The hiatus surface of Neogene-Eogene in Jiyang Depression is situated between underlying erosion and overlap strata.Under the boundary

there were sediments formed in faulted depression and were eroded due to tectonic uplift.The stratigraphic ages of the sediments gradually changed from Archeozoic on uplifts to Mesozoic and Cenozoic in sags; the stratigaphic connection changed from nonconformity to parallel unconformity;the erosion amounts changed from 6 000-8 000 m on uplifts to less than 100 m in sags.On the the boundary

there were sediments formed in depression.The lower part of Guantao Formation is filled in deposit

the upper part is drape deposit covering all uplifts and sags.These properties indicate that the depression underwent the evolution process of fault subsiding→sloping→uplifting→eroding→subsiding.