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Connecting South America to the Global Miocene and the Deep Earth

Potter, Paul E.1 and Szatmari, Peter
1[email protected]

Many major landscape events occurred across South America and its offshore in the Miocene, especially in the Middle and Upper Miocene. These examples include all the continent-rejuvenation of the Andes and intense volcanism of the Altoplano/Puna (the second largest in the world), reversal of the Amazon and changes in course of the Orinoco with growth of their deep sea fans, deposition of thick foreland basins in Paraguay and northward along the eastern side of the Andes, retreat of a shallow sea in the Llanos, development of bordering deep sea unconformities, and heightened relief of South America’s passive margin with deposition of coastal gravels. Broadly comparable events also occurred world wide. These include:

Tectonics

  • The Alpine-Himalaya and Circum-Pacific orogenic belts were both active with rejuvenation of old mountains and formation of new ones along with widespread epeirogenic rejuvenation
  • Spreading rates of mid-ocean ridges increased
  • Many transform faults were active
  • The Japanese Archipelago assumed its present form at 14 Ma
  • Throughout much of the Middle and Upper Miocene the Isthmus of Panama was closing
  • Volcanism along ridges, at ocean-continent margins, and within plates was enhanced
  • Oceans and Atmosphere

  • Long term opening and closing of seven key gateways cooled the temperature of the ocean and atmosphere starting at 14 Ma
  • The present global oceanic circulation system also largely dates from this time
  • Rejuvenated Himalayas and Tibetan Plateau deflected the jet stream to their south side at about 8 Ma and thus increased their erosion rates
  • Leading to new alluvial plains, deltas, and deep sea fans off shore
  • Carbonate production was interrupted or shifted
  • On land

  • Shore lines prograde on many passive margins
  • Some pre-existing basins were inverted and eroded, but many new ones formed plus some deepened entered the oil window for the first time
  • Heightened continental relief enhanced global aridification
  • Major shifts in flora and fauna and beginnings of early man
  • All these diverse global changes in the atmosphere, oceans, and continents occurred in only 11 Ma and thus point to a single deep earth cause. We summarize in a flow diagram how major earth surface processes are related to each other and the deep Earth. Central to this idea is the concept of "dynamic topography", which relates major earth features to seismological inferred changes in density or chemistry of the mantle

     

    AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013