siltstone - tan siltstone from the Round Mountain Silt member of the Temblor Formation - unit of 5 student specimens
The Round Mountain Silt is famous for the now-national-landmark Sharktooth Hill fossil collecting locality. Siltstone fits between shale and sandstone in a classification of sedimentary rocks by grain size. Siltstones have a range of grain sizes as well, with this one being close to the finer-grained end of the siltstone spectrum.
The farther a sediment is transported, the smaller and rounder its grains become. Finer grained sediments take longer to settle out of the water column and are deposited farther from a shoreline in deeper water. This siltstone is marine and some specimens are fossiliferous with small clams. Their delicate shells confirm that this is a deep water sediment, as the shells are too fragile to withstand the high energy near-shore environment.
These specimens were collected from outcrops along the south edge of the floodplain of the Kern River in Kern County, California. They will withstand student examination without crumbling. Some of these contain a small clam, giving you the opportunity to ask your students, “Igneous, sedimentary or metamorphic, and why do you say so?”
Select a specimen: When more than one specimen is shown, you can select a particular specimen by telling us what is in the photo with it, a black and silver pen, a black mechanical pencil, a blue and silver pen, or one of those plus some number of coins, or you can let us make the selection.
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