Stratigraphy Lab Group Projects

We propose to drill three transects of coreholes in the mid-Atlantic U.S. Coastal Plain targeting thick (>10 m) sections of the Paleocene-Eocene Thermal Maximum (PETM), building on drilling in New Jersey by IODP Leg 174AX and Maryland-Virginia by the USGS. Previous drilling has sampled across the paleoshelf from inner neritic to deep neritic (>100 m) paleodepths and has provided important constraints on this major event, but existing cores are either depleted or contain stratigraphic gaps due to the patchwork distribution of the successions, updip dissolution, diagenesis, and the discontinuous nature of coastal zone sedimentation, which can be addressed with new cores. We plan to triple core the sections of interest at ten sites sampling the PETM, targeting the underlying normal shelf deposit of the Vincentown/Aquia Formations, a transitional interval that is expanded in updip sections and contains the Carbon Isotopic Excursion (CIE) onset, and the rapidly deposited Marlboro Clay that records a very thick CIE “core/body”. Though truncated at the top of the Marlboro Clay, very much expanded PETM sections (>10 m versus 1 m in the thickest deep-sea section) are available in this region. We will also core and sample other Eocene hyperthermals and the Cretaceous/Paleogene (K/Pg) boundary at these sites. This project will be an international collaboration with the cores archived by IODP, publication by IODP within two years, and with local logistical and support-in-kind provided by USGS and U.S. state surveys. Coring of three transects will provide new material needed to evaluate CIE initiation and subsequent CIE core/body that provides the clearest geological example of a massive release of carbon analogous to anthropogenic release.

We have studied paleoenvironmental changes across the Paleocene/Eocene boundary in the Millville New Jersey coastal plain core (ODP Leg 174AX). Using two independent temperature proxies (the organic paleothermometer TEX86 and Mg/Ca ratio of planktonic foraminifera) and δ¹⁸O of planktonic foraminifera, we evaluated temperature and salinity changes at Millville (Makarova et al., in prep.). Paleotemperature estimates show warming of 5-7°C across the PETM, though different temperature calibrations provide a broad range of absolute temperatures. The TEXL86 temperature calibration (Kim et al., 2010) is the only one that yields realistic salinities and thus arguably provides the best temperature estimate (warming from 23°C to 30°C). We are currently integrating isotopic records of planktonic (surface and deep dwelling) and benthic foraminifera at Millville and other New Jersey coastal plain cores to reconstruct the water column structure along the New Jersey paleoshelf during the PETM (i.e. changes in surface to deep water temperature gradient, carbon cycle, and oceanic productivity).

We built a cross-shelf Paleocene-Eocene Thermal Maximum (PETM) depositional model for input of muds from the “Appalachian Amazon” where large amounts of fluid mud creating expanded PETM records. New cores from Medford, NJ preserve the carbon isotope excursion (CIE) onset overlain by the lower portion of the CIE “body/core.” We use δ¹³C_bulk, percent CaCO₃, and percent coarse fraction (>63 µm) to correlate Medford with records along a paleoslope dip transect, showing that updip locations preserve expanded sections of the earliest portion of the CIE (the onset) in contrast with downdip locations where the final section of the CIE (the recovery) is preferentially preserved. This pattern implies that the fluid mud was deposited in prograding clinoform foresets. Our subaqueous-clinoform delta model explains the variability of the CIE records and provides a framework for future PETM studies in the region.

Recent studies have focused on the Iridium anomaly in several New Jersey coastal plain outcrops and coreholes (Miller et al., 2010; Esmeray-Senlet, 2015 Ph.D. thesis) and the recovery of planktonic foraminifera and carbon cycle from mass extinction (Esmeray-Senlet et al., 2015). Our data from New Jersey and the deep sea indicate reduced export productivity consistent with the Living Oceans hypothesis, though other studies indicate zones of continued export productivity, prompting us to coin the term Heterogeneous Oceans (Esmeray-Senlet et al., 2015). Ir is associated with the mass extinction event in most sections, though it appears to have migrated downsection at Bass River, and Tighe Park. We continue to explore the relationship between Deccan Trap volcanism, impact, and the mass extinction.