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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Biostratigraphic evidence supports Paleoindian population disruption at 12.9 ka
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Biostratigraphic evidence supports Paleoindian population disruption at 12.9 ka

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摘要

Buchanan et al. (1) interpret an 40 reduction in the cumulative probabilities of radiocarbon dates at the beginning ofthe Younger Dryas (12.9 ka) as noisy data inconsistent withhuman population decreases predicted by the extraterrestrialimpact hypothesis (2). This reduction is, in fact, consistentwith other biostratigraphic evidence suggesting an abrupt environmentalperturbation at the onset of the Younger Dryasaffecting human populations. Haynes (3) described a blacksedimentary layer at 70 localities across North America datingto 12.9 ka as a stratigraphic marker horizon—where Clovisartifacts and select Rancholabrean fauna occur just below, butnever within or above. Archeological sites containing bothClovis and immediately post-Clovis material are rare and,where present, are nearly always separated by culturally sterilesediments. Of the 11 well-dated credible Clovis sites (4), nonehas post-Clovis materials immediately above, suggesting a potentialdisruption in settlement or landscape use. The Clovisagematerial at Blackwater Draw in New Mexico is poorlydated but is capped by a black sedimentary layer indicating aterminal age of 12.9 ka as summarized by Haynes (3) and referencestherein. Folsom-age materials occur above the Clovismaterials, but a hiatus of 500 years is suggested by an interveningsterile deposit (10–35 cm) and radiocarbon ages of12.4–11.8 ka (3). This is also the case at the well-dated Clovisdeposits at Shawnee-Minisink (12.9–12.8 ka) in Pennsylvania,which are separated from an upper Early Archaic deposit(11.5 ka) by 1.71 m of sterile deposits (5). When biostratigraphicand radiocarbon evidence are taken together, theypoint to a post-Clovis decline in human populations consistentwith the Younger Dryas impact hypothesis.

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