Late Jurassic (Kimmeridgian) larger benthic Foraminifera from Santiago Coatepec, SE Puebla, Mexico

Abstract

A micropaleontologic study was carried out from samples collected along a section that crops out in the Santiago Coatepec Stream, located in the southeast of the state of Puebla, Mexico. The sedimentary sequence begins with a reddish conglomerate. Above, thick and thin layers of grey-greenish sandstones that continue in fine-grained, calcareous sandstones, and, finally, in limestones. The reddish conglomerate may represent a continental environment, and the marine transgression began with the sandstone deposit that contains a marine association of Invertebrates such as Trigonids ( Myophorella sp.), and other Mollusks such as Trichites sp., Ostreids and Gastropods, Echinoderms, and Sponges as Cladocoropsis mirabilis. This sequence also provides a rich assemblage of larger Foraminifera as well as Algae, which is reported for the first time in this site. The larger agglutinated Foraminiferal assemblage is composed of Alveosepta jaccardi, Pseudocyclammina lituus, Everticyclammina virguliana, Rectocyclammina chouberti, Choffatella cf. Ch. tingitana, Mesoendothyra croatica, Nautiloculina oolithica, Freixialina planispiralis, Audienusina fourcadei, Placopsilina sp., Pseudocyclammina sp., Meandrospira sp. and Lenticulina sp. All those taxa were adapted to special paleoecological conditions, such as a continuous terrigenous input. The Algae are Marinella lugeoni, Pseudoepimastopora jurassica, Permocalculus sp., and Halimeda sp. The stratigraphic distribution of the larger benthic Foraminifera allow us to propose a Kimmeridgian age for the studied sequence. The opening of the Atlantic Ocean permitted the colonization of its margins by the larger Foraminifera during this time. The data provided by the larger Foraminifera, the Algae, and the lithology may suggest an internal platform environment of warm shallow water. This foraminiferal association is constituted by cosmopolitan species which are frequent in the Tethyan Realm.