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Chemostratigraphy of Cumberland Group (Pennsylvanian) strata influenced by salt tectonics, Joggins Fossil Cliffs UNESCO World Heritage Site, eastern Canada
Journal of Sedimentary Research ( IF 2 ) Pub Date : 2021-09-30 , DOI: 10.2110/jsr.2020.152
Fadel Bahr 1 , Dave Keighley 1
Affiliation  

The Pennsylvanian stratigraphy of the western Cumberland Basin has been influenced by salt tectonics, specifically the formation of the Minudie Anticline, a salt wall. South of the Minudie Anticline, along the shoreline of the Joggins Fossil Cliffs UNESCO World Heritage Site, the post–Boss Point Formation succession comprises an ∼ 3 km succession of strata assigned to the Little River, Joggins, Springhill Mines, and Ragged Reef formations. North of the Minudie anticline, the Grande Anse Formation lies in angular unconformity on the Boss Point and basal Little River formations. Biostratigraphic studies have not been able to discern whether the Grande Anse Formation is equivalent to all, or just one, of the Joggins to Ragged Reef units south of the salt wall (the Minudie Anticline).To further investigate the relationship of the Grande Anse Formation with the units along the Joggins shoreline, forty sandstone samples from the post–Boss Point Fm strata were selected for a chemostratigraphic study, using inductively coupled plasma mass spectrometry (ICP-MS) to determine major-element compositions. Transformed ICP-MS data, subjected to a Kruskal-Wallis test and post-hoc tests, show that there is no significant difference between Grande Anse and Ragged Reef formations in the mean values of almost all analyzed elements. In contrast, there are significant differences when comparing these two units and the older Little River, Joggins, and Springhill Mines formations in the case of elements usually encountered in detrital mineral phases (Si, Al, Ti, Na, and Fe). Sandstones of the Grande Anse and Ragged Reef formations show greater compositional maturity than the Little River, Joggins, and Springhill Mines formations. This trend is explained by a gradual overall change in paleoclimate from semiarid conditions during deposition of the Little River Formation to humid conditions during deposition of the Grande Anse and Ragged Reef formations, causing greater chemical weathering of the sediment. These findings indicate that > 2 km of sediment (Little River, Joggins, and Springhill Mines formations) accumulated south of the salt wall during the major episode of salt diapirism, followed by erosion of any topographic high associated with the salt wall, and accumulation of a further > 500 m of sediment (the laterally equivalent Ragged Reef and Grand Anse formations), all within a timespan of only ∼ 2 Myr.

中文翻译:

Cumberland Group (Pennsylvanian) 地层化学地层受盐构造影响,Joggins Fossil Cliffs 联合国教科文组织世界遗产,加拿大东部

坎伯兰盆地西部的宾夕法尼亚地层受到盐构造的影响,特别是米努迪背斜的形成,这是一个盐墙。Minudie 背斜以南,沿着联合国教科文组织世界遗产地乔金斯化石悬崖的海岸线,后 Boss Point 地层层序包括约 3 公里的连续地层,分配给 Little River、Joggins、Springhill Mines 和 Ragged Reef 地层。在 Minudie 背斜以北,Grande Anse 组位于 Boss Point 和基础 Little River 地层上的角度不整合面。生物地层学研究无法辨别 Grande Anse 地层是否等同于盐墙以南(米努迪背斜)的 Joggins 至参差不齐的珊瑚礁单元中的全部或一个。为了进一步研究 Grande Anse 地层与 Joggins 海岸线单位之间的关系,选择了来自 post-Boss Point Fm 地层的 40 份砂岩样品进行化学地层学研究,使用电感耦合等离子体质谱 (ICP-MS) 来确定主要-元素组成。经过 Kruskal-Wallis 检验和事后检验的转换后的 ICP-MS 数据表明,在几乎所有分析元素的平均值中,大湾和参差不齐的珊瑚礁地层之间没有显着差异。相比之下,就通常在碎屑矿物相(Si、Al、Ti、Na 和 Fe)中遇到的元素而言,将这两个单元与较旧的 Little River、Joggins 和 Springhill Mines 地层进行比较时,存在显着差异。Grande Anse 和 Ragged Reef 地层的砂岩显示出比 Little River、Joggins 和 Springhill Mines 地层更高的成分成熟度。这种趋势是由于古气候从 Little River 地层沉积期间的半干旱条件到 Grande Anse 和 Ragged Reef 地层沉积期间的潮湿条件逐渐整体变化,导致沉积物发生更大的化学风化作用。这些发现表明,在盐底辟作用的主要事件期间,盐壁以南堆积了 > 2 km 的沉积物(Little River、Joggins 和 Springhill Mines 地层),随后与盐壁相关的任何地形高点被侵蚀,以及进一步 > 500 m 的沉积物(横向等效的 Ragged Reef 和 Grand Anse 地层),所有这些都在仅 ~ 2 Myr 的时间跨度内。
更新日期:2021-09-24
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