Integrated Continental Margin Research to benefit ocean and Earth sciences

Nittrouer, Charles A.; Kravitz, Joseph H.

doi:10.1029/95eo00060

Cited by 24 publications

(11 citation statements)

References 5 publications

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“…Along the upper shelf, in water depths to 60 m, £uvial muds from the Eel River watershed are mixed with coarse-grained shelf sediments by hydrodynamic turbulence before they are deposited, eroded and redeposited (Nittrouer and Kravitz, 1995;Drake, 1999). On deeper parts of the shelf, where wind and wave action is reduced, a mixture of ¢ne-grained silts and £uvial muds is deposited as a soft sediment body (Wiberg et al, 1996;Wheatcroft et al, 1996Wheatcroft et al, , 1997Go¡ et al, 1996Go¡ et al, , 1999.…”

Section: Geoacoustic Properties Governed By Environmental Factorsmentioning

confidence: 99%

In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

Gorgas

Wilkens

et al. 2002

Marine Geology

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We compared in situ and laboratory velocity and attenuation values measured in seafloor sediments from the shallow water delta of the Eel River, California. This region receives a substantial volume of fluvial sediment that is discharged annually onto the shelf. Additionally, a high input of fluvial sediments during storms generates flood deposits that are characterized by thin beds of variable grain-sizes between the 40-and 90-m isobaths. The main objectives of this study were (1) to investigate signatures of seafloor processes on geoacoustic and physical properties, and (2) to evaluate differences between geoacoustic parameters measured in situ at acoustic (7.5 kHz) and in the laboratory at ultrasonic (400 kHz) frequencies. The in situ acoustic measurements were conducted between 60 and 100 m of water depth. Wet-bulk density and porosity profiles were obtained to 1.15 m below seafloor (m bsf) using gravity cores of the mostly cohesive fine-grained sediments across-and along-shelf. Physical and geoacoustic properties from six selected sites obtained on the Eel margin revealed the following. (1) Sound speed and wet-bulk density strongly correlated in most cases. (2) Sediment compaction with depth generally led to increased sound speed and density, while porosity and in situ attenuation values decreased. (3) Sound speed was higher in coarser-than in finer-grained sediments, on a maximum average by 80 m s 31 . (4) In coarse-grained sediments sound speed was higher in the laboratory (1560 m s 31 ) than in situ (1520 m s 31 ). In contrast, average ultrasonic and in situ sound speed in finegrained sediments showed only little differences (both approximately 1480 m s 31 ). (5) Greater attenuation was commonly measured in the laboratory (0.4 and 0.8 dB m 31 kHz 31 ) than in situ (0.02 and 0.65 dB m 31 kHz 31 ), and remained almost constant below 0.4 m bsf. We attributed discrepancies between laboratory ultrasonic and in situ acoustic measurements to a frequency dependence of velocity and attenuation. In addition, laboratory attenuation was most likely enhanced due to scattering of sound waves at heterogeneities that were on the scale of

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Section: Geoacoustic Properties Governed By Environmental Factorsmentioning

confidence: 99%

In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

Gorgas

Wilkens

et al. 2002

Marine Geology

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“…Eustasy competes with climatic and paleoceanographic variations, tectonism (variable rates of subsidence), rates of sediment supply and submarine current activity to influence relative sea‐level and stratigraphic development and preservation. Reading the stratigraphic record, therefore, requires evaluation of multiple processes (including eustasy) at various temporal and spatial scales (Nittrouer & Kravitz, 1995).…”

Section: Special Issuementioning

confidence: 99%

Pre‐Quaternary sea‐level changes: records and processes

Fulthorpe¹,

Camoin²,

Miller³

et al. 2008

Basin Research

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“…High‐resolution multichannel seismic (MCS) data, collected on the New Jersey continental shelf as part of the Office of Naval Research's STRATAFORM (Strata Formation on Margins) initiative (Nittrouer & Kravitz, 1995, 1996; Austin et al , 1996;Fig. 1), illustrate how geometries of middle–late Miocene clinoformal sequence boundaries (SBs) vary along strike under the presumed influence of local processes.…”

Section: Introductionmentioning

confidence: 99%

“…High-resolution multichannel seismic (MCS) data, collected on the New Jersey continental shelf as part of the O⁄ce of Naval Research's STRATAFORM (Strata Formation on Margins) initiative (Nittrouer & Kravitz, 1995Austin et al, 1996; Fig. 1), illustrate how geometries of middle^late Miocene clinoformal sequence boundaries (SBs) vary along strike under the presumed in£uence of local processes.The New Jersey margin is relatively unique because it has been imaged with MCS systems using di¡erent frequencies; resultant seismic images allow us to evaluate how much sequence interpretations can be in£uenced by varying vertical and horizontal spatial resolution of the seismic data.…”

Section: Introductionmentioning

confidence: 99%

Assessing the significance of along‐strike variations of middle to late Miocene prograding clinoformal sequence geometries beneath the New Jersey continental shelf

Fulthorpe¹,

Austin²

2008

Basin Research

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Seismic mapping of high‐resolution multichannel seismic profiles along the New Jersey margin illustrates how characteristics of middle–late Miocene clinoformal sequence boundaries (SBs) change markedly along strike in presumed response to local depositional and erosional processes. Most SBs converge from SW to NE, in part as a result of the influence of underlying basin morphology on accommodation space, but also in response to differential subsidence and presumed along‐strike variations in sediment supply from the adjacent margin. The curvature of clinoform breaks, historically viewed as marking palaeo‐shelf edges, is variable and such breaks are rarely sharp. Gently curved palaeo‐shelf/slope transitions cannot be assigned precise palaeobathymetric significance and probably instead reflect post‐depositional sediment reworking. The amount of erosional truncation landward of clinoform breaks varies significantly. Documented along‐strike variability in SB morphology occurs, even though middle–late Miocene palaeo‐shelf edges are nearly linear in plan view. Therefore, such linearity cannot be a product of uniform sedimentary processes and/or accumulation along strike, but instead reflects elongation of depocentres of originally variable cross‐sectional geometry, possibly with the assistance of along‐strike currents. The observed lateral geometric heterogeneity of Neogene sequences can exert profound and unwanted influences on the outcome of scientific drilling intended to calibrate seismic stratigraphic interpretations in the absence of sufficient three‐dimensional (3D) seismic control.

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Integrated Continental Margin Research to benefit ocean and Earth sciences

Cited by 24 publications

References 5 publications

In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

In situ acoustic and laboratory ultrasonic sound speed and attenuation measured in heterogeneous soft seabed sediments: Eel River shelf, California

Pre‐Quaternary sea‐level changes: records and processes

Assessing the significance of along‐strike variations of middle to late Miocene prograding clinoformal sequence geometries beneath the New Jersey continental shelf

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