Full vector geomagnetic secular variation in central Mexico as derived from volcanic rocks younger than about 50 ka

跨墨西哥火山带内持续的火山活动提供了古地球磁场的高质量档案，允许恢复方向变化以及绝对古强度。由于没有足够的火山年代来详细的长期变化曲线，我们假设首先在地貌年龄估计的基础上选择湖泊流，从0-50 ka的年龄范围。这些熔岩流应该用14C法测定年代，使用火山喷发直接产生的木炭。对这些熔岩进行古地磁研究，确定古地磁方向和古地磁绝对强度，并应用新型的微波古地磁强度法确定古地磁绝对强度。我们假设研究了至少50个独立的熔岩流，并与已有的数据一起构建了定义良好的全矢量长期变化曲线。该长期变化曲线可用于标定湖泊沉积物的半连续数据，以构建更高分辨率的复合长期变化曲线。这样的曲线作为地球动力学模型的观测输入数据是很受欢迎的。值得关注的时期还包括地磁拉尚事件和莫诺湖事件，迄今为止只在火山岩的少数地方发现了这些事件。

The ongoing volcanism within the Transmexican Volcanic Belt provides high-quality archives of the ancient earth's magnetic field, allowing for recovering directional variations as well as absolute palaeointensities. As there are not sufficient dated volcanoes for a detailed secular variation curce, we pretend first to select laca flows on the basis of geomorphological age estimations, from the age range 0-50 ka. These lava flows shall be dated by means of the 14C method, using charcoal produced directly by the volcanic eruptions. Palaeomagnetic studies of these lavas will be carried out to determine the paleodirections and absolute palaeointensities of the geomagnetic field, the latter also by application of the novel microwave paleointensity method. We pretend to study a minimum of 50 independent lava flows, to construct together with already available data as well-defined full-vector secular variation curve. This secular variation curve may be used to calibrate semi-continuous data obtained from lake sediments to construct compound secular variation curves of higher resolution. Such curves are much sougth after as observational input data for models of the geodynamo. The period under concern also includes the geomagnetic Laschamp and Mono Lake events, which have been found so far only in few places in volcanic rocks.