Home – Home – Jornals – Russian Geology and Geophysics 2001 number 4

Based on geodynamic data, we consider paleogeographic positions of basins where sediments rich in organic matter (black-shale facies) accumulated in three Devonian epochs. A brief description is given to black-shale formations (series, members, and horizons) and the position of zones of their accumulation in the basins and in the cycles of sedimentation. We study the evolution of the geologic positions of these zones and their dependence on the arrangement of continents and the sequence of transgressive events.
In the Early Devonian, when the continents were located relatively close to each other, black-shale sedimentation basins existed on their periphery, in the area transitive between shoal and pelagic zones. In the Middle Devonian, such basins also appeared in pre-orogeny zones, and black-shale formations accumulated in more shallow-water settings as compared with the Early Devonian black shales. In the Late Devonian, the shelf areas expanded, and the number of black-shale zones and their areas considerably increased. In stratigraphic sections, black-shale facies occur in the middle parts of sedimentation cycles, which are the most transgressive and subsided.