Upper Ordovician Blue Mountain Formation in Southwestern Ontario, Canada: Progress toward High Frequency Allostratigraphic Correlation to the Utica Shale in Ohio and Pennsylvania
Sweeney, Sarah; Cheadle, Burns
Recent activity in the Upper Ordovician Utica Shale play has underscored the need to understand the Utica and correlative strata in the context of the genesis of the Appalachian Basin. Recent stratigraphic correlations in the Taconic foredeep illustrate the response of depositional systems to the interplay between eustacy, basin tectonism and circulation. The question remains, however, how these mechanisms interacted at the distal edge of the foredeep where accommodation may have been strongly influenced by movement of the putative forebulge. In particular, the relationship between productivity and preservation of organic matter and modes of mudstone deposition in a forebulge setting has broad implications for development of carbonaceous mudstone petroleum systems.
The Upper Ordovician Collingwood Member and overlying Blue Mountain Formation of Southwestern Ontario are contrasting carbonaceous mudstones that were deposited in the Taconic forebulge region. Although stratigraphic correlations are currently equivocal, the carbonaceous mudstone of the Rouge River Member of the Blue Mountain Formation may be correlative to the uppermost Utica Shale in Pennsylvania and Ohio. Correlation between the Collingwood Member and the Point Pleasant Formation is more speculative. Both units developed in response to foundering of the Trenton carbonate platform during Taconic loading, with the Collingwood probably slightly postdating the Point Pleasant as the collapse propagated northward. The presence of a regionally extensive phosphatic lag at the sharp Collingwood-Blue Mountain contact suggests a depositional hiatus, possibly associated with uplift, punctuates the Upper Ordovician record in Southwestern Ontario.
Although numerous wells penetrate the Upper Ordovician in Ontario, the subsurface stratigraphy of the strata is not well-defined. Our approach is to use digital well log data in combination with core description, paleontological data, and petrophysical analysis to construct a high-frequency allostratigraphic framework of the Blue Mountain Formation in Southwestern Ontario. This provides the context in which to address the absolute temporal relationship between the Ontario stratigraphic record and the Utica-Point Pleasant succession in Ohio and Pennsylvania. This will pave the way for future analysis of the high-frequency stratigraphic response to far-field flexural tectonism in the Appalachian Basin.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013