This may not be the most appropriate forum for this thread, but it arguably pertains to archeaology. Actually, a Geology forum would be ideal. Say, Ben, how about making a geology forum?
http://gothamist.com/2008/09/22/traces_of_the_ice_age_at_ground_zer.php
September 22, 2008
Traces of the Ice Age at Ground Zero
The NY Times reports on evidence of the Ice Age that has emerged at Ground Zero, thanks for the huge excavation project there. It sounds stunning--"plummeting holes, steep cliffsides and soft billows of steel-gray bedrock, punctuated by thousands of beach-smooth cobblestones in a muted rainbow of reds and purples and greens." The area has been called the "Grand Canyon of Lower Manhattan," thanks to a glacier from 20,000 years ago. A geologist for Mueser Rutledge Consulting Engineers said, “As the ice passed over New Jersey, it picked up local rocks such as red shale and sandstone and gray basalt from the Palisades. As ice melted from the advancing glacier, raging streams of water flowed in front of it. The strong currents picked up the sand, gravel and boulders and carried them downstream across the World Trade Center site."
http://gothamist.com/2008/09/22/traces_of_the_ice_age_at_ground_zer.php