Late Quaternary coastal landscape morphology and evolution of the Maltese Islands (Mediterranean Sea) reconstructed from high-resolution seafloor data

Abstract

Abstract:The current strong motivation to explore those traces of the archaeological and prehistoric human heritage that presently lie submerged on the continental shelf requires large-scale and precise underwater mapping. One Mediterranean sector deserving particular attention is the Sicily Channel, which is critical for a better understanding of the Africa-Europe migratory routes and early civilization patterns due to its large expanses of shallow seabed that were partially or totally exposed at times of lower relative sea levels. We have focused our attention on the submerged continental margin of the Maltese archipelago. A detailed bathymetric map is here presented, and is discussed in terms of features interpretable as former subaerial landforms and inundated by sealevel rise following the Last Glacial Maximum lowstand at approximately -130 m. Our datasets combine multibeam surveys, Light Detection And Ranging (LiDAR)-derived digital terrain models (DTMs), Chirp sub-bottom profiler records and bottom samples acquired between 2009 and 2012. The main features identified are former river incisions, alluvial plains, karst landscapes (sinkholes, limestone plateaus), slide deposits and palaeoshorelines. This study provides a detailed topographical reconstruction of the palaeolandscape of this key region that is relevant to any future archaeological exploration of the Maltese offshore area.

Geomorphological mapping of terrestrial and marine areas, northern Malta and Comino (central Mediterranean Sea)

“…The terrestrial valleys continue on the eastern continental shelf with the same orientation to reach and incise the main escarpment located at 75-90 m of depth. They have a sinuous to meandering pattern varying from 100 m to 4 km (Foglini et al, 2016;Micallef et al, 2013); they are filled by fine to medium sand alternating with coarse sand and gravel. The submerged channels are interpreted as relict fluvial valleys: they are the results of fluvial processes that developed during different stages of the sea level fall (Van Heijst & Postma, 2001), when more humid conditions allowed the watercourses to cut the gorges and deposit the sediments.…”

“…Limited block slides and rock fall deposits can also be found along the eastern coast of Comino. The submarine parts of the described landslides, whose state of activity is unknown, were described in Foglini et al (2016) and Soldati, Devoto, Prampolini and Pasuto (in press). Outstanding examples of block slides prolonging on the seafloor are those located at Anchor Bay, along the stretch of coast between Rdum id-Delli and Ras Il-Wahx (the most prominent block slide deposit) and Il-Qarraba (Figure 8(A,B)).…”

“…Sea level changes have greatly influenced Maltese continental shelf geomorphology: its portion shallower than ca. −130 m emerged during the sea level lowstands, which occurred during the last glacial cycle and was modelled by subaerial processes (Foglini et al, 2016;Micallef et al, 2013). This palaeo-landscape was progressively drowned by post-glacial sea level rise and terrestrial palaeo-landforms are still well preserved on the present seafloor ( Figure 1).…”

Geology and archaeology: submerged landscapes of the continental shelf: an introduction

“…They include technological advances in the reconstruction of deeply submerged palaeolandscapes and assessment of their archaeological potential (Cawthra et al 2015;Foglini et al 2015;Sakellariou & Galanidou 2015), detailed predictive modelling of the environmental and archaeological potential of submerged landscapes (Ward et al 2014), the discovery, interpretation and wider significance of underwater archaeological sites (Abelli et al 2014;Nutley et al 2014), detailed analysis of shoreline changes and their human impact combining geological, palaeoenvironmental and archaeological evidence (Ryabchuk et al 2014;Galili et al 2015;Kulkova et al 2015), and the effect of sea-level changes on patterns of human dispersal in key areas (Antonioli et al 2014;Glørstad 2014;Wurster & Bird 2014). Glørstad (2014) describes the peopling of Norway following the retreat of the Scandinavian ice sheet.…”

“…The Maltese archipelago is a prime candidate as a link in a potential pathway between North Africa and southern Europe, and Foglini et al (2015) pursue this theme with extensive underwater mapping of the continental shelf around Malta. Using high-resolution bathymetric mapping methods, such as multibeam surveys, LiDAR-derived digital terrain models (DTMs), chirp-sonar records and bottom sampling, they demonstrate the presence of a variety of subaerial landforms exposed at low sea level, which have undergone relatively little modification by subsequent sea-level rise.…”