Phanerozoic the Mesozoic features the rise of reptiles on their 150 million year conquest of the Earth on the land, in the seas, and in the air. There are three periods in the Mesozoic: Triassic, Jurassic, and Cretaceous. The Triassic ranges from 250 million to 200 million years ago. The Triassic is a transitional time in Earth's history between the Permian Extinction and the lush Jurassic Period. It has three major epochs: Early Triassic, Middle Triassic and Late Triassic. The Early Triassic lasted between 250 million to 247 million years ago, and was dominated by deserts as Pangaea had not yet
Swithland Wood and The Brand high mountain range, the processes of erosion began. By the Triassic Period, (240 million years ago) the mountains were eroded down to something like their current height. There then began a new deposition, this time of desert sand and fine dust, that produced a new layer of soft red marl, creating the gentler rolling appearance of the land, with just the tips of the older rocks reaching the surface. Over most of Swithland Wood the marl is the surface rock type (although the slate beds will occur underneath that). Finally, during the ice age, glacial erosion stripped back the Triassic