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Interplay between biotic and environmental conditions in pre-salt Messinian microbialites of the western Mediterranean (Upper Miocene, Mallorca, Spain)



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Suárez González, Pablo and Arenas Abad, Concha and Benito Moreno, María Isabel and Pomar, Luis (2019) Interplay between biotic and environmental conditions in pre-salt Messinian microbialites of the western Mediterranean (Upper Miocene, Mallorca, Spain). Palaeogeography, Palaeoclimatology, Palaeoecology, 533 (10924). ISSN 0031-0182

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Official URL: https://www.sciencedirect.com/science/article/pii/S0031018219302925


Microbial buildups that predate the Messinian salinity crisis, including one of the few Phanerozoic examples of ‘giant’ microbialites, crop out upon the island of Mallorca (W Mediterranean). Sedimentological and geochemical data from microbialites and associated deposits, both essentially dolomitic, indicate that they grew in shallow marine conditions but relatively restricted from the open marine realm. Two microbialite-bearing sequences occur, both consisting of subtidal to supratidal deposits. Periods of restriction led to evaporative and hypersaline conditions that favored the development of microbialites and local precipitation of sulfates. By contrast, ephemeral periods marked by more open conditions were devoid of microbialites and allowed production of bioclastic deposits. Microbialites range from decameter- to decimeter-scale, reflecting differences in accommodation space. Despite contrasting sizes, all microbialite bodies record similar mesostructure evolution through time, from thrombolites to stromatolites, with a sharp transition between these endmembers. The change from subtidal to shallower, more restricted and saline intertidal environments triggered biotic substitution of thrombolite-generating microbial communities to stromatolite-generating ones. Furthermore, a wide variety of microstructures, from agglutinated to micritic with fossilized microbes, indicates that two main accretion processes occurred: microbially-influenced primary dolomite precipitation and grain trapping and binding, which were controlled by the interaction between microbes and changes in environmental conditions (e.g. grain supply, hydrodynamics and hydrochemistry). Therefore, the diversity of macro-, meso- and microstructures of these microbialites was caused by a complex interplay between depositional, biotic and hydrological parameters, which offers useful insights for the palaeoecological interpretation of other examples, at any scale and throughout geological time.

Item Type:Article
Uncontrolled Keywords:Thrombolites, Stromatolites, Primary dolomite, Marine evaporative environments, Sedimentology, Geochemistry
Subjects:Sciences > Geology > Stratigraphic geology
Sciences > Geology > Geochemistry
Sciences > Geology > Petrology
ID Code:56925
Deposited On:05 Sep 2019 17:56
Last Modified:24 Sep 2019 08:51

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