鄂尔多斯晚三叠世湖盆古气候及古水体特征的恢复及其地质意义

Geologic significance of the palaeolatitudinal change and the character of connate water in Late Triassic of Ordos Basin

摘要:

本文研究了鄂尔多斯晚三叠世湖盆古气候变迁及古水体特征。研究结果表明：鄂尔多斯晚三叠世湖盆古纬度为北纬31.03O，比现在所处的纬度（35.1 O）偏南4 O多，推测晚三叠世时鄂尔多斯湖盆气候温暖潮湿，生物繁盛，能够形成有机质丰富的烃源岩。利用泥岩B、Sr、Ba元素测试结果及Sr/Ba比值法，以及岩石碳酸盐岩胶结物稳定同位素分析表明，鄂尔多斯晚三叠世长8期—长6期湖盆是一个淡水湖盆，从长8期—长7期—长6期湖盆水体范围与深度经历了收缩—扩大—收缩的过程，纵向上构成了储层—烃源岩—储层的生储盖组合，从湖盆演化的特征上论证了鄂尔多斯盆地晚三叠世油气勘探的实际意义。

Abstract:

This study presents the palaeolatitudinal change and the character of connate water in Late Triassic of Ordos Basin. The results show that palaeolatitude of Ordos ancient lake-basin in Late Triassic was 31.03ON，it was 4O more than the present latitude. So we can presume the climate of Late Triassic was mildness and humidity,creature got flouring, and organic substance were rich ,which could generated oil source rock of abundant organic substance. Utilizing outcome of test about B、Sr、Ba element in mudstone ,and contrast it with element geochemistry index , Ordos Basin from Ch8 to Ch6 period was freshwater lake basin .The wate area and deepness of lake-basin had experienced course of shrinkage-spread- shrinkage during Ch8 ,Ch7 and Ch6,which constituted reservoir-oil source rock- cap rock in lognitudinal.It is important significance about prospect for oil-gas in Ordos Basin when late Triassic.