| PDF: | |
| Time: | 2017 |
| Journal: | Geoscience Frontiers(Geosci Front) |
| Volumn: | 24 |
| Issue: | 1 |
| Pages: | 265-275 |
| Type: | EI |
| Author: | Xiang GAO,Youfeng GAO,Xuejiao QU,Honghao LI,Tong CHEN,Pujun WANG |
Abstract: | Abstract: China Cretaceous Continental Scientific Drilling in the Songliao Basin, called SK2 project, has collected 365.32m of the lower Cretaceous Yingcheng Formation which corresponds to Aptian-Albian. The borehole got a highly continuous core section with recovery of 98.47%, which is the most complete and precise geological records up to now for the stratum of continental non-marine Cretaceous in the world. The diameter of core is 214mm which is among the largest diameter concerning coring engineering. We first described the volcanic-sedimentary succession in centimeter scale and studied the volcanic and sedimentary facies. Considering the sedimentary and volcanic rocks as a whole sequence, we recognized seventeen rock types from drilling core of the Yingcheng Formation. There are nine types of sedimentary rocks, which include conglomerate, coarse sandstone, medium sandstone, fine sandstone, siltstone, silty mudstone, mudstone, breccia tuffaceous sandstone, breccia-bearing tuffaceous sandstone. There are eight types of volcanic rocks including rhyolite, rhyolitic tuff/pyroclastics/agglomerate, rhyolitic welded tuff, crypto-explosive breccia, andesitic tuff, and tuffite. Sedimentary facies is fan delta dominant which includes five sedimentary microfacies of distributary channels, back swamp between delta, subaqueous distributary channels, subaqueous mouth bar and mudstone of still water. Volcanic facies are explosive facies and effusive facies dominant, which include four volcanic subfacies of air-fall, pyroclastic flow deposits, middle and upper flow subfacies of the effusive one. According to detail description of the Yingcheng sequence, we first recognized three periodic sedimentary and volcanic cycles in the Yingcheng Formation, which have been numbered sedimentary I - volcanic I, sedimentary II - volcanic II, and sedimentary III – volcanic III. This is a new discovery concerning the vertical features of of the Yingcheng Formation. The centimeter scale description on the core sections from the SK2 may provide some other useful information for related researches in the future. Key words: Yingcheng Formation; sedimentary facies; volcanic facies; volcanic-sedimentary succession and cycle; Aptian to Albian; International Scientific Continental Program (ICDP) of the Cretaceous Songliao Basin (SK-2); Songliao Basin |