Deepwater Sandstone Fairways and Their Interaction with Substrate: Analogues From the Numidian Turbidites (Miocene) of Sicily

Abstract

Deepwater quartz-rich sandstones derived from mature cratons form reservoirs in many hydrocarbon provinces. These include not only rifted margins of the Atlantic but also tectonically active margins where turbidity currents have interacted with deformed substrate. An understanding of the controls on the distribution of sandstone body thickness and architecture will aid exploration and production strategies in these areas. The Numidian “flysch” is an Oligo-Miocene succession of clean, quartz-rich deep marine sandy turbidite deposits. It was sourced from the North African craton and transported northwards across the continental margin into the foredeep system of the Apennine orogen. The regional extent of these sands is well-established; they extend for some 500 km along strike and down dip with outcrops preserved within the Maghrebian-Apennine thrust belt of Sicily and southern Italy. These deposits are commonly regarded to have been deposited on undeformed substrate within ancentral foredeep, however there are evidences that the turbidity flows interact with active basin evidenced by large scale onlap and relationship between basin floor and slope substrata. This work focuses on detailed mapping of the Numidian stratigraphy and establishing the chronostratigraphic and structural relationships to underlying and overlying stratigraphic units in order to constrain local and regional basin architecture. Three areas have been studied in detail – Mt. Salici, Pollina and Madonie Mountains, Sicily – where key stratigraphic sections were logged and palaeocurrent data collected to establish facies schemes. Observations at outcrop and petrographic analysis are used to describe the facies. Modal analysis demonstrates that the Numidian sandstones are quartz-arenite type derived from craton interior. Also eleven sandstone samples were analyzed by LA-ICPMS and show detrital zircon ages strongly consistent with African source signature. Biostratigraphic samples (foraminifera) were collected mainly from top and base of sandstones to establish chronostratigraphic context and correlation between the sections. Panoramic views were traced to follow lateral continuity and geometry of the beds. Future work will focus on extending the study across northern and Central Sicily to better constrain the influence of basin tectonics on ponding and deflection of the Numidian gravity flows.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015