Late-latest Maastrichtian foraminiferal assemblage from the Angostura Platform, Chiapas, SE Mexico: Biostratigraphic, paleoenvironmental and paleobiogeographic significance

Abstract The carbonate platform deposits of the Angostura Formation are widely distributed in the central and eastern part of the Sierra de Chiapas, SE Mexico. The Angostura Formation contains a rich assemblage of foraminifera associated with mollusks (rudists, gastropods), corals, and dasycladacean green algae. A detailed foraminiferal study was carried out on samples from the El Coyol section of the Angostura succession. The studied section crops out in the El Coyol Hacienda located north of the Angostura dam, SE of the city of Tuxtla Gutierrez in Central Chiapas. The foraminiferal assemblage consists mostly of benthic larger foraminifera but minor pelagic influence is represented by the presence of a number of planktic foraminifera. The benthic foraminiferal association is taxonomically diverse, being composed of Chubbina jamaicensis Robinson, Chubbina macgillavry Robinson, Caribealveolina michaudi Pecheux, C. fourcadei Vicedo, Caus and Frijia, C. obesa (Fourcade and Fleury), Praechubbina breviclaustra Fourcade and Fleury, Omphalocyclus macroporus (Lamarck), Asterorbis rooki Vaughan and Cole, Vaughanina cubensis (Palmer), V. barkeri , Bronnimann, Sulcoperculina dickersoni (Palmer), S . globosa de Cizancourt, S. vermunti (Thiadens), Lepidorbitoides minima Douville, Orbitoides cf. O. apiculata Schlumberger, Planorbulina cretae ( Marsson), Smoutina cruysi Drooger, and Nezzazatinella sp. In addition, the occurrence of Fleuryana adriatica De Castro, Drobne and Gusic, Rhapydionina cf. R . liburnica Stache, Cuneolina ketini Inan, Valvulina cf. V. triangularis d'Orbigny and Minouxia sp. is documented for the first time from the Angostura Formation. The planktic foraminifera are Rugoglobigerina macrocephala Bronnimann, R. cf . R. hexacamerata Bronnimann, R. rugosa (Plummer), Kuglerina rotundata (Bronnimmann), Muricohedbergella monmouthensis (Olson), Planoglobulina cf. P . carseyae (Plummer), Globotruncanita stuarti (de Lapparent), Globotruncanita pettersi (Gandolfi), Planoheterohelix globulosa (Ehrenberg), Pseudoguembelina sp., Macroglobigerinelloides prairielillensis (Pessagno) and the pithonellids Pithonella ovalis (Kaufmann) and P. sphaerica (Kaufmann). The age of the Angostura Formation in the studied section is late to latest Maastrichtian. A Chubbina jamaicensis Taxon Range Zone is proposed on the basis of the occurrence of the nominal taxon and foraminiferal association. The lithological and faunal evidence enable the paleoenvironment to be reconstructed. The microfacies (wackestone–packstone, wackestone–floatstone, wackestone, grainstone and packstone) as well as the foraminiferal assemblage suggest that the deposit was developed in a shallow water marine setting with low to moderate energy, with sporadic intercropping of an open platform deposit characterized by planktic foraminifera and pithonellids. The paleobiogeographical distribution of the foraminiferal association from the Angostura Formation contains cosmopolitan genera as well as endemic forms of the Caribbean Province from the Tethys Realm.