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Title: Similarities in the dolomitization of upper Miocene reef complexes in Mallorca and the Las Negras areas, Spain: Possible evidence for a Mediterranean dolomitizing event during the Messinian

Reef complexes in the Las Negras area and the island of Mallorca, over 600 km to the northeast, contain dolomite with remarkably similar stratigraphic distribution and petrographic characteristics. In both reef complexes dolomite occurs as 5-50 {mu}m euhedral cements and microcrystalline replacement of red-algal fragments and muds. In addition, anhedral, moldic-zoned dolomite cements (5-20 {mu}m) are abundant in the youngest reefs of both areas. All inter-reefal erosional surfaces are cross-cut by dolomite cements. Distribution of dolomite within the reefal sequences is controlled by (1) proximity to the youngest reef margin. Dolomite abundances decrease from 100% to 0% over a 10 km transect into the platform interior in Mallorca. Stratigraphic and petrographic timing support a dolomitization event following exposure of the reefs, during initial deposition of the onlapping Messinian sequence in Mallorca, and before Pliocene deposition in Las Negras. In both areas, dolomitization took place as a Messinian transgression covered the reefs. Evidence for multiple dolomitization events has not been found. Mallorcan dolomites have heavy stable isotopes suggesting saline dolomitizing fluids. One hypothesis for dolomitization invokes brines associated with the deposition of extensive Messinian basinal evaporites. An early Messinian evaporitic lowstand could concentrate marine brines, and with the ensuing transgression bringmore » them in contact with CaCo{sub 3} platforms, dolomitizing them. The similar styles and timing of dolomitization in these two distinct and distant reef settings suggest that dolomitization of late Miocene reefs around the western Mediterranean may have been genetically related to the Messinian salinity crisis.« less
Authors:
;  [1] ;  [2]
  1. (SUNY, Stony Brook, NY (United States))
  2. (Univ. of Kansas, Lawrence (United States))
Publication Date:
OSTI Identifier:
7259816
Report Number(s):
CONF-910403--
Journal ID: ISSN 0149-1423; CODEN: AABUD
Resource Type:
Conference
Resource Relation:
Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States); Journal Volume: 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; BRINES; ROCK-FLUID INTERACTIONS; CARBONATE ROCKS; DIAGENESIS; PETROLOGY; SPAIN; GEOLOGIC DEPOSITS; CHEMICAL COMPOSITION; COMPARATIVE EVALUATIONS; CRYSTALLOGRAPHY; DOLOMITE; EVAPORITES; GEOCHEMISTRY; GEOLOGIC HISTORY; MEDITERRANEAN SEA; MINERALOGY; MIOCENE EPOCH; REEFS; CARBONATE MINERALS; CENOZOIC ERA; CHEMISTRY; DEVELOPING COUNTRIES; EUROPE; EVALUATION; GEOLOGIC AGES; GEOLOGIC STRUCTURES; GEOLOGY; MINERALS; ROCKS; SEAS; SEDIMENTARY ROCKS; SURFACE WATERS; TERTIARY PERIOD 580000* -- Geosciences