Discrimination of two kinds of sedimentary laminae in maar lakes of China

Varved lacustrine sediments have been found from high latitude to low latit ude, even in tropical area. Paleoenvironmental and paleoclimatic research h as increasingly relied on the use of varved sediments to provide high-resol ution geochronologies and climatic reconstructions. However, a special depo sitional environment is necessary for varve formation and preservation. Gen erally, varves can be found in the sediments of maar lakes because of their special geological and hydrological environment. The preliminary research showed that a few carbonate laminations are developed in the Huguangyan maa r lake, south China. They are poorly developed and not annual laminations, and may be related to periodically drought. Diatomaceous laminations are fo und in the maar lakes in northeast China. Diatomaceous laminations with cyc lic nature corresponding with seasonal diatom blooming are the credible nat ural clock.