⁸⁷Sr/⁸⁶Sr dating of Upper Cretaceous (Campanian and Santonian) depositional sequences: Bass River and Ancora, NJ ODP Leg 174 AX

Abstract

The objective of this study is to date hiatuses associated with unconformities identified in the Campanian and Santonian section in the Ancora and Bass River boreholes using ⁸⁷Sr/⁸⁶Sr dating techniques. Sequence-bounding unconformities were previously identified fin the boreholes (Miller et al., 1998, 1999). This study constrains the younger age of the sequence boundaries at the base of the Navesink Formation at 66.5 Ma. The hiatus between the Navesink and Mt. Laurel Formations is approximately 5 Ma with the age of the older surface dated as 71.5 Ma. Another sequence separates the Marshalltown and the Englishtown Fomations; no detectable hiatus is associated with this boundary that is dated at ~75.0 Ma. The sequence boundary separating the upper and lower Englishtown Formations is dated at ~76.2 Ma. The base of the Merchantville Formation is dated to be 81.7 Ma. This study is significant because three depositional sequence boundaries (Marshalltown/Englishtown, upper/lower Englishtown, base of Merchantville) can be firmly tied to the geomagnetic polarity time scale for the first time.