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Researchers present a high-resolution paleomagnetic record of the early Matuyama chron, including the Réunion subchron and the onset of the Olduvai boundary, from a 168-m-thick marine succession in the Boso Peninsula, central Japan. The record shows the Réunion subchronozone and the lower Olduvai reversal at 38.6-44.6 m and 142.0 m, respectively. Sedimentation rates were calculated as 25 cm/ky and 57 cm/ky between the lower and upper Réunion boundaries and between the upper Réunion boundary and lower Olduvai boundary. The virtual geomagnetic pole (VGP) passed across the equator within a similar longitudinal band over Africa at both the upper and lower Réunion boundaries. Relative paleointensity (RPI) values for the entire Réunion interval were generally lower than the average for the entire interval from the Réunion to the lower Olduvai subchronozone. The VGP for the lower Olduvai reversal boundary did not pass across the equator within a narrow longitudinal band but settled in several cluster areas. The RPI declined rapidly and recovered slowly as the VGP moved rapidly between cluster areas. The study provides one of the most detailed records of geomagnetic reversals from marine sediments, helping to understand the dynamics of geomagnetic reversals.