Abstract

Contemporaneous Ozona Sandstone slope and basin systems display a range of depositional styles and facies, which can be understood as responses to tectonic setting and sediment supply. In the Early Permian Val Verde Basin, active and passive continental margins faced each other across a basin floor that was less than 40 km wide. The northward-converging Ouachita orogenic belt formed the southern basin margin, whereas a pre-collision cratonic margin persisted in the north. Sandstones derived from both margins are intimately interbedded along the narrow basin floor. The Ozona Sandstone is the uppermost of four deep-water clastic intervals that filled the Val Verde Basin during the period of plate convergence (Late Pennsylvanian to Early Permian). Although Ozona stratigraphy is complex, dense well control allowed high-resolution mapping of genetic stratigraphic units a few tens of meters thick. The Ozona Sandstone interval is 300 m thick and displays three distinct depositional styles: 1) A line source slope-apron composed of turbidite channel-lobe complexes that onlaps the northern passive margin, 2) Poorly channelized, turbidite sheet-lobes that offlap the southern active margin, and 3) An axial-channel system on the basin floor that parallels the opposing margins.

Ouachita convergence resulted in northward migration of three important structural zones: thrust-related uplift, foredeep subsidence, and forebulge uplift. Thrust-related uplift in the south supplied large volumes of sediment for offlapping sand-rich turbidite lobes. The migrating foredeep progressively depressed the northern passive margin, creating space for sustained onlap. Forebulge uplift on the northern craton created a sediment source for the onlapping strata. The axial channel system is a product of asymmetric convergence and basin-floor tilting. Contemporaneous Ozona slope and basin systems experienced the same eustatic sea-level history but exhibit a variety of depositional styles and facies.