The Stratigraphic Evolution of a Migrating Submarine Channel System in a Tectonically-Confined Basin: Driving Factors and Implications for Reservoir Prediction – The Gorgoglione Flysch Formation, Southern Italy

Abstract

The Gorgoglione Flysch Fm is a siliciclastic turbidite succession developed during the Miocene in a narrow and elongate thrust-top basin of the Southern Apennines (Italy). The stratigraphic product of protracted sediment transfer and deposition through a long-lived channel system is recorded in a wide outcrop belt, oriented nearly parallel to the basin axis and regional palaeoflow. These exceptional exposures of channel-fill strata allow the stacking architectures and the general evolution of the channel system to be analysed at multiple scales, enabling the effects of syn-sedimentary thrust tectonics and basin confinement on the depositional system development to be deciphered. An approach based on the integration of standard sedimentary facies analysis and emerging digital techniques for outcrop mapping has been employed to enhance the interpretation of the multiple levels of turbidite channel hierarchy. Two end-member types of elementary channel architecture, each consisting of a distinct internal facies distribution and associated out-of-channel deposits, have been identified: (i) high-aspect-ratio, weakly-confined channels flanked by sand-prone heterolithic deposits, with abundant amalgamated poorly-sorted sandstones in the channel axes that pass to less amalgamated clean sandstones and planar-laminated sandstones towards the margins; and (ii) low-aspect-ratio, strongly-confined channels flanked by mud-prone heterolithic deposits, with poorly-sorted sandstones and matrix-supported conglomerates dominating the majority of channel element’s infill. The deposition of different channel architectures is interpreted to have been governed by regional thrust tectonics, combined with a high subsidence rate that promoted significant aggradation. In this scenario, the alternate in- and out-of-sequence tectonic pulses of the basin-bounding thrust structures controlled the activation and deactivation of the coarse-clastic inputs in the basin. The tectonically-driven confinement of the depositional system limited the lateral offset in channel stacking, preventing large-scale avulsions and the development of superelevated levees. This study should find wide applicability in analogous depositional systems in the subsurface, developed within elongate basins in active tectonic settings, facilitating the characterization of hydrocarbon reservoirs whose hosting architecture has been influenced by tectonically-controlled lateral confinement and associated lateral tilting.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018