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

Abstract

Diatomaceous deposits in the Miocene-Pliocene Pisco Formation contain abundant whales preserved in pristine condition (bones articulated or at least closely associated), in some cases including preserved baleen. The well-preserved whales indicate rapid burial. The 346 whales within ϳ1.5 km 2 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. Current depositional models do not account for the volume of diatomaceous 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 protected, shallow embayments, is responsible for the superb preservation of these whales, leading to a higher upper limit on phytoplankton accumulation rates than previously documented.

Stratigraphic framework of the late Miocene Pisco Formation at Cerro Los Quesos (Ica Desert, Peru)

“…Brand, Esperante, Chadwick, Poma Porras, & Alomía, 2004;Ehret et al, 2012;Esperante, Brand, Chadwick, & Poma, 2015;Esperante, Brand, Nick, Poma, & Urbina, 2008;Gariboldi et al, 2015;Lambert, Bianucci, & de Muizon, 2008;Lambert, Bianucci, & Post, 2009Lambert, Bianucci, Post, de Muizon, et al, 2010;Lambert, Bianucci, & Beatty, 2014;Lambert, de Muizon, & Bianucci, 2014;Lambert et al, 2015;Collareta et al, 2015). However, despite the growing significance of the vertebrate fauna of the Pisco Formation, a comprehensive stratigraphic framework for individual fossil-bearing localities and their position relative to one another has yet to be established (Brand, Urbina, Chadwick, DeVries, & Esperante, 2011;Di Celma et al, in press).…”

Evolution of marine mammals: Back to the sea after 300 million years

“…Soft tissue preservation, while rare, does occur. Several instances of baleen preservation have been noted (e.g., Brand et al, 2004), but no other soft tissues of fossil marine mammals have been reported. Thus, any interpretation of the behavior of fossil marine mammals must be reflected in the morphology of the skeleton or teeth, be reflected in modification of the skeleton or teeth, or be interpreted from the depositional context of the fossils.…”

Distribution of fossil marine vertebrates in Cerro Colorado, the type locality of the giant raptorial sperm whaleLivyatan melvillei(Miocene, Pisco Formation, Peru)

“…The first attempt to census the fossil vertebrates in the Pisco Formation was made by Muizon and DeVries (1985). Two decades later, Brand, Esperante and colleagues (Brand, Esperante, Chadwick, Poma, and Alomía, 2004;Esperante, Brand, Nick, Poma, and Urbina, 2008;Esperante, Brand, Chadwick, & Poma, 2015), evidenced an extraordinary concentration of specimens in several localities of the Pisco Formation, but these papers were limited to baleen whales and, consequently, did not provide any useful information about the faunal diversity of these highly fossiliferous areas. With a different approach, Brand, Urbina, Chadwick, DeVries, and Esperante (2011) attempted to place some published fossil vertebrates of the Pisco Formation along several measured stratigraphic sections; their work provided a rough indication of the fossil distribution, only reporting a non-exhaustive list of fossils, some of which were not correctly placed along the stratigraphic sections (Lambert & Muizon, 2014).…”