PSV records from Tangra Yumco and Taro Co (Tibetan Plateau)

Magnetostratigraphy has been serving as a valuable tool for dating and confirming chronologies of lacustrine sediments in many parts of the world. Suitable paleomagnetic records on the Tibetan Plateau (TP) and adjacent areas are, however, extremely scarce. Here, we derive paleomagnetic records from independently radiocarbon-dated sediments from two lakes separated by 250 km on the southern central TP, Tangra Yumco and Taro Co. Studied through alternating field demagnetization of u-channel samples, characteristic remanent magnetization (ChRM) directions document similar inclination patterns in multiple sediment cores for the past 4000 years. Comparisons to an existing record from Nam Co, a lake 350 km east of Tangra Yumco, a varve-dated record from the Makran Accretionary Wedge, records from Lakes Issyk-Kul and Baikal, and a stack record from East Asia reveal many similarities in inclination. This regional similarity demonstrates the high potential of inclination to compare records over the Tibetan Plateau and eventually date other Tibetan records stratigraphically. PSV similarities over such a large area (>3000 km) suggest a large-scale core dynamic origin rather than small scale processes like drift of the non-dipole field often associated with PSV records.

磁地层学长期以来都是全球诸多地区湖相沉积物定年与厘定年代序列的重要手段。然而，青藏高原（Tibetan Plateau, TP）及其毗邻区域的合格古地磁记录却极度匮乏。本研究从藏中南部相距250 km的两个湖泊——当惹雍错（Tangra Yumco）与塔若错（Taro Co）——的经独立放射性碳定年的沉积物中获取了古地磁记录。通过对U通道样品开展交变退磁分析，特征剩磁（characteristic remanent magnetization, ChRM）方向显示，过去4000年以来多根沉积物岩心的倾角模式具有高度相似性。将该结果与纳木错（当惹雍错以东350 km处的湖泊）的已有记录、马克兰增生楔（Makran Accretionary Wedge）的纹泥定年记录、伊塞克湖与贝加尔湖的记录，以及东亚的地磁堆叠记录进行对比后发现，各地的倾角特征存在诸多共性。这种区域相似性表明，倾角数据在青藏高原范围内开展古地磁记录对比、乃至最终对其他青藏高原沉积物开展地层定年方面具备极高应用潜力。如此大范围（>3000 km）内的古地磁场长期变化（Paleosecular Variation, PSV）相似性，指示其起源于大尺度的地核动力过程，而非通常与古地磁场长期变化记录相关的非偶极场漂移这类小规模过程。