CATAGENESIS OF ORGANIC-MATTER OF MESO-CEN OZOIC DEPOSITS IN THE INDIGIRKA-ZYRYANKA TROUGH (IN CONNECTION WITH PETROLEUM POTENTIAL)

On the basis of vitrinite reflectivities measured in boreholes and out crops, we have studied the catagenetic zoning of the sedimentary cover of the Indigirka-Zyryanka trough. This zoning ranges from PC to AC. I t has been established that in the axial part of the trough and piedmo nt zone (PZ) the organic matter conversion is determined by regional c atagenesis with paleogeothermal gradients of about 3.0 degrees C/100 m in the PZ front and 3.5-3.9 degrees C/100 m in its back. On the near- platform wing of the trough it is superimposed with magmathermal and c ontact catagenesis related to the Late Cretaceous tectonomagmatic acti vity on the Alazei Uplift, causing anomalous paleogradients (up to 9.4 degrees C/100 m) and high-amplitude erosions (up to 2 km). According to structure-catagenetic signs, depths favorable for searching for hyd rocarbon accumulations were determined.