THE DAWN OF LIFE ON EARTH: COMBINED RESULT OF SUPERCONTINENTAL MANTLE INSULATION AND A MEGA-ASTEROID IMPACT

M. DOBLAS¹, N. YOUBI², M. BEN ABBOU³ & H. EL HACHIMI²

¹IGEO, Facultad de Medicina, CSIC-UCM, Spain, doblas@mncn.cisc.es; ²Cadi Ayyad University, Marrakesh, Morocco; ⁴Sidi Mohamed Ben Abdellah University, Faculty of Sciences Dhar-Mehraz, Fes, Morocco.

        We contend that planet-wide mantle insulation by the Pannotian supercontinental cap during the Precambrian/Cambrian transition (reinforced by the prevailing "Snowball Earth" ice-sheet) led to widespread magmatic underplating and subsequent generalized worldwide volcanic activity (e.g. Central Iapetus “Large Igneous Provinces”, LIP). Combined with this terrestrial evolution, we suggest that by the same time a gigantic extraterrestrial asteroid impacted on the center of this supercontinent. These two major events definitely drove the Phanerozoic evolution of the Earth. They contributed to melt the "Snowball Earth" ices terminating the last Precambrian glaciation, accompanied by: gigantic radial dike swarms and massive magmatism; breakup of Pannotia through a series of radial and concentric rifts; a generalized elevation of the sea-level; a noticeable increase of the oceanic P; massive CO2 outgassing; a dramatic greenhouse event that drastically changed the whole picture of our planet, in particular its biotic evolution. This marked the beginning of the Phanerozoic cycle and created the necessary conditions for the Dawn of Life on Earth.

According to our dual model, the geological evolution of the Earth´s lithosphere/mantle couple was one of the key factors directly responsible for the flourishment and development of our planet unique biological diversity.

A dramatic consequence of the major asteroid catastrophe involved the rebound of the terrestrial core triggering in the antipodes (the impact site in protoAfrica and the Panthalassan ocean/protoPacific neo-ocean). These dual upwellings began to pulsate as a consequence of an impact-induced “core rebounding ball, CRB” scenario, triggering a series of antipodal LIPs episodically at the same places on Earth, usually accompanied by mass biotic extinction or upheaval events : the late Neoproterozoic-Cambrian Central Iapetus Magmatic Province (CIMP) and the protopacific superoceanic swelling, the Permo-Carboniferous Eastern European Northwestern African magmatic Province (EUNWA) and the Panthalassian superplume, the Triassic/Jurassic Central Atlantic Magmatic Province (CAMP) and the central Pacific superswell, the Cretaceous Peri-Atlantic Alkaline Province (PAAP) and the central Pacific superplume, the Cenozoic African superswell and the Ontong/Java oceanic plateau. These magmatic superpulses were accompanied by episodic tectonic cycles involving downwelling-induced supercontinental amalgamation and upwelling-induced supercontinental fragmentation, thus giving rise to the different Phanerozoic Pangeas. In fact, our model implies a complete revision of the presently accepted global geodynamic concepts in that plate/plume movements would be driven by a long-lived “core rebounding ball (CRB)” scenario.

REFERENCE: Doblas, M., Youbi, N., Ben-Abbou, M., López-Ruiz, J. & El-Hachimi, H., 2007. Mantle insulation and the Dawn of Life on Earth. 5th International Geological Correlation Programme Conference (IGCP 485/497), November 28 - December 5, El Jadida, Morocco, p.28.