塔里木盆地海相古生界化学地层学研究

在许多地质条件下，低镁方解石质的海相碳酸盐岩能保存其原始的化学元素和同位素组成，化学地层学与生物地层学相结合，有可能成为远距离、大区域之间海相地层精确划分与对比的工具。塔里木盆地英买力、轮南和塔中地区下古生界缺乏标准化石，重要油气产层（东河塘组）的时代归属长期难以定论。选择古生物地层学研究较详细的柯坪地表剖面，建立其下古生界稳定同位素组成曲线，与塔中、轮南地区钻井剖面下古生界稳定同位素组成曲线对比，参考微体古生物证据，较精确地划分了中、上奥陶统与下奥陶统的界线。根据塔中地区探井中极少量牙形石化石分布，在泥盆系与石炭系可能的分界线附近集中采样分析，建立化学元素分布曲线，与化学生物地层学研究较详细的２条华南古生界剖面（贵州长顺县睦化剖面，湖南祁阳县黎家坪剖面）对比；根据３条剖面都出现的Ｓｒ元素含量异常与华南剖面标准化石带的关系，确定塔中地区泥盆系与石炭系的分界线位于东河塘组顶面之上５１．５ｍ处。图３参７（梁大新摘）

A chemostratigraphic research on marine Paleozoic sediments in Tarim basin.

The original chemical elements and stable isotopes within low Mg calcite marine carbonate rocks could be excellently preserved under many geological conditions. The connection between chemostrati graghy and biostratigraphy will be able to be a tool for long range and high resolutional stratigraphical correlation of marine sedimentological horizon. In Tarim basin, no standard fossils have been found in the Lower Paleozoic horizon of Yengimahalla, Lunnan and Tazhong (center of Tarim basin), and the age of important oil and gas producing strata (Donghetang Formation) have not been identified for a long time. By combing stable isotopic and biostratigraphic (micro fossils) methods and marks, the Lower Paleozoic on both outcrop section (Keping) and drilling section of Tazhong and Lunnan have been excellently correlated and the boundary of Middle Upper Ordovician can be rather accurately identified and correlated. According to a chemostratigraphical study (Sr element abnormal shift) on a section of Tarim basin and two sections of Muhua, Guizhou province, Lijiaping, Hunan province, South China, in which late two have relative integrated fossils assemblage, so the Devonian Carboniferous boundary (i.e. the international agreed praesulcata sulcata boundary) may be defined at the level 51.5m above the top of Donghetang Formation of Tarim basin. Subject