北极阿拉斯加北坡盆地挤压正断层特征及其发育演化模式

Compressional Normal Faults and Its Development and Evolution Mechanism,North Slope Basin,Alaska,Arctic

阿拉斯加北坡盆地为北极圈内重要的富油气盆地,盆地自早白垩世晚期以来一直处于布鲁克斯前陆挤压状态,然而在盆地西北部楚科奇海域却发现了大量的晚期正断层。断层可进一步细分为2期3组断裂,分别为EW向、NNE向、NNW向断层,剖面上均表现为断面陡直的平行板状正断层,断距相对较小;平面上主要分布于古隆起及其周缘,部分NNE向和NNW向断层直接相连,呈"锯齿状"折线展布。晚期断层的发育受2个期次、2个方向挤压应力的控制,早白垩世晚期,受南北向挤压作用,首先形成NNW向和NNE向2组剪切节理,而后形成EW向断层。晚白垩世,受东西向挤压作用,断层沿早期2组节理发育,使NNW向和NNE向断层部分呈"锯齿状"。

North Slope Basin is an important petroliferous basin in Alaska, Arctic. The Basin has been in compressing stage since the Early Cretaceous, but lots of normal faults have been identified in the north- west of Chukchi Sea, North Slope Basin. The faults can be further subdivided into three groups in two phases, EW and NNE/NNW trending. The slabby faults plan is high-angle faults in cross section, with small fault throw. Normal faults are mainly distributed in the paleohigh and the adjacent areas. Some faults are in ＂jagged＂ distribution in plane, as result of part of NNE/NNW trending faults connecting di- rectly. The fault development is mainly controlled by two compressive events in mutually perpendicular di- rections. Early Cretaceous, NNE/NNW trending shear joint fissures were formed firstly by the North- South compression, and then formed the EW trending faults. Late Cretaceous, NNE/NNW trending faults were formed along the earlier NNE/NNW trending joint fissures by the East-West compression, and also some faults were ＂jagged＂ because of earlier NNE/NNW trending joint fissures.