ROW/RPG: Tectonic and Stratigraphic Analysis of the Transition from Paleozoic Sedimentation to Mesozoic MagmaticActivity, Southern Arizona

亚利桑那州南部古生代被动边缘沉积的停止和中生代弧形岩浆作用的开始被明确确立，与古生代沉积和中生代火山作用有关的矿床已经或正在研究中。然而，这种转变本身的性质尚不清楚，尽管在莫哈韦沙漠和科迪勒兰边缘的其他地方已经提供了类似的时间跨度的连贯和可信的模型。该项目将研究与亚利桑那州南部古生界/中生界有关的碎屑岩、火山碎屑岩和火山岩地层。综合地质调查将包括：1)已知或推断古生代至早中生代地层沉积层序的详细野外填图，2)接触面上地层的相分析，以确定a)中生代早期岩浆作用的构造背景，3)U-Pb锆石b)中生代早期岩浆作用的构造背景；3)接触处火山岩的锆石U-Pb年代学，以确定岩浆活动的初始时间，或在适当情况下作为对比序列的工具。这项研究将通过揭示亚利桑那州南部被动边缘沉积向俯冲和岩浆作用转变的时间和方式，填补我们对科迪勒拉西南部晚古生代至早中生代构造演化认识的一个重要空白。

The cessation of passive margin sedimentation in Paleozoic time and the beginning of arc magmatism in Mesozoic time in southern Arizona are clearly established, and the deposits associated with both Paleozoic sedimentation and Mesozoic volcanism have been or are being studied. The nature of the transition itself remains unknown, however, although coherent and plausible models have been provided for a similar time span in the Mojave Desert and elsewhere along the Cordilleran margin. This project will investigate epiclastic, volcaniclastic, and volcanic strata associated with the Paleozoic/Mesozoic boundary in southern Arizona. An integrative geologic investigation will involve: 1) Detailed field mapping of sections where depositional sequences from Paleozoic to early Mesozoic strata are known or inferred; 2) Facies analysis of strata along the contact, in order to determine a) the tectonic setting of earliest Mesozoic magmatism; 3) U-Pb zircon b) the tectonic setting of earliest Mesozoic magmatism; 3) U-Pb zircon geochronology on volcanic rocks at the contact to establish the initial timing of magmatic activity, or where appropriate as a tool in correlating sequences. This research will fill an important gap in our understanding of late Paleozoic to early Mesozoic tectonic evolution of the southwestern Cordillera by shedding light on the timing and style of the transition from passive-margin sedimentation to subduction and magmatism in southern Arizona.