Davenport Quarry – Geologic events in central New York

Geologic events in central New York span the last 400 million years of Earth history. Here we begin with some geologic features that are relatively recent. The Davenport quarry contains sand, gravel and cobbles that were deposited here by glaciers only 14 thousand years ago.

Cobbles transported on the surface of a glacier in France

Cobbles transported on the surface of a glacier in France.

At that time Charlotte Creek valley, where we are now standing, was a rather large lake. The valley was filled with water melting off of a nearby glacier. Glacial debris blocked one end of the valley, forming a very effective dam. The water collected behind this natural dam, creating a glacial lake. Smaller streams entering the valley from each side carried sediment that was deposited in small deltas along the lake shore. We are now standing in front of a glacial lake delta. The quarry wall in front of us contains cross-bedded gravels and sand, indicative of a glacial delta.

Large cross-beds of sand, gravel and cobbles

Large cross-beds of sand, gravel and cobbles, indicative of a delta that formed as a stream carried material into a glacial lake. Current direction was from right to left.

If you look carefully at the cobbles that are strewn around the quarry floor you will see that they are made out of many different rock types. Here we find cobbles of limestone, sandstone, shale, gneiss and granite.

Cobbles of white quartzite

Cobbles of white quartzite (upper left) and pink & black banded gneiss (bottom center).

How did these “exotic” cobbles arrive here in Davenport, where all the local bedrock is gray sandstone and shale? There’s a lot more to learn about glaciers and the last ice age !

What you have in your mind?