Juxtaposed Complexes in the Front Range of the Greater Caucasus

摘要

The Front Range of the Greater Caucasus stands out against other pre-Alpine tectonic units of this region because of its most complex section and clearly expressed nappe structure. The widespread Silurian-lower Visean island-arc volcanosedimentary rocks (Urup or Kizikol Complex) are overthrust in the northwestern sector of the Front Range by allochtho-nous ophiolites and the Atsgara Nappe composed of metamorphic rocks and granitoids. The Front Range crystalline complex consists of paragneisses, ortho-gneisses, and metabasic rocks. It emerges from under the Urup Complex to the southwest in the large Blyb Uplift. The crystalline complex is exposed as the Dakho, Beskes, and Sakhrai inliers to the north of the Urup Complex domain, where unmetamorphosed granitoid plutons are also known (figure).