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- Title
Beidellite-nontronite clays in Neogene sediments from Cuitzeo-Charo lacustrine basin Michoacán, México. Geological setting and paleoenvironmental implications.
- Authors
Israde-Alcántara, Isabel; Robles-Camacho, Jasinto; Domínguez, José Manuel
- Abstract
Lacustrine and fluviolacustrine deposits of the Charo sequence crop out extensively along tens of kilometres, and they overlie the Miocene volcanic sequences of the Mil Cumbres Complex in an E-W oriented basin. Eastwards of Morelia city (central Mexico), layers of non lithified clayey sediments of about 3 m in thickness are overlaid by massive diatomite deposits developed during the Miocene-Pliocene in the Cuitzeo palaeolake. Major outcrops are located south and east of the village of Charo at the Las Pulgas, Lomas Blancas and Tzitzimeo sites; all having similar mineralogical facies and stratigraphic correlation. Field studies, petrography and X-ray fluorescence spectrometry (XRF) indicated that the parent rock was mainly of andesitic composition with minor dacitic-rhyolitic components. The source of the raw material was located in the upper topographic levels of the present horst-graben system. The diagenetic clays were identified as smectites. The central part of the Las Pulgas column shows a beidellite-nontronite (B-N) association. Likewise, 27Al-NMR and Mössbauer spectroscopies confirm the B-N character. Interlaid and overlying diatomite strata indicate a lacustrine environment, favourable to the development of secondary clays. The stability of lacustrine conditions gave place to an incipient stratification (smectite-illite), better developed in the middle part of the clayey levels.
- Subjects
NEOGENE paleoseismology; FIELD research; PLIOCENE-Pleistocene boundary; MIOCENE paleoecology; BEIDELLITE; NONTRONITE
- Publication
Boletín de la Sociedad Geológica Mexicana, 2008, Vol 60, Issue 2, p159
- ISSN
1405-3322
- Publication type
Article
- DOI
10.18268/BSGM2008v60n2a2