5. MAGNETOSTRATIGRAPHY OF PLIOCENE–PLEISTOCENE SEDIMENTS FROM THE EASTERN MEDITERRANEAN SEA1Carl Richter,2 Andrew P. Roberts,3 Joseph S. Stoner,4,6 L. David Benning,5 and Cung T. Chi2,7 |
ABSTRACTDetailed paleomagnetic investigations were conducted to develop a magnetostratigraphic framework for sedimentary sequences that were recovered by hydraulic piston coring in the Eastern Mediterranean Sea (Ocean Drilling Program Leg 160). A total of 1556 discrete samples from seven sites were subjected to detailed demagnetization, and high-resolution measurements of the magnetic properties of >100 m of sediments were made using "U-channel" samples (measurements at 1-cm intervals). The main magnetic carriers are probably an iron sulfide mineral and magnetite; occasional hematite were also present. Between 10% and 50% of the samples displayed erratic magnetic behavior and could not be used for magnetostratigraphic analysis. In addition, between 5% and 49% of the samples were completely overprinted by the coring process and had significantly higher paleomagnetic inclinations (>75°) than would be expected for an axial dipole field (inclinations of 49°-52°) at the site latitudes. Despite the coring-induced remagnetization and problems with the stability of magnetization, a sound magnetostratigraphic chronology was established at some sites. This chronology provides support for stratigraphic correlations within the basin and with onshore sequences as well as a temporal framework for paleoenvironmental studies that will enable assessment of the origin of organic-rich sapropel layers frequently found in the Mediterranean Sea and adjacent onshore sequences. |
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