Abstract
We present the results of an integrated geomorphological and seismo-stratigraphic study based on high resolution marine data acquired in the north-western Sicilian continental margin. We document for the first time five contourite drifts (marked as EM1a, EM2b, EM2, EM3a, and EM3b), located in the continental slope at depths between ca. 400 and 1500 m. EM1a,b have been interpreted as elongated mounded drifts. EM1a,b are ca. 3 km long, 1.3 km wide, and have a maximum thickness of 36 m in their center that thins northwards, while EM1b is smaller with a thickness up to 24 m. They are internally characterized by mounded seismic packages dominated by continuous and parallel reflectors. EM2 is located in the upper slope at a depth of ca. 1470 m, and it is ca. 9.3 km long, more than 3.9 km wide, and has a maximum thickness of ca. 65 m. It consists of an internal aggradational stacking pattern with elongated mounded packages of continuous, moderate to high amplitude seismic reflectors. EM2 is internally composed by a mix of contourite deposits (Holocene) interbedded with turbiditic and/or mass flow deposits. EM1a,b and EM2 are deposited at the top of an erosional truncation aged at 11.5 ka, so they mostly formed during the Holocene. EM3a,b are ca. 16 km long, more than 6.7 km wide, and have a thickness up to 350 m. Both EM2 and EM3a,b have been interpreted as sheeted drift due to their morphology and seismic features. The spatial distribution of the contourite drifts suggests that the drifts are likely generated by the interaction of the LIW, and deep Tyrrhenian water (TDW) on the seafloor, playing an important role in the shaping this continental margin since the late Pleistocene-Holocene. The results may help to understand the deep oceanic processes affecting the north-western Sicilian continental margin.
Highlights
Bottom currents play a key role in controlling the morphological and sedimentary evolution of continental margins, giving rise to a large spectrum of erosive and depositional morphologies [1,2,3]
We focus on the north-western part of the tectonically active Sicilian Continental Margin between the Castellammare Gulf and the Palermo Gulf (Figure 1), where several geomorphic elements associated with tectonic deformation, slope failure, and fluid seepage were identified, giving rise to a very complex morphology, [33,34,35,36]
The study area is dominated by the thermohaline circulation which forms two pathways of east moving water masses: the Modified Atlantic Water (MAW) and the Levantine Intermediate Water (LIW) (Figure 1) [51,52,53,54,55]
Summary
Bottom currents play a key role in controlling the morphological and sedimentary evolution of continental margins, giving rise to a large spectrum of erosive and depositional morphologies [1,2,3]. Internal and external geometries of the contourite drifts are controlled by a number of factors such as seafloor morphology, current velocity, type and volume of available sediments, climate condition, and sea-level changes [8,20,21]. Based on their morphological and seismic features, Faugères et al (1999) [8] and successively Rebesco et al (2014) [1] proposed an accurate nomenclature to classify contourite drifts, including: (i) elongated mounded drifts, (ii) sheeted drifts, (iii) confined drifts, (iv) channel-related drifts, (v) faultcontrolled drifts, (vi) patch drifts, (vi) infill drifts, and (vii) mixed drifts [1].
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