Plan-view meandering-river depositional model: sinuous channel with point bars on the inside of bends, cut banks on the outside, an abandoned oxbow lake from a cut-off meander loop, flanking natural levees, and the wider floodplain.
A meandering river is a single, sinuous, low-gradient channel that migrates laterally across its floodplain through time by simultaneously eroding the outer (concave) bank of each bend and depositing on the inner (convex) bank, so the whole channel belt sweeps sideways while advancing only slowly downstream. The key features of the resulting depositional system are:
Cut bank — the outer bank of a bend, where the fastest, most erosive flow (the thalweg) impinges directly on the bank, undercutting it and driving continuous lateral channel migration.
Point bar — the inner (convex) bank of the same bend, where flow velocity and competence are lowest; sediment deposited here builds a crescentic bar as the channel migrates, producing the system's principal sand body via lateral accretion (gently inclined epsilon cross-stratification), fining upward from a basal channel-lag gravel/coarse sand through cross-bedded lower point-bar sand to ripple-laminated, finer upper point-bar sand and silt.
Oxbow lake — formed when a meander loop's neck is finally cut off (neck cutoff) as two bends migrate into each other, isolating the abandoned loop as a curved, quiet-water lake that subsequently fills with fine organic-rich mud (clay plug).
Natural levees — low ridges flanking the channel, built by rapid deposition of the coarsest suspended load the instant floodwater spills over the bank and decelerates.
Floodplain — the broad, low-relief area beyond the levees that receives only fine suspended sediment (overbank silt/mud) during periodic flood events, often preserving paleosols (Question 2) during quieter intervals between floods.
Together, repeated lateral migration and periodic avulsion/cutoff produce the classic meandering-river stratigraphic architecture: a basal erosional scour overlain by a fining-upward point-bar sand body, capped by finer levee and floodplain overbank mud, with isolated, mud-filled oxbow-lake bodies encased within the floodplain fines.
