13-Reef dolostone

Dolostone reef rock showing open "vuggy" character and altered (dolomitized) fossils. Rock is part of an ancient barrier reef (the Fort Wayne Bank) that extended around the southern end of the Michigan Basin during Late Silurian time, about 420 million years ago. The reef grew in warm shallow seawater that flooded the Midwest for millions of years. Block is from the middle of the rock sequence in the May Stone and Sand quarry, the only place where the Fort Wayne Bank is exposed.