Выпуск: 1 , Том: 51 , Год издания: 2016

Contents and distribution of U, Th, and K in rocks of the so-called normal and anomalous sections of the Upper Jurassic-Lower Cretaceous Bazhenov Formation in the West Siberian marine basin are examined. In normal sections of this unit, the most widespread clayey-siliceous rocks deposited in the course of slow "background" sedimentation, are characterized by high (relative to black shales) contents of U (66.5 ppm) but moderate contents of Th (5.07 ppm) and K (0.81%). In mudstones identified as turbidite sediments with high sedimentation rate, contents of these elements are 11.68 ppm, 11.00 ppm, and 2.70%, respectively. In rare clayey-silty sediments of anomalous sections marked by maximal deposition rates, contents of these elements are 2.15 ppm, 3.78 ppm, and 2.15%, respectively. Uranium is associated mainly with organic matter and partly with apatite (phosphate clasts of fish skeletons) and calcite; thorium, with clay minerals; potassium, with clay minerals and K-feldspar. The U content is 345 ppm at high apatite concentration (7%)