Deep-Sea Gravel from Cascadia Channel

Griggs, Gary B.; Kulm, L. D.; Waters, Aaron C.; Fowler, Gerald A.

doi:10.1086/627560

Cited by 29 publications

(13 citation statements)

References 9 publications

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“…This is not true. The existence of deep water gravel and pebbly sandstone deposits related to hyperpycnal discharges of the Columbia river has been clearly documented in the Cascadia Channel (Zuffa et al 2000) in cores located 200 km far from the coast and at a water depth of 3820 m (Griggs et al 1970;Normark and Reid 2003). Individual pebbles are rounded to subrounded with diameters up to 4 cm.…”

Section: Intrabasinal and Extrabasinal Turbiditesmentioning

confidence: 99%

The new knowledge is written on sedimentary rocks – a comment on Shanmugam’s paper “the hyperpycnite problem”

Zavala

2019

J. Palaeogeogr.

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In a recent contribution G. Shanmugam (2018) discusses and neglects the importance of hyperpycnal flows and hyperpycnites for the understanding of some sediment gravity flow deposits. For him, the hyperpycnal flow paradigm is strictly based on experimental and theoretical concepts, without the supporting empirical data from modern depositional systems. In this discussion I will demonstrate that G. Shanmugam overlooks growing evidences that support the importance of hyperpycnal flows in the accumulation of a huge volume of fossil clastic sediments. Sustained hyperpycnal flows also provide a rational explanation for the origin of well sorted fine-grained massive sandstones with floating clasts, a deposit often wrongly related to sandy debris flows.

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Section: Intrabasinal and Extrabasinal Turbiditesmentioning

confidence: 99%

The new knowledge is written on sedimentary rocks – a comment on Shanmugam’s paper “the hyperpycnite problem”

Zavala

2019

J. Palaeogeogr.

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“…Hurley (1960Hurley ( , 1964 described the Cascadia Channel, which extends offshore from the Columbia River south into and through the Blanco Fracture Zone; the channel exits from the fracture zone onto the Pacific plate and extends west for several hundred kilometers on the Tufts Abyssal Plain. Griggs et al (1970) described pebble-sized sediment from the floor of Cascadia Channel west of the Blanco Fracture Zone that they ascribed to an eastern Washington source area; they further suggested that this coarse material was carried to the ocean by the late Pleistocene catastrophic floods from glacial Lake Missoula and subsequently transported through Cascadia Channel to the Pacific plate.…”

Section: Introductionmentioning

confidence: 99%

Turbidite Megabeds in an Oceanic Rift Valley Recording Jökulhlaups of Late Pleistocene Glacial Lakes of the Western United States

Zuffa¹,

Normark²,

Serra³

et al. 2000

The Journal of Geology

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Escanaba Trough is the southernmost segment of the Gorda Ridge and is filled by sandy turbidites locally exceeding 500 m in thickness. New results from Ocean Drilling Program (ODP) Sites 1037 and 1038 that include accelerator mass spectrometry (AMS) 14C dates and revised petrographic evaluation of the sediment provenance, combined with high-resolution seismic-reflection profiles, provide a lithostratigraphic framework for the turbidite deposits. Three fining-upward units of sandy turbidites from the upper 365 m at ODP Site 1037 can be correlated with sediment recovered at ODP Site 1038 and Deep Sea Drilling Program (DSDP) Site 35. Six AMS 14C ages in the upper 317 m of the sequence at Site 1037 indicate that average deposition rates exceeded 10 m/k.yr. between 32 and 11 ka, with nearly instantaneous deposition of one approximately 60-m interval of sand. Petrography of the sand beds is consistent with a Columbia River source for the entire sedimentary sequence in Escanaba Trough. High-resolution acoustic stratigraphy shows that the turbidites in the upper 60 m at Site 1037 provide a characteristic sequence of key reflectors that occurs across the floor of the entire Escanaba Trough. Recent mapping of turbidite systems in the northeast Pacific Ocean suggests that the turbidity currents reached the Escanaba Trough along an 1100-km-long pathway from the Columbia River to the west flank of the Gorda Ridge. The age of the upper fining-upward unit of sandy turbidites appears to correspond to the latest Wisconsinan outburst of glacial Lake Missoula. Many of the outbursts, or jökulhlaups, from the glacial lakes probably continued flowing as hyperpycnally generated turbidity currents on entering the sea at the mouth of the Columbia River.

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“…The floodwater had immense power (Benito, 1997) and was charged with coarse sediment in suspension. 1) (Griggs et al, 1970). Long-distance transport of Missoula Flood sediments across the abyssal Pacific Ocean floor is indicated by the lithology of pebbles recovered from the Blanco Fracture Zone ( Fig.…”

Section: North Americamentioning

confidence: 99%

High‐Energy Megafloods: Planetary Settings and Sedimentary Dynamics

Baker

2002

Flood and Megaflood Processes and Deposits

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High-energy megafloods usually occur in relatively narrow and deep, confined reaches supplied by large volumes of water. Examples of planetary settings include modern and ancient glacial outburst floods (jökulhlaups) of Iceland, glacial lake spillways south of the Pleistocene Laurentide Ice Sheet, the Channeled Scabland of the north-western USA, mountain lake bursts from central Asia, spillways connecting Pleistocene lake basins in Asia, and the immense outflow channels of Mars. The palaeohydraulic analyses of all these floods indicate that they generate values of stream power per unit area (> 10 3 W m −2 ) and bed shear stress (> 10 3 N m −2 ) that are two orders of magnitude larger than are typical for floods on large alluvial rivers such as the Amazon and Mississippi. Flood discharges can be comparable to flows in ocean currents, indicating important short-term roles in planetary water and sediment fluxes.Significant sedimentary processes in the confined reaches for megafloods include streamlining (and related bar formation), scour around obstacles and giant current ripple (dune) formation. Sediment transport involves the entrainment of large boulders and phenomenally high loading of the flow with extremely coarse suspended and wash load. The outflux of high-energy, sediment-charged megafloods from confined continental settings to ocean basins results in hyperpycnal flows, and unusually powerful turbidity currents. These have been documented recently for the Pleistocene Missoula floods that formed the Channeled Scabland. They also were probably very important for the Martian outflow channel floods, which may have exerted the primary trigger for climatic change during Mars' geological history.

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Deep-Sea Gravel from Cascadia Channel

Cited by 29 publications

References 9 publications

The new knowledge is written on sedimentary rocks – a comment on Shanmugam’s paper “the hyperpycnite problem”

The new knowledge is written on sedimentary rocks – a comment on Shanmugam’s paper “the hyperpycnite problem”

Turbidite Megabeds in an Oceanic Rift Valley Recording Jökulhlaups of Late Pleistocene Glacial Lakes of the Western United States

High‐Energy Megafloods: Planetary Settings and Sedimentary Dynamics

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