Sedimentary processes in a submarine canyon excavated into a temperate-carbonate ramp (Granada Basin, southern Spain)

Authors

  • ÁNGEL PUGA-BERNABÉU,

    1. Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Campus de Fuentenueva s.n., Universidad de Granada, 18002 Granada, Spain (E-mail: angelpb@ugr.es) Associate Editor: Christian Betzler
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  • JOSÉ M. MARTÍN,

    1. Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Campus de Fuentenueva s.n., Universidad de Granada, 18002 Granada, Spain (E-mail: angelpb@ugr.es) Associate Editor: Christian Betzler
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  • JUAN C. BRAGA

    1. Departamento de Estratigrafía y Paleontología, Facultad de Ciencias, Campus de Fuentenueva s.n., Universidad de Granada, 18002 Granada, Spain (E-mail: angelpb@ugr.es) Associate Editor: Christian Betzler
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Abstract

During the Late Tortonian, shallow-water temperate carbonates were deposited in a small bay on a gentle ramp linked to a small island (Alhama de Granada area, Granada Basin, southern Spain). A submarine canyon (the ‘Alhama Submarine Canyon’) developed close to the shoreline, cross-cutting the temperate-carbonate ramp. The Alhama Submarine Canyon had an irregular profile and steep slopes (10° to 30°). It was excavated in two phases reflected by two major erosion surfaces, the lowermost of which was incised at least 50 m into the ramp. Wedge-shaped and trough-shaped, concave-up beds of calcareous (terrigenous) deposits overlie these erosional surfaces and filled the canyon. A combination of processes connected to sea-level changes is proposed to explain the evolution of the Alhama Submarine Canyon. During sea-level fall, part of the carbonate ramp became exposed and a river valley was excavated. As sea-level rose, river flows continued along the submerged, former river-channel, eroding and deepening the valley and creating a submarine canyon. At this stage, only some of the transported conglomerates were deposited locally. As sea-level continued to rise, the river mouth became detached from the canyon head; littoral sediments, transported by longshore and storm currents, were now captured inside the canyon, generating erosive flows that contributed to its excavation. Most of the canyon infilling took place later, during sea-level highstand. Longshore-transported well-sorted calcarenites/fine-grained calcirudites derived from longshore-drift sandwaves poured into and fed the canyon from the south. Coarse-grained, bioclastic calcirudites derived from a poorly sorted, bioclastic ‘factory facies’ cascaded into the canyon from the north during storms.

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