Jurassic is very thick and has a complete sequences in Quemocuo area

northeastern Qiangtang basin.The Quemocuo Formation and Xueshan Formation

the earliest and latest Jurassic deposits

both presently have a remaining thickness of over 1300m

representing the apparent local subsidence-accumulation centers of the times in the basin. These two subsidence-accumulation centers have very similar development background and evolution process

i.e. there are the evidences of early-stage thermal-magmatic activity and relevant uplifting backgrounds

subsequently

the uplifted areas where the early deposits being thin or even denuded have subsided rapidly and accumulated very thick deposits. The special phenomena that uplifts and depressions occur successively in time and are superimposed vertically are characteristic of structures having been formed by thermal activity.This unique feature shows that Quemocuo area has experienced two geologic processes:(1) humping up of deep thermal-magmatic activity

magmatic eruption

and uplifting and denudation of superficial and shallow crust in early stage; (2) thermal attenuation and cooling down at depth and caving in and depression of superficial and shallow crust in late stage. The deep structures revealed by aeromagnetic survey and magnetotelluric depth sounding data acquired in recent years verify the existence of this thermal subsidence structure. The vitrinite reflectance(R

0

)of Upper Jurassic Xueshan Formation ranges from 1.63%to 1.83%

providing evidences for the Mesozoic thermal anomaly. The thermal attenuation and accompanying magmatic activities had lasted till Late Cretaceous-Early Tertiary. Later

this area was uplifted and cooled down.