Ammonite biostratigraphy of the uppermost Tithonian, Berriasian, and lower Valanginian along the Río Argos (Caravaca, SE Spain)

This paper deals with the ammonite biostratigraphy of the lower 312 m of the Miravetes Formation (sections Y and Z) exposed 500 m north and northwest of Los Miravetes along the Río Argos, 3 km west of Caravaca (SE Spain). This sequence embraces the uppermost Tithonian, Berriasian, and lower Valanginian. The succession of ammonite assemblages is similar to the one described by Le Hégarat (1971) from SE France. Le Hégarat's results are, where possible, completed and, where necessary, corrected. Arguments are adduced for a stratigraphic position of the Tithonian-Berriasian boundary, which should also be the Jurassic-Cretaceous boundary, between the Pseudosubplanites grandis and Subthurmannia (Strambergella) subalpina subzones. The Berriasian was divided into two zones, the lower Subthurmannia (Strambergella) occitanica Zone and the upper Subthurmannia (Subthurmannia) rarefurcata Zone. The latter comprises only the Berriasella (Malbosiceras) paramimouna and Berriasella (Berriasella) picteti subzones. Also arguments were adduced for a stratigraphic position of the Berriasian-Valanginian boundary between the B. (B.) picteti Subzone and the here proposed Tirnovella alpillensis Subzone. The latter can be correlated with the 'Sous-zone à Callisto' of Le Hégarat & Remane (1968), which is inadequately characterized with respect to its ammonite association. The T. alpillensis Subzone is the lowest subzone of the Thurmanniceras (Kilianella) retrocostatum Zone, here proposed, which also encloses Le Hégarat's Tirnovella pertransiens Subzone in the middle and the here proposed Sarasinella trezanensis - Thurmanniceras (Kilianella) pexiptychum Assemblage-subzone at the top. The Pseudosubplanites euxinus Zone (Wiedmann in Allemann et al., 1975), which is shown to embrace the Berriasella (Hegaratella) jacobi and Pseudosubplanites grandis subzones, is adopted as the name for the topmost Tithonian zone. Finally Neumayr's (1871) Paraulacosphinctes transitorius Zone and Kilian's (1888) Subthurmannia (Subthurmannia) boissieri and Thurmanniceras (Kilianella) roubaudianum zones are reinstated in their original faunistical sense and treated as superzones. For a better understanding of the author's interpretation of some taxa, palaeontological notes are added. In these a new genus, Pseudoneocomites, is introduced.