Joint sets are of interest since they control the migration of hydrocarbons and natural gas through the Antrim. Don Oliver thought these were mudcracks in the Antrim. The Antrim shale is famous for the huge spherical concretions it contains. Here's Melody next to one of those giant concretions. Houwaida and Melody next to a broken concretion showing the internal structure of radiating calcite crystals.
Black calcite is found in some concretions due to the abundance of organic hydrocarbons.
Mike, resting on a concretion, surveying the Paxton quarry. Some concretions form nodular masses. Don Oliver explaining concretion formation to Andrew and Brooks in the Paxton shale quarry. After lunch, we examined the limestone outcrops at Partridge Point which extends outward into Thunder Bay of Lake Huron. Houwaida searching for fossils in the Thunder Bay Limestone.