鲁南新元古界石旺庄组风暴岩特征及其意义

Features and Their Siginificance for the Tempestite of Neoproterozoic Shiwangzhuang Formation in South Shandong Province

鲁南地区新元古界石旺庄组为一套以白云岩为主的地层,其中发育多层竹叶状砾屑灰岩,同时还发育丘状层理、粒序层理等沉积构造以及波状、不规则状、含V字形、U字形槽模等底面构造所代表的冲刷面,表现为较典型的风暴岩特征。研究表明,石旺庄组竹叶状砾屑灰岩形成于缓坡型台地的浅缓坡环境之中,为揭示鲁南新元古界岩相古地理特征提供了重要依据。竹叶状砾屑灰岩所代表的风暴岩在前寒武纪碳酸盐岩地层、尤其是潮下缓坡相碳酸盐岩沉积中较为普遍,对该类型沉积及其共生的沉积构造进行系统描述将有助于前寒武纪古环境的恢复。

The Neoproterozoic Shiwangzhuang Formation in the southern part of Shandong Province is marked by a set of dolomitic deposits,in which several beds of edgewise calcirudites and scouring surfaces represented by underside structures such as the wave-shaped,the irregular-shaped,the V-shaped and the U-shaped trough molds are developed.All of these features indicate that the edgewise calcirudites may represent the typical tempestite,which is formed in the shallow ramp affected frequently by strong storm.Therefore,the tempestite in the Neoproterozoic Shiwangzhuang Formation provides a useful actual evidence to study the paleogeographical setting of the Neoproterozoic in the southern part of Shandong Province.Since the tempestite represented by edgewise calcirudites is widespread in carbonates of the Precambrian especially for those subtidal deposits of shallow ramp,the detail description for this type of deposits and their genetically relative sedimentary structures is helpful to reconstruct. the sedimentary environment of the Precambrian.