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Secondary precipitates in Pleistocene and present cryogenic environments (Mendoza Precordillera, Argentina, Transbaikalia, Siberia, and Seymour Island, Antarctica)
Author(s) -
VOGT THEA,
CORTE ARTURO E.
Publication year - 1996
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/j.1365-3091.1996.tb01459.x
Subject(s) - geology , pleistocene , calcite , paleontology , vadose zone , aragonite , geochemistry , phreatic , glacial period , early pleistocene , geomorphology , groundwater , aquifer , geotechnical engineering
Secondary precipitates (iron oxide, calcite, etc.) are currently observed in cold‐climate Pleistocene deposits. Some have micro‐ and ultrastructures quite different from precipitates of vadose, phreatic and biogenic origin, and seem to have originated by freezing processes. The microstructures of calcite coatings from a Pleistocene cryopediment in the Mendoza Pre‐Cordillera, from a Lower Pleistocene cryogenic slope deposit in Western Transbaikalia and from the present active layer in Antarctica are described. They show similar patterns: fibrous crystals often consisting of piles of platelets, some with internal holes, assembled in millimetre‐scale fringes on the lower face of clasts. Observational (mainly fabric) evidence confirms that such peculiar crystals are formed during freezing. The features are unknown in other climates and, when found in past sediments, can be diagnostic of cryogenic palaeoenvironments.