黄河中下游焦作区段现代边滩沉积中的生物遗迹

摘要

沉积物中的生物遗迹记录是生物与环境相互作用的结果,是沉积环境、气候及生态环境的良好指示标志.文中主要研究了黄河中下游焦作区段现代边滩沉积物中的生物遗迹及其造迹者的组成与分布特点,即:(1)近岸边滩:几乎无植被,以层面上的生物觅食迹为主,其造迹生物主要有鸟类、长泥甲虫(鞘翅目长泥甲科)和隐翅虫(鞘翅目隐翅虫科)等；(2)远岸边滩:有大量植物根出现,大多数生物遗迹是层内U形、Y形和W形潜穴以及层面上的F形、Y形爬行迹和觅食迹,其主要造迹生物为蝼蛄(直翅目蝼蛄科)、蟋蟀、狼蛛和蠕虫类等；(3)泛滥平原:出现大量植物根,以层内J形、漏斗形等的生物居住迹和进食迹为主,主要造迹生物为蝼蛄、蟋蟀、田鼠、蚁狮和狼蛛等.基于沉积物粒度分析、总有机碳测定、菌落平板计数法等手段分析得知,研究区现代生物遗迹的深度随沉积物中微生物群落数量的增加及植物根长度的增长而增加,而丰度和分异度随沉积物粒度的递减及总有机碳含量的增加而增大.该成果一方面能为研究区黄河边滩上生物成因的沉积构造提供新资料,另一方面也能为地史时期河流沉积环境的研究乃至古地理、古生态环境重建提供生物遗迹学方面的科学依据.%Biogenic traces records are the results of the interaction of organisms and environment and the good indicator of sedimentary environment, climate and the ecological environment. The composition and distribution characters of biogenic traces and their makers in modern point bar deposits of the Middle-Lower Reaches of Yellow River in Jiaozuo area, Henan Province, are as follows: (1 ) The main trace-makers on point bar near riverbed are birds and Coleptera. The main traces are the feeding traces of Co-leptera and birds on the bedding plane. (2) The main trace-makers on distal point bar and temporal channels are insects as mole crickets, crickets and worms. The main traces are the U-shaped, Y-shaped, W-shaped and vertical feeding burrows of mole crickets, crickets and worms in intrastratal bedding as well as F-shaped and Y-shaped feeding and crawling traces developed on bedding plane. (3 ) The main trace-makers on flood plain are ant lion, cricket, field mouse and spiders. The biogenic traces are characterized by the J-shaped and funnel shaped feeding and dwelling burrows. By means of grain size a-nalysis, admeasurements of total-organic-carbon, plant bacteria colony counting, the abundance and diversity of traces increase with decreasing grain size and increasing TOC in this study area. The depth of traces below the sediment surface is closely related to the food source and amount of bacteria in the sediments. This study is not only significant to identify the biogenic structures and can be applied to the study of fluvial sedimentary environment, ecology, palaeoichnology research, but also is available to the palae-oclimate, palaeoenviroment and palaeoecology reconstruction.