贺兰山中段震旦系盖帽白云岩的沉积特征、区域对比及意义

2011年,作者在贺兰山中段腰坝配件厂地区进行1∶5万区域地质调查时发现了震旦系盖帽白云岩,进而研究了其沉积特征、碳氧同位素组成和时代,并与该区紫花沟兔儿坑组白云岩、华南和华北地台南缘相应地层进行对比.结果表明,盖帽白云岩为含陆源细碎屑白云岩,与兔儿坑组白云岩相近;其δ13C值为-4.7‰～0.79‰,且自下而上呈下降趋势;其时代与华南震旦系下、中部相当,与华北地台南缘震旦系罗圈组的沉积特征和古地理环境相近;与全球Gaskiers冰期有相关性.这对华北地台的古构造、古地理、古气候及动物演化“源头”的研究有重要意义.

Sedimentary characteristics,regional comparison and implication of the Sinian cap dolomites in the middle Helan Mountain

Sinian cap dolomites have been found in Peijianchang area, Helanshan Mountain, when performing the 1.50 000 geological survey in 2011. The sedimentary characteristics, C-O isotopes, compositions and age of the dolomites were studied, and correlated with the contemporaneous dolomites from Zihuagou area and correspondent strata from the south margins of, South China and North China Platforms. The dolomites in the studied area belong to terrigeous clastric dolomites, which resemble that of Tuerken formation, Zihuagou area. The δ13C values range from -4.7‰ to -0.79‰, and decrease with the ascending order. The carbonates share the similar sedimentary characteristics and palaegeographic environ-ments with the lower-upper Sinian in South China and the Sinian Luoquan Formation in the south margins of North China platform. Thus, this study could be contributed to the study on the palaeotectonics, palae-ogeography and palaeoclimatology of North China platform, and the evolution of invertebrates.