西准噶尔中古生代复理石相遗迹化石及其古环境意义

西准噶尔复理石相遗迹化石主要分布于上泥盆统-下石炭统塔尔巴哈台组以及石炭系的包古图组、太勒古拉组和哈拉阿拉特组中, 典型遗迹属包括Phycosiphon, Nereites, Megagrapton, Glockerichnus, Cochlichnus, Lophoctenium, Gordia, Chondrites, Zoophycos, Scolicia, Thalassinoides.这些遗迹化石构成具有典型深水Nereites遗迹相特征的Phycosiphon-Nereites遗迹化石组合和Megagrapton-Glockerichnus-Cochlichnus遗迹化石组合.包古图组和太勒古拉组属于海底扇中下扇扇缘-盆地平原环境; 哈拉阿拉特组和塔尔巴哈台组则属于海底扇中下扇扇叶环境.西准噶尔复理石相遗迹化石分布与鲍马序列的厚度密切相关, 在毫米-厘米级鲍马序列中, 遗迹化石属种单调且保存较差, 可见单一属的Phycosiphon或Nereites; 而在厘米-分米级鲍马序列中, 可见不同直径大小和形态上具有过渡的Phycosiphon和Nereites, 可能代表同种造迹生物不同个体发育阶段的生物遗迹.海底扇不同亚环境单个鲍马序列的厚度决定了底栖生物是否有足够的时间形成较为成熟的群落(包括一系列幼年和成年个体). 

Middle Paleozoic Flysch Trace Fossils from Western Junggar and Their Palaeoenvironmental Significance

The flysch trace fossils of western Junggar, Xinjiang, NW China are mainly distributed in the Upper Devonian-Lower Carboniferous Ta'erbahatai Formation and Baogutu, Tailegula and Hala'alate formations of the Carboniferous. Characteristic trace fossils include Phycosiphon, Nereites, Megagrapton, Glockerichnus, Cochlichnus, Lophoctenium, Gordia, Chondrites, Zoophycos, Scolicia, Thalassinoides, forming two characteristic trace fossil assemblages of the Nereites ichnofacies: the Phycosiphon-Nereites and Megagrapton-Glockerichnus-Cochlichnus ichnoassemblages. The Baogutu and Tailegula formations represent the medial-distal submarine fan fringe-basin plain environments, while the Hala'alate and Ta'erbahatai formations are chiefly medial-distal submarine fan lobe deposits. The distribution of flysch trace fossils in western Junggar is closely linked to the thickness of the Bouma sequences. In millimetre to centimetre Bouma sequences, there are only scarce and blur traces of Phycosiphon or Nereites, while in centimetre to decimetre Bouma sequences, Phycosiphon and Nereites of various diametres and transitional morphologies occur, which might be produced by conspecific trace makers in an ontogenetic series. The thickness of a single Bouma sequence in submarine fan related environments determines if there is enough time for a mature benthic fauna to develop (with a series of young and old individuals).