Sedimentologic and stratigraphic analysis of synrift siliciclastic fluvial and lacustrine strata in the Lower Cretaceous upper Yucca Formation, Indio Mountains, West Ttexas
Outcrops of the upper Yucca Formation in the Indio Mountains near Van Horn, Texas provide temporal, tectonic, and climatic similarities to Lower Cretaceous, synrift, greenhouse pre-salt lacustrine strata along in the subsurface of the South Atlantic margin. These “pre-salt” strata hold prolific petroleum reservoirs but despite extensive seismic studies performed for regional scale hydrocarbon exploration in these lacustrine reservoirs, sedimentologic and stratigraphic analyses have rarely been published. The Upper Yucca Formation in the Indio Mountains contain lacustrine reservoir analogs that intertongue with fluvial and deltaic sandstones. Near Squaw Canyon, fluvial-deltaic sandstones are reduced in abundance to lacustrine carbonates by nearly 70% over less than 1 km of exposure. This change is either accommodated by delta progradation into the Cretaceous lake or through climatic and tectonic events resulting in channel erosion and redeposition of mudstone and lacustrine limestone on the lake floor. A detailed facies analysis and stratigraphic architecture of the fluvial/lacustrine depositional system of the upper Yucca Formation was performed to distinguish how the fluvial channels sands interact with the lacustrine muds; three stratigraphic transitions are documented revealing 1) conglomeratic cross-bedded fluvial channel sands downcut into lacustrine muds marked by an erosional unconformity 2) burrowed and laminated lacustrine shoreface muds onlap meandering channel sands 3) fluvial channel sands bearing lacustrine rip-up clasts intertongue with draping delta-front and lacustrine muds indicating a lacustrine delta. Overall the fluvial channels characterize fluvial progradation across a desiccated lake floor with fluctuating lake levels that are characterized by erosional unconformities, erosional lacustrine shoreline, and interfingering fluvial-lacustrine deltaic sands and muds.
Fox, Matthew Robert, "Sedimentologic and stratigraphic analysis of synrift siliciclastic fluvial and lacustrine strata in the Lower Cretaceous upper Yucca Formation, Indio Mountains, West Ttexas" (2016). ETD Collection for University of Texas, El Paso. AAI10151197.