Architectural changes in a coarse-grained deep-water system deposited above a Mass Transport Complex (MTC).

PRIVAT, A.; HODGSON, D.M.; JACKSON, C.A-L.; SCHWARZ, E.; PEAKALL, J.

Londres

Congreso; Deepwater Depositional Systems: Advances and Applications; 2017

Geological Society of London

Local gradient changes and variable accommodation characterize the upper surface of mass transport complexes (MTCs). The associated bathymetric variability can influence the longitudinal and vertical processes occurring within coarse-grained sediment gravity flows, which are challenging to interpret from the rock record alone. Here we document an exhumed deep-water succession from the Los Molles Formation, Neuquén Basin, Argentina to investigate the facies types occurring within and the architecture of, coarse-grained beds deposited above a seismic-scale MTC (20-60 m-thick). The study area is a 12 km-long oblique downdip section within which individual beds are correlated between 21 measured sections (1:25 scale). The stratigraphic succession comprises a 25-70 m thick, sandstone-rich division (69% sandstone) containing two units (Figure 1). Unit 1 comprises a lower heterolithic succession, grading upwards into a sandstone-prone succession that consists in poorly sorted, very coarse to fine-grained, thin to medium bedded sandstones with pebble-sized clasts. Sandstone beds in Unit 1 have a poor bed continuity, high amalgamation and abrupt lateral pinch-out, with evidence for erosion, sediment bypass and lateral facies changes occurring over short down-dip distances (