PROSPECT FOR EXPLORATION TARGETS IN SMALL—MEDIUM JURA—CRETACEOUS BASINS, NORTH CHINA

In the north China intraplate,Jura-Cretaceous basins could occur in a form of either an extensionalfaulted or depressed basin in synrifting(or post-rifting)or strike-slip foreland,or a strike-slip pull apartbasin during synorogeny(or post orogeny),whose formation was controlled by Mesozoic tectonic movements.Corresponding to a warm and humic paleo-climate,limnetic sediments were developed in the basin,which became basins' material basis.The relative late intraplate orogeny caused the expulsion,migration,and accumulation of hydrocarbons,which were entrapped to form into the petroleum structural belts discovered up to now.In such a basin,the reservoir assemblages consist of Jura-Cretaceous strata and thestructural traps(pop-up anticline,fault block flexure or block fault-rolling anticline)on relative upliftedor lowly embossed parts close to the down-warping source region should be regarded as petroleum exploration targets.