Organic matter analysis of surface sediment in Buha Estuary region and its comparative sedimentology significance

青海湖布哈河口区与晚三叠世鄂尔多斯盆地及四川盆地具有相似的古地理特征和水体环境，对布哈河口区表层沉积物中有机质的类型和丰度进行研究具有重要的比较沉积学意义.通过对布哈河口区河流、三角洲平原、前三角洲、滨湖、浅湖及半深湖环境表层沉积物样品全岩组分、总有机碳（TOC）及有机质类型进行分析，确定布哈河口区表层沉积物中有机质主要为Ⅱ2型和少量Ⅱ1型，TOC含量不超过4.29%，其中半深湖TOC含量最高并且有机质类型较好.布哈河口区表层沉积物中TOC含量主要受黏土矿物含量、有机质生产力和水深控制，半深湖沉积物具有较高的黏土矿物含量、较高的有机质生产力、较好的有机质类型和较大的覆水深度，有利于有机质的生产和保存，为河口区最有利于烃源岩发育的环境.同时，根据前三角洲、浅湖及半深湖沉积物中TOC含量与水深存在良好的相关性，建立了利用岩石中TOC含量对古水深进行恢复的公式.;The paleogeography characteristics and water environment of Buha Estuary in Lake Qinghai are similar with those in Or-dos Basin and Sichuan Basin in the Late Triassic.The study on the types of organic matter and its abundance in the surface sedi-ment from Buha Estuary is significant to comparative sedimentology.The sediments were collected from river,prodelta,lakeshore,shallow lake and semi-deep lake in Buha Estuary region and were analyzed in aspects of whole-rock composition analysis,total or-ganic carbon (TOC) and examination of the kerogen.The results demonstrate that Ⅱ2 kerogen is the major organic matter type in sediments and only a few Ⅱ1 kerogen exist.TOC content in the sediments is no more than 4.29%,and the samples collected from semi-deep lake generally have high TOC content while the quality of organic matter is better than that of the other places.The clay minerals content in sediments,organic matter productivity and water depth are the major factors that affect the TOC content in the sediments of Buha Estuary.The semi-deep lake is a sedimentary environment which was the most favorable hydrocarbon source place because of its high productivity and good condition for organic matter.At the same time,according to the good correlation be-tween the water depth and TOC contents in sediments gathering from prodelta,shallow lake and semi-deep lake,the formula using the TOC contents has been established for reconstructing water depth.