Eocene Krabi basin (southern Thailand): Paleontology and magnetostratigraphy

We present the magnetostratigraphy of the late Eocene Krabi section from th e Krabi basin, Thailand. The investigated section is about 105 m thick and consists of red and yellow siltstones, sandstones, gray claystones, lignite s, and limestones. We collected 86 samples at 43 different stratigraphic le vels front the 105-m-thick section. The samples yielded a paleomagnetic dir ection, and paleomagnetic analyses give favorable demagnetization behaviors ; two magnetic components ran be isolated. Rock magnetic experiments show t hat the natural remanent magnetization generally results from the presence of titanomagnetite, The first component has roughly the direction of the pr esent-day field. The second component displays only reversed polarity, with a mean direction: declination = 192.34, inclination = -15.5, N = 71, alpha (95) = 4.7, k = 14 (after bedding correction). Mammalian biostratigraphy i ndicates a late Eocene age, Correlation to the Geomagnetic Polarity Time Sc ale relies on biostratigraphic data previously proposed for the fauna found in the same section. These correlations have been achieved by comparing va riations in the sedimentation rate derived from the alternative correlation , The proposed correlation puts the Krabi section in chron C12r or chron C1 3r. This suggests sedimentation rates of 4.9 and 9.4 cm/k.y., respectively. This correlation suggests that the Krabi section is older than 31 Ma and y ounger than 34 Ma.