Slopes and Slumps

Imaged by backscatter techniques offshore the US Eastern Seaboard, and on the flanks of Hawaii. These are 10’s of km across and produce large scale erosion surfaces in margin stratigraphy, clearly seen in the seismic record. Tend to involve collapse of water saturated sediment that fold and deform plastically, but the sediment is not re-suspended. Slumps may be triggered by sealevel fall with or without the sometime catastrophic loss of solid methane hydrates that are held at shallow levels below the seafloor along many margins today (e.g., Blake Nose, E. USA). Ancient examples known in Greek Alpine chains. Major slumps generate tsunamis.

Typical clastic margin morphology

Margin types-sealevel

Faulted clastic margin morphology

Nova Scotia Margin

Gulf of Mexico, slumping

Large slumps, Eastern USA margin

Large slumps, African margin

Large slumps, African margin-2

Giant slump folds in calcareous turbidites, Cretaceous, Greece