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Based on elevated concentrations of a set of “impact markers” at the onset of the Younger Dryas stadial from sedimentary contexts across North America, Firestone, Kennett, West, and others have argued that 12.9 ka the Earth experienced an impact by an extraterrestrial body, an event that had devastating ecological consequences for humans, plants, and animals in the New World [Firestone RB, et al. (2007) Proc. Natl. Acad. Sci. USA 104:16016–16021]. Herein, we report the results of an independent analysis of magnetic minerals and microspherules from seven sites of similar age, including two examined by Firestone et al. We were unable to reproduce any results of the Firestone et al. study and find no support for Younger Dryas extraterrestrial impact.

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A silty mantle on the upper Eastern Shore of Maryland was studied to determine its origin and characteristics. Thickness of the silts was studied by selecting traverses in an east‐west direction from the Chesapeake Bay and also scattered borings between traverses. These deposits are believed to be loess; they are characterized by 50 to 75% silt‐sized particles. The material is also carbonatefree, nonstratified, and yellowish brown in color. In addition, the silty mantle shows a reduction in thickness and particle size with increasing distance from the Chesapeake Bay, which was the probable source area. In areas of thin loess (< 90 cm), increasing amounts of sand were apparently incorporated into the loess at the time of deposition. Based on 14C date of a 11A1b horizon of a buried paleosol below the loess, deposition of the silts took place after 10,520 ± 240 years B.P. Profile characteristics of soils developed in the loess show moderately well expressed argillic horizons with the soil in this study having an increase of 9% clay from the A to the B2t horizon or a B2t/A clay ratio of 1.65.

Cactus Hill is located in the Virginia Coastal Plain on a terrace above the Nottoway River. The site has a record of occupation that spans the Holocene and also offers evidence of humans late in the Pleistocene before Clovis time. Soil investigations identified several deposit types, and demonstrated that multisequal eolian sands forming the site's primary core are arrayed in spatially and temporally discrete horizons. Resting atop an ancient paleosol, the earliest sand stratum (19,540 ± 70 14C yr B.P.) is marked by a conspicuous but culturally sterile buried surface horizon. Eolian sand above this surface supports another sequum in which Clovis and underlying “Blade” artifacts are associated with a fainter surface horizon and pronounced subsoil lamellae. Early Archaic and successively younger artifacts occur above the Clovis level in a more weakly developed uppermost sequum. This soil and cultural stratigraphy, together with considerations of regional topography, demonstrate that the landscape has evolved incrementally since about the last glacial maximum. © 2004 Wiley Periodicals, Inc.