Samples showing compactional slickensides

Slickensides are shiny rock surfaces lined by clay minerals. The clays
were brought into parallel alignment by sections of rock fracturing and
sliding past one another. This may occur by tectonic rupturing of rocks
(tectonic slickensides), by flowage of incompetent shaly sediment
during compaction, especially next to firm objects or irregularities in
adjacent competent beds (compactional slickensides), or by expansion
and contraction of clay-bearing rocks during soil formation (pedogenic
slickensides). These are compactional slickensides from weathered
shale just below the Worland Limestone.

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