Miocene relative sea level on the New Jersey shallow continental shelf and coastal plain derived from one-dimensional backstripping: A case for both eustasy and epeirogeny

Abstract

Onshore drilling by Ocean Drilling Program (ODP) Legs 150X and 174AX and offshore drilling by Integrated Ocean Drilling Program (IODP) Expedition 313 provides continuous cores and logs of seismically imaged Lower to Middle Miocene sequences. We input ages and paleodepths of these sequences into one-dimensional backstripping equations, progressively accounting for the effects of compaction, Airy loading, and thermal subsidence. The resulting difference between observed subsidence and theoretical thermal subsidence provide relative sea-level curves that reflect both global average sea level and non-thermal subsidence. In contrast with expectations, backstripping suggests that the relative sea-level maxima in proximal onshore sites were lower than correlative maxima on the shelf. This requires that the onshore New Jersey coastal plain has subsided relative to the shelf, which is consistent with models of relative epeirogeny due to subduction of the Farallon plate. These models predict subsidence of the coastal plain relative to the shelf. Although onshore and offshore sea-level estimates are offset by epeirogeny, the amplitude of million-year-scale Early to Middle Miocene sea-level changes seen at the New Jersey margin is generally 5-20 m and occasionally as great as 50 m. These events are interpreted to represent eustatic variations, because they occur on a shorter time frame than epeirogenic influences. Correction for epeirogenic effects largely reconciles differences between onshore and offshore relative sea-level estimates and suggests that backstripping provides a testable eustatic model for the Early to Middle Miocene.

Closing an early Miocene astronomical gap with Southern Ocean δ18O and δ13C records: Implications for sea level change

“…Though there is minimal temporal overlap with the late early to middle Miocene backstripped eustatic estimates derived from the Marion and Queensland Plateaus [ John et al ., , ], it is important to note that they obtained similar amplitudes (~20–50 m) for Myr‐scale Miocene sea level changes. Backstripped sea level estimates from the Marion‐Queensland, onshore New Jersey [ Miller et al ., ; ], and offshore New Jersey [ Kominz et al ., ] are similar to our δ 18 O‐Mg/Ca estimates (Figure ). These contrast sharply with previously reported estimates of over 100 m of sea level change for this time interval (e.g., Haq et al ., ).…”

Filter Or Conveyor? Establishing Relationships Between Clinoform Rollover Trajectory, Sedimentary Process Regime, and Grain Character Within Intrashelf Clinothems, Offshore New Jersey, U.S.A.

“…The three cores (M27, M28 and M29) intersect topset, foreset and bottomset deposits (ca. 12-22Ma) along seismic line Oc270 529 Kominz et al, 2016) (Fig. 2).…”

“…The timings of sequence boundaries have been shown to correlate with major positive excursions in the 18 O deep-sea record, suggesting that observed changes in relative sea-level (~5-20 m) are predominantly controlled by sea-level variations of allogenic origin, resulting from the waxing and waning of Antarctic ice sheets Kominz et al, 2016).…”

Miocene Glacial Dynamics Recorded by Variations in Magnetic Properties in the ANDRILL‐2A Drill Core

“…Present understanding of Miocene glacial history of Antarctica relies in large part on benthic carbon and oxygen isotope records from deep-sea records, which indicate a highly dynamic glacial environment (e.g., Holbourn et al, 2014Holbourn et al, , 2015Holbourn et al, , 2018Lear et al, 2004;Liebrand et al, 2017;Miller et al, 1991;Shevenell et al, 2008;Zachos et al, 2001). Additional far-field evidence of ice sheet history comes from sequence stratigraphic records on passive continental margins such as Marion Plateau, Australia, and the New Jersey margin, USA, which indicate that sea-level varied up to 100 m, from −60 to +40 m (e.g., John et al, 2011;Kominz et al, 2008Kominz et al, , 2016Miller et al, 1996). Direct evidence of how the ice sheet responded under different climate setting comes from near-field geological records (Antarctic coastal margin), but these records are difficult to obtain because of extensive ice coverage (e.g., Barrett, 1986Barrett, , 1989Barrett et al, 2000Barrett et al, , 2001Hambrey & Barrett, 1993;Hambrey & Wise, 1998;Harwood et al, 2009;Naish et al, 2007).…”