Fold deformations of the paleozoic basement roof in the Chunkurchak Trough, Kyrgyz Ala-Too Range

Abstract

A structural–geological study has been performed on the northern slope of the Kyrgyz Ala-Too Range. Deformations of the peneplaned Paleozoic basement surface, structures of granite disintegration, and morphostructural manifestation of Late Cenozoic tectonic movements have been investigated. Based on the location of pre-Paleocene peneplain remnants with the retained weathering mantle partly overlapped by Paleocene–Miocene sedimentary complexes, we have reconstructed the morphology of the folded surface of the Chunkurchak Trough separated from the Chu Basin at the early Miocene. The dome–fold forms, the morphology and arrangement of which are controlled by disintegration of the basement, have been described for the basement surface. It has been established that granites are broken by systems of steeply dipping, fanshaped, and gently dipping faults and fractures. Variously oriented insignificant offsets along slickensides, as well as displacements deduced from the geometry of fracture intersections, are a result of volumetric cataclastic flow of rocks. The tectonic mobility of disintegrated granites, which are abundant in the Paleozoic–Precambrian basement, explains the complexity and scale of tectonic processes initiated by Cenozoic activation. In paleotectonic reconstructions, which take into consideration tectonic flow and the redistribution of basement masses, the estimates of Cenozoic relative rapprochement of the Chu Basin and the Kyrgyz Ala-Too Range decrease substantially to 4–6 km.