摘要
前陆复杂构造区因构造变形强烈,地层缺失严重,'断相'、'古隆起'假象等因素,导致了前陆区岩相古地理制图具多解性.以鄂尔多斯西缘二叠系山西组和下石盒子组岩相古地理恢复为例,提出古构造复原、物源区分析是重建岩相古地理的重要环节,指出:西缘北部早中石炭世为走滑拉张断陷;二叠纪沉积时存在3大物源区;中生代的冲断推覆造成地层缩短率20%～47%.恢复后的岩相古地理图在沉积体系展布、砂体分布等方面和恢复前相比,有明显差异,对指导西缘地区上古生界天然气勘探有意义.
Lithofacies paleogeographic mapping is a key to paleogeography reconstruction. The mapping has various interpretations in foreland areas because of strong deformation, strata hiatus, facies-break and pseudomorphs of paleo-uplift. This paper puts forward a five-steps method to reconstruct paleo-structure in the foreland areas. First, it is necessary to reconstruct structures at 3 key stages： pre-depositional, syn-depositional and post-depositional paleo-structures. Secondly, the distribution and mapping of sedimentary systems should be studied in isochronous stratigraphic framework by the integrated analyses of drilling, log and seismic data. Thirdly, the source area analysis is a tie of distribution of sedimentary systems between basin and orogenic belts. Fourthly, the original strata distributions are restored by reasonably choosing reference points. Finally, the reasonable lithofacies and paleogeographical mapping can be made after all these works mentioned above. This paper takes the Permian Shanxi Formation and Xiashihezhi Formation in the west margin of Ordos Basin as examples to reconstruct lithofacies paleogeography on the basis of paleo-structure restoration and source area analyses by the above five steps. The study shows that there was a slide-tension fault depression in the north of west margin of Ordos Basin at the early and middle Carboniferous periods, there were three source areas at the Permian period, and the Mesozoic thrusting resulted in 20% to 47% strata shortage. The distribution of sedi- mentary systems and sandbodies after the restoration of lithofacies and paleogeography differs greatly from that before the restoration, and this will be significant to guide the Upper Palaeozoic gas exploration in the west margin of Ordos Basin.
出处
《现代地质》
CAS
CSCD
北大核心
2005年第3期385-393,共9页
Geoscience
基金
国家重点基础研究发展规划项目(2001CB20900)。
关键词
古构造复原
岩相古地理
平衡剖面
物源区
二叠系
鄂尔多斯西缘
paleo-structure reconstruction
lithofacies paleogeography
balanced cross-section
source area
the Permian System
the west margin of Ordos Basin
作者简介
汪泽成，男，高级工程师，博士，1966年出生，石油地质学专业，主要从事石油天然气勘探与综合研究工作。
