Federica Foglini

Bathymetry of the Adriatic Sea: The legacy of the last eustatic cycle and the impact of modern sediment dispersal

The Istituto di Scienze Marine (ISMAR-CNR) has conducted several research projects on the Italian side of the Adriatic Sea over more than 15 years, collecting bathymetric, geophysical and sediment core data to perform multidisciplinary studies of modern sediment dynamics and of past environmental changes during the last eustatic cycle. A crucial step in this direction was the construction of a detailed bathymetry, a time-consuming task due to the extensive shallow water portion of the basin. Given the setting of the Adriatic Sea and the long-lasting research effort, the bathymetric map is necessarily based on heterogeneous data with uneven spatial distribution of Single-Beam echo-soundings. The main objective of this work is to illustrate the methodology applied to compile the bathymetric map of the west side of the Adriatic Sea at basin scale (1:750,000) and to describe the main morphological units that characterise the seafloor and reflect its main geological features. This bathymetry can also be used in oceanographic modelling both at regional and local scale, focussing on the interaction between bottom currents and seafloor morphology.

DROWNED KARST LANDSCAPE OFFSHORE THE APULIAN MARGIN (SOUTHERN ADRIATIC SEA, ITALY)

The south Adriatic shelf offshore of the predominently carbonate Apulian coast is characterized by a peculiar rough topography interpreted as relic karst formed at a time of lower sea level. The study area covers a surface of about 220 km, with depths ranging from 50 to 105 m. The most relevant and diagnostic features are circular depressions a few tens to 150 m in diameter and 0.50 to 20 m deep thought to be dolines at various stages of evolution. The major doline, Oyster Pit, has its top at about 50 m water depth and is 20 m deep. It is partly filled with sediments redeposited by episodic mass failure from the doline’s flank. Bedrock samples from the study area document that Plio-Pleistocene calcarenites, tentatively correlated with the Calcarenite di Gravina Fm, are a prime candidate for the carbonate rocks involved in the karstification, although the presence of other units, such as the Peschici or Maiolica Fms, is not excluded. The area containing this subaerial karst landscape was submerged about 12,500 years ago as a result of the postglacial transgression over the continental shelf.

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

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 sea-level 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)

ABSTRACT This paper presents an integrated geomorphological map of terrestrial and marine areas of northern Malta and Comino (central Mediterranean Sea) at 1:25,000 scale. The map is the result of terrestrial and marine analyses of different types of data such as aerial photos, digital terrain model of the seafloor and its acoustic backscatter image. The research is intended to emphasise the relationships and continuity of geomorphological features of both the land- and sea-scape, and outline their evolution. The map highlights the occurrence of fluvial, karst and gravity-induced landforms both on land and on the seafloor, such as palaeo-fluvial channels, sinkholes and landslides, which were shaped during sea level lowstands of the last glacial cycle.

Mass Transport Complexes from Contourite and Shelf-Edge Deposits Along the South-Western Adriatic Margin (Italy)

Seismic data and multi-beam bathymetry reveal the occurrence of several exposed or shallowly buried Mass Transport Complexes (MTCs) in the South-Western Adriatic margin (SWAM), which represents the outer sector of the Albanides-Dinarides foreland basin. MTCs are spatially diffused along the SWAM and characterized by high variability in size, morphology and internal geometry. MTCs are derived from the mobilisation of both contourite drift deposits and shelf-margin progradational deposits. The most prominent MTC of the SWAM is the Gondola Slide (GS), a large, deep-seated (∼250 m) MTC located near the Gondola-Dauno fault zone (GDFZ), involving around 30 km3 of shelf and slope sediments. In the northern sector of the margin, the Vieste Slide (VS) affects a low gradient upper slope sector, which is extensively dominated by contourite drifts and sediment waves. Seismic correlation shows that the first and main failure events of GS and VS were contemporaneous and impacted the entire margin (more than 2,000 km2), and probably were trigger by large earthquake, while later events in both GS and VS appear more localised and asynchronous indicating, probably, slope readjustments governed by local stratigraphic factors.

High resolution multibeam and hydrodynamic datasets of tidal channels and inlets of the Venice Lagoon

Tidal channels are crucial for the functioning of wetlands, though their morphological properties, which are relevant for seafloor habitats and flow, have been understudied so far. Here, we release a dataset composed of Digital Terrain Models (DTMs) extracted from a total of 2,500 linear kilometres of high-resolution multibeam echosounder (MBES) data collected in 2013 covering the entire network of tidal channels and inlets of the Venice Lagoon, Italy. The dataset comprises also the backscatter (BS) data, which reflect the acoustic properties of the seafloor, and the tidal current fields simulated by means of a high-resolution three-dimensional unstructured hydrodynamic model. The DTMs and the current fields help define how morphological and benthic properties of tidal channels are affected by the action of currents. These data are of potential broad interest not only to geomorphologists, oceanographers and ecologists studying the morphology, hydrodynamics, sediment transport and benthic habitats of tidal environments, but also to coastal engineers and stakeholders for cost-effective monitoring and sustainable management of this peculiar shallow coastal system.

INTEGRATED GEOMORPHOLOGICAL MAPPING OF THE EMERGED AND SUBMERGED NORTHERN AREA OF MALTA

Terrestrial and marine datasets referring to northe rn Malta (central Mediterranean Sea) have been collected and coupled in the frame of an inter national project funded by the EUR-OPA Major Hazards Agreement of the Council of Europe. O ne of the main outputs of the project is an integrated geomorphological map of the land and seascape of coastal areas of the northern sector of Malta. Existing geomorphological maps pro duced within the same project were used as a base for the mapping of the terrestrial areas. As regards submerged areas, several multibeam suveys were carried out offshore the east ern coasts of the archipelago and offshore the north-western coast of Malta to acquire high re solution bathymetry and backscatter data; a LiDAR-derived DEM of the northern area of Malta was used to cover the white zone between the bathymetric survey and the coastline. This larg e dataset allowed seafloor morphological features to be mapped and recognized by means of ba thymetric analysis and geomorphological interpretation. The seafloor sedim ents were analysed through grab samples collected offshore the eastern coasts of Malta and through the analysis of the acoustic textures characterising the seafloor backscatter imagery (Te xAn implemented by the University of Bath, UK) to produce a sediment distribution map. T he submerged geology was inferred by drawing geological sections based on the Geological Map of the Maltese Islands – Sheet 1 Malta. By exploiting all these data, an integrated g omorphological map of the northern area of Malta (from Marfa Ridge to the Great Fault) and the surrounding seafloors have been produced. The map clearly shows the differences cha ra terising the eastern and the western sides of the island. On the western side, the main features are related to gravity-induced processes responsible for the occurrence of differe nt types of coastal landslides prolonging under the sea level and making up the main landform s of the narrow continental shelf. On the eastern side of the island, the main features are r elated to fluvial and marine processes. Actually, the continental shelf is clearly cut thro ugh by a drainage network that is likely to have developed during sea level lowstands of the La st Glacial Maximum, when the sea level was about 130 m lower than at present.