宜昌莲沱震旦系陡山沱组含磷钙质风暴岩沉积特征

SEDIMENTARY CHARACTERISTICS OF PHOSPHORUS-BEARING CALC-STORM ROCKS OF DOUSHANTUO FORMATION OF SINIAN SYSTEM IN LIANTUO,YICHANG

宜昌莲沱地区上震旦统发育在扬子准地台中部鄂中碳酸岩台地两侧的浅陆棚区。陡山沱中期是风暴事件的多发区和活动中心。风暴作用强烈,风暴流沉积物发育并保存较好。属含磷钙质风暴岩。磷质聚集在风暴层系下部的块状粒序段A中。特别是粒序段底部滞留砾屑层含多量的磷块岩砾屑及胶磷矿砂屑,含量丰富可形成泥云基砂砾屑磷块岩。它是因风暴浪冲击台地边缘聚磷浅滩产生的携带大量沉积物的风暴流向海搬运至邻近的浅陆棚区,在重力分选作用下堆积而成。

The Upper Sinian Series in Liantuo area, Yichang develops in shallow continental shelf on the western side of carbonatite platform of central Hubei within the central part of Yangzi paraplatform. The mid-Doushantuo age is frequent area of storm events and active center. The storm actions are intense and the sediments of storm current develops and pre serves better, belonging to the phosphorus-bearing calc-storm rocks. The phosphorous subs-tance accumulates in massive graded member A of the lower storm layer system. Par-ticularly pebble-debris. layer obstructed at the bottom of the graded member contains much pebble debris of phosphorites and collophane arenites, the content of which is abundant and forms pebble-debris phosphorites filled with clay and dolomite. It is a storm current car-rying a great number of sediments by storm wave rushing upon the phosphorus-accumula-ted shallow beach on the platform margin: toward the sea the storm current migrates and accumulates into the adjacent shallow continental shelf area under the action of gravity sorting.