• Paleointensity of the Earth's magnetic field at ${\sim}$117 Ma determined from the Rajmahal and Sylhet Trap Basalts, India

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    • Keywords


      Paleointensity; IZZI protocol; early Cretaceous; Rajmahal–Sylhet Traps; India.

    • Abstract


      We present here the paleointensity results of basalt samples from Rajmahal (25.10$^{\circ}$N; 87.40$^{\circ}$E) and Sylhet Traps (25.22$^{\circ}$N; 91.71$^{\circ}$E) of eastern India (${\sim}$117 Ma) to know the strength of the earth's magnetic field during the early Cretaceous from these locations. The modified version of the Thellier–Thellier paleointensity method of, in field-zero field-zero field-in field (IZZI) protocol and systematic partial thermoremanent magnetization (pTRM) checks were used for the paleointensity determination. Rock magnetic investigations on these rocks indicate ‘magnetite’ is the main remanence carrier with single domain (SD) to pseudosingle domain (PSD) nature. The samples have yielded low paleofield intensities between 6.97 $\pm$ 2.21 and 23.47 $\pm$ 2.08 $\mu$T (mean 17.20 $\pm$ 1.89 $\mu$T). The corresponding virtual dipole moment (VDM) ranges from 1.16 to 4.17 $\times$ 10$^{22}$ Am$^{2}$ (mean 2.93 $\times$ 10$^{22}$ Am$^{2}$) which is approximated as to 30% of the present-day field strength (8 $\times$ 10$^{22}$ Am$^{2}$). The success rate of the experiment is quite low in the order of 5%, but has provided scope for further, more elaborative paleointensity studies. Our new results compared with published paleointensities from these basalts as well as rocks of Cretaceous normal superchron (CNS) time around the globe are in good agreement.

    • Author Affiliations



      1. CSIR-National Geophysical Research Institute, Hyderabad, India.
    • Dates

  • Journal of Earth System Science | News

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      Posted on July 25, 2019

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