Tournaisian forested wetlands in the Horton Group of Atlantic Canada
Tournaisian forested wetlands in the Horton Group of Atlantic Canada
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加拿大大西洋霍顿群的图尔奈森林湿地
DOI：
10.1130/2006.2399(05
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
Camilla S.A. Melrose
中科院分区：
文献类型：
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作者：
M. Rygel;J. Calder;M. Gibling;M. Gingras;Camilla S.A. Melrose
加拿大大西洋沿岸的霍顿群（晚法门期到图尔奈期）提供了一个异常完整的早期密西西比湿地生物群记录。最著名的是来自“罗默峡谷”的四足动物化石，这个单位还包含许多有植被的地平线。霍顿群化石森林的埋藏学和分类学仍然是个谜，因为保存不好，奇怪的树桩铸造形态，以及未能认识到在直立植物周围形成的不寻常的沉积结构。霍顿组内的四个森林层位被保存为由碎屑沉积物与原位植物相互作用形成的隐蔽铸件和植被诱导的沉积结构。原气门是木本石松类Lepidodendropsis的浅裂基部，以砂岩填充的管型附着在密集的根团上。泥岩填充的空洞是部分被掩埋的植物腐烂后形成的，留下的空隙后来被泥泞的沉积物填充。一个划痕半圆形形成的地方，电流弯曲一个小植物，使它雕刻成同心槽到相邻的泥泞的基础。障碍物的痕迹发展的地方，洪水沃茨挖掘侵蚀冲刷到桑迪沉积物周围的少年Lepidodendropsis。这些神秘的石松类森林的密度比宾夕法尼亚州的森林要高得多。霍顿群地层中有大量的植被引起的沉积构造，很容易被误艾德是纯粹的水动力沉积物或软沉积物。104 M.C. Rygel等人
The Horton Group (late Famennian to Tournaisian) of Atlantic Canada provides an unusually complete record of Early Mississippian wetland biota. Best known for tetrapod fossils from “Romer’s Gap,” this unit also contains numerous horizons with standing vegetation. The taphonomy and taxonomy of Horton Group fossil forests have remained enigmatic because of poor preservation, curious stump cast morphology, and failure to recognize the unusual sedimentary structures formed around standing plants. Four forested horizons within the Horton Group are preserved as cryptic casts and vegetation-induced sedimentary structures formed by the interaction of detrital sediment with in situ plants. Protostigmaria, the lobed base of the arborescent lycopsid Lepidodendropsis, occur as sandstone-fi lled casts attached to dense root masses. Mudstone-fi lled hollows formed when a partially entombed plant decayed, leaving a void that was later infi lled by muddy sediment. A scratch semi-circle formed where a current bent a small plant, causing it to inscribe concentric grooves into the adjacent muddy substrate. Obstacle marks developed where fl ood waters excavated erosional scours into sandy sediment surrounding juvenile Lepidodendropsis. These cryptic lycopsid forests had considerably higher densities than their Pennsylvanian counterparts. Vegetation-induced sedimentary structures are abundant in Horton Group strata and could easily be misidentifi ed as purely hydrodynamic or soft-sediment *Present address: Department of Geosciences, 224 Bessey Hall, University of Nebraska, Lincoln, Nebraska 68588-0340; mrygel@unlnotes.unl.edu. 104 M.C. Rygel et al.