The Mesozoic Era – age of reptiles
The Mesozoic began after the End-Permian mass extinction, 251 Mya, and ended in the less catastrophic but better-known Cretaceous-Tertiary (“K-T”) mass
The Mesozoic Era – age of reptiles
The Mesozoic began after the End-Permian mass extinction, 251 Mya, and ended in the less catastrophic but better-known Cretaceous-Tertiary (“K-T”) mass extinction, 65 Mya. Like the Paleozoic, it is subdivided into periods:
- the Triassic (251-200 Mya),
- the Jurassic (200-145 Mya) and
- the Cretaceous (145-65 Mya).
As life in the Mesozoic was dominated by reptiles, including dinosaurs, it is often called the “Age of Reptiles”.
As the Mesozoic opened, there was only one continent, Pangea. Pangea did not just form and then sit stationary for millions of years; tectonic activity continued throughout the era. Evidence from fossils (types of organisms) and sedimentary rocks (formation from sand dunes) indicate that the interior of Pangea was quite arid.
As plates shifted, rifts developed and sea water periodically spilled into the rifts. In between periods of flooding, evaporating water left behind salts (evaporites). Measurement of the ages of these salts gives geologists a calendar of the opening of the rifts and therefore the development of the inter-continental oceans.
The main geological event of the Mesozoic was the breakup of Pangea into seven major continents. Around the end of the Triassic, around 175 Mya, Laurentia rifted and what would become the North Atlantic opened up. As the Tethys Sea penetrated into the flank of Pangea from the east, the two seas joined and split the supercontinent into its two major components, Laurentia1Or Laurasia. in the north and Gondwanaland in the south. A huge mountain chain which had stretched diagonally across the great continent left its remains in the Appalachians of North America and the mountains of Ireland, northern Scotland and western Scandinavia. Around the end of the Jurassic, 50 million years later, Gondwanaland rifted and South America and Africa began to separate, the South Atlantic Ocean ope