%0 Journal Article 
%A Sandoval, J.
%A Aguado, R.
%A Fraguas, A.
%A O'Dogherty Luy, Luis Carlos
%T The lower/upper Bajocian boundary (Middle Jurassic) in the Casa Chimeneas section: Sierra de Ricote (Murcia Region), southern Spain
%D 2025
%U http://hdl.handle.net/10498/36947
%X The Lower Bajocian/Upper Bajocian transition was analysed in the Casa Chimeneas section (JRi3), Sierra de Ricote (Murcia),
which is located in the Median Subbetic paleogeographic domain. This stratigraphic section, consisting of an alternation of
marls and marly limestones with radiolarians, fnely shelled bivalves, Zoophycos and frequent ammonites, represents the best
stratigraphic sequence of the Subbetic (Betic Range) and, also possibly, of the Mediterranean province (westernmost Tethyan
Realm) to carry out this analysis. Ammonite have been sampled since the 90s increasing the collection available, which,
together with the analysis of calcareous nannofossil assemblages and the carbon-isotope δ13C curve, allows accurately modify
the position of the Lower Bajocian/Upper Bajocian boundary in this stratigraphic reference section. Ammonite assemblages
are dominated by Oppeliinae, Phylloceratoidea and Sphaeroceratidae, but other taxa with more biostratigraphical value
(Stephanoceratinae, Cadomitinae, Frebolditinae, Leptosphinctinae and Parkinsoniidae) are also common. The absence of
the typical Teloceras and the scarcity of Caumonstisphinctes make difcult to recognize the base of the Upper Bajocian. The
appearance of the species Leptosphinctes constrictus, the last records of the genus Paviceras, and the species Masckeites?
af. exilis and Subcollina ochoterenai are the most signifcant bioevents marking this boundary. The frst specimens, but
not frst occurrences, which would be recorded below the oldest studied sample, of the calcareous nannofossils Cyclagelosphaera margerelii and Crepidolithus crassus are identifed in the base of the Blagdeni Subzone, and those of Discorhabdus
ignotus and Ethmorhabdus gallicus within the upper part of the same subzone. The last occurrences (LOs) of Hexalithus
magharensis and Carinolithus superbus are located within the Niortense Zone. Signifcant fuctuations are recorded in the
δ13C curve in the Lower Bajocian/Upper Bajocian transition coinciding with the turnover of ammonites and the increase in
diversity of calcareous nannofossils. Some ammonite taxa with signifcant biostratigraphic value are herein described and
illustrated for the frst time in Sierra de Ricote.

%K Bajocian
%K Betic Cordillera
%K Sierra de Ricote
%K Ammonites
%K Calcareous nannofossils
%K Carbon-isotopes
%K Bajociense
%K Cordillera Bética
%K Sierra de Ricote
%K Ammonites
%K Nanofósiles calcáreos
%K Isótopos de carbono
%~ Universidad de Cádiz