siltstone - teaching hand specimen of a moderately lithified tan to gray Miocene siltstone
This siltstone is Miocene in age, is moderately lithified and was deposited in a closed basin in a non-marine or brackish marine depositional environment. It is mapped as a unit of the Ridge Route Formation, part of the Ridge Basin Group. It is relatively well cemented, so will withstand student examination.
The silt grains in these specimens are smaller than those of a sandstone and when rubbed off, feel gritty. It would be instructive to compare this siltstone with a larger grained sandstone, and with a siltstone that is cemented with silica. This siltstone has a calcium carbonate cement which effervesces with a drop of dilute hydrochloric acid.
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