The Holland Quarry is a black shale formerly exposed at a single outcrop located near Toledo, Ohio. Local stratigraphic relations and the carbonaceous nature of the shale suggest that it was deposited in a small, stagnant embayment occupying a previously eroded channel. Regional stratigraphic relations indicate that at the time of deposition (Gedinnian or Early Siegenian) of the shale the Michigan Basin and adjacent areas of the craton were emergent; the nearest contemporaneous marine rocks are located in southeastern Ohio.
The Holland Quarry fossil assemblage is a mixture of marine, brackish, and terrestrial elements suggestive of deposition in an estuarine environment. The dominant endemic forms consist of nektonic and vagrant benthonic fishes and eurypterids, indicating that the oxygen-deficient environment was largely confined to the substrate. Neither the length nor the location of the mouth of the estuary can be determined from presently available information.