Saint David area, Cochise Co., Arizona, USA
|Latitude & Longitude (WGS84):||31° 54' 15'' North , 110° 12' 49'' West|
|Latitude & Longitude (decimal):||31.90417,-110.21361|
|Other regions containing this locality:||San Pedro river valley, Arizona/Sonora, USA/Mexico|
Sonoran Desert, North America
|Köppen climate type:||BSk : Cold semi-arid (steppe) climate|
The St. David area is an alluvial outflow from the Whetstone Mountains to the West. At the San Pedro River in the center of the valley the alluvial deposits are up to fifteen hundred feet in depth.
Subsequent erosion cut through layers of soil, exposing the various deposition levels.
Soil saturation of rainwater and subsequent evaporation allowed deposition of gypsum in many forms. Opal also formed in the same way above impervious layers of caliche or clays.
Quartz, magnetite, garnet, iron and other minerals are found in the outflow washes. Some of the opal and silica pods are slightly radioactive from the marginally commercial deposits in the Whetstone Mountains.
Mindat ArticlesFluorescent Common Opal of St. David, Arizona by Rolf Luetcke
Pseudomorph Crystal Discovery by Rolf Luetcke
Saint David Gypsum Collecting by Rolf Luetcke
12 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Holocene - Gelasian|
0 - 2.588 Ma
|Quaternary surficial deposits, undivided|
Age: Pleistocene (0 - 2.588 Ma)
Description: Unconsolidated to strongly consolidated alluvial and eolian deposits. This unit includes: coarse, poorly sorted alluvial fan and terrace deposits on middle and upper piedmonts and along large drainages; sand, silt and clay on alluvial plains and playas; and wind-blown sand deposits. (0-2 Ma)
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.