MOAPA PEAK AND TWO SOUTHERN NEVADA EXPLORITORIES: DAVIDSON PEAK (5530') AND FRENCHMAN MTN (4054') 20-23 April 85

Southern Nevada is one of the great happy hunting grounds of structural geologists as well as Desert Peakers and gamblers. Here, the westernmost salient of the Rocky Mountain Overthrust Belt structural province, trending southwest out of Utah, meets the northwest-trending structural grain of the Las Vegas Shear Zone at a right angle. The result during the Laramide Crogeny - the time of formation of the Rocky Mountains - was enormous compressional deformation leading to massive overthrusting from the west which has actually shortened - "telescoped"-the crust in this area by stacking huge blocks of it atop each other. (While we have clear evidence that whole mountain ranges - for example, the Mormon Mountains - have "broken loose" from their roots and been shoved many miles to the east, the actual mechanisms by which this could occur remain one of the many mysteries of Creation.) A dramatic manifestation of this raw geologic violence is the sheer 2000' curtain of limestone which forms the south face of Moapa Peak, As three of us - Henry Heusinkveld, Graham Breakwell, and myself - hiked up a draw toward this great wall on the providentially cool, overcast morning of 20 April, it became obvious that this wall was in fact built of massive limestone strata which had been upended 90 to a perfectly vertical position. (A later check of the Geologic Map of Nevada showed that the Moapa massif is the southern edge of the great thrust plate to the north which comprises most of the Mormon Mountains; the crumpling of this plate against the underlying rock must have caused this awesome deformation.) I wondered how this wall would yield a reasonable route to the summit ridge, but, following the route in the excellent write-up in Sage #151, we gained the skyline with only a couple short pitches of third class and a lot of cautious route-finding. The technically easy but fearfully exposed summit ridge was engaged, and the three of us had completed a memorable climb of one of the most glorious peaks on the DPS List by the time evening shadows were beginning to fall over Jacks Pockets. Next morning we took a far better road than the Moapa approach to the jump-off point for the exploratory climb of Davidson Peak (5320'), high point of the East Mormon Mountains, a small but picturesque eastward - tilted fault block range about ten miles northeast of Moapa Peak. We followed the obvious, straightforward route - about 4 mi RT and 2000' gain - up the dip or "back" slope of the fault block to the top of Davidson. This route is written up, with a topo map, in Sage #138. It's a delightful peak, with great views of Moapa and the crumpled wilderness of the main Mormon range to the north. The 10,000-foot peaks of the Pine Valley Range north of St. George, Utah, could be seen to the east, There is a most impressive sheer drop-off from Davidson's summit down the west face, This part of the Nevada desert was at its peak of bloom; mallow, asters, and the Day-Glo flowers of hedgehog and beavertail, so intensely colored as to seem radioactive, were everywhere. We agreed that Davidson would be a fine addition to the List were it not so far from LA and so in the shadow of mighty Moapa. I had business in Las Vegas Monday, and on Tuesday I joined two friends from Denver, Edmund and Karen Mohr, who happened to be decadently vacationing at the Dunes, for a quick bag of Vegas' backyard peak, Frenchman Mountain (4054'). Most everyone who has ever taken Geology 101 (Rocks for Jocks) has met Frenchman Mountain in school; many elementary geology texts use it as a

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