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Depositional and Architectural Evolution of a Turbidite Channel System from Outcrop and Behind-the-outcrop Data: the Solitary Channel Complex (Miocene, Tabernas Basin, SE Spain).

Abstract

The Solitary Channel developed as a slope to base-of slope turbidite channel complex in a back-arc basin in the context of the evolution of the Betic Chain. Exceptional outcrops with multiple orientations allow for both sedimentologic detail as well as a reasonably constrained depiction of the 3D internal architecture of the channel complex. The outcrop description was substantiated by means of the integration of conventional outcrop data and the interpretation of Digital Outcrop Models. The Solitary Channel dataset was furthermore complemented with two wells drilled behind the outcrop, which produced core recovered at about complete, plus downhole geophysical data.

Our data show that most of the channel-fill is made up of sandstones, with minor amounts of conglomerate and less than 5% mudstone. Distribution grading, traction carpet laminae and massive and parallel laminated divisions, all indicate that most sedimentation took place primarily from turbidity currents passing from high to low density conditions. A/B plane clast imbrication is frequent in the coarse-sand and gravelly sandstone beds.

This can be observed in outcrop and quantified in drillcore studies. The results indicate bedload transportation and bedforms accreting perpendicular to channel axes, which can be related to high flow velocity in a high-gradient setting. Disorganized gravelly sandstones and sandy conglomerates are a lesser occurrence and correspond to debrites.

Architectural analysis, following accurate 3D horizon reconstruction and facies modelling, evidences that the dominant fundamental architectural element corresponds to vertically-stacked beds bounded by closely juxtaposed erosional surfaces. These elements can be interpreted as representing avulsion or incision followed by infill.

Groupings of the avulsion-erosion-infill elements are found as arranged into channel complexes, each carrying a significant southeastwards stepping of the channel complex, which can be interpreted as fault-driven accommodation. This is supported by an open fold, minor faults and slide features affecting the channel-fill.

We acknowledge financial support from ExxonMobil and Project MODELGEO (CGL2010–15294). Schlumberger is also acknowledged by donation of Petrel software licenses.