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|where sedimentary rocks, such as clays, shales, and limestones, are exposed. Figure 09-04a depicts the sequence of rocks (stratigraphy) that occurs within the park and immediately adjacent to it, including the names and ages of the natural rock layers or strata. The bottom layer (earliest) corresponds to the Devonian Period when earliest amphibians and first forests appeared about 400 million years ago. The Strathcona Park website carries all the information about the geology of the Park and more. While the events and objects listed in Figure 09-04a are related locally within the Park, the history of the Geological Periods in Figure 09-04b is supposed to be global with events re-constructed by geologists and paleontologists. Table 09-01 depicts the geological and biological events in each of the period.|
Figure 09-04a Earth History, Local [view large image]
Figure 09-04b Earth History, Global [view large image]
|Era||Period (MYA)||GEOLOGICAL EVENTS||BIOLOGICAL EVENTS|
|HADEAN||4560-3800||Formation of Earth, solidification of crust, evidence of water, heavy bombardment.||Prebiotic.|
|ARCHEAN||3800-2500||Beginning of rock record, evidence of plate tectonics, magnetic field generation.||Protozoa (unicellular organism).|
|PROTEROZOIC||2500-540||Free oxygen in the atmosphere, glaciation¶, solidification of inner core.||Metazoa (multicellular organism).|
|PALAEOZOIC ERA||(Era of Ancient Life)|
|CAMBRIAN||540-500 (new timescale)||Deposition of Burgess Shale.||Invertebrates (trilobites), corals, sea life of many types proliferating.|
|ORDOVICIAN||500-425||Sea covered most of the planet.||Vertebrates, first fish, mass extinction§.|
|SILURIAN||425-408||Land plants, jawed fishes, ammonoids.|
|DEVONIAN||408-362||Amphibians, forests, sharks.|
|CARBONIFEROUS||362-290||Swamps and coal bearing rocks.||Insects, ferns.|
|PERMIAN||290-245||Formation of Pangaea (the super-continent), desertification occurred.||Reptiles, conifers.|
|MESOZOIC ERA||(Era of Middle Life, Age of Reptiles)|
|JURASSIC||208-145||Oldest surviving ocean floor.||Height of dinosaurs, early mammals and birds.|
|CRETACEOUS||145-65||Oil and gas deposits, broke up of Pangaea, global mountain building.||End of the dinosaurs, first flowering plants.|
|CENOZOIC ERA||(Era of Modern Life, Age of Mammals)|
|TERTIARY||65-1.64||Himalayas and Alps folded.||Evolutionary separation of apes and monkeys, most mammals established.|
|QUATERNARY||1.64-present||Last ice age.||Modern man.|
|Figure 09-04c displays a brief history of the Earth pictorially with key geological and biological events. The terms in the picture are explained briefly below :|
Formation of Earth and Core formation - See "Beginning".
Moon Formation - See "Moon".
Jack Hills Zirconµ - Zircons that formed around 4.4 billion years ago were found there.
Acasta Gnesis - Oldest intact crustal fragment about 4 Ga was found in Acasta River, Canada.
Late Bombardment - Period of heavy meteorites shower as witnessed by carters on the Moon.
Figure 09-04c Brief History of the Earth [view large image]
Bio-carbon from Isua - See "Origin of Life".|
Apex Chert Fossils - Bacteria fossils from Apex Chert, W. Australia. See also "Life on Mars"
Cyanobacteria (Blue-green Algae) - See "Micro-organisms".