Bathymetry and Paleoecology of Ouachita Geosyncline of Southeastern Oklahoma as Determined from Trace Fossils,

Abstract

ABSTRACT Trace fossil assemblages from the Mississippian-Pennsylvanian rocks of the Ouachita Mountains, southeast Oklahoma, define a basin-to-shoal bathymetric profile. They include a deep-basin assemblage (Nereites) in the central Ouachitas, transitional assemblage (Chondrites) in the lower Atoka Formation of the frontal Ouachitas, littoral and sublittoral to bathyal assemblage (Cruziana and Zoophycos) in the Wapanucka Limestone, and shallow-shelf assemblage (Cruziana) in the upper Atoka Formation of the Arkoma basin. The persistence of widespread, distinctive trace-fossil assemblages in the central Ouachitas, mainly feeding trails and burrows, through approximately 25,000 ft of Mississippian-Pennsylvanian rocks attests to the continuous hospitability of the flysch environment in a basin that remained deep despite isostatic and eustatic fluctuations. In the frontal Ouachitas, as the north slope of the geosyncline shifted north, the shallow-water environment was replaced by a flysch environment, and the trace-fossil assemblage of mainly dwelling and feeding burrows was replaced by a flysch facies with mainly feeding trails and feeding burrows. The southern edge of the Arkoma basin probably underwent subsidence and uplift, although only a littoral trace-fossil assemblage is exposed today.