Abstract
ABSTRACT We investigate the relationship between the cross-sectional geomorphic expression of a submarine channel as observed on the seafloor and the stratigraphic product of long-lived erosion, bypass, and sediment deposition. Specifically, by reconstructing the time–space evolution of an individual channel fill (i.e., channel element) exposed in outcrop, we establish a genetic link between thick-bedded channel-element-axis sandstone to thinly interbedded channel-element-margin deposits. Although the bounding surface between axis sandstone and margin thin beds is sharply defined, it is composed of a series of geomorphic surface segments of various ages; as such, the composite stratigraphic surface (∼ 17 m relief) was formed from numerous incision events that repeatedly sculpted the conduit. By demonstrating the origin of the stratigraphic surface, we conclude that geomorphic surfaces with 2–7 m of erosional relief were largely responsible for the observed intra-channel-element architecture (and ultimately, the composite 17-m-thick element). The widely documented channel element axis-to-margin architecture is a product of submarine-channel thalweg dynamics, primarily recording interactions between the seafloor and the basal high-concentration layers of channelized turbidity currents.
Highlights
Submarine channel systems are important conveyors of sediment, nutrients, and pollutants from continents to deep-sea basins (Piper and Normark 2001; Liu et al 2013; Kane and Clare 2019)
The analysis of submarine channel-fill units has been widely couched in the context of stratigraphic hierarchy (Pickering et al 1995; Sprague et al 2002; Mayall et al 2006; McHargue et al 2011; Cullis et al 2018). These classification schemes have proven useful for delineation and comparison of deep-water hydrocarbon reservoirs (McHargue et al 2011), and we aim to explore aspects of their morphodynamic origins
Our finescale analysis demonstrates that this stratigraphic surface is composed of a series of geomorphic surface segments of various ages; as such, this composite surface formed over numerous incision events that repeatedly sculpted the setting
Summary
Submarine channel systems are important conveyors of sediment, nutrients, and pollutants from continents to deep-sea basins (Piper and Normark 2001; Liu et al 2013; Kane and Clare 2019). They are carved by gravity-driven density currents, and their sedimentary fills contain a record of protracted sediment transfer across slopes (Deptuck et al 2003; Hubbard et al 2014; Englert et al 2020). Outcrop studies have shown that channel-filling strata can exhibit a variety of facies and architectures, from amalgamated sandstone beds interpreted to have been deposited from high-density turbidity currents (cf. Lowe 1982)
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