MIXED CARBONATE-SILICICLASTIC SEDIMENTATION AND ACCOMMODATION TRENDS IN THE BUG SCUFFLE LIMESTONE, SACRAMENTO MOUNTAINS, NM
This study concerns the accommodation history of the Desmoinesian Bug Scuffle Mbr. of the Gobbler Fm. (Morrowan?-Desmoinesian). The Bug Scuffle platform, located along the eastern Orogrande basin, is dissected by an E-W trending siliciclastic thoroughfare at Alamo Canyon. Published data indicate regional transitions from marine carbonates along the west face of the Sacramento Mtns to marginal marine siliciclastics to the east, and basinal facies to the south and west.
New measured sections from the Dog Canyon area were compared with published data to interpret sequence architecture of the Bug Scuffle carbonate platform. Fissile mudstone, crinoidal turbidites and cohesive slide blocks abruptly overlie shallow marine siliciclastics at the base of sections, indicating deepening and suppression of siliciclastic input. Skeletal wackestone and packstone cycles stack into transgressive systems tracts, while highstand cycles grade into crinoid grainstones. Blackened crusts and mottled cycle tops indicate subaerial exposure of subtidal facies and are common tops in highstand cycles. Two composite sequences are interpreted from stacking trends and facies proportions. Above the upper sequence boundary, shingled mounds and thin-bedded, nautiloid wackestone suggest increased accommodation during terminal Bug Scuffle deposition, in contrast with previous studies that suggest progradation throughout. This work represents preliminary findings in a larger effort to compare tectonic and eustatic signals in Pennsylvanian carbonates from the Sacramento Mountains with coeval deposits in other Ancestral Rocky Mountains basins.