Expedition 313 summary

Abstract

Integrated Ocean Drilling Program (IODP) Expedition 313 to the New Jersey Shallow Shelf off the east coast of the United States is the third IODP expedition to use a mission-specific platform. It was conducted by the European Consortium for Ocean Research Drilling (ECORD) Science Operator (ESO) between 30 April and 17 July 2009, with additional support from the International Continental Scientific Drilling Program (ICDP). There were three objectives: (1) date late Paleogene-Neogene depositional sequences and compare ages of unconformable surfaces that divide these sequences with times of sea level lowerings predicted from the δ 18 O glacio-eustatic proxy; (2) estimate the corresponding amplitudes, rates, and mechanisms of sea level change; and (3) evaluate sequence stratigraphic facies models that predict depositional environments, sediment compositions, and stratal geometries in response to sea level change. We drilled at three locations in around 35 m of water 45-67 km offshore, targeting the topsets, foresets, and toesets of several clinoforms at 180-750 meters below seafloor (mbsf). Seismic correlations to previously drilled holes on the continental slope and extrapolations of depths to key horizons in wells drilled into the adjacent coastal plain suggest the clinoform structures investigated during Expedition 313 were deposited during times of oscillations in global sea level; however, this needs to be determined with much greater certainty. The age, lithofacies, and core-log-seismic correlations provided by drilling at key locations will yield the data needed for a rigorous evaluation. We attempted 612 core runs with 80% recovery totaling 1311 m in length. Some or all of the upper 180-280 m of sand-prone sediment was drilled without coring. The deepest hole (M0029A) reached 757 mbsf, and the oldest sediment recovered was late Eocene (Hole M0027A). Wireline logs gathered spectral gamma ray, resistivity, magnetic susceptibility, sonic, and acoustic televiewer data; a vertical seismic profile was run at each site. Multisensor core logger (MSCL), natural gamma ray, and thermal conductivity measurements were made on all cores prior to splitting. Aided by physical properties of discrete samples measured onshore, we have established preliminary corelog-seismic ties with depth uncertainties typically ±7 m or less. We are confident that further study will narrow this range and firmly link facies successions to as many as 16 surfaces and/or sequence-bounding unconformities mapped in the regional seismic grid. Eight lithologic units are recognized that contain important Expedition 313 summary 1 Expedition 313 Scientists 2 Chapter contents

High-resolution correlations of strata within a sand-rich clinothem using grain fabric data, offshore New Jersey, USA

“…At Site M28, sequence m5.4 (151.30 m thick; 512.30-361.00 mcd) is bounded by two high-amplitude reflectors (m5.4 and m5.3) and has been recognized in previous studies (Monteverde et al, 2008;Mountain et al, 2010;Miller et al, 2013aMiller et al, , 2013b based on termination styles of seismic reflectors at its base and top. Two alternative bases of sequence m5.4 were proposed by Mountain et al (2010) at 495.20 mcd, where a thin sand bed overlies a clayey silt, and by Hodgson et al (2018) at 519.70 mcd, where a sharp-based sand forms a fining-upward package of stratified sands with a deeply burrowed basal contact.…”

“…At site M27, the basal sequence boundary of m5.4 is placed at 295.01 meters composite depth (mcd) at an erosional surface (Miller et al, 2013a), which has been tied to synthetic seismogram data (Miller et al, 2013b). Originally, the m5.4 sequence boundary was placed at 271.23 mcd by Mountain et al (2010). This surface was subsequently suggested by Miller et al (2013a) .…”

“…This surface was subsequently suggested by Miller et al (2013a) . The placement of the overlying m5.3 sequence boundary is equivocal and has been placed at 236.15 mcd (Mountain et al, 2010), 249.76 mcd (Miller et al, 2013b), and 256.19 mcd (Miller et al, 2013a). The 256.19 mcd sequence boundary placement was favored by Miller et al (2013a) due to core expression, where a strongly bioturbated contact separates silt from an overlying coarse glauconite sand; this placement was also followed by Hodgson et al (2018) and Proust et al (2018).…”

“…Paleoenvironmental interpretations were based on the following: (1) a classic wave-dominated shoreline model (e.g., Reineck and Singh, 1972;McCubbin, 1982;Browning et al, 2006), which recognizes upper shoreface (0-5 m), lower shoreface (5-10 m), offshore transition (10-30 m), and offshore environments (>30 m); and (2) mixed river/wave delta facies models (e.g., Galloway, 1975;Bhattacharya and Walker, 1992). These have been summarized in Mountain et al (2010) and Proust et al (2018).…”

“…Surface 2 is associated with an overlying fining in mean grain size and the disappearance of the coarse sand fractions. Surface 1 corresponds with the placement of the original m5.4 surface identified in Mountain et al (2010) at 495.20 mcd, where a thin sand bed overlies a clayey silt. Grain-size trends overlying surface 2 show two fining-upward packages (495.00-459.95 and 459.94-432.00 mcd), which are overlain by a package of fine sand (432.00-415.00 mcd) that terminates at surface 3 (415.00 mcd; this study).…”