- Rutgers, Earth and Planetary Sciences, New Brunswick, United States of America (am2966@eps.rutgers.edu)
We present findings from the first academic high-resolution, high-density (3.125x6.25 m line spacing) conventional 3D seismic reflection data (550 km2) acquired on the shallow New Jersey continental shelf. This dataset enables us to identify and describe geomorphological evidence of coastal and marine processes during the Miocene. By combining seismic geomorphological analysis (performed on 3D data in map view) with quantitative geometric analysis of clinoforms (performed on 2D seismic profiles), we examine the interplay between change in margin architecture and dominant processes during major climatic perturbations, including the Miocene Climate Optimum (MCO, 17 - 13.8 Ma), and subsequent global cooling during the Middle Miocene Climate Transition (MMCT, ca. 13.8-12.8 Ma).
Our analysis shows that during the pre-MCO, clinoforms exhibited moderate lateral shifts of rollover points basinward (up to ~7 km; up to 6 km/Myr) with mostly flat clinoform rollover trajectories. Sediment thicknesses were similar on clinoform topsets and bottomsets. During the MCO, clinoforms transitioned to high aggradation-to-progradation ratios with steep rollover trajectories. In stark contrast, the MMCT and post-MMCT intervals are marked by rapid dramatic progradation (up to 35 km in 0.4Myr) and flat to falling rollover trajectories. During the MMCT, sediments primarily bypassed the topset domain. Topsets of the post-MMCT interval are, however, thick and are associated with relatively small-scale, low-angle clinoforms that we interpret as subaerial delta fronts.
Surprisingly, we have not detected signs of subaerial exposure, such as incised valleys, fluvial or tidal channels, barrier islands and beaches, etc., during the pre-MCO, the MCO, and the MMCT intervals. The first signs of subaerial exposure appeared ~12 Ma, where we identified remnants of meander bends within a NNW-SSE-trending channel belt. This channel belt appears to be truncated by an overlying fluvial system trending NW-SE comprising relatively narrow (~20-120 m), up to ~10-12 m deep anastomosing, low-sinuosity channels. The NW-SE fluvial system also cuts through a series of >10 km-long, tens-of-meters-wide, closely spaced, parallel linear to arcuate, positive-relief features. We interpret these as beach ridges that formed on the regressive coast (as opposed to the Holocene transgressive New Jersey coast). Our seismic analysis suggests the Lower to Middle Miocene paleoshelf topsets remained submerged until at least the late Middle Miocene (ca. 12 Ma) following the MMCT and drop in global mean geocentric sea level, which resulted in major shifts in shelf processes and stratal architecture.
How to cite: Mukhatzhanov, A., Mountain, G., Miller, K., and Browning, J.: Miocene coastal and shelf processes inferred from the geomorphological analysis of 3D seismic reflection data offshore New Jersey, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13468, https://doi.org/10.5194/egusphere-egu25-13468, 2025.