A conifer-dominated palynological assemblage from Pennsylvanian (late Moscovian) alluvial drylands in Atlantic Canada: implications for the vegetation of tropical lowlands during glacial phases
A conifer-dominated palynological assemblage from Pennsylvanian (late Moscovian) alluvial drylands in Atlantic Canada: implications for the vegetation of tropical lowlands during glacial phases
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DOI：
10.1144/0016-76492010-061
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发表时间：
2011-02
影响因子：
2.7
通讯作者：
G. Dolby;H. Falcon-Lang;M. Gibling
中科院分区：
文献类型：
--
作者：
G. Dolby;H. Falcon-Lang;M. Gibling
摘要：新的研究表明，在季节性干旱的冰川期，宾夕法尼亚州的煤炭森林通常被针叶树为主的植被所取代。在这里，我们描述了从堆叠序列的中宾夕法尼亚（晚莫斯科）悉尼矿区形成的新斯科舍省，加拿大，这给这个假设提供了一些支持的孢粉组合。一个关键的样品，从一个广泛的红层继承下面的海港煤主要是针叶树花粉（55%），连同丰富的代表cordaitaleans，其他coniferopsids，和罕见的pteridosperms，蕨类植物和lepidodendrids。它明显不同于其他13个样品从煤，其屋顶页岩-石灰岩和相关的通道机构，其中主要是lepidodendrids，marattialean树蕨，cordaitaleans和/或calamiteans。后者床代表沿海湿地，并归因于晚期海侵和高位体系域，而针叶树轴承样品代表旱地冲积平原，并可能归因于低位或最早的海侵体系域。另外三个样品从灰色页岩以下的序列边界（晚期高位）和红层继承和主要煤层（早期至中期海侵存款）之间包含过渡palynofloras与高比例的草本gleicheniaceous和sphenopteroid蕨类植物，草本石松，和sphenophylls穿插cordaitaleans和/或lepidodendrids。针叶树花粉的优势旱地组件内定义明确的序列，这已被链接到相对海平面的变化，促进冈瓦纳冰川作用，支持宾夕法尼亚州的热带生物群系的冰川-间冰期周期的节拍。
Abstract: New research suggests that Pennsylvanian Coal Forests were commonly replaced by conifer-dominated vegetation during seasonally dry glacial phases. Here we describe palynological assemblages from stacked sequences of the Middle Pennsylvanian (late Moscovian) Sydney Mines Formation of Nova Scotia, Canada, which lends some support to this hypothesis. One critical sample from a widespread redbed succession below the Harbour Coal is dominated by conifer pollen (55%), together with abundant representatives of cordaitaleans, other coniferopsids, and rare pteridosperms, ferns and lepidodendrids. It differs markedly from 13 other samples obtained from coals, their roof shale–limestone and associated channel bodies, which are dominated by lepidodendrids, marattialean tree-ferns, cordaitaleans and/or calamiteans. The latter beds represent coastal wetlands, and are attributed to late transgressive and highstand systems tracts, whereas the conifer-bearing sample represents a dryland alluvial plain and may be attributed to lowstand or earliest transgressive systems tracts. Three additional samples from grey shale below a sequence boundary (late highstand) and between a redbed succession and major coal seam (early to mid-transgressive deposits) contain transitional palynofloras with a high proportion of herbaceous gleicheniaceous and sphenopteroid ferns, herbaceous lycopsids, and sphenophylls interspersed with cordaitaleans and/or lepidodendrids. The dominance of conifer pollen within the dryland components of well-defined sequences, which have been linked to relative sea-level change promoted by Gondwanan glaciation, supports the view that Pennsylvanian tropical biomes responded to the beat of glacial–interglacial cycles.