Print this pageABSTRACT: Three Lobes of Higher Organic Content May Be Related to Three Mississippian Antler Basin Delta Systems, Utah and Nevada
Three lobes of higher organic content on an average total organic content (TOC) map of well cuttings and samples from measured sections in the Mississippian Antler basin indicate three delta systems protruding into Utah from the Antler highlands in Nevada. The largest lobe of high organic richness is associated with a depositional trough that extends into the Oquirrh basin of central Utah. Subaerial indicators such as mud cracks and roots penetrating bedding plains in several of the siliciclastic tongues of the lobes suggest that their higher organic content concentrations may be due to lacustrine and deltaic deposition. Lower organic values to the east and between the lobes may be due to carbonate dilution of the Antler carbonate basin to the east.
Organic richness and shale thickness increase westward until truncated by the Mesozoic central Nevada thrust belt. Mississippian rocks in allochthonous thrust sheets such as the Diamond Range and the Eleana Range are organically lean while rocks beneath and just in front of the thrust sheets are organically rich (up to 6% average TOC). The lower organic content of leaner, coarser, allochthonous rocks may be due to siliciclastic dilution from the Antler highlands to the west.
AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990