The Devonian in Northwest region, Mexico

Paleontology and geology

In the Devonian, the northern part of this region was near the edge of the continent, and shallow to deep seas of the continental shelf, slope, and basin extended south and west. The volcanic islands that would form part of this region were approaching the area, while other parts had not formed yet. The limestones, sandstones, and shales deposited in the seas contain fossils of the many animals that lived here, including corals, brachiopods, radiolarians, sponges, and conodonts. Most of the Devonian rocks have been removed by erosion or are buried below the surface, but a few small exposures can be found in the north and west. They are too small to appear on this map, but may be included in the undifferentiated Paleozoic rocks. Other more detailed maps may also show them. Some rocks in the north may have been deposited elsewhere and later moved to their present location. Geologists continue to study how and when they formed.