巴布亚湾两期前陆盆地叠置结构及其形成演化

Superimposed Structure and Evolution of Two-Stage Foreland Basin in Gulf of Papua

巴布亚湾受澳大利亚板块与太平洋板块高速斜向汇聚的控制,经历了复杂的中、新生代构造演化.前人对巴布亚湾盆地结构构造特征的研究多是局部的、分散的,关于盆地的形成时间和动力学机制仍存在争议.利用覆盖全盆的钻井约束的高精度2D、3D地震资料,精细地刻画了盆地的结构和构造特征,揭示了巴布亚湾发育潘多拉和奥雷两期叠置的前陆盆地.潘多拉前陆盆地是形成于渐新世不整合面之上的晚渐新世-中中新世微型前陆盆地,走向为NNE.奥雷前陆盆地是发育在复杂的裂谷边缘之上的早中新世-现今的周缘前陆盆地,沿着弧形的巴布亚半岛延伸480 km;盆地走向在148°E发生转变,由西部的NW向转为东部的近EW向.潘多拉微前陆盆地被奥雷前陆盆地向南逐渐超覆的沉积地层覆盖,两个前陆盆地走向相互垂直,垂向上形成叠置结构.阐明了巴布亚湾新生代经历三期挤压事件及两期叠置的前陆盆地的形成演化,解决了盆地结构及区域构造演化认识的不足,理清了复杂陆缘环境从伸展到挤压多期构造事件的时序及动力学机制,为澳大利亚板块北缘的板块构造重建提供了盆内证据.

The Gulf of Papua has undergone complex evolution due to the oblique and rapid converging between the Australian and Pacific plates in boundary zone.However,since previous studies on the basin structural characteristics of the Gulf of Papua are mostly local and dispersed,the formation time and dynamics mechanism of the basin are still controversial.In this paper,the structural characteristics of the basin are described by using the high-precision 2D and 3D seismic data with drilling constraints covering the whole basin.It is revealed that there are two superposed foreland basins of Pandora and Aure foreland basins in the Gulf of Papua.The Pandora foreland basin is a Late Oligocene-Middle Miocene micro-foreland basin formed on the unconformity of the Oligocene trending NNE.The Aure foreland basin is an Early Miocene-Present peripheral foreland basin developed on the complex rift margin,extending 480 km along the curved Papua peninsula.The basin trend changes from NW in the west to near EW in the east at longitude 148°E.The Pandora micro-foreland basin is covered by sedimentary strata of the Aure foreland basin that gradually onlaps southward.The two foreland basins strike perpendicular to each other and form a superimposed structure vertically.This study elucidates the evolution of the two superimposed foreland basins of the Gulf of Papua,which underwent three-stage extrusion event in the Cenozoic,solving the lack of understanding of basin structure and regional tectonic evolution.In this paper,the temporal sequence and dynamic mechanism of the multi-stage tectonic events in the complex continental margin from extensional to compressional are clarified,providing evidence for plate tectonic reconstruction in the northern margin of the Australian Plate.