Late Palaeozoic red beds elucidate fluvial architectures preserving large woody debris in the seasonal tropics of central Pangaea
Late Palaeozoic red beds elucidate fluvial architectures preserving large woody debris in the seasonal tropics of central Pangaea
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DOI：
10.1111/sed.12692
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发表时间：
2020-01
期刊：
影响因子：
3.5
通讯作者：
Steffen Trümper;Steffen Trümper;Birgit Gaitzsch;J. Schneider;J. Schneider;Bodo-Carlo Ehling;R. Kleeberg;R. Roessler;Ronny Rößler
中科院分区：
文献类型：
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作者：
Steffen Trümper;Steffen Trümper;Birgit Gaitzsch;J. Schneider;J. Schneider;Bodo-Carlo Ehling;R. Kleeberg;R. Roessler;Ronny Rößler
含有解剖保存的大型木质碎屑的河流红层为宾夕法尼亚-二叠纪过渡时期季节性干燥的生物群提供了新的线索，并阐明了河流沉积系统和植被的共存。因此，石化的大型木质碎屑堆积的发生、分布和保存被认为是理解树生植被在塑造河流环境中的作用的关键。这项研究报告了来自宾夕法尼亚(上Gzhelian)Siebigerode组(德国中部Kyffhäuser)的相当大的硅化主干和相应的河流结构。综合运用地质填图、岩相分析、沉积岩石学、木材解剖和显微结构分析等多学科方法，对化石木的成因、埋藏学和沉积环境进行了研究。这些结果反映了萨勒盆地西北部边缘砂层到砾石层辫状河流对基底的缓慢抬升的逐渐埋藏。相结构是同沉积构造、反复古珊瑚复壮、高频河道撕裂、季节性干燥气候和木质碎屑-沉积物相互作用的复杂相互作用的结果。冲积的涌入和河岸的侵蚀从邻近的半河岸斜坡栖息地吸收了树干，栖息着高达40米的珊瑚和针叶树。宽阔辫子中的高流量有利于大块木质碎屑的畅通运输。树干的埋葬和最初的保存是在树枝上扎根，用附着的根固定，然后埋葬的结果。沉积后的两相硅化作用受热液赤铁矿矿化的影响，决定了一种选择性的木材保存模式，称为尖岩。大型木质碎屑沉积构造(LWDISS)是生物作用于陆地沉积作用形成的一类沉积构造。
Fluvial red beds containing anatomically preserved large woody debris shed new light on seasonally dry biomes of the Pennsylvanian–Permian transition and elucidate the concurrence of river depositional systems and vegetation. As a result, the occurrence, distribution and preservation of petrified large woody debris accumulations are considered crucial to understanding the role of arborescent vegetation in shaping fluvial environments. This study reports sizeable silicified trunks and corresponding fluvial architectures from the uppermost Pennsylvanian (upper Gzhelian) Siebigerode Formation (Kyffhäuser, central Germany). The origin, taphonomy and depositional environment of the fossil woods are elucidated by using a multidisciplinary approach including geological mapping, lithofacies analysis, sediment petrography, wood anatomical studies and microstructure analyses. Results reflect the gradual burial of a gentle basement elevation by sand‐bed to gravel‐bed braided rivers at the north‐western margin of the perimontane Saale Basin. Facies architectures resulted from a complex interplay of syndepositional tectonics, repeated palaeorelief rejuvenation, high‐frequency channel avulsion, seasonally dry climate and woody debris–sediment interactions. The alluvial influx and cut‐bank erosion recruited trunks from adjacent semi‐riparian slope habitats vegetated by up to 40 m tall cordaitaleans and conifers. High discharge in wide braids facilitated uncongested transport of large woody debris. Trunk entombment and initial preservation resulted from grounding on barforms, anchoring by attached roots and subsequent burial. The post‐depositional two‐phase silicification was influenced by hydrothermal hematite mineralization and determined a selective wood preservation pattern known as ‘pointstone’. Large woody debris‐induced sedimentary structures (‘LWDISS’) are introduced as a class of sediment structures formed by the biogenic impact on terrestrial deposition.