Notes from the Field: Ancient Oysters

“Recently we were collecting sediment cores in New York in support of a harbor deepening project. The goal was simple, penetrate deeply until the glacial till is reached. This was a reasonable goal for one of our heavy-duty vibracoring systems. When the sample was retrieved and split open we discovered a strata of oyster shells from an ancient bed that most likely dates back to the Pleistocene era (1.8 million to 10,000 years ago).”

-Don Nazario, Senior Environmental Scientist, Aqua Survey, Inc.

The shell layer which Don found last week is just one reminder of the rich geological and biological history of New York City and its surrounding waterways. The region and harbor owes much of its current configuration to the last ice age when the Laurentide ice sheet advanced and retreated over a period of 60,000 years, reaching its last peak 22,000 years ago.  New York City marked the southernmost extension of the ice sheet, which covered hundreds of thousands of square miles in what are now Canada and the northern United States. Ten thousand years ago global warming accelerated and the region went through drastic changes.  Spruce and tundra were quickly replaced by pine forests and the mammoths and mastodons which once thrived in the region died out.  These transformations are thought to possibly have happened within the lifespan of a human being.  It’s intriguing to imagine how the Paleo-Indians survived such rapid changes.

At its tallest the Laurentide ice sheet covered New York City with a thousand feet of ice.  If New York City was to be covered in that much ice today, only a handful of buildings would poke through, the most prominent being the Empire State Building.

-Part 1 of a 3-part Series on the Deepening of New York Harbor-