THE ‘PUBLISHING AMATEURS’

The Upper Ordovician of North America is the Cincinnatian Series, named for the richly fossiliferous beds in the Ohio—Indiana—Kentucky tri-state area surrounding Cincinnati, Ohio. This area is near or beyond the southern extent of Pleistocene glaciation, so bedrock is exposed or covered only thinly with glacial sediments. Hillsides, stream beds and road cuts expose the interbedded shale and limestone Cincinnatian strata, and fossils virtually tumble from rocks into collecting bags. This physical backdrop of abundant fossils and layered strata has been an intellectual seed for more than a century and a half. Many now-famous palaeontologists grew up in Cincinnati, including R. S. Bassler, J. M. Nickles, C. Schuchert and E. O. Ulrich. Caster (1981) referred to early Cincinnati geologists as the ‘publishing amateurs’ or in the case of those just listed as the ‘amateurs-turned-professionals’.

Bryozoans and brachiopods are the most prolific Cincinnatian fossils, but trilobites and echinoderms are the prizes of these strata. Crinoids are the most abundant echinoderms of the Cincinnatian, but asteroids, cyclocystoids, edrioasteroids, rhombiferans and stylophorans are also known from these beds.

STRATIGRAPHIC CYCLES

At an estimated 20°S palaeolatitude, Cincinnatian sediments were deposited in a tropical, shallow-water epicontinental setting, approximately 440 million years before present. The composite outcrop section in Ohio consists of more than 300 m of interbedded fossiliferous limestones and shales. Eustatic sea level fluctuations and storms were apparently the dominant physical factors controlling sedimentation, and this produced a hierarchy of cyclical strata.