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Geomorphologic features related to gravitational collapse: submarine landsliding to lateral spreading on a Late Miocene-Quaternary slope (SE Crete, eastern Mediterranean)

Alves, Tiago Marcos and Lourenco, Sergio 2010. Geomorphologic features related to gravitational collapse: submarine landsliding to lateral spreading on a Late Miocene-Quaternary slope (SE Crete, eastern Mediterranean). Geomorphology 123 (1-2) , pp. 13-33. 10.1016/j.geomorph.2010.04.030

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Detailed geological mapping, complemented by sedimentary facies analysis, photomosaics and topographic measurements (height, width) allowed the investigation of the geomorphological features related to the Late Miocene–Quaternary gravitational collapse of a palaeoslope located in SE Crete (eastern Mediterranean). In the study area, carbonate megablocks indicative of submarine landsliding during the Late Miocene alternate with collapse features more typical of subaerial settings; the latter generated after a major event of tectonic uplift initiated in Crete during the Early-mid Pliocene. Submarine features typically show basal shear zones, rather than planes, generated in near-seafloor strata deformed in ductile form during the gravitational collapse of the megablocks. The lithology of failed carbonate strata differs from that of their basal shear surfaces, a characteristic providing a reliable estimate for the degree and styles of basal deformation during submarine slope instability. Styles of submarine collapse include, by order of magnitude; (i) lateral spreading of fractured segments of fan cones and carbonate sheet flows, eventually transported 100s of metres downslope; (ii) aperture of ravines and chasms in gravitationally unstable fan cones and boulder conglomerates; (iii) gliding of megablocks over a ductile basal layer through a distance of up to several kilometres; and (iv) rolling of subcircular blocks, often within a debris-flow matrix in fan cones and deltas, or embedded in slope siliciclastic strata. This work highlights the existence of prominent 2–10 m basal shear zones in strata underneath the larger megablocks deposited on marine slope strata. Basal shear zones comprise a melange of reworked conglomerates and breccia clasts from overlying megablocks, large ripped blocks of rock and faulted near-seafloor strata, at places showing remnant beds and sand injection features. Consequently, the outcrop data show an average 5:1 ratio between the maximum observed thickness of megablocks and the thickness of basal shear zones (R), a value of similar magnitude to published examples from offshore landslides.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Uncontrolled Keywords: Eastern Mediterranean; Submarine landsliding; Basal slip planes; Lateral spreading; Toe thrusting
Publisher: Elsevier
ISSN: 0169-555X
Last Modified: 04 Jun 2017 02:04

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