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The Apache Group near the bottom of the Grand Canyon, includes fluvial shale and sandstone, as well as limestone from a shallow sea, exposed in the Salt River Canyon. The limestone contains stromatolite remains, mounds of blue-green algae. The Apache Group was intruded with basalt and diabase between 1.05 and 1.14
Desert pavement evolution. Desert pavement surfaces are often coated with desert varnish, a dark brown, sometimes shiny coating that contains clay minerals. In the US a famous example can be found on Newspaper Rock in southeastern Utah. Desert varnish is a thin coating (patina) of clays, iron, and manganese on the surface of sun-baked boulders.
An AH-64A Apache from the 2nd Squadron, 6th Cavalry Regiment, leaves an enormous cloud of dust after landing at a desert airstrip in central Iraq. October 19, 2001, Dalbandin , Pakistan — U.S. Army Rangers, Task Force 3/75 MH-60 K Black Hawk — As the search and rescue helicopter approached to land at night, it caused a brownout, obscuring ...
For example, GW-GM corresponds to "well-graded gravel with silt." If the soil has more than 15% by weight retained on a #4 sieve (R #4 > 15%), there is a significant amount of gravel, and the suffix "with gravel" may be added to the group name, but the group symbol does not change. For example, SP-SM could refer to "poorly graded SAND with silt ...
Caliche fossil forest on San Miguel Island, California. Caliche (/ k ə ˈ l iː tʃ iː /) (unrelated to the street-slang "Caliche" spoken in El Salvador) is a soil accumulation of soluble calcium carbonate at depth, where it precipitates and binds other materials—such as gravel, sand, clay, and silt.
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Variations in the type and proportions of precipitated iron oxides resulted in the different black, brown, crimson, vermillion, orange, salmon, peach, pink, gold, and yellow colors of the Navajo Sandstone. The precipitation of iron oxides also formed laminae, corrugated layers, columns, and pipes of ironstone within the Navajo Sandstone.
Gravel (/ ˈ ɡ r æ v əl /) is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentary and erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gravel is classified by particle size range and includes size classes from granule- to boulder-sized fragments