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Fig. 5 | Journal of Palaeogeography

Fig. 5

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

Fig. 5

Sketch showing procedures of the peatland productivity analysis. f1, f2, f3 represent the main average frequencies (cyclesm− 1) of the spectral analysis. t1, t2, t3 represent Milankovitch periodicities of 123 kyr (eccentricity), 35.6 kyr (obliquity), and 21.2 kyr (precession). T1, T2, T3 represent different cycle length (m). Vcoal represents rate of coal deposition (mkyr − 1). L represents thickness of coal seam (m). Tcoal represents period of coal deposition (kyr). ρ is the measured dry bulk density of coal (gcm− 3). X1 is the measured average carbon concentration of the coal. X2 is carbon loss percentage during the coalification. VC in coal represents the long-term average carbon accumulation rate for the coal (gCm− 2a− 1). VC in peatland represents the long-term average carbon accumulation rate for the initial peatland (gCm− 2a− 1). X3 is the quantitative relation between the Holocene net primary productivity (NPP) level (gCm− 2a− 1) and the long-term average carbon accumulation rate for the peatland

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