Rhythmite
Encyclopedia
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
or sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
which are laid down with an obvious periodicity and regularity. They may be created by annual processes such as seasonally varying deposits reflecting variations in the runoff cycle, by shorter term processes such as tides, or by longer term processes such as periodic floods.
Rhythmites serve a significant role in unraveling prehistoric events, providing insights into sea level change, glaciation change, and earth's orbital variations which serve to answer questions about climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
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Annually laminated rhythmites
Annually laminated deposits or varveVarve
A varve is an annual layer of sediment or sedimentary rock.The word 'varve' is derived from the Swedish word varv whose meanings and connotations include 'revolution', 'in layers', and 'circle'. The term first appeared as Hvarfig lera on the first map produced by the Geological Survey of Sweden in...
s are rhythmites with annual periodicity: annual layers of sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
or sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
are laid down through seasonal variations that result from precipitation, or from temperature, which influences precipitation rates and debris loads in runoff. Of the many rhythmites found in the geological record, varves are among the most important and illuminating to studies of past climate change. Varves are amongst the finest resolution events easily recognised in stratigraphy
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
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Periodically laminated rhythmites
Tidal rhythmites
Geologic tidal rhythmites display layered Carboniferous Period beds which record tidal cyclical events such as semi-diurnal, diurnal or neap tide, spring tide cycle. The geologic record captures layered beds comparable to those found currently in sediments in the Bay of FundyBay of Fundy
The Bay of Fundy is a bay on the Atlantic coast of North America, on the northeast end of the Gulf of Maine between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine...
in Canada and the Bay of Mont Saint-Michel
Mont Saint-Michel
Mont Saint-Michel is a rocky tidal island and a commune in Normandy, France. It is located approximately one kilometre off the country's north-western coast, at the mouth of the Couesnon River near Avranches...
in France.
The Storm Mountain area of Big Cottonwood Canyon
Big Cottonwood Canyon
Big Cottonwood Canyon is a canyon in the Wasatch Range southeast of Salt Lake City in the U.S. state of Utah. The -long canyon provides hiking, biking, picnicking, rock-climbing, camping and fishing in the summer. During winter, its two ski resorts, Brighton and Solitude, are popular among skiers...
has rhythmites which record sea-level sedimentary deposit fluctuations consistent with the cycle of the tides.
Proglacial rhythmites
One common mechanism is the episodic flooding which results from glacial dam bursts. In one such example geologists estimate that the Missoula FloodsMissoula Floods
The Missoula Floods refer to the cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age. The glacial flood events have been researched since the 1920s...
cycle of flooding and reformation of the lake took an average of 55 years and that the floods occurred approximately 40 times over the 2,000-year period between 15,000 and 13,000 years ago. Distinct rhythmites with an approximately 55-year periodicity have been observed.