Triassic plants and Pangea

Abstract

Comparison between conclusions of Palaeobotany and plate tectonics covering the position of Mesozoic continents shows some disagreements. Existing palaeomagnetic reconstructions differ from one another as well as from the picture received on the basis of Palaeobotany. Various palaeomagnetic reconstructions for the Permian and Triassic differ from one another in showing less or more compact Pangea, different width of Tethys Ocean and in the form of relative position of Cathaysia. There are also contradiction between palaeomagnetic reconstructions and palaeontological data.

Palaeobotanical investigations show that in the end of Palaeozoic there were four first order phytochoria in Eurasia with very different composition of floras which suggest high isolation of these phytochoria. In the beginning of Triassic former isolation of floras of different areas disappeared. The floras of Europe, China and Indochina and also North America became quite similar. At this time a new united Laurasian Kingdom had originated.

Distribution of plants in the Mesozoic Era suggests the existence of united continent- Laurasia. The separation of North America from Laurasia took place after Triassic. Nevertheless, united Eurasia existed from the Triassic till now.

Palaeomagnetic reconstructions for the Mesozoic do not reflect changes in the distribution of plants and animals as we see from Triassic. From this point of view all reconstructions showing isolated plates (similar to Paleozoic ones) in the Mesozoic, instead of united Eurasia and the reconstructions showing isolation of Cathaysia from other Eurasia are doubtful. Similarly, the gradual union of isolated plates to united Eurasia during Mesozoic and Cenozoic also seems doubtful.