Inter‐ and supratidal sedimentology of a fjord‐head estuary, south‐western British Columbia

Abstract

Detailed examination of inter‐ and supratidal delta and floodplain sediments exposed in eroding bank sections at 52 locations along the Squamish River estuary provides the basis for recognizing seven distinct facies within the 5500 m‐long estuary. Estuary sedimentation is initially driven by the development of sand bar complexes along the seaward edge of the intertidal delta. Sedimentation continues within interdistributary bay environments as intertidal sandflats and then tidal marshes develop, Aggradation of the delta within interdistributary bay environments results in a gradual transition from delta to alluvial plain. Of the seven facies identified, only the intertidal sands and tidal marsh deposits provide evidence of their tidal origin. Examination of deposits throughout the riverine estuary reveals a number of gradual yet distinct changes of sediment size, structure, and sequence architecture. These trends record the changing nature of tidal and riverine control on sedimentation along the tidal gradient. Generally, with increasing distance up‐estuary, sediment grain‐size increases, the thickness of fine‐grained overbank deposits decreases, and bedding changes from fine parallel bedding to higher energy bedforms. In addition, fining‐upward successions become capped by coarser sands, facies contacts change from gradational to abrupt and occasionally erosional, and facies successions become increasingly complex and less predictable. Squamish River estuary has been divided into four zones based on sedimentological and stratigraphical evidence, each zone reflecting changes in the relative influence of tidal and riverine control on sedimentation. Each zone contains distinctly different facies sequences, although zone boundaries generally are gradational.

Annual textural banding in Holocene estuarine silts, Severn Estuary Levels (SW Britain): patterns, cause and implications

“…Many fine-grained sediments of tidal origin carry more or less complex vertical patterns of laminae which, in terms of thickness and number, can often be interpreted by reference to individual tides and spring-neap (semilunar), anomalistic and even higher-order tidal periodicities. Most recorded examples of this distinctive facies (tidal rhythmite) come from either the postmediaeval part of the Holocene (van Straaten, 1954;Bouma, 1963;Larsonneur, 1975; van den Berg, 1981;Dalrymple and Makino, 1989;Allen, 1990a;Dalrymple et al, 1991;Shi, 1991;Tessier, 1993;Borrego et al, 1995;Gibson and Hickin, 1997;Atwater et al, 2001;Fan and Li, 2002;Stupples, 2002) or from the Proterozoic and mid-Phanerozoic rock records (Broadhurst, 1988;Kvale et al, 1989;Tessier and Author for correspondence (e-mail: j.r.1.a11engreading.ac.uk) (C Arnold 2004 Gigot, 1989;Williams, 1989;2000;Kvale and Archer, 1991;Lanier et al, 1993;Brettle et al, 2002). So far, little is reported from the premodern Holocene or late Pleistocene (Roep, 1991;Choi and Park, 2000;Choi et al, 2001;Allen and Haslett, 2002; Park and Choi, 2002), and the facies remains largely unexploited in studies of Holocene environmental change, despite the prevalence of shallow-marine and estuarine deposits of this epoch.…”

Tidal Rhythmites as Possible Indicators of Very Rapid Subsidence in a Foreland Basin: An Example from the Miocene Marine Molasse Formation of the Digne Foreland Basin, SE France

“…These cycles of couplet thickening and thinning are interpreted as the record of the semilunar (SL) tidal cycle, the duration of which is 14 days. Such SL cycles generally compose the main elements of tidal rhythmites as they are usually recognized in modern (Dalrymple and Makino 1989;Gibson and Hickin 1997) and ancient (Williams 1989;Kvale et al 1989;Brown et al 1990;Archer et al 1991;Lanier et al 1993;Martino and Sanderson 1993;Chan et al 1994;Miller and Eriksson 1997;Adkins and Eriksson 1998;Ehlers and Chan 1999) deposits. Fast Fourrier transform (FFT) analysis performed on SD couplet thickness data reveals two main periods relative to these cycles at T ϭ 20.7 SD couplet duration and T ϭ 22.5 SD couplet duration ( Fig.…”

“…Because rhythmite sedimentological characteristics and cyclic patterns are potentially indicative of tidal dynamic evolution and water-depth changes, tidal rhythmite successions have been used as a tool for paleoenviron-mental reconstructions (Tessier 1993;Lanier et al 1993;Greb and Archer 1995;Gibson and Hickin 1997;Choi et al 2001).…”

Carbon Dynamics Along a Temperate Fjord‐Head Delta: Linkages With Carbon Burial in Fjords

“…Fjord‐head deltas, like many other deltas, have long been proposed as traps for coarse particles due to reduced flow energy (Gibson & Hickin, ; Orton & Reading, ). The coarse‐grained particles found at all deltaic stations in this study, in contrast with the fine‐ grained particles in fjord sediments (Ramirez et al, ), indicated that the Gaer Arm fjord‐head delta is comparable to other fjord‐head deltas in trapping the majority of coarse particles in a fjord system.…”