Fossil whale preservation implies high diatom accumulation rate in the Miocene–Pliocene Pisco Formation of Peru

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Abstract
Diatomaceous deposits in the Miocene-Pliocene Pisco For- mation contain abundant whales preserved in pristine condition (bones articulated or at least closely associated), in some cases in- cluding preserved baleen. The well-preserved whales indicate rapid burial. The 346 whales within ;1.5 km2 of surveyed surface were not buried as an event, but were distributed uninterrupted through an 80-m-thick sedimentary section. The diatomaceous sediment lacks repeating primary laminations, but instead is mostly massive, with irregular laminations and speckles. There is no evidence for bioturbation by invertebrates in the whale-bearing sediment. Cur- rent depositional models do not account for the volume of diato- maceous sediments or the taphonomic features of the whales. These taphonomic and sedimentary features suggest that rapid burial due to high diatom accumulation, in part by lateral advection into pro- tected, shallow embayments, is responsible for the superb preser- vation of these whales, leading to a higher upper limit on phyto- plankton accumulation rates than previously documented.