Bioturbation trends across the freshwater to brackish-water transition in rivers

La Croix, Andrew D. , Dashtgard, Shahin E. , Gingras, Murray K. , Hauck, Tyler E. and MacEachern, James A. (2015) Bioturbation trends across the freshwater to brackish-water transition in rivers. Palaeogeography, Palaeoclimatology, Palaeoecology, 440 66-77. doi:10.1016/j.palaeo.2015.08.030


Author La Croix, Andrew D.
Dashtgard, Shahin E.
Gingras, Murray K.
Hauck, Tyler E.
MacEachern, James A.
Title Bioturbation trends across the freshwater to brackish-water transition in rivers
Journal name Palaeogeography, Palaeoclimatology, Palaeoecology   Check publisher's open access policy
ISSN 0031-0182
1872-616X
Publication date 2015-01-01
Sub-type Article (original research)
DOI 10.1016/j.palaeo.2015.08.030
Open Access Status Not yet assessed
Volume 440
Start page 66
End page 77
Total pages 12
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Abstract Most existing ichnological models predict an increase in burrow density and diversity from the zone of persistent brackish-water into the realm of persistent freshwater. Herein we compare the neoichnology of five tidal-fluvial channels with varying tidal magnitudes, saltwater incursion distances, and river discharge. The results indicate that there is a noticeable diminution in the sizes of marine traces and a corresponding decrease in their distribution (reduced abundance of burrowed versus unburrowed beds) with decreasing salinity. From the landward limit of saltwater incursion into the wholly freshwater tidal backwater, there is no concurrent increase in terrestrial or freshwater burrow forms; rather, burrow diversities remain low (range: 10 to 35% of the "open marine" signature) and burrow densities decrease from BI 0-3 to BI 0-1 in both sand and mud units. The five modern systems described in this study do not support the hypothesis that there is an increase in bioturbation from the brackish-water reaches of channels into freshwater reaches. In fact, freshwater channels, including those in the tidal backwater zone, are characterized by very low trace-fossil diversities (1 to 2 forms) as well as low and sporadically distributed bioturbation intensities (BI 0-1).
Keyword Brackish water
Brackish-water ichnological model
Deltas
Estuaries
Freshwater
Neoichnology
Trace fossils
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, 12:50:48 EST by Andrew La Croix on behalf of UQ Energy Initiative