Discontinuity surfaces, clinoforms, and facies architecture in a wave-dominated, shoreface-shelf parasequence

Detailed outcrop analysis of a wave-dominated, shoreface-shelf parasequence exposed in the Book Cliffs, Utah reveals minor stratigraphic discontinuiti es, which define clinoforms. Two types of discontinuity are recognized, eac h with a distinctive lithologic character and geometry. Nondepositional dis continuities are marked by an abrupt decrease in the thickness and amalgama tion of storm-generated event beds, and are interpreted to record hiatuses in sedimentation. These discontinuities define clinoforms with a concave-up ward geometry that dip gently (0.02-0.58 degrees) over distances of 800-600 0 m down depositional dip. Erosional discontinuities are marked by an abrup t increase in event-bed amalgamation, grain size, and sand content, and are interpreted as enhanced storm-wave scours. These discontinuities define mo re steeply dipping (0.22-0.95 degrees), concave-upward clinoforms that exte nd over 100-1600 m down depositional dip and 500-1500 m along depositional strike. The distribution and amalgamation of minor stratigraphic discontinu ities defines linear zones of distinctive facies architecture that are orie nted parallel to the paleoshoreline trend. Using the simple assumption that the shoreface-shelf equilibrium profile remained approximately constant fo r each type of discontinuity throughout shoreface migration (the "Bruun rul e"), intra-parasequence facies architecture can be speculatively interprete d in terms of shoreline trajectory, which reflects the balance between sedi ment supply and accommodation. The resulting interpretations support the no tion that shoreline trajectory exerts a strong control on intra-parasequenc e facies architecture and preservation of the shoreface-shelf profile.