Jacobsville Formation

Jacobsville Sandstone is a red sandstone formation, marked with light-colored streaks and spots, primarily found in northern Upper Michigan, portions of Ontario, and under much of Lake Superior. Desired for its durability and aesthetics, the sandstone was used as an architectural building stone both locally and around the United States. The stone was extracted by thirty-two quarries throughout the Upper Peninsula approximately between 1870 and 1915.

The sandstone has been variously called redstone, brownstone, Lake Superior Sandstone, and Eastern Sandstone. In 1907, the Jacobsville Formation was given its current classification and the name Jacobsville, in honor of Jacobsville, Michigan, a town known for its production of the sandstone. There is disagreement regarding the age of the sandstone, though it dates to sometime between the Mesoproterozoic Era and the Middle Cambrian. The formation is of terrestrial origin and is entirely devoid of fossils.

The earliest geologic studies of southern Lake Superior were made in the early 1800s. Many studies used the term Lake Superior Sandstone to describe a number of different geologic formations. Differentiation of the sandstone largely centered on an east-west division across the Keweenaw Peninsula or between the lower red and upper grey sandstones. The current definition for the Jacobsville Formation was made in 1907 by A. C. Lane and A. E. Seaman, in which the various Lake Superior sandstones were divided into the Jacobsville, Freda, and Munising. The Jacobsville reflects the sandstones described as either lower red or Eastern. They also introduced the name Jacobsville in honor of Jacobsville, Michigan, a town notable for its production of the sandstone including the "famous Portage Redstone".

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