Geomagnetic polarity dating

This activity was intermittent and a hiatus is recognized from about 2 to 0.7 m.y.ago, which we have taken as the break between the eruption of the Early and Late Lavas of the Younger Volcanic Series.During this change the strength of the magnetic field weakened to 5% of its present strength.

Lavas of the Younger Volcanic Series were erupted from about 3.5 m.y. ago, flooding the denuded stumps of the shield volcano.The accumulated data set on polarity chronology from Nepal permits regional correlation of this sector with the Siwalik sections in India and Pakistan that have beenwell-dated through a combination of magnetostratigraphy and fission-track dating (see, for example, Keller 1990; see also reviews by Opdyke 1990 and Burbank 1996 and references therein).Owing to the absence of fossil- or isotope-constrained ages in the Siwaliks of Nepal, however, additional reversal records from the relatively thick ( 1-2 km) sections in its eastern and western parts are required in order to gain an accurate overall chronological insight into the sedimentation and tectonic history of the central part of the fold-and-thrust foreland belt of the Himalaya.Results of a geochronological and paleomagnetic investigation of the volcanic island of Mauritius are reported.Potassium-argon dates indicate that the main shield volcano was built subaerially between about 7.8 and 6.8 m.y. Some evidence is presented for caldera formation following the construction of the volcanic shield.

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