecosystems under future climate change. Available records suggest that western North American subalpine forest-parkland ecosystems responded to Holocene climate in various ways at different places. Here we present a Holocene record of upper montane forest-parkland dynamics from Silver Lake in Big Cottonwood Canyon, Wasatch Range, on the Great Basin’s eastern margin. Our results show that at the end of the Younger Dryas, Silver Lake was surrounded by open Pinus/Picea parkland mixed with Artemisia subalpine steppe. By ~9.0 cal ka BP Picea began to expand in response to early Holocene summer warming and enhanced winter moisture. Picea-dominated forests prevailed from ~8.0 to 5.0 cal ka BP, after which time a more open Picea parkland developed. By ~3.5 cal ka BP Pinus increased under cooling conditions, and Picea gradually rebounded to form the mixed conifer forest present today. The Silver Lake long-term record of moderate shifts within an upper montane ecosystem is consistent with other regional sites in the timing of major vegetation changes reflecting large-scale climatic forcings, but distinct in response to local factors including the importance of enhanced lake-effect snowpack and the absence of competing lower montane Pinus. These local factors may help account for the long-term stability of Picea-dominated forests in the area.

The extent to which long-term climate change has influenced cultural evolution among hunter-gatherers has long been debated. In the Great Salt Lake desert (USA), a detailed record of paleoenvironmental change has been developed for the last 15,000 years, but a similarly complete chronicle of human occupation and adaptation is less secure. Here, we report and analyze one of the largest datasets (n = 247) of radiocarbon ages yet amassed from a single archaeological site in the Americas - Bonneville Estates Rockshelter, Nevada - to investigate human-environment interaction in this desert setting since 13,000 years ago. Results show a striking consistency in human-occupation intensity and oscillations between cool, mesic and warm, arid climate, specifically high occupation intensity during relatively cool times, and low intensity - even abandonment - during extended periods of drought. The ultimate outcome is a clear case of how long-term oscillations in climate can repeatedly motivate change in foraging societies in a marginal environmental setting. (C) 2021 Elsevier Ltd. All rights reserved.

ABSTRACTThe effects of climate change during the Terminal Pleistocene–Early Holocene transition on ecosystems and early Prearchaic hunter‐gatherers in the central Great Basin of North America are not well understood. We present a palynological reconstruction of regional vegetation and fire history in Grass Valley, central Nevada, from ~14 to ~7.5k cal a BP showing that Pinus‐dominated woodlands were replaced by dry‐adapted steppe and desert vegetation accompanied by an increase in regional fire activity at the beginning of the Holocene, in response to summer warming and a drying climate. Following a severe drought period peaking ~10.2–9.3k cal a BP, Pinus woodlands partially recovered contemporaneously with the 8.2k cal a BP climate anomaly. Local wetlands provided important resource patches for human foraging societies, and periodic declines of wetlands in response to changing local hydrological conditions may have necessitated adjustments in subsistence and settlement practices and technology.

The early archaeological record of Beringia is complicated by the occurrence of several lithic industries. Site assemblages, dating from 14,000 to 12,800 years ago and located from the Yana-Indigirka Lowlands of Siberia to the upper Tanana River basin, contain artifacts characteristic of the Nenana technological complex. After 12,800 years ago, site assemblages contain artifacts diagnostic of the Denali technocomplex. To explain the variation in lithic industries, we first and foremost need well-stratified and well-dated sites with multiple components so we securely know their ages and depositional relationships. We present excavation results of one such site located in interior Alaska, Owl Ridge, with the goal of assessing site stratigraphy, radiocarbon chronology, and natural site formation processes. Owl Ridge was visited three times during the Pleistocene-Holocene transition with a Nenana-complex occupation at 13,380-12,800 years ago followed by two Denali-complex occupations at 12,540-11,430 years ago and 11,270-11,200 years ago. Assemblage change at Owl Ridge was diachronically patterned, as at the nearby Dry Creek archaeological site, and separated by two climatic events, a brief extremely windy Younger Dryas (lasting 300-250 years) and a very brief wetter period (lasting similar to 160 years). Our results indicate these climate and environmental conditions played a role in settlement of eastern Beringia.

The Central Mountains Archaic began with the arrival of foraging populations in the Intermountain West about 6000 years ago. This migration coincided with the "extremely dramatic" winter-wet event of 4350 cal b.c. and the arrival of piñon pine forests in the central Great Basin. Human foragers likely played a significant role in the rapid spread of piñon across the central and northeastern Great Basin. Logistic hunters exploited local bighorn populations, sometimes serviced by hunting camps (the "man caves" such as Gatecliff Shelter, Triple T Shelter, and several others) and they staged communal pronghorn drives at lower elevations. As climate cooled and became more moist, logistic bighorn hunting gradually shifted downslope, then apparently faded away about 1000 cal b.c. Communal pronghorn driving persisted into the historic era in the central Great Basin. This volume, the first in the Alta Toquima trilogy, describes and analyzes more than 100 alpine hunting features on the Mt. Jefferson tablelands. High-elevation, logistical bighorn hunting virtually disappeared across the central Great Basin with the onset of the Late Holocene Dry Period (about 750-850 cal b.c.), giving way to an alpine residential pattern at Alta Toquima (26NY920) and elsewhere on Mt. Jefferson. Situated at almost exactly 11,000 ft (3352 m) above sea level, Alta Toquima was sited on the south summit of Mt. Jefferson (the third-highest spot in the state of Nevada), where at least 31 residential stone structures were emplaced along this steep, east-facing slope. When first recorded in 1978, Alta Toquima was the highest American Indian village site known in the Northern Hemisphere. This volume discusses the material culture, plant macrofossils, vertebrate fauna, and radiocarbon dating for Alta Toquima. Bayesian analysis of 95 14C dates documents an initial occupation of Alta Toquima at 1370-790 cal b.c., with the sporadic settlements persisting until immediately before European contact. These alpine residences are the most dramatic examples of the intensified provisioning strategies that began in the Central Mountains Archaic about 3000 years ago, broadening the diet breadth to include plant and animal resources previously considered too costly. The oldest summertime residence at Alta Toquima correlates with the onset of Late Holocene Dry Period (LHDP) aridity (~750 cal b.c.), and these houses were episodically occupied only during the driest intervals throughout the next 1500 dramatic years of abrupt climate change. During the intervening wetter stretches, Alta Toquima was abandoned in favor of subalpine basecamps. This sequenced intensification predated the arrival of bow technology in the central Great Basin by more than a millennium. Exactly the opposite sequencing took place a few miles to the north, when Gatecliff Shelter was abandoned during LHDP aridity--precisely when the first summertime settlements appeared at Alta Toquima. This pattern reversed again when lowland habitats became sufficiently well watered to again support summertime patches of seeds and geophytes (~150 cal b.c.-cal a.d. 100). Alta Toquima families responded by abandoning (temporarily) their alpine summertime camps to repurpose former "man caves" like Gatecliff and Triple T shelters into family settlements. The Monitor Valley sequence documents several syncopated lowland-alpine, wet-dry reversals, reflecting an adaptive diversity that spanned more than two millennia. The drought terminating cal a.d. 1150 devastated much of the western Great Basin and American Southwest, but its impact was less severe in central Nevada. Although subalpine sites were again abandoned during the drought buildup that peaked in the mid-12th century, summertime occupation of Alta Toquima became more commonplace, although it increased notably during the ~cal a.d. 1200-1400 aridity and persisted throughout the Little Ice Age.

Although the sediments of Lake Bonneville and its successor, the Great Salt Lake have been studied for over a century, there are few records of diatom floras from this area. Blue Lake warm spring is located near the Utah-Nevada border (40.5o N; 114.0o W; 1,297 masl) along the former western margin of late Pleistocene Lake Bonneville. The spring is a NaCl-dominated mesohaline brackish (3-10 o/oo) system with an elevated sulfate concentration. Core BL04-4 (822 cm long) was collected near the southwestern margin of the spring (Louderback and Rhode, 2009; L&R 09). The modern diatom flora is dominated by a diverse suite of benthic species, most of which are motile epipelic and epiphytic, and a few are tychoplanktic. There are few planktic taxa. There are a number of brackish and marine species, and a portion of the flora is endemic. Freshwater assemblages are generally better preserved. The diatoms from two downcore intervals (~44-27 ka and ~13-1 ka) were studied. The older interval is dominated by benthic taxa. Navicula spp. dominate the intervals between ~44-39 and ~37-31 ka; this group is briefly replaced within these intervals by halophilic taxa. The assemblage in the intervening period included freshwater tychoplanktic and heterotrophic benthic taxa. The former group is also abundant at ~28 ka. The younger interval contains an assemblage that more closely approximates the modern Blue Lake warm spring assemblage, with several species that are not present in the older interval. Tychoplanktic fragilarioids are more abundant in the early and late Holocene. The diatoms of the older interval are indicative of Lake Bonneville while those in the younger interval are affected by the waters emanating from the spring system. The 15,000-year record of vegetation change from core BL04-4 (L&R 09), identifying a local component of the flora affected by water availability at the spring, and pollen representing broader regional climate variability. Because of sampling differences, it is not possible to directly compare the diatom and palynofloras, but there is a qualitative similarity in changes in the abundance of cypreaceae pollen and fragilarioid taxa, both indicative of standing water. Louderback & Rhode, 2009, 15,000 years of vegetation change in the Bonneville basin: The Blue Lake pollen record: Quat. Sci. Rev. (28) 308-326.

We identified and dated 18 occupational events at eight sites dating to ~14.7–10.8kiloannum before present (ka BP) during a decade of archaeological survey and excavation on the northeastern high Tibetan Plateau (TP) >3200m. The ephemeral nature of the earliest sites suggests they were created by small foraging groups during very short stays. By ~12ka BP, larger foraging groups began to occupy sites >4000m leading to a more intensive occupation of the high TP after ~9.5ka BP. This archaeologically-based chronology closely matches genetically-based Tibetan population histories showing an early growth in population size and initial split with Han populations ~15–9ka BP, and a second spike in population growth during the early-mid Holocene. We found no evidence for occupation of the high TP prior to or during the Last Glacial Maximum (LGM), suggesting the initial separation of Tibetan and Han populations may have occurred at lower elevations in the TP margins or after the LGM in the high TP.