Research was carried out to estimate the possibility of determining the direction and strength of the ancient geomagnetic field $(\textbf{H}_{\rm an})$ by natural remanent magnetization ($\textbf{I}_n$) of nine oriented samples from traps of the Minor Botuoba Region (Yakutia) aged 260 Ma. Five samples (Pi-10, K-4, K-6, 315–13, and Ki-2) are characterized by negative polarity of $\textbf{I}_n$, while four samples (nos. 334-5, 331–2, 315–11, 299–2) have positive polarity as does the recent geomagnetic field in this region. The ferrimagnetic constituent of the samples with reverse I n polarity appears to be quite variable: samples K-4 and K-5 are characterized by low Curie points ($T_c\approx200^{\circ}$C) of the ferrimagnetic phase, sample Ki-2 contains single-phase oxidized titanomagnetite with $T_c\approx310^{\circ}$C, and the $T_c$ of the Pi-10 ferrimagnetic phase is 540°C. Hence, it may be concluded that the primary remanent magnetization of the first two samples was formed in a reverse polarity field. These samples also may be used to determine the paleostrength of the geomagnetic field. The properties of traps containing single-phase oxidized (sample Ki-2) and disintegrated (sample Pi-10) titanomagnetite require additional investigation. Samples with positive $\textbf{I}_n$ polarities are characterized by the self-reversal phenomenon upon thermal demagnetization of the natural remanent magnetization, which was most likely caused by the occurrence of titanomagnetite exsolution textures in ferrimagnetic grains. The paleoinformation value of the $\textbf{I}_n$ of these samples is doubtful.
91.25.N- Paleomagnetism
91.25.Ng Paleomagnetism
Faculty of Physics, Moscow State University, Moscow, 119991, Russia