Varve dating method

The alternating layers of dark and light count the years like tree rings.The sedimentation or annual varve thickness is relatively uniform, typically 1.2 mm per yr for present conditions in Lake Suigetsu which is located near the coast of the Sea of Japan.These varves are found more in vegetated temperate regions.In the spring nutrients promote blooms of diatoms, a type of algae encased in a silica cell wall that fossilizes in sediments.There are some characteristics of lakes that help set up the necessary conditions.

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However, there are often inconsistencies or periods of missing layers. Each spring, tiny plants bloom in Lake Suigetsu, a small body of water in Japan.When these one-cell algae die, they drift down, shrouding the lake floor with a thin, white layer.Also, lakes that are thermally stratified, separated into a warm upper layer and a cool bottom layer, for long periods of time can lead to the cool lower layer becoming anoxic (lacking oxygen).This can prevent the organisms that can mix the sediment from becoming established (O’Sullivan, 1983).

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