4:45 PM - 5:00 PM
[SEM34-20] A preliminary paleomagnetic result from Lake Suigetsu 2014 cores
Keywords:Lake Suigetsu, Varved sediments
Firstly, preliminary paleomagnetic analyses were conducted on two double-L channel samples, with progressive alternating field demagnetizations. All characteristic remanent magnetizations measured at 1-cm regular interval have almost constant directions close to the present geomagnetic field. This suggests the remanence of a core is intensively affected by secondary viscous remanent magnetizations (VRM). Next, we performed preliminary paleomagnetic analyses of discrete specimens with progressive thermal demagnetizations (THD). The result shows that secondary VRMs are removed below 350℃, and we confirmed that THD was more useful to isolate a primary remanent magnetization than AFD. From preliminary paleomagnetic analyses with progressive THDs for pilot discrete specimens collected from 100 to 10 cm intervals, we have obtained two excursional paleomagnetic directions. One is of an oriented specimen collected at a preliminary composite depth of about 32.50m, having negative inclination and northerly declination, and the other is of an unoriented specimen collected at a preliminary composite depth of 30.25m, having low positive inclination. Both are carried by a component with a temperature range from 400 to 590℃, which shows the carrier is magnetite. The Lake Suigetsu varve chronology suggests they are dated at 41 ka and 38 ka, respectively. The former or both may be correlated with the Laschamp excursion.