ZHU Jiaqi,born in 2001,is a master’s degree candidate at the School of Resources and Environment,Henan Polytechnic University. Her main research interest lies in storm deposits. E-mail: lychee080925@163.com.
This paper investigates storm deposit characteristics in tidal flat environments of the Early Ordovician Yeli Formation in southern North China to elucidate their implications for palaeolatitude and palaeoclimate. Through comprehensive field sedimentological observations and carbonate microfacies analysis,five distinct microfacies were identified: intraclastic dolomite,quartz-bearing sandy dolomite,sandy dolomite,medium-crystalline dolomite,and fine-crystalline dolomite. These microfacies,combined with macroscopic sedimentary features,indicate an environmental transition from subtidal through intertidal to supratidal zones. Storm-generated sedimentary structures include scoured surfaces,storm gravel layers,graded bedding,massive bedding,hummocky cross-stratification,rip-up clasts,load and flame structures. Through systematic analysis of structure-environment relationships,six distinct storm deposition sequences were classified based on their formative hydrodynamics: subtidal vortex-dominated,subtidal combined vortex-wave,intertidal hybrid gravity flow-wave,intertidal debris flow,intertidal vortex-controlled,and supratidal tidal current sequences. The established depositional model demonstrates that storm flow dynamics primarily controlled the sequence architecture. The recorded increase in both storm frequency and intensity during the Early Ordovician corresponds to a climatic warming phase within the broader cooling trend. Regional synthesis indicates the eastern North China Block margin faced an open ocean at paleolatitudes of 15°~24°S. The research results not only deepen the understanding of the storm deposition sequence,but also provide key sedimentary data for the reconstruction of the Early Ordovician palaeoclimate and palaeogeography in southern North China.
| 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 |