塔里木盆地奥陶纪—志留纪陆生植物微体化石记录——兼论早期孢型化石古地理和生物地层研究现状及问题

MICROFOSSILS OF LAND PLANTS FROM THE ORDOVICIAN AND SILURIAN OF THE TARIM BASIN,WITH DISCUSSIONS ON THE PALEOGEOGRAPHICAL AND BIOSTRATIGRAPHICAL SIGNIFICANCE OF EARLY SPOROMORPHS

本文梳理并总结了塔里木盆地奥陶纪—志留纪陆生植物微体化石组合面貌及含化石层位。化石证据来自盆地覆盖区草1井(深度5309.31 m和5471.98 m)和满南1井(深度3206.68 m和3207.28 m)的上奥陶统岩心(对应地表的铁热克阿瓦提组)、托甫2井(第6—7回次)的志留系兰多维列统岩心(对应地表的柯坪塔格组),以及盆地西北缘上奥陶统—志留系的西克尔层、柯坪塔格组、塔塔埃尔塔格组和克兹尔塔格组地层剖面。塔里木盆地的早期陆生植物微体化石中,隐孢子分布最为广泛,在上述露头地层和钻井岩心中均有记录;三缝孢目前发现于柯坪塔格组上段、塔塔埃尔塔格组和克兹尔塔格组下段;管状体仅来自西克尔层;类表皮则出现在西克尔层和塔塔埃尔塔格组。基于孢型化石记录开展古生物地理研究时,需考虑基础数据偏差,也需要识别局部环境和气候的影响。奥陶纪—志留纪孢型化石全球生物带有待厘定,该时期中国各板块上的孢型化石分布零散、丰度较低,缺少标志性属种,未建立系统的生物地层序列,应优先开展该时期区域性的生物地层序列划分工作。

The microfossil assemblages of the Ordovician and Silurian land plants and the fossil-bearing horizons in the Tarim Basin are reviewed here.Fossil records of early land plants have been documented from the Upper Ordovician of two boreholes,i.e.,Cao-1(depths of 5309.31 m and 5471.98 m)and Mannan-1(depths of 3206.68 m and 3207.28 m)(corresponding to the Terekawat Formation),the Llandovery of TP2 borehole,the outcrops of the Upper Ordovician‒Silurian Xikeer Bed,Kalpintag,Tataaiertag and Kiziltag formations.Our study shows that cryptospores are the most widely distributed microfossils of early land plants in Tarim Basin,as they have been recorded in all of the above-mentioned strata and borehole cores.Trilete spores are found in the upper part of the Kalpintag Formation,the Tataaiertag Formation and the lower part of Kiziltag Formation.The fossil tubes are only recovered from the Xikeer Bed.The cuticle-like sheets occur in the Xikeer Bed and the Tataaiertag Formation.It is necessary to consider the basic data deviation and identify the impacts of the local environment and climate in the palaeobiogeography of sporomorphs.The biozones of global Ordovician-Silurian sporomorphs need to be further revised.The sporomorphs of China during this period are relatively rare and lack stratigraphically diagnostic taxa,and thus no biostratigraphic sequences have been systematically established.For the biostratigraphy of the Ordovician-Silurian sporomorphs,priority should be given to the establishment of a regional framework.