FLOW DIAGRAM RELATING MAJOR SURFACE PROCESSES TO THE DEEP EARTH - INSIGHTS FROM THE MIOCENE

Many tectonic, oceanic and climate changes of global scale began in the Tertiary and changed the world. In full flower by the beginning of the Middle Miocene around 16 Ma, these continued through the Late Miocene into the present. Hence most of our modern world, continental glaciations excepted, is traceable back to the Middle and Late Miocene.

Two global orogenies dominated this 11 Ma interval. One extends from Gibraltar across southern Asia into Vietnam and the other around the Pacific Rim. Two super plumes, one under Africa and the other under the South Pacific, powered these global orogenies. Because they are closely synchronous, they had enormous consequences for the earth’s surface, and because they are close to us in time, both are easy to study and sample. Thus the Miocene is ideal to study for its many global intra connections and their link to the Deep Earth.

As these two orogenies developed with both new and rejuvenated mountains and interior and passive margin plateaus, a global warm water ocean became more fragmented and cooler – globally seven gateways opened and closed. These orogenies also deflected jet streams, expanded rain shadows and desertification, and helped cool air temperatures. Upwelling developed on both sides of the Pacific basin, silica production shifted from the Atlantic to the Pacific and Indian Oceans, more mud and sand were brought to the ocean causing many passive margins to prograde, and hemi pelagic mud became more abundant off continental margins. At the very end of the Miocene even the Mediterranean dried up, isolated by the Alpine orogeny. Active convergent margins changed continental tilts, completely altered some rivers and formed new ones with new deltas, some on the other sides of continents. The above changes greatly modified the surface environment and induced many significant changes in flora and fauna, and altered geochemical parameters. Global tectonics is the underlying driving force of all the above. A flow diagram shows how the major earth surface process active in the Miocene are related to the Deep Earth as understood by recent advances in seismological tomography. We posit that the generalizations ultimately emerging from the Miocene apply to all the Phanerozoic and farther back in time.