User:RudiBosbouer/sandbox
Geology
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History
[edit]The foundations of the Fish River Canyon were laid between 3,600 and 2,000 million years ago when the Congo and Kalahari Craton Cratons were formed. Millions of years’ of volcanic activity and massive amounts of erosion material from these Cratons deposited material into a shallow sea which was formed about 1,700 million years ago. Extreme heat and preasure changed this deposited material as well as marine sediments into gneisses and granites which was the beginning of the Namaqualand Metamorphic Complex.
Approximately 1,200 million years ago, continental drift caused the Namaqualand Mountain Building event to take place, folding huge mountains in the area. Today the remnants of these mountains are still visible at Ai-Ais.
Thereafter numerous intrusions interspersed the Namaqualand Metamorphic Complex with granites and volcanic activity so that by 700 million years ago the complex was thoroughly penetrated by swarms of Dolerite dykes (some up to 100 kilometers long and 1.5 kilometers wide).
Around 550 million years ago continental drift of Gondwanaland took the location of the Fish River Canyon within the Antarctic Circle[1]. Between 320 and 270 million years ago, as the location came closer to the South Pole, glaciation deposited Dwyka till in two distinct moraines. Around 250 million years ago the location of the Canyon moved out of the Antarctic Circle and as the ice receded, huge quantities of melt water were released which found their own drainage channels.
The double canyon of the Fish River was born from a tectonic event (and not erosion). The presence and distribution of Dwyka tillites in and around the Canyon suggests that the Canyon existed before glaciation. 350 Million years ago a tectonic event activated faults to form a Graben [2] resulting in a block of Earth’s crust to down-fault about 250 meters along deep-reaching faults. A triangular section of almost 400 square kilometers from Sulphur Springs in the South, towards Koelkrans in the North slowly down-faulted along several fault lines to form the double canyon.
Today, the area is arid and littered with metamorphosed sandstone shards. Due to sparse vegetation many geological features are visible and an avid hiker can descent into the canyon through billions of years’ of geological forming in under an hour.
Stratigraphical evidence
[edit]Stratigraphically the Fish River Canyon consists of two main layers: (1) the Namaqualand Metamorphic Complex which consists of metamorphosed gneisses, granits (1,700 - 1,200 million years ago) and dolerite dykes (1,200 - 700 million years ago) and (2) the Nama layer which can be broken down into the Kuibis (640??? - 548 million years ago), Schwarzrand (548 - 542 million years ago) and Fish River (542 - 530 million years ago???) subgroups. [3]
Fossil evidence
[edit]Cloudina in Kuibis subgroup Most of the known fossil deposits in Namibia represent the remains of redeposited Coudina. Concretions Stromatolites
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- ^ History of Global Plate Motions: http://www.uwgb.edu/dutchs/platetec/plhist94.htm
- ^ Namibia http://people.bath.ac.uk/exxbgs/journal_articles/06_Namibia.pdf
- ^ Tubular Compression Fossils from the Ediacaran Nama Group, Namibia http://nrs.harvard.edu/urn-3:HUL.InstRepos:3007641