Boletín de la Sociedad Geológica Mexicana Volumen 73, núm. 1, A080620, 2021 http://dx.doi.org/10.18268/BSGM2021v73n1a080620

Evolución paleoambiental de la diatomita de Agostitlán, Michoacán, durante la transición Pleistoceno-Holoceno

Paleoenvironmental evolution of the Agostitlán diatomite, Michoacán, during the Pleistocene-Holocene transition

Ma. de Jesús Sánchez-González^1,*, Isabel Israde Alcántara², Juan Julio Morales³, Avto Goguitchaichvili¹

¹Doctorado en Ciencias de la Tierra, Instituto de Geofísica Universidad Nacional Autónoma de México. Ciudad Universitaria, 04510 Coyoacán, CDMX, México.

²Instituto de Investigaciones en Ciencias de la Tierra (INICIT), Universidad Michoa­cana de San Nicolás de Hidalgo. Avenida Francisco J. Múgica S/N, Edificio U-4 Ciudad Universitaria, 58030, Morelia, Michoacán, México.

³Laboratorio Interinstitucional de Magnetismo Natural (LIMNA), Unidad Michoacán del Instituto Geofísica, Universidad Nacional Autónoma de México, Antigua Carretera a Pátzcuaro No. 8701, Col. Ex Hacienda de San José de la Huerta, 58190, Morelia, Michoacán, México.

* Autor para correspondencia: (M.J. Sánchez-González) This email address is being protected from spambots. You need JavaScript enabled to view it.

How to cite this article:

Sánchez-González, M.J., Israde Alcántara, I., Morales, J.J., Goguitchaichvili, A., 2021, Evolución paleoambiental de la diatomita de Agostitlán, Michoacán, durante la transición Pleistoceno-Holoceno: Boletín de la Sociedad Geológica Mexicana, 73 (1), A080620. http://dx.doi.org/10.18268/BSGM2021v73n1a080620

ABSTRACT

The Chapala Acambay graben is characterized by several Quaternary diatomite deposits of variable thickness where dominates flora indicative of ancient deep lakes. The 6.70 m thickness diatomite-deposit of the Agostitlan dammed basin contains the paleoenvironmental record that show the transition from less cold conditions of 37,000 yr cal AP until the onset of the late Glacial period (ca. 25,000 yr cal AP). At the beginning of the lake formation a deep-water body was developed, characterized mostly by Stephanodiscus niagarae with little contribution of detrital material, mostly composed of argillaceous lithology. The magnetic susceptibility values in this first episode of the lake are relatively low, at least in the first two meters, with two notorious maxima associated with periods of erosion of the high-mountain ranges. Successively towards the Early Glacier the lake conditions become fluctuating; the sedimentation is more detrital, alternating with episodes of fine sedimentation in which the lowest values of magnetic susceptibility are revealed, which are accompanied by the decrease of Stephanodiscus spp communities and an increase of Aulacoseira ambigua and Fragilaria spp. This indicates an environment of dominantly cold and alkaline conditions. The top of the succession is characterized by an increase in the concentration of magnetic minerals, as well as by a significantly decrease of planktonic that becomes substituted by littoral benthic and periphytic species, which are interpreted as the response to the increase in aridity in this area at the beginning of the Last Glacial Maximum.

Keywords: Diatomitas, Central Mexico, Environmental Magnetism, MIS3, late Wisconsin.