Polar forests of the Cretaceous Polar forests of the Cretaceous Cretaceous polar forests were temperate forests that grew at polar latitudes during the final period of the Mesozoic Era, known as the Cretaceous Period 145–66 Ma. During this period, global average temperature was about higher and carbon dioxide (CO) levels were approximately 1000 parts per million (ppm), 2.5 times the current concentration in Earth's atmosphere. The abundance of atmospheric carbon dioxide had a very significant impact on global climate and Earth's natural systems as its concentration is considered one of the main factors in the development of a pronounced greenhouse Earth during the Cretaceous with
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