Ichnology of the Upper Silurian Wallpack Center Member (Decker Formation), Northwestern New Jersey

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Upper Silurian deposits of light to medium gray, interbedded calcareous sandstones, quartzose limestones, and calcareous siltstones comprising the type section of the Wallpack Center Member of the Decker Formation (Upper Silurian), Wallpack Center, New Jersey, have yielded a moderate variety of trace fossils. The greatest diversity and abundance of trace fossils occurs on the soles of calcareous sandstones underlain by thin siltstones, interbedded with thin quartzose limestones. Specimens of Cruziana isp., Diplichnites isp., Lockeia siliquaria, Palaeophycus herberti, Planolites beverleyensis, Protovirgularia rugosa, and bilobate trails reflect horizontal feeding, crawling, and dwelling traces, The traces compare favorably to the Cruziana ichnofacies. Fossils include largely crinoid columnal debris and brachiopods, as well as bryozoa and coral fragments. The shelly fossils on these units and the trace fossils are indicative of a shallow marine environment. Overall, tracemaking occurred during moderate to low energy levels, punctuated by periodic, higher energy (likely storm) conditions. In contrast, the Skolithos ichnofacies consists of vertically oriented feeding burrows of Skolithos verticalis within light to medium gray calcareous sandstones as well as thin calcareous siltstones. Fossils include abundant coral fragments, bryozoa, brachiopods, and crinoid columnals. The Skolithos ichnofacies records somewhat limited exploitation by opportunistic suspension feeders in a shallow marine environment, during higher energy conditions.

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Northeastern Geology and Environmental Sciences

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