Tectonic Significance of Lower Cretaceous Gravels, Southern Canadian Rockies: Quantitative Models of Basin Development

PIS将研究加拿大哥伦布造山带南部和蒙大拿州邻近地区上侏罗统至下白垩统前陆地层序列的古地形、沉降和物源区发展史。哥伦布/塞维尔带标志着北美洲科迪勒拉晚中生代造山运动的顶峰，其长度总体上是连续的，在构造样式、时间和地层发育方面与邻近的前陆盆地相似。这两个地区都有上侏罗统泥质为主的河流沉积和东部古流；分布较广的下白垩统硅石-卵石墓；以及分隔两个单元的区域性亚白垩世不整合。然而，这两个地区在这些单元内的分布细节和古水流方向上有所不同。此外，两个带对构造驱动力的解释也不同，碰撞主要是哥伦布带的原因，而岩浆活动显然产生了塞维尔带。通过对南哥伦比亚前陆层序的定量分析，并将这些数据与我们之前对Sevier前陆层序的研究进行比较，我们将确定这两个层序是否记录了类似的演化史。如果是这样，那么在哥伦布带和塞维尔带活跃的两种不同的机制能产生相同的地层记录吗？如果不是，那么两个截然不同的逆冲带驱动机制是如何产生如此相似的地层包的？两个造山带之间的过渡在哪里？

PIs will study the paleotopographic, subsidence and source area development history of the Upper Jurassic to Lower Cretaceous foreland stratigraphic sequence along the southern part of the Columbian orogenic belt in Canada and adjacent parts of Montana. The Columbian/Sevier belt, which marks the culmination of Late Mesozoic orogency in the Norther American Cordillera, is generally continuous along its length and overall is similar in structural style, timing and stratigraphic development of the adjacent foreland basin. Both regions contain Upper Jurassic, mud-dominated fluvial deposits with easterly paleoflow; comparatively widespread Lower Cretaceous chert-pebble grave; and a regional sub-Cretaceous unconformity separating the two units. The two regions differ, however, in the details of distribution and paleoflow directions within these units. In addition, the interpretation of tectonic driving forces differ between the two belts with collisions primarily responsible for the Columbian belt and magmatic activity apparently generating the Sevier belt. By quantitatively analyzing the southern Columbian foreland sequence and comparing these data to our previous study of the Sevier foreland sequence we will determine if the sequences record a similar evolutionary history. If so, then can two different mechanisms active in the Columbian and Sevier belts produce the same stratigraphic record? If not, then how do two very different thrust belt driving mechanisms produce such grossly similar stratigraphic packages and where does the transition lie between the two orogenic belts?