Stratigraphic and structural relationships among rock groups at Old Mans Pond, west Newfoundland

Gillespie, Randall Thomas (1983) Stratigraphic and structural relationships among rock groups at Old Mans Pond, west Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Old Mans Pond area is positioned between the Humber Arm Allochthon to the west and the exposed eastern edge of the Appalachian miogeocline east of Deer Lake, thus providing a unique opportunity to study a complete section across the deformed ancient continental margin of eastern North America. The geology of the area demonstrates virtually all elements of the relict margin including, from northwest to southeast: (1) an autochthonous Paleozoic carbonate bank sequence including the well known St. George and Table Head Groups and lesser known Reluctant Head and Penguin Cove Formations; (2) a previously unrecognized allochthonous rise prism clastic sequence (Old Mans Pond Group) which is similar to, and may have at one time been continuous with, the Curling Group of the Humber Arm Allochthon; (3) a newly recognized structural slice (Hughes Lake Allochthon) involving Grenvillian basement rocks (Round Pond Complex) and a thick clastic cover sequence (Mount Musgrave Group) correlative in part with the Labrador Group and Fleur de Lys Supergroup. Carboniferous strata of the Deer Lake Basin overlie older Paleozoic rocks in the area with profound unconformity. -- Structurally the Old Mans Pond area is dominated by an imbricate stack involving the allochthonous assemblages mentioned above. Structural evidence and regional tectonic considerations indicate that the stack was assembled from the east and emplaced against the autochthonous carbonate sequence during the Taconic Orogeny. Deformation was polyphase in nature and westerly time transgressive. Early fabrics which are evident in the transported sequences are not present in the carbonate sequence implying that the carbonate bank was not involved in the earliest stages of the Taconic. Later involvement is evident from the ommission of much of the carbonate sequence beneath the Old Mans Pond Allochthon. -- Subsequent orogenic activity (Acadian?) is responsible for overturning thrusts and fabrics generated during the Taconic, thus producing the marked reversal in structural polarity which characterizes the area. The Acadian Orogeny had little other effect on the area due to its sheltered position northwest of a minor reentrant in the ancient margin. -- The Alleghanian Orogeny evidently had little effect on the area since Carboniferous strata along the western margin of the Deer Lake Basin are undeformed.

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