During the Permian-to-Triassic transition

a NW-SE-trending paleo-rift

also known as Guangyuan-Liangping paleo-rift

was developed in the Guangyuan-Liangping area of northern Sichuan Basin.The paleo-rift is of great significance to the oil and gas exploration and development in the northern and northeastern parts of the Basin and therefore calls for an in-depth study on its tectonic-sedimentary evolution.A systematic collection and study of outcrops and drilling data from both inside and outside of the paleo-rift

combined with analyses of corresponding sedimentary records

including unconformities

sedimentary filling

abrupt log response changes

and sediment geochemistry

as well as seismic profiles

shows that the sediments of the 3

rd

and 4

th

members of the Maokou Formation extend into the paleo-rift.The absence of an extensive karstification on top of the Maokou Formation in the paleo-rift suggests that

it was sedimentary facies changes

rather than karst erosion

that caused the thinning of the Maokou Formation in the paleo-uplift.The paleo-rift was initially taking shape during the deposition of the 3

rd

and 4

th

members of the Maokou Formation and continued to grow during the Wujiapingian stage.It entered the peak development phase during the Changxingian stage when the extensional rifting and hydrothermal activities intensified and tectonic-sedimentary differentiation escalated.It wasn't until the deposition of the 4

th

member of the Feixianguan Formation that the paleo-rift was completely filled up.The paleo-rift had strong control over the development of the Middle-to-Upper Permian reservoir rocks around it

including the biodetritus beach facies of the Maokou Formation and the grain beach facies in the Wujiaping Formation.Moreover

signs of hydrocarbon migration and accumulation and residual pores in the Wujiaping Formation indicate that the Formation is promising in terms of further hydrocarbon exploration.