THE JURASSIC DELTA DEPOSIT SYSTEM TRACT AND SEDIMENTATION MODEL IN THE WESTERN SICHUAN FORELAND BASIN, CHINA

The Jurassic is built of continental clastic deposited sediments in the western Sichuan foreland basin.Its deltaic depositional system is branched out into lake fan delta system and lake delta system.The lake fan delta system,which mainly existed in the Upper Jurassic Suining Formation and Lianhuakou Formation,is made up of fan delta plain subfacies,fan delta front subfacies and prodelta subfacies.The lake delta system,which mainly distributed in the Upper Jurassic Penglaizheng Formation and so on,can be divided into two kinds:apical axis delta and brachy-axis delta,and included delta plain subfacies,delta front subfacies and prodelta subfacies.Sedimentation model of the Jurassic in the western Sichuan foreland basin had two kinds,they are alluvial fan-river (alluvial flat)-delta-lake-lake floor fan model and alluvial fan-fan delta-lake-lake floor fan model.