A review of the Tithonian ammonites from the Kachchh Basin, Western India

Twenty taxa of ammonites, represented by 53 specimens, are described from three sections of the highly ferruginous Umia Ammonite Beds of western Kachchh, Gujarat. The ammonites are representatives of the families Phylloceratidae, Haploceratidae, Perisphinctidae, Ataxioceratidae, and Berriasellidae and belong to the genera Ptychophylloceras, Holcophylloceras, Hildoglochiceras, Virgatosphinctes, Parapallasiceras, Paraulacosphinctes, Micracanthoceras, and Himalayites. Four ammonite levels can be distinguished. They are, in stratigraphic order, the Hildoglochiceras Horizon, and the Denseplicatus, Microcanthum, and Frequens ammonite zones, and stratigraphically represent the middle Lower to lower Upper Tithonian. The Umia Ammonite Beds are a condensed unit representing the maximum flooding zone of a transgressive-regressive cycle. The degree of condensation varies between the sections: While the four ammonite levels can be differentiated in the Katesar section, they are less clearly developed in the more strongly condensed Lakhapar section.