单词	varve
释义	varve /vɑːv / noun Geology A pair of thin layers of clay and silt of contrasting colour and texture which represent the deposit of a single year (summer and winter) in a lake. Such layers can be measured to determine the chronology of glacial sediments.Each summer/winter pair of layers - called varves - would thus represent a single year.... The basal, coarse layer of a varve is commonly overlain by microlaminared silt and clay, reflecting variable streamflow during summer. Analysis of varves (banded sediments in lakes that show annual variation) can be used to date Pleistocene sediments. Derivatives varved adjective ... Silt and varved clay, probably deposited during the last stages of Pleistocene glaciation, cover the entire floor. In glacial terrains coarse-grained, so-called Gilbert-type deltas of gravels and sands are common, and these pass in deeper water into varved sediments. Sediments in many proglacial lakes are varved (annually laminated) and thus offer the same temporal resolution as trees for paleoenvironmental studies. Origin Early 20th century; from Swedish varv 'layer'.
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