Paleomagnetic analysed of two sediment cores off Cape Ghir


Holocene records documenting variations in direction and intensity of the geomagnetic field during the last about seven and a half millennia are presented for Northwest Africa. High resolution paleomagnetic analyses of two marine sediment sequences recovered from around 900 meter water depth on the upper continental slope off Cape Ghir (30°51'N, 10°16'W) were supplemented by magnetic measurements characterizing composition, concentration, grain size and coercivity of the magnetic mineral assemblage. Age control for the high sedimentation rate deposits (~60 cm/kyr) was established by AMS radiocarbon dates. The natural remanent magnetization (NRM) is very predominantly carried by a fine grained, mostly single domain (titano-)magnetite fraction allowing the reliable definition of stable NRM inclinations and declinations from alternating field demagnetization and principal component analysis. Predictions of the Korte and Constable (2005) geomagnetic field model CALS7K.2 for the study area are in fair agreement with the Holocene directional records for the most parts, yet noticeable differences exist in some intervals. The magnetic mineral inventory of the sediments reveals various climate controlled variations, specifically in concentration and grain size. A very strong impact had the mid-Holocene environmental change from humid to arid conditions on the African continent which also clearly affects relative paleointensity (RPI) estimates based on different remanence normalizers. To overcome this problem the pseudo-Thellier RPI technique has been applied. The results represent the first Holocene record of Earth's magnetic field intensity variations in the NW Africa region. It displays long term trends similar to those of model predictions, but also conspicuous millennium scale differences.

Supplement to: Bleil, Ulrich; Dillon, Melanie (2008): Holocene Earth's magnetic field variations recorded in marine sediments of the NW African continental margin. Studia Geophysica et Geodaetica, 52(2), 133-155

Related Identifier IsSupplementTo
Metadata Access
Creator Bleil, Ulrich; Dillon, Melanie
Publisher PANGAEA
Publication Year 2010
Rights Creative Commons Attribution 3.0 Unported;
OpenAccess true
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 10 datasets
Discipline Earth System Research
Spatial Coverage (-10.268W, 30.848S, -10.268E, 30.850N); off Northwest Africa
Temporal Coverage Begin 1999-10-18T15:50:00Z
Temporal Coverage End 2003-05-16T20:53:00Z