Paleo- ja mesoproterotsooisten supermannerten kehitys paleomagneettisten tulosten perusteella.

Various geological and geophysical evidence show that at least two supercontinents, Columbia and Rodinia, existed during the Paleoproterozoic and Mesoproterozoic eras. In this study, updated paleomagnetic and isotope age data has been used to define the amalgamation and break-up times of these supercontinents. Before putting the ancient continents to a supercontinent assembly, we have tested the validity of the geocentric axial dipole model (GAD) of the Paleo-Mesoproterozoic geomagnetic field. The tests yield support to the GAD-model, but do not rule out a ca. 10% non-dipole (octupole) field. In the whole of Proterozoic, Columbia and Rodinia were predominantly in moderate to low paleolatitudes. In the Paleoproterozoic, unexpected low-latitude glaciations took place in several continents. The pre-Columbia orogenies were caused by a complex set of collisions, rotations and transform or strike slip faultings that caused the orogenic belts to appear obliquely. However, no prominent difference was observed between paleomagnetically derived and recent geologic models of Columbia. The final amalgamation of Columbia didn’t happen until ca. 1.53 Ga. Columbia broke up at ca. 1.18 Ga during several rifting episodes, followed by a short period of independent drift of most continents. The amalgamation of Rodinia took place at 1.10 - 1.04 Ga.