Grain-Size Distribution and Sedimentary Transport Patterns in Deep Water Rift Basins: Plio-Pleistocene Syn-Rift of the Corinth Rift, Greece

Abstract

Deep water sedimentary systems are major exploration targets in many rifted margin petroleum provinces. Due to their inaccessibility and the relatively coarse resolution of seismic imaging, the intrinsic link between the different architectural elements that comprise submarine channels and lobes and their lithological heterogeneity requires outcrop analogue studies. This presentation focuses on exceptional, seismic-scale exposures of Plio-Pleistocene syn-rift deep water depositional systems exposed in the central part of the Corinth Rift. A combination of digital outcrop techniques (LIDAR and photogrammetry), integrated with sedimentological, stratigraphic and structural analysis is used to characterise the stratigraphy, and reservoir geometry and heterogeneity. The results of this study have important implications for the prediction of grain-sizes and reservoir characteristics in deep water rift basins. The studied succession corresponds to a pro-delta to basin floor setting that can be divided in a lower, ~250 m thick unit of laterally extensive conglomerate and sandstone bodies intercalated with finely laminated mudstones, and an upper unit dominated by more than 800 m of marlstones, sandstones and localized conglomerates. The conglomerate-dominated bodies are 2 to 15 m thick and extend laterally for 20 to 300 m. They have a varied geometry, constituting sheets of laterally amalgamated channels, lobes and, less commonly, isolated single-storey channels. The sandstone-dominated bodies are 0.15 to 1 m thick tabular bodies that extend laterally for more than 500 m and the finest-grained deposits are composed of an alternation of laminated claystone beds up to 10 cm thick with 1 to 5 cm thick laminated sandstones and siltstones. Sediment was mainly sourced by several rift shoulder fan deltas (the Kilini, Mavro, Evrostini and Illias deltas), generating a series of transverse entry points that converged into a major axial deep-water drainage system, similar to the present day subaqueous configuration of the Gulf of Corinth. A clear contrast in the stacking pattern of the conglomerate channels is observed: in the lower unit they are numerous and laterally scattered and become fewer and more localized in the upper unit. This variation is interpreted to be linked to a deepening of the depositional environment controlled by the tectonic evolution of the southern margin of the Corinth Rift.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017