Pennsylvanian Tidal Depositional Systems in the Anadarko Basin, Northeast Texas Panhandle and Northwest Oklahoma
Report of Investigations No. 280, “Pennsylvanian Tidal Depositional Systems in the Anadarko Basin, Northeast Texas Panhandle and Northwest Oklahoma” is an indispensable guide for the general public who are interested in ancient tidal deposits in some of the most prolific oil and gas reservoirs in the Texas Panhandle. It is also a valuable resource for oil and gas explorationists who seek to have a better understanding of depositional controls on reservoir sandstones of tidal origin in the Anadarko Basin.
A thick (>6,000-ft [>1,830-m]) succession of Desmoinesian to Virgilian (Pennsylvanian) strata in the northwest part of the Anadarko Basin contains a variety of tide-modified deposits. This succession, which encompasses the Marmaton Group (Upper Desmoinesian), Cleveland Formation (Missourian), and Douglas Group (Virgilian), records progradation of highstand tidemodified delta and littoral systems punctuated by lowstand incised-valley deposits. Tidal stratification in this succession includes asymmetrical, double-draped ripples; reactivation surfaces; flaser bedding; rhythmic, laminar stratification; upper flow regime planar stratification; and minor herringbone stratification. Tidal amplification and reworking of deltaic and littoral sediments was controlled by (1) basin configuration, consisting of a broad, shallow shelf merging northward with an extensive epicontinental seaway in the U.S. Midcontinent, and (2) the formation of embayments during periods of relative sea-level fall, notably in the Cleveland Formation, in which an east-west-trending, lowstand paleovalley contains a vertical succession of coarse-grained fluvial-channel, tidal-channel, sandy tidal flat, muddy tidal flat, and transgressive-estuarine facies.
Local paleogeography was an important factor in the preservation of tidal signatures in the Marmaton to Douglas succession, where the relative weakness of wave and fluvial processes in marginal areas in depocenters resulted in preservation of rhythmic bedding and bidirectional, doubledraped ripples. A macrotidal setting is inferred for parallel, narrow, and dipelongate, upward-coarsening sandstone bodies in highstand-shelf systems in the Marmaton Group. In contrast, ~10-ft (~3-m) intertidal deposits and absence of large-scale bed forms such as estuarine-floor tidal sand bars in the Cleveland Formation and Douglas Group suggest microtidal regimes. Gross-sandstone thickness maps of highstand and lowstand systems tracts within the Cleveland Formation and Marmaton Group document systematic changes in sandstone-body thickness, continuity, and regional extent through time. These variations in sandstone-body geometry are a function of a unique paleogeomorphologic setting within each systems tract. Abrupt changes in sandstone-body geometry between each systems tract control variations in reservoir continuity and permeability pathways that should be considered in future resource development.