In these cross sections we compare the differences between the northwest and the southwest part of the continental margin. Along the northwest part of the margin (W NV), we see the red Sonoma terrane accreted to NA and the fold and thrust belt active further inland. At the same time (moving horizontally across the figure), the SE part of the margin has experienced rifting or a transform fault that has juxtaposed the thick Precambrian crust (white) covered with thin passive margin sediments against thin oceanic crust. -----------------------------------------Later in time we see in the NW that the polarity of subduction switched from west dipping to east dipping, effectively changing the plate margin from a ‘South-Pacific’ style margin to a ‘Andean’ style margin. As well, in the backarc environment, there is extension and deposition in the West Nevada Triassic basin. Along the SW portion of the plate margin, east dipping subduction is also active, but because the continental crust is dominantly thick, buoyant pC crust, there is no back-arc extension (as in the case in W NV) and instead, there are structures indicative of compression.
Created with Web Album Generator