Taphonomy and palaeoecology of the lower Miocene marine vertebrate assemblage of Ullujaya (Chilcatay Formation, East Pisco Basin, southern Peru).

Bianucci, Giovanni; Collareta, A.; Bosio, Giulia; Landini, W.; Gariboldi, Karen; Gioncada, Anna; Lambert, O.; Malinverno, Elisa; Muizon, C. de; Varas-Malca, R.; Villa, Igor Maria; Coletti, Giovanni; Urbina, M.; Di Celma, Claudio (2018). Taphonomy and palaeoecology of the lower Miocene marine vertebrate assemblage of Ullujaya (Chilcatay Formation, East Pisco Basin, southern Peru). Palaeogeography, Palaeoclimatology, Palaeoecology, 511, pp. 256-279. Elsevier 10.1016/j.palaeo.2018.08.013

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The taphonomy and palaeoecology of the early Miocene (Burdigalian) vertebrate assemblage of Ullujaya (East Pisco Basin, Peru) is here described. Vertebrate remains are concentrated in marine facies (Ct1a association) of the exposed Chilcatay Formation (dated 19–18 Ma) deposited within a 30–40 m deep, semi-enclosed, offshore environment. Coupled with ichnological observations, the size distribution of pyrite framboid relics reveals fluctuation of euxinic and oxic-dysoxic conditions at the seafloor. The assemblage is dominated by toothed cetaceans (kentriodontids, squalodelphinids, physeteroids, and the eurhinodelphinid-like Chilcacetus), together with a large dermochelyid turtle, some bony fish, and diverse elasmobranchs, mostly juveniles of Carcharhinus brachyurus and Cosmopolitodus hastalis. The vertebrate assemblage comprises a coastal community, dominated by mesopredators, representative of a warm-temperate, sheltered embayment connected with riverine and open-ocean environments. Vertebrate skeletons are typically disarticulated and incomplete, and some bone elements display shark bite marks. Microborings are observed at the bone surface. Bones exhibit a good degree of apatite mineralisation and bone cavities are locally filled by Ca-Mg carbonates. Our taphonomic observations suggest prolonged flotation of carcasses during which they were subject to biogenic and physical processes of partial destruction (including scavenging by sharks), before final deposition on a soft compact substrate. Preservation was favoured by the oxygen-deficient bottom conditions that inhibited the action of benthic macro-scavengers.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Isotope Geology
08 Faculty of Science > Other Institutions > Emeriti, Faculty of Science

UniBE Contributor:

Villa, Igor Maria

Subjects:

500 Science > 550 Earth sciences & geology
500 Science > 560 Fossils & prehistoric life

ISSN:

0031-0182

Publisher:

Elsevier

Language:

English

Submitter:

Igor Maria Villa-Toscani

Date Deposited:

18 Jun 2019 14:42

Last Modified:

23 Oct 2019 07:02

Publisher DOI:

10.1016/j.palaeo.2018.08.013

BORIS DOI:

10.7892/boris.129762

URI:

https://boris.unibe.ch/id/eprint/129762

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