扬子地块东南古生代上升流沉积相及其与烃源岩的关系

RELATIONSHIP BETWEEN PALEOZOIC UPWELLING FACIES AND HYDROCARBON IN SOUTHEASTERN MARGINAL YANGTZE BLOCK

长江中下游苏、皖、赣、鄂一带属古生代扬子地块被动大陆边缘的东南缘 ,通过该区 6 4条古生界剖面的实测、分析和对比 ,得出该区古生界寒武、奥陶、志留、石炭和二叠系等地层中的黑色碳质页岩、硅质页岩、硅质条带和结核以及磷矿层和磷结核等沉积是古特提斯海中上升流作用形成的。上升流水体中富营养盐和SiO2 ,在古生代低纬度的扬子地块东南缘生物大量繁殖 ,引发缺氧事件 ,形成上述硅质和磷质沉积以及有机质丰富的烃源岩、石煤和磷矿层等 ,由于上升流水体富营养盐和SiO2 ,生物化石属种丰富 ,个体大 ,多营底栖或固着浅海底生活 ,硅质生物放射虫等丰富。区内烃源岩有机质与上升流的强度呈正相关关系 ,可见它们之间存在着成因联系。上古生界油气发现于苏北及南黄海 ,因而 ,这一区域是与上升流沉积有关的。

Jiangsu, Anhui, Jiangxi and Hubei Provinces, along the middle and lower reaches of the Yangtze River, are the southeastern margin of the Paleozoic passive continental margin of Yangtze block.Through analysis and correlation of 64 Paleozoic profiles across this area,it is considered that the upwelling in the Paleotethys caused deposition of dark carbonaceous shale, siliceous shale, siliceous bands and nodules, phosphorite layers and nodules of Cambrian, Ordovician, Silurian, Carboniferous and Permian in this passive continental margin area. Since upwelling water is rich in nutrient salt and SiO_2,high bioproductivity and anoxic events appeared in the southeastern margin of the low-latitude Paleozoic Yangtze block .The upwelling resulted in the deposition of organic-rich carbonaceous and phosphorite sediments such as source rocks, bone coal and phosphorite etc. There are rich fossil organisms in the sedimentary strata of the upwelling. Sizes of the fossils are big.The biocoenoses belong to benthonic and anchoring faunas in the shallow sea.Siliceous radiolarite boomed. The positive relationship between the TOC content and strength of the upwelling is evident. In the upper Paleozoic, the low (oil) and high maturities (condensate and wet gas) are located in the Subei area and east part of the South Yellow Sea.Consequently, Subei and South Yellow Sea basin is the important exploration area for the Paleozoic oil and gas of upwelling sedimentary strata.