柴达木盆地北缘中生界剥蚀厚度恢复

认为地层剥蚀厚度能否根据压实规律来恢复,其决定因素并非是新沉积层厚度是否大于剥蚀厚度;当不整合面以上新沉积层对不整合面以下老地层施加的压力大于被剥蚀地层(剥蚀前)对不整合面以下老地层施加的压力时,不整合面以下老地层的压实规律被破坏,无法用声波时差法恢复剥蚀厚度,否则可以恢复。据此,以用声波测井资料恢复的地层剥蚀厚度为依据,结合未被剥蚀地层厚度趋势延伸法、盆地构造演化分析法,对柴达木盆地北缘中生界剥蚀厚度进行了恢复,认为柴达木盆地北缘剥蚀量从西向东增大,昆特依坳陷和冷湖构造带的剥蚀量(约500m)大于其东部南八仙、鱼卡等地区(约100m),潜西—冷湖四号地区剥蚀量最大(最大可超过1400m)。图5参4(梁大新摘)

The recovery of Mesozoic formation erosion thickness in the north margin of Qaidam basin.

The critical factor affecting the recovery of formation erosion thickness is that whether the pressure, which is exerted by the formations above the unconformity to the formations below it, is greater than that exerted by the erosive formation, not that the thickness of formations above the unconformity is thicker than the erosive formation thickness. This is a new point of view in this paper. It is suggested that when the pressure exerted by the above new formations is greater than that exerted by the erosive formation, the compaction regularity in the formations below the unconformity was altered, that made it impossible to use acoustic (interval) transit time to recover the erosive thickness. Otherwise, it is possible to do so. According to the point of view, with the combination of the unerosive formation thickness trend method and the basin tectonic evolution analytical method, the Mesozoic erosive thickness in the north margin of Qaidam basin has been recovered, and which increases from west to east. The erosive thickness (about 500m) of Kunteyi depression and Lenghu structural belt is large than that (about 100m) of Nanbaxian and Yuka area, and which of Qianxi Lenghu No.4 area is the largest (may be over 1400m).