A new Late Carboniferous Pangea reconstruction

Abstract:

Paleomagnetically reconstructed Laurasia and Gondwana are well satisfied. However, the Pangea reconstruction remains controversial. The Late Triassic-Early Jurassic reconstruction, Pangea A, is consistent with one derived by closure of the Atlantic Ocean. As going back to older Period, the Pangea A reconstruction cannot stand. Particularly, the Late Carboniferous and Permian reconstruction, Pangea B, placed Gondwana ~3500 km eastward relative to its Pangea A configuration. This might indicate that the super continent was tectonically evolving during the period. For instance, an intra Pangean megashear zone has been proposed to show the evolution from Pangea B to Pangea A. On the other hand, researchers suspected that the Pangea B reconstruction is not accurate, because of several factors, i.e., the effect of persistent, large non-dipole field, remagnetization, errors in paleomagnetic record (inclination shallowing), and so on.

To test the effect of inclination shallowing on the Pangea reconstruction, we here focus on the Late Carboniferous time, because, the Laurasian poles are mainly from volcanic rocks, and the Gondwana poles dominantly from sediments. This makes the test rather simple. Assuming a flattening factor of 0.5, we corrected the paleomagnetic inclinations of the Late Carboniferous results from Gondwana, and the inclination-corrected poles are thus achieved. The mean Laurasia and Gondwana poles can largely be accommodated by closure of the Atlantic Ocean, and the remaining offset may be solved by a ~15 degree relative rotation between the two continents. Relative rotation is often observed during continental collision (e.g., the collision between the North and South China blocks, the India-Asia collision, and so on), and more likely than the large scale shear. Our test indicates that Pangea B is probably the artifact of paleomagnetic inclination shallowing in sedimentary rocks.