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Varved sediments provide an imperfect record of changes in climate by means of variations in varve thickness. Erratic varve thickness pulsations with about 2 to 30 years between maxima agree with similar fluctuations in meteorologic records and show no strong periodicities according to power spectrum studies. However, weak rapidly changing climatic patterns are generally present with a slight favoritism for periodicities near 5 years.
Normally, varves form in quiet places that are relatively insensitive to the short climatic oscillations, but three sequences (Devonian Beaverhill Lake Formation, Oligocene Florissant lake beds, Miocene Monterey Formation) have yielded some information about them and about certain aspects of bedding. The short-term changes (2 to 30 years) are at least partially responsible for the timing of severe storms and floods that scour the bottom or shed coarse clastic layers into a basin.
Subtle varve thickness trends with a tendency toward quasiperiodicity near 90 and 180 years that may be related to solar activity have been observed, and varve calibration of bedding features formed in quiet low energy situations suggests that low energy (Fondo) bedding couplets on the scale of 1 cm to 3 dcm are the result of 100-300-year climatic changes. Bedding features of the same and larger scale formed in higher energy environments are under the influence of the shorter, more erratically timed, climatic fluctuations.
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