Palaeomagnetism and Palaeogeography

Palaeomagnetism, the study of fossil magnetisations in ancient rocks, is the only method for quantitatively formulating and verifying pre-Mesozoic continental reconstructions.

The direction of the ancient geomagnetic field, recorded during cooling in igneous and metamorphic rocks, or during deposition in sedimentary rocks, reveals the latitude and orientation of a continental block with respect to the ancient palaeomagnetic pole (palaeopole). Comparison of paleopoles and Apparent Polar Wander Paths (APWPs) from different continents enables their ancient positions, relative to the paleopole and to each other, to be determined, and reconstructions can then be checked and improved using palaeontological, geochronological, structural and other data.

Our current research is focused on the Neoproterozoic (ca. 1000 - 540 Ma) palaeogeography. There were several major glaciations during this time interval. There is a strange and important feature about these glaciations - their tracks are often found in the continents located in the equatorial palaeolatitudes. This discovery gave a rise for several interesting theories of the Precambrian climate, including the Snowball Earth hypothesis. The only way to check these theories is to recover the detailed history of the plate tectonic movement (“continental drift”) between 1000 and 540 Ma.

The present palaeomagnetic database is yet unable to produce such an unequivocal drift record- data are too fragmented and often poorly dated. Few alternative palaeogeographic models exist only for some limited time intervals. Our main aim is to improve this situation by the study of several key Neoproterozoic rock formations all over the world (in Africa, Australia, North and South America, Europe, India, and Siberia). These new palaeomagnetic data will be complimented by geochronology and stable isotope studies. The expected result is an animated global plate tectonic history supplemented by the first-order palaeoclimatic reconstructions.



Dr. Jenny A. Tait