Cenozoic Uplift And Exhumation Process In Sanjiang Area Heilongjiang Province

The Sanjiang Basin is located in and between the Yishu fault,the Dunmi fault and the Nada-nhada terrane.It is a special location affected by the movement of the north part of Tanlu fault and the Pacific plate.The Cenozoic evolution of Sanjiang basin is in response to the Tanlu fault activity and the Pacific plate insertion.There are a lot of positive topography in Fujin area and Raohe area of Sanjiang Basin.The uplift and exhumation process of this positive topography expressed the evolution of the Sanjiang basin.In this paper,the Sanjiang Basin is studied for further evidence of the uplifting in this area.Basin characteristics analysis,LA-ICPMS apatite fission track dating and thermal history simulation were carried out for the Cenozoic uplift and exhumation research of Sanjiang Basin.The basin is very sensitive to tectonic activity,with sensitive geomorphic index which indicating the tectonic activity and evolution stage.In this paper,the area elevation integral(HI),elevation,slope and relief are extracted from ArcGIS platform through a 30 m resolution digital elevation model of Sanjiang area.From these geomorphic parameters,the HI value of the whole Sanjiang area is less than 0.35,but it is gradually lower from south to north,indicating that the Sanjiang basin is in an old stage,with a small geomorphic changing.The determination of the fission track dating and the qualitative analysis of the elevation of the apatite samples collected in the Sanjiang area shows that there is a stage of basin uplift in the study area at about 25 Ma.Also the fission track dating of apatite and the thermal history simulation express that the study area has been uplifting at high speed since 10 Ma.The high-speed uplift and geomorphic evolution in the study area since 10 Ma is in the old stage,this shows us that the present landform of Sanjiang area might be caused by high-speed uplift and rapid denudation.It is consistent with the climate background of large precipitation,river development and strong denudation in the study area.The Cenozoic uplift,combined with the regional background shows that the regional uplift event at 25 Ma was due to the northern part of the Tanlu fault which was left-handed strike-slipped from right-handed strike-slip;the regional uplift event was accelerated by the movement of the Pacific plate since 10 Ma.