Cordilleran tectonics

本研究旨在阐明以加拿大科迪勒拉为例的山带形成过程。重点研究了位于加拿大南部和蒙大拿州北部的科迪勒兰前陆逆冲褶皱带的起源和演化，该带形成于北美洲祖先与西缘俯冲带的汇合过程中。逆冲-褶皱带由地壳上的地层片和片组成，这些地层片和片是由被称为“山间地体”的主要是海洋盆地和火山岩的上覆构造拼贴作用刮下来的，这些构造拼贴作用是从下方的祖先北美大陆及其西部边缘刮下来的。这项研究包括准备“修复”的古地质构造剖面和地图，这些地图描绘了在逆冲和褶皱之前存在的位置和构造的表壳岩石。三个深沉积盆地（贝尔特-珀塞尔盆地、温德米尔盆地和科迪勒拉新生代地槽）将恢复它们彼此之间的原始关系，并与科迪勒拉下延伸的北美古元古代基底的深部地壳结构恢复原始关系。重建工作将主要依据地质图和平衡的深部构造剖面。另外五张1:5万比例尺的地质图，包括构造剖面和两张新的区域地质图。将根据现有的现场数据完成深层平衡结构剖面，以弥补该区域中心的关键信息差距。深部地震成像，连同重磁异常图、地质图、变质岩和火成岩的热时和地球气压数据，将提供变形的区域和时间变化以及深部地壳和岩石圈结构的约束条件。初步分析表明，横断带的累计位移为100 ~ 300 km。这项研究的结果有望阐明加拿大东南部科迪勒拉及其丰富的化石燃料和矿产资源是如何、何时、以及为什么形成的，也可以告诉许多对落基山脉着迷的人，他们对山脉的好奇心是如何形成的。

This research aims to elucidate some of the processes involved in the formation of mountain belts as exemplified by the Canadian Cordillera. The focus is on the origin and evolution of the Cordilleran foreland thrust-and-fold belt in southern Canada and northern Montana, which formed during convergence between ancestral North America and subduction zones along its western margin. The thrust-and-fold belt consists of sheets and slices of supracrustal strata that have been scraped off the under-riding ancestral North American continent and its western margin by an over-riding tectonic collage of accreted, mainly ocean-basin, volcanic rocks called "Intermontane terrane". The research involves preparation of "restored" paleogeological structure sections and maps that portray the supracrustal rocks in the locations and configurations in which they existed prior to the thrusting and the folding. Three deep sedimentary basins from which most of the displaced rocks came (Belt-Purcell, Windermere, and Cordilleran miogeocline) will be restored to their original relationships with each other and with the deep crustal structures in the Paleoproterozoic basement of North America that extends under the Cordillera. The reconstructions will be based mainly on geological maps and balanced deep structure sections. Five additional 1:50,000-scale geologic maps, with structure sections and two new regional. deep, balanced structure sections will be completed from available field data to close a critical information gap in the centre of the region. Deep seismic imaging, together with gravity and magnetic anomaly maps, geological maps, and thermochronometric and geobarometric data from metamorphic and igneous rocks will provide constraints on regional and temporal variations in deformation and on the deep crustal and lithospheric structure. Preliminary analyses indicate that the cumulative displacement across the belt is >300 km. The results of this research can be expected to clarify how, when, and why the southeastern Canadian Cordillera and its rich fossil fuel and mineral resources formed, and also to inform the many people whose fascination with the Rockies arouses their curiousity about the mountains came to be.