The canadian cordillera: testing contrasting models of orogenesis

板块构造学说为山系的形成提供了一种解释：大陆沿着收敛边缘的碰撞。喜马拉雅山脉-阿尔卑斯山脉链源于西部的非洲和东部的印度试图在欧亚板块之下俯冲而成。解释加拿大科迪勒拉山脉的落基山脉就比较困难了。变形发生在八千万到五千万年前。但古北美大陆地壳向西延伸至海岸，80ma时没有碰撞。因此，落基山脉被认为是在没有大陆碰撞的情况下，在板块边缘内侧2000公里处形成的。科迪勒拉地壳位于具有海洋特征的逆冲层之下。这些“地形”的增生被认为可以解释落基山脉的形成。然而，在落基山脉形成之前，地表增生在200 - 100 Ma结束。你如何解释一次200毫安的碰撞产生的80毫安的山带？

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?