Abstract
1H spin-lattice relaxation time (T1) of kerogen as measured by NMR gives a regular increase with increasing burial depth. Organic maturation proceeds with a doubling of reaction rate for each 10°C increase in temperature. Relations between T1 and paleotemperature on the kerogen samples separated from argillaceous rocks of the MITI-Hamayuchi borehole were figured in due consideration of time. Paleogeothermal gradients on five boreholes and two outcropping section samples were estimated on the basis of the comparison with the standard figure of MITI-Hamayuchi. The gradient data obtained in this method show a slightly lower value than those calculated without any consideration of the absolute geologic age of kerogens. This evidence can be explained by slower sedimentation rate of all the sampling localities than in the MITI-Hamayuchi.
