Landslide influence on delta stratigraphy, northeastern Gulf of Mexico

Abstract Although wave, tide, and river controls on deltas are well established, there has been less work on the influence of growth faults and submarine landslides on delta stratigraphy and deep-water sediment delivery. We used an ~1200 km2 portion of a three-dimensional seismic-reflection dataset (wherein peak frequency ranges ~30 Hz to 50 Hz in the shallow interval) in the northeastern Gulf of Mexico1 to document the stratigraphic evolution of its shelf margin during the last 0.5 m.y. We mapped five deltas, which were deposited one at a time during glacio-eustatic lowstands since oxygen isotope stage (OIS) 14. Deltas active during OIS 12, 10, and 6 are erosionally truncated by submarine landslides, which nucleated along prominent growth faults. The landslide-dominated interval shows progressively increasing thickness variability in deposits filling local landslide scarps. In addition, depocenters migrated great distances, ~10 km on average, but with a lot of variability from one delta to the next (5–20 km). Prominent submarine channels formed in the landslide scarps, and downstream mass-transport deposits constrained channel orientation. Shelf-margin evolution is different along strike in the east, where the older, well-documented Fuji-Einstein delta complex lacks landslides and exhibits more typical geometries of unperturbed deltas, i.e., lenticular cross-sectional and oval map-view geometries, with submarine channels forming in prodelta gullies rather than landslide scarps. Our detailed mapping and analysis of shelf-margin evolution in the northeastern Gulf of Mexico during the last half million years are useful as a process analog for older, poorly imaged, and/or locally sampled subsurface intervals there and in other settings with delta-fed submarine channels.