Peru, the origin of one of the largest cetacean fossil deposits in the world revealed

The low concentration of oxygen at the bottom, the rapid burial of the carcasses and the precipitation of minerals such as apatite and dolomite immediately after the burial of the bones, together with the original biological richness: these are the conditions that would be at the origin of one of the most the world’s largest marine vertebrate fossil deposits (PHOTOGALLERY). It is located in one of the driest areas on the planet, the Ica Desert of southern Peru, and is such an exceptional field because it is home to thousands of fossilized records of whales, dolphins, seals, sharks and other fish, birds and reptiles dating back to an of time between 14 and 6 million years ago (an epoch that geologists call “Miocene”). The group of researchers from the Milano-Bicocca University (Giulia Bosio and Elisa Malinverno), from the University of Camerino (Claudio Di Celma) and the University of Pisa (Giovanni Bianucci, Alberto Collareta, Anna Gioncada and Karen Gariboldi), in collaboration with scholars from various foreign research institutes, has revealed the causes of the origin of this extraordinary paleontological site thanks to the study of almost 900 finds, often exceptionally preserved, in an article entitled “Taphonomy of marine vertebrates of the Pisco Formation (Miocene, Peru): Insights into the origin of an outstanding Fossil-Lagerstätte”, just published in magazine “Plos One”. “Where today there is a desert that extends for hundreds of kilometers along the coast of Peru – explains the geologist Claudio Di Celma – in the past there was a large marine basin, the Pisco Basin, characterized by a great abundance of nutrients and a rich biodiversity “. “The inhabitants of this ancient bay have been preserved for millions of years and are now exposed around Ica thanks to tectonic uplift and erosion in the current desert environment. The absence of vegetation that characterizes the area also greatly facilitates the discovery of the finds »” continues the paleontologist Elisa Malinverno. “The study of the distribution of the finds, the associated fauna and the traces left by shark bites on the bones – says paleontologist Alberto Collareta – together with that of the rocks in which the fossils are contained , made it possible to reconstruct the taphonomic history of these extraordinary finds, that is what allowed their conservation as fossils from the moment of their death to the present day “. It was therefore a concomitance of various conditions favorable to fossilization that gave rise to this extraordinary deposit, as explained by the paleontologist Giulia Bosio of the University of Milano-Bicocca, first author of the article: “The low concentration of oxygen at the bottom, the rapid burial of the carcasses and the precipitation of minerals such as apatite and dolomite immediately after the burial of the bones, together with the original biological richness have allowed the formation of this important deposit , leading to the fossilization of thousands of specimens “. Particularly interesting is the recognition of some skeletons of whales whose arrangement and relations with the surrounding rocks suggest that the carcass has undergone a” self-burial “mechanism. This happens when relatively heavy objects settle on a seabed crossed by currents; these quickly erode the sediment on which the obstacle rests (in our case, the carcass), thus causing it to sink into a cavity which is then just as quickly filled with new sediment. The result of this process – much studied with regard to submarine mines but never recognized in paleontological contexts – is the rapid engulfment by the sediment of a carcass which is thus protected from the action of “scavengers” organisms and many others. “disturbing” factors. The study was carried out, with numerous prospecting and excavation campaigns, by researchers from the universities of Milan-Bicocca, Pisa and Camerino, coordinated by the paleontologist Giovanni Bianucci of the University of Pisa, in collaboration with the Institut Royal des Sciences Naturelles de Belgique (Brussels, Belgium), the Museum of New Zealand Te Papa Tongarewa (Wellington, New Zealand), the University of Otago (Dunedin, New Zealand), the Muséum national d’Histoire naturelle (Paris, France) and the Museo de Historia Natural (Lima, Peru).