Burdigalian-Langhian paleoclimatic reconstruction of Middle and Upper Globigerina Limestone (Malta Island, Central Mediterranean)

The Miocene sediments of the Maltese Archipelago were intensively studied for their geological and stratigraphical meaning, since Malta is considered a bypass area between western and eastern Mediterranean. This feature makes this site suitable for the Early-Middle Miocene paleoclimatic reconstruction. In particular, the St. Thomas (1) and St. Peter’s Pool (2) sections are two well cyclically bedded exposed pelagic successions, referred to the Middle and Upper Globigerina Limestone members, spanning the Burdigalian-Langhian time intervals. They crop out along the cliffs of the Delimara Peninsula in the SE of Malta Island. The St. Thomas and St. Peter’s Pools sections are separated by a phosphate rich bed (C2 bed). The two sections are combined in a ~120 m thick composite section consisting of alternating gray marls and calcareous marls, with marly mega-beds in the middle-upper part. Upwards, the composite section is characterised by yellowish marly limestone, interlayered with typical very hard limestone, pale brown in colour and strongly protruding from the morphological profile. The integrated stratigraphic study (calcareous plankton and magnetostratigraphy) allows us to assign the composite section to the Burdigalian-Langhian time interval (magnetochron interval C6n- C5Br), highlighting a hiatus of ~0.6 My in correspondence of the phosphate rich C2 bed (uppermost Burdigalian). In order to reconstruct the main climatic events occurring in the St. Thomas-St. Peter Pool composite record, a planktonic foraminiferal paleoclimatic curve has been generated using the biogeographic index groups (warm, warm-temperate, cold-temperate and cold species) reported by (3). On this basis, six intervals have been identified: i) Burdigalian cold interval, characterised by three main cold/warm oscillations, occurring in the middle part of Chron C6n (between 7 and 30 meters); ii) Burdigalian warm interval, between 30 and 63 meters, spanning in the uppermost part of Chron C6n to the upper part of Chron C5En, iii) Burdigalian cold interval, between 63 and 75 meters, centred in the middle part of Chron C5Dr. According to magnetostratigraphy of the composite section, this sudden cold event could be correlated to the glaciation Miller event Mi1b; iv) Burdigalian warm interval, between 75 and 90 meters, occurring in the Chron C5Dn; v) Burdigalian/Langhian cold interval, just above the C2 phosphate rich bed, between 90 and 98 meters, spanning from Chron C5Cn.2n? to Chron C5Cn.1n; vi) three main cold/warm oscillations occur within Chron C5Br, characterising the lower part of the Langhian interval (Upper Globigerina Limestone).