Unidirectional to bidirectional subtidal sandwaves influenced by gradually decreasing steady flow velocity
By: Nakayama, Katsuhiro
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Material type: 
ArticleDescription: 557-561pp ; Illustration.Subject(s): Bedding plane irregularities | Coastal environment | Depositional environment | Sand waves - Honshu - Japan | Sequences stratigraphy | Petrology
In:
Geological magazine : Vol. 134 Iss. 1-6 Year. 1997Summary: Miocene subtidal sandwave deposits in southwest Japan were influenced by periodic flow and steady flow. The sandwave deposits can be divided into five units, based on lithofacies and thickness. In order of accretion, unit 1 consists of unidirectional sand bedforms without mud drapes, unit 2 of unidirectional sand bedforms with thin, discontinuous mud drapes, unit 3 of bidirectional sand bedforms with thin continuous mud drapes, and units 4 and 5 of relatively thinner and smaller bidirectional sand bedforms with continuous mud drapes. The thickness of units 1 to 3 increase progressively to 2.6 m, and units 4 to 5 subsequently decrease from 2.0 to 1.0 m. Variations between the units are due to differing combinations of periodic and steady flow velocities. Palaeoflow velocity is estimated from grain size and unit thickness. Depth-mean velocities of steady flow components gradually decrease from 0.72 ms−1 to 0.16 ms−1 with unit accumulation.
| Item type | Current location | Collection | Call number | Status | Date due | Barcode |
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Article
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Library and Information Centre Periodical Section | Bound Journal Collection | Not for loan | 002523_127 | ||
Serials/Scientific Journal
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Library and Information Centre Periodical Section | Bound Journal Collection | 550 GEO (Browse shelf) | Available | 002523 |
Miocene subtidal sandwave deposits in southwest Japan were influenced by periodic flow and steady flow. The sandwave deposits can be divided into five units, based on lithofacies and thickness. In order of accretion, unit 1 consists of unidirectional sand bedforms without mud drapes, unit 2 of unidirectional sand bedforms with thin, discontinuous mud drapes, unit 3 of bidirectional sand bedforms with thin continuous mud drapes, and units 4 and 5 of relatively thinner and smaller bidirectional sand bedforms with continuous mud drapes. The thickness of units 1 to 3 increase progressively to 2.6 m, and units 4 to 5 subsequently decrease from 2.0 to 1.0 m. Variations between the units are due to differing combinations of periodic and steady flow velocities. Palaeoflow velocity is estimated from grain size and unit thickness. Depth-mean velocities of steady flow components gradually decrease from 0.72 ms−1 to 0.16 ms−1 with unit accumulation.
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