Study of 29 stratigraphic sections of the Upper Cretaceous Cliff House Sandstone, Lewis Shale, Pictured Cliffs Sandstone, Fruitland Formation, and Kirtland Shale in the Bisti Badlands of northwestern New Mexico suggest deposition in deltaic environments. Cliff House Sandstone littoral, Lewis Shale prodelta and delta-front, Pictured Cliffs strand-plain, levee, and distributary-channel, Fruitland Formation paludal, estuarine, and delta-plain, and Kirtland Shale flood-plain facies document the transgression and regression of the last epeiric seaway for the San Juan basin.

Littoral and strand-plain paralic facies, respectively, delineate transgressive and regressive sequences, whereas prodelta and delta-front facies reflect deposition in offshore open-marine waters. Late Campanian fossils represented by marine mollusks, sharks and dinoflagellates, pelagic foraminiferids, benthic ostracods, littoral and shallow-neritic Ophiomorpha burrows, and terrestrial palynomorphs illustrate that marine conditions prevailed but were contaminated by terrestrial biotas. Deposition of delta-front sandstones 1 km or more from shore is substantiated by the hypopycnal inflow formula.

Terrestrial environments, represented by levee, distributary-channel, paludal, delta-plain, and flood-plain facies, exhibit the deposits of vertically accreted shale, laterally accreted channel sandstones, and coal. Overbanking of distributary channels formed natural levees on the periphery of interdistributary marshes, thereby preserving a coal to shale to sandstone vertical sequence. Local transgression due to channel abandonment and delta-lobe subsidence deposited estuarine shale and upward-coarsening, crevasse-splay sandstones. Delta-plain to flood-plain facies shows the transition from thick commercial coals and shale, to shale and channel sandstones, to shale which contain local coal, bentonite, and channel sandstones. The transition represents, respectively, poorly drained swamps, well-drained delta-top tracts, and riverine with lacustrine regions. Aquatic bivalves and gastropods plus fish, turtle, crocodile, and dinosaur bones occur as lag deposits to channel sandstones. Locally, articulated dinosaur, turtle, and crocodile bones are present in the vertically accreted shale.

Nine hundred million metric tons of coal from four coal seams of the lower Fruitland Formation represent a major energy resource for New Mexico. Western Coal Co., Albuquerque, intends to strip mine 80 million metric tons of coal found within the study area.

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