Subaerial and submarine geomorphology and links between onshore and offshore erosion in teh Ionian Sea, Italy

UoM administered thesis: Phd

  • Authors:
  • Rajasmita Goswami

Abstract

This thesis focuses on the northern Ionian Sea and the bordering coastlines of NESicily and SW Calabria. The area provides opportunities to investigate the link betweenonshore erosion and offshore morphology, in an area of varying tectonic, climatic andeustatic conditions. Shelves are very narrow here (<1 km) so they allow straightforwardconnections between the rivers and adjacent submarine channels.Channel morphometric analyses revealed that the dominant control upon theirdiffering characteristics is tectonics. Range-parallel normal faults cause a variation inbedrock erodibility across the range, ultimately affecting the channel steepness, concavityand width. The majority of landslides in Sicily occur in the footwalls of these faults, whereslope instability is exacerbated by faulting, fracturing or jointing. Conversely, in Calabria,due to there being fewer faults, landslides are restricted to steep valley walls, and areabsent from interfluves. The frequency-area power-law exponents (1.99 in Sicily and 1.94in Calabria) fall within the range of values observed (2.0 ± 0.5) in similar landscapes.Onshore erosion is quantified by a variety of methods namely: long-term sediment fluxfrom Pleistocene uplift rates, decadal sediment flux from landslides; published recentsediment yields determined using the Gavrilovic Method and published long-termexhumation rates from 10Be cosmogenic nuclide concentrations.This study prepared the first geomorphology map of the northern Ionian Basin.Comparison with the results of the on-shore geomorphological analysis suggests thatsediment flux offers a first-order control on the offshore morphology, dominated by slopecanyonand gully systems feeding the axial Messina Channel. Submarine channelsassociated with rivers delivering larger sediment flux are characterised by broad channels,shallow gradient and concave-upward longitudinal profiles. Conversely, submarinechannel that lie offshore small-flux rivers have straight longitudinal profiles, low relief andare steep. As the low-flux areas have smaller tectonic uplift rates, their offshore steepnesscontrasts with the tectonic control upon subaerial morphology, where steeper channelstend to occur in high-uplift rate areas. In addition, slump and slide scars are common atthe outer-bends of the Messina Channel and on the Calabrian slope where crossed byfaults. In Calabria, where the landscape is transient, tectonics appears to overshadow allother influences.

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Original languageEnglish
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Award date1 Aug 2012

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