论文部分内容阅读
古元古代全球性冰期(～2.3Ga)可能是地质历史时期发育最早的雪球事件.华北地区广泛出露古元古代轻微变质沉积岩,但缺乏古元古代冰期事件的沉积学证据.研究了山西五台地区古元古代滹沱群(2.5～2.2Ga)稳定碳同位素组成,结果显示δ13C值在垂向地层序列中的变化有明显的规律性:豆村亚群大石岭组碳同位素高正值(δ13Ccarb值3.2‰～1.0‰);东冶亚群纹山组-大关洞组中部碳同位素值的降低(δ13Ccarb值2.0‰～-1.2‰),伴随着叠层石从繁盛到衰落的过程;至大关洞组上部及其与槐荫村组界线附近碳同位素发生显著负漂移(δ13Ccarb值1.4‰～-3.3‰),该段地层叠层石不发育;在其之上的北大兴组-天蓬垴组碳同位素比值逐渐恢复到零值附近(δ13Ccarb-1.2‰～1.4‰),叠层石迅速繁盛.在东冶亚群建安村组-大关洞组中部出现的碳同位素负漂移可能是古元古代全球性冰期事件在我国华北地区的响应,反映古元古代全球古气候发生了重要的变化.
The ancient glacial period (~2.3Ga) in the Paleoproterozoic may be the earliest snowball event in the geologic history.Exploration of Paleoproterozoic metamorphic sedimentary rocks in North China, but lack of depositional evidence of Paleoproterozoic glacial events, The stable carbon isotopic compositions of the ancient Proterozoic Hudutou (2.5 ~ 2.2Ga) in the Wutai area show that there is a clear regularity of the δ13C value in the vertical stratigraphic sequence: the high positive value of carbon isotope The δ13Ccarb values ranged from 3.2 ‰ to 1.0 ‰). The decrease of carbon isotope values (δ13Ccarb value 2.0 ‰ ~ -1.2 ‰) in the middle of the Dongshang sub-group Zhushan-Daguandong Formation accompanied with the process of the stratum from prosperity to decline. (Δ13Ccarb = 1.4 ‰ ~ -3.3 ‰) in the upper part of the Dabuan Tunnel Group and its boundary with Huaiyin-Mukai Formation. The strata of this strata are not well developed. On the top of the North Daxing Formation - The δ13Ccarb-1.2 ‰ ~ 1.4 ‰ (δ13Ccarb-1.2 ‰ ~ 1.4 ‰) carbon isotope ratio of canopies gradually recovered to zero, and the stratums rapidly thrived. The carbon isotope shifts that may occur in the middle part of Jianancun-Daguandong Formation in Dongye Subgroup may be negative It is the ancient ice age in ancient China in North China Response, Gu Yuan reflect the global paleoclimate classical important changes have taken place.