Cretaceous sedimentation and tectonism in the southeastern Kaiparowits region, Utah

Abstract

Upper Cretaceous strata in the southeastern Kaiparowits region of southcentral Utah consist of approximately 3,500 feet of interfingering sandstone, mudstone, shale, and coal in the Dakota Formation (oldest), Tropic Shale, Straight Cliffs Formation, and Wahweap Formation (youngest). The formations consist of several depositional facies that can be recognized by characteristic lithologies, bedding structures, and fossils; these are the alluvial plain, deltaic plain, lagoonal-paludal, barrier sandstone, and offshore marine facies. The distribution of facies clearly defines the paleogeography of the region during several cycles of marine transgression and regression. The nonmarine beds were deposited on a broad alluvial coastal plain that was bordered on the west and southwest by highlands and on the east and northeast by the Western Interior seaway. The marine beds were deposited whenever the seaway advanced into or across the region. The Dakota Formatioa and the lower part of the Tropic Shale were deposited in nonmarine and marine environments while the shoreline advanced generally westward across the region. The middle and upper parts of the Tropic Shale and the Tibbat Canyon, and Smoky Hollow Members of the Straight Cliffs Formation were deposited in marine and nonmarine environments when the seaway had reached its greatest areal extent and began a gradual northeastward withdrawal. An unconformity at the top of the Smoky Hollow represents a period cf erosion and possibly nondeposition before deposition of the John Henry Member of the Straight Cliffs. The John Henry Member grades from nonmarine in the southwest to predominantly marine in the northeast, and was deposited during cwo relatively minor cycles of transgression and regression. The Drip Tank Member at the top of the Straight Cliffs Formation is a widespread sandstone unit deposited mainly in fluvial environments. Some of the beds in the northeastern, part of the region were probably deposited in marine waters during the final incursion of the seaway into the Kaiparowits region. The overlying Wahweap Formation was deposited in nonmarine environments. Slight but continued tectonism during Late Cretaceous time is indicated by lateral changes of facies and thickness variations that coincide at least partly with present structures. These criteria indicate that Laramide tectonism consisted of two phases. An early phase that lasted from about late Albia: to late Campanian time included regional subsidence, basin downwarping, and movement on local folds and faults. A later phase that lasted from late Campanian to about late Paleocene time included regional uplift, monoclinal flexing, and probable new faulting, as well as continued basin dovmwarping and movement on local folds and probably on the older faults. The principal economic resource in the Kaiparowits region is bituminous or subbitumincus coal in the John Henry Member. Because basin downwarping and movement on local folds occurred during deposition, the thicker and more continuous coal beds are in the an...

High precision U–Pb zircon geochronology for Cenomanian Dakota Formation floras in Utah

“…The excursion in d 13 C is located just below the formational contact of the Middle Dakota with the overlying marine Tropic Shale, a contact that is readily identifiable throughout southern Utah and represents a flooding surface associated with a major sealevel transgression that reached maximum high stand in the early Turonian (Haq et al, 1987;Roberts and Kirschbaum, 1995). This transgression provided the initial framework for correlating the Dakota Formation and Tropic Shale on the Colorado Plateau with the Greenhorn Cycle (Averitt, 1962;Peterson, 1969;Peterson and Kirk, 1977). The correlation from western Utah to the CenomanianeTuronian GSSP in Pueblo, Colorado was improved using bentonite (Kowallis et al, 1989) and limestone marker beds (Elder et al, 1994), coupled with associated ammonite and bivalve index fossils (Cobban and Scott, 1972;Kauffman, 1977;Cobban, 1984;Kauffman and Caldwell, 1993).…”

“…3) are located along the western margin of the Kaiparowits Plateau (Kirschbaum and McCabe, 1992;Uli cný, 1999), which exposes a thick section of Upper Cretaceous (Cenomanian to Campanian) sedimentary rocks unconformably deposited on the tilted Jurassic Entrada or Morrison Formations (Eaton et al, 1999;Uli cný, 1999). Peterson (1969) divided the Dakota Formation on the Kaiparowits Plateau into three informal members, separated by disconformities. The Lower Member erodes into the underlying Jurassic deposits and is characterized by thick sequences of conglomerate (typically one meter thick, but exceeding 10 m locally) and sandstone, deposited in braided river channels flowing from the Sevier Orogeny (Gustason, 1989;Kirschbaum and McCabe, 1992).…”

Facies control on sandstone composition (and influence of statistical methods on interpretations) in the John Henry Member, Straight Cliffs Formation, Southern Utah, USA

“…2; Peterson, 1969a;Shanley and McCabe, 1995). Shoreface successions of the John Henry Member form stacked sandstone units along Fifty Mile Mountain.…”

High-Resolution Estuarine Sea Level Cycles From the Late Cretaceous: Amplitude Constraints Using Agglutinated Foraminifera

“…Lignite (L): Impure coals of sub-bituminous grade occupy 3 to 5 beds (Peterson, 1969;Tibert and others, 2003b). The coal seams range in thickness from 10 to 30 centimeters.…”