A REVISE OF STRATIGRAPHY BASE ON MAGNETIC POLARITY AND RADIOMETRIC AGE DATA: CASE STUDY OF ROCK GROUP FROM TOTTORI AND HYOGO PREFECTURE, JAPAN:

PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

A REVISE OF STRATIGRAPHY BASE ON MAGNETIC POLARITY AND RADIOMETRIC AGE DATA: CASE STUDY OF ROCK GROUP FROM TOTTORI AND HYOGO PREFECTURE, JAPAN

Eddy Zulkamaini Gaffar * and Masayuki Torii **

* Research Center for Geotechnology, Indonesian Institute of Science,
** Kyoto University, Japan

ABSTRACT

Paleomagnetic measurements were carried out on the Pliocene volcanic rocks in the Teragi

Group.

Samples were collected from 12 sites that included three lithologic units of the Teragi Group, in the border area between eastern Tottori and northwestern Hyogo Prefectures. Samples of Miocene granItes also were collected at three sites. Stability of natural remanent magnetization was examined by progressive demagnetization with thermal and alternating field methods. All samples revealed charac­teristic paleomagnetic directions which we assumed to be primary direction.

By using the magnetic polarity and radiometric age data, the stratigraphy of The Teragi Group can be revised. The lower parts of the Teragi Group (Lower Tuff, Haruki Mud and Terada Volcanics) showed normal polarity (NB] polarity zone), but the upper part (Upper Tuff) indicated reversed polarization as RB] polarity zone.