塔里木盆地石炭系卡拉沙依组旋回地层与层序地层综合研究

塔里木盆地石炭系卡拉沙依组形成于盆地演化相对稳定期的陆表海陆棚环境, 由多层碎屑岩与碳酸盐岩及膏岩相互叠置而成, 是重要的成藏组合之一.根据古生物研究及地层对比, 卡拉沙依组在国际地层表上对应于维宪阶和谢尔普霍夫阶, 时限约为±27 Ma.目前卡拉沙依组层序地层学方面的研究工作尚较薄弱, 由于内部难于识别出明显的古间断面, 有的研究将其划分为3~4个三级层序, 这与其所跨越的地质时限之间存在较大的矛盾.通过频谱分析和小波分析等处理方法对卡拉沙依组的自然伽马、自然电位等测井曲线进行了旋回地层学研究, 同时结合岩心观察及基准面分析, 对塔中及邻近区域的麦6井、中1井、中17井及顺6井的卡拉沙依组地层分别划分出了9~11个层序地层单元, 每个层序的延续时限约为2.40 Ma, 对应于地球轨道3个参数组合形成的天文周期.这在实现精细划分了三级层序的同时, 也在一定程度上反映了此处三级层序成因于天文气候因素的形成机理. 

Cyclostratigraphy and Sequence Stratigraphy on Carboniferous Karashayi Formation of Tarim Basin,China

Carboniferous Karashayi Formation of Tarim basin formed in the continental shelf environment, is composed of several sedimentary assemblages of clastic rocks, carbonate rocks and gypsum rocks. It is one of the important reservoir combination in the Tarim basin. According to the research results of paleontology, the formation can be approximately correlated with the Visean and Serpukhovian Stage of the International Stratigraphic Chart, about ±27 Ma. Currently, the research of sequence stratigraphy on Karashayi Formation is relatively weak. Due to lack of obvious discontinuity surfaces, a limited number of studies have been divided the formation into 3-4 third-order sequences, which leads to a conflict as to the time limits ±27 Ma. In this paper, the cyclostratigraphy was carried on well logs GR (Natural Gamma-Ray Log), SP (Spontaneous Potential Log), U, Th, K, etc. of Karashayi Formation with spectral analysis and wavelet analysis methods. Integrated with core observation and sedimentary base level study, 9-11 third-order sequences were identified in Karashayi Formation of Well Mai6, Zhong1, Zhong17 and Shun6. The average time duration of each cycle is about 2.40 Ma. This value corresponds to the intersection astronomical period of the three Earth orbital parameters. Not only do the results reflect the application value of the method, but also reflect that the climatic cycles are the controlling factors on the development of third-order sequences.