Person:
Suárez González, Pablo

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First Name
Pablo
Last Name
Suárez González
URI
https://hdl.handle.net/20.500.14352/75279
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Geodinámica, Estratigrafía y Paleontología
Area
Estratigrafía
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2019 - 201912020 - 20211
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Subject: 550.7(460.32) ×

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    Interplay between biotic and environmental conditions in pre-salt Messinian microbialites of the western Mediterranean (Upper Miocene, Mallorca, Spain)
    (Palaeogeography, Palaeoclimatology, Palaeoecology, 2019) Suárez González, Pablo; Arenas Abad, Concha; Benito Moreno, María Isabel; Pomar, Luis
    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.
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    Columnar microbialites of the upper Miocene of Mallorca (Spain): A new morphogenetic model based on concurrent accretion and bioturbation – uncommon or overlooked?
    (Sedimentology, 2021) Suárez González, Pablo; Benito Moreno, María Isabel; Arenas Abad, Concepción; Pomar, Luis
    Bioturbation has long been considered an antagonist of microbialite development and preservation, because metazoan grazing and burrowing destroy benthic microbial communities. However, metazoan bioturbation, in conjunction with microbial accretion, may have had a significant role in the morphogenesis of some columnar microbialites, as suggested by the case study presented and by some Phanerozoic and Upper Proterozoic analogues discussed here. Late Miocene in age, the studied microbial biostrome developed in a western Mediterranean restricted shallow-water platform dominated by grainy sediments and with a notable influence of bioturbation. This study is focused on the complex accretionary history of the columnar microbialite biostrome and on its striking dark grey colour, which is attributed to Mn-oxyhydroxides precipitated during meteoric diagenesis linked to subaerial exposure. The characteristic columnar structure of the microbialite biostrome has features consistent with an accretionary origin of the columns, but also has features suggesting metazoan disruption. Therefore, a new morphogenetic model for columnar microbialites is presented, highlighting the concomitant roles of microbial accretion, bioturbation and grainy sediment infill of the intercolumn space. Whether this model is an exception or a rule, should be tested on other examples of Phanerozoic and Upper Proterozoic columnar microbialites. Nevertheless, this model is a step forward in understanding the complex microbe–metazoan interactions as constructive coexistence rather than just as destructive competition.