Collaborative Research: Regional Chronostratigraphic and Sequence Stratigraphic Analysis of Central Cordilleran Foreland Basin

该项目包括详细的区域年代地层学、沉积学和层序地层学分析，包括对上侏罗统-下白垩统莫里森组、克洛弗利组和库特奈组以及甘尼特群的相当地层的陆相岩石进行分析。为了将层序地层学分析与前陆盆地的海洋记录结合起来，这项研究将包括Sundance(侏罗纪)和Thermopolis(白垩纪)地层中的海相岩石。数据收集区域包括波德河盆地和黑山，爱达荷州-怀俄明州逆冲带，以及蒙大拿州中西部的大瀑布周围地区。将进行详细的相分析、岩石薄片和砾岩碎屑计数的点计数、河流河道复合体的露头填图、地球物理测井曲线的地下-地表对比、详细的磁地层学和选定的富灰层中真面体锆石的裂变径迹测年。这个数据库的主要结果将是一个完整的莫里森-克洛弗利层序及其在怀俄明州西部和北部的等价物的年代和岩石地层格架。该数据库将覆盖-25万公里的区域，从盆地的近端到东端附近。其他重要成果包括：(1)前陆盆地充填不足和过充填部分的陆相岩石的层序地层格架；(2)科迪勒前陆盆地早期充填的新的年代地层学控制模式；(3)对早期科迪勒前陆盆地的外部(构造、海平面、气候)控制的新的和更完整的认识。这一结果还将提供最大的数据库之一，以便与现有的和正在开发的前陆盆地地球物理模型进行比较。

The project consists of a detailed, regional chronostratigraphic, sedimentologic, and sequence stratigraphic analysis of nonmarine rocks in the Upper Jurassic - Lower Cretaceous Morrison, Cloverly, and Kootenai Formations and the equivalent strata of the Gannett Group. In order to integrate sequence stratigraphic analysis with the marine record of the foreland basin, the study will include bounding marine rocks in the Sundance (Jurassic) and Thermopolis (Cretaceous) Formations. Areas of data collection include the Powder River basin and Black HIlls, the Idaho-Wyoming thrust belt, and the area surrounding Great Falls in west-central Montana. Detailed facies analysis, point counts of petrographic thin sections and conglomerate clast counts, outcrop mapping of fluvial channel complexes, subsurface-to-surface correlations of geophysical well logs, detailed magnetostratigraphy, and fission- track dating of euhedral zircons from selected ash-rich horizons will be performed. The principal results of this data base will be a complete chrono - and lithostratigraphic framework for the Morrison-Cloverly sequence and its equivalents to the west and north of Wyoming. The data base will span an area covering - 250,000 km , from the proximal part of the basin to near its eastern terminus. Among other important results will be (1) a sequence - stratigraphic framework for nonmarine rocks in both underfilled and overfilled parts of foreland basins; (2) a new chronostratigraphically controlled model for early filling of the Cordilleran foreland basin; and (3) new and more complete understanding of the extrinsic (tectonic, eustatic, climatic) controls on the early Cordilleran foreland basin. The results also will provide one of the largest data bases for comparison with available and developing geophysical models for foreland basins.