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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 39 (1955)

Issue: 1. (January)

First Page: 1

Last Page: 30

Title: Pennsylvanian Conglomerates, Structure, and Orogenic History of Lake Classen Area, Arbuckle Mountains, Oklahoma

Author(s): Robert J. Dunham (2)


Detailed mapping of a structurally complex area on the north side of the western Arbuckle Mountains revealed evidence that mountain-making in this part of the mountains did not occur as a single movement in Late Pennsylvanian time, but merely culminated then. It began in Middle Pennsylvanian and ended in Permian or later time, five distinct pulsations being recorded in the area.

Outcrops of the Middle Pennsylvanian (Des Moines) Deese formation, the first to be discovered on the north side of the western part of the mountains, record the initial pulsation. This formation rests unconformably on the Mississippian Caney shale and contains a conglomerate composed of limestone boulders derived from beds at least 4,500 feet and probably 9,000 feet stratigraphically lower. During the second and culminating pulsation (probably Virgil), the Deese and older strata were steeply folded into generally parallel, overturned anticlines and synclines. Somewhat later the overturned folds were broken by many branching faults, and fold axes were displaced as much as a mile. All the faults probably are branches of the Timbered Hills-Washita Valley fault. Most are strike- or obliqu -slip faults. Strike slip can be demonstrated by horizontal separation of vertical strata, and the magnitude of the dip- and strike-slip components can be calculated by matching displaced and eroded folds. In the fourth pulsation (still Virgil), there was renewed slippage on old faults and perhaps creation of a few faults. This pulsation affected the Virgil Collings Ranch conglomerate, displacing it only a fraction of the amount shown by the beds below the conglomerate, but failed to affect the younger, Virgil Vanoss conglomerate. The final pulsation folded the Vanoss conglomerate to dip as much as 40°, rejuvenating the old faults in one locality.

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