Abstract

The article discusses the main disagreements between two published models (the authors’ model and the previously published model by V.V. Mitta et al.) of the structure and stratigraphic subdivision of the Bajocian–Bathonian reference section in the north of European Russia (near the Dreshchanka River mouth, Izhma River basin). Calculation of dip and strike makes it possible to verify mutually exclusive correlation schemes for key outcrops exposed near the Dreshchanka River mouth. It is shown that the correlation model for outcrops proposed by V.V. Mitta is inconsistent. According to this model, the actual thickness of the Bajocian part of the succession is understated. Some disagreements in ammonite stratigraphy are also discussed. Ammonites occurring in the lower Bathonian Ishmae Zone of the Timan–Pechora region belong to a single species, Arcticoceras ishmae, characterized by a wide range of intraspecific variability. The available data for the studied region does not allow any further division of the Ishmae Zone into either subzones or biohorizons. The classical succession, including four consecutive biohorizons in East Greenland, is based on the change of chronosubspecies/chronovariations of the species A. ishmae, which differ in the ratio of intraspecific morphs of the proposed variability. Currently, it is impossible to define these horizons in the Timan–Pechora region sections because representative sets of well-referenced samples are absent.

中文翻译：

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伊日马河流域（俄罗斯欧洲北部）参考剖面巴约阶-巴松阶的地质特征和亚科 Arctocephalitinae Meledina 菊石的演替

摘要

本文讨论了俄罗斯欧洲北部（靠近 Dreshchanka河口，伊日马河流域）。倾角和走向的计算使得可以验证 Dreshchanka 河口附近暴露的关键露头的互斥相关方案。结果表明，VV Mitta 提出的露头相关模型不一致。根据该模型，该序列的 Bajocian 部分的实际厚度被低估了。还讨论了菊石地层学中的一些分歧。出现在蒂曼-伯朝拉地区巴顿阶下部伊什梅带的菊石属于单一物种， Arcticoceras ishmae，其特征是种内变异范围很广。研究区域的可用数据不允许将 Ishmae 带进一步划分为子带或生物地层。经典的演替，包括东格陵兰的四个连续的生物地平线，是基于A. ishmae物种的时间亚种/时间变异的 变化，它们在提议的变异性的种内形态的比率上有所不同。目前，无法在 Timan-Pechora 区域部分定义这些层级，因为缺少参考良好的代表性样本集。