HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Pearson, N. J. Articles by Gingras, M. K. Search for Related Content GeoRef GeoRef Citation

An Ichnological and Sedimentological Facies Model for Muddy Point-Bar Deposits

¹ Department of Geological Sciences, 114 Science Place, University of Saskatchewan, Saskatoon, Saskatchewan, S7Z 5E2, Canada; nadinepearson{at}gmail.com
² Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Building, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada

Detailed analysis of fine-grained clastic deposits associated with the macrotidal estuarine mouth of the Shepody River, New Brunswick, Canada, concentrated on identifying the ichnological and sedimentological characteristics of tidally dominated point bars and their adjacent tidal flats. The aim of the study was to establish an ichnological facies model for similar deposits.

Within the study area, the distribution of ichnological structures and sedimentary characteristics such as grain-size distribution and total organic content are associated with bar elevation (i.e., upper, middle, or lower intertidal), tidal-bank slope, and the local hydraulic processes. The distribution of animal traces is also influenced by the duration of intertidal exposure and sedimentation rates. Polykladichnus- and Skolithos-like traces characterize upper-subtidal and lower-intertidal zones of the point bars; Arenicolites-, Diplocraterion-, Polykladichnus-, Palaeophycus-, and Planolites-like forms are pervasive in middle-intertidal zones; and, Siphonichnus- and Polykladichnus-like burrows typify the upper-intertidal point bars and the tidal flats. The size and diversity of the burrowing fauna are affected by the chemistry of the depositional waters and by seasonal variations in composition and temperature of those waters. The extreme seasonality of the area favors opportunistic fauna and thereby contributes to an impoverished, brackish-water trace assemblage.

Geomorphologically, the area is dominated by point-bar and tidal-flat deposits, which comprise rhythmic bedding, composed of interlaminated to thinly interbedded silty and sandy mud. Point-bar bedding dips channelwards and represents mud-dominated inclined heterolithic stratification (IHS). The IHS alternates between burrowed and laminated beds. Laminated beds contain rhythmic lamination. Cyclic variations in laminae thickness are attributed to neap–spring variation in tidal-current strength. The burrowed interbeds exhibit high degrees of bioturbation that eradicate the preexisting lamination. The intercalation of laminated and burrowed beds represent seasonal variations in the depositional system: laminated beds characterize early winter and early spring sedimentation, and the bioturbated beds represent late spring through fall deposits.

This article has been cited by other articles:

				L. G. HERRINGSHAW, O. A. SHERWOOD, and D. McILROY ECOSYSTEM ENGINEERING BY BIOTURBATING POLYCHAETES IN EVENT BED MICROCOSMS Palaios, January 1, 2010; 25(1): 46 - 58. [Abstract] [Full Text] [PDF]

				B. Yang, R. W. Dalrymple, M. K. Gingras, S. Chun, and H. Lee Up-Estuary Variation of Sedimentary Facies and Ichnocoenoses in an Open-Mouthed, Macrotidal, Mixed-Energy Estuary, Gomso Bay, Korea Journal of Sedimentary Research, September 1, 2007; 77(9): 757 - 771. [Abstract] [Full Text] [PDF]