if sea level rises and the rate of sediment flux exceeds the sea level rise, then progradation results.if sea level rises and the rate of sediment flux matches the sea level rise, then aggradation results.if sea level rises and there is a low rate of sediment flux, then retrogradation results.if the sea level rises and there is a zero or low sediment flux, then transgression results.Resulting patterns reflect accommodation space and rate of sediment influx: Thus, accommodation space, the potential space available for sediment to fill is determined from the combined movement of:Īccommodation - the filing of accommodation space with sediment - is a function of: Can vary with climate even when tectonic activity is constant. Relative sea level: The distance between some lithospheric reference horizon (like the sea floor bedrock) and the sea surface is called relative sea level or accommodation space.Tends to vary with mid-ocean ridge activity Eustatic sea level: Depth of the ocean with respect to the center of the Earth.The Quaternary ice ages when the actual volume of sea water diminished.īecause these processes differ, we have two ways of thinking of sea-level: E.G The Cretaceous highstand resulted from accelerated plate tectonics, causing the sea floors to puff up topographically. ![]() Tectonic activity: uplift or subsidence of the ocean floor relative to the center of the Earth.Over long time scales (10 5 to 10 8 years), sediment accumulation is strongly controlled by changes in Eustatic sea level - The depth of the ocean with respect to the center of the Earth. The only reasonable process that could be responsible is global sea level change. The global similarities in transgressive-regressive cycles are unlikely to have been controlled by local tectonics and thus must have a global cause. Global analysis shows that the major sequences of North America appear (to varying degrees) in other regions of the world. Aggradational: facies remain in the same general location and stack atop others of the same facies.Retrogradational: deeper water deposits move towards land and overlie shallow water deposits.Progradational: shore and nearshore deposits move outward into the ocean and overlie deeper water deposits.Regression: ocean moves away from shore result of sea level fall.Transgression: ocean moves towards shore result of sea level rise.Sequence stratigraphy was introduced by Laurence Sloss as the Sloss cycles. Natural intervals of sedimentary history that may cross bio/lithostratigraphic boundaries. ![]()
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