CONTORTED BEDS IN THE LATE PALEOZOIC SEQUENCE OF THE CENTRAL COLORADO BASIN EXPOSED ALONG I-70 NEAR GYPSUM, COLORADO.|
|GYPSUM DESERT ROSE COLLECTED FROM NEAR ST. DAVID, ARIZONA, IN THE COLLECTION, AND COURTESY, OF ROGER WELLER AT COCHISE COLLEGE (WHOSE ROSE IS MUCH BETTER THAN WHAT I COLLECTED).|
|BROKEN SELENITE CRYSTALS LITTER THE SURFACE AT THE ST. DAVID LOCALITY.|
|SAN PEDRO RIVER GRABEN SHOWING ANCIENT LAKE AND STREAM SEDIMENTS/ROCKS EXPOSED BY RECENT DOWN CUTTING BY THE RIVER. THE DESERT ROSES ARE FOUND IN THESE SEDIMENTS. THE DRAGOON MOUNTAINS, A HORST OR FAULT-UPLIFTED BLOCK, BOUND THE VALLEY ON THE EAST.|
St. David is a watery oasis in the middle of the desert and numerous springs and lakes are quite evident; irrigated agriculture is noticeable. Certain layers of the ancient lake and stream sediments in the graben seem to confine the ground water running into the valley and it reappears as artesian wells in the bottom of the San Pedro River Valley. Members of the LDS church (Mormons) found the town in the 1870’s because of the abundance of water for growing crops.
U. S. Department of Agriculture, 2003, Soil Survey of Cochise County, Arizona: http://soildatamart.nrcs.usda.gov/Manuscripts/AZ671/0/cochise.pdf