Siliciclastic sediments of the Lower Miocene Tanabe Group crop out in southwest Kii Peninsula，Wakayama Prefecture，and represent a forearc basin succession deposited on the uplifted Shimanto accretionary complex．This report contains whole-rock XRF data for a stratigraphic collection of 87 sandstones and mudrocks from the Tanabe sequence．Fifty-four samples have also been analysed for REE and additional trace elementby solution ICP-MS after acid digestion and alkali fusion．The results show characteristic elemental sorting fractionation between sandstones and mudrocks in the members of the basal Asso Formation，which becomes more marked in the overlying Shirahama Formation，probably as a result of winnowing in a storm-dominated shelf depositional environment．Elemental abundances generally compare well with those of the Shimanto protoliths from which the Tanabe Group was derived．