Professor Titus: I am associated with the Alan Devoe Bird Club. We operate the Wilson Powell Wildlife Sanctuary in Chatham, Columbia County. There is a prominent sandstone ledge on our property called Dorson’s Rock. We would like to know more about it and wonder if you can help us. — Elisabeth Grace, Chatham.
I had never heard of Dorson’s Rock, so I made arrangements to visit. First, though, I ran a search on the Alan Devoe Bird Club. I learned that they have been operating in Chatham for about half a century. They are devoted bird watchers and maintain an annual bird count at the preserve. The 95 acres they own is the site of many activities throughout the year. The Preserve is open to the public and there is a map available to guide visitors through the lands of the Preserve.
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Part II - published 6/2/11 in The Register-Star Online
By Robert Titus
Last week we began a trip to Dorson’s Rock, a fine ledge of sandstone at the William Powell Wildlife Sanctuary, located in Columbia County’s Chatham. The sanctuary is the property of the Alan Devoe Bird Club and its members were curious about the geological history of the site. They invited me out to take a tour last fall and I was happy to go and see. Last week I wrote about my first impressions of Dorson’s Rock. I judged that the ledge had an interesting Ice Age history. I could envision the great Hudson Valley glacier descending from the north and overriding the ledge carving it into its present form. But, after that, the story became difficult.
My biggest problem was identifying what geological unit was this. Every mass of rock belongs to something that we geologists call a “formation.” Formations are the basic units of geology. We travel around the country and whenever we find an outcropping, we seek to figure out exactly what formation it represents.
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