ZHOU Yue,born in 2000,is a master degree candidate. She is mainly engaged in sedimentary geology research. E-mail: mialboxzoye@163.com.
The Taiyuan Formation of Ordos Basin is a mixed depositional system of coal-bearing paralic facies developed under an epicontinental sea setting. Current inconsistencies in the understanding of its mixed depositional system,as well as unclear mixed characteristics and controlling factors,have constrained the exploration and evaluation of high-quality reservoirs such as tight limestones and tight sandstones. Based on systematic observations of cores,thin sections,and outcrops of the Taiyuan Formation in the eastern basin,combined with well logging and mud logging data,this study conducted an in-depth analysis of the cyclicity,lithofacies,and lithological characteristics of the Taiyuan Formation. Through a systematic examination of multiscale mixed depositional features and patterns,the main controlling factors and formation processes were clarified,and a mixed depositional model was established. The Taiyuan Formation in the study area constitutes a relatively complete third-order sequence,which can be subdivided into five fourth-order sequences,recording a relatively full transgressive-regressive cycle. The fourth-order sequences exhibit a binary structure of transgressive and highstand systems tracts. The transgressive systems tract is dominated by carbonate platform deposits,with local development of deltaic and barrier sandbar sand bodies,while the highstand systems tract is primarily composed of tidal flat and lagoon deposits. The Taiyuan Formation exhibits mixed deposition at three scales: Cyclic mixing at the macro-scale,primarily controlled by high-frequency sea-level fluctuations and their amplitudes,reflects the influence of temporal periodic changes on mixed stacking patterns;Contemporaneous heterotopic facies mixing at the meso-scale,governed by terrigenous clastic supply,carbonate productivity,and depositional topography,highlights the constraints of spatial environmental variations on the distribution of endogenic and exogenic sediments;and Component mixing at the micro-scale,mainly regulated by terrigenous clastic input,hydrodynamic conditions,and physicochemical factors,reflects the control on the distribution of mixed sedimentary components. The mixed deposition in the Taiyuan Formation is characterized by multiscale development,multi-factor synergy,and dynamic evolution of depositional environments.
| 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 |