Time scale and denudation thickness calculation of Carboniferous Kalashayi Formation in the Bamai area, Tarim Basin

Restoration of paleogeomorphology plays a very important role in guiding the search for high-quality reservoirs and dominant source rocks of oil and gas, during which the calculation of denudation thickness is the vital step. In this study, the abundant GR curves together with the main frequency and astronomical time scale of the Carboniferous Kalashayi Formation in the Bamai area, Tarim Basin, were used to establish the “floating” astronomical chronological scale with relative time concept and high-precision stratigraphic sequence frame using spectral analysis, wavelet transform and EMD. The results show that a complete Milankovich cycle presents in the formation as a result of astronomical orbit control during the deposition of the formation; and the astronomical chronological scale and the stratigraphic sequence frame is based on the understanding that the imf₃ component calculated by EMD method is basically consistent with the number of stratigraphic cycles under the control of e₁. Based on the results of EMD method, the relationship between the number of missing cycles and the average cycle thickness revealed by drilling in different regions was used to accurately calculate the denudation thickness of the Carboniferous Kalashayi Formation. The erosion thickness of the Kalashayi Formation of the Carboniferous in the study area varies between 0 and 390 m with the overall denudation characterized by “intensive in the west and mild in the east”. The slope area near the BT5 well in the middle of the study area is suggested to be a potential exploration target for oil and gas. The ideas and methods proposed provide a reference for the construction of high-frequency stratigraphic sequence framework, the establishment of “floating” astronomical chronological scales, and the precise calculation of formation erosion thickness in not only the study area, but also areas with similar geological settings.