济阳坳陷车镇凹陷古近系沙河街组遗迹化石Macaronichnus(通心粉管迹)及其沉积环境

济阳坳陷车镇凹陷古近系沙河街组发现的Macaronichnus segregatis(分离通心粉管迹)是一种直到微弯曲形状的层内进食潜穴，个体较小，不分枝，长一般7～8 mm，直径1～3 mm，与前人发现的化石在个体大小上存在着差异。它主要出现于四类环境：①三角洲平原河道间低地，②三角洲、扇三角洲前缘远端砂坝和浊积扇的中扇到外扇，③潮湿气候条件下的浅湖，④周期性干旱气候条件下的滨浅湖。不同沉积环境中产出的Msegregatis都分布于粉砂质泥岩中。通过分析各沉积环境的水动力条件和水体化学性质以及Msegregatis的形成过程，可得出以下结论：①Msegregatis出现的水动力条件中等，水体能量过高或过低，都不适宜其生成；②Msegregatis出现的水体化学性质介于贫氧与富氧之间；③Msegregatis是在沉积物沉积后还未固结时由食沉积物生物活动造成的，衬壁的出现反映了软基底性质。

Sedimentary environments of Macaronichnus of the Shahejie Formation of Paleogene of Chezhen Sag in Jiyang Depression

Macaronichnus segregatis in the Shahejie Formation of Paleogene in Chezhen Sag of Jiyang Depression is an intrastratal and irregularly meandering burrow structureIt is 7～8 mm in length and 1～3 mm in diameter，which is different in size from the same genus formerly discoveredThe ichnotaxon is commonly distinguished from several sedimentary environments：①places between channels of delta plain; ②delta，fan delta front bar and middle to outer fan of turbidite fan; ③shallow lake under humid climate；and ④shore to shallow lake sediments under periodically arid climateThey are generally found in silty mudstone deposited in different environmentsBased on the analyzed results of the hydrodynamic conditions,the chemical characters in different sedimentary environments and the forming process of Macaronichnus segregatis，some conclusions can be drawn as following: ① Msegregatis occurs in moderate water energy environments，and rather high or low water energy is not suitable for its existence；② The burrow maker of Msegregatis lives among the upper dysoxic zone；③ Msegregatis is produced by deposit feeder before the substrate becomes firm，implied by the presence of linings surrounding the trace fossils