TEXTURAL TRENDS REFINE THE LITHOSTRATIGRAPHY OF A BIOTURBATED MARINE K-PG INTERVAL, RANCOCAS CREEK, NEW JERSEY

Recently reported findings from the marine glauconite-rich K-Pg succession at the Rancocas Creek site (Medford, New Jersey) presented textural evidence that supports the use of a lithologic shift as a formational boundary between the Navesink (NF) and Hornerstown (HF) Formations. Traditionally based on an observable color change in outcrops (= 0 cm reference), the NF/HF contact has implications for constraining the K-Pg event boundary and associated thanatocoenosis along the Atlantic Coastal Plain. This study presents a new granulometric and low-field magnetic susceptibility (MS) dataset from an adjacent outcrop that spans the formational boundary and extends the textural trends up-section into the Paleogene deposits. A 5-cm point sampling was used to differentiate between Thalassinoides isp. burrow fill and the enclosing matrix. Within the matrix, the following sand-fraction shift occurs ~15 cm above the color change: 1) 12% reduction in median grain size; 2) 11% improvement in sorting; 3) 44% decrease in skewness (slightly more negative in skewness than the NF, possibly due to increased glauconite maturity and content) and 4) 14% increase in MS values. These trends confirm the affinity of HF matrix and NF burrow fill and support the placement of the formational contact at +15 cm. Applications of similar integrated approach at other K-Pg localities along the New Jersey Coastal Plain, both along and across the depositional gradient, will aid regional lithostratigraphic correlation.