REVUE DE VOLUME 35 (1 ) – 2016 PALÉOBIOLOGIE Une institution Ville de Genève www.museum-geneve.ch Revue de Paléobiologie, Genève (juin 2016) 35 (1): 111-247 ISSN 0253-6730 Jurassic/Cretaceous boundary in the Río Argos succession (Caravaca, SE Spain) Philip J. HOEDEMAEKER1, Nico M. M. JANSSEN1, Cristina E. CASELLATO2, Silvia GARDIN3, Daniela REHÁKOVÁ4 & Miroslava JAMRICHOVÁ4 1 Naturalis Diversity Center, Darwinweg 2, PO box 9517, 2300 RA Leiden, the Netherlands. E-mail: Philip Hoedemaeker: [email protected], Nico Janssen: [email protected]. 2 Universtà degli Studi di Milano, Dipartimento di Scienze della Terra, Sezione Geologia e Paleontologia, Via L. Mangiagalli 34, I-20133 Milano, Italia. E-mail: [email protected] 3 CNRS UMR 727, Centre de recherche sur la paléobiodiversité et les paléoenvironnements – CR2P, Case 104, 5 Place Jussieu, F-75252, Paris, France. E-mail: [email protected]. 4 Department of Geology and Palaeontology, Faculty of Natural Sciences, Comenius University, Mlynská dolina G-1, 842 15 Bratislava, Slovakia. E-mail: Daniela Reháková: [email protected], Miroslava Jamrichová: jamrichova. [email protected] Abstract An integrated biostratigraphic investigation has been performed of section Z of the Río Argos successions. Section Z is situated along the Barranco de Tollo, a left tributary of the Río Argos three kilometres west of the city of Caravaca, Province of Murcia, SE Spain. The sediments of section Z form part of the External Subbetic Zone of the Betic Cordillera. Section Z comprises the Jacobi Zone and the Subalpina Subzone, which is the lower part of the Occitanica Zone. The base of the Jacobi Zone, i.e. the base of bed Z1, conformably overlies beds in ammonitico rosso facies yielding ammonites of the Durangites vulgaris Zone. Sequence boundary Be1 is situated on top of bed Z4. The top of the Jacobi Zone (major sequence boundary Be3) is situated in a continuously deposited succession. The Jacobi zone can be divided into two parts, which are separated by sequence boundary Be2. Berriasella (Hegaratella) jacobi can still function as the index species for the lower part (equivalent to depositional sequence Be1). Instead of the appearance of Pseudosubplanites grandis in bed Z139, a more obvious and natural boundary between the ammonite faunas of the lower and upper part of the Jacobi Zone is formed by sequence boundary Be2. However for this upper part (equivalent to depositional sequence Be2) no index species could be indicated yet. However, Subthurmannia floquinensis is provisionally used as index species for the upper part of the Jacobi Zone. Hitherto the base of the Cretaceous System was defined by ammonites. The base of the Jacobi ammonite Zone is the base of the Berriasian Stage, which is the lowest stage of the Cretaceous. Bed Z1 yielded the first Berriasella (Hegaratella) jacobi (Wiedmann in Allemann et al., 1975). In the sections of Puerto Escaño (S. Spain) and Le Chouet SE France) the base of the Jacobi Zone is virtually situated at the same level as the base of polarity chron M19n, but it is not known how large the lacuna is at the major sequence boundary Be1. The belemnites from section Z are not well-preserved, and difficult to identify. The belemnite fauna mainly consists of species that have traditionally been recognized as indicative for the Late Jurassic (Tithonian Belemnite Association IV) and that were previously unknown from the earliest Cretaceous. The first “typical” Cretaceous belemnite, which is related to theDuvalia lata group, appears in bed Z131. The ranges of the species encountered in section Z should be considered with a certain reservation. As to the calpionellid zones, section Z covers the upper part of the Crassicolaria Zone, viz. the upper part of the Intermedia Subzone and the Colomi Subzone, and the lower part of the Calpionella Zone, viz. the Alpina (with the bloom of Calpionella alpina at its base), Ferasini, and Elliptica subzones. For specialists in calpionellids the bloom of Calpionella alpina at the base of the Calpionella Zone, which is also the base of the Alpina Zone, is considered the base of the Cretaceous. This base was demonstrated at the base of bed Z40. Calcareous nannofossil biostratigraphy was achieved on a total of 56 samples from section Z. Several primary and secondary bio- horizons were detected, allowing us to recognize three zones and two subzones in section Z, viz. the upper part of NJT-17a Subzone, the NJT-17b Subzone, the NKT and NK-1 zones, and a part of NK-2 Zone. Three (on a total of four) bio-horizons selected by the Berriasian Working Group as useful in locating the Jurassic/Cretaceous boundary were recognized. The first appearances of important nannoplankton species are marked in the lithological column. It appeared that, because of a nearby volcanic heat source, all non-calcareous dinoflagellate cysts of section Z are carbonized and that the rocks were totally remagnetized during the Miocene, so that magnetostratigraphy was not possible (Hoedemaker et al., 1998). However, sequence stratigraphy was quite clear and three sequences could be distinguished bounded by three sequence boundaries: Be1, Be2, and Be3. Submitted November 2014, accepted September 2015 Editorial handling: H. Parent DOI: 10.5281/zenodo.51872 112 Ph.J. HOEDEMAEKER et al. Keywords: J/K boundary, Berriasian, Jacobi Zone, ammonites, belemnites, calpionellids, calcareous nannofossils, sequence stratigraphy. Contents 1. General Introduction...................................................................................................................................................113 2. Ammonites ...............................................................................................................................................................115 2.1. Introduction .......................................................................................................................................................115 2.2. Ammonite fauna of the Jacobi Zone and Subalpina Subzone in section Z .......................................................116 2.2.1. Genus Pseudosubplanites Le Hégarat, 1973 (12 species) ....................................................................116 2.2.2. Subgenus Berriasella (Hegaratella) Nikolov & Sapunov, 1977 (10 species) ......................................127 2.2.3. Genus Chapericeras Hoedemaeker, 1982 (2 species) .........................................................................136 2.2.4. Subgenus Berriasella (Berriasella) Uhlig, 1905 (1 species) ...............................................................137 2.2.5. Genus Subthurmannia Spath, 1939 (2 species) ....................................................................................139 2.2.6. Subgenus Delphinella (Delphinella) Le Hégarat, 1971 (9 species) .....................................................141 2.2.7. Genus Dalmasiceras Djanélidze, 1921 (1 species) ..............................................................................148 2.2.8. Genus Substeueroceras Spath, 1923 (3 species) ..................................................................................149 2.2.9. Genus Tirnovella Nikolov, 1966 (3 species) ........................................................................................152 2.2.10. Genus Neocosmoceras Blanchet, 1922 (1 species) ..............................................................................154 2.2.11. Subgenus Himalayites (Himalayites) Uhlig, 1910 (1 species) .............................................................155 2.2.12. Subgenus Himalayites (Pomeliceras) Grigorieva, 1938 (1 species) ....................................................156 2.2.13. Genus Proniceras (Burckhardt, 1919) (1 species) ...............................................................................157 2.2.14. Genus Spiticeras Uhlig, 1903 (1 species) ............................................................................................158 2.2.15. Genus Negreliceras Djanélidze, 1922 (1 species) ...............................................................................158 2.2.16. Genus Protancyloceras Spath, 1924 (3 species) ..................................................................................159 2.2.17. Genus Bochianites Spath, 1922 (3 species) .........................................................................................160 2.2.18. Subgenus Ptychophylloceras (Semisulcatoceras) Joly, 2000 (2 species) ............................................162 2.2.19. Genus Holcophylloceras Spath, 1927 (1 species) ................................................................................164 2.2.20. Subgenus Phylloceras (Hypophylloceras) Salfeld, 1924 (1 species) ...................................................164 2.2.21. Genus Lytoceras Suess, 1865 (2 species) .............................................................................................165 2.2.22. Genus Protetragonites Hyatt, 1900 (1 species) ...................................................................................167 2.2.23. Genus Haploceras Zittel, 1884 (1 species, 2 dimorphs) ......................................................................167 2.3. Concluding remarks ..........................................................................................................................................170 2.3.1. Difference in ammonite faunal composition of the depositional sequences ........................................171 2.3.2. Comparisons with Puerto Escaño