Mackenzie Gordon

LATE DEVONIAN AMMONOIDS FROM OHIO AND ADJACENT STATES

Three late Devonian ammonoid-bearing levels are described from the area of Cleve- land, Ohio. These appear to represent the German Platyclymenia, Clymenia and Wocklumeria Stufen, clear evidence for which has been lacking previously in eastern North America. The lowest level, around the base of the Cleveland Shale, yields Sporadoceras, Cyrtoclymenia, Platyclymenia and a new species, Pleuroclymenia (?) ohioense. The middle level, near the top of the Cleveland Shale, bears Cymaclymenia, Sporadoceras and Prionoceras. The highest level, just above the base of the Bedford Shale, has Prionoceras quadripartitum. This species, and a fauna of the basal Bedford, have been located also in the area of Columbus, Ohio. An Epiwocklumeria (?) sp. is recorded from Indiana. Attention is drawn to the international importance of the late Famennian and Lower Carboniferous ammonoid sequence which can now be recognized in Ohio.

New evidence for the age of the Quantico Formation of Virginia

A new fossil locality within the Quantico Formation of the Virginia Piedmont in Dale City, Virginia, about 40 km south of Washington, D.C., has yielded crinoids and a cephalopod that re-establishes an age younger than Cambrian for this formation. On the basis of regional considerations and the work of investigators in the early 1900s, an Ordovician age for the Quantico seems likely. Also, the Dale City pluton is not intrusive into the Quantico but is unconformable beneath it. Hence, the 560-m.y. zircon age for the Dale City pluton is no longer inconsistent with the temporal and stratigraphic relationships established for the stratigraphic units in the area.