Is there evidence for geostrophic currents preserved in the sedimentary record of inner to middle shelf deposits?; discussion and reply

Higgs, Roger; Hart, B. S.; Vantfoort, R. M.; Plint, A. G.; Leckie, D. A.; Krystinik, Lee F.

doi:10.1306/212f922d-2b24-11d7-8648000102c1865d

Cited by 17 publications

(14 citation statements)

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“…The abundance of wave-formed features in the interpreted hyperpycnites of the lower Genesee, such as hummocky cross-lamination, concave-up lamina-set geometries, and combined-flow-ripple cross-lamination (Figs. 5, 6, 7) is consistent with storm-aided transport of hyperpycnal plumes (Friedrichs and Wright 2004;Higgs 1990), a common process on low-gradient deltas with slopes , 0.3u (Bhattacharya and MacEachern 2009).…”

Section: Discussionsupporting

confidence: 61%

Muddy Prodeltaic Hyperpycnites In the Lower Genesee Group of Central New York, USA: Implications For Mud Transport In Epicontinental Seas

Wilson

Schieber

2014

Journal of Sedimentary Research

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Recent studies of marine continental shelves show that hyperpycnal flows are responsible for offshore transport of large volumes of sediment. Detailed facies analysis and petrography of the lower Genesee Group in the Northern Appalachian Basin (NAB) shows a wealth of sedimentary textures and fabrics that indicate mud deposition by lateral transport across and along the shelf under energetic conditions. Intervals of silt-rich mudstones and muddy siltstones with internal scours, diffuse stratification, soft-sediment deformation, normal and inverse lamina-set grading, and a reduced intensity and diversity of bioturbation occur in multiple facies types and ''interrupt'' what appears to be the overall background sedimentation. These intervals and their sedimentary features are interpreted as products of high-density fluvial discharge events, which generated turbulent flows that carried fine-grained clastics several tens of kilometers offshore from the paleoshoreline.Recognizing these sediments as products of river-flood-and storm-wave-generated offshore-directed underflows challenges previous depositional models for organic-rich mudstones in the lower Genesee succession, which call for clastic starvation and suspension settling of clay and silt in a deep stratified basin. Rapid deposition of fine-grained intervals from hyperpycnal plumes in a setting favoring preservation of organic-rich mudstones calls for a reappraisal of the depositional setting of not only the Genesee Group, but also of comparable mudstone successions in the Appalachian Basin and elsewhere.

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Section: Discussionsupporting

confidence: 61%

Muddy Prodeltaic Hyperpycnites In the Lower Genesee Group of Central New York, USA: Implications For Mud Transport In Epicontinental Seas

Wilson

Schieber

2014

Journal of Sedimentary Research

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“…The latter is a common interpretation (e.g. Bartolini et al, 1975;Hamblin & Walker, 1979;Leckie & Walker, 1982;Higgs, 1990;Myrow & Southard, 1996;Wiberg, 2000;Myrow et al, 2002Myrow et al, , 2008Lamb et al, 2008) and arguably best explains the presence of offshore directed sole markings (e.g. Hamblin & Walker, 1979;Leckie & Walker, 1982;Leckie & Krystinik, 1989;Lamb et al, 2008;Myrow et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Bartolini et al. , 1975; Hamblin & Walker, 1979; Leckie & Walker, 1982; Higgs, 1990; Myrow & Southard, 1996; Wiberg, 2000; Myrow et al. , 2002, 2008; Lamb et al.…”

Section: Introductionmentioning

confidence: 99%

Is most hummocky cross‐stratification formed by large‐scale ripples?

Quin¹

2011

Sedimentology

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Although normal isotropic hummocky cross‐stratification is commonly interpreted to be the deposit of large‐scale ripples, there are many reasons why this may not usually be the case. These reasons include: (i) that the stratification produced by large‐scale ripples does not particularly look like isotropic hummocky cross‐stratification; (ii) that it is difficult reconciling the abundance of HCS with the restricted hydraulic stability of large‐scale ripples in silt to fine sand (i.e. the grain sizes in which hummocky cross‐stratification is usually found); (iii) that the distribution of hummocky cross‐stratification within ancient storm beds is not the distribution that would be expected from large‐scale ripples; (iv) that the flows calculated to have formed ancient examples of hummocky cross‐stratification would be expected to generate an upper stage plane bed rather than ripples; and (v) that it is difficult to explain why large‐scale ripples would predominate in the proximal parts of storm beds when modern storm flows commonly exceed the threshold for entrainment. In contrast to the various hypotheses which propose that isotropic hummocky cross‐stratification is generated by ripples, an alternative hypothesis which suggests that it is generated by instabilities, does seem to adequately explain the origin of hummocky cross‐stratification. However, it is difficult to accept this hypothesis given that the origin of the proposed instabilities is unproven. These conclusions highlight the continued uncertainty regarding the process, which generates hummocky cross‐stratification.

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“…Myrow and Southard (1996) argued that under certain conditions the turbulence added by storm waves could maintain and/or enhance suspended sediment concentrations and thus increase excess-weight forces. Some tempestites were interpreted as the deposits of shelf turbidity currents, or combined flows with strong excess-weight force components, produced by river floods that moved directly into the ocean as hyperpycnal flows (Bartolini et al 1975;Higgs 1990).…”

Section: Introductionmentioning

confidence: 99%

Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica

Myrow¹,

Fischer²,

Goodge³

2002

Journal of Sedimentary Research

173

118

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Sandstone tempestite beds in the Starshot Formation, central Transantarctic Mountains, were deposited in a range of shoreline to shelf environments. Detailed sedimentological analysis indicates that these beds were largely deposited by wave-modified turbidity currents. These currents are types of combined flows in which storm-generated waves overprint flows driven by excess-weight forces. The interpretation of the tempestites of the Starshot Formation as wave-dominated turbidites rests on multiple criteria. First, the beds are generally well graded and contain Bouma-like sequences. Like many turbidites, the soles display abundant well-developed flutes. They also contain thick divisions of climbing-ripple lamination. The lamination, however, is dominated by convex-up and sigmoidal foresets, which are geometries identical to those produced experimentally in current-dominated combined flows in clear water. Finally, paleocurrent data support a turbidity-current component of flow. Asymmetric folds in abundant convolute bedding reflect liquefaction and gravity-driven movement and hence their orientations indicate the downslope direction at the time of deposition. The vergence direction of these folds parallels paleocurrent readings of flute marks, combined-flow ripples, and a number of other current-generated features in the Starshot event beds, indicating that the flows were driven down slope by gravity. The wave component of flow in these beds is indicated by the presence of small-to largescale hummocky cross-stratification and rare small two-dimensional ripples.Wave-modified turbidity currents differ from deep-sea turbidity currents in that they may not be autosuspending and some proportion of the turbulence that maintains these flows comes from storm waves. Such currents are formed in modern shoreline environments by a combination of storm waves and downwelling sediment-laden currents. They may also be formed as a result of oceanic floods, events in which intense sediment-laden fluvial discharge creates a hyperpycnal flow. Event beds in the Starshot Formation may have formed from such a mechanism. Oceanic floods are formed in rivers of small to medium size in areas of high relief, commonly on active margins. The Starshot Formation and the coeval Douglas Conglomerate are clastic units that formed in response to uplift associated with active tectonism. Sedimentological and stratigraphic data suggest that coarse alluvial fans formed directly adjacent to a marine basin. The geomorphic conditions were therefore likely conducive to rapid fluvial discharge events associated with storms. The abundance of current-dominated combinedflow ripples at the tops of many Starshot beds indicates that excessweight forces were dominant throughout deposition of many of these beds.

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Is there evidence for geostrophic currents preserved in the sedimentary record of inner to middle shelf deposits?; discussion and reply

Cited by 17 publications

References 0 publications

Muddy Prodeltaic Hyperpycnites In the Lower Genesee Group of Central New York, USA: Implications For Mud Transport In Epicontinental Seas

Muddy Prodeltaic Hyperpycnites In the Lower Genesee Group of Central New York, USA: Implications For Mud Transport In Epicontinental Seas

Is most hummocky cross‐stratification formed by large‐scale ripples?

Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica

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