Evidence for Multiple Holocene Marine Impact Events: Ejecta in a Bog Core

Details Evidence for Multiple Holocene Marine Impact Events: Ejecta in a Bog Core Evidence for Multiple Holocene Marine Impact Events: Ejecta in a Bog Core

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmpp23d1806a&link_type=abstract

American Geophysical Union, Fall Meeting 2006, abstract #PP23D-1806

Astronomy and Astrophysics

Astrophysics

6022 Impact Phenomena (5420, 8136), 8136 Impact Phenomena (5420, 6022)

Scientific paper

In a core from Tamarack Pond (a former bog) in the Hudson Highlands of New York, we found two layers containing marine microfossils. Because carbon rich sediments can be bioturbated over 20 cm depths, we give the layer thicknesses as 20 cm. The first layer is at 332-354 cm depth. It contains a radiolarian with a splashed on coating of Fe-Cr-Ni metal. It also contains a benthonic foraminiferal fossil. The second layer is at 432-454 cm depth. The second layer contains a degraded radiolarian fossil, a silicate with a splashed on coating of Fe-Cr-Ni metal, a carbon rich spherule containing Fe-Cr-Ni metal, and a grain of titanomagnetite with multiple craters. It also contains organic matter with Sn in it. As Tamarack Pond is quite far from the ocean, the marine fossils in the cores are unlikely to be windblown debris of Holocene age. A benthonic foraminifera is particularly unlikely to be blown by the wind. This conclusion is strengthened by the observation that the splashed on coating of Fe-Cr-Ni metal occurs in chondritic relative abundances with Fe>Cr>Ni. In grains with a thick layer of splashed metal, the Ni is sufficiently abundant to produce 3 distinct Ni peaks in the X-ray analysis. Such a high abundance of Ni coupled with chondritic relative abundances suggests that the Fe-Cr- Ni splash is derived from the vaporization of an extraterrestrial impactor. If we assume that the sedimentation rate of the Tamarack Pond core is the same as that of a previously dated core from nearby Sutherland Pond, the two layers have an uncorrected C-14 age of around 900-1200 B.C. for the layer at 332-354 cm and 2100 to 2400 B.C. for the layer at 432-454 cm. Both ages have a rough correspondence with times of climate downturn recorded in tree ring data (1159 and 2354 B.C.). These climate downturns cannot be explained by volcanic eruptions and are proposed to be cosmogenic in origin[1]. The older layer also corresponds in components to a previously studied circa 2350 B.C. impact ejecta layer[2]. [1]. Baillie, M., 1999, Exodus to Arthur: Catastrophic Encounters with Comets: London, UK, B. T. Batsford, 272 p. [2]. Courty, M.-A. et al. , 2006, Geoph. Res. Abs., vol. 8, A-01812.

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