Trace Fossil Assemblages of Upper Cretaceous Sand Units, Delaware and New Jersey: ABSTRACT

Abstract

End_Page 694------------------------------Siliciclastic formations of Upper Cretaceous age on the Delaware-New Jersey coastal plain contain diverse trace fossil assemblages. When used with physical sedimentary structures and textural data, the assemblages can differentiate intertidal and shallow subtidal depositional environments. Most close modern analogs can be recognized for the Cretaceous trace makers. The Englishtown Formation (Campanian) crops out along the C & D Canal in Delaware. The basal part of the unit is characterized by mottling due to dense concentrations of gently meandering, essentially horizontal Planolites burrows outlined by rims of dark organic-rich material. Other zones are mottled primarily by small-diameter branched shafts of Chondrites. Clumps of quartz sand-lined tubes of Terebellina are dispersed throughout. These tubes have gently curved shafts which form tunnels with distinctive feeding-probe structures at their distal ends. At the top of the unit, the assemblage is dominated by stacked Ophiomorpha nodosa systems with basal mazes. Also present are several types of Chondrites, which commonly surround and/or infest the walls of Ophiomorpha shafts, and deli ate Skolithos shafts. In New Jersey, the Wenonah Formation, Mt. Laurel Formation, and Shrewsbury Member of the Red Bank Formation (all Maestrichtian) each contain a distinctive trace fossil assemblage. The Wenonah Formation is characterized by Cylindrichnus, large concentrically laminated, subvertical, and tapering clay tubes. The Mt. Laurel Formation exhibits two facies, one characterized by small-diameter Ophiomorpha shafts and associated Chondrites forms and the other containing an Ophiomorpha, Chondrites, Skolithos, and Cylindrichnus assemblage. Large-diameter Ophiomorpha nodosa systems and associated Chondrites characterize sands of the Shrewsbury Member of the Red Bank Formation. The trace fossil assemblages and primary sedimentary characteristics suggest the following depositional environments: Englishtown Formation, shallow subtidal shoals transitional to lower foreshore; Wenonah Formation, subtidal, inner shelf; Mt. Laurel Formation, shoreface and transition zones to shallow shoal complex; and Shrewsbury Member of Red Bank Formation, offshore bar complex. End_of_Article - Last_Page 695------------