Abstract
AbstractUnderstanding continental‐slope morphological evolution is essential for predicting basin deposition. However, separating the imprints and chronology of different seafloor shaping processes is difficult. This study explores the utility of bathymetric spectral decomposition for separating and characterizing the variety of interleaved seafloor imprints of mass wasting, and clarifying their role in the morphological evolution of the southeastern Mediterranean Sea passive‐margin slope. Bathymetric spectral decomposition, integrated with interpretation of seismic profiles, highlights the long‐term shape of the slope and separates the observed mass transport elements into several genetic groups: (1) a series of ~25 km wide, now‐buried slide scars and lobes; (2) slope‐parallel bathymetric scarps representing shallow faults; (3) slope‐perpendicular, open slope slide scars; (4) bathymetric roughness representing debris lobes; (5) slope‐confined gullies. Our results provide a multi‐scale view of the interplay between sediment transport, mass transport and shallow faulting in the evolution of the slope morphology. The base of the slope and focused disturbances are controlled by ~1 km deep salt retreat, and mimic the Messinian base of slope. The top of the open‐slope is delimited by faults, accommodating internal collapse of the margin. The now‐buried slides were slope‐confined and presumably cohesive, and mostly nucleated along the upper‐slope faults. Sediment accumulations, infilling the now‐buried scars, generated more recent open‐slope slides. These latter slides transported ~10 km3 of sediments, depositing a significant fraction (~3 m in average) of the sediments along the base of the studied slope during the past < 50 ka. South to north decrease in the volume of the open‐slope slides highlight their role in counterbalancing the northwards diminishing sediment supply and helping to maintain a long‐term steady‐state bathymetric profile. The latest phase slope‐confined gullies were presumably created by channelling of bottom currents into slide‐scar depressions, possibly establishing incipient canyon headword erosion.
Highlights
Characterization of the continental slope physiography, and its changes in time and space, is important for understanding and modelling the development of depositional systems on the slope and adjacent basin, and for predicting potential reservoir settings (e.g., Prather, O’Byrne, Pirmez, & Sylvester, 2017; Ross, Watts, & May, 1995)
These, in turn, are interpreted by us below to reflect the activity of several distinct mass transport complex (MTC) systems, their controlling mechanisms and their role in shaping the continental margin
Three types of recent mass transport processes have sequentially shaped the current bathymetry of the continental slope on a sub-regional scale: 1. Broad scale (~104 m spectral component) relatively cohesive slides originated at shelf edge faults and deposited the sediments within narrowly confined lobes at the base of the slope
Summary
Characterization of the continental slope physiography, and its changes in time and space, is important for understanding and modelling the development of depositional systems on the slope and adjacent basin, and for predicting potential reservoir settings (e.g., Prather, O’Byrne, Pirmez, & Sylvester, 2017; Ross, Watts, & May, 1995). Different classification schemes were proposed to characterize shelf-to-basin profile types and their corresponding characteristic shaping processes and depositional patterns (Adams & Schlager, 2000; Brothers et al, 2013; Mosher et al, 2017; Pyles, Syvitski, & Slatt, 2011; Ross et al, 1995). The present day morphology of the slope represents the cumulative imprint of the past activity of variable shaping processes over different temporal and spatial scales, which are not readily identified through bathymetric analysis (e.g., Brothers et al, 2013). Bathymetric spectral decomposition is introduced here to delineate the inventory of interleaved mass wasting features, on the present-day bathymetry of the slope, based on the spatial scale-dependence of their imprints
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