Abstract

The Bridal Veil Limestone Member of the Oquirrh Formation (Pennsylvanian, Bashkirian) represents the basal second-order supersequence of the composite Absaroka I Supersequence in the Oquirrh basin. At its type locality in the central Wasatch Range of Utah, the 410-m-thick Bridal Veil Limestone consists of 64 coarsening-upward carbonate cycles bundled into 20 depositional sequences that range from 3 to 60 m in thickness. Sequence boundaries are marked by thin (0.5–2.0 m), regionally persistent quartz-sandstone beds and/or microkarst horizons. The typical coarsening-upward cycle comprises a 1- to 15-m-thick couplet of mud-rich, slope-forming limestone overlain by grain-rich, ledge-forming limestone. Heterozoan carbonates, characterized by a skeletal grain association of light-independent invertebrates (brachiopods, crinoids, bryozoans, and siliceous sponges) are far more abundant than limestones containing photozoan components (foraminifera, algae, and ooids) even in grain-rich cycle caps. The lack of photozoan facies in the low-latitude Oquirrh basin appears to be related to turbidity of the water column overlying the Bridal Veil ramp.

Thin (0.5–2.0 m), regionally persistent sandstone beds reflect transport of siliciclastics from the incipient Weber shelf (located to the northeast) during episodes of sea-level drawdown (falling stage and lowstand systems tracts). Though volumetrically insignificant, these sandstone beds play a critical role in regional correlation of the Bridal Veil Limestone and in identification of sequence boundaries.

The majority of cycles delineated on Cascade Mountain and Mount Timpanogos can be traced into the Lake Mountains and Thorpe Hills located 30 and 50 km west of Cascade Mountain, respectively, indicating that sequences, sequence boundaries, and lowstand sandstone beds are regionally persistent. However, lack of conodonts and foraminifera in Bridal Veil Limestone samples collected to date limits correlation with the global sea-level curve and with basal Oquirrh carbonates outside of the study area. Nevertheless, sequence stratigraphic analysis of the Bridal Veil Limestone is significant because the Oquirrh basin is one of only a few basins in North America that preserves a record of Bashkirian (Morrowan) carbonate deposition.