The Prospect of Compact Estuarine Lagerstätten

Abstract

A thin, laterally restricted but exceptionally fossiliferous clay lens–informally dubbed the Ingersoll shale–within the Upper Cretaceous Eutaw Formation, eastern U.S. Gulf coastal plain, provides insights regarding the origins of a class of fossil conservation lagerstätten we call compact estuarine lagerstätten (CELs).The Ingersoll shale accumulated in a restricted channel wherein preservation of a diverse paleoflora, amber with fossil inclusions, and feathers was favored by rapid tidal deposition of clay-rich carbonaceous sediments, anoxic pore waters, early diagenetic pyrite mineralization, and perhaps microbial sealing and/or replacement.Although potentially easily overlooked, similar compact lagerstätten formed by comparable taphonomic factors may be common in other estuarine successions. Exploration for additional CELs, guided by sequence stratigraphic principles, may yield other small but spectacular glimpses of life in the past.