File:Pisco Formation cetacean preservation model (1).png

English: Proposed mechanism of rapid self-burial (I). Diagrams summarising steps in the proposed storm-related self-burial mechanism rapidly burying large cetacean carcasses resting on the seafloor at various stages of decay. Note the smaller scale in profile view. A) In this scenario the whale carcass reaches the sediment-water interface relatively soon after death, largely intact or in a very early stage of decay after a short floating phase at the sea surface. Under storm conditions, currents and waves develop a scour pit around the carcass. As erosion around and beneath the carcass proceeds and the scour depression deepens, the carcass gradually sinks into the deepening depression. Concentration of small pebbles near the head results from winnowing of loose fine-grained sand and silt, leaving gravel-size particles in the scour depression. B) Once the carcass has settled below the level of the surrounding bottom, where it no longer acts as an obstruction to flow, the scour depression is filled in by sediments, completely burying the carcass before significant decomposition may take place. C) Deformation and sagging of laminae in the scour-filling sediments were presumably due to decay of the soft tissues and compaction by the weight of overlying sediment, which resulted in some squashing of the sediments deposited inside the scour and partial penetration of fossil bones into the underlying sediments. Bone colours in the figure refer to those coded in Fig 3.