Full
CHEN Mengran,born in 1999,is a Ph.D. candidate at School of Earth Sciences and Surveying Engineering,China University of Mining and Technology(Beijing),majoring in Geology. E-mail: 2544760899@qq.com.
Outline
This study investigates the sequence stratigraphy,palaeogeography,and coal accumulation patterns of the coal-bearing Xishanyao Formation of the Middle Jurassic in the Taibei sag of Tuha Basin,utilizing outcrop profiles and drilling core data. The Xishanyao Formation in the Taibei sag is divided into two third-order sequences,sequence I corresponds to the first and second members of the Xishanyao Formation,while sequence II corresponds to the third and fourth members. Based on a series of contour maps of lithological parameters such as stratigraphic thickness,sandstone thickness,and sandstone-to-mudstone ratio,the palaeogeographic outlines of the two third-order sequences are reconstructed. The northern and southern parts of the Taibei sag primarily were dominated by braided river deltas and meandering river deltas,while the central area was characterized by lacustrine environment. The provenance came from the northern Bogda Mountains and the southern Juelotag Mountains. From the first and second members to the third and fourth members of the Xishanyao Formation,the Taibei sag underwent a transition from swamp-dominated(sequence I)to lacustrine conditions(sequence Ⅱ),characterizing a fluvio-lacustrine sedimentary environment. The most intensive peat accumulation occurred in the second member of the Xishanyao Formation within sequence I,with the coal accumulation center located in the northern foothills of the sag,especially in the Kekeya area,which was situated in palaeogeographic settings such as delta plains and peat swamps. In contrast,coal accumulation in sequence II was weak,with only thin or no coal seams developed. The results of this study on sequence stratigraphy,palaeogeography,and coal accumulation patterns provide a theoretical basis for coalbed methane exploration and development,as well as for the evaluation and selection of exploration blocks in the Taibei sag.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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