The mass extinction of Marine-life in the Silurian Period opened up endless possibilities and potential for terrestrial life in the next Geologic time period, The Devonian Period. The Devonian Period served as an introduction to the expansion of the first amphibians, sharks, and some of the first plants with roots, leaves, and stomata. Despite such significant advances, the Devonian Period is best known for its diversity and abundance of underwater life. Not only did fish with cartilage begin to appear during this period, but also fish with bony skeletons and it are these primitive predecessors of fish that encompass a majority of modern fish.
Numerous noteworthy changes in the world's geography took place during the Devonian Period. During this period, the world's land was split between two supercontinents, Gondwana and Euramerica (Rice). These vast landmasses sat relatively close to each other in a single hemisphere, while a vast uninterrupted ocean covered the remainder of the globe. These two supercontinents were completely surrounded by numerous subduction zones. The subduction zone between Gondwana and Euramerica set a major collision in motion that would later bring the two continents together to form the massive single continent, Pangaea (Rice).
In addition to ample global shifts, many important regional activities occurred. The continents of North America and Europe collided, resulting in massive granite formations as well as the formation of the Appalachian Mountains located on the eastern side of the North American continent. Extensive reef building produced some of the world's largest reef complexes (“More Info about the Devonian World”). These reefs were built in the equatorial seas between the two preexisting cont...
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Rice, Stanley A. "Devonian." Science Online. Facts On File, Inc. Web. 25 Apr. 2012. http://www.fofweb.com
Kusky, Timothy. "Devonian." Science Online. Facts On File, Inc. Web. 25 Apr. 2012. http://www.fofweb.com
University of California Museum of Paleonto (Lead Author);C Michael Hogan (Topic Editor) "Devonian". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth January 22, 2010; Last revised Date November 17, 2011; Retrieved April 25, 2012 http://www.eoearth.org/article/Devonian
Sallan, Lauren Cole, and Michael I. Coates. "End-Devonian Extinction and a Bottleneck in the Early Evolution of Modern Jawed Vertebrates." Diss. Cambridge University, 2010. 17 May 2010. Web. 25 Apr. 2012. http://www.pnas.org
The area composed of the Gander, Nashoba, Avalon, and Meguma Terranes has been extensively studied for many years. However, it was only recently that the terranes were recognized as distinct geologic entities with unique tectonic histories thus there is still much debate regarding the tectonic model which brought these terranes together (Hon et al., 2007). This paper will address the geology of the peri-Gondwanan terranes and propose a potential tectonic model for the accretional orogenic events. It will also primarily focus on the juxtaposition between the Nashoba and Avalon Terranes.
The shelf-edge includes carbonate-to-clastic facies transition and tectonic uplift and erosion of the carbonates followed by deposition of the clastics. The Saint Peter Sandstone is a well-sorted, almost pure quartz arenite deposited during a major mid-Ordovician low stand. Clastics spread across an exposed carbonate platform by transportation. This is shown by the well-rounded, frosted texture of the quartz grains.
1) Carroll, R. L. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York.
The central belt of the Franciscan Complex represents older and more metamorphosed units of rock best characterized as a melange. Blocks of graywacke, greenstone, chert, limestone, and blueschists are sheared and thrust upon one another in a choatic mix (Isozaki and Blake, 1994). In contrast to the coastal belt, metamorphism is higher in grade here and dominated by pumpellyite which formed within the matrix of graywacke (Hagstrum and Murchey, 1993). The mixing of these units makes a stratigraphic subdivision difficult but analysis of the graywacke slabs indicates that the depositional environment was also deep sea, near to the continent. Turbidity currents in this environment deposited much of the sediment in both the coastal and central belts.
Majungatholus atopus roamed the plains of northwestern Madagascar about 70 million years ago during the Late Cretaceous (Perkins, 2003; Rogers et al, 2003). The discovery of 21 tooth-marked elements originating from two Majungatholus atopus individuals suggests evidence that the dinosaur supplemented its diet by feeding on its own dead or hunting them (Rogers et al, 2003). It cannot be confirmed whether they were purely scavengers, hunters, or both. Scientists are certain that the marks are not the doing of any other predator because the teeth marks are not consistent with any other known species that lived in the area. Only one other theropod that inhabited the area during the time Majungatholus atopus did, Masiakasaurus knopfleri, had teeth and bite marks too small to have caused these markings. Two large crocodile species also shared the same ecosystem but their teeth were “too blunt and too irregularly spaced to have produced the narrow grooves found on the Majungatholus bones”(Perkins, 2003). The tooth marks on at least nine Majungatholus elements attest to intertooth spacing in the perpetrators jaw and denticle drag patterns consistent enough to make a compelling case for Majungatholus feeding on other Majungatholus (Rogers et al, 2003).
During the Late Cretaceous a period of mountain building occurred along the west coast of North America. This is called the Laramide orogeny that started the Rocky Mountains growth about seventy-five million years ago. The Laramide orogeny was different from orogenies that had happened before hand. What caused the Laramide Orogeny is uncertain but there are many theories about what caused it. One big thing to better understand the Laramide orogeny is the theory of Uniformitarianism.
Fig.6 showing a map of Earth during the Devonian period. Yellow star showing Anglesey. http://eeos260-f13-poynton.wikispaces.umb.edu/-/Ancient%20Wiki%20Project/Grp10%20Devonian%20and%20Silurian%20Periods/
This breaking up of the mega continent of Pangaea allowed for more diversification of plant species and as the continents continued to break apart, plant life became even more diversified. As the continents shifted and moved from one area of the ocean to another the climates began to change drastically which allowed for plant and dinosaur species both to begin adapting to suit their new ecosystems. All the water that was produced by the split of Pangaea gave the previously hot and dry climate a more humid and drippy subtropical weather. Dry deserts took on a greener look. Before the Mesozoic Era, livings things were confined to only surviving in the oceans. It was not until the Jurassic Period that livings things evolved the capability of living on the land rather than just the ocean. Towards the beginning of the Jurassic, plant life evolved from Bryophytes, the low-growin...
...t of laurasia, just like most of the other plates. North America,Europe, and Green land all used to be connect because of Pangea ( as mentioned earlier). But when everything started to separate, first europe, then green land, and lastly the North American plate. After pangea was no more and the plates all started moving, the continents started going their own ways, there fore putting the continents where they are today.
The Burgess Shale Fauna is a fauna that was constructed based on a group of fossils that were initially found, in the Burgess Shale area in the Canadian Rockies (Gould, 1989). They are a very important group of fossils as “modern multicellular animals make their first unprotected appearance in the fossil record some 570 million years ago” through this group (Gould, 1989, pp. 24). Moreover the Burgess Shales are known to have preserved the soft parts of animals enabling us to get a better understanding of life at the time.
Acanthostega had a fish-like tail and gills for breathing under water, this being the aquatic part of it. But at the ends of the arms were “peddle-shaped” appendages, thought to be the first “hands” on Earth. Clack’s discovery proved that some fish had arms and legs in the water. It showed that arms and legs were already evolved before organisms started actually living on land, they were used more for survival than walking. In a sense, the “blueprints” of an arm were already in place.
According to scientists, one of the most extraordinary bursts of evolution ever known was the Cambrian Explosion. For most of the nearly 4 billion years that life has existed on Earth, evolution produced little beyond bacteria, plankton, and multi-celled algae. Then, about between 570 and 530 million years ago, another burst of diversification occurred. This stunning period is termed the "Cambrian explosion," taking the name of the geological age in which the earlier part occurred. A recent study revealed that life evolved during the Cambrian Period at a rate about five times faster than today. But it was certainly not as rapid as an explosion; the changes seems to have taken around 30 million years, and some stages took 5 to 10 million years. The Cambrian explosion was a period of time where life evolved into numerous multifaceted organisms that developed into the vertebrates and human life as we know today.
Over the past century, the Burgess Shale has revealed important information about the development of earth’s history. The excavation of the Burgess Shale formation provided evidence for what was once just a theory in evolution. The taphonomic findings of the Burgess Shale have played a significant role in understanding the large diversity that resulted from the Cambrian explosion, advancing the study of evolutionary assemblages for Paleontologists worldwide.
Welsh, Jennifer. "Fossil Teeth Show Mammals Thrived Before Dinos Died." LiveScience. TechMedia Network, 14 Mar. 2012. Web. 14 Mar. 2014.
Earth was formed 4.8 billion years ago (3) . It became the home for hazelnuts because it had an atmosphere and environment which allowed for life to prosper in later years. Earth’s surface was once composed of a single landmass, known as Pangaea (1).Over time it was broken up into seven different plates which were free to move as a result of movements in the hot, semi-liquid magma beneath the...