Decadal Geomagnetic Secular Variations From Greigite Bearing Dead Sea Sediments. (22nd April 2021)

• Record Type: Journal Article
• Authors: Ebert, Yael; Shaar, Ron; Stein, Mordechai
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 22:Number 4(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-04-22
• Subjects: Dead Sea -- greigite -- Levantine -- paleomagnetic directions -- secular variations -- sediments; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1029/2021GC009665
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: Archeomagnetic data from the Levant revealed periods within the Holocene with fast and extreme changes in the geomagnetic field. Yet, the availability of the archeomagnetic data is sporadic and the correlation with the available sedimentary records from the region is rather poor. To further explore decadal variations in the directions of the field, we investigate three outcrops of the late Holocene Dead Sea that are exposed along the western retreating shores of the modern lake. The sediments were deposited under spatially varying limnological‐environmental conditions, influencing their magnetic properties. The southern section, located near Ein‐Gedi Spa (EG section) is dominated by detrital titanomagnetite whereas the northern sections, Nahal Og (Og section) and Ein‐Feshkha (EF section), are dominated by authigenic greigite. The chronology of the sections was established by radiocarbon dating of short lived organic debris. The magnetic data were obtained in a 2 cm resolution. The EF section, spanning the time interval from ca. 2, 500 cal yr BP to ca. 1, 000 cal yr BP, is dominated by greigite and thus providing the most robust geomagnetic record with precise paleomagnetic directions. Greigite forms very early in the sediment and the effects of smoothing and the inclination shallowing are negligible. The new data reveal a maximal deviation of 20° from the geocentric axial dipole field between 2, 400 to 2, 200 cal yr BP accompanied with a fast swing in inclination from 60° to 35° over about a century. This suggests high geomagnetic field activity associated with the Levantine Iron Age geomagnetic anomaly. Key Points: Rock and paleomagnetic data at decadal resolution from three coeval radiocarbon‐dated late‐Holocene sections of the Dead Sea, Israel Paleomagnetic data from sediments with high greigite content are compatible with archeomagnetic data Smoothing and inclination shallowing of the paleomagnetic data carried by greigite are negligible