Determining the Depositional Environment of the Lower Eagle Ford Group in Lozier Canyon, Antonio Creek, and Osman Canyon: An Out Crop Study of Bedding Features a Study of Bedding Features at Outcrop Scale or in the Outcrop

Abstract

The Eagle Ford Formation is currently the most economically significant unconventional resource play in the state of Texas. There has been much debate as to the environment of deposition for the lowermost Facies A of the Eagle Ford in outcrop exposures in Lozier Canyon, Texas. Two conflicting hypotheses were proposed: 1) Sedimentary structures in Facies A are hummocky cross-stratification (HCS) and swaley cross-stratification (SCS), which indicates a shelfal depositional environment above the storm wave base (SWB). 2) Sedimentary structures in Facies A are a mixture of diagenetically separated contourites, turbidites, and pinch-and-swell beds, which indicate a distal-slope depositional environment below SWB. This research used field work, three-dimensional analysis of sedimentary structures, measurements of ripple height, and laboratory analysis to interpret the environment of deposition. The results of these observations and data suggest that the sedimentary structures in Facies A record a depositional environment above SWB.

Observation of cross-bedded structures in three-dimensions reveals (i) isotropic truncation of laminae; (ii) symmetric rounded ripples; (iii) large variations in laminae geometry, truncation, and dip inclination, attributed to fluctuations in storm intensity, frequency, and duration; and (iv) and bidirectional downlap and reactivation surfaces associated with oscillatory flow above the SWB.

This study interprets cross-bedded sedimentary structures in Facies A as swaley cross-stratification (SCS) and hummocky cross-stratification (HCS) associated with storm events, and thus places Facies A in a depositional environment above storm wave-base (SWB).