Low geomagnetic field strength during End-Cretaceous Deccan volcanism and whole mantle convection

Radhakrishna T,Asanulla R Mohamed,Soumya G S,Venkateshwarlu M

doi:10.1038/s41598-020-67245-6

Abstract

Knowledge about long-term variation of the geomagnetic dipole field remains in its nascent stage because of the paucity of reliable experimental data over geological periods. Here, we present the first robust experimental data from the largest Cretaceous flood basalt province on Earth, the ~65–66 Ma Deccan basalt within a thick (1250 m) unbiased stratigraphic section down to the basement, recovered from a drill hole of the Koyna Deep Scientific Drilling Project in the Western Ghats, India. Critical analysis of the result along with similar results of the Cretaceous age find that (i) the dipole moment during the end Cretaceous Deccan eruption is the lowest in whole of Cretaceous (ii) dipole moment at the onset/termination of the Cretaceous Normal Superchron is apparently lower relative to that in mid-superchron, however, such differences cannot be deciphered in shorter polarities probably because of insufficient time to develop recognizable variations (iii) inverse relation between dipole moment and reversal rate is lacking and (iv) a cause and effect relation between core-mantle boundary heat flux and low dipole moment that appears to be the principle governing factor in forming the Large Igneous Provinces on the surface of earth.

Highlights

Knowledge about long-term variation of the geomagnetic dipole field remains in its nascent stage because of the paucity of reliable experimental data over geological periods
The Mesozoic Dipole Low (MDL) was suggested to confine to the Jurassic Quiet Zone (~145– 165 Ma)[10], and some others extend it into early Cretaceous[11,12,13].The low field strength is variably described with respect to the Cretaceous Normal Superchron (CNS); some argue that the MDL extended into the CNS14,15, some others, mostly from China, report a low field at the onset of CNS16–18 and some works find it at the end of the CNS19–22
Using the remarkably well constrained Deccan palaeopole (37.8°N, 282.6°E)34, ~65 Ma palaeolatitude for the Koyna drill hole is estimated as 28.1°S to calculate the Virtual Dipole Moment (VDM),which is independent of the latitude

Summary

Introduction

Knowledge about long-term variation of the geomagnetic dipole field remains in its nascent stage because of the paucity of reliable experimental data over geological periods. We present the first robust experimental data from the largest Cretaceous flood basalt province on Earth, the ~65–66 Ma Deccan basalt within a thick (1250 m) unbiased stratigraphic section down to the basement, recovered from a drill hole of the Koyna Deep Scientific Drilling Project in the Western Ghats, India. In light of the ongoing hot debate and the large-scale geodynamic significance, we conducted a comprehensive PI study on one of the prominent surface manifestations of whole mantle convection, the Deccan flood basalt covering an unbiased stratigraphic section within a thick drill hole of the Continental Scientific Deep Drilling Project in the Koyna region of the Western Ghats, India (Fig. 1). We combine the results with other high quality Cretaceous global data and interpret in terms of relationships between geomagnetic behavior, polarity reversals and deep mantle processes

Methods

Results

Discussion

Conclusion