Late Quaternary sedimentation off New Jersey: New results using 3-D seismic profiles and cores

Davies, T. G. E.; Austin, James A.; Lagoe, Martin B.; Milliman, John D.

doi:10.1016/0025-3227(92)90203-t

Cited by 73 publications

(61 citation statements)

References 16 publications

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“…Seabed heterogeneity on the New Jersey shelf is strong over these scales; 5 in particular, the AMCOR site is on a sand ridge, whereas the SW06 central site is on the clay-rich outer-shelf sediment wedge. 6 At this SW06 site, seafloor sand is confined to a thin ͑ϳ20 cm͒ winnowed layer 5,7 rather than to a thicker, O͑1͒ m, sand sheet typical of sand ridge sites. 5,6 For these reasons, the initial comparison of our results is limited to the direct in situ measurements of sound speed made within the same 0.3 km radius 8 during SW06.…”

Section: Introductionmentioning

confidence: 94%

“…6 At this SW06 site, seafloor sand is confined to a thin ͑ϳ20 cm͒ winnowed layer 5,7 rather than to a thicker, O͑1͒ m, sand sheet typical of sand ridge sites. 5,6 For these reasons, the initial comparison of our results is limited to the direct in situ measurements of sound speed made within the same 0.3 km radius 8 during SW06. Interpretation and forward modeling of our results are guided by the stratigraphic constraints provided by closely spaced ͑50 m͒ chirp seismic reflection profiles that provide pseudo three-dimensional coverage of the SW06 central site.…”

Section: Introductionmentioning

confidence: 94%

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Observations of the R reflector and sediment interface reflection at the Shallow Water ’06 Central Site

Choi

Dahl

Goff

2008

The Journal of the Acoustical Society of America

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Acoustic bottom-interacting measurements from the Shallow Water ’06 experiment experiment (frequency range 1–20kHz) are presented. These are co-located with coring and stratigraphic studies showing a thin (∼20cm) higher sound speed layer overlaying a thicker (∼20m) lower sound speed layer ending at a high-impedance reflector (R reflector). Reflections from the R reflector and analysis of the bottom reflection coefficient magnitude for the upper two sediment layers confirm both these features. Geoacoustic parameters are estimated, dispersion effects addressed, and forward modeling using the parabolic wave equation undertaken. The reflection coefficient measurements suggest a nonlinear attenuation law for the thin layer of sandy sediments.

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Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 94%

Observations of the R reflector and sediment interface reflection at the Shallow Water ’06 Central Site

Choi

Dahl

Goff

2008

The Journal of the Acoustical Society of America

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“…Buried Pleistocene valleys of the Hudson and Delaware Rivers have indeed been traced across the shelf (Ewing et al, 1963;Twichell et al, 1977;Knebel et al, 1979;Davies et al, 1992), and clearly they once transported sediment to the heads of the Hudson and Wilmington canyons. Daly's (1936) model has been substantiated further by the recovery of turbidites on the Hatteras Abyssal Plain that are similar in composition to the relict sands found near the heads of slope canyons off the mid-Atlantic states (Horn et al, 1971).…”

Section: Introductionmentioning

confidence: 99%

Origin, Reburial, and Significance of a Middle Miocene Canyon, New Jersey Continental Slope

Mountain¹,

Damuth²,

McHugh³

et al. 1996

Proceedings of the Ocean Drilling Program, 150 Scientific Results

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Ocean Drilling Program Site 906 was drilled through a 5-km-wide, buried slope canyon to learn when and how this feature formed, was maintained, and subsequently filled. Seismic profiles show that it is the oldest Neogene canyon in the region, and that it marks the beginning of major slope bypass that continued intermittently to Pleistocene time. Sampling the oldest material within the canyon (pre-reflector m2) to determine the minimum canyon age, and tracing the youngest surface cut by the canyon to a nearby site (reflector m3) to determine the maximum age, shows the canyon formed between 13.5 ± 0.5, and 12.4 ± 0.5 m.y.The first sediment that accumulated within the canyon is a 57-m breccia deposit shed from the adjacent walls; matrix-supported debris flows of similar age and lithology were sampled at Site 905, 52 km southeast at 2800-m water depth on the continental rise. At both sites this material lacks shallow-water sand, and together with the flat (not V-shaped) canyon cross-section cutting into reflector m3 suggests that the canyon formed sometime after 13.5 ± 0.5 m.y. as a result of sediment failure that widened and lengthened the scar during headward erosion. By this process the canyon connected with a sediment source on the adjacent shelf, probably in less than ~0.5 Ma, and 60 m of mostly quartz sand turbidites accumulated above the Site 906 breccia; no equivalent turbidites have been found outside the canyon.Reflector m2 (12.4 ± 0.5 m.y.) is the oldest seismic reflector draping both the canyon and the adjacent slope, and it matches the top of an 82-m unit of laminated siltstone at Site 906. Seismic mapping beneath the upper slope shows this laminated unit completely filled the canyon 5 km landward of Site 906; furthermore, this unit lapped out against the basal breccias and turbidites just 7 km seaward of Site 906, demonstrating the head of the canyon filled first. This left a 250-m high, headless canyon on the middle and lower slope that has subsequently been utilized and completely filled by overlying canyon systems. Younger Miocene canyons seen in nearby profiles reveal a similar history.This evidence emphasizes that sediment failure and headward erosion are important precursors to shelf-edge sands finding a ready conduit to the deep sea. Sea-level fall can thus be a secondary process in slope canyon formation. Because canyons are buried on the upper slope before those on the lower slope, canyon piracy is more common in the latter setting. Consequently, the stratigraphic record of lower slope canyons can be especially complex.

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“…The initial deposition of the outer shelf wedge directly above the "R" reflector consists of finely laminate dipping layers of alternating sandy clay and clay. 26 In the 3-D geoacoustic seabed model, this layer is characterized by a sound speed of 1585 m/s. Cores into the shallower sediment above the erose boundary primarily sampled clay, with occasional sand lenses.…”

Section: Environmental Descriptionmentioning

confidence: 99%

Horizontal refraction of propagating sound due to seafloor scours over a range-dependent layered bottom on the New Jersey shelf

Ballard

Lin

Lynch

2012

The Journal of the Acoustical Society of America

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Three-dimensional propagation effects of low frequency sound from 100 to 400 Hz caused by seafloor topography and range-dependent bottom structure over a 20 km range along the New Jersey shelf are investigated using a hybrid modeling approach. Normal modes are used in the vertical dimension, and a parabolic-equation approximate model is applied to solve the horizontal refraction equation. Examination of modal amplitudes demonstrates the effect of environmental range dependence on modes trapped in the water column, modes interacting with the bottom, and modes trapped in the bottom. Using normal mode ray tracing, topographic features responsible for threedimensional effects of horizontal refraction and focusing are identified. These effects are observed in the measurements from the Shallow Water 2006 experiment. Specifically, signals from a pair of fixed sources recorded on a horizontal line array sitting on the seafloor show an intensification caused by horizontal focusing due to the seabed topography of 4 dB along the array.

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Late Quaternary sedimentation off New Jersey: New results using 3-D seismic profiles and cores

Cited by 73 publications

References 16 publications

Observations of the R reflector and sediment interface reflection at the Shallow Water ’06 Central Site

Observations of the R reflector and sediment interface reflection at the Shallow Water ’06 Central Site

Origin, Reburial, and Significance of a Middle Miocene Canyon, New Jersey Continental Slope

Horizontal refraction of propagating sound due to seafloor scours over a range-dependent layered bottom on the New Jersey shelf

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