Abstract Representative rock-magnetic experiments and petrographic studies on remagnetized limestones and dolostones from the Upper Cambrian La Flecha Formation (Quebrada La Angostura, Precordillera of La Rioja, Argentina) carrying a pre-tectonic Permo-Triassic secondary magnetization are reported in order to improve the understanding of the pervasive Sanrafaelic overprint that reset the palaeomagnetic record of most of the Early Cambrian to Mid-Ordovician units of the Argentine Precordillera and the San Rafael Block. The main carrier of the remagnetization is determined as fine-grained magnetite of chemical origin, though three additional ferromagnetic phases were identified (pyrrhotite, hematite and goethite). A power-law model fitted to hysteresis ratio data (Mrs/Ms vs. Bcr/Bc) defined an almost identical trend as that of the limestones from the Middle-Ordovician Ponon Trehue Formation (San Rafael Block, Mendoza province, Argentina) which were affected by the same regional event. Magnetic fabrics revealed by anisotropy of magnetic susceptibility and of anhysteretic remanence show mostly a pre-tectonic origin and, in some cases, a secondary overprint probably related to recent formation of magnetic minerals.

中文翻译：

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来自阿根廷 Precordillera 拉里奥哈省上寒武统 La Flecha 地层的再磁化石灰岩和白云岩

摘要 对来自上寒武统 La Flecha 组（Quebrada La Angostura，阿根廷拉里奥哈的 Precordillera）的再磁化石灰岩和白云岩进行了代表性的岩磁实验和岩相研究，这些石灰岩和白云岩带有前构造二叠纪二次磁化，以改善对普遍存在的 Sanrafaelic 套印的理解，将大部分早寒武世的古地磁记录重置为阿根廷 Precordillera 和 San Rafael Block 的中奥陶世单位。再磁化的主要载体被确定为化学来源的细粒磁铁矿，尽管确定了三个额外的铁磁相（磁黄铁矿、赤铁矿和针铁矿）。拟合滞后比数据的幂律模型（Mrs/Ms vs. Bcr/Bc) 定义了与受同一区域事件影响的中奥陶世 Ponon Trehue 组（阿根廷门多萨省圣拉斐尔区块）的石灰岩几乎相同的趋势。磁化率各向异性和非滞后剩磁所揭示的磁性织物主要显示出构造前的起源，在某些情况下，可能与最近形成的磁性矿物有关的二次叠印。