河南鲁山寒武系第二统辛集组风暴沉积及其相关的遗迹化石*
Storm deposits and relevant trace fossils from the Cambrian Series 2 Xinji Formation in Lushan area, Henan Province

河南鲁山寒武系第二统辛集组为一套风暴作用影响下的含磷和海绿石的碎屑岩沉积,主要由中厚层石英砂岩及极薄层泥岩与砂岩互层组成。遗迹化石发育在交错层理砂岩以及极薄层泥岩与薄层砂岩互层的层面上。Skolithos sp. 属于风暴衰减期的Skolithos遗迹相机会种(r-选择)遗迹化石,它们以短小的垂直居住潜穴及低遗迹分异度和丰度为特征。Palaeophycus tubularis,P. striatus,Taenidum sp.,Gordia marina,Planolites montanus,P. beverleyensis等属于风暴间歇期的Cruziana遗迹相均衡种(K-选择)遗迹化石,以水平进食、觅食潜穴为主,遗迹分异度和丰度中等。早寒武世风暴衰减期,频繁的风暴事件不利于研究区机会种遗迹化石的保存,同时风暴间歇期持续时间短、风暴停息期不发育,造成均衡类生物殖居窗口期短暂,亦不利于对沉积底质的连续殖居。这种特殊的风暴沉积以及早寒武世造迹生物较差的掘穴能力,导致研究区遗迹化石种类及数量远不及寒武纪以后的风暴沉积。
The Cambrian Series 2 Xinji Formation,a suit of siliciclastic stratum with phosphorus and glauconite deposits influenced by storm processes in Lushan area,Henan Province,mainly consists of medium- to thick-bedded quartzose sandstones and alternations of very thin-bedded mudstones and sandstones. Abundant trace fossils were preserved within cross-bedded sandstones and bedding planes between very thin-bedded mudstones and sandstones in the lower part of the formation. Skolithos sp. belongs to opportunistic trace fossil (r-selected) of Skolithos ichnofacies formed at weakening stage of the storm, dominated by short vertical dwelling burrows and low ichnodiversity and ichnoabundance. Palaeophycus tubularis,P. striatus,Taenidum sp.,Gordia marina,Planolites montanus and P.beverleyensis belong to equilibrium trace fossils(K-selected)of Cruziana ichnofacies formed during interludes between storms,which are dominated by the horizontal feeding and grazing burrows with medium ichnodiversity and ichnoabundance. The low ichnodiversity reflects dominance of the storm events with short duration of interludes which prevented the continuous colonization of substrates. The particular storm process and relatively poor burrowing ability of trace makers during the Early Cambrian may have led to the lower ichnodiversity and inchoabundance in storm deposits in study area in comparison to that during the time after Cambrian