里奥穆尼盆地重力滑脱构造发育特征及演化规律

笔者论述了西非被动大陆边缘里奥穆尼盆地重力滑脱构造的发育特征及演化规律。里奥穆尼盆地晚白垩世至今的被动大陆边缘构造旋回主要发育重力滑脱构造,该盆地重力滑脱构造又可分为大陆架至上陆坡顶部的重力滑脱伸展构造、上陆坡中下部的重力滑脱底辟构造、中下陆坡-深海平原转换区的重力滑脱冲断构造;其中该盆地以重力滑脱伸展构造和重力滑脱冲断构造为主,重力滑脱底辟构造仅零星发育。一期完整的重力滑脱构造演化模式为从早到晚由陆向海逐渐发育的前展式发育模式,即最早发育高部位的重力滑脱伸展构造,其次发育中部的重力滑脱底辟构造,最后发育低部位的重力滑脱冲断构造。里奥穆尼盆地总共发育两期重力滑脱构造,分别是早白垩世阿尔布期(Albian)-晚白垩世发育的第1期(早期)重力滑脱构造,主要发育重力滑脱伸展构造和重力滑脱冲断构造;古近纪发育的第2期(晚期)重力滑脱构造,但此期仅发育活动较弱的重力滑脱伸展构造;这2期重力滑脱构造之间也呈现出从早到晚由陆向海发育的前展式结构,即晚期的重力滑脱伸展构造叠置在早期重力滑脱冲断构造之上。

Gravitational Decollement Structural Development Characteristics and Its Evolutionary History of Rio Muni Basin

The gravitational decollement structural development characteristics and its evolutional rules of Rio Muni Basin of the West African passive continental margin were described.From Late Cretaceous to present days,the gravitational decollement structures were mainly developed in passive continental-margin structural cycle,the gravitational decollement structures could be divided into the gravitational decollement extensional structures on upper continental slope,the gravitational decollement diapir structures on the middle and the gravitational decollement thrust structures on lower continental slope-deep sea plain.A complete tectonic evolution pattern of the gravitational decollement structures was a forward developmental pattern where the gravitional structures were developed from land to sea from early to late period.That was to say,the gravitational decollement extensional structures were first developed,then the gravitational decollement diapir structures were developed,finally the lower gravitational decollement thrust structures were developed.The Rio Muni Basin totally develops two-stage gravitational decollement structures: the first phase(early) gravitational decollement structure is developed from the Early Cretaceous Albian to Oligocene;the second phase(late) gravitational decollement structure is developed from Miocene up to now.Both gravitational decollement structures present a forward developmental structure is developed from land to sea from early to late period.That is,later gravitational decollement structures are developed on the seaward side of the early gravitational decollement structures.