Contrast the patterns of occurrence of sediments and sedimentary structures in the following three kinds of depositional cycles: the kind produced by meandering rivers, the kind produced by deltas, and the kind produced by turbidity currents.

Depositional cycles are the result of changes in sediment supply, rates of subsidence, and sea level fluctuations. Each depositional environment forms its characteristic pattern of sediments and sedimentary structures. In this exercise, we will discuss the characteristics of meandering rivers, deltas, and turbidity currents and compare the patterns of sediments and sedimentary structures in these depositional cycles.

Meandering rivers are characterized by their sinusoidal paths and consist of alternating pool and riffle sections. Sedimentary structures typically associated with meandering rivers include point bars, levees, oxbow lakes, and floodplain deposits. The pattern of occurrence of sediments in meandering rivers is generally fining upward, with coarser sediments deposited in channels and finer sediments deposited on floodplains.

Deltas form at the mouths of rivers where they meet a standing body of water, such as a lake or an ocean. The sedimentary structures commonly associated with deltas include foreset beds, bottomset beds, and topset beds. The deltaic depositional environment shows a coarsening upward sequence, with finer sediments deposited off the delta front (bottomset beds) and coarser sediments deposited on the delta plain (topset beds).

Turbidity currents are underwater avalanches of sediments that flow down continental slopes due to the pull of gravity, typically following submarine canyons. Sedimentary structures commonly found in turbidite sequences include graded bedding, flute casts, convolute bedding, and flame structures. The pattern of occurrence of sediments in turbidite systems is characterized by Bouma sequences that show fining upward sequences with a sharp base and gradual top.

: In conclusion, meandering rivers, deltas, and turbidity currents show different patterns of occurrence of sediments and sedimentary structures: 1. Meandering rivers generally show a fining upward sequence, with point bars, levees, oxbow lakes, and floodplain deposits as common sedimentary structures. 2. Deltas exhibit a coarsening upward sequence, with foreset beds, bottomset beds, and topset beds as characteristic sedimentary structures. 3. Turbidity currents display Bouma sequences with fining upward patterns, including graded bedding, flute casts, convolute bedding, and flame structures as typical sedimentary structures. By understanding the patterns of occurrence of sediments and sedimentary structures in these three depositional environments, we can better interpret the sedimentary record and infer the depositional history of a given geological setting.