The Jacobsville Formation outcrops significantly throughout the Upper Peninsula, with lesser exposures in Ontario and Wisconsin [REF].
Estimates for the age of the formation range from the late Mesoproterozoic Era (about 1.03 to 1.07 billion years ago)[REF] to Middle Cambrian,[REF][REF] though early geologists believed that it may have dated from as recently as the Upper Cambrian [REF].