This paper presents new paleomagnetic data from the lower Kameyama Formation of the Tokai Group. Oriented cores of silt and fine tuff were collected at four stratigraphic sites that are located in a stratigraphic section between the Otani-ike and Haradagawa volcanic ash beds. Analysis of stepwise demagnetization results revealed normal-polarity paleomagnetic directions for three sites and a reverse-polarity direction for one site. I conclude that the stratigraphic section between the two ash beds was deposited during Chron C2An (Gauss Chron: 3.596–2.581 Ma). A possible marine invasion event just before the deposition of the Otani-ike volcanic ash bed (Mori et al., Diatom, 30, 75–85, 2014) occurred during Chron C2An.3n (3.596–3.330 Ma).