The petrology and depositional environments of the Middle Cambrian Wirrealpa and Aroona Creek limestones (South Australia)
The petrology and depositional environments of the Middle Cambrian Wirrealpa and Aroona Creek limestones (South Australia)
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DOI：
10.1306/212f73fb-2b24-11d7-8648000102c1865d
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发表时间：
1978-03
影响因子：
2
通讯作者：
B. C. Youngs
中科院分区：
文献类型：
--
作者：
B. C. Youngs
摘要通过对中寒武世早期Wirrealpa和Aroona Creek石灰岩中约500个碳酸盐岩样品的醋酸盐岩皮进行岩相学研究，确定了9种主要岩石类型。碳酸盐颗粒包括圆整的鲕粒、核粒、内碎屑、泥质和化石碎片。纹理范围从颗粒岩到泥岩。瘤状和半瘤状层，规则地与薄的、波状的钙质粉砂互层，在各处都很常见。在22个实测剖面中，识别出2个大相，由8个相组成。这两个巨相弧的沉积环境解释--（1）靠近浅克拉通内台地的向洋边缘的一个卵形滩区域，其特征是在较小湍流区域之间存在移动的卵形浅滩，以及（2）一个浅的海洋泻湖，卵形浅滩后面的特征主要是较小湍流的沉积条件、钙质粉砂和叠层石。通过对某露头区的详细相分析，明确地记录了一个海侵-海退旋回。外推到其他四个露头地区，使整个Arrowie盆地的尝试性古地理重建假设。这表明海侵来自盆地的北方地区，并可能向盆地的北部地区退缩。
ABSTRACT A petrographic study of acetate peels made from approximately 500 carbonate rock samples from the early Middle Cambrian Wirrealpa and Aroona Creek Limestones led to the identification of nine major rock types. Carbonate grains include well-rounded ooids, oncolites, intraclasts, peloids and fossil fragments. Textures range from grainstones to mudstones. Nodular and semi-nodular layers, regularly interbedded with thin, wavy, calcareous silts, are common throughout. Two megafacies, composed of eight facies, were identified in most of the 22 measured sections. Interpreted depositional environments for these two megafacies arc--(1) an ooid bank area close to the oceanward margin of a shallow intracratonic platform, characterized by mobile ooid shoals intertonguing between areas of lesser t rbulence, and (2) a shallow, marine lagoon, behind the ooid shoals characterized mainly by less turbulent depositional conditions, calcareous silts and stromatolites. The detailed analysis of facies in one outcrop area provides a clear record of a marine transgression-regression cycle. Extrapolation to four other outcrop areas enables tentative paleogeographic reconstructions for the whole Arrowie Basin to be hypothesized. These suggest that the transgression came from and probably retreated to the northern areas of the basin.