Integrated stratigraphy of St. Thomas section (Malta): new preliminary data on a potentially reference section for the Burdigalian GSSP

Over the last few years, the Neogene Period underwent a deep chronostratigraphic revision, and several boundary stratotypes were ratified. Only the GSSPs of the Langhian and Burdigalian have still to be formalized. Recent researches on some Mediterranean sections (Di Stefano et al., 2008, Iaccarino et al., 2011) provided useful results to propose the GSSP of the Langhian Stage, while the Burdigalian GSSP (temporarily placed by Lourens et al. (2004) at 20.43 Ma in correspondence of the Helicosphaera ampliaperta First Occurrence) still represents a completely open problem. According to the ICS suggestions, the Burdigalian GSSP should be located in the Mediterranean area, even though there are very few suitable outcropping successions. We try to solve this problem studying the St. Thomas section, an Aquitanian-Burdigalian succession outcropping on the southern coast of the Malta Island and pertaining to the Middle Globigerina Limestone, the intermediate member of the Globigerina Limestone formation (Chattian-Langhian in age). The St. Thomas Section, is mainly composed of alternating marls and calcareous marls, and was measured (~90 m thick) and sampled (744 samples were collected by a hand-core driller system with a sampling space of ~10 cm) from the basal phosphate rich bed (QCB) up to the highly eroded surface (TMGLOg). Furthermore, some pilot magnetostratigraphic analyses were performed and produced positive results. Nowadays, we can assert that St. Thomas Section is totally comprised within the foraminiferal MMi2 Zone of Iaccarino et al. (2007) and spans the interval MNN2a Zone (upper part)-MNN4a Zone (lowermost part) of Fornaciari and Rio (1996). In terms of magnetostratigraphy it covers the interval between the Magnetochron C6n and the Magnetochron C5Dn. The well exposed outcrops, the lithological cyclicity, the rich and well preserved micropaleontological assemblages and the positive magnetostratigraphic results make this section suitable for high-resolution stratigraphic, cyclostratigraphic and astrochronologic studies. Although the study is still at an early stage, the characteristics of the succession make the St. Thomas section a potential candidate for the Burdigalian GSSP.