![]() ![]() Using QmFLt and QtFL ternary diagrams allowed to infer that the sandstones of the Losero Formation were deposited in an active continental margin. Elemental ratios critical of provenance (La/Sc, Th/Sc, La/Cr, Th/Cr and Ba/Sc) are similar to sediments derived from weathering of mostly felsic rocks. ![]() ![]() These findings demonstrate that the sandstones were deposited by supercritical and subcritical flows as well as by unidirectional flows within channels and bars in a river system. Primary sedimentary structures include ripples, antidunes, flute and groove casts, cross and parallel lamination, desiccation cracks and soft-sediment deformation structures interpreted as seismites. The petrographic analysis revealed that the Losero Formation is constituted by litharenite and arkose, mostly derived from granitic and metamorphic basement rocks typical of the interior of a craton. We present a comprehensive geological analysis which includes collection of samples and elaboration of eight stratigraphic columns, followed by laboratory studies including petrography, trace element determinations using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and mineralogy by X-ray diffraction and Scanning Electron Microscopy (SEM). However, sedimentological, petrographic and geochemical evidence that supports a sedimentary or volcanic origin has not been discussed extensively. Most of the up-to-date studies of the Losero Formation have indicated that this formation corresponds to a Cenozoic volcanic sequence. AbstractThe Losero Formation is exposed in the Guanajuato Mining District, conformably overlying the Guanajuato conglomerate. ![]()
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