The influence of sediment supply on the stratigraphic evolution of an ancient passive margin deep-marine slope channel system, Windermere Supergroup, British Columbia, Canada

Abstract

At the Castle Creek study area a superbly exposed continental-slope channel-complex set of the Isaac Formation termed ICC1 crops out. ICC1 is 220 m thick and exposed over 5 km parallel to bedding and consists of four vertically stacked channel complexes—lower channel complex (LC), and three upper channel complexes (termed UC1–UC3). Based on differences in lithological and textural makeup, and stratal trends, two styles of channel fill and stacking pattern are recognized—disorganized stack of bottom-up channel fills (LC, UC1, and UC2), and organized lateral-offset stack of laterally accreting channel fills (UC3). Bottom-up channel fills show an upward and axis-to-margin fining and thinning, and were filled by poorly sorted, density-stratified flows. In contrast, channel fills of UC3 exhibit negligible upward and lateral fining and thinning and were filled by flows enriched in coarse and very coarse sand and were only negligibly stratified in their lower part. Accordingly, the lower, depositionally important part of the flow had a plug-like density profile with limited overspill that caused circulation patterns in channel bends to resemble those in rivers. Notably, the grain-size makeup of late-stage channel fills of UC3 indicates a change in the makeup of the sediment supply, namely grain size and sorting. Note that this systematic upward change in sediment texture and channel type is observed in most (5 of 8) Isaac slope channel-complex sets at the Castle Creek study area. These changes reflect a change from hinterland- to shelf-dominated sediment supply interpreted to be associated with a long-term rise of relative sea level that progressively expanded continental-shelf accommodation and retention of coarse relict and palimpsest sediment. During short-term relative sea-level falls this increasingly voluminous source of coarse, moderately well-sorted siliciclastic and minor carbonate sediment eventually came to dominate the supply of coarse sediment to the shelf edge, and in turn, controlled the character of turbidity currents that remobilized sediment farther down the continental slope and possibly onto the basin floor.

Organic matter deposition and preservation in ancient deep‐sea levée sediments: Implications for Neoproterozoic trends in carbon burial

“…Reduced amplitude of eustatic change during greenhouse times can allow fluvial systems, especially those with high sediment flux, to remain connected to the deep sea even during highstand conditions, which would further enhance the delivery of terrestrial OM into the deep sea (Keil et al ., 1997; Burdige, 2005; Sweet & Blum, 2016). During icehouse periods, on the other hand, the increased amplitude of eustatic fluctuations typically results in continental fluvial systems being separated from the deep sea by a wide continental shelf during highstands (Blum & Hatter‐Womack, 2009; Sømme et al ., 2009; Sweet & Blum, 2016; Fraino et al ., 2022). This suggests that during the Proterozoic, when marine OM was the single source of organic carbon, icehouse transgressive to the early/middle part of the falling stage systems tracts would provide optimal conditions for OM production and burial in the deep marine.…”

“…The sedimentology and stratigraphic architecture of the levée deposits associated with two of these channel complexes, namely Isaac Channel Complex 3 (ICC3) and Isaac Channel Complex 4 (ICC4), have been described in detail by previous workers (Navarro et al, 2007;Davis, 2011;Khan, 2012;Cunningham & Arnott, 2021;Bergen et al, 2022). The channel complexes themselves have also been described in detail by Navarro et al (2007), Terlaky (2014), Fraino (2020), Bergen et al (2022) and Fraino et al (2022), and notably, contain little to no organic material [total organic carbon (TOC) ≤0.1%]. Similarly, a number of earlier studies had collected geochemical data in levée deposits of the Isaac Formation, but Milczarek (2018) was the first to conduct a systematic sampling program and construct a chemostratigraphic profile from the uppermost part of the FIC below Isaac Channel Complex 1 (ICC1) up through strata of Isaac Channel Complexes 2 and 3 (ICC2 and ICC3, respectively), using major, minor and trace element composition and geochemical proxies to analyse trends related to sediment provenance, seawater redox and stratification, and sea level.…”

“…The channel complexes themselves have also been described in detail by Navarro et al . (2007), Terlaky (2014), Fraino (2020), Bergen et al . (2022) and Fraino et al .…”

“…(2022) and Fraino et al . (2022), and notably, contain little to no organic material [total organic carbon (TOC) ≤0.1%]. Similarly, a number of earlier studies had collected geochemical data in levée deposits of the Isaac Formation, but Milczarek (2018) was the first to conduct a systematic sampling program and construct a chemostratigraphic profile from the uppermost part of the FIC below Isaac Channel Complex 1 (ICC1) up through strata of Isaac Channel Complexes 2 and 3 (ICC2 and ICC3, respectively), using major, minor and trace element composition and geochemical proxies to analyse trends related to sediment provenance, seawater redox and stratification, and sea level.…”

Stratigraphic evolution of a spectacularly exposed turbidite channel belt from the Tachrift System (late Tortonian, north‐East Morocco)

“…The less amalgamated parts of these channel fills reflect deposition in off-axis settings where sole erosion by subsequent flow was relatively minor. Although comparatively sandier and of larger-scale, analogue outcrop examples are those from the Tres Pasos Formation (Hubbard et al, 2014), the Windemere Supergroup (Fraino et al, 2022) and the Capistrano Formation (Camacho et al, 2002).…”