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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.

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Tsunamis are marked by distinct phases of uprush during coastal inundation and backwash when tsunami water recedes. Especially in the case of a steep coastal profile, the return flow may operate in a Froude-supercritical regime, eroding the flooded area and transporting large volumes of sediment seawards. Important sediment accumulation occurs when the supercritical flow goes through a hydraulic jump where it becomes subcritical upon deceleration. An inferred example in coarse-grained, mixed carbonates from the Lower Pleistocene on Rhodes (Greece) is described, with offshore bars up to 10 m long with scour-and-fill structures and steep antidune stratification. In finer-grained sandy depositional systems such structures may be much longer, up to hundreds of metres. It is suggested here that, analogous to some turbidite beds, the apparent lack of structures or the presence of faint stratification that is common for graded sand layers within marine tsunamiites may in fact consist of extremely low-angle, landward-dipping backset-strata that formed under a landward-migrating hydraulic jump during the basinward retreat of tsunami water. Numerical simulations that focus on the internal stratification of backwash-generated offshore bars support this hypothesis. The recognition of such deposits in the sedimentary record enlarges the toolbox for assessing the past frequency of tsunamis in coastal areas.

Chutes-and-pools are hybrid bedforms that occur in upper-flow-regime conditions, populating the stability field between antidunes and cyclic steps. Chutes-and-pools consist of a superimposition of a train of antidunes on a longer-wavelength cyclic-step instability. The presence of a hydraulic jump is more persistent in chutes-and-pools than the bores occasionally seen on breaking-wave antidunes, yet not permanent as over cyclic-step bedforms. The nature of chute-and-pool structures preserved in the depositional record is controlled largely by aggradation rate. This paper documents chute-and-pool structures generated beneath highly aggradational sediment density-flows at the subaqueous toe-of-slope of a Pleistocene carbonate wedge. Quarry exposures enable the morphodynamic reconstruction of the sediment-bed configuration that produced the identified structures. Wavebreaking on growing antidunes occurred without the destruction of the antidune, which deviates from observations in low-aggradation subaerial open-channel flows. The antidune build-up was followed by hydraulic jump controlled deposition in the antidune trough. Two-dimensional depthresolved numerical simulations have been used to validate this process interpretation. The term aggradational chutes-and-pools is proposed for these bedforms, associated with the formation of build-and-fill structures consisting of interstratified convex lenses (in-phase wave regime) and concave lenses (hydraulic jump regime). Such structures contrast with the scour-and-fill structures produced by low-aggradation chutes-and-pools frequently described from subaerial open-channel-flow deposits. This study demonstrates a potential difference in flow behaviour between open-channel flows and density flows in the supercritical regime.

Particle transport and deposition in turbidity currents is governed by the balance between turbulent suspension and gravitational settling, with settling velocity becoming dominant during the final rain‐out phases of decelerated turbidity currents on lobes. Differential particle settling velocities play a role in the sorting of grains in turbidity currents; there is a preference of grains with higher settling velocities to be deposited first, yielding a settling‐velocity gradient in vertical and longitudinal cross‐sections through turbidite beds. If sediments contain little variation in particle shape and density (for example, siliciclastics), then settling velocity is dominantly controlled by grain size. Carbonate sediments, in contrast, are composed of non‐skeletal and skeletal grains with various growth structures, producing a wide distribution of particle shapes (from spheroidal to platy, bladed and elongated forms). The present paper aims to constrain the extent to which shape‐dependent differential settling velocities influence sorting mechanisms in carbonate turbidity currents. Experiments using natural skeletal sand were conducted to investigate the settling of carbonate grains in: (i) isolation; (ii) suspension clouds; and (iii) turbidity currents. Size, density and shape parameters, including Corey Shape Factor and Zingg diagrams, were analysed using high‐resolution micro‐computed tomography. The slower settling of non‐spheroidal shapes was quantified. In the sinking suspensions, a sorting mechanism operated through differential velocities yielding an abundance of spheroidal grains at the base and enrichment in less‐spheroidal grains towards the top of suspension deposits. This trend was also observed longitudinally in carbonate turbidity currents, for which enhanced advection lengths caused less spheroidal grains to be transported farther into the basin. The effect of particle shape becomes increasingly significant as grain size increases, in particular above medium sand. Carbonate turbidites may therefore be more poorly sorted than siliciclastic turbidites, which is expected to result in lower primary porosity in calciturbidites compared to siliciclastic turbidites.