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<p>The Paleocene–Eocene Maíz Gordo Formation (Salta Group, NW Argentina) records lacustrine to marginal lacustrine environments that hosted microbialite development under fluctuating paleoenvironmental conditions. This study characterizes a newly identified microbialitic level (MI) located on the southwestern slope of the Sierra de Zapla (Jujuy Province), through a multiscale approach combining stratigraphic, sedimentological, mesostructural, and microstructural analyses. The microbialites exhibit stratiform geometries with domical to semi-domical morphologies, laterally coalescing into a biohermal-type megastructure. Internally, three mesostructural zones (A, B, and C) were distinguished, consisting of clotted, alternately laminated, and clastic-rich fabrics. Porosity distribution is strongly controlled by microstructure, with clastic-rich zones showing the highest values, whereas laminated microstructures display distinctive fenestral and growth-framework porosities. Growth mechanisms varied through time, with trapping and binding dominating in clotted textures, biologically induced mineral precipitation in laminated textures, and episodic sediment supply driving clastic-rich structures. These variations reflect changes in hydrodynamic energy, sediment input, and carbonate saturation within a shallow alkaline lake setting, likely ranging from lower littoral to shallow littoral conditions. The results highlight the value of microbialites as reliable paleoenvironmental indicators for reconstructing the environmental dynamics of Paleogene continental basins in the Andes.</p>

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Paleoenvironmental conditions recorded in a microbialitic level from the Paleocene–Eocene Maíz Gordo Formation, Northwestern Argentina

  • 期刊论文

  • 发表日期：

    2026年7月6日

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  • Micaela Della Vedova,
  • Gabriel R. López-Isla,
  • Patricio G. Villafañe,
  • Agustín G. Romano,
  • Diego A. Herrera,
  • Juan M. Lezama,
  • Luis R. Horta

摘要

The Paleocene–Eocene Maíz Gordo Formation (Salta Group, NW Argentina) records lacustrine to marginal lacustrine environments that hosted microbialite development under fluctuating paleoenvironmental conditions. This study characterizes a newly identified microbialitic level (MI) located on the southwestern slope of the Sierra de Zapla (Jujuy Province), through a multiscale approach combining stratigraphic, sedimentological, mesostructural, and microstructural analyses. The microbialites exhibit stratiform geometries with domical to semi-domical morphologies, laterally coalescing into a biohermal-type megastructure. Internally, three mesostructural zones (A, B, and C) were distinguished, consisting of clotted, alternately laminated, and clastic-rich fabrics. Porosity distribution is strongly controlled by microstructure, with clastic-rich zones showing the highest values, whereas laminated microstructures display distinctive fenestral and growth-framework porosities. Growth mechanisms varied through time, with trapping and binding dominating in clotted textures, biologically induced mineral precipitation in laminated textures, and episodic sediment supply driving clastic-rich structures. These variations reflect changes in hydrodynamic energy, sediment input, and carbonate saturation within a shallow alkaline lake setting, likely ranging from lower littoral to shallow littoral conditions. The results highlight the value of microbialites as reliable paleoenvironmental indicators for reconstructing the environmental dynamics of Paleogene continental basins in the Andes.