Earth & Environmental Science Journalism:

Science Research Project

Using a high-resolution bog sediment core at Tamarack Pond, NY, to constrain an extraterrestrial impact in the Hudson Region ~2300 yr. B. P.

Veronica Phillips

Area under study, including sites of interest at Tamrack Pond, NY, and Carteret Canyon offshore of the New Jersey continental margin.


We examined a bog sediment core from Tamarack Pond, NY for evidence of impact ejecta around a previously constrained age horizon of 2300 yr. B.P.  This horizon approximately coincides with a tsunami event recorded in sediment cores from Long Island and in the Hudson River, which some hypothesize was triggered by a hypervelocity bolide impact on the eastern North American continental Margin.  We attempted to determine whether a connection existed between the cores at Tamarack Pond and the characteristics of a potential candidate for an impact site in Carteret Canyon located offshore of the New Jersey continental margin. We detected shocked minerals—including quartz—in the Tamarack Pond core as well as several spherules with great disparity in size, texture and color.  We considered the layer containing these grains to be the ejecta layer; however a thickness of 6 cm was several orders of magnitude greater than the ejecta layer thickness predicted by a computational model, using Carteret Canyon as the impact site.  The reasoning for this discrepancy may be related to bioturbation or the model’s failure to accurately represent processes that affect the distribution of distal ejecta. 

Impact scientists have identified a variety of shock metamorphic effects, both microscopic and macroscopic scale. This study focused on microscopic features. Prospective shocked quartz grains were identified on the basis of straight, parallel planar deformation features (PDFs) on mineral surfaces corresponding to approximate shock pressure and post shock temperature.
All grains potentially called shocked quartz came from three depth intervals as noted in brown/red above. No other shocked quartz candidates were identified outside of these depth intervals. This 6 cm layer (graphed above) is what was inferred to be the ejecta layer.
Twelve carbon-rich spherules or tecktites were found throughout the Tamarack Pond samples, with both smooth and pitted (above) surfaces. Carbon spherules could be the result of impact origin, forest fires, or a more unlikely cause would be from pollution. The disparity in the samples might indicate more than one mechanism is responsible for their presence in Tamarack Pond. Imaged using a Scanning Electron Microscope (SEM).



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Last updated: 8 January 2001, KAK.