Bio-chemostratigraphy of the Barremian-Aptian shallow-water carbonates of the southern Apennines (Italy): pinpointing the OAE1a in a Tethyan carbonate platform

Abstract

Abstract. Low biostratigraphic resolution and lack of chronostratigraphic calibration hinder precise correlations between platform carbonates and coeval deep-water successions. These are the main obstacle when studying the record of Mesozoic oceanic anoxic events in carbonate platforms. In this paper carbon and strontium isotope stratigraphy are used to produce the first chronostratigraphic calibration of the Barremian-Aptian biostratigraphy of the Apenninic carbonate platform of southern Italy. According to this calibration, the segment of decreasing δ 13 C values, leading to the negative peak that is generally taken as the onset of the Selli event, starts a few metres above the last occurrence of Palorbitolina lenticularis and Voloshinoides murgensis. The following rise of δ 13 C values, corresponding to the interval of enhanced accumulation of organic matter in deep-water sections, ends just below the first acme of Salpingoporella dinarica, which roughly corresponds to the segment of peak δ 13 C values. The whole carbon isotope excursion associated with the oceanic anoxic event 1a is bracketed in the Apenninic carbonate platform between the last occurrence of Voloshinoides murgensis and the "Orbitolina level", characterized by the association of Mesorbitolina parva and Mesorbitolina texana. Since these bioevents have been widely recognized beyond the Apenninic platform, the calibration presented in this paper can be used to pinpoint the interval corresponding to the Early Aptian oceanic anoxic event in other carbonate platforms of central and southern Tethys. This calibration will be particularly useful to interpret the record of the Selli event in carbonate platform sections for which a reliable carbon isotope stratigraphy is not available.

Lithium-isotope evidence for enhanced silicate weathering during OAE 1a (Early Aptian Selli event)

“…The carbon-isotope data from Monte Raggeto is taken from Di Lucia et al (2012) and the stratigraphic position of the OAE 1a record follows Amodio et al (2013Amodio et al ( , 2003, D'Argenio et al (2011D'Argenio et al ( , 43 2004), Di Lucia et al (2012) and Wissler et al (2004), based on carbon-isotope, sequence, magneto-and cyclostratigraphic investigations. Carbon isotopes of the Coppitella section are taken from Luciani et al (2001), who identified the record of OAE 1a by integrated bio-and carbon-isotope stratigraphy.…”

“…The Coppitella section has been analysed by Luciani et al (2001) for bio-and carbon-isotope stratigraphy identifying the record of OAE 1a. Wissler et al (2004) and Di Lucia et al (2012) studied the Monte Raggeto section and identified the typical carbon-isotope signature of OAE 1a. This interpretation is supported by magneto-, sequence and cyclostratigraphic investigations (Amodio et al, 2013(Amodio et al, , 2003D'Argenio et al, 2011D'Argenio et al, , 2004Wissler et al, 2004).…”

“…The other three sections, Monte Raggeto, Santa Maria 4 core and Coppitella, are situated in southern Italy (part of the Apennines) and were formerly positioned in the central Tethyan realm. The Monte Raggeto section is representative of the inner part of the Apennine Carbonate Platform and is mainly composed of well-cemented ostracodal mudstones, peloidal and algal-foraminiferal wackestone-packstones and subordinate requienid-ostreid floatstones (Amodio et al, 2003;D'Argenio et al, 2004;Di Lucia et al, 2012;Wissler et al, 2004). The sediments of the Santa Maria 4 core were deposited in the inner part of the Apulian Carbonate Platform and are characterized principally by well-cemented cyanobacterial laminites, ostracodal mudstones, foraminiferal-algal wackestone-packstones and orbitolinid-sponge packstones to floatstones, (Amodio et al, 2013(Amodio et al, , 2003D'Argenio et al, 2011).…”

“…The carbon-isotope curve of Resolution Guyot, with suggested stratigraphy based partly on strontium isotopes, has been taken from Jenkyns & Wilson (1999) with data from and ; the Monte Raggeto carbon-isotope curve is taken from Di Lucia et al (2012); and the carbon-isotope and biostratigraphy of the Coppitella section is from Luciani et al (2001). The Santa Maria 4 core has been specifically analysed for carbon-isotope ratios in this study, although the record is not unequivocal.…”

Environmental consequences of Ontong Java Plateau and Kerguelen Plateau volcanism

“…These proxies imply a likely major volcanic phase of the GOJE that introduced CO 2 concentrations 3-6 times higher than before (e.g., Erba and Tremolada, 2004) and added biolimiting and/or toxic metals. The nannoconid crisis and the contemporaneous demise of carbonate platforms suggest that acidifi cation in addition to eutrophication of surface waters contributed to a major biocalcifi cation failure, although low-latitude carbonate platforms were less affected (Di Lucia et al, 2012), perhaps because of the kettle effect in near-tropical settings, compensating the impact of elevated atmospheric CO 2 concentrations (Skelton and Gili, 2012).…”