Middle Toarcian Ammonitina from the Gerecse Mts, Hungary

In the Gerecse Mts, Jurassic successions built of sedimentary rocks characteristic of the peri-Mediterranean region are found. The lower part of the Toarcian stage, largely representing the "Ammonitico Rosso marl" facies, contains very diverse and abundant ammonite faunas. Bed-by-bed sampling of four sections carried out during the late seventies and early eighties of the last century has resulted in the collection of more than 15 000 specimens, the bulk of them belonging to the orders Phylloceratina and Lytoceratina. Due to the presence of very rare index forms of the suborder Ammonitina, the successions could be fitted into the zonal scheme established for the NW European Toarcian. The aim of the present paper is to provide information on the stratigraphic distribution of Ammonitina in the Bifrons and Gradata Zones as well as to present a subzonal subdivision of these beds.