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Palinspastic Restoration of the Eastern Laurentian Margin on the St. Lawrence Promontory, Western Newfoundland: Preliminary Results

John S. Allen and William A. Thomas
University of Kentucky, Department of Earth and Environmental Sciences, Lexington, KY 40506
[email protected]

The St. Lawrence promontory defines the Laurentian margin in western Newfoundland. There, Neoproterozoic through Carboniferous clastic, volcanic, and carbonate successions indicate protracted continental rifting and passivemargin thermal subsidence followed by destruction of the Laurentian passive margin during Paleozoic Appalachian orogenic cycles. Rocks of the Cambrian- Ordovician carbonate passive margin are host to an unknown quantity of oil and bitumen along the western coast of Newfoundland. Thus, understanding the structural and stratigraphic architecture of specific Paleozoic deformational cycles on the St. Lawrence promontory is important to constraining the development of these potential hydrocarbon plays.

A set of balanced cross sections has been constructed across the Laurentian margin in western Newfoundland to resolve the structure, stratigraphy, and timing of tectonic events on the St. Lawrence promontory. The cross sections were constructed with the use of geologic maps and field data from geologic mapping. Deep wells, a wide array of seismic reflection profiles, and digitized potential field data provide depth control for interpretation of Appalachian structures mapped at the surface.

Preliminary results indicate the Laurentian margin experienced four critical Paleozoic tectonic events after the development of the Cambrian-Ordovician passive margin: 1) Middle Ordovician thin-skinned emplacement of Taconic allochthons and ophiolites onto the continental margin; 2) post-Middle Ordovician loading of the margin and deposition of a thick Silurian-Devonian foreland basin fill; 3) post-Early Devonian (Emsian) westward emplacement of the Humber Arm allochthon into a tectonic wedge beneath the Silurian-Devonian basin; 4) premiddle Carboniferous (Visean) thick-skinned faulting along the margin.

AAPG Search and Discover Article #90087 © 2008 AAPG/SEG Student Expo, Houston, Texas