Details

Autor(en) / Beteiligte

• Yang, Xiaoqiang
• Zhang, Tingwei
• Zhang, Enlou
• Toney, Jaime
• Zhou, Qixian
• Xie, Yixuan

Titel

Paleosecular Variations During the Last Glacial Period From Tengchong Qinghai Lake, Yunnan Province, China

Ist Teil von

• Journal of geophysical research. Solid earth, 2022-03, Vol.127 (3), p.n/a

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2022

Quelle

Wiley Online Library

Beschreibungen/Notizen

• In recent years, the evolution of the magnetic flux lobes in terms of location and intensity has been attributed to paleosecular variation of the geomagnetic field, reflecting outer‐core fluid convection close to the core‐mantle boundary. However, most results were based on observational data for the past 400 years supplemented by sparse archeomagnetic studies with data for approximately 3 kyr. In this paper, we construct a relative paleointensity (RPI) record and an inclination record spanning the past ∼90 kyr based on two cores from Tengchong Qinghai Lake (Yunnan Province, China), a closed crater lake that formed in the late Pleistocene. The evolution of flux lobes and the non‐dipole field can be assessed on a much longer time scale. Although the concentration and domain state of magnetic grains in the cores vary significantly, the RPI record is still representative of geomagnetic field features in the region of Yunnan Province, China. The contrasting trends in RPI with the records for eastern China since the late Holocene indicate the southeastward migration of the Siberian flux lobe. During the last glacial period, the RPI records of Tengchong Qinghai Lake and the North Atlantic Ocean show opposite trends, denoting the diverse and strong influence of the two flux lobe systems. The strong reverse flux lobe in the North Atlantic Ocean strengthened the non‐dipole field, while the weak normal flux lobe in Tengchong weakened the non‐dipole field. Plain Language Summary Earth's magnetic field is composed of two main field components: a dipole field and a non‐dipole field. Although the non‐dipole field constitutes a minor component of the geomagnetic field, its variations in strength and location over different time scales have a significant influence on the surface expression of the geomagnetic field. The flux lobes arising from the fluid convection at the boundary between the core and mantle may produce the main components of the non‐dipole field. In recent years, the distribution of magnetic flux has been discussed based mainly on instrumental data and archeomagnetic data spanning a few kyr, which limits our understanding of flux lobe evolution on a much longer time scale. In this paper, we reconstruct a relative paleointensity (RPI) and an inclination records over the past ∼90 kyr from sediments of a closed volcanic lake in Tengchong, Yunnan Province, China. The results show that the RPI in the Tengchong area differs from the records for eastern China in the Holocene and from the records in the North Atlantic Ocean during the last glacial period. We conclude that a flux lobe may have played an important role in the non‐dipole field in the Tengchong and in the North Atlantic Ocean. Key Points High‐resolution paleosecular variation records, including relative paleointensity (RPI) and inclination for the past 90 kyr, are derived from sediments in a closed lake in China The Holocene RPI trend obtained differs from records from records from eastern China, indicating the movement and intensification of the Siberian flux lobe The opposing RPI patterns from the lake and the North Atlantic Ocean during the last glacial period indicate the influence of flux lobe systems on the non‐dipole field