Well-exposed lava sequences with available geochronological information may provide invaluable information on the fine characteristics of the Earth's magnetic field variation. A paleomagnetic study has been performed on twenty Pleistocene age, sub-horizontal lava flows in the Javakheti Highland (Lesser Caucasus). The sequence is formed by calc-alkaline basaltic lavas and is divided by a thin sedimentary layer in its upper part. We obtained two new radiometric ages: an age of 1.93±0.09 Ma for the flows below the sedimentary layer and 1.78±0.11 Ma for the upper part of the sequence. Thermomagnetic susceptibility vs. temperature curves indicate that remanence is carried by ferrimagnetic minerals like magnetite, titanomagnetite or titanomaghemite. Reliable paleomagnetic results could be obtained from all 20 analyzed flows, yielding the following reverse-polarity mean direction for the whole sequence: inclination I =-61.5°and declination D =200.1° (N = 20; α₉₅ =3.1°; k=114). This direction does not agree with the expected one. The discrepancy can be explained by an apparent clockwise 17.1 ± 6.1° vertical-axis rotation. Alternatively, such moderate deviation may be due to some unstable geomagnetic regime or undersampled paleosecular variation. Isotope ages obtained in the present study indicate that the Toloshi sequence was emplaced during the normal-polarity Olduvai subchron, but palaeomagentic results indicate a reverse-polarity magnetization. At the same time, the analysis of virtual geomagnetic pole (VGP) scatter indicates that the Toloshi sequence was probably formed during a short time, insufficient to average paleosecular variation. These results suggest that the Olduvai subchron is probably disrupted by a short reverse-polarity episode.

充分暴露的熔岩序列和可用的年代学信息可能会提供有关地球磁场变化的精细特征的宝贵信息。已经对爪哇高地（莱瑟高加索地区）的二十个更新世年龄，次水平的熔岩流进行了古磁研究。该层序由钙碱性玄武岩熔岩形成，并在其上部被一薄层沉积层划分。我们获得了两个新的辐射年龄：沉积层以下流动的年龄为1.93±0.09 Ma，序列上部为1.78±0.11 Ma。热磁化率与温度的关系曲线表明，剩磁是由诸如磁铁矿，钛磁铁矿或钛磁铁矿的亚铁磁性矿物携带的。从所有20个分析流中都可以获得可靠的古磁结果，N = 20；α ₉₅= 3.1°；k = 114）。这个方向与预期的方向不一致。差异可以通过明显的顺时针旋转17.1±6.1°垂直轴旋转来解释。或者，这种中等偏差可能是由于某些不稳定的地磁状态或欠采样的古生物变化引起的。在本研究中获得的同位素年龄表明，Toloshi序列是在正极性Olduvai子年代发生的，但古成岩结果表明其反极性磁化强度。同时，对虚拟地磁极（VGP）散点的分析表明，Toloshi序列可能是在短时间内形成的，不足以使古目视变化平均化。这些结果表明，Olduvai亚时相可能被短暂的反极性事件破坏了。