A PALEONTOLOGICAL ANALYSIS OF SAND PODS AT THE BASE OF THE NAVESINK FORMATION, BIG BROOK, MONMOUTH COUNTY, NJ

The Upper Cretaceous stratigraphic sequence of the Wenonah, Mount Laurel and Navesink Formations exposed in Big Brook, northeastern Monmouth County, NJ has been highly debated. Sandy concretions (“sand pods”) occur at the base of the Navesink Fm. The sand pods are commonly fossiliferous, 4 to 16 cm in diameter and composed mostly of fine to medium, glauconitic quartz sand. These concretions are unique to northeastern Monmouth County occurring locally within a 30 cm horizon just above the unconformity bounding the Navesink Fm and the Wenonah Fm. A faunal and sedimentological analysis was conducted. Twenty-two different species were identified including Neithea quinquecostata and Anomia tellinoides, commonly associated with the Mount Laurel Fm. The concretions are interpreted as remnants of the Mount Laurel Fm within a lag deposit at the base of the Navesink Fm resulting from shoreface retreat. Ammonite biostratigraphy suggests this is likely related to a late Campanian to early Maastrichtian transgressive event.