Original Article

Carbonates and Evaporites

, Volume 30, Issue 1, pp 45-58

First online:

Microbial mixing zone dolomitization and karst development within Isla de Mona Dolomite, Isla de Mona, Puerto Rico

  • Jonathan SumrallAffiliated withDepartment of Geography and Geology, Sam Houston State University Email author 
  • , John MylroieAffiliated withDepartment of Geosciences, Mississippi State University
  • , Patricia KambesisAffiliated withDepartment of Geosciences, Mississippi State University

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Modification of the mixing zone model to include microbial processes that promote dolomitization explains many of the petrographic, isotopic, and outcrop observations found on Isla de Mona. Large flank margin caves at the contact between the Isla de Mona Dolomite and the capping Lirio Limestone formed during prolonged, likely episodic, periods with a stable lens position. These periods would produce a stable halocline. The halocline is hypothesized to be the zone of dolomitization in the microbial mixing zone model. Collection of organics at the density interface of the halocline coupled with sulfate reduction by sulfate-reducing bacteria would establish a geochemical environment that promotes dolomitization of the precursor limestone. This microbial community and geochemical environment would overcome the kinetic and thermodynamic barriers associated with the previous mixing zone model.


Karst Dolomite Mixing zone Isla de Mona