Abstract
The Eastern and Western Mediterranean are separated by an elevated plateau that regulates water exchange between these two basins. The Maltese archipelago, situated atop this topographic high, offers a unique window into the evolution of this plateau in the lead up to the Messinian Salinity Crisis. The Upper Coralline Limestone Formation was deposited between the late Tortonian and the early Messinian and was probably terminated by palaeoceanographic events related to the Messinian Salinity Crisis. It represents the youngest Miocene sedimentary deposits outcropping in the Maltese archipelago. This shallow‐water carbonate unit can be used to trace palaeoenvironmental changes atop the sill between the Eastern and Western Mediterranean and to explain the possible water flow restrictions to the Eastern Mediterranean that could have preceded the Messinian Salinity Crisis. Here field surveys, and analysis of the depositional environment within the Upper Coralline Limestone in Malta, are combined with recently acquired multichannel seismic reflection profiles between Malta and Gozo, to reconstruct the depositional sequence in the Malta Plateau during the late Miocene. The Upper Coralline Limestone consists of multiple coralline and larger benthic foraminifera dominated facies, extending from subtidal to intertidal environments. These accumulated in two depositional cycles observed in both outcrop and seismic reflection data. Each cycle exhibits an early aggradation–progradation phase followed by a progradation phase and a final aggradation phase. These manifest themselves in the outcrops as shallowing and deepening upwards phases. These were deposited above a deep water unit and are indicative of a preceding uplift phase followed by filling of the accommodation space through the deposition of the Upper Coralline Limestone Formation in shallow marine depths. The presence of this highly elevated sill during the late Miocene could have restricted circulation to the eastern basin.
Highlights
The Messinian salinity crisis (MSC, 5.97–5.33 Ma) was the result of extreme restriction of the Mediterranean Sea from the Atlantic Ocean (Hsü et al, 1973; Meilijson et al, 2019; Roveri et al, 2014a)
While it is accepted that evaporite deposition was synchronous in both the Western and Eastern Mediterranean (Krijgsman et al, 2002; Meilijson et al, 2018, 2019), an ongoing debate persists on whether the Eastern and Western Mediterranean were restricted to the same degree and at the same times (Blanc, 2000, 2006; Meijer, 2006; Ryan, 2008)
The uplift raised the Maltese Islands to a water depth that allowed the emplacement of a shallow-w ater carbonate unit in the form of the Upper Coralline Limestone (UCL) Formation
Summary
The Messinian salinity crisis (MSC, 5.97–5.33 Ma) was the result of extreme restriction of the Mediterranean Sea from the Atlantic Ocean (Hsü et al, 1973; Meilijson et al, 2019; Roveri et al, 2014a). Microfossil assemblages exhibit indications of periodically enhanced salinity and oxygen limitation (Kontakiotis et al, 2019; Kouwenhoven et al, 2006; Moissette et al, 2018) All of this evidence points to some enhanced restriction of the eastern basin as early as ca 7.5 Ma. A key region controlling the connection between the Eastern and Western Mediterranean is the sill between Sicily in the north and Tunisia in the south. The region is tectonically complex where rifting, transpression and the African/European collision resulted in a highly dynamic configuration throughout the Miocene (Ben-Avraham et al, 1987; Dart et al, 1993; Gardiner et al, 1995) This activity allowed for significant vertical movements, well expressed in the geological record of the Maltese Islands by significant shifts in depositional depth (Pedley, 1978).
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