Russian Journal of Earth Sciences
Papers in press
Joint orientations from Paleozoic sedimentary rocks
in the Kyzyl Kum region, Uzbekistan, Central Asia
T. P. Belousov, Sh. A. Mukhamediev, and S.~F.~Kurtasov
Abstract
Over 18,000 joint orientations were measured from a spectrum of lithologies of
various ages at natural exposures in the Central Kyzyl Kum region. For each exposure, we
plotted joint orientation diagrams and identified local joint systems. Orientations of these
systems were established from both (i) density maxima of poles to joints on stereograms and
(ii) cluster analysis. Tilt-corrected data from coeval strata integrated over all the
measurement localities were used to identify regional joint directions and their relative
development. In Paleozoic sedimentary rocks these directions are, overall, close to fault and
fold trends in structures related to pre-Paleozoic, Caledonian, and Hercynian evolutionary
stages. However, regional joint systems display certain changes in their direction and
development depending on rock age. In Cretaceous deposits, regional joint directions are
chiefly inherited from those in Paleozoic strata. Our study of time-dependent changes in
regional jointing characteristics proves that, as the region kept developing, the primary
jointing became overprinted by additional random joints and tectonic joint systems. Our
previous attempt to reconstruct paleostresses in the study region from joints in sedimentary
rocks yielded results closely similar to fold trend data.