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Steven L. Dorobek1, Michael F. Hoffmann2, Steven L. Bachtel3, Steven K. Reid4
(1) Texas A&M University, College Station, TX
(2) Burlington Resources Inc, Houston, TX
(3) Exxon Production Research Company, Houston, TX
(4) Morehead State University, Morehead, KY

Abstract: Syndepositional Intrastratal Failure Along Outer Parts of the Lake Valley Carbonate Ramp (Mississippian, South-central New Mexico) and Its Effects on Stratigraphic Development

A variety of intrastratal deformation features formed during deposition of outer-ramp carbonate facies that comprise much of the Mississippian Lake Valley Formation, south-central New Mexico. These deformation features include buckled and slumped beds, toe thrusts, listric to subhorizontal faults, and near vertical faults (with unknown terminations at depth). Locally, slow downslope-directed creep also appears to have created multiple, complexly intersecting, subhorizontal shear surfaces within argillaceous carbonate strata. Stratal onlap patterns within post-deformation beds and direct mapping of faults indicate that many features are associated with shallow detachment surfaces (i.e., <20 m sedimentary overburden at time of deformation). The apparently minor stratigraphic overburden and the regional, low-angle character of the Lake Valley ramp suggest that seismic events may have triggered much of the shallow deformation. Larger scale, near vertical faults, however, may be basement-involved.

Slump features created bathymetric highs (1-20 m high, 10-50 m wide) that influenced post-deformation stratal patterns and depositional processes. Sediment gravity-flows (grain flows, debris flows, high-density turbidity currents) onlapped, bypassed and thinned over seafloor highs created by slumping. Steeply dipping faults locally formed steep-sided channels that funneled sediment gravity-flows downdip. Multiple erosive gravity-flows also progressively flattened or buried the profiles of some slump features. Correspondingly, seafloor highs created by intrastratal deformation had progressively diminishing effects on the movement of sediment gravity-flows.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana