3-D Submarine geomorphology of the Galicia continental margin and adjacent abyssal plains

Abstract

Submarine geomorphology is the study of landforms and processes in the underwater domain. The ocean hosts a tremendous variety of forms that reflect the action of a range of tectonic, sedimentary, oceanographic, chemical and biological processes at multiple spatio-temporal scales. Submarine geomorphological mapping provides fundamental and effective means to characterize the seabed, an important interface between the geological substrate and the water column, where a range of biological, chemical and hydrodynamic phenomena are dependent on both the morphological and geological character of the seabed. In this way, a new extensive data set acquired of late-particularly for the Law of the Sea extended continental shelf (ECS) in the area of Galicia mapping purposes-provided the opportunity to analyse the 3D submarine geomorphology of the Galicia margin. We use artificial sun-illumination, shading and 3D rendering with digital bathymetric data (DTM's) to form natural looking and easily interpretable submarine landscapes of the main architectural elements that compose the submarine landscapes along the Galicia Margin. This seabed geomorphological mapping of the Galicia Margin allows us to establish the relationship between the processes (tectonic and sedimentary/oceanographic) and the resulting landforms. The submarine geomorphology of the Galicia Margin is inherited from former tectonic stages i.e. Variscan heritage as the Ibero-Armorican Arc, Mesozoic hyperextension of the Iberian-Newfoundland Atlantic conjugate margin, and Cenozoic convergence with subduction of the Bay of Biscay oceanic crust. Otherwise, the main oceanographic morphologies identified in the Galicia Margin related to sedimentary/oceanographic processes are: (i) System of gullies, canyons, channels and 83

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VI International Symposium on Marine Sciences
Vigo (Spain), 20-22th June 2018
3-D SUBMARINE GEOMORPHOLOGY OF THE GALICIA
CONTINENTAL MARGIN AND ADJACENT ABYSSAL PLAINS
L. Somoza 1, T. Medialdea 1, F. J. González 1, R. León1, J. Rengel 2, D. Palomino 3,
L.M. Fernández-Salas 3 & J.T. Vázquez 4
1
1 Marine Geology Mapping Dv. Geological Survey of Spain (IGME), c/ Ríos Rosas 23, 28003
Madrid, Spain. l.somoza@igme.es, t.medialdea@igme.es, fj.gonzalez@igme.es, r.leon@igme.es
2 Instituto Hidrográfico de la Marina, IHM, Cádiz, Spain. jrenortega@fn.mde.es
3 Instituto Español de Oceanografía, C.O. de Cádiz, Muelle de Levante, Puerto Pesquero s/n,
Cádiz, Spain. desiree.palomino@ieo.es, luismi.fernandez@ieo.es
4 Instituto Español de Oceanografía, C.O. de Málaga, Puerto Pesquero s/n, 29649, Fuengirola,
Spain. juantomas.vazquez@ieo.es
.
Abstract: Submarine geomorphology is the study of landforms and processes in the
underwater domain. The ocean hosts a tremendous variety of forms that reflect the action
of a range of tectonic, sedimentary, oceanographic, chemical and biological processes at
multiple spatio-temporal scales. Submarine geomorphological mapping provides
fundamental and effective means to characterize the seabed, an important interface
between the geological substrate and the water column, where a range of biological,
chemical and hydrodynamic phenomena are dependent on both the morphological and
geological character of the seabed.
In this way, a new extensive data set acquired of late-particularly for the Law of the Sea
extended continental shelf (ECS) in the area of Galicia mapping purposes- provided the
opportunity to analyse the 3D submarine geomorphology of the Galicia margin. We use
artificial sun-illumination, shading and 3D rendering with digital bathymetric data
(DTM's) to form natural looking and easily interpretable submarine landscapes of the main
architectural elements that compose the submarine landscapes along the Galicia Margin.
This seabed geomorphological mapping of the Galicia Margin allows us to establish the
relationship between the processes (tectonic and sedimentary/oceanographic) and the
resulting landforms.
The submarine geomorphology of the Galicia Margin is inherited from former tectonic
stages i.e. Variscan heritage as the Ibero-Armorican Arc, Mesozoic hyperextension of the
Iberian-Newfoundland Atlantic conjugate margin, and Cenozoic convergence with
subduction of the Bay of Biscay oceanic crust.
Otherwise, the main oceanographic morphologies identified in the Galicia Margin related
to sedimentary/oceanographic processes are: (i) System of gullies, canyons, channels and
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deep-sea fans related to turbidity currents/dense shelf water cascading; (ii) Drifts, moats
and abyssal channels driven by geostrophic ocean circulations, (iii) giant rotational and
translational deep-seated landslides triggered by slope instability and mass-transport; (iv)
pockmarks and giant craters associated with deep-seated seabed fluid-flow processes.
Key words: Seabed Mapping, Submarine Geomorphology, Galicia Margin, UNCLOS,
Multibeam echosounders.
Acknowledgments: This work was supported by the Spanish project for the Extension of
the Continental Shelf according United Convention for the Law of the Sea (UNCLOS), the
Project EMODNET-Geology (EASME/EMFF/2016/1.3.1.2-Lot 1/S12.750862) and the
EXPLOSEA project (CTM2016-75947-R).
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