贵州台江下-中寒武统凯里组遗迹化石群落与环境关系的探讨

RELATIONSHIP BETWEEN ICHNOCOENOSIS AND SEDIMENTARY ENVIRONMENTIN THE LOWER-MIDDLE CAMBRIAN KAILI FORMATION OFTAIJIANG,GUIZHOU, CHINA

通过贵州台江凯里组中丰富的、分异度较高的、以原地埋藏为特征的遗迹化石的研究,探讨凯里组遗迹化石群落的沉积环境和埋藏环境。凯里组遗迹化石群落以节肢动物和软体动物的停息迹、爬行迹和游泳迹占优势,浅层内生爬行觅食潜穴和系统觅食潜穴占有一定的地位,也见有浅的居住滤食性潜穴,属Seilacher的Cruziana遗迹相,为正常浪基面和风暴浪基面之间的浅海软质基底陆棚低能环境,那里盐度正常、光照充足、含氧量充分、水体平静、沉积速率较快。在此环境中,浮游、游泳以及底栖爬行和固着生物类型大量地生长、繁殖和活动,表生遗迹和浅层内生遗迹十分丰富。生物死亡后的腐烂和分解,使得食泥生物大量繁盛。随着沉积物的覆盖和被埋藏生物遗体的分解、腐烂,沉积物内部还原能力逐渐增强,导致分解和腐烂过程终止。

Abundant trace fossils including Rusophycus, Cruziana , Did yrnaulichnus, Di plichnites , Dirnorphichnus, Beaconichnus, Monornorphichnus, Lophocteniurn, Planolites, Palaeophycus, Gordia, Cochlichnus, Oldharnia, Phycodes, Bi fungites, Arenicolites, Treptichnus and Rhizocorallum have been found in the Lower-Middle Cambrian Kaili Formation at Balang, Taijiang County, Guizhou Province, China. The Kaili Biota in the Kaili Formation is similar to that in the Burgess Shale （Zhao et al. , 1994, 1999, 2002）. There are different views on its edimentary environments （Yang, 1994; Zhang, 1996）. This paper deals with the sedimentary environments of the Kaili Formation, ichnocoenosis in it and taphonomy of the Kaili Biota. The Kaili ichnocoenosis belonging to Cruziana ichnofacies of Seilacher （1964, 1967） is composed of predominant resting, crawling, walking, swimming and feeding traces produced by arthropods （trilobite） and some dwelling burrows. Ichnological studies indicate that the Kaili Formation was deposited in openshelf environments between daily wave base and storm wave base with normal salinity and abundant light. Varied pelagic, swimming and sessile organisms lived in the calm and aerobic environments. Epirelic and shallow endirelic traces made by different trace makers in the Kaili Formation are abundant. After organisms died, the decay and decomposition of corpses resulted in richness of organic materials and flourish of depositfeeding organisms. Along with continual covers of deposits and decay and decomposition of corpses, reducing environments became dominant and the process of the decay and decomposition ceased.