Abstract
In northern Sonora two belts of Precambrian rocks are exposed, the youngest rocks are towards the east (l,600-1,700 m. y.), in northwestern Sonora the older rocks are exposed (1,700-1,800 m.y.). The main lithologies are schists, quartzites, gneisses and calcalkaline intrusives. These rocks have suffered a complex history of deformation, metamorphism and intrusion. These metamorphic rocks were unconformably covered by marine sedimentary carbonates at the end of the Precambrian. Cambrian rocks are concordant with the sedimentary Precambrian rocks. The more common lithologies among the Paleozoic rocks are limestones, sandstones and shales. The outcrops of the Paleozoic rocks are isolated in northern and central Sonora. The prevailing structural direction of the Paleozoic rocks is NW to NS. In the Mesozoic, during Late Triasstc thick sequences of clastics with coal lenses were deposited, they unconformably rest on Paleozoic rocks. In order to continue, download the full paper in PDF.
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