Comparative Precambrian Stratigraphy and Structure Along the Mid-Continent Rift

作者：Albert B. Dickas · 发表于：AAPG Bulletin · 年份：1986 · DOI：10.1306/9488566a-1704-11d7-8645000102c1865d · 被引用次数：58 · 研究领域：Hydrocarbon exploration and reservoir analysis、Geological and Geochemical Analysis、Geological formations and processes

ABSTRACT The Mid-Continent rift is a geophysically identified tectonic structure that has been traced from Kansas northeastward into the Lake Superior district. A related arm has been identified by gravity as extending from eastern Lake Superior southeastward into the lower peninsula of Michigan. This rift is of Precambrian (Keweenawan) age and began developing approximately 1.1 b.y.B.P. For most of its extent, this continental-class rift system is buried below Phanerozoic strata. Outcrops are found only in east-central Minnesota, northwestern Wisconsin, and the upper peninsula of Michigan. The most accepted tectonic model of the Mid-Continent rift is that of a central horst partly covered by clastic rocks, bounded by high-angle faulting, and flanked by basins filled with clastic rocks. This model was developed in conjunction with field studies in the southwestern Lake Superior area, and generally has been adopted for Minnesota, Iowa, Nebraska, and Kansas. A comparable model has yet to be presented for the related arm extending into southern Michigan. In the Lake Superior outcrop belt, the oldest recognized rifted rocks are layered basalts of middle Keweenawan age. Overlying these basalts is an upper Keweenawan thick sedimentary sequence composed of the Oronto (older) and Bayfield (younger) Groups. These sedimentary rocks are almost entirely clastic with texture ranging from conglomerate to shale (mudstone). Rock colors are principally reds and browns, with secondary shades o...