Episodic Tectonics in the Phanerozoic Succession of the North American Arctic and the “10 Million Year Flood”

Ashton Embry

Detailed stratigraphic studies in the basins of the North American (NA) Arctic have revealed the presence of 56, large magnitude, sequence boundaries within the Phanerozoic succession. The sequence boundary characteristics indicate that the boundaries were generated primarily by tectonics. Each sequence boundary is interpreted to have been produced by a tectonic episode which affected the entire region and which resulted in tectonic uplift and erosion on the margins of the basins. The sequence boundaries have been assigned a numerical age and the time intervals between the boundaries were no less than 5 and no more than 15 million years in almost all cases. It is clear that the tectonically generated boundaries were chaotic and had a relatively high chance of reoccurring within 10 million years. The major transgression which follows each boundary could perhaps be referred to as a “10 million year flood”. The tectonic episodes which generated the sequence boundaries lasted for a few million years and were separated by longer intervals of relative tectonic quiescence. The tectonic episodes are interpreted as an expression of relatively rapid and substantial changes in the stress fields of the NA Arctic. Such stress changes would be possibly due to somewhat abrupt changes in the speed and/or direction of plate movements which affected the NA Arctic. Given there is a complex feedback between plate distribution and dynamics with mantle convection and heat release, the recognized tectonic episodes may reflect perturbations in mantle convection intermittently occurring every 5 -15 million years due to a gradual buildup of, and a consequent episodic release of, stress and heat. There are indications that the recognized tectonic episodes affected basins throughout the world. A literature survey has indicated most of the tectonic sequence boundaries we have recognized are present in basins on different continents. Furthermore, many of the tectonic episodes correlate with significant carbon isotope excursions and with mass extinctions. Given that all the tectonic plates are linked and a mantle-driven, major adjustment in the speed or direction of one plate would require compensatory movement changes in all the other plates, a phenomenon of episodic global tectonics occurring with a frequency of 5 -15 million years is a theoretical possibility. These results have implications for petroleum exploration in that petroleum traps would have been formed, altered and sometimes breeched during the tectonic episodes. Also, the movement of subsurface fluids would have been greatly influenced by such intermittent convulsions of the sedimentary column. Finally, the recognition and dating of these tectonically-generated sequence boundaries, in combination with their potential global distribution, allows their occurrence to be predicted in unexplored sedimentary basins.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013