Surfaces between layers of sediments (bedding planes) are usually deposited in horizontal sheets, but cross-bedding is inclined. Cross bedding is very common in beach deposits, sand dunes, and river deposited sediment. Note that reverse graded bedding cannot occur as current velocity increases, because each layer will simply be removed as the current achieves a velocity high enough to carry sediment of a particular size. Graded bedding results when a sediment-laden current (such as a turbidity current) begins to slow down. Cross-bedding or cross-stratification is an arrangement of beds or laminations in which one set of layers is inclined relative to the others.
Surfaces between layers of sediments (bedding planes) are usually deposited in horizontal sheets, but cross-bedding is inclined. Graded beds are horizontal and are usually sorted from coarse at the bottom to fine at the top. GRADED BEDDING Turbidites:The lower part (a-b-c) of a Bouma sequence: the interval a is constituted by massive bedding; the interval b by parallel, horizontal lamination; the interval c by cross-bedding and convolute lamination. One of the most common types of bedding is called graded bedding.
Cross-Bedding and Graded Bedding. For carbonates, cross-bedding is often the most useful for topping, where it can be found. Fossils preserved in growth position are relatively rare. The development of normally graded bedding requires transport of multiple sediment sizes both in suspension, and as bottom or traction loads, which subsequent to flow energy subsidence, settle out in order of weight and density. Assymmetrical features, such as cross or graded bedding, are used to determine whether the beds have been rotated more than 90 degrees –overturned.
What Is The Difference Between Graded Bedding And Cross-bedding?
Posts about cross-bedding written by richardwilliamsgeologist. Within most of the rocks you can find examples of graded bedding, where the grains in each layer are coarser at the base and become progressively finer towards the top, as in the image below.