The St. Peter’s Pool section (Malta Island): progress towards the Langhian GSSP

The main goal of the project “In search of the Global Stratotype Section and Point of the Langhian Stage and paleoceanographic implication” granted by the Italian Ministry of University and Research and supported by the Subcommision on Neogene Stratigraphy, was to find a potential candidate for hosting the Langhian GSSP. In the framework of the project several sections were investigated and among the others the St. Peter’s Pool one (Foresi et al., 2011), spectacularly outcropping in the Delimara Peninsula, SE of the Malta Island. This section was studied through high-resolution bio-magnetostratigraphy, which resulted in a remarkable improvement of the Mediterranean Langhian knowledge. Calcareous plankton quantitative analyses allowed the definition of several bioevents with a great potential for biostratigraphic correlations. To the well-known bio-horizons, such as the Helicosphera ampliaperta Last Common Occurrence (LCO), the Sphenolithus heteromorphus Paracme and the Paragloborotalia siakensis Acme, many others were added, such as the Paragloborotalia bella LCO and a new P. siakensis Acme, documented for the first time in the Mediterranean area. The following aspects play in favor of the St. Peter’s Pool section as a candidate for hosting the Langhian GSSP: • the excellent exposure and the easy accessibility; • the well-preserved and abundant content of calcareous plankton and the high number of significant bioevents. Two of these can be selected for approximating the Langhian GSSP, namely the LCOs of the nannofossil H. ampliaperta and of the planktonic foraminifer Paragloborotalia bella, both falling in the Chron C5Cn.1n. Particularly the LCO of H. ampliaperta represents a well-defined horizon, also recognizable in extra Mediterranean areas, and its choice could represents a good compromise between thee two recommended events for the definition of the Langhian GSSP (the Praeorbulina datum and the C5Cn/C5Br reversal); • the stratigraphic continuity with the section yielding the Serravallian GSSP (Ras il-Pellegrin in Malta Island); • the cyclic pattern of the succession. On the other hand the magnetostratigraphic data show some uncertainties. Yet, the cyclostratigraphic reconstruction, which is the subject of ongoing studies, has a high potential for establishing a reliable astronomical tuning of the section, providing a further positive element for proposing it as a candidate for the Langhian GSSP. The study will be completed by Oxygen and Carbon isotopes analyses to individuate global paleoclimatic changes.