Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica
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 co...
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ftcaltechauth:oai:authors.library.caltech.edu:27553 2023-05-15T13:37:28+02:00 Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica Myrow, Paul M. Fischer, Woodward Goodge, John W. 2002-09 application/pdf https://authors.library.caltech.edu/27553/ https://authors.library.caltech.edu/27553/1/MYRjsr02.pdf https://resolver.caltech.edu/CaltechAUTHORS:20111101-110016082 en eng Society for Sedimentary Geology https://authors.library.caltech.edu/27553/1/MYRjsr02.pdf Myrow, Paul M. and Fischer, Woodward and Goodge, John W. (2002) Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica. Journal of Sedimentary Research, 72 (5). pp. 641-656. ISSN 1527-1404. doi:10.1306/022102720641. https://resolver.caltech.edu/CaltechAUTHORS:20111101-110016082 <https://resolver.caltech.edu/CaltechAUTHORS:20111101-110016082> other Article PeerReviewed 2002 ftcaltechauth https://doi.org/10.1306/022102720641 2021-11-11T18:48:06Z 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 large-scale 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 combined-flow ripples at the tops of many Starshot beds indicates that excess-weight forces were dominant throughout deposition of many of these beds. Article in Journal/Newspaper Antarc* Antarctica Antarctica Journal Caltech Authors (California Institute of Technology) Transantarctic Mountains Journal of Sedimentary Research 72 5 641 656 |
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Open Polar |
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Caltech Authors (California Institute of Technology) |
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ftcaltechauth |
language |
English |
description |
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 large-scale 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 combined-flow ripples at the tops of many Starshot beds indicates that excess-weight forces were dominant throughout deposition of many of these beds. |
format |
Article in Journal/Newspaper |
author |
Myrow, Paul M. Fischer, Woodward Goodge, John W. |
spellingShingle |
Myrow, Paul M. Fischer, Woodward Goodge, John W. Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica |
author_facet |
Myrow, Paul M. Fischer, Woodward Goodge, John W. |
author_sort |
Myrow, Paul M. |
title |
Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica |
title_short |
Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica |
title_full |
Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica |
title_fullStr |
Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica |
title_full_unstemmed |
Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica |
title_sort |
wave-modified turbidites: combined-flow shoreline and shelf deposits, cambrian, antarctica |
publisher |
Society for Sedimentary Geology |
publishDate |
2002 |
url |
https://authors.library.caltech.edu/27553/ https://authors.library.caltech.edu/27553/1/MYRjsr02.pdf https://resolver.caltech.edu/CaltechAUTHORS:20111101-110016082 |
geographic |
Transantarctic Mountains |
geographic_facet |
Transantarctic Mountains |
genre |
Antarc* Antarctica Antarctica Journal |
genre_facet |
Antarc* Antarctica Antarctica Journal |
op_relation |
https://authors.library.caltech.edu/27553/1/MYRjsr02.pdf Myrow, Paul M. and Fischer, Woodward and Goodge, John W. (2002) Wave-Modified Turbidites: Combined-Flow Shoreline and Shelf Deposits, Cambrian, Antarctica. Journal of Sedimentary Research, 72 (5). pp. 641-656. ISSN 1527-1404. doi:10.1306/022102720641. https://resolver.caltech.edu/CaltechAUTHORS:20111101-110016082 <https://resolver.caltech.edu/CaltechAUTHORS:20111101-110016082> |
op_rights |
other |
op_doi |
https://doi.org/10.1306/022102720641 |
container_title |
Journal of Sedimentary Research |
container_volume |
72 |
container_issue |
5 |
container_start_page |
641 |
op_container_end_page |
656 |
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1766092161702428672 |