RT journal article
T1 The lower/upper Bajocian boundary (Middle Jurassic) in the Casa Chimeneas section: Sierra de Ricote (Murcia Region), southern Spain
A1 Sandoval, J.
A1 Aguado, R.
A1 Fraguas, A.
A1 O'Dogherty Luy, Luis Carlos
A2 Ciencias de la Tierra
K1 Bajocian
K1 Betic Cordillera
K1 Sierra de Ricote
K1 Ammonites
K1 Calcareous nannofossils
K1 Carbon-isotopes
K1 Bajociense
K1 Cordillera Bética
K1 Sierra de Ricote
K1 Ammonites
K1 Nanofósiles calcáreos
K1 Isótopos de carbono
AB 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 ofmarls and marly limestones with radiolarians, fnely shelled bivalves, Zoophycos and frequent ammonites, represents the beststratigraphic sequence of the Subbetic (Betic Range) and, also possibly, of the Mediterranean province (westernmost TethyanRealm) 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 modifythe position of the Lower Bajocian/Upper Bajocian boundary in this stratigraphic reference section. Ammonite assemblagesare dominated by Oppeliinae, Phylloceratoidea and Sphaeroceratidae, but other taxa with more biostratigraphical value(Stephanoceratinae, Cadomitinae, Frebolditinae, Leptosphinctinae and Parkinsoniidae) are also common. The absence ofthe typical Teloceras and the scarcity of Caumonstisphinctes make difcult to recognize the base of the Upper Bajocian. Theappearance 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, butnot 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 Discorhabdusignotus and Ethmorhabdus gallicus within the upper part of the same subzone. The last occurrences (LOs) of Hexalithusmagharensis and Carinolithus superbus are located within the Niortense Zone. Signifcant fuctuations are recorded in theδ13C curve in the Lower Bajocian/Upper Bajocian transition coinciding with the turnover of ammonites and the increase indiversity of calcareous nannofossils. Some ammonite taxa with signifcant biostratigraphic value are herein described andillustrated for the frst time in Sierra de Ricote.
PB Springer Nature
YR 2025
FD 2025-03-04
LK http://hdl.handle.net/10498/36947
UL http://hdl.handle.net/10498/36947
LA eng
DS Repositorio Institucional de la Universidad de Cádiz
RD 10-may-2026