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Abstract
The section of Gorgo a Cerbara in Italy has been proposed as the Global Stratotype Section and Point (GSSP) for the Barremian/Aptian boundary (Lower Cretaceous). This section displays the transition between the white pelagic limestones of the Maiolica Formation (Tithonian–lowermost Aptian) and the polychrome marls of the Marne a Fucoidi Formation (Aptian–Albian). The Oceanic Anoxic Event 1a (OAE 1a) anoxic horizon (Selli Level) is located in the latter formation. Here, we report for the first time a palynostratigraphical assessment of this key section, with a very high resolution in the Selli Level.
Palynomorph groups recorded include acritarchs, microforaminiferal test linings, 58 dinoflagellate cysts, 44 sporomorph taxa, and freshwater fungal and algal bodies. These include such biostratigraphical markers as Rhynchodiniopsis aptiana and Odontochitina operculata among the dinoflagellate cysts and Afropollis cf. jardinus among sporomorphs. Biostratigraphical events recognised allow comparisons with previously studied successions in other similar areas (e.g. Cismon apticore in the Southern Alps, Italy). The distribution of taxa recorded in the Gorgo a Cerbara section is generally consistent with published data, but several differences between the assemblages recorded in the Cismon apticore and in this study were noted.
The best global markers for the Barremian/Aptian boundary are represented by the disappearance of R. aptiana and by the appearance of O. operculata, but in this section these occurred 0.65–1.35 Myr after the magnetostratigraphically defined boundary, within the Selli Level. The angiosperm pollen A. cf. jardinus is recorded only within the Selli Level (from 1.4 to 1.6 Myr after the Barremian/Aptian boundary), consistent with an Early Aptian age. A cluster of 10 extremely short-ranging dinoflagellate cyst excursion taxa appear in this section coincident with the Nannoconid Crisis event and its associated thermal peak, ca. 10–20 kyr before the onset of the OAE 1a. Several short-ranging Pteridophyta spore species are found only within the Selli Level itself.
Acknowledgements
RPS Energy (Woking, UK), and particularly Drs. Janice Weston and Martin Lester are gratefully acknowledged for allowing us to process the samples, and tolerating the use of the office facilities and microscopes for the sample logging. Thanks go to James Riding (British Geological Survey), Paul Dodsworth (Stratasolve Ltd.) and to another, anonymous, reviewer for reviewing a previous version of this manuscript. The authors would also like to express their gratitude to Dave Shaw (Biostratigraphic Associates, UK) and Stefano Torricelli (ENI, Milan, Italy) for providing comments and suggestions.
Disclosure statement
No potential conflict of interest was reported by the authors
Supplemental data
The underlying research material for this article (palynological slides) can be accessed at RPS Energy Woking office, Goldvale House, 27-41 Church Street West, Woking, Surrey, United Kingdom. Supplemental data for this article, including the summary of the palynological events (Table S1) and the occurrence data of each taxon (Table S2), can be accessed here
Additional information
Notes on contributors
Stefania Unida
STEFANIA UNIDA is a palynostratigrapher currently working at RPS Energy, Woking, UK. Her main areas of her expertise lie in the Mesozoic and Cenozoic palynostratigraphy of the Mediterranean, the North Sea and West Africa. Stefania's experience includes single and multi-wells and outcrop studies, integrated multidisciplinary and palaeoenvironmental interpretations. In 2005, Stefania graduated with a BSc in Natural Sciences from the University of Cagliari, Italy, and in 2008 she obtained an MSc from the same institution. In 2011 Stefania completed a PhD on the Miocene palynostratigraphy of the central-western Mediterranean Basin within the multidisciplinary Italian National Research Project (PRIN 2007) in collaboration with Utrecht University, The Netherlands and ENI, Italy.
Stefano Patruno
STEFANO PATRUNO is a geoscientist currently working at PGS, Weybridge, UK. His areas of expertise include sedimentology, stratigraphy, seismic interpretation, hydrocarbon exploration and production. In 2007, Stefano graduated with a BSc in Geology from the University of Chieti, Italy and in 2008 he obtained an MSc in Micropalaeontology from University College London, UK. For his MSc dissertation, Stefano was awarded The Dennis Curry Fund Prize of the Geologists' Association, UK. Subsequently, Stefano completed a PhD at Imperial College London on the sedimentology and seismic stratigraphy of subsurface deltaic sand bodies during 2009–2013. His PhD research was published in several major journals. One of these articles was Earth-Science Reviews 13th most downloaded paper in 2015. In 2014, another paper achieved a special commendation as a part of the Early Career Award from Basin Research.
