High-resolution paleomagnetic and sedimentological investigations on the Tibetan Plateau for the past 16 ka cal BPThe Tangra Yumco record

The spatial distribution of paleomagnetic secular variation (PSV) records on the Tibetan Plateau and adjacent areas covering the Holocene and Late Glacial is sparse. In order to reconstruct PSV in this area, a piston core covering the past 17.5 ka cal B.P. retrieved from Lake Tangra Yumco, southern-central Tibetan Plateau, was analyzed. In the laminated sediments, several event layers are intercalated. Those were identified by sedimentological analysis and excluded for age-depth modeling and interpretation. Paleomagnetic measurements on u-channels reveal two contrasting core sections. The lower section (dated to 17.5-15.9 ka cal B.P.) is very coarse grained (up to 220 mu m) and characterized by low intensities (0.8 mA m(-1)) and high maximum angular deviation values (mean 25 degrees), making it unsuitable for PSV reconstruction. In contrast, the upper unit (dated to <15.9 ka cal B.P.) yields ideal properties with a well-defined magnetization carried by low-coercivity minerals in the pseudo single domain state making those younger sediments a proper record for PSV studies. The robustness of the PSV reconstruction for the past 3000 years is highlighted by a comparable inclination and declination pattern of three short sediment cores (2 m) from Tangra Yumco. On a regional scale, the obtained inclination signal for the past 15.9 ka cal B.P. is in good agreement with the Lake Baikal record (3000 km to the North), PSV stack for East Asia, as well as with predictions of geomagnetic field models. This study is a step forward in constructing a PSV reference curve for central Asia.