HR: 17:30h
AN: T22E-07    [PDF]
TI: Tracking tectonism with terraces: new methods, new insights in the Gulf of Evvia, central Greece
AU: * Dewez, T J
EM: t.dewez@brgm.fr
AF: Land Management and Natural Hazard (ARN), BRGM, Orleans, 45000 France
AU: Stewart, I S
EM: istewart@geog.gla.ac.uk
AF: Department of Geography and Geomatics: Centre for Geosciences, University of Glasgow, Glasgow, G12 8QQ United Kingdom
AU: Moore, J M
EM: john.moore@brunel.ac.uk
AF: Department of Geography and Earth Sciences,, Brunel University,, Uxbridge, UB8 3PH United Kingdom
AB: Coastal terraces are typically the preferred geomorphic marker to calibrate crustal deformation along tectonically active coastlines. Their elevation with respect to a horizontal reference datum - typically sea level - provides a measure of net uplift (or subsidence), whilst their dislocation or tilting can constrain the 3-D deformation field. Such tectonic interpretations, however, rest on the reliable identification, characterisation and measurement of the terraces themselves. To aid extraction of the topographic attributes of terraces from DEMs, we have developed an algorithm that rapidly and consistently delimits the spatial extent of terrace surfaces based on user-defined individual 'seed points'. The extracted topographic attributes can then be manipulated by standard structural geological 3-D visualisation techniques to inform tectonic analyses. We illustrate the methodology with a case study from the northern Gulf of Evvia, Greece. Here, on the Arkitsa headland of the gulf's western shore, a staircase set of topographic benches are carved into the uplifted tip of a major active normal fault, the Kamena Vourla fault. In the field the benches are observed to be multiple unconformable wave-cut platforms, though individual surfaces are locally faulted in places. A 10 x 10m DEM of the headland, extracted photogrammetrically from scanned air-photos, served as the testbed for the terrace delimitation algorithm. The algorithm computed a terrace map which, when combined with the digital topography, defined the altitude, slope and aspect data for each terrace fragment. The data indicate that the terrace fragments conform to two discrete populations that locate either side of a largely ignored transverse lineament, the Livanates fault. Structural reconstruction of pre-deformation terrace geometries track the differential uplift and tilting of terraces across the Livanates fault. Our tectonic interpretation proposes that this fault is an important 'release' structure to the main Kamena Vourla fault, and that this release fault has been operating at most since the penultimate interglacial period.
DE: 1824 Geomorphology (1625)
DE: 8010 Fractures and faults
DE: 8107 Continental neotectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting