Title

Deformation Of The Subsurface Silurian And Devonian Rocks Of The Southern Tier Of New York State

Date of Award

1983

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

Advisor(s)

Ernest H. Muller

Keywords

Geology

Subject Categories

Geology

Abstract

Seismic, lithofacies, and structural interpretations are integrated into a tectonic model. For the Trenton (Middle Ordovician) to Tully (Middle Devonian) interval, subsurface lithofacies are mapped from well sample logs and compared with surface facies described in the literature, adding a third dimension to the stratigraphy.

While incorporating seismic and well data into a single mappable interpretation, a correction for glacial overburden velocity anomalies was devised to compensate for inadequate black box static corrections performed by seismic contractors and displayed on analog time sections.

The elusive decollement of the Allegheny Plateau is identified and mapped from repeat sections on gamma ray logs. The limits of surface folding mapped by Wedel are demonstrated to correspond to the edge of the "D" and "F" salt layers of the Salina Group as defined by Rickard. A detachment surface is found at three progressively lower stratigraphic levels (but topographically higher) from east to west within the Salina Group. In the eastern counties, Unit F (salt) sections of the Syracuse Formation are vertically repeated two and three times along splays originating at decollement. Fault throws as great as 400 feet are documented. The dome shape of the top of the Syracuse Formation and a planar base suggest a thin-skinned tectonic origin and negate the primary depositional thesis. In Steuben and Allegany Counties, Unit E sections are overthickened and the detachment surface is near the base of Unit E.

In Chautauqua County decollement terminates in a structure with northeast strike; here named the "Chautauqua Anticline". This thrust zone is of smaller proportions, but structurally comparable to the Burning Springs Anticline of West Virginia. At the northwest edge of the underlying salt beds, horizontal decollement bends upward forming structural petroleum traps: the targets for the recent plays in the Bass Islands and Akron Dolostones of the Rondout Group.

A decollement tectonic model for the southern tier is proposed in which individual buried fault blocks display differential movement above detachment zones. The blocks are comprised of internal low angle thrust sheets and are bounded by strike-slip faults with traces oriented generally north in the east to northwest in the west.

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