Paleoindian demography and the extraterrestrial impact hypothesis

Buchanan, Briggs; Collard, Mark; Edinborough, Kevan

doi:10.1073/pnas.0803762105

Cited by 109 publications

(111 citation statements)

References 18 publications

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“…In North America at least 17 genera of megafauna (e.g., mammoths, mastodons, giant short-faced bears, saber-tooth tigers, and numerous other megafauna species) became extinct near the YD onset, although the details of the chronology are in question (7,8). North America's earliest known human populations arrived and dispersed prior to the YD, and their Clovis lithic technology disappeared from the sedimentary record near the onset of the YD (9,10). Although the YD climate reversal as well as the geologically abrupt Pleistocene megafauna extinctions and disappearance of the Clovis culture are not disputed, their causes are matters of intense debate.…”

Section: Uring the End Of The Last Glacial Period In The Northernmentioning

confidence: 99%

No evidence of nanodiamonds in Younger–Dryas sediments to support an impact event

Daulton

Pinter

Scott

2010

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

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The causes of the late Pleistocene megafaunal extinctions in North America, disappearance of Clovis paleoindian lithic technology, and abrupt Younger-Dryas (YD) climate reversal of the last deglacial warming in the Northern Hemisphere remain an enigma. A controversial hypothesis proposes that one or more cometary airbursts/ impacts barraged North America ≈12,900 cal yr B.P. and caused these events. Most evidence supporting this hypothesis has been discredited except for reports of nanodiamonds (including the rare hexagonal polytype) in Bølling-Ållerod-YD-boundary sediments. The hexagonal polytype of diamond, lonsdaleite, is of particular interest because it is often associated with shock pressures related to impacts where it has been found to occur naturally. Unfortunately, previous reports of YD-boundary nanodiamonds have left many unanswered questions regarding the nature and occurrence of the nanodiamonds. Therefore, we examined carbon-rich materials isolated from sediments dated 15,818 cal yr B.P. to present (including the Bølling-Ållerod-YD boundary). No nanodiamonds were found in our study. Instead, graphene-and graphene/ graphane-oxide aggregates are ubiquitous in all specimens examined. We demonstrate that previous studies misidentified graphene/graphane-oxide aggregates as hexagonal diamond and likely misidentified graphene as cubic diamond. Our results cast doubt upon one of the last widely discussed pieces of evidence supporting the YD impact hypothesis.archaeology | paleoclimate | Quaternary extinctions | carbon spherules | fungal sclerotia

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Section: Uring the End Of The Last Glacial Period In The Northernmentioning

confidence: 99%

No evidence of nanodiamonds in Younger–Dryas sediments to support an impact event

Daulton

Pinter

Scott

2010

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

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“…Buchanan et al (1) correctly identify accurate Paleoindian population estimates as an important test of the Younger Dryas boundary (YDB) extraterrestrial impact hypothesis (2). They claim that cumulative probabilities of 628 14 C-dated components provide evidence for population continuity across the YDB.…”

mentioning

confidence: 99%

Standards of evidence and Paleoindian demographics

Kennett

Stafford²,

Southon

2008

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

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“…Shortly after the impact hypothesis was proposed, critics began questioning whether some of the markers were necessarily related to an ET impact event (5-11), whereas others argued against the hypothesis after they were unable to find supporting evidence in other depositional settings (12,13) or existing datasets (4,14). Still others raised concerns over issues of replicability and laboratory protocols used in the original study (15).…”

mentioning

confidence: 99%

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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Paleoindian demography and the extraterrestrial impact hypothesis

Abstract: Recently it has been suggested that one or more large extraterrestrial (ET) objects struck northern North America 12,900 ؎ 100 calendar years before present ( comet ͉ Clovis ͉ population decline ͉ radiocarbon ͉ summed probability distribution

Cited by 109 publications

References 18 publications

No evidence of nanodiamonds in Younger–Dryas sediments to support an impact event

No evidence of nanodiamonds in Younger–Dryas sediments to support an impact event

Standards of evidence and Paleoindian demographics

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

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