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Subject Keyword PETROLEUM ♦ FEDERAL REGION IX ♦ PETROLEUM DEPOSITS ♦ FEDERAL REGION VIII ♦ GEOLOGIC TRAPS ♦ RESERVOIR ROCK ♦ CRETACEOUS PERIOD ♦ DEPOSITION ♦ DIAGENESIS ♦ SANDSTONES ♦ GEOLOGIC AGES ♦ GEOLOGIC DEPOSITS ♦ MESOZOIC ERA ♦ MINERAL RESOURCES ♦ NORTH AMERICA ♦ RESOURCES ♦ ROCKS ♦ SEDIMENTARY ROCKS ♦ USA 020200* -- Petroleum-- Reserves, Geology, & Exploration
Abstract Shelf-bar sandstones of the Cretaceous Western interior seaway of North America form excellent stratigraphic traps for hydrocarbons. Modern shelf sands occur in a variety of settings and are affected by such processes as storms and tidal, longshore, and shelf currents. Case studies of several Cretaceous and late Paleozoic sandstones document a spectrum of ancient shelf-bar types analogous with modern shelf systems. Several shelf bars deposited in nearshore environments (8-10 mi offshore) were associated with deltaic axes. Sands were reworked from these axes by currents moving along the shoreline that were diverted by a headland. Such shelf-plume sandstones were subsequently reworked by storms and other shelf processes. The relative effects of storm and shelf or coastal currents greatly influenced the geometry and characteristics of the nearshore shelf bars, of which several variations can be documented. Tidal currents are an important factor in forming and modifying modern shelf bars in the North sea. Examination of primary structures and directional features suggests tidal currents were relatively unimportant in nearshore shelf bars of the Cretaceous Interior seaway. Examples of Pennsylvanian shelf-bar sandstones from the Sacramento Mountains of New Mexico have features characteristic of both storm and tidal processes. Detailed examinations of primary sedimentary structures and facies relationships are useful in recognizing the various shelf-bar types and predicting the occurrence and distribution of similar potential reservoirs.
Educational Use Research
Learning Resource Type Article
Publisher Date 1987-11-01
Publisher Place United States
Journal AAPG Bull.
Volume Number 71
Issue Number 11
Organization RPI International, Inc., Boulder, CO (USA)


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