河南西峡盆地上白垩统河流及湖泊沉积中的遗迹组构

河南西峡盆地上白垩统马家村组沉积厚度巨大，达1 960 m，由辫状河沉积、曲流河沉积和湖泊沉积组成。在河流与湖泊沉积中，发育丰富的遗迹化石，共6种类型，分别为Skolithos linearis、Cylindricumichnosp、Palaeophycus tubularis“J”形潜穴、垂直分枝潜穴和垂直螺旋潜穴。从形态分析，大多数为居住迹，按照遗迹化石产出岩层的岩性、扰动特征和残留遗迹等总体特征，将所发现的遗迹化石层划分为两类遗迹组构，即软底组构和僵底组构。前者主要发育在纹层状极细砂岩和粉砂岩中，潜穴密度大，属种单一，包括Skolithos组构和Palaeophycus组构；后者主要发育在厚层泥岩中，潜穴密度较大，类型稍多，包括由Cylindricum ichnosp、垂直分枝潜穴J形潜穴和垂直螺旋潜穴所组成的遗迹组构。与报道过的其他地区陆相遗迹化石的对比表明，随着时间的推移，河流沉积中的组构特征在白垩纪有明显变化，而浅湖沉积中的遗迹组构表明造迹生物的扰动能力显著加强。

Ichnofabric characteristics of fluvial and lacustrine sediments of the Upper Cretaceous in Xixia Basin, Henan Province

The Majiacun Formation of Upper Cretaceous，with a thickness of 1 960 m，crops out in the Xixia Basin，southwestern Henan ProvinceFrom the base of the formation upwards，the succession is composed of braided river，meandering river and lacustrine sedimentsA lot of trace fossilswere foundin the fluvial lacustrine sediments，including Skolithos linearis,Cylindricum ichnosp，Palaeophycus tubuaris,Jshaped burrows,vertical branchedburrows and vertically helical burrows Most of the trace fossils，in terms of theirshapes，are supposed to be domichnia,and can be classified into assemblagesof Scoyenia or Arenicolites ichnofacies Based on the lithology of thehost rocks，bioturbation and the total relic fabric，the two ichnofabric typesnamed as soft ground ichnofabric and stiff ground ichnofabric can be distinguishedThe former type of ichnofabric consisted of Skolithos linearis and Palaeophycus tubularis which occurred in very fine grained sandstones and siltstones，displaying higher density and less diversity of trace fossils,while the latter type of ichnofabric dominated by Cylindricum ichnosp,Jshaped burrows,vertical branched burrows and vertically helical burrows,occurred in siltstones and thick bed mudstones，exhibiting less density and more diverse individuals Comparedto the reported continental ichnofabrics，the fluvial ichnofabric varied apparently in the Cretaceous，and shallow lacustrine ichnofabric showed that the trace maker’sability to bioturbate the substrates increased obviouslywith time passing