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Canyon and landslide processes of non-tropical carbonate escarpments

Final Report Summary - SCARP (Canyon and landslide processes of non-tropical carbonate escarpments.)

Despite forming some of the most impressive landforms on Earth, carbonate escarpments are poorly understood features, and the few studies available have mainly been carried out in tropical settings. SCARP is a project that integrates diverse geophysical and sedimentological datasets acquired from the Mediterranean Sea, and analyses them with innovative and state-of-the-art analytical and laboratory techniques. The key outcomes of SCARP include the following:

(i) The outer shelf of a carbonate escarpment is directly influenced by escarpment-forming processes. In the case of the Malta Escarpment, the key seafloor processes include mass movements triggered by seismicity and loss of support, horst and graben formation associated to strike-slip deformation, and erosion/deposition by bottom current flow.
(ii) The Malta Escarpment geomorphology indicates that the eastern Mediterranean Basin experienced a drawdown of 2500 m during the Messinian salinity crisis, which enabled formation of canyons by subaerial fluvial erosion prior to the deposition of the Messinian evaporites. Post-Messinian geomorphic activity entailed limited canyon erosion by submarine gravity flows, tectonic activity associated to extensional and strike-slip kinematics in the southern part of the Malta Escarpment, deposition by bottom currents, and widespread but small-scale slope failures in Plio-Pleistocene sediments.
(iii) An extensive, buried and chaotic sedimentary body at the base of the Malta Escarpment is consistent with the passage of a megaflood from the western to the eastern Mediterranean Sea via a south-eastern Sicilian gateway during the Messinian salinity crisis. This supports the scenario of a Mediterranean-wide catastrophic Zanclean flood and suggest that the identified sedimentary body is the largest megaflood deposit on Earth.
(iv) A synthesis of the knowledge on the stratigraphy, morphology and formation processes of the Blake, Campeche, Florida and Malta Escarpments reveals that, at fine-scale, escarpments are generally characterised by three distinctive landforms – canyons (2 types), landslide scars (3 types) and deposits, and terraces. Gravity flows and fluid seepage are thought to mechanically erode and dissolve escarpment canyons. Loss of support, associated with canyon erosion and escarpment steepening, is responsible for retrogressive submarine landsliding. Lithologic differences and their enhancement by erosional processes are important for terrace development. Structural processes, and mechanical abrasion and carbonate dissolution by bottom currents, only explain escarpment morphology locally.

The outcomes of the SCARP project have been disseminated via 28 publications, 28 conference communications, and numerous outreach activities (interviews, exhibits, public talks, school visits, geological walks, project website).

During SCARP, Dr Micallef has been promoted to associate professor and awarded a European Research Council Starting grant, which have allowed him to set up a new research group. The fellow has initiated collaborations with institutions from 10 different countries, which have provided him with access to research vessels and seafloor surveying infrastructures, seafloor data, software and expertise not available in Malta. During the past 4 years, the fellow has delivered lectures in MSc and undergraduate degrees offered by the Departments of Geosciences and Physics, and he has contributed to the development of a new BSc degree in Geosciences. He has also organised training courses in Malta and Brazil.