Many large new discoveries of oil and gas during the past few years have been made in Cretaceous strata. These fields occur in many parts of the world and have very similar reservoir and entrapment characteristics.

The worldwide orogeny near the end of the Early Cretaceous produced sharp uplifts, folding, epeirogenic warps, and a general marine regression to create a complicated paleogeography. Subsidence along shelf edges allowed accelerated reef growth, evaporites were deposited in the marginal supratidal sabkhas, and sandstones derived from granitic terrane or reworked from newly uplifted older strata were widely distributed. These features were subjected to erosion in many areas and then rapidly overlapped by the widespread Albian to early Late Cretaceous marine transgression which created 4 types of traps in which Cretaceous oil and gas accumulated: (1) Lower Cretaceous sandstone overlain by upper Lower Cretaceous evaporites (Cabinda B field, offshore west Africa), (2) upper Lower Cretaceou shelf carbonates (offshore Iran and southern Persian Gulf), (3) upper Lower Cretaceous or lower Upper Cretaceous deltaic and littoral sandstones overlain by deeper water marine shale (Bell Creek, Montana; Oriente Plain, Ecuador-Colombia; Western Desert, Egypt; Barrow Island, Australia; Tyumen Province, western Siberia), and (4) folded and eroded oil-producing Triassic, Jurassic, and Lower Cretaceous beds unconformably overlain by Albian to Upper Cretaceous strata (northern Alaska).

The late Early Cretaceous tectonic history indicates that numerous large petroleum accumulations in Lower Cretaceous to Cenomanian strata await discovery throughout the world.

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