Niccolo Baldassini

Stratigraphic features of the Maltese Archipelago: a synthesis

The present study gathers a large amount of both existing and unpublished biostratigraphic data, which allows a detailed and complete definition of the stratigraphic features of the late Oligocene–late Miocene Maltese Archipelago sedimentary succession, recording in turn the tectonic and eustatic history of the Central Mediterranean region. We selected five sections in the Malta Island and three in Gozo, representative of the entire sedimentary succession, affected by well-known erosional surfaces, correlated to low-stands of the sea level, often associated with phoshatic layers, linked to the subsequent high-stands. The sedimentary interval, and thus the associated hiatuses, was constrained both by the bio-chronostratigraphic attribution and by the comparison with the third-order succession of the New Jersey passive margin, which shows strict analogy with the geodynamic context in which the Maltese succession deposited. The diachroneity at the base of the formations in the different sections, and the presence of intraformational unconformity/hiatuses, highlighted the role of the tectonic, which depicted a complex sedimentary basin, characterized by more distal versus more marginal sectors. Furthermore, the possibility to compare the sedimentary succession with the oxygen isotope curve connects the sedimentation interruptions, recorded within the Maltese Archipelago deposits, to global cooling events.

New insights on the Oligo-Miocene succession bearing phosphatic layers of the Maltese Archipelago

The Maltese Archipelago sedimentary succession is nowadays very well studied and known, mostly due to the excellent exposures of the outcrops, the well-preserved calcareous microfossil content, and the cyclic lithological pattern of most of the stratigraphic intervals. Therefore, the Maltese sediments have been studied to establish updated calcareous plankton biostratigraphic schemes, and the Ras il Pellegrin section, along the western coast of Malta Island, has been chosen to host the Global Stratigraphic Section and Point of the Serravallian Stage. This paper focuses on the Maltese Oligo-Miocene succession bearing well-developed phosphatic beds, with particular attention to the evaluation of the associated sedimentary hiatuses. To achieve this goal, the calcareous nannofossils content of the marine sediments inter-bedded to the phosphatic horizons has been analysed in two key sections: Il Blata (W of the Malta Island) and Qammieh (N of the Malta Island). Furthermore, the good correspondence of the examined succession with the third-order sequences of the New Jersey passive margin, allowed a more refined definition of the intervals characterized by absence of normal marine sedimentation. Dissimilarities in the number of the phosphatic horizons characterizing the two sections have been explained supposing different locations of the two depositional areas within the sedimentary basin, probably affected by local syn-sedimentary tectonic activity. Finally, the correlation of the two investigated successions with the stable Oxygen isotope curve provided relationships between the origin of the phosphatic layers and global sea-level changes.