Factors controlling the organic matter accumulation across the Pliensbachian-Toarcian transition in the Qiangtang Basin, Tibetan Plateau
Factors controlling the organic matter accumulation across the Pliensbachian-Toarcian transition in the Qiangtang Basin, Tibetan Plateau
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青藏高原羌塘盆地普林斯巴阶-托阿尔阶过渡期有机质富集控制因素
DOI：
10.1016/j.marpetgeo.2021.105304
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发表时间：
2021-11
影响因子：
4.2
通讯作者：
Li Na
中科院分区：
文献类型：
--
作者：
Yi Fan;Yi Haisheng;Xia Guoqing;Wu Chihua;Li Gaojie;Cai Zhanhu;Li Na
碧龙错地区下侏罗统油页岩是青藏高原南羌塘盆地最重要的烃源岩。这些页岩沉积的发生与全球变暖的Pliensbachian-Toarcian过渡期密切相关;然而，这些页岩中有机质的积累机制仍然缺乏约束。在这项研究中，多代理地球化学研究进行了跨越Pliensbachian/Toarcian边界的Bilong剖面的有机质丰富的页岩，以评估有机质来源，碎屑流入，古盐度，古氧化还原条件，和古生产力在这些页岩的沉积。干酪根中正构烷烃的分布模式以及干酪根的H/C和O/C比值表明，有机质主要来源于海洋浮游生物/藻类。碎屑代用指标（K/Al、Si/Al、Ti/Al、Zr/Al和Zr/Rb）表明，该剖面沿着海平面相对稳定，大陆风化强度也相对稳定。古盐度指标表明，富有机质页岩沉积在海水盐度条件下，淡水输入很少。氧化还原指标（MoEF，UEF，ReEF，DOPT和Corg/Ptot）的协变模式表明，富含有机质的页岩沉积在亚氧条件下，而MoEF-UEF和Mo-TOC图表明弱水文限制沉积环境。生产力代理（Ptot，CuEF，ZnEF和CdEF），以及CdEF/MoE-CoEF* MnEF图显示低到中等初级生产力，表明有机质积累是由保护驱动，而不是由生产力。碧龙错地区大洋脱氧作用的发展可能是由于羌塘中央隆起与班公湖-怒江洋之间陆架的大洋环流减弱和温跃层增强的结果。Pliensbachian-Toarcian过渡期的气候变化导致了Bilong错地区有机质聚集的开始，而与良好的保存条件相关的水文限制的沉积环境可能是羌塘盆地南部下侏罗统油页岩大量沉积的主要原因。
The Lower Jurassic oil shales in the Bilong Co area are the most important hydrocarbon source rocks in the southern Qiangtang Basin, Tibetan Plateau. The onset of the deposition of these shales was closely related to the global warming during the Pliensbachian-Toarcian transition; however, the mechanism of organic matter accumulation in these shales remains poorly constrained. In this study, a multiproxy geochemical study was performed on the organic-rich shales spanning the Pliensbachian/Toarcian boundary in the Bilong Co section in order to assess the organic matter sources, detrital influx, paleosalinity, paleoredox conditions, and paleoproductivity during the deposition of these shales. The distribution patterns of then-alkanes, as well as the H/C and O/C ratios of the kerogen, suggest that the organic matter primarily originated from marine plankton/algae. The detrital proxies (K/Al, Si/Al, Ti/Al, Zr/Al, and Zr/Rb) indicate relatively stationary sea level and stable continental weathering intensity along the section. The paleosalinity proxies indicate that the organic-rich shales were deposited under marine salinity conditions with little freshwater input. The covariation patterns of the redox proxies (MoEF, UEF, ReEF, DOPT, and Corg/Ptot) suggest that the organic-rich shales were deposited under suboxic conditions, while the MoEF-UEFand Mo-TOC plots suggest a weakly hydrographically restricted depositional setting. The productivity proxies (Ptot, CuEF, ZnEF, and CdEF), as well as CdEF/MoE-CoEF*MnEFplot indicate low-to-moderate primary productivity, indicating that the organic matter accumulation was driven by preservation rather than by productivity. The development of the ocean deoxygenation in the Bilong Co area was probably the result of sluggish oceanic circulation and an enhanced thermocline on the shelf between the Qiangtang central uplift and the Bangong-Nujiang Ocean. The climatic changes during the Pliensbachian-Toarcian transition led to the onset of organic matter accumulation in the Bilong Co area, while the hydrographically restricted depositional setting associated with good preservation conditions may have been the primary reason for the massive deposition of the Lower Jurassic oil shales in the southern Qiangtang Basin.
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影响因子：
3.9
作者：
W. Ruebsam;M. Reolid;N. Sabatino;D. Masetti;L. Schwark
通讯作者：
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影响因子：
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作者：
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通讯作者：
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作者：
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通讯作者：
J. Moldowan;W. K. Seifert;E. J. Gallegos