Chronology of Eocene-Miocene sequences on the New Jersey shallow shelf: Implications for regional, interregional, and global correlations

Abstract

Integrated Ocean Drilling Program Expedition 313 continuously cored and logged latest Eocene to early-middle Miocene sequences at three sites (M27, M28, and M29) on the inner-middle continental shelf offshore New Jersey, providing an opportunity to evaluate the ages, global correlations, and signifi cance of sequence boundaries. We provide a chronology for these sequences using integrated strontium isotopic stratigraphy and biostratigraphy (primarily calcareous nannoplankton, diatoms, and dinocysts [dinofl agellate cysts]). Despite challenges posed by shallowwater sediments, age resolution is typically ±0.5 m.y. and in many sequences is as good as ±0.25 m.y. Three Oligocene sequences were sampled at Site M27 on sequence bottomsets. Fifteen early to early-middle Miocene sequences were dated at Sites M27, M28, and M29 across clinothems in topsets, foresets (where the sequences are thickest), and bottomsets. A few sequences have coarse (~1 m.y.) or little age constraint due to barren zones; we constrain the age estimates of these less well dated sequences by applying the principle of superposition, i.e., sediments above sequence boundaries in any site are younger than the sediments below the sequence boundaries at other sites. Our age control provides constraints on the timing of deposition in the clinothem; sequences on the topsets are generally the youngest in the clinothem, whereas the bottomsets generally are the oldest. The greatest amount of time is represented on foresets, although we have no evidence for a correlative conformity. Our chronology provides a baseline for regional and interregional correlations and sea-level reconstructions: (1) we correlate a major increase in sedimentation rate precisely with the timing of the middle Miocene climate changes associated with the development of a permanent East Antarctic Ice Sheet; and (2) the timing of sequence boundaries matches the deep-sea oxygen isotopic record, implicating glacioeustasy as a major driver for forming sequence boundaries.

Plants in movement – Floristic and climatic characterization of the New Jersey hinterland during the Palaeogene–Neogene transition in relation to major glaciation events

“…Downslope mass transport is not expected to be a major factor at Site M0027 prior to the transgression of the shelf break within sedimentary Unit 6/sequence m5.8 (Fig. S1), except during glacioeustatic lowstands -then the ratio of terrestrial vs. marine palynomorphs 10 ("P:D") helps identify resedimentation (McCarthy et al, 2013).…”

“…Because the palaeo-shelf break only transgressed the Site M0027 during the Early Miocene (McCarthy et al, 2013) dominance of bisaccate grains is expected, reflecting their preferential transport in wind and water (McCarthy et al, 2003).…”

“…1). Site M0027 is the only of three recovered sites containing Oligocene sequences (Browning et al, 2013;Miller et al, 2013aMiller et al, , 2013b). …”

“…The age model is based on calcareous nannofossils, dinoflagellate cysts, planktic diatoms, Sr isotopes, and sequence stratigraphy (Browning et al, 2013;Miller et al, 2013a). The analysed core sediments comprise four sequences, which 20 correlate with sea level high stands, while no sediments were deposited during sea-level lowstands (likely connected to glacial phases).…”

“…The recovered deposits contain generally well preserved marine and terrestrial palynomorphs. Furthermore, a robust age model (Browning et al, 2013) was developed for these cores. Kotthoff et al (2014) gave an overview of the OMB, including the related Mi-1 cooling event indicated by temperature decline and conifer expansion.…”