Ancient sediments give new understanding of geomagenetic field
The aim of the PALEOCLAK (Paleomagnetic applications for dating and identifying Holocene climate variability in southwestern Europe and Azores Islands as recorded by lake sediments) project was to advance the use of paleomagnetic and environmental magnetic techniques. New reliable data is crucial to achieving a detailed reconstruction of the Earth’s magnetic field. Therefore, PALEOCLAK developed a paleomagnetic dating technique based on the recognition of changes in the direction and intensity of the Earth’s magnetic field in the sedimentary record. The main result was the establishment of a new regional European geomagnetic field intensity model for the last millennia, which provided an improved reconstruction of past geomagnetic field intensity fluctuations. The study also demonstrated the need to establish a pre-selection of high-quality data to obtain an accurate description of the geomagnetic field in the past. New environmental magnetic datasets were obtained from different lake sediments from the Iberian Peninsula and Azores Islands. The data was used to identify paleoenvironmental variations in the type, concentration and grain size of magnetic minerals. By comparing magnetic parameters with other available sedimentological, geochemical and biological data, scientists were able to evaluate the reliability of magnetic parameters as proxies for Holocene climate variability and human activity. An environmental magnetic study was carried out on a Late Pleistocene-Holocene sediment core from Lake Sanabria and from different rocks of its catchment in north-west Spain. This provided new insights into the evolution of the climate of the north-west Iberian Peninsula during the last deglaciation. A sharp change in magnetic properties was observed in lake sediments between 13 and 12.6 thousand years Before Present (BP), together with more subtle changes in rock magnetic data around 14 thousand years BP. This supported the idea of rapid glaciation of the catchment of Lake Sanabria inferred from previous studies of its sediments, geochemistry and geomorphology. New reliable data is crucial to achieving a detailed reconstruction of the Earth’s magnetic field. The paleomagnetic dating technique developed by PALEOCLAK will therefore enable accurate high-resolution age models to be developed, in which paleoenvironmental responses to climatic and anthropogenic impacts can be properly determined.
Keywords
Lake deposits, Holocene, PALEOCLAK, geomagnetic, paleomagnetic, sedimentary record, geomagnetic field intensity model, proxies, Lake Sanabria, geochemistry, geomorphology
