Sharp change of the channel bar pattern within the river delta: Insights from modern Ganjiang River delta in Jiangxi province, China

Abstract

Channel bars (mid-channel bars or point bars) in river-deltas offer building materials, habitats, and farmlands, and threaten water transportation, as well as, could become targets in hydrocarbon reservoirs. Researchers focus on the channel bar pattern in rivers, whereas ignoring the channel bar pattern in distributary channels. We propose a sharp change of the channel bar pattern from the river to the delta. The integration of remote map analysis, fieldwork, and a flume experiment resulted in a quantified sharp change in the channel bar pattern in the Ganjiang River-Delta and revealed a hydrodynamic mechanism. The result shows that distributary channels develop much more insular, finer-grained, smaller-scaled, lower-width-depth-ratio channel bars, compared to the upstream river. Distributary channels develop more point bars and fewer mid-channel bars than the upstream braided river, and develop fewer point bars than the upstream meandering river. Sharply weakening bank erosions in distributary channels lead to the formation of the sharp change in the channel bar pattern from the upstream river, due to backwater-effect-induced sharp gentling of landform gradient. The backwater effect impedes bank erosions in the distributary channels, but promotes bank erosions in upstream rivers, in turn, enhances the sharp change of the channel bar pattern. This work provides insights into channel bars' growth in modern river-deltas and provides new facies models for the river-delta system.

The formation of fan‐deltas in mountain lakes: Findings from Zelené Kežmarské Lake (Slovakia)

“…The internal structure of the mouth bars consists of sets of wavy reflections marking traces of bedforms. The sedimentary structure resembles the mouth bars studied by Lee et al (2007) in the Cretaceous Wall Creek sandstone delta (Wyoming, USA) and Xu et al (2022) in the Ganjiang delta (China). GPR section 18 (Figure 6) is similar to the architecture of a mouth bar delta shown in Winsemann et al (Winsemann et al, 2018; see Figure 9a,c in there).…”

Depositional Facies and Sequence Stratigraphy of Kodiak Butte, Western Delta of Jezero Crater, Mars

“…The difference in dip observed between Fsa and Fsb likely reflects the position of the deposits within the 3D deltaic bar. The steeper angles observed (up to ∼35°) are preferentially observed closer to the primary direction of delta progradation, while lower dips indicate a deposition occurring on the lateral banks of a delta bar, off‐axis from the primary direction of delta progradation (e.g., Ori & Roveri, 1987; van Yperen et al., 2020; Xu et al., 2023; Zhang et al., 2016). This peculiar 3D architecture is evidenced here at Kodiak within Unit 1 (Figure 3c) as we observe lower dip values associated with the occurrence of Fsb in section #4 compared to Fsa in section #2.…”