Lithostratigraphy and clay mineralogy of Paleocene-Eocene Thermal Maximum sediments at Wilson Lake, NJ

The Marlboro Formation is an almost exclusively fine-grained and highly kaolinitic unit deposited during the Paleocene-Eocene Thermal Maximum (ca. 56 Ma). It presents a unique opportunity to study an exceptionally thick carbon isotope excursion and continental shelf sedimentation during a geologically brief episode of global warming. Moreover, the dominantly clayey-silt lithology is traceable over hundreds of kilometers within the Mid-Atlantic Coastal Plain physiographic province and has been drilled at numerous locations. Here, I report lithologic changes within the Marlboro Formation from a corehole at Wilson Lake, NJ to ascertain the environment of deposition and its implications for the isotopic record. Using differences in bedding character, quantified clay mineral identification, fine and coarse fraction grain size analysis, and core scanning x-ray fluorescence of major elements, I show that subtle facies changes are consistent with a shoaling depocenter that is aggrading above a modern shelf clinoform rollover.;Previous work has identified the continental shelf adjacent to the Amazon River as a possible analog for the sedimentary environment of the Marlboro Formation. Sedimentary processes and the morphology of the Amazon shelf may be similar to those that produced the Marlboro Formation. Enhanced physical weathering and continental runoff are inferred from the clay mineralogic changes in the PETM section, and are consistent with the PETM climate. Furthermore, the Amazon experiences high rates of deposition in excess of those hypothesized for the New Jersey shelf. Particular clay minerals are also used to demonstrate increased sedimentation rates by measuring the extent of alteration caused by seawater. Rhythmic beds that have previously been interpreted as annual layers based on the periodic cycles in stable isotopes are here interpreted as sediment gravity flow deposits caused by wave-enhanced mud suspensions (fluid mud) like those documented on mud-rich shelves worldwide. The depositional model put forward here supports the extremely rapid onset to the carbon isotope excursion that has been proposed in the shallow marine environment.