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Neoproterozoic glacial origin of the Great Unconformity.

  • Author(s): Keller, C Brenhin
  • Husson, Jon M
  • Mitchell, Ross N
  • Bottke, William F
  • Gernon, Thomas M
  • Boehnke, Patrick
  • Bell, Elizabeth A
  • Swanson-Hysell, Nicholas L
  • Peters, Shanan E
  • et al.
Abstract

The Great Unconformity, a profound gap in Earth's stratigraphic record often evident below the base of the Cambrian system, has remained among the most enigmatic field observations in Earth science for over a century. While long associated directly or indirectly with the occurrence of the earliest complex animal fossils, a conclusive explanation for the formation and global extent of the Great Unconformity has remained elusive. Here we show that the Great Unconformity is associated with a set of large global oxygen and hafnium isotope excursions in magmatic zircon that suggest a late Neoproterozoic crustal erosion and sediment subduction event of unprecedented scale. These excursions, the Great Unconformity, preservational irregularities in the terrestrial bolide impact record, and the first-order pattern of Phanerozoic sedimentation can together be explained by spatially heterogeneous Neoproterozoic glacial erosion totaling a global average of 3-5 vertical kilometers, along with the subsequent thermal and isostatic consequences of this erosion for global continental freeboard.

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