Abstract: The Three Lithofacies of the Bass Islands Formation (Upper Silurian) in eastern Ohio

ARIE JANSSENS
Granville, Ohio

In a continuing study of Lower and Middle Devonian carbonates in the subsurface of eastern Ohio, it has been found that the Bass Islands occurs in three lithofacies. Areally most extensive is the lithology found on the Lake Erie islands: brown or gray laminated dolomicrite or dolosiltite that in many places in northeastern Ohio is overlain by gray shale and anhydrite, each of which is a few ft thick. Locally in southeastern Ohio, a sandy lithofacies completely or, more commonly, partly replaces the dolomite lithofacies and is made up of light gray sandstone consisting of very fine angular sand or of siltstone. This sandy lithofacies occurs as far north as Muskingum County and as far east as Harrison County and is probably represented by the sandstone reported from the same stratigraphic position in the Sandhill deep test in Wood County, West Virginia. The sandstone reaches a maximum thickness of 30 ft in Meigsville Township, Morgan County. In Belmont County and parts of adjacent counties a third lithofacies almost entirely replaces the dolomite lithofacies; it consists of pale-gray dolosiltite probably less than 10 ft thick underlain by as much as 40 ft of dark-brown lithographic to dense limestone that is indistinguishable from basal Helderberg limestone.

Thickness of the Bass Islands Formation ranges up to 50 ft. The formation's boundaries with the underlying Salina G anhydrite and with the overlying Helderberg Formation are considered conformable.

AAPG Search and Discovery Article #90930©1998 AAPG Eastern Section, Columbus, Ohio