Tertiary Detrital Gypsum in the Madrid Basin, Spain: Criteria for Interpreting Detrital Gypsum in Continental Evaporitic Sequences
Published:January 01, 1994
María Esther Sanz, Juan Pablo Rodríguez-Aranda, Jose Pedro Calvo, Salvador Ordonez, 1994. "Tertiary Detrital Gypsum in the Madrid Basin, Spain: Criteria for Interpreting Detrital Gypsum in Continental Evaporitic Sequences", Sedimentology and Geochemistry of Modern and Ancient Saline Lakes Models, Robin W. Renaut, William M. Last
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The lower beds of the Miocene Intermediate Unit in the southern and southeastern parts of the Madrid Basin, central Spain, are formed mainly of mudstones, marls and gypsum. The mudstones contain euhedral gypsum crystals and are interpreted as the sediments of a saline mudflat environment. Two main types of gypsum deposit have been identified: (1) chemical precipitates, which include selenite and lenticular gypsum crystals, and (2) detrital gypsum grains. The latter form prominent deposits throughout the study area and display a wide variety of hydrodynamic structures, including scours, wavy bedding, parallel stratification, ripple lamination, parting lineation, graded bedding, and low-angle cross-stratification. The detrital gypsum beds are formed of sand-sized, hemipyramidal, lenticular or prismatic crystals that commonly exhibit abraded and/or partially dissolved edges.
We recognize four facies associations. The first, formed of mudstone and gypsum-bearing mudstone, is a typical saline mudflat association. The second consists of detrital gypsum deposits interbedded with gypsum-bearing mudstones. In this association, the detrital gypsum is interpreted as sheetflood deposits derived from the reworking of the mudflat facies during periods of heavy rainfall. The other two facies associations comprise different types of detrital gypsum deposits that are interbedded with marginal and/or more central, lacustrine evaporite facies. These facies associations allow us to characterize the different sedimentary subenvironments throughout a saline mudflat-saline lake complex.
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Sedimentology and Geochemistry of Modern and Ancient Saline Lakes Models
Sedimentology and Geochemistry of Modern and Ancient Saline Lakes - This volume of papers grew out of a four-day symposium entitled ?Sedimentary and Paleolimnological Records of Saline Lakes? held at Saskatoon, Canada in August, 1991. The aim of this Special Publication is to bring together selected papers from this conference that deal specifically with the sedimentological, inorganic geochemical, and hydrological aspects of salt lakes and their stratigraphic records. This volume is divided into four sections. The first section contains papers that deal with modern saline lakes. The second section contains papers dealing with sedimentation and diagenesis of late Quaternary salt lakes. The third and fourth sections contain papers devoted to ancient (pre-Quaternary) Lacustrine sequences.