Crestal Unconformities as Indicators of Clastic Stratigraphic Traps: Genetic Relation of Berlin Field and Elk City Structure, Deep Anadarko Basin: ABSTRACT

Abstract

The Berlin fan-delta gas reservoir in the deep Anardarko basin was deposited during the late Atokan (Pennsylvanian) as a response to the initial uplift and erosion of the Elk City structure. During the late Atokan pulse of the episodic Pennsylvanian orogeny in the south-central US, abrupt epeirogenic uplift and brittle deformation created an interregional unconformity on positive areas around foreland and cratonic basins. The Elk City structure within the deep Anadarko basin originated as a distinct, subaerially exposed upthrust-block during the late Atokan tectonic event. A crestal unconformity developed on the emergent upthrust block concurrent with its uplift. Terrigenous, detrital Atoka dolomite, originally sourced from the Arbuckle dolomite (Cambrian-Ordovician) of the Amarillo-Wichita uplift, was eroded from the upthrust block and recycled northward as the Berlin fan-delta. Today, the Berlin recrystallized, recycled detrital dolomite fan-delta is a large 41 mi/sup 2/ overpressured gas reservoir with 242-362 bcf reserves at 15,000 ft. The Berlin field is genetically related to the late Atokan crestal unconformity of the Elk City structure, and is an example of the association of crestal unconformities and clastic stratigraphic traps. Such stratigraphic traps originated in marine environments proximal to active structures that have become subaerially exposed. With adequate sealsmore » and favorable structural position, detrital deposits recycled from local uplifts can form significant stratigraphic traps. Such stratigraphic traps can occur in compressional, extensional, and diapiric regions.« less