Lesson 8 notes

  • Mesozoic Earth: Key Concepts

    • Introduction to Mesozoic Tectonics

      • Understanding the positions of land masses during the Mesozoic era is critical—for example, continental corridors and barriers significantly impacted the ecology and evolution of fauna and flora.

    • Paleogeographic Changes: The supercontinent Pangea was intact during the Early Triassic and fragmented into distinct continents by the Late Cretaceous.

      • British Columbia experienced substantial geological changes during this period.

    • Global Mesozoic Paleogeography

    • At the start of the Mesozoic, all continents formed Pangea, surrounded by the Panthalassic Ocean and Tethys Ocean.

    • The fragmentation of Pangea shaped oceanic climate systems throughout the Mesozoic.

    • Continental Drift

    • Late Triassic Phase: Pangea began to unzip, forming Gondwana (south) and Laurasia (north), with the Tethys Ocean dividing it.

    • By the Late Triassic, North America and Africa were starting to separate.

    • Modern Analogies

    • The East African Rift System illustrates how rifting may have appeared in Late Triassic with similar geological processes occurring in the Red Sea.

    • Separation of continents continued, with Antarctica, Australia, and India moving away from Gondwana.

    • Hispanic Corridor

    • The corridor, a seaway between North and South America, existed for millions of years prior to the formation of the Isthmus of Panama.

    • Fossil evidence suggests it might have opened during the latest Triassic or early Jurassic using bivalves and ammonites as indicators.

    • Jurassic Period Developments

    • South America and Africa's rifting sparked the formation of the South Atlantic Ocean.

    • The Tethys Ocean began to close as Laurasia and Africa drifted.

    • Exotic Terranes of North America

    • Initially a passive margin, the west coast of North America underwent tectonic changes, accumulating exotic terranes that shaped its current geology.

    • Exotic Terrane Defined: A crustal fragment formed on one tectonic plate and accreted onto another, each having distinct geological histories.

    • Mountain Building in the Mesozoic

    • Mountain ranges, such as Coast Mountains and Rockies, were influenced by volcanic activity and crustal compression due to plate tectonics.

      • Volcanic Activity led to formation of Coast Mountains via subduction creating a magmatic arc.

      • Compression created the Rocky Mountains with significant crustal shortening and faulting.

    • Cretaceous Seaway

    • Formed due to subsidence created by the weight of the Rockies; served as an inland sea dividing North America, impacting Mesozoic biodiversity.

    • Eventually disappeared due to tectonic shifts and compression ceasing, altering habitats significantly for terrestrial dinosaurs.

    • Fossil Records in Alberta

    • Cretaceous factors: Fertile landscapes supported diverse dinosaur fauna, while modern arid conditions expose old rocks for fossil discovery.

    • Badlands of Alberta primarily contain Late Cretaceous rocks, including a mixture of terrestrial and marine fossils due to historical seaway presence.

    • Conclusion

    • Mesozoic tectonics greatly influenced geological facets of Western North America, emphasizing plate movements' significant impact on regional geology and life forms.