Magnetostratigraphy of U-Pb–dated boreholes in Svalbard, Norway, implies that magnetochron M0r (a proposed Barremian-Aptian boundary marker) begins at 121.2 ± 0.4 Ma

Abstract The age of the beginning magnetic polarity Chron M0r, a proposed marker for base Aptian Stage, is disputed due to divergence published radioisotopic dates and ambiguities in stratigraphic correlation sections. Our magnetostratigraphy core DH1 from Svalbard, Norway, calibrates bentonite bed, dated by U-Pb methods 123.1 ± 0.3 Ma, uppermost part magnetozone M1r, which ∼1.9 m.y. before M0r. This first direct calibration any high-precision date chron M sequence. interpolated 121.2 0.4 Ma M0r younger ∼5 than its estimated used Geologic Time Scale 2012, had been extrapolated on oceanic basalts cyclostratigraphy. adjusted model implies commensurate faster average global spreading rate ∼12% during Aptian–Santonian interval. Future dating high-resolution cyclostratigraphy are needed investigate where expand mid-Jurassic earliest Cretaceous interval required ∼4