Dudley D. Rice, Donald L. Gautier, 1983. "Coastal Sandstones", Patterns of Sedimentation, Diagenesis, and Hydrocarbon Accumulation in Cretaceous Rocks of the Rocky Mountains, Dudley D. Rice, Donald L. Gautier
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Coastal sandstones in the Western Interior form prominent cliffs and hogbacks in outcrop and thick, sheetlike sandstones in the subsurface that are often conventional reservoirs for oil and gas. Hydrocarbon accumulations in these reservoirs are generally associated with structure because of their widespread nature. Coastal sandstones are deposited in two main settings: deltaic and strand plain. Most of the coastal sandstones of Cretaceous age in the Western Interior were deposited in an interdeltaic strand plain environment. The sand that composes these deposits was derived from wave-dominated deltaic systems that were areally small and had few distributaries. The distinction between strand plain and deltaic deposits is made on the presence of distributary channels in deltaic deposits that erode through parts of shoreface sequences and (or) distributary mouth bar deposits. Deltaic deposits generally have only been recognized in outcrop.
Most of these Cretaceous coastal sandstones were deposited along a prograding shoreline and contain characteristic vertical sequences of lithologies and sedimentary structures that demonstrate shoaling and increasing energy upward. The sequences grade upward from marine shale to sandstone capped by a root zone indicating subaerial exposure; most of the sand accumulated in the subtidal shoreface zone. These coarsening-upward sequences have been recognized in outcrop and core and have been interpreted from mechanical logs. The prograding sequences are similar to modern examples, with two exceptions: (1) sandstones representing deposition in upper shoreface zone (trough and tabular cross-stratified) are thicker in Cretaceous examples, and (2) coarsest grain size occurs in upper shoreface facies in Cretaceous
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Patterns of Sedimentation, Diagenesis, and Hydrocarbon Accumulation in Cretaceous Rocks of the Rocky Mountains
In the Rocky Mountains from western Canada to Mexico, Cretaceous rocks are major sources and reservoirs for oil and natural gas, accounting for about 40% of the cumulative production to date. Resources estimates indicate that large amounts of hydrocarbons remain to be discovered in these rocks. The purpose of this volume is to examine the relationship of reservoir quality, resource evaluation, and exploration strategy to depositional environment, thermal maturity, and diagenetic history of Cretaceous rocks in the Rocky Mountain area. Chapters deal with the general characteristics of the Cretaceous Western Interior Basin and seaway, the application of organic geochemistry to hydrocarbon occurrence and exploration, principle aspects of diagenesis that affect reservoir quality and source-rock potential, and the five main depositional facies which can be recognized from west to east across the basin.