Full
LI Yonglin,born in 1996,Ph.D. candidate,is engaged in researches on sedimentology and geochemistry. E-mail: liyonlin0702@163.com.
Outline
The sedimentary environment of the Pinghu Formation in the BW area of the Xihu sag has long been controversial. In this study,19 mudstone samples were collected and analyzed for trace elements and rare earth elements(REEs)using two methods: conventional whole-rock total digestion and selective acetic acid extraction. Based on the geochemical data obtained,multiple proxies were integrated to systematically analyze the redox conditions,paleoclimatic characteristics,and paleosalinity evolution during the depositional period of the Pinghu Formation. The results show that: (1)Element concentrations obtained via acetic acid extraction are significantly lower than those from whole-rock digestion,but both methods reveal consistent elemental distribution patterns. Moreover,the acetic acid extraction method is proven to be more effective than conventional whole-rock digestion when applying specific elemental proxies to identify sedimentary environments,especially for distinguishing terrestrial and marine facies.(2)The redox conditions during the depositional period of the Pinghu Formation were predominantly suboxic to oxic,indicating a relatively oxidizing environment;paleoclimate and paleosalinity evolved concurrently,characterized by an initial warm and humid freshwater setting,which shifted to an arid and saline environment by the end of the early stage. This was followed by a transition to a warm and humid brackish setting in the middle stage,a return to arid and saline conditions by the mid-stage,and finally a return to a warm and humid freshwater environment in the late stage. In light of the sedimentary context of the study area,the synchronous variations in paleoclimate and paleosalinity are interpreted as recording four successive changes,collectively indicating at least two major marine transgressions during the depositional period of the Pinghu Formation. The above results have significant scientific guiding significance and application value for deepening oil and gas exploration in the Xihu sag of the East China Sea Shelf Basin.
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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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