Def. "a pair of sedimentary layers, a couplet, that form in an annual cycle as the result of seasonal weather changes"[1] is called a varve.

Pleistocene age varves at Scarborough Bluffs, Toronto, Ontario, Canada. The thickest varves are more than half an inch thick. Credit: Bruce F. Molnia, USGS.

"Typically formed in glacial lakes a varve couplet consists of a coarser grained summer layer formed during open-water conditions, and a finer grained winter layer formed from deposition from suspension during a period of winter ice cover. Many varve deposits contain hundreds of couplets."[1]

"The ruin marble structure of the Cretaceous/Paleogene fine-grained marly limestone from the Outer Flysch Belt of the Western Carpathians has a non-tectonic origin, according to structural and sedimentological evidence. Distinctive offsets of coloured red-brownish ferric oxyhydroxide bands are not due to displacements along rock-cutting fractures, as they superficially appear to be. Evidences for shear movement along these pseudo-faults were not observed. Band offsets result from different velocities of pervasively diffusing fluids, precipitating ferric oxyhydroxides in corridors bounded by sets of mineralised systematic joints. During rock weathering, calcite-filled joints operated as barriers for lateral fluid diffusion, but enabled longitudinal diffusion along healed joints."[2]

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References edit

  1. 1.0 1.1 Eleyne Phillips (16 December 2004). Glossary of Glacier Terminology. Reston, Virginia USA: United States Geological Survey. Retrieved 2014-11-09. 
  2. František Marko, Daniel Pivko and Vratislav Hurai (2003). "Ruin marble: a record of fracture-controlled fluid flow and precipitation". Geological Quarterly 47 (3): 241-52. Retrieved 2015-02-21.