Depositional Environment of the Yates Formation in Kermit Field, Winkler County, Texas: ABSTRACT

Abstract

The Yates Formation (Permian Guadalupian) is a series of alternating clastic and carbonate units deposited on a shallow marine shelf in repetitive cycles: (1) a mottled, anhydritic dolomite at the base, (2) an overlying oxidized wind-blown very fine-grained sand and silt, (3) a bioturbated, but otherwise massive, sandstone, and (4) an uppermost massive dolomite containing oolites or skeletal material. A typical cycle is 10-20 ft thick. Deposition of the Yates was controlled by fluctuations in sea level governed by glacial activity and local tectonics. During sea level low stands, carbonates were dolomitized and displaced by anhydrite. This was followed by deposition of wind-blown sediments creating planar horizontal laminae and exposure features (desiccation cracks, tepee structures, and adhesion ripples). During sea level high stands, dunes an the platform were deposited as sheet sands. Lastly, a carbonate layer was deposited before sea level dropped and another cycle began. Sands were transported to the Central Basin platform as eolian dunes from the Pedernal highlands of central New Mexico. Wind direction for the Permian is documented as south-southeast based on mapping of sand dunes in the southwestern US. Quartz size in the clastics ranges from 0.03-0.11 mm, averaging 0.07 mm. The sandstones are homogeneous,more » well sorted, and most quartz grains are frosted. Except for planar wind laminae, these units contain only indistinct primary sedimentary structures, constrained by small grain size and grain size uniformity within beds. The clastics are 52% monocrystalline quartz, 17% feldspar, 4% rock fragments, 5% other minerals, and 22% matrix (dolomite in the carbonates and authigenic clays in the clastics).« less