Preliminary Analysis of Depositional Environments of Tar Sand Host Rocks, Uinta Basin, Eastern Utah: ABSTRACT

Abstract

Four major tar sand bodies in the Uinta basin were examined in terms of their depositional environments: (1) the Duchesne River and Mesaverde Formations at the Asphalt Ridge deposit near Vernal, Utah; (2) the Wasatch and Green River Formations at the Sunnyside deposit near Sunnyside, Utah; (3) the Green River Formation of the Hill Creek deposit in the southern Uinta basin; and (4) the Green River Formation in the P.R. Spring deposit of the southeastern Book Cliffs. The Mesaverde Formation at Vernal is interpreted as a fluvial deposit, based on the discontinuous geometry, and the presence of large-scale trough cross-beds which grade vertically into smaller trough cross-beds and tabular foreset beds. The lower Duchesne River Formation was deposited in distributary channels, based on the discontinuous geometry, large-scale trough cross-beds, contorted bedding, and clay-chip zones. This facies is overlain by a meandering flood-plain sequence of sandstones and red shales. The Wasatch Formation in the Sunnyside area is comprised of stream-mouth bars, point bars, and both active and partial abandonment channel fill. The Green River Formation at Sunnyside was deposited in distributary channels as evidenced by a scoured contact, calcareous clay clasts, large-scale convoluted bedding, and the geometry. This facies grades to the southeast into more laterally continuous sands in the P.R. Springs area. These sands reflect delta front deposition. End_of_Article - Last_Page 645------------