A synthesis of depositional trends in intertidal and upper subtidal sediments across the tidal–fluvial transition in the Fraser River, Canada

La Croix, Andrew D. and Dashtgard, Shahin E. (2015) A synthesis of depositional trends in intertidal and upper subtidal sediments across the tidal–fluvial transition in the Fraser River, Canada. Journal of Sedimentary Research, 85 6: 683-698. doi:10.2110/jsr.2015.47


Author La Croix, Andrew D.
Dashtgard, Shahin E.
Title A synthesis of depositional trends in intertidal and upper subtidal sediments across the tidal–fluvial transition in the Fraser River, Canada
Journal name Journal of Sedimentary Research   Check publisher's open access policy
ISSN 1527-1404
1938-3681
Publication date 2015-06-01
Sub-type Article (original research)
DOI 10.2110/jsr.2015.47
Open Access Status Not yet assessed
Volume 85
Issue 6
Start page 683
End page 698
Total pages 16
Place of publication Tulsa, OK, United States
Publisher Society for Sedimentary Geology
Language eng
Abstract Sedimentological, neoichnological, palynological, and geochemical trends from upper subtidal and intertidal positions on channel bars in the lower Fraser River, Canada are synthesized into a single, coherent framework. From these data we define criteria for determining depositional position in shallow water depths in tide-influenced rivers. Three sedimentological trends are observed from the river mouth, through the locus of mud deposition (within the turbidity maximum zone (TMZ)), and into the freshwater-tidal zone. (1) The recurrence (per meter) and thickness of mud beds increase towards the TMZ and tapers in both the landward and seaward directions. (2) Muddy current ripples and graded current ripples are most abundant in the TMZ; they are less common with decreasing brackish-water influence and are absent in the freshwater river reach. (3) Heterolithic bedding (i.e., flaser, wavy, and lenticular) is common in the TMZ, less common seaward, and absent from the freshwater realm. In addition to the sedimentological trends, four ichnological trends parallel decreasing water salinity. With decreasing salinity, there is: (1) a decrease in bioturbation intensity from BI 2-3 to BI 0-1; (2) a decrease in the abundance of bioturbated beds; (3) a marked decrease in the diversity of traces from 5-6 forms to 1-2 forms; and, (4) a decrease in the diameter and length of traces. Traces are rare to absent in the tidal freshwater zone. Palynological and geochemical trends generally follow ichnological trends but are less obvious. Neither dinocyst abundance nor geochemical signature can be used to determine relative position in a tide-influenced river channel, although dinocyst abundances greater than 1% indicate significant marine influence, and 0-1% marine dinocysts indicate tidal influence. Although it is not feasible to determine exact depositional position within the tidal-fluvial transition, our results suggest that it is possible to determine where sediments were deposited relative to the TMZ. In turn, predicting relative depositional position can assist in unraveling stratigraphy and in recognizing nested channels in architecturally complex sedimentary successions.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Earth and Environmental Sciences, Dorothy Hill Collection
 
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 5 times in Thomson Reuters Web of Science Article | Citations
Google Scholar Search Google Scholar
Created: Wed, 15 Mar 2017, 12:47:54 EST by Andrew La Croix on behalf of UQ Energy Initiative