Controls on deposition and resulting stratal architecture of coarse-grained alluvial and nearshore facies associations

Three tectono-stratigraphic sequences compose the mixed carbonate-siliciclastic succession of the Permo-Pennsylvanian Cutler Group in the Paradox Basin. These are related to large-scale, long-term depositional events resulted from tectonic evolution of the basin. The first two sequences are Pennsylvanian in age and were associated to high rates of tectonic subsidence in the areas adjacent to the Uncompahgre highlands. Preservation of alluvial and nearshore clastics occurred at the more proximal areas. Conversely, the third sequence, main focus of this work, was deposited during the Permian in association with low rates of subsidence in the Uncompahgre front and major siliciclastic input into the more distal segments of the basin. High-frequency depositional genetic sequences are nested within the tectono-stratigraphic sequence. Stacking patterns of high-frequency genetic sequences subdivide this tectono-stratigraphic sequence into a basinward-stepping unit and a landward-stepping unit.; Coarse-grained sediment was supplied to the basin from coalesced braid-dominated alluvial fans. A large braidplain carried clastics westward from the alluvial fans into an extensive coastal plain and littoral/shallow marine systems. Due to contrasting accommodation scenarios, alluvial facies architectures in the medial segment are distinct for the basinward-stepping and landward-stepping units. The facies succession of the basinward-stepping unit records deposition in a braidplain dominated by low-sinuosity, bed-load fluvial systems and unconfined sheetflood flows. In contrast, the landward-stepping contains deposits of a tide-influenced, high-sinuosity to anastomosing fluvial systems. Distally, during aggradational to progradational periods, eolian dune fields occupied the coastal plain areas, and the bounding shore-zone was wave-dominated. Conversely, the landward-stepping unit records increasing tidal influence within a broad estuarine embayment behind a narrow, but well-established coastal eolian dune field. Shelf carbonate ramps extended from the clastic shore-zone into the basin throughout the deposition of the large-scale tectono-stratigraphic sequence.; The Permian Cutler Group outcrops were used in the integration of geological and numerical procedures to assess reservoir architecture and distribution of reservoir properties for the Permian Upper Rotliegend Group in the North Sea Basin. The integrated approach involved (a) the facies analysis and depositional system interpretation of the reservoir units, (b) observations from analog outcrops, (c) sequence stratigraphic analyses and, (d) geostatistical interpolation procedures.