http://gallery.usgs.gov/images/logos/usgs_only.jpg http://gallery.usgs.gov/ en-us OC_Web@usgs.gov (Office of Communications Web Group) http://gallery.usgs.gov/images/USGS.gif http://gallery.usgs.gov/ http://gallery.usgs.gov/photos/10_14_2011_i4Dpg66ff0_10_14_2011_0 Photo of fossil algae (dinocyst). Specimen is about 90 micrometers across.The largest known impact crater in the U.S. lies buried beneath the Virginia Coastal Plain. The late Eocene Chesapeake Bay impact event caused a wide variety of distinctive features, such as fossil algae (dinocysts) that were found in drilled cores from hundreds to thousands of feet below the surface. The study of distinctive preservational features, whether related to the crater or not, leads to more questions than answers. How was a specific feature formed? How did it come to be preserved in the fossil record?

]]> http://gallery.usgs.gov/photos/11_18_2010_cHXj0NMa87_11_18_2010_0 USGS geologist Jeff Pigati (center) and personnel of the Denver Museum of Nature and Science examine an exposure of sediments at the Ziegler Reservoir site, Snowmass Village, Colo.

]]> http://gallery.usgs.gov/photos/11_18_2010_cHXj0NMa87_11_18_2010_1 Excavation of the initial Columbian mammoth remains found at the Ziegler Reservoir site.

]]> http://gallery.usgs.gov/photos/11_18_2010_cHXj0NMa87_11_18_2010_2 Denver Museum of Nature and Science personnel excavate a large mastodon tusk at the Ziegler Reservoir site.

]]> http://gallery.usgs.gov/photos/11_18_2010_cHXj0NMa87_11_18_2010_3 The Ziegler Reservoir site above Snowmass Village, Colo. The white tent in the background is the site of the original mammoth find.

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