| Popis: |
Late Mississippian and early Pennsylvanian flysch sediments of the Ouachita foldbelt of southeastern Oklahoma include turbidites with abundant sole marks and other paleocurrent indicators. Directional readings on sandstones of the Jackfork, Johns Valley, and lower Atoka sequence show that sediment transport was westward, down the axis of the geosyncline and that current directions remained essentially constant during the deposition of 13,000 feet of sediment. A turbidity flow mechanism dominated during sand transport and fallout, although existing oceanic currents may have aided sand distribution. In the Arkoma basin, which adjoins the Ouachita geosyncline on the north, sediment transport was southward across the basin as evidenced by paleocurrent readings on ripple marks and cross bedding. At the south margin of the basin, in a zone 6 to 8 miles wide, paleocurrents were deflected abruptly westward to parallel those of the geosyncline. Facies relations, sedimentary petrology, and paleocurrent studies all indicate that the Ouachita geosyncline derived its sediments from marginal sources. In Oklahoma a substantial amount of the Stanley was derived from the south margin of the geosyncline, as shown by paleocurrent and petrographic studies. Petrographic studies indicate that a significant amount of the Jackfork Sandstone of Arkansas also was derived from the south. Some of the sand for the turbidites was derived from the craton to the north, transported southward across the Eastern Interior basin, and debouched into the Ouachita geosyncline in eastern Arkansas or western Mississippi. Turbidity flows transported the sand down the axis of the trough to the west where it intermingled with sediments from southern sources. > The sole marks of each major thrust plate are parallel to those of adjacent thrust plates, indicating that there was very little rotation of the thrust plates as they moved northward. It seems likely that the Arkoma basin-Ouachita geosyncline transition facies now lies buried beneath the outer edge of the Choctaw thrust plate. |
