洛阳龙门地区中寒武统张夏组下部遗迹组构及其沉积环境

洛阳龙门地区中寒武统张夏组为一套富含生物扰动的薄层微晶灰岩和厚层鲕粒灰岩沉积，根据沉积学和遗迹学特征，从中识别出6个遗迹组构，从下到上依次是:潮下低能碳酸盐岩台地中的Planolites montanus遗迹组构，潮下浅水较高能碳酸盐岩台地中的Palaeophycus tubularis-Thalassinoides horizontalis遗迹组构，高、低能交替的滨岸浅滩或开阔台地滩间坪或滩前沉积中的Skolithos linearis-Planolites montanus遗迹组构，深水低能开阔台地沉积中的模糊生物扰动遗迹组构，高能鲕粒浅滩中的Macaronichnus segregatis遗迹组构和潮下低能局限台地环境中的Palaeophycus heberti遗迹组构.龙门地区张夏组由无鲕粒滩的碳酸盐岩台地逐渐向发育厚层鲕粒滩的碳酸盐岩台地演化，沉积环境从滨岸浅滩逐渐演变为无鲕粒滩的开阔台地，并随着海退由深水、开阔台地逐渐变浅形成鲕粒滩、局限台地. 

Ichnofabrics and Their Sedimentary Environments from the Lower Part of the Middle Cambrian Zhangxia Formation,Longmen Area,Luoyang City

The Zhangxia Formation in the Longmen area, Luoyang City, was a set of deposited thin-bedded microcrystalline limestone and thick-bedded oolitic limestone, with abundant bioturbation. Based on sedimentology and ichnology characteristics, six ichnofabrics were determined, namely from the bottom up, Planolites montanus ichnofabric in low energy, subtidal carbonate platform; Palaeophycus tubularis-Thalassinoides horizontalis ichnofabric in shallow, medium energy, subtidal carbonate platform; Skolithos linearis-Planolites montanus ichnofabric in onshore oolitic shoals, inter flat and fore shoals of oolitic platform with alternation of high and low energy; blurry bioturbation ichnofabric in deeper water, lower energy of open platform; Macaronichnus segregatis ichnofabric in oolitic shoals with high energy and Palaeophycus heberti ichnofabric in subtidal restricted platform with low energy. Zhangxia Formation in Longmen area developed from carbonate platform without oolitic shoals to with oolitic shoals. The sedimentary environment evolved from onshore oolitic shoals to open platform without oolitic shoals, and finally ended up with platform oolitic shoals and restricted platform with the regression.