[1] The extents of volcanic island shelves result from surf erosion, which enlarges them, and volcanic progradation, which reduces them. However, mass-wasting, tectonics and sediment deposition also contribute to their morphology. In order to assess the relative significance of these various processes, we have mapped in detail Faial Island's shelf in the Azores archipelago based on interpretation of geophysical and geological data. The nearshore substrates of the island, down to 30-50 m depth, are rocky and covered by volcaniclastic boulder deposits formed by surf action on now-submerged lava flows. Below those depths, sandy and gravel volcaniclastic beds dominate, building clinoforms up to the shelf edge. In some sectors of the coast, Copyright 2012 by the American Geophysical Union 1 of 30 prograding lava has narrowed the shelf, but, in contrast to nearby Pico Island, we find fewer submarineemplaced lavas on the shelf. In this island, we interpret the distance between the coastline and the shelf edge as almost entirely a result of a straightforward competition between surf erosion and lava progradation, in which erosion dominates. Therefore shelf width can be used as a proxy for coastline age as well as for wave energy exposure. The stratigraphy of shelf deposits in boomer seismic data is examined in detail to assess the roles of different sediment sources, accommodation space and wave exposure in creating these deposits. We also show evidence of mass-wasting at the shelf edge and discuss the possible origins of slope instability. Finally, we discuss the contributing role of tectonics for the development of the shelf.

Traditionally, the study of coastal evolution has focused on emergent barriers or stratigraphic sequences on the adjacent shelf, but seldom are these two systems studied holistically or the information combined into a single model. Here, we combine data sets from the emerged and submerged sectors of a prograding coast, from the coastal dune to the innermost continental shelf, to reconstruct the long-term history of shelf reworking and spit elongation of Tr oia Peninsula in Portugal. This analysis involves synthesizing high-resolution reflection seismic profiles from the shoreface, Ground Penetrating Radar images from the emerged sand barrier, high resolution digital terrain models, and Optically Stimulated Luminescence and radiocarbon dating of sediment samples from the emergent sand barrier and backbarrier. The results document the growth of the sandy peninsula in five major phases of progradation represented by massive foredunes separated by hiatuses of sedimentation and periods of shoreline stability. Formation of the peninsula began circa 6,500 years ago by spit elongation from the south as documented by the oldest beach sediments within the spit. The spit enlarged until a tidal inlet was formed around 3,300 years ago, which caused the construction of the ebb-tidal delta. The latter sequestrated the sand supplied to the spit inhibiting spit progradation until the ebb delta reached an equilibrium volume, allowing shoreline

This paper synthesizes the geology of the Atlantic Margin off the coast of Iberia and surrounding Abyssal Plains using published thematic mapping freely downloadable from EMODNET-Geology portal at different scales. Selected information was chosen in order to highlight mineral occurrences and natural hazards overlaid on geological and morphological maps. Altogether, this information is published and interpreted here for the first time; nevertheless this exercise can be carried out by anyone interested and allows different visualizations of geological objects. Cross-correlations of geological objects and processes can easily arise. Because all of the information (each piece of data and metadata) in the EMODNET-Geology portal has bibliographic references associated, readers are able to find the original source of information. It is shown that clicking in and out of layers of information (that cannot be found all together in a single scientific paper) allows quick cross-correlation using the EMODNET Geology thematic portal. This allows a free, versatile and quick way of cross-correlating geological objects and processes in vast marine areas and their comparison with onshore geology.

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