TAPHONOMY OF FOSSIL TURTLES FROM THE LOWERMOST NAVESINK FORMATION (MAASTRICHTIAN) IN MONMOUTH COUNTY, NEW JERSEY

Fossil turtle carapace and plastron fragments representing the families Trionychidae and Toxochelyidae occur as rare constituents of the lowermost Navesink Formation (Maastrichtian) in Monmouth County, New Jersey. These turtle fossils co-occur with skeletal remains of other reptiles, chondrichthian and osteichthian teeth, mollusks, and decapod crustaceans, as a macrofossil residuum within a prominent lag deposit in the lower part of the Navesink Formation. This lag occurs directly above a type two disconformity separating the Marshalltown and Navesink Depositional Sequences and reflects third order, regressive-transgressive sea level cyclicity of Global Sea Level Cycles UZA 4.3-4.4 of Haq et al. 1988. The rarity and fragmentary nature of these turtle fossils, and the fact that they derive from species having disparate habitat preferences, suggest a complex taphonomic history that is the result of extensive reworking of the upper Wenonah-Mt. Laurel sediments and mixing and subsequent re-deposition of this older material during early Navesink time. Turtles and other macrofossils that occur directly above the contact between these formations thus represent animals of upper Campanian to lower Maastrichthian age.