🌎 Sometimes You've Got to Stick Together! 🌏 EarthCache

This is an EarthCache. As such there is no physical container or physical log. To earn credit for finding this cache, you must visit the posted coordinates, make personal observations, and formulate conclusions based on your observations and careful reading of the cache description. Then, send me the answers to the questions listed under "Logging Requirements" via my geocaching.com profile per the guidelines. Do not post your answers online. You don't need to wait for my response to log your find. I will contact you if there is a problem with your answers.

Please use the date of your observation for the found date, not the date that you finally get a chance to submit and log it.

1. Cache title, date, and with whom did you make this observation?
2. What did you observe at the posted coordinates?
3. What stage of caliche development do you see at the second waypoint? Describe the observed characteristics including aggregate 
4. Where did the concretions at the third waypoint come from? Why did they break away?
5. Post a picture of you (or some personal identifying item) at the posted coordinates with the Goldfield Mountains (to the north) in the background or send said picture with your response to me. This picture is REQUIRED in accordance with current guidelines for EarthCaches.

This EarthCache is located on Arizona State Trust Land. Geocachers must purchase an annual recreation permit available on the Arizona State Land Department website. This EarthCache is located about 600 feet from the nearest access point. The majority of the trail is relatively smooth and level except the portion where the trail drops down into the wash which is steep and slippery. Note: There are hundreds of geocaches located on Arizona State Trust Land so it's well worth the small annual investment for the permit! Removal of any natural products is not permitted.

This EarthCache involves three points to consider. The first is at the posted coordinates and spans the width of the trail at this point. The second is 100 feet in a westerly direction. While the whole western side of the wash exhibits caliche development, the second point of interest is the near vertical section below the palo verde tree. The third waypoint is about 30 feet downstream at the base of the west wall of the wash. With the exception of navigating the trail down into the wash, there is no need to scale the steep sides of the wash. Observations of points two and three should be made from the bottom of the wash. The wash is cut into an alluvial fan from the Goldfield Mountains.

According to Péwé, “Caliche is an epigenetic accumulation of calcium carbonate derived from soil processes in unconsolidated sediments in climates where moisture is deficient during all seasons. Such deposits are common throughout the Phoenix Basin and the adjoining and intervening ranges.” Caliche forms as rainwater percolates downward into the soil carrying calcium carbonate in solution. In situ evaporation of this water results in the precipitation of the CaCO₃ in soil or rock voids. Caliche deposits are generally sheet-like, forming parallel to the ground surface.

Diagram from Gile (1975) as used in Péwé. Attributed to Péwé in Arrowsmith.

Caliche generally exhibits progressive development with time. Weakly developed caliche coats the underside of rocks, then builds up and fills the spaces between pebbles in the moderately developed stage. Eventually, all the pebble spaces become filled, creating a plugged, impermeable layer in the strongly developed stage. Since water can percolate no further, the very strongly developed stage will exhibit upper layers of pure laminated CaCO₃.

The bank of a wash may exhibit repeated layers of caliche, separated by deposits of weakly to non-calichified sediments, indicating interruptions in the formation of caliche. It’s assumed that the non-calichified sediments were deposited at a rate too great for caliche to develop.

There is an excellent example of very strongly developed caliche in the road cut north of Thomas Road on the west side of Higley Road. It's not used in this EarthCache since it's easily viewable in Google Streetview but it's worth a visit when you have a chance.

Boulder: rocks larger than 10 inches in diameter

Caliche: a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials, normally white or very light in color

Cobble: rocks from approximately 2.5 inches to 10 inches in diameter

Epigenetic: forming later than the surrounding or underlying rock formation

Meteoric: relating to or denoting water derived from the atmosphere by precipitation or condensation

Pebble: small rocks from approximately 1/8 inch to 2.5 inches in diameter

Web Resources:

• Arrowsmith, R., 2001, Field trip guide: Urbanization, landscape, and geologic history along the Salt River, eastern Maricopa County, AZ downloaded from http://activetectonics.asu.edu/qgeo/ahsft.pdf on Oct. 31, 2020
• Bales, J. T., Wellendorf, C. S., and Péwé, T. L., 1986, Caliche Tempe Quadrangle, Maricopa County, Arizona, State of Arizona Bureau of Geology and Mineral Technology, Geologic Investigation Series Map GI-2-G downloaded from http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1413/tempegi-2-g.pdf on Nov. 4, 2020
• Péwé, T. L., 1978, Terraces of the Lower Salt River Valley in Relation to the Late CenozoIc History of the Phoenix Basin, Arizona, in Burt, D. M., and Péwé, T. L., Guidebook to the Geology of Central Arizona: Arizona Bureau of Geology and Mineral Technology, Special Paper No. 2, p. 1-45. downloaded from http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1931/sp2-chp1-p1-46.pdf on Nov. 1, 2020
• Skotnicki, S. and Ferguson, C. 1997, Bedrock Geologic Map of the Apache Junction and Buckhorn Quadrangles, Maricopa and Pinal Counties, Arizona – Report, Arizona Geological Survey Open File Report 96-8 downloaded from http://repository.azgs.az.gov/sites/default/files/dlio/files/2010/u14/ofr-96-8.pdf on Nov. 1, 2020
• Skotnicki, S. and Ferguson, C. 1997, Bedrock Geologic Map of the Apache Junction and Buckhorn Quadrangles, Maricopa and Pinal Counties, Arizona downloaded from http://repository.azgs.az.gov/sites/default/files/dlio/files/2010/u14/apachejunction_azgs-ofr96-08_1of2_opt.pdf on Nov. 1, 2020