Abstract

Three floristic assemblages from the Upper Cretaceous volcanogenic deposits of the Bolshaya Ayanka River basin (Okhotsk-Chukotka volcanogenic belt (OChVB), Northeastern Russia) are described for the first time. The flora includes about 60 species of fossil plants. Conifers and angiosperms dominate; ferns are less diverse; horsetails, liverworts, ginkgoaleans, and cycads occur as single specimens. The Ayanka flora is similar to the Santonian–Campanian floras of Northeastern Russia and Northern Alaska (with Barykov, Late Bystraya, Ust-Emuneret, and, to a lesser extent, with the Ola and Early Kogosukruk floras), which allows to conclude the most probable Santonian–Campanian age of the studied flora. Floristic assemblages of the Ayanka flora reflect both slope vegetation dominated by conifers and vegetation of lowlands—river or lake banks—dominated by angiosperms. These assemblages demonstrate the penetration of plant communities dominated by advanced angiosperms from the coastal lowlands of the Anadyr–Koryak subregion to the territory of the volcanic highlands, where ferns and conifers are often found in the Late Cretaceous, and the relict plants of the Early and beginning of the Late Cretaceous are still preserved.

中文翻译：

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俄罗斯东北部鄂霍次克-楚科奇火山带上白垩统阿扬卡植物群的地层背景和组成

摘要

首次描述了来自 Bolshaya Ayanka 河流域（鄂霍次克-楚科奇火山带 (OChVB)，俄罗斯东北部）的上白垩统火山成因沉积物的三个植物区系组合。植物群包括大约 60 种化石植物。针叶树和被子植物占主导地位；蕨类植物种类较少；马尾、地钱、银杏和苏铁作为单一标本出现。Ayanka 植物群与俄罗斯东北部和阿拉斯加北部的 Santonian-Campanian 植物群（与 Barykov、Late Bystraya、Ust-Emuneret 以及在较小程度上与 Ola 和早期 Kogosukruk 植物群）相似，可以得出最所研究植物群的可能的桑托尼亚-坎帕尼亚时代。Ayanka 植物群的植物区系既反映了以针叶树为主的斜坡植被，也反映了以被子植物为主的低地植被（河岸或湖岸）。这些组合表明以先进被子植物为主的植物群落从阿纳德尔-科里亚克次区域的沿海低地渗透到火山高地的领土，那里经常发现晚白垩世的蕨类植物和针叶树，以及早和早的孑遗植物。晚白垩世初仍保存。