The mapping and analysis of ancient turbidite deposits using geographically dependent sedimentologic indices (or proximality) determined by genetic facies relationships and grain-size variations were mostly applied during the early years of turbidite research. Nevertheless, the understanding that fine-grained deposits (thin-bedded turbidites) can also occur in proximal (interchannel) areas, and the impossibility of differentiating them from real distal deposits, revealed many inconsistencies in this approach to the development of turbidite fan facies models. More recently, a genetic facies tract has been proposed for hyperpycnal systems, which distinguishes between thin-bedded deposits accumulated in interchannel areas from those deposited on distal areas.

The genetic facies tract proposed for hyperpycnal systems in marine settings comprises three main facies categories related to bed-load, suspended-load, and lofting processes, respectively. Bed-load-related facies are coarse grained and related to drag forces provided by the overpassing turbulent flow. Suspended-load-related facies are composed of fine-grained sandstones and originate from the gravitational collapse of the suspended load as the long-lived flow progressively wanes. Lofting-related facies are the result of the fallout of very fine-grained sands, silts, plant debris, and micas from lofting plumes mainly in flow-margin areas. Proximal (Pt) and lateral (Lt) facies indices have been defined based on the relative abundance of B, S, and L facies within a stratigraphic interval. The Pt and Lt indices are dimensionless numbers that range from 100 to 0. The Pt index measures how proximal a given stratigraphic section is with respect to the entire hyperpycnal system. The Lt index provides an indication of the stratigraphic lateral distance of a given section with respect to the flow axis. These genetic indices were applied to hyperpycnal deposits of the late Oligocene–early Miocene Merecure Formation, Maturin Subbasin, Venezuela.

Results suggest that the Merecure Formation may be more extensive than previously considered with a main sediment source from cratonic areas located in the south and southeast. Index mapping also suggests a syntectonic accumulation during the Oligocene, which controlled the subaqueous topography and, thus, the distribution of sand bodies.