Ultra-shallow-marine anoxia in an Early Triassic shallow-marine clastic ramp (Spitsbergen) and the suppression of benthic radiation
Ultra-shallow-marine anoxia in an Early Triassic shallow-marine clastic ramp (Spitsbergen) and the suppression of benthic radiation
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DOI：
10.1017/s0016756815000588
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发表时间：
2015-10
影响因子：
2.3
通讯作者：
P. Wignall;D. Bond;Yadong Sun;S. Grasby;B. Beauchamp;M. Joachimski;D. Blomeier
中科院分区：
文献类型：
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作者：
P. Wignall;D. Bond;Yadong Sun;S. Grasby;B. Beauchamp;M. Joachimski;D. Blomeier
摘要斯匹次卑尔根群岛的下三叠世海相地层堆积在中高纬度斜坡上，其中高能前滨和滨面相通过近海进入可能为硬辉石成因的席状砂岩。更远的相包括粉砂岩、页岩和碳酸盐石灰岩。碳同位素化学地层学的比较，使改进的年代测定的北方部分，并显示了显着的间隙在上Spathian。两个主要的加深事件，在最早的格里斯巴赫和晚期史密斯时间，被分开的浅向上的趋势，最终在Dienerian和Spathian子阶段。氧化还原记录，揭示了生物扰动，古生态，黄铁矿framboid含量和微量金属浓度的变化，显示缺氧阶段交替间隔更好的通风。只有Dienerian-early Smithian时间见证了持续的氧合，足以支持多样化的底栖生物群落。最强烈的缺氧，通常是缺氧的，条件最好在近海环境中发展，但有时euxinia也在近海环境中发展，甚至在hyperpycnite和风暴成因的砂岩床中也有记录：斯匹次卑尔根记录的一个非凡方面。富氧相不跟踪相对水深的变化。例如，从Griesbachian到下Dienerian的连续变浅，见证了几个由更好氧的生物扰动沉积物间隔分开的富氧相。这可能是由气候振荡，而不是流域内因素控制的真石漆。尽管在史密斯/斯帕蒂安边界区间广泛分布的缺氧相显然是一个全球性事件，但在斯匹次卑尔根发现的所有缺氧相是否在其他地方也能看到还有待观察。
Abstract Lower Triassic marine strata in Spitsbergen accumulated on a mid-to-high latitude ramp in which high-energy foreshore and shoreface facies passed offshore into sheet sandstones of probable hyperpycnite origin. More distal facies include siltstones, shales and dolomitic limestones. Carbon isotope chemostratigraphy comparison allows improved age dating of the Boreal sections and shows a significant hiatus in the upper Spathian. Two major deepening events, in earliest Griesbachian and late Smithian time, are separated by shallowing-upwards trends that culminated in the Dienerian and Spathian substages. The redox record, revealed by changes in bioturbation, palaeoecology, pyrite framboid content and trace metal concentrations, shows anoxic phases alternating with intervals of better ventilation. Only Dienerian–early Smithian time witnessed persistent oxygenation that was sufficient to support a diverse benthic community. The most intensely anoxic, usually euxinic, conditions are best developed in offshore settings, but at times euxinia also developed in upper offshore settings where it is even recorded in hyperpycnite and storm-origin sandstone beds: an extraordinary facet of Spitsbergen's record. The euxinic phases do not track relative water depth changes. For example, the continuous shallowing upwards from the Griesbachian to lower Dienerian was witness to several euxinic phases separated by intervals of more oxic, bioturbated sediments. It is likely that the euxinia was controlled by climatic oscillations rather than intra-basinal factors. It remains to be seen if all the anoxic phases found in Spitsbergen are seen elsewhere, although the wide spread of anoxic facies in the Smithian/Spathian boundary interval is clearly a global event.