河北兴隆团山子组旋回层序特征及地层格架

CYCLIC-SEQUENCES AND STRATIGRAPHIC FRAMWORK OF TUANSHANZI FORMATION OF MIDDLE PRO-TEROZOIC, XINLONG, HEBEI

中元古界团山子组由一套碳酸盐岩构成，发育若干类型的“环潮坪型碳酸盐米级旋回层序”，米级旋回层序的１∶４垂直叠加形式表明了旋回性地层记录的米兰柯维奇性质。根据米级旋回层序在长周期三级层序中的有规律叠加形式，在该组中识别出４个三级层序，它们构成一个二级超层序。依据三级层序的相序组构及时空变化特征，即可建立团山子组的地层格架。团山子组旋回层序特征表明，这套时限大致为１７００～１６５０Ｍａ的前寒武系，也存在类似于显生宙“温室效应”地史时期普遍发育的、与米兰柯维奇旋回有关的旋回性沉积记录。

There are many kinds of meter-scale cyclic-sequences belong to carbonate peritidal type developed in Tuanshanzi Formation of middle Proeterozoic, XingLong, Hebei. The regularly vertical stacking patterns of meter-scale cyclic-sequences marked by 1∶4 indicate the Milankovitch naturres of cyclic records in Tuanshanzi Formation. On the basis of lithofacies and facies-successions, four third-order sequences which constitute one second-order megasequence are discerned in the strata of Tuanshanzi Formation according to the regularly vertical patterns in Long-term third-order sequence. Based on the architecture of facies-succession as well as the changing natures in time and space of third-order sequences stratigraphical framwork of Tuanshanzi Formation can be constructed. The cyclic records of Tuanshanzi Formation (the time-span is from 1700 Ma to 1650 Ma ) of middle Proterozoic show that there are similar cyclic sedimentary records developed in Precambrian strata similar to those developed in 'green-house period' of Phanerozoic.