What is Retrogradation geology?
1. n. [Geology] The accumulation of sequences by deposition in which beds are deposited successively landward because sediment supply is limited and cannot fill the available accommodation.
What causes progradation?
progradation can occur as a result of a sea-level rise accompanied by a high sediment flux (causing a regression). This latter usually occurs during the late stages of the development of a highstand systems tract and/or an falling stage systems tract.
What is progradation process?
Progradation is the diagnostic depositional trend for regressions, and is defined as the building forward or outward toward the sea of a shoreline or coastline (as of a beach, delta, or fan) by nearshore deposition of river-borne sediments or by continuous accumulation of beach material thrown up by waves or moved by …
What occurs during retrogradation?
Retrogradation is a reaction that takes place when the amylose and amylopectin chains in cooked, gelatinized starch realign themselves as the cooked starch cools. Amylose crystallization occurs much faster than crystallization of the amylopectin.
What is the difference between gelatinization and retrogradation?
Gelatinization and retrogradation are properties of starch that vary with heat. The key difference between gelatinization and retrogradation is that gelatinization refers to the act of making or becoming gelatinous, whereas retrogradation refers to the motion in a retrograde manner.
What is Aggrading river?
Aggradation (or alluviation) is the term used in geology for the increase in land elevation, typically in a river system, due to the deposition of sediment. Typical aggradational environments include lowland alluvial rivers, river deltas, and alluvial fans.
What is regression geology?
A marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously-exposed land.
What is an example of retrogradation?
When starchy foods—rice, pasta, bread dough—are cooked in the presence of water, all those individual granules of starch absorb water and swell up. The amylose and amylopectin molecules in the granules, formerly clinging together, relax a bit and come apart, allowing water to seep in among them.
Is retrogradation good or bad?
Starch retrogradation has been the subject of intensive research over the last 50 years, mainly due to its detrimental effect on the sensory and storage qualities of many starchy foods. However, starch retrogadation is desirable for some starchy food products in terms of textural and nutritional properties.
What happens during retrogradation?
Retrogradation is an ongoing process, which initially involves rapid recrystallization of amylose molecules followed by a slow recrystallization of amylopectin molecules. Amylose retrogradation determines the initial hardness of a starch gel and the stickiness and digestibility of processed foods.