Paleointensity study of Early Miocene lavas from Pingzhuang, Inner Mongolia, China

A paleomagnetic and geochronologic investigation has been conducted on 17 lava flows from Inner Mongolia, north China. Radiometric K‐Ar dating experiments give an age between 23 and 22 Ma for these volcanic units. Rock magnetic measurements of thermomagnetic curves and hysteresis loops show the primary carrier of remanence to be pseudo‐single domain titanomagnetite. Stepwise thermal demagnetization isolated a well‐defined direction of characteristic remanent magnetization (ChRM) in all studied lava flows with a mean direction of D/I = 359.8°/62.2° (α 95 = 3.8°). Fifty samples from 11 lavas were pre‐selected on the basis of thermomagnetic analyses to carry out Thellier‐Thellier paleointensity experiments with systematic partial thermoremanent magnetization (pTRM) checks. Twenty‐three samples from 7 lavas yield reliable paleointensity estimates with a mean virtual dipole moment (VDM) of (3.9 ± 0.9) × 10 22 Am 2 , about half the strength of the modern‐day field.