The Trace Fossil Assemblage of a Cretaceous Nearshore Environment: Englishtown Formation of Delaware, U.S.A.
H. Allen Curran, 1985. "The Trace Fossil Assemblage of a Cretaceous Nearshore Environment: Englishtown Formation of Delaware, U.S.A.", Biogenic Structures: Their Use in Interpreting Depositional Environments, H. Allen Curran
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Trace fossils are abundant and extremely well-preserved in the unconsolidated, siliciclastic sediments of the Late Cretaceous Englishtown Formation exposed along the Chesapeake and Delaware Canal in Delaware. The trace fossil assemblage is characteristic of a nearshore environment and can be divided into two subassemblages. The upper part of the formation is dominated by densely packed Ophiomorpha nodosa shafts and tunnels, Skolithos linearis, and a delicate branching burrow that forms vertical polygonal nets. The subassemblage that characterizes the middle and lower parts of the sequence consists of Macaronichnus segregatis and a Skolithos-like form, both of which created mottled horizons, isolated O. nodosa shafts and tunnels, Schaubcylindrichnus coronus, and probable echinoid burrows. Each trace fossil taxon is described, and modern tracemaker analogs are discussed to enable further interpretation of the trace fossils and their paleoenvironmental significance. The Englishtown Formation is interpreted to have been deposited in a prograding nearshore environment with a low energy, O. nodosa-dominated, upper shoreface—lower foreshore zone similar to parts of the modern shallow-water Sea Isles coast of Georgia.
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Organisms of one sort or another today inhabit virtually every sediment environment on Earth, and the rock record tells us that this has been the case through the greater part of our planet’s history. Furthermore, organisms leave their mark in most sedimentary settings, either directly in the form of body fossils or indirectly as biogenic structures. In addition to their often profound modifying effects on substrates, ancient biogenic structures preserve a record of organism behavioral activity in response to substrate and other paleoenvironmental controls. Thus, biogenic structures can be highly useful as facies indicators and can provide valuable clues to the interpretation of paleodepositional environments. The purpose of this volume is to present a broad spectrum of case-book examples of the use of biogenic structures in the interpretation of depositional environments.