CAJ | 학술논문

“雪球地球”假说为全球新元古代冰碛岩研究注入了新的活力.各国地质学家根据新元古代冰碛岩全球各大洲发育的特点,并依据同位素年龄、δ13C/δ18O 和 Sr 的比值和化学蚀变指数(CIA)为全球的新元古界划分出4个冰期,但国际上的4个冰期的限定,是各大洲不同剖面冰期的集合.新元古代冰期事件周期变化视为早期生物复苏和早期动物分异的起点.由于国际埃迪卡拉系底界(GSSP)年龄,即成冰系顶界年龄确定后,使成冰系底界年龄成为当前研究的重点.中国新疆塔里木板块库鲁克塔格地区新元古代冰碛岩是目前世界各大陆中发育有4套连续的新元古代冰碛岩和多期火成岩事件的唯一剖面,它的进一步深入研究,可以备考全球冰期的同步性,以期建立全球新元古代冰碛岩标准剖面.本文报道了来自塔里木西南缘南华系波龙组的碎屑锆石年龄,有助于我们对塔里木板块西南缘南华系时代的限定.
“설구지구”가설위전구신원고대빙적암연구주입료신적활력.각국지질학가근거신원고대빙적암전구각대주발육적특점,병의거동위소년령、δ13C/δ18O 화 Sr 적비치화화학식변지수(CIA)위전구적신원고계화분출4개빙기,단국제상적4개빙기적한정,시각대주불동부면빙기적집합.신원고대빙기사건주기변화시위조기생물복소화조기동물분이적기점.유우국제애적잡랍계저계(GSSP)년령,즉성빙계정계년령학정후,사성빙계저계년령성위당전연구적중점.중국신강탑리목판괴고로극탑격지구신원고대빙적암시목전세계각대륙중발육유4투련속적신원고대빙적암화다기화성암사건적유일부면,타적진일보심입연구,가이비고전구빙기적동보성,이기건립전구신원고대빙적암표준부면.본문보도료래자탑리목서남연남화계파룡조적쇄설고석년령,유조우아문대탑리목판괴서남연남화계시대적한정.
The hypothesis of the “Snow Earth” pours new vitality into the study of the global Neoproterozoic glaciations. According to the development of glaciations in different continents, isotopic dating, ratios ofδ13C/δ18O and CIA, four glaciations have been recognized in the whole globe along different sections in different continents. The change of the circle of Neoproterozoic glaciations is regarded as the start of the early biota or division. Because the top GSSP of the Crytersian has been defined, the bottom of GSSA has become a problem in the study of glaciations. Now, the Kuruk Tag section in Tarim Plate of Xinjiang is the only section with four Neoproterozoic glaciations and different volcanic rocks. The further study of the Nanhuan glaciations in Tarim is useful work for the stratigraphic correlation with the global Neoproterozoic glaciations. The authors put forward for the first time the upper limit line of the deposition of the Bolong Formation based on the distributional pattern of debris zircon ages from the Bolong Formation, Nanhuan System. The main distributional pattern of debris zircon ages comprises 2.5 Ga, 2.2 Ga and 1.8 Ga, with the youngest age being 756 Ma, suggesting that the depositional age is younger than 756 Ma. According to the distributional pattern of debris zircon ages of the Bolong Formation, they must have had different rock sources in relation to Tarim Plate.