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Abstract

Integrated Ocean Drilling Program Expedition 313 continuously cored uppermostEocene to Miocene sequences on the New Jersey shallow shelf (Sites M27, M28, and M29). Previously, 15 Miocene (ca. 23-13 Ma) seismic sequence boundaries were recognized on several generations of multichannel seismic profi les using criteria of onlap, downlap, erosional truncation, and toplap. We independently recognize sequence boundaries in the cores and logs based on an integrated study of core surfaces, lithostratigraphy and process sedimentology (grain size, mineralogy, facies, and paleoenvironments), facies successions, stacking patterns, benthic foraminiferal water depths, downhole logs, core gamma logs, and chronostratigraphic ages. We use a velocitydepth function to predict the depths of seismic sequence boundaries that were tested by comparison with major core surfaces, downhole and core logs, and synthetic seismograms. Using sonic velocity (core and downhole), core density, and synthetic seismograms, we show that sequence boundaries correspond with acoustic impedance contrasts, although other stratal surfaces (e.g., maximum fl ooding and transgressive surfaces) also produce refl ections. Core data are suffi cient to link seismic sequence boundaries to impedance contrasts in 9 of 12 instances at Site M27, 6 of 11 instances at Site M28, and 8 of 14 instances at Site M29. Oligocene sequences have minimal lithologic and seismic expression due to deep-water locations on clinoform bottomsets. Miocene sequences (ca. 23-13 Ma) were sampled across several unconformity clino-thems (prograding units) on topset, foreset, and bottomset locations. Excellent recovery allows core-seismic integration that confi rms the hypothesis that unconformities are a primary source of impedance contrasts. Our core-seismic-log correlations predict that key seismic surfaces observed in other sub surface investigations without core and/or well logs are stratal surfaces with sequence stratigraphic signifi cance.

Sedimentology, Stratigraphic Context, and Implications of Miocene Intrashelf Bottomset Deposits, Offshore New Jersey

“…Sequence boundaries are recognized on seismic reflection profiles by reflector terminations: onlap, erosional truncation, downlap, and toplap Mitchum et al, 1977). Seismically interpreted sequence boundaries correlate well with sequence boundaries recognized on the basis of physical stratigraphy and sedimentological character in the Expedition 313 cores, indicating that impedance contrasts across changes in stratal patterns are indicative of sequence boundary locations (Miller et al, 2013b;Fig. 3).…”

“…3) was ~50, ~100, and ~100 m, respectively (Kominz et al, 2016), with calculated foreset gradients of 0.5°, 0.7°, and 0.8°, respectively. Two-dimensional backstripping also shows that the Late Cretaceous to Miocene structural continental shelf break was at several hundred meters water depth, well seaward (>75 km) of these clinothems (Steckler et al, 1999;Mountain et al, 2010;Miller et al, 2013b, Kominz et al, 2016. Therefore, the seaward progradation of the Miocene clinothems was entirely confined to the continental shelf.…”

“…23-13 Ma) seismic sequence boundaries were recognized in profiles and correlated to the IODP Expedition 313 sites using a velocity-depth function developed from stacking velocities of nearby profiles (Mountain et al, 2010;Mountain and Monteverde, 2012;Miller et al, 2013a). The reflection seismic data have a vertical resolution of ~5 m, and were shot by the R/V Oceanus cruise Oc270 in 1995 with a 48-channel generator injector gun and HiRes (http:// www .seimaxtech .com/) equipment (Miller et al, 2013b). Sequence boundaries are recognized on seismic reflection profiles by reflector terminations: onlap, erosional truncation, downlap, and toplap Mitchum et al, 1977).…”

“…Expedition 313 results showed 25 regionally mapped Oligocene to Miocene seismic surfaces that correlate to abrupt sedimentary facies changes in the coreholes (Mountain et al, 2010;Miller et al, 2013b). Sequences were dated with a resolution of ±0.25 to ±0.5 m.y.…”

“…1), bounded by surfaces with a distinct sigmoidal (clinoform) geometry (e.g., Vail, 1987;Van Wagoner et al, 1987) are termed clinothems (e.g., Rich, 1951;Plink-Björklund and Steel, 2002;Johannessen and Steel, 2005;Miller et al, 2013aMiller et al, , 2013b. Depending on the geological setting and data sets examined, clinothem-bounding surfaces can be maximum flooding surfaces (Carvajal and Steel, 2006) or sequence boundaries (Miller et al, 2013a).…”