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岩浆活动的开始已被明确确立，古生代沉积和中生代火山作用相关的矿床已经或正在研究中。尽管在莫哈韦沙漠和科迪勒拉山脉边缘的其他地方已经提供了类似时间跨度的连贯和可信的模型，但这种转变本身的性质仍然未知。该项目将研究亚利桑那州南部古生代/中生代边界相关的火山碎屑岩、火山碎屑岩和火山地层。综合地质调查包括：1)对已知或推断出古生代至早中生代地层层序的剖面进行详细的野外测绘；2)接触带地层相分析，确定a)中生代早期岩浆活动的构造背景；3) U-Pb锆石b)早中生代岩浆活动的构造背景；3) U-Pb锆石年代学用于确定接触处火山岩岩浆活动的初始时间，或在适当情况下作为对比层序的工具。该研究将通过揭示亚利桑那州南部被动边缘沉积向俯冲岩浆作用过渡的时间和方式，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.