Data for: Oxfordian carbon-isotope stratigraphy and pelagic biofacies of the Middle–Upper Jurassic transition in the Tethys–Central Atlantic connection

A bulk carbon-isotope stratigraphy, based on high-resolution sampling of five stratigraphic ammonite-dated sections
from pelagic swells of the Subbetic basin (External Zones of the Betic Cordillera, southern Spain) is presented. The
studied sections are characterized by Callovian‒Oxfordian stratigraphic successions located in the South Iberian
palaeomargin, a key area connecting the Central Atlantic to the Tethys oceans. The rocks are mainly nodular
limestones with common extreme condensation (rosso ammonitico facies). Discontinuities with hiatuses of variable
duration, submarine “hardgrounds”, Fe-Mn ooids, limonite crusts, and neptunian dykes are observed around the
Callovian/Oxfordian boundary. The stratigraphic record, although very time-averaged, allows for a consistent and
accurate ammonite chronostratigraphy. The carbon isotopes of marine carbonates show a marked trend towards high
δ13C values from Lower Oxfordian to the Middle Oxfordian (~4.3 ‰, near the Plicatilis/Transversarium boundary). The
isotopic values stand between 2.7–3.0 ‰ at the Upper Oxfordian (Bifurcatus and Hypselum Zones) and lowermost
Kimmeridgian (Bimammatum Zone); afterward δ13C values decrease and reach a relative minimum (~2.3–2.5 ‰) in
the Lower Kimmeridgian (Bimammatum/Planula boundary). Finally, isotopic values increase again (~2.6–2.7 ‰) in the
lower Kimmeridgian (mid part of the Planula Zone). Comparison of carbon-isotope stratigraphy between Subbetic and
other Tethyan areas shows similar trends. The replacement of thin-shelled bivalves by planktonic foraminifers and
radiolarians that took place in the Callovian/Oxfordian boundary can be associated to the widening of the trans-
Pangaean seaway . This, in turn, triggered the global warming which increased nutrients concentration in upper water
column due to intensified nutrient input by river plumes. These phenomena are concomitant with the major Oxfordian
δ13C positive excursion and with a transgressive cycle.