Petrographic Constraints on Provenance and Sediment Dispersal Patterns, Atokan Sandstones of Arkoma Basin, Oklahoma and Arkansas: ABSTRACT

Abstract

Atokan strata of the Arkoma basin record the transition from sedimentation on a passive rifted margin to sedimentation in a foreland basin that developed as a result of convergent tectonic activity along the Ouachita orogenic belt. Sandstone compositions reveal how provenance and sediment dispersal patterns changed during Atokan sedimentation. The basal Atokan Spiro sandstone is composed almost exclusively of quartz grains derived from older platform strata north of the basin. In contrast, younger Atokan sandstones (Red Oak, etc) contain 70-90% quartz, 5-25% metamorphic lithic fragments (mostly slate), and 2-10% feldspar (more plagioclase than K-feldspar). Moreover, in many middle Atokan sandstones, the percentages of lithic fragments and feldspar have been significantly reduced during diagenesis by grain dissolution. In addition to the abundant framework grain species mentioned, Atokan sandstones locally contain small percentages of volcanic glass and ultramafic lithic fragments. Microprobe analyses of the ultramafic fragments indicate that they are composed of clinopyroxene crystals whose compositions suggest derivation from orogenic, tholeiitic basalt (e.g., an island arc). Integration of these compositional characteristics with facies and paleocurrent data suggests that the Spiro was deposited on a tectonically stable, south-facing shelf with predominantly southward sediment dispersal. The overlying Atokan sandstones were deposited in a tectonicallymore » active, rapidly evolving foreland basin. Most of the sediment deposited in this foreland basin was derived from the rising Ouachita orogenic belt to the east and south, and was dispersed longitudinally westward within the basin. The grain compositions suggest that the orogenic belt contained rocks of oceanic affinities, thereby supporting hypotheses of its accretionary origin.« less