H12: Hike near hiway 9, NW-erly limb of the Virgin anticline, and near Coral Cliffs housing area, in S4&5, T42S R14W
This is a short hike, climbing the cliffs above the road cut on hiway 9, to see a reverse fault cutting the limb of the anticline (hogback). The strike of the fault is roughly E-W, not only diagonally to the hogback, but different to all other major faults in the area. This is entirely in the Mesozoic, but immediately above the red beds there is a Pc (pliocene-pleistocene unconformity) gravel, with the shear strength of Pliocene. This is overlain by sand- almost level- and then again above that, more conglomerate. Pc contains large meter-size boulders of intrusiive from the Pine Valley Mtns, and the imbrication can be seen to indicate a S or SE-erly river flow (perpendicular to the Pine Valley Mtns.),indicating that there was no intervening river to block the flow. The present Virgin R. is east of this, so that there could been an ancestral Virgin, but we have already seen that there was no Virgin north of the Sky Mt. Golf course, in early Pleistocene
time- the land was essentially flat, away from the slopes of the Pine V. foothills. We will test the conclusion that Pliocene drainages were south and near the present Hurricane scarp.