Integrated biostratigraphy and chemostratigraphy of the upper Cenomanian and lower Turonian succession in Puentedey, Iberian Trough, Spain

摘要

In this paper, we present an integrated study of the macrofauna (Cephalopoda), microfauna (Ostracoda and Foraminifera), microflora (Pithonella, Dinoflagellata, Acritarcha and Prasinophyta) and geochemical signals (carbon delta C-13 and oxygen delta O-18 stable isotopes) of the upper Cenomanian and lower Turonian succession in Puentedey, Iberian Trough, Spain. This palaeontological and geochemical study has enabled us to identify numerous species of cephalopods (29), ostracods (19), benthic foraminifers (31), planktonic foraminifers (15), dinoflagellates (63), and acritarchs and prasinophytes (11), and to recognise two positive excursions of the delta C-13 signal related to the OAE2 (in the Metoicoceras geslinianum and the Spathites (Jeanrogericeras) subconciliatus zones, respectively). Variations of these macrofaunal, microfaunal, microfloral and geochemical signals have been interpreted to identify important events of the palaeoenvironmental evolution of the inner platform of the Iberian Trough during the studied interval of the Late Cretaceous. Benthic ecosystems were severely affected by the establishment of the Oceanic Anoxic Event 2 (OAE2) at the end of the late Cenomanian. This event is evidenced by the depletion of calcareous microfauna (benthic calcareous free intervals, BCFI) and the survival of opportunistic microfauna (platycopic ostracods and textulariid foraminifers). The response was different for microflora (dinoflagellates and acritarchs), which were less affected by the anoxic event.