6.15: Sedimentary Processes and Sedimentary Structures

Sedimentary Processes and Sedimentary Structures

Lamination and bedding

Sediments are deposited in layers ranging from paper-thin sheets to massive beds tens to hundreds of feet thick! A laminae (or lamination) is a layer of sediment or sedimentary rock layer only a small fraction of an inch (less than a centimeter) in thickness (see Figure 6.57). Thin lamination is typically associated with fine-grained sediments deposited in quiet or slack-water environments, such as in a lake basin or offshore below the influence of waves and strong currents. Bedding is the smallest division of a sedimentary rock formation or stratigraphic rock series marked by well-defined divisional planes (bedding planes) separating it from layers above and below (see Figure 6.58).

Figure 6.57. Lamination in shale. Each laminae may be an annual cycle of deposition or a seasonal storm flood event (scale is in mm to cm).	Figure 6.58. Bedding is layers of sediment deposited in an environmental setting on a scale of hundreds to many thousands of years.