Cyclic sediments

Allocycles are sedimentary cycles caused by processes outside of the depositional system and that involve forced oscillations of the sedimentary system; in this case the cyclic succession registers some features of the forcing process (Sea level fluctuations, climate oscillations or tectonic activity).

[3] Changes in sea level can create cyclic successions of limestones, shales, coals and seat earths.

Seasonal changes in weather can create cyclic sediments in the form of alternating bands of clay and silt (also known as varves).

In winter, melting is at a minimum, meaning that only fine material is supplied to the lake, causing thin clay layers.

One of the fundamental properties of carbonate peritidal successions is the arrangement of subtidal, intertidal and supratidal facies into asymmetric, shallowing-upwards cyclothems or parasequences (Hardie & Shinn, 1986)[4] The Ginsburg model deals with the cyclic successions in the specific case of a tidal flat and lagoon, introducing the important concept that carbonate peritidal cycles may form without external forcing.

The Florida Bay lagoon and the tidal flats of the Bahamas and Persian Gulf are traps for fine sediment produced on the large adjacent open platforms or shelves they face.

Since many times the open marine source areas are larger than the nearshore traps, due to the lack of accommodation space, the sediments' wedge inevitably progrades seaward.

As consequences, the size of the open marine source area decreases and the production of mud is reduced and no longer exceeds slow continuous subsidence.

Ginsburg's assumption is to consider the constant and continuous subsidence in the Bahamas area (passive margins) and to idealize an almost horizontal slope.