SIMMONS, MICHAEL, ARCO Oil and Gas Company, Bakersfield, CA

ABSTRACT: Regional Distribution Patterns of Midway-Sunset Sands Related to Highstand/Lowstand Sequences of the Antelope Shale

The Antelope Shale Member of the Monterey Formation can be subdivided into three informal units: two sand-rich lowstand sequences separated by a shale dominated highstand.

The intervening highstand or flooding event is dominated by the upper Obispo Shale, which contains very few sands. This unit may represent cessation of tectonic activity related to temporary stalling of the northward migrating Salinian block. During the highstand, sands sourced from the Salinian block were stranded on the shelf west of the depositional site of the Republic sand, the youngest of the previous lowstand channel sands.

The culminating lowstand of the Antelope Shale documents a major tectonic episode, possibly renewed northward translation of the Salinian block, and is dominated by sand in the stratigraphic record. The youngest sand, the 1-6, overlies the Obispo Shale and Republic sand and may represent remobilized coarse clastics which had been stranded on the shelf during the previous highstand. The other major sands within this interval document the filling of an intraslope basin from south to north and appear as thick, overlapping "shingles." The oldest of these major "shingles" is the lower Monarch 10-10, followed in ascending order by the Monarch 10-10, Monarch, Spellacy, and younger unnamed sands. Sand deposition ceased with the onset of another highstand marking the end of Antelope deposition

AAPG Search and Discovery Article #90992©1993 AAPG Pacific Section Meeting, Long Beach, California, May 5-7, 1993.