Proceedings of the Ocean Drilling Program 174A Initial Reports

Austin, Julian; Christie‐Blick, Nicholas; Malone, M.J.

doi:10.2973/odp.proc.ir.174a.1998

Cited by 245 publications

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“…Oc270 Line 529 collected remarkably improved images of features imaged in Ew9009 line 1003 (Fig. 2) across the shelf, although the Oc270 grid focused on the outer continental shelf subsequently drilled by ODP Leg 174A (Austin et al, 1998).…”

Section: Seismic Interpretationmentioning

confidence: 99%

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et al. 2013

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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.

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Section: Seismic Interpretationmentioning

confidence: 99%

“…In many cases, sequence boundaries on the slope are expressed as the base of slightly coarser grained sediment transported during sea-level lowstands. Leg 174A drilled primarily upper Miocene sequences at outer continental sites on either side of clinoform rollovers, but there was poor recovery in sands (Austin et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

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“…1) allowed planning a transect of coreholes across the New Jersey coastal plain, shelf, and slope to evaluate the controls on depositional sequences. Ocean Drilling Program (ODP) Leg 150 drilled the continental slope, ODP Leg 174A (Austin et al, 1998) drilled the slope and outer shelf, and ODP Legs 150X and 174AX (Miller et al, 2003) drilled the onshore coastal plain. Sequences beneath the inner continental shelf contain Miocene facies most sensitive to sea-level changes (shoreface to middle neritic environments), but were poorly sampled before Expedition 313.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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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.

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“…Offshore, they form complex systems and their dynamics remain poorly known. Brackish to fresh waters have been found in boreholes several kilometers away from the coastline on the continental shelves and upper slopes (Austin et al, 1998;Hathaway et al, 1979; Scientifi c Committee on Oceanic Research, Land-Ocean Interactions in the Coastal Zone, 2004;Kohout et al, 1977;Malone and Martin, 2000;Manheim and Paull, 1981). In carbonate environments, offshore exploratory drillings have identifi ed fresh waters (salinity < 1 g/L) in deep karstic cavities (Scientifi c Committee on Oceanic Research, Land-Ocean Interactions in the Coastal Zone, 2004;Vernet, 2000).…”

Section: Introductionmentioning

confidence: 99%

Fresh-water and salt-water distribution in passive margin sediments: Insights from Integrated Ocean Drilling Program Expedition 313 on the New Jersey Margin

et al. 2013

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International audienceOn the New Jersey shelf (offshore North America), the presence of pore water fresher than seawater is known from a series of boreholes completed during the 1970s and 1980s. To account for this fresh water, a fi rst hypothesis involves possible present-day active dynamic connections with onshore aquifers, while a second involves meteoritic and/or sub- ice-sheet waters during periods of lowered sea level. Expedition 313 drilled three boreholes on the middle shelf, offering a unique opportunity for the internal structure of the siliciclastic system to be accessed, at scales ranging from the depositional matrix to the continental margin. This enables the stratigraphic architecture to be correlated with the spatial distribution and salinity of saturating fl uids. Expedition 313 revealed both very low salinities (<3 g/L) at depths exceeding 400 m below the seafl oor and evidence for a multilayered reservoir organization, with freshand/ or brackish-water intervals alternating vertically with salty intervals. In this study we present a revised distribution of the salinity beneath the middle shelf. Our observations suggest that the processes controlling salinity are strongly infl uenced by lithology, porosity, and permeability. Saltier pore waters generally occur in coarse-grained intervals and fresher pore waters occur in fi ne-grained intervals. The transition from fresher to saltier intervals is often marked by cemented horizons that probably act as permeability barriers. In the lowermost parts of two holes, the salinity varies independently of lithology, suggesting different mechanisms and/or sources of salinity. We present an interpretation of the sedimentary facies distribution, derived from core, logs, and seismic profi le analyses, that is used to discuss the marginscale two-dimensional reservoir geometry and permeability distribution. These proposed geometries are of primary importance when considering the possible pathways and emplacement mechanisms for the fresh and salty water below the New Jersey shelf

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Proceedings of the Ocean Drilling Program 174A Initial Reports

Cited by 245 publications

References 0 publications

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

Fresh-water and salt-water distribution in passive margin sediments: Insights from Integrated Ocean Drilling Program Expedition 313 on the New Jersey Margin

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