Tectonic Influence on Sedimentation Patterns, Upper Ordovician of Eastern North America

Brian D. Keith

The upper part of the Champlainian Series and all of the Cincinnatian Series (both parts of the Upper Ordovician Series on the newly published COSUNA charts) can be divided up into seven time slices: the late part of the Blackriverian Age, Rocklandian, Kirkfieldian, Shermanian, Edenian, Maysvillian Ages, and early part of Richmondian Age. Analysis of the rocks, using these time slices in eastern North America, shows five regional facies packages: (1) clean carbonates, (2) mixed carbonates and terrigenous clastics, (3) shale, (4) terrigenous clastics coarser than shale, and (5) terrigenous clastics prograded over carbonates. The latter is considered a facies because this style of sedimentation is integral to the Upper Ordovician.

Regional tectonic events related to plate collision along the eastern margin of North America had a direct influence on the sedimentation pattern of these facies packages. The extensive clean carbonate platform represented by upper Blackriverian rocks was replaced by widespread argillaceous carbonates during Rocklandian, Kirkfieldian, and Shermanian time. Also, by Shermanian time, a linear belt of shale deposition bisected the carbonate platform from the southwest to the northeast. South of this trend, carbonate sedimentation continued essentially without interruption in response to tectonic stability until the end of the Ordovician Period. To the north, the carbonate platform deepened and was later flooded by shale during Edenian and Maysvillian time. Starting during the Maysvillian nd continuing into the Richmondian, upwarping and erosion of the Taconic highlands caused large-scale terrigenous clastic progradation over the northeastern part of the platform.

AAPG Search and Discovery Article #91041©1987 AAPG Eastern Section Meeting, Columbus, Ohio, October 7-10, 1987.