Evidence for a redox stratified Cryogenian marine basin, Datangpo Formation, South China
Evidence for a redox stratified Cryogenian marine basin, Datangpo Formation, South China
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DOI：
10.1016/j.epsl.2012.03.018
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发表时间：
2012-05
影响因子：
5.3
通讯作者：
Chao Li;G. Love;T. Lyons;C. Scott;Lianjun Feng;Jing Huang;Huajin Chang;Qirui Zhang;X. Chu-
中科院分区：
文献类型：
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作者：
Chao Li;G. Love;T. Lyons;C. Scott;Lianjun Feng;Jing Huang;Huajin Chang;Qirui Zhang;X. Chu-
在这里，在努力探索Cryogenian海水化学，我们目前的铁，碳，钼和硫的化学地层结果的两个露头部分的CA。南化盆地新元古代两大冰期（Sturtian冰期和Marinoan冰期）之间的大塘坡组沉积于663- 654 Ma。古地理重建表明，间冰期南华盆地是一个新生的年轻洋盆，约1000年以来因裂谷作用而打开。820-630Ma。与开阔洋的海水交换受到限制;这种间冰期条件可能是整个区域和世界的共同特征，与全球海平面低水位期间广泛的裂谷边缘有关。浅水杨家坪和深水民乐段生成的地球化学剖面表现出大致一致的地层变化，一般指向缺氧（主要是缺氧）深水沉积的下部黑色页岩，但增加氧化沉积在浅水中的上部粉砂岩在这两个部分。在大塘坡组记录的水化学波动可以解释由分层氧化还原模型，其中水柱化学强烈控制铁的可用性和其他营养通量，低溶解海洋硫酸盐浓度，海平面变化，并通过初级生产提供的海洋有机碳的不同输入。对新近发表的大塘坡组硫同位素资料的综合分析表明，南华盆地底部碳酸盐岩和页岩中的34 S极富集黄铁矿（高达69‰）主要形成于盆地深部沃茨。最可能的解释是富含34 S的深海硫酸盐池，部分是在Sturtian冰川作用期间通过细菌硫酸盐还原结合严重抑制的河流硫酸盐输入和海平面急剧下降期间边缘盆地的限制而产生的。这项研究强调了全球和局部控制在确定新元古代海洋盆地的化学条件的重要性。
Here, in an effort to explore Cryogenian seawater chemistry, we present chemostratigraphic results for iron, carbon, molybdenum, and sulfur for two outcrop sections for the ca. 663–654Ma Datangpo Formation deposited between the two major Neoproterozoic glacial episodes (Sturtian and Marinoan) in the Nanhua Basin, South China. Paleogeographic reconstruction suggests that the interglacial Nanhua Basin was an emerging young ocean basin, which opened by rifting from ca. 820–630Ma. Seawater exchange with the open ocean was restricted; such interglacial conditions may have been a common feature throughout the region and the world in association with widespread rifted margins during global sea-level lowstands. Geochemical profiles generated for the shallow water Yangjiaping and deeper water Minle sections demonstrate broadly consistent stratigraphic variations and generally point to anoxic (mostly euxinic) deep water deposition for the lower black shales but increasing oxygenation for the upper siltstones deposited in shallower water at both sections. Fluctuations in water chemistry recorded in the Datangpo Formation can be explained by a stratified redox model in which water column chemistry was strongly controlled by Fe availability and other nutrient fluxes, low dissolved marine sulfate concentrations, sea level variation, and varying inputs of marine organic carbon delivered via primary production. A compilation of new and published sulfur isotope data for the Datangpo Formation indicates that the extremely34S-enriched pyrite (up to 69‰) in the basal carbonates and shales was formed mainly in the deep waters of the Nanhua Basin. The most likely explanation is a34S-enriched deep marine sulfate pool generated, in part, during the Sturtian glaciation by bacterial sulfate reduction in combination with severely suppressed riverine sulfate inputs and restriction of the marginal basin during a dramatic drop in sea level. This study highlights the importance of both global and local controls in determining the chemical conditions in Neoproterozoic marine basins.