摘要
泥盆纪时期龙门山构造带北段位于上扬子古陆的边缘,继承了陆棚斜坡断陷,沉积环境受斜坡区北川、南坝大断裂控制,在平面上由西向东分为海槽区、台缘浅滩区、开阔台地区和局限台地区。志留纪末,加里东运动使整个扬子地台上升为陆,为泥盆纪沉积提供了大量的陆源物质;早泥盆世,地壳下降、海侵开始,在青川—南坝断裂和马角坝—雁门坝断裂之间的甘溪、平驿铺和六合地区一带为浅海碳酸盐岩--滨岸碎屑岩沉积环境;中泥盆世,海侵更大、海域更广,天井山古隆起全被海水淹没并达汉南古陆边缘的朝天驿龙洞背附近;同时,川黔古陆地貌差异变小,物源供应减少,主要为一套以碎屑岩和碳酸盐岩为主的混合沉积;晚泥盆世,随海侵的进一步扩大,海域终止于天井山古隆起的边缘,区内基本无物源的供给,主要为一套以碳酸盐岩为主的沉积。龙门山地区泥盆纪沉积环境演化经历了3个主要沉积旋回:平驿铺旋回、甘溪—观雾山旋回和沙窝子—茅坝旋回。总的格局为海侵延续时间较长且速度较缓慢,而海退延续时间较短、速度较快且幅度较大。
The northern Longmenshan tectonic belt located at the egde of Upper Yangtze ancient land in Devonian,inherited the continental shelf slope fault.The depositional environment is controlled by Beichuan and Nanba faults in slope area,and divided into ocean trough,platform edge shoal,open platform and restricted platform areas from west to east at plane.At the end of Silurian,Caledonian movement uplifted the whole Yangtze platform to be ancient land,which supplied massive terrestrial materials to Devonian deposition.In Early Devonian,the crust declined and transgression started.The depositional environment in Ganxi,Pingyipu and Liuhe between the Qingchuan—Nanba fault and Majiaoba—Yanmenba fault is of neritic carbonate rocks and shoreland clastic rocks.In Middle Devonian,the transgression is more intensive with space of more extensive.Tianjingshan ancient uplift is completely covered by sea water and reached to Chaotianyilongdongbei in the Hannan ancient land,while the geomorphic difference between Sichuan and Guizhou ancient lands became smaller with reduced provenance supply,the sediments are mixed mainly by clastic and carbonate rocks.In Late Devonian,the maritime space terminated in the margin of Tianjingshan ancient uplift with the further expansion of transgression.There was only carbonate deposition with no source supply in this area.The evolution of depositional environment of Longmenshan in Devonian mainly experienced the Pingyipu,Ganxi—Guanwushan and Shawozi-Maoba sedimentary cycles.The general pattern is long-time and slow-velocity transgression,and short-time,high-velocity and large-range regression.
出处
《世界地质》
CAS
CSCD
2010年第4期561-568,共8页
World Geology
关键词
龙门山
泥盆系
岩相古地理
沉积环境
Longmenshan
Devonian
lithofacies paleography
depositional environment
