Event Deposits And High-resolution Sequence Stratigraphy Of The Upper Cretaceous In Songliao Basin

After 50 years of exploration and the extensive research in the paleo-environment and paleoclimate, paleomagnetism, sequence stratigraphy and petroleum geology and other fields, we achieved fruitful results in the Songliao Basin. But with the deepening of the exploration degree, the detailed study of basin formation is a more urgent needs, the lack of continuous, systematic study sample is the main constraint to the study of the high resolution sequence stratigraphy of the Songliao Basin. The continuous core information of CCSD-SK-I, which from the top of member K1q3 to the bottom of Taikang formation, with 96.46% of core recovery provides unprecedented information for the study of the upper cretaceous event stratigraphy and high resolution sequence stratigraphy of the Songliao Basin.In this thesis, we take the 2485.89 m core information of CCSD-SK-I and outcrop profile as the research object, through the centimeter-level observation and description to the cores and profile, and established the complete centimeter level lithostratigraphic sequence of the Upper Cretaceous in Songlian Basin. Based on lithology, sedimentary structures, containing material and sedimentary sequences characteristics, we systematically identify the development of various types of microfacies, based on which, we systematically study the sequence interface types and identification character. Through high resolution sequence stratigraphy dividing to the CCSD-SK-I and based on the latest chronostratigraphic analyze result of the Songliao Basin, we calculated the time span of base level cycle at all levels and discuss the controlling factors of the formation of the sequence at all levels. The specific research process and understanding, including the following six areas:1,The identification of lithology character and microfacise of CCSD-SK-IThe identification and classification of the whole core section rock types is the base of the whole research, we mainly completed it by the combination of microscopic identification and specimen identification. Through the 2485.89 m core information of CCSD-SK-I, we identified 7 types of rocks after the grain size, including mudstone, siltystone, fine sandstone, medium sandstone, coarse sandstone, fine and medium conglomerate and there are 37 specific lithologies. Then, we identified 8 special lithology, including dolomite, volcanic ash, oil shale, lime mudstone, marlite, recrystalline limestone, ostracode clastic limestone and ostracode limestone.Lithology, structure, content, rock color and the sequence characteristics are considered in identifying sedimentary microfacies. There are five types of sedimentary environments, including meandering river, delta, lakeshore, shallow lake and semi-deep to deep lake in which 29 kinds of microfacies deveoped. The meandering river develops channel lag, point bar, natural levee, crevasse splay, crevasse channel, flooded plain and flooding lake. The delta develops subaqueous distributary channel, mouth bar, interdistributary bay, distal bar and slump sediment. The lakeshore develops sand beach and mud beach. The shallow lake develops mudstone of still water, turbdite, nearshore bar and tempestite. The semi-deep to deep lake develops mudstone of still water, mud limestone, dolostone, oil shale, volcanic ash, turbidite, slump sediment, temperitite, seismite, ostracoda limestone and sparite carbonate.2,Detailed study of outcropsIn this thesis,we selected relatively good outcrop to study the lithostratigraphy, sedimentary facies, sequence stratigraphy and other aspects of research of the southeastern uplift of the Songliao Basin,and through the contrast between drilling the outcrop support the establishment of the Songliao basin stratigraphic framework. The studyed profiles including the Quantou formation profile of Jiejianlin in Changtu County, the Quantou formation profile of Baishanchun of Shanmen in Shiping city, The Qingshankou formation profile along the Songhua River of Qingshankou township in Nong'an County, Yaojia-Nengjiang formation on the south bank of the Songhua river near the Yaojia military station fo Caiyuanzhi Township in Dehuicity and Shifangtai formation in the west of Shifangtai in the shifangtai township of Shuihua city.3,The study of event stratigraphy types and character of CCSD-SK-IDuring the detailed description of CCSD-SK-I, we identified event etratigraphy layers and studyed them, including crevasse fan, crevasse channel, slumping gravity flowing, turbidity current, seismite, volcanic-ash sediment and tempestite-gravity flow sediment. We analyzed the development of various types of event stratigraphy and sedimentary features of the environment and discussed the role of the event stratigraphy and special lithology layers in the high resolution sequence stratigraphy dividing. We believe that crevasse fan and crevasse channel deposits reflect the beginning of the cycle upward deepen of the base level, which generally at the bottom of the cycle; turbidite, submarine slump deposits and seismites are located on top of up lighter base level cycle; the deep lake marl layer of Qingshankou formation and Nenjiang formation at the bottom of the high accommodation space of the upward shallow base-level cycles;dolomite deposits represent a kind of high accommodation space under a high-up shallowing of the base level cycle sequences.4,The research of high resolution sequence stratigraphy of CCSD-SK-IWe used high-resolution sequence stratigraphy theory to study the high-resolution sequence stratigraphy of CCSD-SK-I. We refined the type of sequence boundary, and found the identification of each type, on the basis this and the sequence-level classification and nomenclature, sequence structure and stacking pattern, Sedimentary facies in each group research results. We use five-level classification scheme of sequence stratigraphy including ultra long, long, medium, short and ultra short-term to dividing the high-resolution sequence stratigraphy of CCSD-SK-I.5,The time span of the high-resolution sequence development of CCSD-SK-IWe use the latest multi-stratigraphic division and correlation theme to calculate the time span of base level cycle at all levels, and find that the the average time span of ultra-short cycle sequences has two intervals, one is mainly delta and lakes and have a time span of 10.3 ~ 13.8ka, another is mainly rivers and lakes and have a time span of 24.7 ~ 36.4ka;The average time span of short-term cyclic sequence has different periods based on the different sedimentary facies, Rivers and lakes is 66.7 ~ 88.6ka, lakes and delta is 36.1 ~ 43.2ka, the calculated result of medium-term base level cycle sequence time span is 342.9 ~ 443.8ka.6,The control factors of high-resolution sequence of CCSD-SK-IThe Cretaceous terrestrial strata of Songliao Basin has a complex development, and has various types of base-level cycles sequence, the formation of the sequence at all levels controlled by many factors. Through the discussion of control sequence elements within various types of ultra-short-term base level cycle combined with the calculation of time span of sequence at all levels,we determine controlling factors of cycle at each levels . The results show that ultra-short-term cyclic sequence is subject to lift and drop of the base level, which is also called auto-cycle sequence controlled by A / S value. The short-term cyclic sequence in the river environment, record the cycle of the Earth's orbit inclination rate, the short-term cyclic sequence in the lakes and delta record the Earth's orbit semiprecession. The short-term base level cycle sequences in the river environment controlled by the change between dry and wet climate, which caused by the eccentricity of the short period. The short-term sequence base-level cycles under the lake and delta environment are related with the climate change, which is caused by the earth orbit inclination rate. The formation of medium-term cyclic sequence controlled by the earth's long orbital eccentricity cycles. Long and ultra long-term base level cycle sequences controlling factor is the tectonic activity, followed by an external source input and climate change. At the same time, we can not rule out the input and the source control action of the earth's orbit period on climate change.