关键词: 古地磁, 风成红层, 晚白垩世, 信江盆地, 华南

Abstract: Red bed is one of the important targets in paleomagnetic studies. Previous research has focused mainly on paleomagnetism
of lacustrine-fluvial red beds, while paleomagnetism of aeolian red beds has been rarely investigated. As a result, the reliability of
paleomagnetic data from aeolian red beds and the remanence acquisition in different depositional processes remain poorly understood.
In this study, we carried out a paleomagnetic study of the Upper Cretaceous aeolian red beds from the Tangbian Formation (Fm) and
lacustrine-fluvial red beds from the Hekou Fm of the Guifeng Group in Xinjiang Basin, Jiangxi Province, China. The purposes of this
study are to investigate the reliability of the paleomagnetic records of aeolian red beds and the influence of different depositional
processes on magnetic remanence acquisition by comparing the paleomagnetic data of aeolian red beds and those of lacustrine-fluvial
red beds. Stepwise thermal demagnetization of the samples shows that only 19% of the aeolian red beds samples of Tangbain Fm yield
stable characteristic remanent magnetizations (ChRMs) with convex intensity decay curves, indicating a primary origin of remanence
carried by detrital hematite grains. The mean of the ChRMs of the Tangbian Fm is Ds=15.6 °, Is=28.9 °, n=25, κ=13.0, α95=8.3 ° after
tilt correction, corresponding to a Late Cretaceous paleopole at Latitude=70.7 °, Longitude=245.6 °, A95=6.8 °. The new paleopole is
indistinguishable with the coeval paleopole from lacustrine-fluvial red beds of the Ganzhou area and the recently updated Late
Cretaceous paleopole of South China, suggesting that the aeolian red beds of the Tangbian Fm can carry reliable paleomagnetic records.
Most lacustrine-fluvial red bed samples from the Hekou Fm failed to yield stable ChRMs. The anisotropy of magnetic susceptibility
(AMS) data of the Tangbian Fm and the Hekou Fm indicate sedimentary fabrics. Rock magnetic results of representative samples show
that remanence are carried by hematite and magnetite. Further investigations of the Tangbain Fm aeolian red beds with thin section
observations and redness analysis indicate that particle size and degree of cementation may affect the stability of remanent
magnetization of aeolian red beds.

Key words: paleomagnetism, aeolian red beds, Late Cretaceous, Xinjiang Basin, South China