Geomagnetism and Paleomagnetism/Marine Geology and Geophysics
The Ionian Sea: The oldest in situ ocean fragment of the world?
Article first published online: 11 DEC 2012
©2012. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 117, Issue B12, December 2012
How to Cite
2012), The Ionian Sea: The oldest in situ ocean fragment of the world?, J. Geophys. Res., 117, B12101, doi:10.1029/2012JB009475., , , and (
- Issue published online: 11 DEC 2012
- Article first published online: 11 DEC 2012
- Manuscript Accepted: 11 OCT 2012
- Manuscript Revised: 14 SEP 2012
- Manuscript Received: 22 MAY 2012
- Ionian Sea;
- magnetic anomalies;
- magnetic modelling;
- oceanic crust
 It is well known that the Ionian Sea is characterized by thin (8–11 km) crystalline crust, thick (5–7 km) sedimentary cover, and low heat flow, typical for a Mesozoic (at least) basin. Yet seismic data have not yielded univocal interpretations, and a debate has developed on the oceanic versus “thinned continental” nature of the Ionian basin. Here we analyze the magnetic anomaly pattern of the Ionian Sea and compare it to synthetic fields produced by a geopotential field generator, considering realistic crust geometry. The Ionian basin is mostly characterized by slightly negative magnetic residuals and by a prominent positive (150 nT at sea level) “B” anomaly at the northwestern basin margin. We first test continental crust models, considering a homogeneous crystalline crust with K = 1 × 10−3, then a 5 km thick deep crustal layer of serpentinite (K = 1 × 10−1). The first model yields insignificant anomalies, while the second gives an anomaly pattern anticorrelated with the observed residuals. We subsequently test oceanic crust models, considering a 2 km thick 2A basaltic layer with K = 5 × 10−3, magnetic remanence of 5 A/m, and a unique magnetic polarity (no typical oceanic magnetic anomaly stripes are apparent in the observed data set). Magnetic remanence directions were derived from Pangean-African paleopoles in the 290–190 Ma age window. Only reverse polarity models reproduce the B anomaly, and among them the 220–230 Ma models best approximate magnetic features observed on the abyssal plain and at the western basin boundary. The Ionian Sea turns out to be the oldest preserved oceanic floor known so far.