Peach Springs Tuff: Its Bearing on Structural Evolution of the Colorado Plateau and Development of Cenozoic Drainage in Mohave County, Arizona

摘要: The Peach Springs Tuff, a welded ash flow of Miocene age, formerly blanketed minimum area 2,000 sq mi on both sides the western edge Colorado Plateau in Mohave County, Arizona, and filled northeast-trending, pre–Colorado River canyons cut through Paleozoic rocks. Paleomagnetic direction, petrography, field relations indicate that tuff is single cooling unit trachytic composition normal polarity. It was erupted across region prior to last major movement plateau marginal faults, completion significant amount Basin Range block faulting, development existing topographic relief. A pre-tuff period uplift erosion exposed Precambrian basement rocks directly west plateau. Gravel buried beneath Hualapai evidence northeast-flowing, incised drainage, time, which probably continued northward along Hurricane fault zone where younger canyon now. This ancient drainage system disrupted by volcanism, localized fluvial aggradation, followed gradual incision modern drainage. South Truxton Valley, there pre–middle divide present All geologic points an early middle Pliocene age for associated tributary fault.