GEOHISTORY MODELLING OF CRATONIC BASINS: A CASE STUDY OF THE ORDOS BASIN, NW CHINA

This paper describes geohistory modelling as applied to the intracratonic Ordos Basin in NW China; corrections for compaction, the restoration of unconformities and the effects of tectonic subsidence are discussed.The thickness of a modelled layer of sediments can be determined at any time in the past by taking account of a correction for compaction. Also, the effects of eroded layers can be restored automatically if various assumptions are made. Regional studies indicate that the amount of tectonic subsidence in the Ordos Basin can be calculated using a flexural isostatic model (i.e. of regional compensation).The geohistory of Well QS2 in the Ordos Basin was determined, as was that of a 650‐km long, east‐west cross‐section in the centre of the basin, using a modelling programme run on a PC. The results indicate that the Ordos Basin (and possibly also other intracratonic basins) have the following characteristics: first, rates of sedimentary accumulation, total basement subsidence and tectonic subsidence were relatively low; secondly, basement subsidence is dominantly controlled by tectonism; thirdly, the location of the depocentre changes over time; and finally, the intensity of erosion varies in different parts of the basin.