Full vector geomagnetic ?field record of 28 lava flows from El Hierro, Canary Islands, Spain

by J.P. van Galen

Institution: Universiteit Utrecht
Year: 2015
Keywords: Paleomagnetism, Paleointensities, Rockmagnetims, Paleodirections, Brunhes
Record ID: 1266675
Full text PDF: http://dspace.library.uu.nl:8080/handle/1874/305363


Direct observations on the Earth's magnetic field have only been done during the last 170 years, finding a gradual decline over this period. Attempts to increase the temporal and spatial constraints for the paleofield are made by looking at archaeological sites. Models based on these sites give spatially limited insight in the behavior of the field in the last 7 kyr. In order to obtain global paleointensity coverage new and improved methods have been conducted on volcanic islands predominantly on the northern hemisphere. Here, paleodirections were obtained from lavas flows El Hierro, Canary Islands, Spain. In addition, three different intensity methods were used to obtain information about the full-vector field. An age model was created (middle to late Brunhes 466 - 135 ka) based on a stratigraphic and directional coherency with a dated section 4 km northwest. The directions in this study and in the published section 4 km northwest deviate east around ~13°. These eastern directions in both studies are attributed to unrepresentative sampling to properly depict paleosecular variation. Thellier-Thellier, the recently proposed multi-speciment parallel differential pTRM method combined with the ARM-test, and the very recent Pseudo-Thellier approach are here thoroughly reviewed on success rate, workload and results. A paleointensity trend is suggested with intensities often ~15 µT lower than the current intensity for El Hierro (~ 39 µT), showing only three phases of intensities equal or close to present day values.