Characteristics And The Times Discussion Of Baiyingaolao Formation In The Northern Of Great Xing'an Rang

Volcanic rock of Baiyingaolao formation in north Great Khingan is Widely distributed.But stratigraphic structure and Era of belonging have been controversial.This artical Through comprehensive study.We think Baiyingaolao formation in north Great Khingan mainly is acidiic volcanic rock.Different volcanic institutions stacking thickness and stratigraphic structure have big difference.It can be divided into three lithologic section.The first section mainly is rhyolitic ignimbrite.The second section include tuffite,tuffaceous sandstone and zeolite.The third section include Chondrules rhyolite,black obsidian and perlite.The relationship between Manitu formation trachyte and older geologic body is eruption unconformity.On which is Meiletu formation mudstone and trachyandensite.They are disconformity relationship.Three rock section of Baiyingaolao formation react the process of volcanic action.First section is the production of strong eruption,and this is Pyroclastic flow accumulation belong Peak period of caldera activity.The second section is Eruption-sedimentary facies,and this is volcanic crater lake's iconic rock.The third section is near crater phase accumulation,and this is Broken volcanic period of resurrection parasitic lateral volcanic eruption result.Baiyingaolao formation Stratigraphic structure react broken volcano experience early violent eruption,Collapsed volcano crater formation,late breaking the resurrection collapse crater formation,late breaking volcanic evolution process of the evolution of the resurrection process.Baiyingaolao formation second section in north Great Khingan is Fossil occurrence horizon.Fossils mainly output in gray tuffite of Aershan town and gray tuffite of Handagai pasture.fossil assemblage include bivalve: Ferganoconcha curta,F.sibirica Chern,Eosestheria sp,Phoenicopsis sp,Pityophyllum sp,Carpolithus sp..Eosestheria is an important part of Jehol Biota,and era is early Cretaceous.Different sotopic age research indicate that Baiyingaolao volcanic age in north Great Khingan belong early Cretaceous.K-Ar age is 105-115 Ma,U-Pb age is124-138 Ma,U-Pb age test results are 121±0.5,135±0.8.Combining fossils,lithological association and contact relation,we confirm that volcanic rock age of Baiyingaolao in north Great Khingan is early Cretaceous.