High resolution stable isotope stratigraphy of Langhian marine records from the St. Peter's Pool section (Central Mediterranean, Malta Island)

The Maltese Islands play an important role in extending the stable isotopic stratigraphy of the Mediterranean (Abels et al., 2005;Mourik et al., 2011) back to the early-middle Miocene. In particular, the St. Peter’s Pool section, which outcrops in the Delimara Peninsula (southeastern coast of the Malta island) and belongs to the Upper Globigerina Limestone member (the younges tmember of the Globigerina Limestone formation), presents a continuous and well preserved deep marine record for the Langhian time interval. The 31 meter thick sedimentary record is characterized by cyclic alternations of calcareous marl, marly limestone and jutting bioturbated hardened limestone and lies on the well-known C2 phosphate- rich bed (Pedley et al., 1976). High-resolution oxygen and carbon stable isotope analyses performed on 375 bulk samples in the St. Peter’s Pool section showed higher-frequency oscillations superimposed on the long-term trends. In particular, a major shift in the a18O record (~1.00‰) identified the major step in the Langhian global climate cooling corresponding to the Mi2 event of Miller et al. (1991). At the same time, an increase of 1.2‰ in the a13C record documents the onset of the carbon isotope event CM3a. Biostratigraphic data (Foresi et al., in press) constrain the onset of this cooling event (Mi2 event) between the Last Common Occurrence (LCO) of Helicosphaera ampliaperta and the LCO of Paragloborotalia bella. In addition, it falls in the upper part of the Magneto-Chron C5Cn.1n. This event coincideswith theminimumobliquity amplitudes associatedwith the 1.2-Myr cycle.This orbital configuration mirrors the one that occurred during the younger Mi3b event of Miller et al. (1991), which was identified in the Ras il Pellegrin section (Malta island) by Abels et al. (2005) and Mourik et al. (2011). Furthermore, this isotopic event is comparable to other oxygen isotope enrichment events that occurred during the late Paleogene and the Neogene.