|Classification:||Doline Devonian limestones of the Traverse Group|
|Bibliography:||Brochure at the Community Development Building near Maple Lane and Leer Road, Alpena.|
|Address:||Michigan Karst Conservancy, 2805 Gladstone Avenue, Ann Arbor, MI 48104-6432. E-mail:|
|Last update:||$Date: 2011/12/13 09:10:11 $|
|1993||purchased with gifts from William and Archie Stevens.|
The Stevens Twin Sinks Preserve was named after William C. and Archibald H. Stevens, who donated money for its purchase by the Michigan Karst Conservancy, and after two sinks of course. The center of the 1.2 ha preserve are two sinkholes, each about 60m in diameter and 25m deep, separated by a fragile saddle-ridge. A karst trail leading to this dolines and others was planned, but we could not find out if it is realized yet.
The area around Alpena and Presque Isle is formed by limestones of the Devonian Traverse Group. They are underlayn by Detroit River Group anhydrite, which dissolves much faster. The cavities undergound, about 230m below the surface, collapse and form huge dolines in the overlying rocks. This is also called a caprock doline, 200 of them exist in the Alpena area. Only the Stevens Twin sinks and the Bruski sink are open for public viewing.
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