A reconstruction of the early Palaeocene palaeovegetation of Turtle Mountain, south-western Manitoba, Canada

The lower Goodlands Member of the Turtle Mountain Formation is exposed in a streambank outcrop on the western flank of Turtle Mountain, south-western Manitoba, Canada (49°0′2″N, 100°14′51″W). This outcrop was sampled for a 1.5 m section of microfossil-rich non-marine clay and coal-rich sediments deposited in a coastal plain environment during the early Palaeocene. These sediments were deposited 65.4–65 Ma and thus offer an opportunity to reconstruct terrestrial palaeoecology 0.6 to 1 Ma after the Cretaceous–Paleogene boundary (K–Pg) extinction event. We use quantitative palynology to reconstruct terrestrial plant ecology and explore ecological patterns of recovery and succession of these communities on a millennial time scale. Quantitative palynological analyses shows that at the time of deposition of the Goodlands Member the landscape on the coastal plain of the Western Interior Seaway – in what is now south-western Manitoba – was covered in a forested canopied swamp with tall standing swamp cypress and other conifers, Juglandaceae (walnut family), birch, alder, elms and other angiosperms, with an understory of ferns and ground cover of Sphagnum moss. Notably, palms were present but scarce, indicating a relatively warm climate. No successional pattern of diversity and community composition is evident in the samples; all samples showed high plant diversity (33–54 taxa/sample, H′ 2–3). Vegetation in Manitoba recovered within 0.6 to 1 Ma following the K–Pg extinction event or was predominantly influenced by local environmental patterns independent of time.

加拿大马尼托巴省西南部乌龟山（Turtle Mountain）西翼的河岸露头处，出露有乌龟山组（Turtle Mountain Formation）下古兰兹段（Goodlands Member），其地理坐标为49°0′2″N，100°14′51″W。该露头针对一套厚度1.5米、富含微古生物的非海相黏土与富煤沉积物开展了采样工作，这些沉积物形成于古新世早期的海岸平原环境，沉积年代为65.4–65 Ma，可为重建白垩纪-古近纪界线（Cretaceous–Paleogene boundary, K–Pg）灭绝事件后0.6至1 Ma的陆地古生态提供研究契机。本研究采用定量孢粉学（quantitative palynology）方法，重建该区域的陆地植物生态，并探索该群落在千年时间尺度上的恢复与演替生态模式。定量孢粉分析结果显示，在古兰兹段沉积时期，现今马尼托巴省西南部区域所处的西部内陆海（Western Interior Seaway）海岸平原地带，被覆盖有林冠的沼泽森林所占据，其中优势类群包括高大的落羽杉（swamp cypress）与其他针叶树、胡桃科（Juglandaceae，核桃科）植物、桦木、桤木、榆科植物及其他被子植物；林下伴生蕨类植物，地表覆盖有泥炭藓（Sphagnum moss）。值得注意的是，当时区域内存在但数量稀少的棕榈类植物，表明彼时气候相对温暖。本次采集的样品未显现出多样性与群落组成的演替模式，所有样品均展现出较高的植物多样性（单样含33–54个分类单元，香农指数H'为2–3）。综上，马尼托巴省的植被在K–Pg灭绝事件后的0.6至1 Ma内即完成恢复，或其群落组成主要受局地环境模式调控，与时间因素关联较弱。