古代深海底质氧控的遗迹化石群落

Oxygen-dependent Ichnocoenose in Paleo-pelagic Substrates

通过中国 9个深海沉积区近 2 0条研究剖面的沉积地质学和古遗迹学的研究 ,获得了判别深海底质遗迹化石群落与含氧量关系的几点认识 :1深海贫氧的底质中因相对含氧量的差异 ,其代表性的遗迹化石组合也不尽相同。以Megagrapton,Paleodictyon和 Protopaleodictyon为代表的 A组合 ,以 Scalarituba和 Phycosiphon为代表的 B组合 ,和以 Chondrites和 Zoophyeos为代表的 C组合 ,所指示贫氧底质中的溶解氧含量 ,是随组合的不同而依次降低 ;2遗迹化石潜穴的粗细通常与底质含氧量呈正相关 ,即潜穴直径随含氧量降低而变细 ;3遗迹化石的分异度随底质含氧量降低而变低 ;4应用个别遗迹化石属判识贫氧环境要慎重 ,如 Chondrites或者 Zoophycos,不能不加分析地视为贫氧环境的遗迹化石标志 ,应结合多种因素综合分析后 ,才能得出更符合客观实际的认识。

On the basis of sedimentological and palichnological investigations on the nearly 20 profiles of 9 paleo-pelagic depositional areas in China, some conclusions on the identification of the relationship between ichnocoenose in paleo-pelagic substrates and the oxygen content have been drawn as follows: ①The difference in the relative oxygen content of the pelagic oxygen-depleted substrate produces a different representative ichnofossil association, i.e. the dissolved oxygen content of the oxygen-depleted substrate indicated by Associations A, B and C, which are mainly composed of Megagrapton, Paleodictyon and Protopaleodictyon , of Scalarituba and Phycosiphon , and of Chondrites and Zoophycos , respectively, decreases gradually with different associations; ②The size of ichnofossil burrows usually has a normal relationship with the oxygen content of substrates, namely the diameter of burrows becomes smaller with decreasing of the oxygen content; ③The differentiation of ichnofossils decreases with decreasing of the oxygen content of substrates; ④It should be prudent to apply some individual ichnofossils in identifying the oxygen-depleted environment, for instance, Chondrites and Zoophycos can not be always regarded as an ichnofossil indicator to an oxygen-depleted environment, it is necessary to investigate multiple factors before a conclusion that more accords with the true fact can be drawn.