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

该项目包括对上侏罗统-下白垩统Morrison、Cloverly和Kootenai组以及Gannett群等效地层的非海相岩石进行详细的区域年代地层、沉积学和层序地层分析。为了将层序地层学分析与前陆盆地海相记录相结合，研究将包括Sundance组（侏罗纪）和Thermopolis组（白垩纪）的海相岩石。数据收集的区域包括粉末河盆地和黑山，爱达荷-怀俄明州冲断带，以及蒙大拿州中西部大瀑布周围地区。将进行详细的相分析、岩石薄片和砾岩碎屑的点计数、河道复合体的露头作图、地球物理测井的地下对地对比、详细的磁地层学以及选定的富灰岩层的自体锆石的裂变径迹测年。该数据库的主要结果将是Morrison-Cloverly层序以及其在怀俄明州西部和北部的等效层序的完整年代和岩石地层格架。该数据库将覆盖25万公里的区域，从盆地的近端到靠近其东部末端。其他重要成果包括：(1)前陆盆地欠填和过填部分非海相岩石的层序地层格架；(2)为科迪勒拉前陆盆地早期充填建立了新的年代地层控制模式；(3)对科迪勒早期前陆盆地的外在（构造、隆起、气候）控制有了新的更完整的认识。研究结果还将提供一个最大的数据库，用于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.