Modeling of the New Jersey Continental Shelf in the Miocene: Insights into Sedimentation Processes, Sea-level change, and Climate

Global mean sea level is rising today at approximately 3.4 mm/year and accelerating, though it is unclear how processes of sinking of the land and sediment input to the coasts influence the impact of sea-level rise on ancient, modern, and future shorelines. This research will improve knowledge of how local processes drive observed sea-level variations on continental margins in general, and at the US mid-Atlantic margin in particular.

The investigators will combine information from sediment samples, high-resolution subsurface imaging, and modeling to evaluate global, regional, and local impacts on the stability of shorelines in a changing world. Broader impacts include support for two Early Career Researchers and a community workshop. The investigators will continue their long-standing sea-level outreach to students, the public, and stakeholders through research opportunities, teaching, public events, and press interviews.

IODP Expedition 313 drilled, cored, and logged Neogene clinoforms on the New Jersey middle shelf to recover geologic evidence of the impact of changes in sea-level, sediment delivery, and tectonism on shallow water sedimentation. The RV Marcus G. Langseth collected 550 km2 of high-resolution 3D seismic reflection data surrounding these drillsites, placing the cores, logs and previous regional 2D seismic data in a spatial and temporal context.

The current research will apply state-of-the-art imaging to the 3D volume and iteratively match it with 2D forward models of sequence evolution to improve knowledge of how coastlines and shallow shelves evolve in response to changes in sediment supply, global mean sea level and tectonics (including thermal subsidence, flexural response, and mantle dynamic topographic variations). The investigators have proposed three hypotheses: 1) a major increase in sediment supply to the NJ margin began at ca. 13 Ma, significantly widening the shallow continental shelf and sharply changing sequence geometries, facies distributions, and processes of seaward sediment transport; 2) gravity-driven debris flows played a major role in downslope sediment transport before the Middle Miocene Climate Transition (14.8-12.8 Ma), but during and after this interval canyon cutting coupled with channelized flows became the major agent moving sediment to the outer continental shelf and beyond; and 3) global mean sea-level change throughout the Neogene was the dominant process forming sequence boundaries on the Myr to 405 kyr scale, while variations in sediment supply were responsible for changes in sequence geometry and facies distribution.

These hypotheses will be tested by applying 3D seismic imaging techniques in a sequence stratigraphic framework including analyses of seismic attributes to map stratal geometry and facies ground-truthed at the Exp 313 drill sites. The investigators have developed a 2D forward stratigraphic model that simulates deposition of marine siliciclastic sediments on a passive margin in response to parameterized variations in global mean sea level, sediment supply, and subsidence due to thermal cooling, flexure, and compaction.

They will use optimization algorithms applied within a Bayesian framework to yield a probabilistic fit of the model output to the observed stratigraphic record and generate the most likely history of these drivers. This Bayesian inference framework will be used to derive model output values for metrics like shoreline position, which is challenging to measure independently from the underlying data, but can be constrained within the model output by core data and the proposed 3D seismic facies analysis.

Integrating continuously cored and logged drillsites with high-resolution 3D seismic data and forward stratigraphic modeling poses a unique research opportunity. Results will advance understanding of the response of ancient shorelines to changes in sea-level, sediment supply and tectonics and contribute to informed predictions of how these factors will impact coastlines of the future.

This project will support two Early Career Researchers and foster their development as leaders in seismic imaging and stratigraphic modeling used to evaluate the relative effects of change in global mean sea level, deformation of the Earth, and rates of sediment supply on shoreline position. The researchers will run a two-day community workshop on sequence stratigraphy and stratigraphic modeling.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.