The canadian cordillera: testing contrasting models of orogenesis

板块构造为山系提供了一种解释：大陆沿会聚边缘的碰撞。喜马拉雅-阿尔卑斯山链起源于西部非洲和东部欧亚大陆之下的印度的企图俯冲。解释加拿大科迪勒拉的落基山脉就更难了。形变发生在8000万到5000万年前。但古北美陆壳向西延伸至海岸，在80 Ma时没有碰撞。因此，落基山脉被认为形成了2000公里的板块边缘内侧，在没有大陆碰撞的情况下。科迪勒地壳位于海洋性质的逆冲板块之下。这些“地体”的堆积被认为解释了落基山脉。然而，在落基山脉形成之前，地体的增长结束于200 Ma，&100 Ma。你如何解释一次200 Ma碰撞导致的80 Ma山带？

Plate tectonics provides an explanation for mountain systems: the collision of continents along a convergent margin. The Himalayan-Alpine chain stems from the attempted subduction of Africa, in the west, and India, in the east, beneath Europe-Asia. Explaining the Rocky Mountains of the Canadian Cordillera, is more difficult. Deformation occurred 80 to 50 million years ago. But ancient North American continental crust extends west to the coast, and there was no collision at 80 Ma. Hence the Rocky Mountains are thought to have formed 2000 kms inboard of a plate margin, and in the absence of a continental collision. The Cordilleran crust sits beneath thrust sheets of oceanic character. Accretion of these "terranes" was thought to explain the Rockies. However, terrane accretion ended by 200 Ma, >100 Ma before the Rockies formed. How do you explain an 80 Ma mountain belt as the result of a 200 Ma collision?