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Full-Text Articles in Geology
The Ordovician Period, John J. Renton, Thomas Repine
The Ordovician Period, John J. Renton, Thomas Repine
Readings and Notes
The Ordovician Period extends in time from 505 million years ago until 438 million years ago. You will remember from our discussions of the Cambrian that the Ordovician Period of time and the Ordovician System ofrocks was suggested by Professor Lapworth as a means of solving the dilemma presented by Murchison and Sedgewick as to the "ownership" of a section of rock that both claimed when Murchison wanted to include the upper portion of Sedgewick's Cambrian System as the lower portion of his Silurian System. Sedgewick, you will remember, responded by demanding that the lower portion of his Silurina System …
The Cambrian Period, John J. Renton, Thomas Repine
The Cambrian Period, John J. Renton, Thomas Repine
Readings and Notes
The Cambrian Period extends from 570 million years ago to 505 million years ago. Notwithstanding the discovery of the Ediacara fauna, the Cambrian Period of the Paleozoic Era has historically been taken as the beginning of historical time based on the first appearance of abundant fossil remains. It is interesting to note, however, that where first described, the lower Cambrian was not very fossiliferous.
The Triassic Period And The Beginning Of The Mesozoic Era, John J. Renton, Thomas Repine
The Triassic Period And The Beginning Of The Mesozoic Era, John J. Renton, Thomas Repine
Readings and Notes
The Triassic Period is the first period of the Mesozoic Era, a span of time from 245 million years ago to 66 million years ago. Although the Mesozoic era commonly known as the "Age of the Dinosaurs,', it should be pointed out that there were other important evolutionary developments taking place such as the appearance of the first mammal birds and flowering plans. The onset of the Mesozoic Era, the Triassic Period, was also a time of profound tectonic activity affecting the entire North American craton. In the east, the primary event was the breakup of Pangea and the formation …
The Jurassic Period, John J. Renton, Thomas Repine
The Jurassic Period, John J. Renton, Thomas Repine
Readings and Notes
During the Jurassic Period, Europe was covered by a shallow sea in which a rich fauna was encapsulated in sequences of limestones and shales. These Jurassic rocks were the training ground for many of the early geologists as they began to formulate some of the basic precepts of geology. Foremost amongst these was William Smith (1769-1839) who was the first to discover how to use fossils to correlate between separated outcrops. He gained his knowledge and understanding of fossils in his profession of a surveyor and in the building of canals throughout southern England where the canals were cut into …
The Mississippian Period, John J. Renton, Thomas Repine
The Mississippian Period, John J. Renton, Thomas Repine
Readings and Notes
The first rocks to attract the attention of the early European were those containing the coals, primarily because of their importance in supplying the source of energy for the Industrial Revolution which began in the mid-1700s. As early as 1808, the coal-bearing rocks were referred to on the Continent as the "bituminous terraine' while the British geologists called them the "Coal Measures" The name Carboniferous was introduced in 1822 by Conybeare and Philips when they were attempting to make sense of the rocks of England and Wales. They proposed that all of the rocks from the Coal Measures down to …
The Pennsylvanian Period, John J. Renton, Thomas Repine
The Pennsylvanian Period, John J. Renton, Thomas Repine
Readings and Notes
In many respects, the mountain building of the Acadian Orogeny never really came to an end. Following the collision of Avalonia with the eastern margin of Laurasia with the subsequent creation of the Acadian Highlands, Gondwana and South America, now joined together into a single continent, were approaching from the east and south respectively. Even before the continent-continent collision that would occur at the close of Permian time, the highlands of Acadia along the eastern margin of Laurasia and Llanoria along the southern margin were being maintained as uplands in response to the compressional forces generated by the converging continents. …
The Cenozoic Era, John J. Renton, Thomas Repine
The Cenozoic Era, John J. Renton, Thomas Repine
Readings and Notes
It has been said that the modem world unfolded during the Cenozoic Era. It is true that every feature of the modem landscape was formed during the Cenozoic Era. The Alps and the Himalaya have literally risen from the ocean floor. The Rocky mountains have been formed, worn away and re-uplifted to their present heights. The Appalachian Mountains that had formed at the close of the Paleozoic and worn away by the end of the Triassic, were uplifted and sculpted into their present form during the Cenozoic. All the other mountains of the world were also elevated and sculpted to …
The Cretaceous Period, John J. Renton, Thomas Repine
The Cretaceous Period, John J. Renton, Thomas Repine
Readings and Notes
A global rise in sea level occurred during the Cretaceous; as a result, sea level stood as high during the Late Cretaceous than at any other time in the Phanerozoic history of Earth. Although Pangea had begun to breakup during the Early Mesozoic Era, the smaller continents remained tightly clustered at the beginning of Cretaceous time. The continued breakup of Pangea and the dispersion of the newly created continents were among the most important events that occurred during the global geography of the Cretaceous. Especially important was the breakup of Gondwana. Gondwana was still intact at the beginning of the …
The Permian Period, John J. Renton, Thomas Repine
The Permian Period, John J. Renton, Thomas Repine
Readings and Notes
The Permian Period was a time of great crisis in Earth's history. The Permian saw the final closure of the Iapetus Ocean that had formed following the breakup of the super continent of Rodinia in the late pre-Cambrian; the closure resulting in the formation of another super-continent, Pangea. It was during the Permian that two of Earth's major mountain chains, the Appalachians and the Urals, were created. The period was one of climatic extremes. By the end of the Permian, Earth had not only experienced its most widespread glaciation but also the formation of deserts the likes of which had …
The Silurian Period, John J. Renton, Thomas Repine
The Silurian Period, John J. Renton, Thomas Repine
Readings and Notes
The Silurian Period is the shortest of all the periods of the Paleozoic Era, lasting only 30 million years from 438 million years ago until 408 million years ago. As the Silurian Period opens, the eastern margin ofLaurentia was dominated by the Taconic Highlands that had been created during the Taconic Orogeny at the close of the Ordovician. The rest of the craton was essentially flat-lying and covered by a shallow sea. Except for the northeastern margin which was involved in a major orogeny following the Taconic Orogeny, Laurentia was tectonically quiet throughout the Silurian. About 10 million years before …
The Devonian Period, John J. Renton, Thomas Repine
The Devonian Period, John J. Renton, Thomas Repine
Readings and Notes
Until the 19th century, the rocks exposed throughout the provinces of Devonshire and Cornwall in southwestern England had long been considered to be Carboniferous in age because of their content of fossil plants. Closer investigation by Murchison and Sedgwick in 1836, however, showed that only the uppermost portion of these rocks contained fossil plants. Because the lower portion of the rock sequence was devoid of plant fossils, was highly deformed, and resembled the rocks of northwest Wales which they had recently studied, Murchison and Sedgwick assigned the rocks to the Cambrian System. However, local fossil collectors had submitted fossil corals …