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Diagenetic evolution of Tortonian temperate carbonates close to evaporites in the Granada Basin (SE Spain)

  • Lopez-Quiros, A.
  • Barbier, Mickael
  • Martin, J. M.
  • Puga-Bernabéu, Angel
  • Guichet, Xavier
Publication Date
Jan 01, 2016
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The Granada Basin (SE Spain) is a small basin located in the central part of the Betic Cordillera, structured as suchin the late Tortonian and initially connected to the Atlantic Ocean and to the Mediterranean Sea. During the lateTortonian, normalmarine conditions prevailed, leading to the deposition of skeletal carbonate sediments on platformsaround structural highs. The marine connections were later interrupted, first to the Atlantic Ocean andthen to theMediterranean Sea, and a thick evaporite sequence,marking the transition frommarine to continentalconditions,was deposited during the latest Tortonian. In thiswork, the diagenetic evolution of the Tortonian temperatecarbonates (TTC), underlying and close to the evaporite bodies, is revealed and discussed. The diageneticstudy includes petrographic analyses (conventional petrography, cathodoluminescence, and fluorescence), geochemicalanalyses (major,minor and trace elements, and δ13C and δ18O stable isotopes), and microthermometryof fluid inclusions. In the TTC, marine diagenetic processes such as micritization and fibrous calcite-cement precipitationand mechanical compaction took place during or just after deposition (Eogenesis). An initial burialevent (Mesogenesis 1) is characterized by: 1) stabilization of the temperate-water carbonates by freshwater,and 2) porosity occlusion via precipitation of low-Mg bladed and syntaxial/mosaic calcite cements. The TTCwere then subaerially exposed (or got close to the surface) during evaporite deposition and underwent pedogenesis,Mg-smectite infiltration, and pyrite formation (Telogenesis 1). Subsequent brine-related diagenetic alterations,such as dolomitization and silica, halite, and sylvite replacements of carbonate grains occurred during asecond burial episode (Mesogenesis 2) concomitant with theMessinian lacustrine deposition, this being followedby chemical compaction (stylolite formation). Finally, the area was uplifted and the TTC exhumed.Microstalactitic (dripstone) and fibre/whisker calcite cement precipitation and extensive dissolution relate tothis Pliocene–Quaternary late event (Telogenesis 2). In the study case diagenetic history is closely linked tobasin evolution, as diagenetic pathways of carbonate rocks were related to major geodynamic events, includingbasin restriction leading to evaporite deposition, and several episodes of subsidence and uplift. Up to now, onlyvery fewdiagenetic studies have attempted to demonstrate this correlation between diagenetic history and basinevolution.

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