Upper-Flow-Regime Mud Floodplains, Lower-Flow-Regime Sand Channels: Sediment Transport and Deposition in a Drylands Mud-Aggregate River

摘要: Abstract Dryland rivers in which fine sediments travel as aggregates are increasingly recognized modern and ancient fluvial systems. Fowlers Creek, Australia, is an ephemeral dryland mud-aggregate river whose provide insights into the dynamics of floodplains, origin massive mudrocks from arid depositional environments, nature planar bedding. Creek's flow conditions were inferred relationships between landforms sediment texture, bedforms, sedimentary structures remaming after ceases. Floodplain muds, consisting sand sand-size mud aggregates, distributed over floodplain suspension. As decelerates they deposited bedload. The shallow depth, high load, low aggregate particle density promote ranging lower regime to upper regime, producing coexisting ripples, scours, flat beds, clay layers. With time, visible signs structure lost, leaving a cohesive mud; consolidation not achieved by burial. Aggregates reappear when muds reenter transport. In unchanneled reaches, sheetflows deposit with pervasive horizontal fabric. Channel (coarse sands gravels) minor component deposits. Widespread lower-flow-regime produce beds 2-D dunes, usually without internal stratification or laminae. Lower-flow-regime bedding also observed silty sands. Near close flow, rapid shallowing may move channel higher positions bedform stability spectrum, leading unusual associations. rock record like Creek would be characterized structureless gravelly (channel facies), red mudstones (floodplain fabric but poorly expressed (sheetflow facies).