Strike Variability of Carbonate Platform Margin Stratal Architecture and Cycle Stacking Patterns: Outcrop and Seismic Examples from Lower Permian Depositional Sequences of the Permian Basin, U.S.A.: ABSTRACT

Strike variability in stratal architecture, cycle stacking patterns and facies differentiation within sequences exemplifies the potential for differential stratigraphic response of platforms to eustasy. Variability exists within base-level cycles of several scales within a compound stratigraphic hierarchy, though the causes may vary among different scales. Cross-sections from outcrops in the Sierra Diablo document the framework and stacking pattern of 3rd-order sequences (HFS), including: two progradational middle Wolfcampian HFS (mW1-2), one backstepped upper Wolfcampian HFS (uW1), one progradational lower Leonardin HFS (L1), aggradational middle (L2) and upper Leonardian HFS (L3), three progradatic upper Leonardian HFS (L4-6), and two backstepped, aggradational upper Leonardian HFS (L7-8). Seismic lines from the northern Delaware and Midland Basins and San Simon Channel area document the regional consistency of 3rd-order sequence stacking patterns (a response to eustasy), but show variability related to local subsidence, antecedent topography (owing to deeper structures and platform margin erosion), windward vs. leeward facing, and siliciclastic sediment supply. Sequences L2 and L3 appear to exhibit the greatest variability in stacking pattern. Strike variability in 4th/5th-order cycle stacking patterns within 3rd-order sequences as studied in outcrop is greatest in sequences L2 and L3, in which headland-bight margin trends are developed on a lateral scalemore » of 1-2 miles. Aggrational to backstepping reef-margin facies with steep ([le]35[degrees]) foreslopes developed along headlands. Mudstones abut these margin facies abruptly along headlands and may contain megabreccias at the toe-of-slope. More gently sloping (10-15[degrees]) [open quotes]ramp[close quotes] margin strata composed of fusulinid packstones characterize bights.« less