Late Pleistocene paleohydrology near the boundary of the Sonoran and Chihuahuan Deserts, southeastern Arizona, USA

Pigati, Jeffrey S.; Bright, Jordon; Shanahan, T. M.; Mahan, Shannon A.

doi:10.1016/j.quascirev.2008.09.022

Cited by 64 publications

(59 citation statements)

References 56 publications

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“…Brennan and Quade also determined the 14 C content of 1 aliquot of Succinea shells from pre-Wisconsin spring deposits, which returned a 14 C age of 40.3 ± 0.8 14 C ka, or ~0.7 pMC, indicating a small amount of open-system behavior. Pigati et al (2004Pigati et al ( , 2009) dated terrestrial gastropod shells from late Pleistocene spring deposits in southeastern Arizona and found stratigraphically consistent 14 C ages for shells that ranged from ~25-11 14 C ka. Finally, Pigati et al (2010) dated 18 aliquots of fossil gastropod shells and 5 aliquots of plant macrofossils from a 5-cm-thick organic silt within glacial deposits from the Midwestern USA.…”

Section: Introductionmentioning

confidence: 99%

Assessing Open-System Behavior of ¹⁴C in Terrestrial Gastropod Shells

et al. 2011

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ABSTRACT. In order to assess open-system behavior of radiocarbon in fossil gastropod shells, we measured the 14 C activity on 10 aliquots of shell material recovered from Illinoian (~190-130 ka) and pre-Illinoian (~800 ka) loess and lacustrine deposits in the Midwestern USA. Eight of the 10 aliquots yielded measurable 14 C activities that ranged from 0.25 to 0.53 percent modern carbon (pMC), corresponding to apparent 14 C ages between 48.2 and 42.1 ka. This small level of open-system behavior is common in many materials that are used for 14 C dating (e.g. charcoal), and typically sets the upper practical limit of the technique. Two aliquots of gastropod shells from the Illinoian-aged Petersburg Silt (Petersburg Section) in central Illinois, USA, however, yielded elevated 14 C activities of 1.26 and 1.71 pMC, which correspond to apparent 14 C ages of 35.1 and 32.7 ka. Together, these results suggest that while many fossil gastropods shells may not suffer from major (>1%) open-system problems, this is not always the case. We then examined the mineralogy, trace element chemistry, and physical characteristics of a suite of fossil and modern gastropod shells to identify the source of contamination in the Petersburg shells and assess the effectiveness of these screening techniques at identifying samples suitable for 14 C dating. Mineralogical (XRD) and trace element analyses were inconclusive, which suggests that these techniques are not suitable for assessing open-system behavior in terrestrial gastropod shells. Analysis with scanning electron microscopy (SEM), however, identified secondary mineralization (calcium carbonate) primarily within the inner whorls of the Petersburg shells. This indicates that SEM examination, or possibly standard microscope examination, of the interior of gastropod shells should be used when selecting fossil gastropod shells for 14 C dating.

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Section: Introductionmentioning

confidence: 99%

Assessing Open-System Behavior of ¹⁴C in Terrestrial Gastropod Shells

et al. 2011

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“…1). Our research group investigated these sites previously to reconstruct late Quaternary climatic and hydrologic change in arid settings in the Americas (20)(21)(22)(23). Examination of deposits in these regions allowed us to evaluate the occurrence of markers in black mats of different ages and in different hemispheres, including localities far removed from the presumed impact location and its fallout.…”

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Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis

Pigati

Latorre

Rech

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The Younger Dryas impact hypothesis contends that an extraterrestrial object exploded over North America at 12.9 ka, initiating the Younger Dryas cold event, the extinction of many North American megafauna, and the demise of the Clovis archeological culture. Although the exact nature and location of the proposed impact or explosion remain unclear, alleged evidence for the fallout comes from multiple sites across North America and a site in Belgium. At 6 of the 10 original sites (excluding the Carolina Bays), elevated concentrations of various “impact markers” were found in association with black mats that date to the onset of the Younger Dryas. Black mats are common features in paleowetland deposits and typically represent shallow marsh environments. In this study, we investigated black mats ranging in age from approximately 6 to more than 40 ka in the southwestern United States and the Atacama Desert of northern Chile. At 10 of 13 sites, we found elevated concentrations of iridium in bulk and magnetic sediments, magnetic spherules, and/or titanomagnetite grains within or at the base of black mats, regardless of their age or location, suggesting that elevated concentrations of these markers arise from processes common to wetland systems, and not a catastrophic extraterrestrial impact event.

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“…From ∼50,000-13,000 14 C yBP (50,000-15,000 cal BP), southwestern Arizona was relatively wet (10). Large pluvial lakes were surrounded by hillsides covered with pinyon-juniper woodlands and rich understories of C 3 shrubs, C 4 annuals, and C 4 grasses (11,12); springs and shallow ponds were supported by a high water table (10); and a C 4 grassland stretched from southern Arizona to central Texas (12)(13)(14)(15)(16)(17).…”

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“…Large pluvial lakes were surrounded by hillsides covered with pinyon-juniper woodlands and rich understories of C 3 shrubs, C 4 annuals, and C 4 grasses (11,12); springs and shallow ponds were supported by a high water table (10); and a C 4 grassland stretched from southern Arizona to central Texas (12)(13)(14)(15)(16)(17). A warm and arid period began around 13,000 14 C yBP (15,000 cal BP), culminating in a severe drought that coincided with mammoth extinction and Clovis occupation of the SPV (10,900 14 C yBP or 12,800 cal BP) (18).…”

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Isotopic paleoecology of Clovis mammoths from Arizona

Metcalfe

Longstaffe

Ballenger

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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The causes of megafaunal extinctions in North America have been widely debated but remain poorly understood. Mammoths (Mammuthus spp.) in the American Southwest were hunted by Clovis people during a period of rapid climate change, just before the regional onset of Younger Dryas cooling and mammoth extirpation. Thus, these mammoths may provide key insights into late Pleistocene extinction processes. Here we reconstruct the seasonal diet and climatic conditions experienced by mammoths in the San Pedro Valley of Arizona, using the carbon ( 13 C/ 12 C) and oxygen ( 18 O/ 16 O) isotope compositions of tooth enamel. These records suggest that Clovis mammoths experienced a warm, dry climate with sufficient summer rainfall to support seasonal C 4 plant growth. Monsoon intensity may have been reduced relative to the preceding time period, but there is no isotopic evidence for severe drought. However, it is possible that the "Clovis drought", inferred from stratigraphic evidence, occurred suddenly at the end of the animals' lives and thus was not recorded in the enamel isotopic compositions. Unlike mammoths that lived before the Last Glacial Maximum, Clovis mammoths regularly increased C 4 grass consumption during summer, probably seeking seasonally green grasslands farther from the river valley. This predictable seasonal behavior may have made mammoths easier to locate by Clovis hunters. Furthermore, Clovis mammoths probably had no previous experience of such sudden climatic change as is believed to have occurred at the time of their extinction.geochemistry | stable isotopes | bioapatite | paleoclimate | Paleoindian

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Late Pleistocene paleohydrology near the boundary of the Sonoran and Chihuahuan Deserts, southeastern Arizona, USA

Cited by 64 publications

References 56 publications

Assessing Open-System Behavior of ¹⁴C in Terrestrial Gastropod Shells

Assessing Open-System Behavior of ¹⁴C in Terrestrial Gastropod Shells

Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis

Isotopic paleoecology of Clovis mammoths from Arizona

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Late Pleistocene paleohydrology near the boundary of the Sonoran and Chihuahuan Deserts, southeastern Arizona, USA

Cited by 64 publications

References 56 publications

Assessing Open-System Behavior of 14C in Terrestrial Gastropod Shells

Assessing Open-System Behavior of 14C in Terrestrial Gastropod Shells

Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis

Isotopic paleoecology of Clovis mammoths from Arizona

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Assessing Open-System Behavior of ¹⁴C in Terrestrial Gastropod Shells

Assessing Open-System Behavior of ¹⁴C in Terrestrial Gastropod Shells