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Stratigraphic Architecture of the Desmoinesian Bug Scuffle Limestone, Sacramento Mountains, New Mexico

Abstract

Desmoinesian-early Missourian mixed carbonate-siliciclastic strata from the Sacramento Mountains house a depositioanal record of sea level fluctuations during the Late Paleozoic Ice Age and influx of coarse siliciclastics during Ancestral Rocky Mountains (ARM) shortening. The Bug Scuffle Member of the Gobbler Formation is the limestone facies of the carbonate-siliciclastic depositional system. A new sequence stratigraphic framework for the Bug Scuffle Limestone provides an analogue for Strawn and Canyon reservoirs in the Permian Basin.

A 35km strike-oblique transect and 2-4km dip-oriented correlations were compiled from 9 new measured sections and 1 new core log that total more than 2000m of vertical section. Bug Scuffle exposures vary from ~170m-thick in distal sections to ~300m central localities, spanning ~5my of deposition. Photopan tracings and drone photogrammetry were used to assist correlation between measured sections and to evaluate detailed stratigraphic architecture.

Carbonate deposition took place on a ~5km wide ramp that steepened to the south and west from the Pedernal Uplift, and was bisected by a siliciclastic thoroughfare. Siliciclastic facies form coarsening-upward cycles of fluvial-deltaic sandstones and siltstones-shales. Distal carbonate facies form slope deposits with muddy channels and crinoid grain flow deposits. Outer ramp facies are mud-dominated limestones with delicate fenestrate bryozoan assemblages. Middle ramp facies are composed of skeletal mud- and grain-dominated packstones with disarticulated brachiopods, ramose bryozoan fragments, crinoids and fusulinids. Shallow carbonate facies crinoid grainstones deposited in amalgamated subtidal shoal complexes.

Cycles stack into two composite sequences. The younger composite sequence is overlain by shingled mixed skeletal bars with ~6m of relief that pass upward into thin-bedded, cephalopod-bearing wackestone. This indicates transgression during terminal Bug Scuffle deposition in the early Missourian.

Preliminary fusulinid data suggest that the lower composite sequence is early Desmoinesian (primitive Beedeina and Wedekindellina), and the upper composite sequence is late Desmoinesian (advanced Beedeina), which correlate to the Midcontinent Cherokee and Marmation Groups, respectively. Interbasinal correlation to the more stable Midcontinent region will help to isolate tectonic variables that impact siliciclastic sediment routing onto synorogenic carbonate shelves across ARM basins.