Chamberlain's Brook Formation

The Chamberlain's Brook Formation is a thin but distinctive geologic formation of dark red calcareous mudstones that crops out from Rhode Island to Massachusetts and, Nova Scotia, New Brunswick and Newfoundland. It preserves fossils, including trilobites, dating back to the lower mid-Cambrian period. Its lowermost member is the Braintree Member (lowest Middle Cambrian) and the uppermost member is the Fossil Brook Member.