Micropaleontological and geochemical analyses in samples from the Coniacian-Maastrichtian-aged Smoking Hills and Mason River formations in the Anderson Basin of the northern mainland coast of Arctic Canada provide a refined picture of the environmental conditions occurring in the incipient southern Arctic Ocean at the end of the Cretaceous. These units were deposited within a 22 myr time span in an outer shelf setting characterized by relatively stable tectonic conditions and low sedimentation rates. The Coniacian-middle Campanian Smoking Hills Formation was deposited during times of marine transgression and water column stratification. Surface waters were highly productive and dominated by dinoflagellates, red algae, green algae and likely diatoms and silicoflagellates. Bottom waters were predominantly anoxic-euxinic, but the presence of benthic foraminifera and variations of geochemical signatures in some intervals indicate episodic ventilation. The deposition of the Smoking Hills Formation is temporally consistent with the Oceanic Anoxic Event 3 (OAE3), but the duration of these anoxic conditions is much longer in the Anderson Basin. During the middle Campanian, relative sea level reached a highstand, fostering the expansion of planktic siliceous microorganisms, including diatoms, silicoflagellates and radiolarians. During the late Campanian to at least the Maastrichtian, sediments of the Mason River Formation were deposited during a regressive sedimentation phase characterized by high productivity fueled by river run-off and the proliferation of diatoms, red and green algae. Despite high productivity, bottom waters were oxygenated. This study highlights the importance of data integration to reconstruct the environmental conditions of the past as many, if not all, of the proxies utilized to this end are subjected to preservational and diagenetic bias.

中文翻译：

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南冰洋晚白垩世生态系统动态：微古生物学和地球化学视角


对加拿大北极大陆北部大陆海岸安德森盆地的 Coniacian-Maastrichtian 时代的 Smoking Hills 和 Mason River 地层的样本进行微古生物学和地球化学分析，提供了白垩纪末期南北冰洋初期环境条件的精炼图景。这些单元在 22 myr 的时间跨度内沉积在外大陆架环境中，其特点是构造条件相对稳定，沉积速率低。Coniacian-Middle Campanian Smoking Hills 组是在海洋海侵和水柱分层时期沉积的。地表水产量很高，以甲藻、红藻、绿藻以及可能的硅藻和硅藻藻为主。底层水域主要是缺氧-真生的，但底栖有孔虫的存在和某些间隔中地球化学特征的变化表明存在间歇性通风。Smoking Hills 组的沉积在时间上与海洋缺氧事件 3 （OAE3） 一致，但在安德森盆地，这些缺氧条件的持续时间要长得多。在坎帕尼亚中期，相对海平面达到高位，促进了浮游硅质微生物的扩张，包括硅藻、硅鞭毛虫和放射虫。在坎帕尼亚晚期至至少马斯特里赫时期，梅森河组的沉积物沉积在退行沉积阶段，其特征是河流径流和硅藻、红藻和绿藻的增殖推动了高生产力。尽管生产力很高，但底层水是含氧的。 这项研究强调了数据集成对于重建过去环境条件的重要性，因为用于此目的的许多（如果不是全部）代理都受到保存和成岩偏差的影响。