Dimensions and architecture of late Pleistocene submarine lobes off the northern margin of East Corsica

Abstract

Sandy lobe deposits on submarine fans are sensitive recorders of the types of sediment gravity flows supplied to a basin and are economically important as hydrocarbon reservoirs. This study investigates the causes of variability in 20 lobes in small late Pleistocene submarine fans off East Corsica. These lobes were imaged using ultra-high resolution boomer seismic profiles (<1 m vertical resolution) and sediment type was ground truthed using piston cores published in previous studies. Repeated crossings of the same depositional bodies were used to measure spatial changes in their dimensions and architecture. Most lobes increase abruptly down-slope to a peak thickness of 8 to 42 m, beyond which they show a progressive, typically more gradual, decrease in thickness until they thin to below seismic resolution or pass into draping facies of the basin plain. Lobe areas range from 3 to 70 km 2 and total lengths from 2 to 14 km, with the locus of maximum sediment accumulation from 3 to 28 km from the shelf-break. Based on their location, dimensions, internal architecture and nature of the feeder channel, the lobes are divided into two end-member types. The first are small depositional bodies located in proximal settings, clustered near the toe-of-slope and fed by slope gullies or erosive channels lacking or with poorly developed levées (referred to as 'proximal isolated lobes'). The second are larger architecturally more complex depositional bodies deposited in more distal settings, outboard more stable and longer-lived levéed fan valleys (referred to as 'composite mid-fan lobes'). Hybrid lobe types are also observed. At least three hierarchical levels of compensation stacking are recognized. Individual beds and bed-sets stack to form lobe-elements; lobe-elements stack to form composite lobes; and composite lobes stack to form lobe complexes. Differences in the size, shape and architectural complexity of lobe deposits reflect several inter-related factors including: (i) flow properties (volume, duration, grain-size, concentration and velocity); (ii) the number and frequency of flows, and their degree of variation through time; (iii) gradient change and sea floor morphology at the mouth of the feeder conduit; (iv) lobe lifespan prior to avulsion or abandonment; and (v) feeder channel geometry and stability. In general, lobes outboard stable fan valleys that are connected to shelf-incised canyons are wider, longer and thicker, accumulate in more basinal locations and are architecturally more complex.

Quantification of the Bed-scale Architecture of Submarine Depositional Environments and Application to Lobe Deposits of the Point Loma Formation, California

“…Each environment is commonly associated with a particular geometry, facies, and bed thickness distribution (Mutti and Normark, 1987;Normark, 1978;Sullivan et al, 2000;Deptuck et al, 2008;Prélat et al, 2009;Hubbard et al, 2014;Stevenson et al, 2015). For example, submarine lobe deposits typically show a qualitative decrease in bed thickness, grain size, sand content, and amalgamation in proximal-to-distal and axis-to-margin transects (Normark, 1978;Sullivan et al, 2000;Deptuck et al, 2008;Prélat et al, 2009).…”

“…For example, submarine lobe deposits typically show a qualitative decrease in bed thickness, grain size, sand content, and amalgamation in proximal-to-distal and axis-to-margin transects (Normark, 1978;Sullivan et al, 2000;Deptuck et al, 2008;Prélat et al, 2009). However, the details of these downstream and lateral facies changes are often overlooked, and very few studies perform correlations at the bed scale (e.g., Chapin and Tiller, 2007;Marini et al, 2015).…”

Sedimentology, Stratigraphic Context, and Implications of Miocene Intrashelf Bottomset Deposits, Offshore New Jersey

“…Each coarse-grained package at Site M29 has its own thickness, ratio of glauconite to quartz sand, and grain-size distribution, which could suggest compensational stacking of lobe deposits (e.g., Prélat et al, 2009). Several studies have shown that compensational stacking of basin-floor elements can occur across a range of scales (e.g., Deptuck et al, 2008;Prélat et al, 2009;van der Merwe et al, 2014). It is striking that coreholes at both Sites M28 and M29, which are 9 km apart in a dip direction, intersected the same sharp-based coarse-grained deposits in all sequences, apart from m5.47 (Fig.…”

Implications of Sediment Dynamics in Mass Transport along the Pianosa Ridge (Northern Tyrrhenian Sea)

“…The sediment input from the Tuscan Shelf is low since sediment from Italian rivers is mostly trapped in the shelf and cannot reach the Corsica Trough (Roveri 2002). Most of the sediment deposited in the Corsica Trough is transported from the Corsica shelf by the Golo turbidite network (Deptuck et al 2008; Fig. 1).…”