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@article{Lonergan:2013:10.1016/j.margeo.2013.02.001,
author = {Lonergan, L and Jamin, NH and Jackson, CA-L and Johnson, HD and Lonergan, L and Jamin, NH and Jackson, CAL and Johnson, HD},
doi = {10.1016/j.margeo.2013.02.001},
journal = {Marine Geology},
pages = {80--97},
title = {U-shaped slope gully systems and sediment waves on the passive margin of Gabon (West Africa)},
url = {http://dx.doi.org/10.1016/j.margeo.2013.02.001},
volume = {337},
year = {2013}
}
TY - JOUR
AB - 3-D seismic reflection data has enabled the documentation of a system of remarkable modern and buried u-shaped gullies which intimately co-exist with upslope migrating sediment waves along 80 km of the Gabon continental slope. The modern gullies occur on a silty mud-dominated slope in water depths of 150–1500 m on an ~50 km wide slope with a gradient of 4.5° decreasing to 1.5°. The gully sets persist laterally for distances of at least 40 km and extend downslope for distances of up to 60 km. The gullies are u-shaped in crosssection,with a relief of 5–30 m, and widths of 50–400 m. Intriguingly, the gullies become narrower andshallower with distance down the slope, as well as increasing in number down slope. The majority of the gullies appear to be erosional but some appear to have resulted from simultaneous aggradation along inter-gully ridges and non-deposition along the adjacent gully floor. Hence, these gullies are interpreted to have formed mainly inresponse to spatially-variable deposition, rather than erosion. Upslope migrating sediment waves occur in close proximity to the gullies. Gullies cross fields of sediment waves and waves are observed to migrate up-slopelocally within both the erosional and aggradational gullies. Evidence is lacking for any slumping or headward erosion in the headwall region of the gullies, which discounts formation by very local sediment gravity flowsoriginating from shelf-edge collapse, as has been observed in other v-shaped gully systems. Based on our new data, and supported by theoretical studies on the mechanics of turbidity currents, we propose that the gulliesand related sediment waves were formed by diffuse, sheet-like, mud-rich turbidity currents that presumably originated on the shelf. Instabilities in the turbidity currents generated a wave-shaped perturbation in a crossflow direction leading to regularly spaced regions of faster and slower flow. For the non-aggradational and erosional gullies it is
AU - Lonergan,L
AU - Jamin,NH
AU - Jackson,CA-L
AU - Johnson,HD
AU - Lonergan,L
AU - Jamin,NH
AU - Jackson,CAL
AU - Johnson,HD
DO - 10.1016/j.margeo.2013.02.001
EP - 97
PY - 2013///
SP - 80
TI - U-shaped slope gully systems and sediment waves on the passive margin of Gabon (West Africa)
T2 - Marine Geology
UR - http://dx.doi.org/10.1016/j.margeo.2013.02.001
UR - http://www.sciencedirect.com/science/article/pii/S0025322713000133
VL - 337
ER -