Comptes Rendus Palevol | 2021

Taphonomy of a Panopea Ménard de la Groye, 1807 shell bed from the Pisco Formation (Miocene, Peru)



Invertebrate taphonomy can provide signifi cant information about the post-mortem processes that aff ected the fossil record. In the East Pisco Basin of southern Peru, a Panopea Ménard de la Groye, 1807 shell bed was found in the upper Miocene strata of the Pisco Formation, hinting at a peculiar biostratinomic and diagenetic history. Th is bed contains abundant invertebrate fossil molds cemented by dolomite. Th e specimens of the deep infaunal bivalve, Panopea sp., occur together with bivalves representative of shallow infaunal species (Trachycardium sp. and Dosinia ponderosa [Gray, 1838]) and balanid barnacles, which are sessile encrusters. Th e Panopea specimens host compound molds evidencing an abundant encrusting fauna, including serpulids, ?foraminifera, bryozoans, and barnacles that colonized the inner surfaces of the valves before their fi nal burial. We hypothesize that short-term, storm-related processes exhumed the living bivalves, resulting in a sedimentological concentration of relatively well-preserved shells. After the death of the exhumed bivalves, the inner surfaces of the articulated Panopea shells, representing hard-substratal, sheltered environments on an otherwise unstable sandy seafl oor (i.e., “benthic islands”), were colonized by diff erent encrusting organisms. Following the fi nal burial, dolomite precipitated, cementing the sediment infi ll of the valves. Lastly, a decrease of pH occurred at the sulfate reduction-methanogenesis boundary, inducing the dissolution of the shell carbonate.

Volume 20
Pages 119-140
DOI 10.5852/CR-PALEVOL2021V20A8
Language English
Journal Comptes Rendus Palevol

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