Abstract

OMANA, Lourdes  and  ALENCASTER, Gloria. Lower Aptian shallow-water benthic foraminiferal assemblage from the Chilacachapa range in the Guerrero-Morelos Platform, south Mexico. Rev. mex. cienc. geol [online]. 2009, vol.26, n.3, pp.575-586. ISSN 2007-2902.

Lower Cretaceous shallow-water benthic foraminifera were recovered from the lower part of a limestone sequence that crops out in the Chilacachapa range in the Guerrero-Morelos Platform paleogeographic unit in southern Mexico. The benthic foraminiferal association consists of Palorbitolina lenticularis, Choffatella cf. decipiens, Melathrokerion valserinensis, Glomospira urgoniana, Istriloculina eliptica, Pseudocyclammina sp., Ammovertellina sp., and Lenticulina sp. This association is documented here for the first time in the study area and Melathrokerion valserinensis for the first time in Mexico. An early Aptian age was assigned to the sequence on the basis of the size of the embryonic chamber and test characters of Palorbitolina lenticularis. The observed lithology and foraminiferal faunas suggest a warm shallow-water platform environment. The benthic foraminiferal assemblage is considered typical of the Tethys realm, corresponding to the Barremian-Aptian boundary platform expansion, as the same benthic foraminifera are present at many localities in the Old and New World.

Keywords : benthic foraminifera; shallow-water platform; Tethys realm; early Aptian; Chilacachapa range; Guerrero-Morelos platform; Mexico.

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