Sedimentologic and Chronostratigraphic Analysis of Cenozoic Strata, Southern Margin of Colorado Plateau: Tectonic and Paleogeographic Implications

科罗拉多高原南部和邻近的Verde盆地的新生代非海相沉积岩和火山岩被划分为五个构造地层包，它们记录了科罗拉多高原与亚利桑那州中部盆地和山脉省之间过渡带的演化阶段。划分依据有：1)地貌位置；2)碎屑成分和物源变化；3)构造背景和构造历史；4)层间火山岩辐射年龄。对这些地层单元的面积范围、岩性、物源、沉积环境和年龄的限制很少，对它们的解释也存在分歧。一种观点认为，科罗拉多高原悬崖是在渐新世期间由侵蚀形成的，另一种观点认为，它是在中新世期间由伸展断裂形成的，不到1000万年前。在对高原边缘地质历史的这些相互矛盾的解释得到解决之前，科罗拉多高原、盆地和山脉省的构造和地貌历史仍然是推测性的。本研究将建立南科罗拉多高原-莫高隆环地区新生代岩石的时代关系、环境和构造史。这些解释将基于对五个构造地层包的岩石学和相分析，以及基于古生物学、K-Ar和裂变径迹测年对它们年龄的更精确定义。

Cenozoic nonmarine sedimentary and volcanic rocks of the southern Colorado Plateau and adjacent Verde Basin are divided into five tectonostratigraphic packages that document stages in the evolution of the transition zone between the Colorado Plateau and the Basin and Range provinces in central Arizona. These two units are differentiated on the basis of, 1) geomorphic position, 2) clast composition and provenance variations, 3) tectonic setting and structural history, and 4) radiometric ages of intercalcated volcanics. The areal extent, lithology, provenance, depositional environments and age of these stratigraphic units are poorly constrained, and differences of opinion exist as to their interpretation. One school of thought is that the Colorado Plateau escarpment was formed by erosion during the Oligocene, and the other is that it was formed by extensional faulting beginning during the Miocene, less than 10 million years ago. Until these contradictory interpretations of the geologic history of the Plateau margin are resolved, the tectonic and geomorphic history of the Colorado Plateau and Basin and Range provinces remains speculative. This study will establish the age relationships, and environmental and tectonic history of the Cenozoic rocks in the southern Colorado Plateau-Mogollon Rim area. These interpretations will be based on petrologic and facies analyses of five tectonostratigraphic packages and more precise definition of their ages based on paleontology, K-Ar and fission track dating.