11:45 AM - 12:00 PM
[SEM34-05] Integrated magnetostratigraphy and biostratigraphy of the Upper Triassic bedded chert sequences from Inuyama area, central Japan
Keywords:Late Triassic, magnetostratigraphy, biostratigraphy, bedded chert, Mino belt, Panthalassa
Here we present Carnian to Rhaetian magnetostratigraphy and biostratigraphy (conodont and radiolaria) of the Upper Triassic bedded chert successions from the Mino belt, Inuyama area, central Japan. 416 oriented samples were collected at four sections (Section H, N, Q, R) where Sugiyama (1997) investigated the radiolarian biostratigraphy. All samples were thermally demagnetized and analyzed at the paleomagnetic laboratory of Center for Advanced Marine Core Research, Kochi Univ.
Based on detailed study of the conodont biostratigraphy from the study sections, seven conodont zones are recognized and calibrated with the Sugiyama's radiolarian zone. Thermal demagnetization showed four distinct remanent magnetization components from the cherts. The highest blocking temperature component shows positive reversal test and is regarded as the primary remanent magnetization, which produced a magnetostratigraphy of the Carnian to Rhaetian. Paleomagnetic polarity reversals observed at the vicinity of Carnian/Norian boundary and middle Norian/upper Norian boundary are correlated with those of Tethyan marine sections (Pizzo Mondello and Silickà Brezovà). Assuming that the rocks in the two Tethyan marine sections were deposited in the Northern Hemisphere, the magnetostratigraphic correlation indicates that the bedded chert of Inuyama area was deposited in the Northern Hemisphere. The mean inclination of the last demagnetized component suggests the bedded chert originated in an equatorial area.