Evolution of a carbonate delta generated by gateway‐funnelling of episodic currents

Abstract

Cool-water carbonate sedimentation has dominated Mediterranean shelves since the Early Pliocene. Skeletal sand and gravel herein consist of remains of heterozoan organisms, which are susceptible to reworking due to weak early cementation in non-tropical waters. This study documents the Lower Pleistocene carbonate wedge of Favignana Island (Italy), which prograded from a 5 km wide passage between two palaeo-islands into a perpendicular, 10 to 15 km wide strait between the palaeo-islands at one side and Sicily at the other during the Emilian highstand (1Á6 Ma to 1Á1 Ma). The clinoformed carbonate wedge, which is 50 m thick and 6 km long, formed by east/southeast progradation of a platform on the submarine sill by currents that were funnelled between the two palaeo-islands. Platform-slope clinoforms evolved from initial aggradation (thin and low-angle) into a progradation phase (thick and high-angle). Both clinoform types are characterized by a bimodal facies stacking pattern defined by sedimentary structures created by: (i) subaqueous dunes associated with dilute subcritical currents; and (ii) upper-flow-regime bedforms associated with sediment-laden supercritical turbidity currents. Focusing of episodic currents on the platform by funnelling between the islands controlled the downstream formation of a sediment body, here named carbonate delta. The carbonate delta interfingers with subaqueous dune deposits formed in the perpendicular strait. This study uses a reconstruction of bedform dynamics to unravel the evolution of this gatewayrelated carbonate accumulation.

Froude supercritical flow processes and sedimentary structures: New insights from experiments with a wide range of grain sizes

“…The experiments indicate that cyclic step instabilities enhance deposition and erosion to occur in bursts, where erosion on the supercritical lee side of the hydraulic jumps generates surges of sediment that are partially deposited in the vicinity of the hydraulic jump and partially transported further downstream. Erosion on the supercritical lee side and beneath the underflow within the hydraulic jump forms the composite erosion surface, as previously described by Slootman et al ., 2019 (Figs 5 and 6). Deposition starts in the vicinity of the hydraulic jump where supercritical flow transitions into subcritical flow (see also Winterwerp et al ., 1992; Kostic & Parker, 2006; Cartigny et al ., 2014; Vellinga et al ., 2018).…”

“…McKee et al ., 1967; Williams, 1971; Frostick & Reid, 1977; Foley, 1978; Tunbridge, 1981; Stear, 1985; Abdullatif, 1989; Bromley, 1991; North & Taylor, 1996; Alexander et al ., 2001; Fielding, 2006; Billi, 2007; Fielding et al ., 2009; Plink‐Björklund, 2015, 2018; Fielding et al ., 2017). Supercritical flow deposits have also been described from a variety of other depositional environments, such as deltas (Massari, 1996; Ventra et al ., 2015; Dietrich et al ., 2016; Hughes Clarke, 2016), carbonate ramps (Massari & Chiocci, 2006; Lüdmann et al ., 2018; Slootman et al ., 2019), glacial settings (e.g. Russell & Arnott, 2003; Duller et al ., 2008; Lang & Winsemann, 2013; Lang et al ., 2017b) and volcanic settings (Schmincke et al ., 1973; Casalbore et al ., 2014; Clare et al ., 2018; Pope et al ., 2018).…”

A Cretaceous carbonate delta drift in the Montagna della Maiella, Italy

“…B). Such successions have been described as related to supercritical flow structures (Massari, 2017; Slootman et al ., ). Other pebbly conglomerates are horizontally stratified with horizons rich in clasts separated by the grainstone matrix (Fig.…”

The depositional signature of high‐aggradation chute‐and‐pool bedforms: The build‐and‐fill structure

“…Continuous coastal cliffs display a large-scale clinoform architecture consisting of south-eastprograding units up to 50 m high, 500 m long and tens of metres thick, dipping approximately 5 to 20°. These clinoforms are the main building blocks of a prograding carbonate wedge, reflecting the outbuilding of a carbonate slope (Slootman et al, 2016(Slootman et al, , 2019Moscariello et al, 2018). The clinoform succession composes the largest part of the wedge and consists of a bimodal stacking of facies associations B and C in the terminology of Slootman et al (2019).…”

“…These clinoforms are the main building blocks of a prograding carbonate wedge, reflecting the outbuilding of a carbonate slope (Slootman et al, 2016(Slootman et al, , 2019Moscariello et al, 2018). The clinoform succession composes the largest part of the wedge and consists of a bimodal stacking of facies associations B and C in the terminology of Slootman et al (2019). The nature of B-units and C-units varies as a function of subenvironment.…”