Geochemical characteristics and depositional paleoenvironment of source rocks from the Lower Cretaceous Chijinbao Formation in Jiuxi Basin, China
Geochemical characteristics and depositional paleoenvironment of source rocks from the Lower Cretaceous Chijinbao Formation in Jiuxi Basin, China
复制标题
酒西盆地下白垩统赤金堡组烃源岩地球化学特征及沉积古环境
DOI：
10.1016/j.petrol.2021.109968
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发表时间：
2021-12
影响因子：
--
通讯作者：
Liwen Long
中科院分区：
文献类型：
--
作者：
Bo Ma;Liming Ji;Peihong Jin;Mingzhen Zhang;Bochao Yuan;Liwen Long
The Lower Cretaceous Chijinbao Formation is one of the primary source rocks in the Jiuxi Basin in Northwest China. However, it is poorly studied due to the lack of a complete stratigraphic sequence exposed by drilling. In this research, an integrated analysis of palynofacies, organic geochemistry, and element geochemistry was systematically conducted on samples with longitudinal continuity collected from the Chijinbao Formation in the Hanxia Section of the Jiuxi Basin to determine the distribution of source rocks and the source and type of organic matter and to reconstruct the depositional paleoenvironment of the Chijinbao Formation. The lower part of the sequence, which is governed by poor source rocks with Type III organic matter, is characterized by palynofacies A (woody tissue–charcoal assemblage) grown in a proximal alluvial fan–shallow lacustrine environment. The excellent source rocks with mostly Type II1organic matter are considerable in the middle part of the sequence, which is marked by palynofacies B (amorphous organic matter assemblage), and occur in a distal semi-deep lacustrine–deep lacustrine environment. The upper part of the sequence is largely composed of poor and fair source rocks, represented by palynofacies C (amorphous organic matter–woody tissue assemblage), and a small amount of sporadically distributed good and excellent source rocks (approximately 1/3), which may be deposited in a proximal fan delta and a local semi-deep lacustrine–deep lacustrine environment. A semiarid–semi-humid climate and a freshwater–brackish water environment prevailed during the deposition of the Chijinbao Formation. The lower part of the sequence is characterized by the highest terrestrial detritus influx, strong weathering, humid paleoclimate, oxic water column conditions, and the lowest paleoproductivity. The middle part of the sequence has the lowest terrestrial detritus influx, relatively weak weathering, relatively arid paleoclimate, predominantly anoxic water environment, and the highest paleoproductivity. The climate became humid again during the deposition of the upper part, which is typified by an intermediate terrestrial detritus influx, strong weathering, fluctuations of oxic–anoxic bottom-water conditions, and moderate paleoproductivity. The correlation analysis of element proxies suggests that the increase in salinity during the deposition of the middle part is associated with an arid climate. Amorphous organic matter, which is derived mostly from aquatic organisms and degraded terrestrial higher plants, is the major hydrocarbon generation component in the source rocks of the Chijinbao Formation. It increases in abundance with an improvement in water reducibility and productivity, favoring the formation and preservation of excellent source rocks.
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酒溪盆地寒霞-红柳峡地区早白垩世孢粉学与古气候
影响因子：
1.9
作者：
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期刊：
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影响因子：
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