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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 54 (1970)

Issue: 5. (May)

First Page: 789

Last Page: 806

Title: Provenance of Johns Valley Boulders in Late Paleozoic Ouachita Facies, Southeastern Oklahoma and Southwestern Arkansas

Author(s): Gerald L. Shideler (2)


Clasts within the Johns Valley Formation of the central Ouachita Mountain province range in age from Late Cambrian through Early Pennsylvanian; Ordovician specimens dominate. The clasts were derived from a single linear sourceland which was composed predominantly of foreland carbonate strata, but which also contained subordinate quantities of transitional and geosynclinal rock types. The sourceland was just north of the transitional zone along the flexure which separated the foreland and geosynclinal tectonic provinces.

Boulder dispersal patterns indicate that the sourceland was a rising, fault-bounded geanticlinal ridge which became an emergent archipelago. Prominent islands of the archipelago functioned as major boulder dispersal centers, and transport was primarily southward down steep and unstable marginal paleoslopes of the Ouachita trough. Clasts were derived by both subaerial erosion of the archipelago under warm and humid climatic conditions and by submarine erosion of a marginal fault scarp. The boulders were transported only short distances from their source by a combination of mass-movement media that were active along the unstable marginal paleoslopes.

The prolific introduction of boulders into the Ouachita geosyncline during deposition of the Johns Valley Formation resulted in the development of a distinct wild-flysch subfacies indigenous to the northern margin of the trough, in contrast to the turbidite flysch facies of the trough interior. After deposition of overlying Atoka sediments, the Ouachita facies was compressed and thrust-faulted northward over the denuded sourceland, the probable paleogeographic location of which is approximately coincident with the present Ouachita frontal belt.

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