NOTCH PEAK: GREAT GEOLOGY

SHARP CONTACT BETWEEN METAMORPHOSED CAMBRIAN CARBONATES AND THE NOTCH PEAK INTRUSION.  IT IS NOT OFTEN THAT ONE CAN :PUT THEIR FINGER" ON SUCH A CONTACT

The House Range is one of those geological wonders found in the west desert of Utah and the Great Basin—it is a classic uplifted block of rocks, a horst, bounded by Tule and Sevier valleys, the grabens.  The Range is north-south trending (~40 mi X 7 mi) and generally exposes lower Paleozoic (Cambrian and Ordovician) rocks.  However, there is a major quartz monzonite (an igneous rock similar to granite but without the quartz) intrusive body of Jurassic age (Notch Peak Intrusion) called Sawtooth Mountain.  This name comes from the weathering of the monzonite into sharp points and ridges as compared to the more rounded peaks in the limestones and shales. 

NOTCH PEAK IN THE HOUSE RANGE.  THE PEAK IS CAPPED BY THE NOTCH PEAK DOLOMITE.  NOTE THE ORANGE-COLORED AND INTRUSIVE QUARTZ MONZANITE OF THE NOTCH PEAK INTRUSION.  PHOTO COURTESY OF WIKIPEDIA.

The dominant topographic feature of the Range is Notch Peak at 9654 feet, but with a vertical rise (cliff) of about 2200 feet at the summit.  The peak itself is floored by the Notch Peak Intrusion with overlying Cambrian and Ordovician carbonates and topped by the Notch Peak Dolomite. The igneous rocks have produced minor amounts of placer gold and some claims are still active.  It seems as though the source of the gold dust has never been located, perhaps representing an opportunity for prospectors to “strike it rich”!  One of the really “neat things” about the fascinating geology at Sawtooth Mountain is that one is able to “put your finger” on the contact between a major intrusive feature and a sedimentary rock and follow the metamorphic aureole outward.  This intrusive event is related to tectonic activity associated with the Nevadan Orogeny and is approximately 150 Ma in age. 

mike