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Fig. 3 | Journal of Palaeogeography

Fig. 3

From: Using geophysical logs to identify Milankovitch cycles and to calculate net primary productivity (NPP) of the Late Permian coals, western Guizhou, China

Fig. 3

Spectral analysis of the Late Permian coal seams from the Songhe mining area, western Guizhou. a, b, c show spectral analysis results of the 17 + 18#, 17# and 18# coal seams respectively. DLW, DEN (Density) and GR represent apparent resistivity, gamma-gamma and natural-gamma logs respectively. MEM and MTM represent the maximum entropy method and multitaper method respectively

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