Laurentide rifting

Are we finishing the puzzle?

Over many years, there have been many theories about paleoreconstruction. Many geologists have come to believe that Laurentia broke away from the supercontinents of Rodinia and Pannotia in a 2-phase rifting event during the Neoproterozoic (900-544 Ma). As more studies have been made on different boundaries of Laurentia, more and more possibilities are ruled out, but more and more come into play. Among the most recent studies are Dalziel and Soper, who are trying to properly fit the Scottish Promontory into the puzzle, and Colpron, et al, who have put the first U-Pb zircon age constraints on the rifting of Laurentia.

Two possible scenarios (A, B) to account for two Neoproterozoic rifting events along western Laurentia(L). X and Y are unspecified crustal blocks that separated during the rifting events. Relative location of the Death Valley (DV),
 southern Canadian (SC) and Mackenzie Mountains (M) are shown (Colpron et al., 2002)   

Outline:

I. Introduction

II. Dalziel and Soper

III. Colpron, et al

IV. Summary

References:

Colpron, Maurice; James M. Logan, and James K Mortensen. Canadian Journal of Earth

Science. 39: 133-143 (2002).

Dalziel, I. W. D.; and N.J. Soper. Neoproterozoic extension on the Scottish Promontory

of Laurentia: Paleogeographic and tectonic implications. Journal of Geology.

109: 299-317. (2001).

Thomas, William A.; and Ricardo A. Astini. Journal of Geology. 109: 231-146 (2001).

Torsvik, T.H. et al. Continental break-up and collision in the Neoproterozoic and 
			Paleozoic – A tale of Baltica and Laurentia. Earth Science Reviews. 40: 229-258 (1996).