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Article Title

Middle Miocene Pholadid Borings at the Base of the Isidro Formation, Arroyo Mezquital, Baja California Sur, Mexico

Volume

93

Issue

2

First Page

83

Last Page

90

Abstract

Abxxnddinl sediment-infilled clavate (club-shaped) borings, assignable to ichnogenus Gastrochaenolites, are reported from the base of the Miocene Isidro Formation, Baja California Sur, Mexico. The infilled borings were made by pho- ladid bivalves that lived in a nearshore-marine environment on a semi-consoli- dated substrate ("'Glossifungites'' ichnofacies). Some borings are connected by horizontal burrows that are sculptured (Spongeliomorpha) or unsculptured (Tha- lassinoides). The localized pholadid community was short lived and abruptly terminated by an influx of sediment.