81-8 Eocene Sequences and Forward Modeling of the New Jersey Coastal Plain, USA: Changing Depositional Styles in Response to Climate and Sea Level

Session: Investigating Earth’s History With Continental Scientific Drilling

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Paleogene to Neogene evolution of the U.S. mid-Atlantic margin is revealed by corehole arrays and 1-D and 2-D modelling. We map the spatial and temporal distribution and depositional environments of Eocene sequences and formations in the New Jersey Coastal Plain, USA, using an array of coreholes and gamma logs. On this passive margin, Eocene depositional systems reflect a change from prograding earliest Eocene mud lobes, to Early to Middle Eocene hemipelagic ramp, and finally to late Middle Eocene prograding sandy sequences. The Marlboro Clay, containing the Paleocene/Eocene Thermal Maximum (PETM), was deposited as prograding fluid mud during times of high global temperatures; it is found in northern and southern lobes but is absent from the central coastal plain. Lower and lower Middle Eocene sediments consist of carbonate rich-clays deposited in middle to outer neritic (50-150 m) paleodepths on a hemipelagic ramp during a peak in global mean sea level. The upper Middle to Upper Eocene consists of three prograding lithologic units found in parallel belts with coarse-grained sediments in the most updip positions and fine-grained sediments found in the most downdip positions; the lithologic units transgress time and sequences. Comparison of the timing of sea-level falls constructed using oxygen isotopes with New Jersey Eocene sequence boundaries shows a correlation between sequences boundaries and global mean sea-level falls controlled by ice-volume changes, even in the purportedly ice-free Early Eocene. We date the change from ramp to prograding sequences to the late Middle Eocene (ca. 41.5 Ma). We use a forward stratigraphic model to evaluate the primary controls influencing changing styles of sedimentation on the Eocene New Jersey margin. Using a forward stratigraphic model we show the appearance of prograding sands and silts in the Middle Eocene is a response primarily to changes in siliciclastic input, presumably due to climate or tectonics in the hinterland. Our study of the New Jersey Eocene shows that by integrating stratigraphic and chronostratigraphic data with an independent estimate of global mean geocentric sea level, our forward model was able to disentangle the effects of sea level and sediment supply on the stratigraphic record.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10150

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