368 radiocarbon ages between 30 and 10 cal ka for samples collected from outcrops and shorelines from the Lake Bonneville basin have been compiled for this paper. Samples include 1. organic materials ...from sources outside the lake, such as wood, charcoal, plant fragments from emergent aquatics, and dispersed wetland organics, and 2. carbonate materials deposited in the lake, such as mollusk shells, tufa, charophyte debris, ooids, and marl. In general, organic materials provide rather than precise ages for lacustrine events, but their interpretation is less complicated than interpretation of results from carbonate samples. The data set shows evidence of contamination of different carbonate samples with both younger carbon and older carbon. For example, a radiocarbon reservoir at certain places within the lake during the middle transgressive phase accounts for ages of mollusk shells that are older than basal wood ages at similar altitudes. The large number of ages permits an accurate reconstruction of the lake chronology; conflicts between ages can be detected and reliable ages can be meaningfully integrated in interpretations. If fewer ages were available, the chronology might look simpler, but its accuracy would be unknown.
•368 radiocarbon ages from outcrops and shorelines have been compiled in this update.•New ages should be placed in the context of hundreds of ages that have already been obtained.•This compilation provides data for many different sub-disciplines of Quaternary science.•Ages for organic materials limit the time of lake occupation at particular altitudes.•In some cases carbonate ages show contamination from radiocarbon reservoirs or young carbon.
Bennett
. (Reports, 24 September 2021, p. 1528) report human footprints from Lake Otero, New Mexico, USA ~22,000 years ago. Critical assessment suggests that their radiocarbon chronology may be ...inaccurate. Reservoir effects may have caused radiocarbon ages to appear thousands of years too old. Independent verification of the ages of the footprint horizons is imperative and is possible through other means.
Ostracode faunas changed in Lake Bonneville as the lake rose in the closed basin and became more dilute, then overflowed, and eventually returned to closed-basin hydrology; alkalinity ...(carbonate + bicarbonate) increased throughout the lake history. Fossil-ostracode faunas in marl deposited in the lake between about 30 and 13 cal ka allow reconstruction of these geochemical changes (as shown by R. M. Forester), and permit stratigraphic correlations within the large lake basin, including into the Sevier subbasin, which was connected to the main body of the lake but had different inflowing rivers. The first ostracode to appear in Lake Bonneville deposits at low altitudes is
Limnocythere staplini
; it was replaced by
L. ceriotuberosa
as the lake got larger and the water became more dilute and alkaline.
Candona adunca
and several species of
Fabaeformiscandona
mark the freshest-water phases.
Cytherissa lacustris
appeared in lake-margin settings after lake level dropped and cold, fresh groundwater began to discharge into the lake.
Candona
sp. cf.
eriensis
lived in the Sevier subbasin during the transgressive phase of the lake, but did not appear in the main body until late in the regressive phase.
Limnocythere sappaensis
, which requires high alkalinity, showed up late in the regressive phase in the main body when lake level was very low.
Paleo-lakes in the western United States provide geomorphic and hydrologic records of climate and drainage-basin change at multiple time scales extending back to the Miocene. Recent reviews and ...studies of paleo-lake records have focused on interpretations of proxies in lake sediment cores from the northern and central parts of the Great Basin. In this review, emphasis is placed on equally important studies of lake history during the past ∼30 years that were derived from outcrop exposures and geomorphology, in some cases combined with cores. Outcrop and core records have different strengths and weaknesses that must be recognized and exploited in the interpretation of paleohydrology and paleoclimate. Outcrops and landforms can yield direct evidence of lake level, facies changes that record details of lake-level fluctuations, and geologic events such as catastrophic floods, drainage-basin changes, and isostatic rebound. Cores can potentially yield continuous records when sampled in stable parts of lake basins and can provide proxies for changes in lake level, water temperature and chemistry, and ecological conditions in the surrounding landscape. However, proxies such as stable isotopes may be influenced by several competing factors the relative effects of which may be difficult to assess, and interpretations may be confounded by geologic events within the drainage basin that were unrecorded or not recognized in a core. The best evidence for documenting absolute lake-level changes lies within the shore, nearshore, and deltaic sediments that were deposited across piedmonts and at the mouths of streams as lake level rose and fell. We review the different shorezone environments and resulting deposits used in such reconstructions and discuss potential estimation errors.
Lake-level studies based on deposits and landforms have provided paleohydrologic records ranging from general changes during the past million years to centennial-scale details of fluctuations during the late Pleistocene and Holocene. Outcrop studies have documented the integration histories of several important drainage basins, including the Humboldt, Amargosa, Owens, and Mojave river systems, that have evolved since the Miocene within the active tectonic setting of the Great Basin; these histories have influenced lake levels in terminal basins. Many pre-late Pleistocene lakes in the western Great Basin were significantly larger and record wetter conditions than the youngest lakes. Outcrop-based lake-level data provide important checks on core-based proxy interpretations; we discuss four such comparisons. In some cases, such as for Lakes Owens and Manix, outcrop and core data synthesis yields stronger and more complete records; in other cases, such as for Bonneville and Lahontan, conflicts point toward reconsideration of confounding factors in interpretation of core-based proxies.
•We review outcrop-based studies of Great Basin pluvial lakes over the past ∼25 years.•We provide examples of lake-level indicators using sedimentology and stratigraphy.•Studies on drainage-basin change and effects on paleohydrologic records are reviewed.•We compare outcrop and core-based records of Lakes Bonneville, Lahontan, and Owens.•Combined outcrop and core records can yield better insights on paleohydrology.
The initial colonization of the Americas remains a highly debated topic
, and the exact timing of the first arrivals is unknown. The earliest archaeological record of Mexico-which holds a key ...geographical position in the Americas-is poorly known and understudied. Historically, the region has remained on the periphery of research focused on the first American populations
. However, recent investigations provide reliable evidence of a human presence in the northwest region of Mexico
, the Chiapas Highlands
, Central Mexico
and the Caribbean coast
during the Late Pleistocene and Early Holocene epochs. Here we present results of recent excavations at Chiquihuite Cave-a high-altitude site in central-northern Mexico-that corroborate previous findings in the Americas
of cultural evidence that dates to the Last Glacial Maximum (26,500-19,000 years ago)
, and which push back dates for human dispersal to the region possibly as early as 33,000-31,000 years ago. The site yielded about 1,900 stone artefacts within a 3-m-deep stratified sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia. More than 50 radiocarbon and luminescence dates provide chronological control, and genetic, palaeoenvironmental and chemical data document the changing environments in which the occupants lived. Our results provide new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research.
The depositional history of the Bonneville Salt Flats, a perennial saline pan in Utah's Bonneville basin, has poor temporal constraints, and the climatic and geomorphic conditions that led to saline ...pan formation there are poorly understood. We explore the late Pleistocene to Holocene depositional record of Bonneville Salt Flats cores. Our data challenge the assumption that the saline pan formed from the desiccation of Lake Bonneville, the largest late Pleistocene lake in the Great Basin, which covered this area from 30 to 13 cal ka BP. We test two hypotheses: whether climatic transitions from (1) wet to arid or (2) arid to wet led to saline pan deposition. We describe the depositional record with radiocarbon dating, sedimentological structures, mineralogy, diatom, ostracode, and portable X-ray fluorescence spectrometer measurements. Gypsum and carbonate strontium isotope ratio measurements reflect changes in water sources. Three shallow saline lake to desiccation cycles occurred from >45 and >28 cal ka BP. Deflation removed Lake Bonneville sediments between 13 and 8.3 cal ka BP. Gypsum deposition spanned 8.3 to 5.4 cal ka BP, while the oldest halite interval formed from 5.4 to 3.5 cal ka BP during a wetter period. These findings offer valuable insights for sedimentologists, archaeologists, geomorphologists, and land managers.
We present a novel approach to developing a unified radiocarbon-based chronology for multiple sediment cores from a location where radiocarbon dating is challenging. We used 36 radiocarbon ages from ...eight terminal Pleistocene and Holocene sediment cores with correlated stratigraphies. Stratigraphic correlation was accomplished using a combination of high-resolution photography, high-resolution X-ray fluorescence-based elemental composition data, and volcanic tephra identification. Results show that despite problems associated with potential contamination or radiocarbon reservoir effect, a useful age-depth model has been created for the correlated lacustrine sections of these eight sediment cores, providing chronological controls for future paleoenvironmental analyses of the cores.
The Provo shoreline of Lake Bonneville formed following the Bonneville flood, and, based on previous dating, was formed during a period of overflow from about 17.5 to 15.0 cal. ka. In many places the ...Provo shoreline consists of a pair of distinct shorelines, one ∼3 m higher than the other. We present data from two cuts through double beaches to show that the upper beach is younger and represents sedimentation after a lake‐level rise. In addition, the lower beach deposits are internally stratified by beds that suggest three more lake‐level rises during its development. The Provo beach complex thus appears to have been built during rising lake levels, which can be explained by rises in the overflow threshold by sequential landslide deposition. Evaluation of beach altitudes demonstrates that the two beach crests throughout the Bonneville basin experienced equivalent rebound from removal of the lake load, and therefore they formed after the rebound associated with the Bonneville flood occurred in early Provo time. However, radiocarbon ages on gastropods collected within the beach deposits suggest both that the sequence of five beach deposits formed from c.18.1 to c. 17.0 cal. ka, and that the Bonneville flood occurred before 18 cal. ka. These ages are discordant with previous dates on shells within offshore sands, and raise questions about the validity of radiocarbon ages for shells in Lake Bonneville as well as about the age of the Bonneville flood and Provo shoreline. The timing for maximum Provo lake depths and its association with climate stages during deglaciation remain unresolved.
Stratigraphic descriptions and radiocarbon data from eleven field locations are presented in this paper to establish a chronostratigraphic framework for offshore to nearshore deposits of Lake ...Bonneville. Based on key marker beds and geomorphic position, the deposits are interpreted to have accumulated during the period from the late transgressive phase, through the overflowing phase, into the regressive phase of the lake. Radiocarbon ages of sediments associated with the Provo shoreline indicate that Lake Bonneville dropped rapidly from the Provo shoreline at about 12,600
14C yr BP (15,000 cal yr B.P.). The presence of one or more sand beds in the upper part of the Provo-aged marl indicates rapid lowering of lake level or storm events at the end of the Provo episode. An accurate understanding of the timing and nature of Lake Bonneville's climate-driven regression from the Provo shoreline is critical to correlations with records of regional and hemispheric climate change. The rapid descent of the lake from the Provo shoreline correlates with the decline of Lakes Lahontan and Estancia, and with the onset of the B
Ølling–Aller
Ød warming event.
► Analysis and radiocarbon data from stratigraphic sections refine lake-level history. ► Lake level dropped abruptly at the beginning of the regressive phase. ► Provo shoreline formation ceased approximately 12,600
14C yr BP. ► The regression corresponds with onset of the global B
Ølling-Aller
Ød warming event.
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