摘要:
结合四川盆地早寒武世龙王庙期区域沉积背景,本文对川中磨溪地区下寒武统龙王庙组的岩石类型、沉积构造、测井响应等沉积相标志进行了详细研究,探讨了磨溪地区龙王庙组的沉积微相特征及分布规律。研究表明早寒武世龙王庙期磨溪地区主要位于局限台地内,包括澙湖、颗粒滩和云坪三个亚环境,沉积产物以晶粒云岩及颗粒云岩为主。纵向上,龙王庙组由两个向上变浅的沉积旋回构成,旋回底部以澙湖沉积为主,中上部以颗粒滩沉积为主,顶部以云坪沉积为主。其中,颗粒滩亚相根据不同的岩性组合、沉积构造、颗粒岩累计厚度、单滩体颗粒岩厚度等可划分为滩主体(滩核)、滩翼以及滩间洼地三个微相。平面上,龙王庙组上下两段的沉积相展布具有明显的继承性,较龙王庙组下段而言,上段沉积时滩体的沉积范围、规模均有所扩大,同时颗粒滩具有向东迁移的趋势。磨溪地区龙王庙组沉积微相的展布主要受沉积期微古地貌以及相对海平面变化的影响,本文最后建立了磨溪地区龙王庙组颗粒滩沉积演化模式。
Abstract:
Combined with the depositional background of Early Cambrian Longwangmiao Formation in Sichuan Basin, the lithology, sedimentary structures, logging response, microfacies and sedimentary evolution of Longwangmiao Formation in Moxi area were analyzed. It is indicated that in Longwangmiao period, the Moxi area was located in the restricted platform, and the Longwangmiao Formation was composed of dolarenites and crystalline dolomites deposited in the restricted lagoon and grain shoal. Vertically, Longwangmiao Formation was composed of two sets of up-shallowing deposition, from restricted lagoon to the grain shoals. Grain shoal can be subdivided into shoal core, shoal margin and inter-shoal low according to the lithology, sedimentary structures, cumulative thickness of grain dolomite and the grain dolomite thickness of the single shoal. Horizontally, the sedimentary distribution of the Upper Longwangmiao Formation is similar to that of the Lower Longwangmiao Formation, but the shoal scale had been larger with the eastward migration trends. The microfacies distribution is controlled by the palaeogeography characteristic and relative sea-level. The sedimentary evolution model of Longwangmiao Formation in Moxi area has been established.
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