A Miocene river in northern Arizona and its implications for the Colorado River and Grand Canyon

[摘要] Thesouthwesterly course of the pre–late Miocene Crooked Ridge River can be traced continuouslyfor 48 km and discontinuously for 91 km in northern Arizona. It is visible todayin inverted relief. Pebbles in the river gravel came from at least as far northeastas the San Juan Mountains. The river valley was carved out of easily eroded Jurassicand Cretaceous rocks, whose debris overloaded the river with abundant detritus,possibly steepening the gradient. After the river became inactive, the regionaldrainage network was rearranged twice, and the Four Corners region was lowered byerosion 1–2 km. The river provides constraints on the history of the Colorado Riverand Grand Canyon; its continuation into lakes in Arizona or Utah is unlikely, asis integration of the Colorado River through Grand Canyon by lake spillover. Thedownstream course of the river was probably across the Kaibab Arch in a valley roughlycoincident with the present eastern Grand Canyon.

[学科分类] 地质学

[关键词] Fire safety;fatal fires;smoke alarms