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

Abstract

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 muddominated 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.

Reading tidal processes where their signature is cryptic: The Maastrichtian meandering channel deposits of the Tremp Formation (Southern Pyrenees, Spain)

“…Differently, upward grading from mud to sand similar to that observed at site A (Fig. 9C and G) has been documented in tidal point bars (Pearson & Gingras, 2006) and is consistent with fluid mud (Faas, 1991) accumulation at the base of the channel (Dalrymple et al ., 2003; Dalrymple & Choi, 2007). The FU‐CU trends could be generated either by variable intensity of tidal currents at different sites (Ghinassi et al ., 2018b), or by occasional and localized injection of coarser sediment from the basin margin.…”

Reading tidal processes where their signature is cryptic: The Maastrichtian meandering channel deposits of the Tremp Formation (Southern Pyrenees, Spain)

“…Differently, upward grading from mud to sand similar to that observed at site A (Fig. 9C and G) has been documented in tidal point bars (Pearson & Gingras, 2006) and is consistent with fluid mud (Faas, 1991) accumulation at the base of the channel (Dalrymple et al ., 2003; Dalrymple & Choi, 2007). The FU‐CU trends could be generated either by variable intensity of tidal currents at different sites (Ghinassi et al ., 2018b), or by occasional and localized injection of coarser sediment from the basin margin.…”

Morphodynamic evolution and stratal architecture of translating tidal point bars: Inferences from the northern Venice Lagoon (Italy)

“…15) that has been observed also by previous studies (cf. Choi et al, 2004;Pearson & Gingras, 2006). Consistently, downdip fining of grain size fits with the presence of weaker flows in the thalweg and along the outer bank zone (Section 1 in Fig.…”

Ichnological constraints on the depositional environment of the Sawahlunto Formation, Kandi, northwest Ombilin Basin, west Sumatra, Indonesia

“…The Sawahlunto Formation outcrop section that is the focus of this study also consists of heterolithic very fine-to fine-grained sandstone characterized by low-relief, mud-draped ripples and abundant carbonaceous detritus, consistent with deposition in an intertidal flat succession. Similar deposits, characterized by comparable infaunal and epifaunal assemblages, occur in Modern intertidal sand flat successions in many parts of the world including the Baram River Delta in Borneo (Lambiase et al, 2003); the Willapa Bay estuarine succession in the western United States (Gingras et al, 1999), the Shepody River estuarine succession, New Brunswick, Canada (Pearson and Gingras, 2006) and the wave-protected lower foreshore in Craig Bay, Vancouver Island, Canada (JPZ, personal observations). Although the Sawahlunto Formation clearly indicates deposition within a marginal marine intertidal flat succession, additional data are needed before it can be established what setting these intertidal flats occurred within (i.e.…”

Reading tidal processes where their signature is cryptic: The Maastrichtian meandering channel deposits of the Tremp Formation (Southern Pyrenees, Spain)

“…Differently, upward grading from mud to sand similar to that observed at site A (Fig. 9C and G) has been documented in tidal point bars (Pearson & Gingras, 2006) and is consistent with fluid mud (Faas, 1991) accumulation at the base of the channel (Dalrymple et al ., 2003; Dalrymple & Choi, 2007). The FU‐CU trends could be generated either by variable intensity of tidal currents at different sites (Ghinassi et al ., 2018b), or by occasional and localized injection of coarser sediment from the basin margin.…”

Morphodynamic evolution and stratal architecture of translating tidal point bars: Inferences from the northern Venice Lagoon (Italy)

“…15) that has been observed also by previous studies (cf. Choi et al, 2004;Pearson & Gingras, 2006). Consistently, downdip fining of grain size fits with the presence of weaker flows in the thalweg and along the outer bank zone (Section 1 in Fig.…”

Ichnological constraints on the depositional environment of the Sawahlunto Formation, Kandi, northwest Ombilin Basin, west Sumatra, Indonesia

“…The Sawahlunto Formation outcrop section that is the focus of this study also consists of heterolithic very fine-to fine-grained sandstone characterized by low-relief, mud-draped ripples and abundant carbonaceous detritus, consistent with deposition in an intertidal flat succession. Similar deposits, characterized by comparable infaunal and epifaunal assemblages, occur in Modern intertidal sand flat successions in many parts of the world including the Baram River Delta in Borneo (Lambiase et al, 2003); the Willapa Bay estuarine succession in the western United States (Gingras et al, 1999), the Shepody River estuarine succession, New Brunswick, Canada (Pearson and Gingras, 2006) and the wave-protected lower foreshore in Craig Bay, Vancouver Island, Canada (JPZ, personal observations). Although the Sawahlunto Formation clearly indicates deposition within a marginal marine intertidal flat succession, additional data are needed before it can be established what setting these intertidal flats occurred within (i.e.…”

Reading tidal processes where their signature is cryptic: The Maastrichtian meandering channel deposits of the Tremp Formation (Southern Pyrenees, Spain)

“…Differently, upward grading from mud to sand similar to that observed at site A (Fig. 9C and G) has been documented in tidal point bars (Pearson & Gingras, 2006) and is consistent with fluid mud (Faas, 1991) accumulation at the base of the channel (Dalrymple et al ., 2003; Dalrymple & Choi, 2007). The FU‐CU trends could be generated either by variable intensity of tidal currents at different sites (Ghinassi et al ., 2018b), or by occasional and localized injection of coarser sediment from the basin margin.…”

Morphodynamic evolution and stratal architecture of translating tidal point bars: Inferences from the northern Venice Lagoon (Italy)

“…15) that has been observed also by previous studies (cf. Choi et al, 2004;Pearson & Gingras, 2006). Consistently, downdip fining of grain size fits with the presence of weaker flows in the thalweg and along the outer bank zone (Section 1 in Fig.…”

Ichnological constraints on the depositional environment of the Sawahlunto Formation, Kandi, northwest Ombilin Basin, west Sumatra, Indonesia

“…The Sawahlunto Formation outcrop section that is the focus of this study also consists of heterolithic very fine-to fine-grained sandstone characterized by low-relief, mud-draped ripples and abundant carbonaceous detritus, consistent with deposition in an intertidal flat succession. Similar deposits, characterized by comparable infaunal and epifaunal assemblages, occur in Modern intertidal sand flat successions in many parts of the world including the Baram River Delta in Borneo (Lambiase et al, 2003); the Willapa Bay estuarine succession in the western United States (Gingras et al, 1999), the Shepody River estuarine succession, New Brunswick, Canada (Pearson and Gingras, 2006) and the wave-protected lower foreshore in Craig Bay, Vancouver Island, Canada (JPZ, personal observations). Although the Sawahlunto Formation clearly indicates deposition within a marginal marine intertidal flat succession, additional data are needed before it can be established what setting these intertidal flats occurred within (i.e.…”