Paper No. 12
Presentation Time: 9:00 AM-6:30 PM


SIMPSON, Edward L.1, KOCH, Robert1, HENESS, Elizabeth A.2, WIZEVICH, Michael C.3, TINDALL, Sarah E.4, HILBERT-WOLF, Hannah L.5, GOLDER, Keenan B.6 and STEULLET, Alex7, (1)Physical Sciences, Kutztown University, Kutztown, PA 19530, (2)Department of Physical Science, Kutztown University, 425 Boehm, P.O. Box 730, Kutztown, PA 19530, (3)Department of Physics and Earth Sciences, Central Connecticut State University, 1615 Stanley St, New Britain, CT 06050, (4)Department of Physical Sciences, Kutztown University, P.O. Box 730, Kutztown, PA 19530, (5)School of Earth and Environmental Sciences, James Cook University, Townsville, 4810, Australia, (6)Deaprtment of Earth and Environmental Sciences, Wesleyan University, Middletown, CT 06459, (7)ConocoPhillips School of Geology and Geophysics, Univeristy of Oklahoma, Norman, OK 73019,

During development of the East Kaibab monocline, listric normal faulting influenced sedimentation in the Late Cretaceous Wahweap Formation recording the initial phases of the Laramide Orogeny. Located along the East Kaibab monocline, are deposits of two sag ponds that document seismogenic fault movement and disruption of local drainage systems. Ancient sag pond deposits are likely under-identified in the rock record; this study demonstrates their significance and potential for unraveling fault histories.

At the northernmost syndepositional normal fault, the deposits of a small sag pond are located at the boundary between the upper and capping sandstone members of the Wahweap Formation. Pond infill consists of laminated, gray mudstones and siltstones intruded by sandstone dikes and sills. Adjacent to the southernmost syndepositional normal fault, a larger and thicker sag pond deposit is located near the base of the upper member. This southern older sag pond preserves gray, seemingly structureless siltstones and mudstones. The simple fine-grained fill is cut by brittle faulting along the fault-side margin of the southern pond in contrast with the pervasive clastic intrusions in the younger sag pond. The geographic positions and thicknesses of the deposits suggest that the older more southern sag pond has a protracted history of extension, in comparison with the more northern sag pond locality.

The younger, northern sag pond deposit preserves small macerated flora, but no discernable invertebrate fauna. Either the pond was too small, was not active for long, or sedimentation rates were too high (or a combination of factors) to sustain a well-developed ecosystem. The older, larger sag pond fill comprises a series of fossil horizons consisting of juvenile gastropods, Lioplacodes, Planorbis, and Vivaparis and unionid bivalves, Unio, along with unidentifiable macerated plant fragments. The immature fossil assemblages suggest that the older, southern sag pond experienced frequent significant sedimentation events that prevented the invertebrate fauna from reaching maturity punctuated by periods of low sedimentation rates. It is likely that fault movements triggered these rapid catastrophic sedimentation events, but significant precipitation events cannot be ruled out.