苏皖地区石炭系露头层序地层研究

应用露头层序地层学基本原理和方法,在详细的岩石岩相学、沉积学.地球化学研究和精细的地层划分对比基础上,对苏皖地区石炭系地层进行了露头层序地层研究.阐述了沉积层序的各种界面的露头标志,探讨了三级层序和层序区域对比的基本特征.研究表明,苏皖地区石炭系可识别出9种主要岩相、20种微相和11个三级沉积层序.Ⅰ型沉积层序边界识别标志有地表或海底侵蚀、地层上超,界面上下岩性岩相、古生物及氧碳同位素值的突变,界面的区域可对比性等,在研究区主要表现为古风化壳面、古岩溶面、侵蚀面和暴露面四种类型.陆表海盆海水较浅,沉积物常露出水面而遭受侵蚀,形成较多的Ⅰ型层序边界.三级层序发育TST,LST不发育或难以识别。

Study on Outcrop Sequence Stratigraphy of the Carboniferous Strata in Anhui and Jiangsu Province,China

The Carboniferous system exposed from Anhui and Jiangsu provinces,has seven Iithogenetic units. Based on outcrop seguence stratigraphic anaIysis with particuIar attention to the key surfaces or poIyphase paIeokarsts deveIoped in the interruptions of sedimentation,nine types of Iithofacies, twenty types of microfacies and eIeven third-order seguences in the Carboniferous system are recognized. The Iower series of Carboniferous strata have six seguences,and the upper series have five. In the Iower series of Carboniferous strata,Yanguan stage are composed of seguence 1 to 2,and Datang stage from seguence 3 to 6.In the up-per series, Weining stage are composed of seguence 7 to 8, and Maping stage from seguence 9 to 11.According to the fea- tures of the bottom boundary surface,eIeven third - order seguences are cIassified into two sorts of seguence , which are type Ⅰseguence and type ". The bottom boundary surface of type ! seguence aII have cIear signs incIuding the differ-ent thickness eIuviums,the strong paIeokarst,the strata discontinutity,the immense changes of sedimentary patterns and traits,the huge and sudden aIternation of carbon and oxygen isotope vaIues and the disappearence and abrupt changes of organism evoIution. The third-order seguences of S2,S3,S5,S6,S7 and S11 beIong to I-type of sedimentary seguence,and S1,S4,S8,S9 and S10 Ⅱ -type. The third-order seguences are absent at times. The characteristics and genesis of each third-order seguences are described and discussed. The third-order se-guences in various paIeogeographic units and sedimentary environment can be correIated. Sea IeveI change rate and am-pIitude corresponding to these third-order seguences are discussed and highstand systems tracts iike Vaii' s marine seguence modei. Because of the difference of basin texture,fauit activity and materiai suppiy,the main controiied factors of seguence styie were different in steep siope,deep-water area and gen-tie siope. The major controiied factor of seguence styie on steep siope was fauit activity and materiai suppiy,and the nearshore subagueous fan was main sedimentary type；the factor controiied seguence styie in deep water area was reiative change of iake ievei,the sedimentary facies was characteristic of shaiiow-deep iake；the factor controiied seguence styie on gentie siope was reiative change of iake ievei and materiai suppiy,fan-deita or river-dominated deita was major sedi-mentary type. Therefore,the seguence modeis were estabiished separateiy on steep siope,deep-water area and gentie siope. A seguence was made up of iowstand,transgressive and highstand systems tracts with topographic break on gentie siope of Luxi depression. Lastiy,authors anaiyzed the condition of hydrocarbon accumuiation in different seguence frame-work,and pointed out that the iowstand and highstand systems tracts of seguence ! were rich in hydrocarbon resource,and were the main section for finding new hidden traps.