Study on Miocene stromatolites genesis and related paleo-environment in Qaidam basin

In western Qaidam basin, abundant Tertiary lacustrain stromatolites have been discovered recently in several kilometers Miocene strata from lower member of lower Ganchaigou Formation to lower Youshashan Formation in Ganchaigou area. The stromatolites, greatly variable in type and genesis, may partly reflect the Precambrian analogues and further be in contrast with the modern stromatolites, therefore it is of important significance for the international stromatolite research. According to the recent study and trend,the stroma to lites in western Qaidam basin may be classified as skeleton,agglutinated and fine-grained types which also imply different genesis. The skeleton stroma to lites is formed through microbially biological mineralization and calcification combined within-situ precipitation;the agglutinated stroma to lites a remainly related with binding and trapping performed by prokaryotic and eukaryotic algae together;and the fine-grained stroam to lites are mainly formed through biofilm calcification,over-saturated calcite precipitation on the biofilmand microbial chalk precipitation.