Of sand and mud: sedimentological criteria for identifying the turbidity maximum zone in a tidally influenced river

La Croix, Andrew D. and Dashtgard, Shahin E. (2014) Of sand and mud: sedimentological criteria for identifying the turbidity maximum zone in a tidally influenced river. Sedimentology, 61 7: 1961-1981. doi:10.1111/sed.12126


Author La Croix, Andrew D.
Dashtgard, Shahin E.
Title Of sand and mud: sedimentological criteria for identifying the turbidity maximum zone in a tidally influenced river
Journal name Sedimentology   Check publisher's open access policy
ISSN 0037-0746
1365-3091
Publication date 2014-07-05
Year available 2014
Sub-type Article (original research)
DOI 10.1111/sed.12126
Open Access Status Not yet assessed
Volume 61
Issue 7
Start page 1961
End page 1981
Total pages 21
Place of publication Chichester, West Sussex, United Kingdom
Publisher Wiley-Blackwell
Language eng
Abstract The thickness and lateral distribution of sand and mud beds and bedsets on channel bars from the tidally influenced Fraser River, British Columbia, Canada, are quantitatively assessed. Fifty-six vibracores totalling ca 114m of vertical section are used to tabulate bed thicknesses. Statistical calculations are undertaken for nine channel bars ranging from the freshwater and tidal zone, to the sustained brackish water and tidal zone. The data reveal that thickness trends can be organized into three groups that broadly correspond to time-averaged hydrodynamic and salinity conditions in the various distributary channels. Thick sand beds (up to 30cm) and thin mud beds (up to 5cm) characterize the freshwater tidal zone. The tidal and freshwater to brackish-water transition zone comprises thin sands (up to 10cm) and thicker muds (up to 19cm), and the sustained brackish water tidal zone consists of thin muds (up to 6cm) with relatively thicker sands (up to 25cm). The results suggest that the locus of mud deposition occurs in the tidal freshwater to brackish-water zone, probably reflecting mud flocculation and deposition at the turbidity maximum. Landward of the turbidity maximum, mud deposition is linked to tidal influence (tidal backwater effect and reverse eddy currents on channel margins) as mud beds thin in the landward direction. These results support the hypothesis that mud deposition is greatest at the turbidity maximum and decreases in both the seaward and landward direction. This study also showcases that mud-bed thicknesses are greatest towards the turbidity maximum and thin in both the landward and seaward direction. In the rock record, the apex of mud deposition probably marks the position of the palaeo-turbidity maximum
Keyword Backwater effect
Bed-thickness distribution
Fraser River
Inclined heterolithic stratification
Intertidal zone
Saltwater incursion
Tidal-fluvial transition
Turbidity maximum
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Office of the Vice-Chancellor
 
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Created: Wed, 15 Mar 2017, 12:53:18 EST by Andrew La Croix on behalf of UQ Energy Initiative