Utah’s Geological Past and its Effect on the Geography ...



Utah’s Geological Past and its Effect on the Geography, Climate and AnimalsChristina TinsleyDixie State CollegeAbstractThe state of Utah has experienced immense geological changes over the millennia. Plate tectonics have shifted the location of Utah from about 30 degrees south of the equator to its current position of about 40 degrees north of the equator. Utah has been the floor of shallow seas as well as the site of vast Sahara like deserts. Plate tectonics created the mountain ranges that make up the Basin and Range Province of Western Utah, the uplift of the Colorado Plateau and the volcanism that existed across the entire state. Changes in latitude and elevation have directly affected the climate and thus the animals that have been able to thrive. Detailed are the different geological processes that have taken place and their effect on the geography, climate and animals. Utah’s Geological Past and the Effect on theGeography, Climate, Plants and AnimalsChanges in latitude and longitude have greatly changed Utah’s climate from that of sub-tropical shorelines, vast Sahara like deserts, swamp lands like those seen in the Okefanokee swamp in Georgia, to the semi-arid desert of today CITATION Hin09 \l 1033 (Hintze & Kowallis, 2009). Changes in global position and elevation determine the types of animals that have been able to thrive in Utah. Hintze and Kowallis (2009) describe in their book, Geologic History of Utah, “Through-out the vast stretches of geologic time, Utah’s geology has been controlled by its place on the ever-moving North American continent as it traveled about, colliding with other continental masses and occasionally growing by accretion” (p. 3). Geologic forces have shaped and evolved the geography, climate and animals that have existed in the past and have become indigenous to Utah today. Earth’s history is broken up into eons, eras, periods and epochs. New eras, periods and epochs mark the end or the beginning of a significant event or speciesCITATION USG06 \l 1033 (USGS, 2006). This paper will cover the geography of Utah as it progressed through the eons from an early molten state with no life to modern day Utah.Hadean, Archean and Proterozoic EonsUp until recent technological advancements, everything that happened prior to the Mesozoic Era was referred to as the Precambrian Eon. Earth’s history is now divided into three distinct and separate eons: the Hadean, Archean and Proterozoic. These eons make up 88% of earths total history and are the oldest rocks in existence CITATION Div10 \l 1033 (USGS, 2010). Hadean Eon- 4600 to 4000 Million Years AgoThe most important event that took place during the Hadean was the formation of the moon. The event that formed the moon is often referred to as the Giant Impact Theory. In the USGS fact sheet, Precambrian Time - The Story of the Early Earth, author Lindsey (2007) wrote: Scientists know from studying the age of craters on the Moon that the early Earth was bombarded by millions of large objects. One of these objects, a giant perhaps the size of Mars, struck the Earth near the end of its formation and burst into a huge cloud of hot particles that coalesced into the Moon (para. 5)It is unlikely that the earth had cooled enough during the Hadeon for plate tectonics to have occurred; the temperature of the earth’s crust is thought to have been too hot and pliable to have formed a solid crust CITATION Zah07 \l 1033 (Zahnle, et al.).Archean Eon- 4000 to 2500 Million Years Ago -1023433527341FIGURE 1. Grand Canyon, Deer Creek Falls, Mile marker 136. Top layer of the canyon is 550 mya. Kaibab Limestone. Bottom most layer is 1.7 mya. Gneiss and Schist.020000FIGURE 1. Grand Canyon, Deer Creek Falls, Mile marker 136. Top layer of the canyon is 550 mya. Kaibab Limestone. Bottom most layer is 1.7 mya. Gneiss and Schist.-5080383476500 A third of the earth’s crust is thought to have formed during the Archean. The North American continent was formed by volcanic island arcs colliding and fusing together to form plutons. These early plutons form the basement rocks of the continental crust. Much of the data that has been collected about how these ancient rocks were formed comes from research on rocks located in the Beaver Dam Mountains, Wasatch Mountains, Raft River mountains of Utah and the Colorado River; which has cut a path directly through the Colorado Plateau, showing a near complete history of deposition CITATION Hin09 \l 1033 (Hintze & Kowallis, 2009). The earliest evidence of primitive life has been found in rocks formed during the Archean. Oxygen also became available in the atmosphere, albeit at only one to two percent of modern day levels CITATION Sha09 \l 1033 (Sharma & Shukla, 2009). These early life forms would grow to become more and more complex in the coming eons.Proterozoic Eon- 2500 to 542 Million Years Ago During the Proterozoic, accretion continues to play a huge role in Utah’s formation. Blakey and Ranney (2009) explain in their book Ancient Landscapes of the Colorado Plateau, “when volcanic islands collided with North America, the former basin deposits were folded accordion style and placed at great depths within the crust…During this process, the rocks became sutured or attached to the continent and became part of its basement” (p. 2). The first supercontinent, named Rodinia, was constructed, fractured and broken apart during the Proterozoic. Evidence of the breakup of Rodinia can be seen in northern Utah in the Uinta Rift-Basin, sediment deposits nearly three miles deep can be found in this ancient rift. 27137271675394Fig. 2. Paleogeography map of North America after the breakup of Rodinia.Late Precambrian 550 million years ago Ron Blakey, NAU Geology 00Fig. 2. Paleogeography map of North America after the breakup of Rodinia.Late Precambrian 550 million years ago Ron Blakey, NAU Geology Glaciation was prominent during the Proterozoic and is often referred to as Snow Ball Earth. It is unclear what the caused this ice age, but it included at least three distinct periods where earth was blanketed in snow and ice. Large glacial deposits can be found in the Wasatch Range, Sheeprock and the Deep Creek Mountains of UtahCITATION Hin09 \l 1033 (Hintze & Kowallis, 2009). Life forms on earth became more diverse and complex, cyanobacteria bacteria emerged and with it more available oxygen in the atmosphere, which may have been the cause of the Cambrian Explosion of new organisms in the Phanerozoic Eon CITATION Sha09 \l 1033 (Sharma & Shukla, 2009).Phanerozoic EonThe Phanerozoic eon is divided into three eras: the Paleozoic, meaning ancient life, the Mesozoic, meaning middle life, and Cenozoic meaning recent life. The Phanerozoic was a time of great change in Utah. During the Paleozoic, Utah spent much of the time beneath the surface of warm, shallow seas. The Mesozoic and Cenozoic show evidence of tremendous continental upheaval. Plate tectonic collisions would build on to the North American plate, creating the land that would become Utah. Dramatic shifts in climate impacted the types of animals that could survive in the area CITATION Hin09 \l 1033 (Hintze & Kowallis, 2009). As the Phanerozoic continued, life forms became more advanced and moved out of the oceans and onto dry land, to become the largest and most advanced the world has ever seen. Paleozoic Era- 542 to 251 Million Years Ago The Paleozoic is divided into seven periods: the Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian and the Permian Periods. Rifting caused by Laurentia breaking away from Australia, Antarctica and China caused the state to be stretched, resulting in the future basin and range to subsidize or lower in elevation CITATION Hin09 \l 1033 (Hintze & Kowallis, 2009). A continental shelf divided the state in the approximate location of the Wasatch Fault Line and the border of the Colorado Plateau. Blakey and Ranney (2008) explain that sediment deposits “document the prior existence of a broad continental shelf (defined as a low-lying margin of continental crust that may be often flooded with seawater), that was crossed many times by repeated transgressions and regressions of shallow seas” (p. 13). Some of these deposits in the western basin range in depth from 1,500 to 10,000 feet in depth, while the area to the east of the shelf on the Colorado Plateau has only a few hundred feet of sedimentation CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). The warm, shallow marine environment in the first half of the Paleozoic, created the perfect setting for the formation of limestone and dolomite, which make most of Utah’s marine rock formations. Stokes (1986) explains in the Geology of Utah, “the present day red color of the Permian unit’s results from an “aging” process of iron-bearing minerals in what may originally have been drab-looking sediments (p. 96). The red rock strata found in national parks such as; Monument Valley, Canyonlands National Park, and Dinosaur National Monument are examples iron rich formations CITATION Wil86 \l 1033 (Stokes, 1986).381002395220FIGURE 3. Paleogeography maps of Western North America during the Proterozoic Eon. A. Late Cambrian- 500million years ago, B. Carboniferous Mississippian- 340 million years ago, C. Permian- 280 million years ago.00FIGURE 3. Paleogeography maps of Western North America during the Proterozoic Eon. A. Late Cambrian- 500million years ago, B. Carboniferous Mississippian- 340 million years ago, C. Permian- 280 million years ago.39681151790700C00C20180301835150B00B774701835150A00ADuring the Pennsylvanian, the continents were once again moving towards one another to form the supercontinent of Pangaea. By the end of the Proterozoic, Pangaea was fully assembled. If someone were traveling during this time period they would have been able to cross from Utah all the way through Africa and into Antarctica by land CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). All life during the Early Proterozoic existed in water; there were not yet any plants or animals that had adapted to living on dry land CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). Life during the Proterozoic eon became more numerous and complex, this is often called the Cambrian Explosion. As Blakey and Ranney explain (2008), “the Cambrian fossil fauna is replete with multicellular organisms that had intricate shells and advanced complex organs such as eyes and body appendages” (p.19). 774702262181FIGURE 4. Representation of the Paleozoic ocean floor. Species include Brachiopods, nautiloids and crinoids CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). 00FIGURE 4. Representation of the Paleozoic ocean floor. Species include Brachiopods, nautiloids and crinoids CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). Utah’s warm, shallow seas were favorable to a broad range of organisms that were spread uniformly across the state, suggesting generally calm conditions. In the Devonian age, Sarcoperygii fish, meaning flesh-finned, developed fins that enabled them to move on dry land. These fins would eventually evolve to become the limbs of the first Terapods, or four footed invertebrate land based life CITATION Joh07 \l 1033 (Foster, 2007). Fossilized evidence of an unidentified amphibian or reptile has been found in Labyrinth Canyon outside of Green River, Utah. At the end of the Proterozoic, the oceans receded to record low levels across the globe CITATION Wil86 \l 1033 (Stokes, 1986). Blake and Ranney (2008) explain that dry conditions” created havoc for these shallow marine organisms as most of their territory was lost. The ensuing extinction of marine life, perhaps attributed to the loss of shallow marine environments worldwide, was the greatest in the entire rock record; more than 90 percent of all species went extinct” (p.52).At the close of the Paleozoic, Pangaea is fully formed and mass extinction has wiped out almost all of the organisms. The Mesozoic would move earth into a more tectonically violent period and plants and animals would become the largest the planet would ever see.Mesozoic Era- 251 to 65 Million Years AgoThe Mesozoic Eon is made up of the Triassic, Jurassic and the Cretaceous Periods. During the Mesozoic tectonic forces molded and formed the early continents into the more recognizable configurations that they are today. The super continent of Pangaea was lifted up in elevation. Blakey and Ranney (2008) explain the reason for continental uplift occurs when “continents, especially large ones, become places where heat accumulates. This causes continental rocks to become less dense, making them more buoyant and causing continents to become elevated” (p. 57). This raise in elevation produced a climate that was increasingly arid and more conducive to erosion. During the Jurassic and Cretaceous, the North American continent drifted away from Pangaea. Deserts would be replaced by tropical swamps and coastal beaches, as an inland sea made its way into Eastern Utah CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). There were three major periods of orogenic activity that have altered Utah, starting in the Mesozoic and continuing into the Cenozoic; the Nevada Orogeny, the Sevier Orogeny and the Laramide Orogeny. These orogenies created the western most states of Washington, Oregon, California, and Nevada. They also produced Utah’s mountain ranges and created widespread volcanic activity across Utah CITATION Hin09 \l 1033 (Hintze & Kowallis, 2009). The description above tells what happened in a very organized, scientific way. However, Orogenesis is not an organized or peaceful process. Huge earthquakes would have ripped through the land twisting, bending and folding the crust to form massive mountain ranges and lowered basins. For example, oceanic crust and seashells have been found at the summits of Utah’s mountain ranges. Much of Utah is made up of a series of upwarps and downwarps, similar to ripples on water. Island arc eruptions are the most violent of volcanic events; explosive pyroclastic flows, huge boulders being shot into the sky and rivers of magma would have been common occurrences.Utah’s environment fluctuated between semi-arid interdune conditions; which contained lakes, rivers and swamps, to arid dune conditions, containing vast deserts that were only broken up by the occasional oasis. Shibata, Matsukawa and Lockley (2006) found in their study of the Late Triassic and Early Jurassic ecosystems that “the low diversity of dune ecosystems represents a severe and stressed ecosystem with limited food. On the other hand, based on track estimates, the interdune ecosystem was almost as diverse as the Late Triassic Chinle formation” which was characterized by a diverse population of dinosaur species (p. 33). Carbon dioxide levels were higher than that of today, causing higher sea levels and a warmer environment, both in the oceans and on land. There was little change in temperature year round between north and south latitudes. The polar ice caps and snowcapped winter mountains did not exist during this time because of the warmer temperatures CITATION Joh07 \l 1033 (Foster, 2007). FIGURE 4. Maps showing the geography and tectonic processes during the Mesozoic Period37585652011045B00B16300572023362A00A422214379513A-B. Late Triassic-215 Million Years AgoElevation was still predominately flat, except for the Ancestral Rocky Mountains in east central area of the state. As the oceans receded, fluvial rivers stretched across Utah. Some of these rivers were relative in size to that of the Nile and the Mississippi CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). 00A-B. Late Triassic-215 Million Years AgoElevation was still predominately flat, except for the Ancestral Rocky Mountains in east central area of the state. As the oceans receded, fluvial rivers stretched across Utah. Some of these rivers were relative in size to that of the Nile and the Mississippi CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). 37572952008505D00D16268702019300C00C422214386443C-D. Early Jurassic-180 Million Years AgoDry, trade winds continually blew moisture away from Utah, creating a massive Sahara like desert. Three major dune systems occupied Utah during the Jurassic: the Wingate, Navajo, and Entrada. Orogenies formed the mountain ranges that started to push eastward into Utah (Blakey & Ranney, 2008). 00C-D. Early Jurassic-180 Million Years AgoDry, trade winds continually blew moisture away from Utah, creating a massive Sahara like desert. Three major dune systems occupied Utah during the Jurassic: the Wingate, Navajo, and Entrada. Orogenies formed the mountain ranges that started to push eastward into Utah (Blakey & Ranney, 2008). 37585652011680F00F15849602016125E00E422214276835E-F. Middle Cretaceous-100 Million Years AgoOrogenies created fault-block mountains in the west, causing the eastern half of the state to subsidize and form a basin. The drop in elevation in the interior of the continent allowed the sea to enter from the north CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). 00E-F. Middle Cretaceous-100 Million Years AgoOrogenies created fault-block mountains in the west, causing the eastern half of the state to subsidize and form a basin. The drop in elevation in the interior of the continent allowed the sea to enter from the north CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). All of the species that are currently living on earth today can trace their ancestors to animals that evolved during the Mesozoic Era. Some examples of animals that lived during the Mesozoic include: crocodilians, turtles, theropod dinosaurs, sauropod dinosaurs, pterosaurs, plesiosaurs, mammals. During the more arid conditions of the Mesozoic research shows that dinosaur populations decreased, those that did stay in the area lived near annually fed rivers or oasis’s that spotted the ancient sand dunes, similar to the present day Serengeti Plains in Africa. The climate during the Cretaceous was more humid and brought about a more diverse population of animals CITATION Shi06 \l 1033 (Shibata, Matsukawa, & Lockley, 2006). Mammals actually outnumbered the dinosaurs by sheer numbers during the Mesozoic. Foster (2007) said in his book Jurassic West, “the diversity of mammals far exceeds all other groups. In fact, there are nearly as many types of mammals in the formation as there are of all four groups of dinosaurs combined…mammals had obviously created enough ecological niches for themselves to equal the dinosaurs in species richness, if not in size or flashiness” (p. 252). The largest mammals were probably only about the size of modern squirrels, until after the extinction of the dinosaurs CITATION Joh07 \l 1033 (Foster, 2007).The Mesozoic ends with the impact of an asteroid, thought to have been nearly 10 miles wide near the Yucatan Peninsula in Mexico CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). The impact blast exterminated everything in its path, enormous tidal waves spread out across the globe, and sediment from the impact blocked out the sun for months on end, killing plant life. As the food chain broke down, all large dinosaurs disappeared, opening a window of opportunity for mammals to come out of hiding and become the new dominate species CITATION Bru101 \l 1033 (Lieberman & Kaesler, 2010).Cenozoic Era- 65 Million Years Ago to PresentThe Cenozoic is made up of the Tertiary and the Quaternary Periods. The relatively flat flood plain that had existed in the Mesozoic is uplifted to form the Wasatch Mountains and the Colorado Plateau. The climate changed considerable during the Cenozoic Era. The early Cenozoic climate was hot and humid, followed by a period of glaciation, and finally to our current semiarid desert conditions. The small mammals that existed in the Mesozoic, evolved into a massive array of new species. Including, but not limited to mammoths, bison, horses, saber tooth cats, giant sloths and a new species that would change everything across the globe, humans!Tectonic forces in previous Nevada and Sevier Orogenies of the Mesozoic exhibited plates that subducted at an angle of about 45 to 60 degrees, resulting in mountain ranges and volcanic activity that were very close to their respective continental margins. Plate subduction of Laramide Orogeny decreased to an angle of approximately 25 degrees. Blakey and Ranney (2008) describe this as an:Unusual angle for a plate to descend but could explain how and why the Rocky Mountains were uplifted almost a thousand miles inland from the plate boundary. The position of the Rockies so far from a plate boundary makes them one of the most enigmatic mountain ranges on Earth. This far reaching deformation event is what uplifted the Colorado Plateau … as much as 15,000 to 17,000 feet (p. 104-105).The Laramide Orogeny produced volcanoes and laccoliths throughout Utah. A laccolith is an intrusion of molten magma that is squeezed horizontally between two layers of sedimentary rock. As the magma billows up, the sedimentary rocks are pushed up to form domes and mountains. The Henry, La Sal, Abajo and Pine Valley Mountain ranges are examples of laccoliths, though Pine Valley Mountain was formed later and is one of the largest laccolith mountains in the world CITATION Bla08 \l 1033 (Blakey & Ranney, 2008).69851787296Paleogeography Maps of Western North America during the Cenozoic Era.A-50 Million Years Ago. B- 15 Million Years Ago. C- Present Day00Paleogeography Maps of Western North America during the Cenozoic Era.A-50 Million Years Ago. B- 15 Million Years Ago. C- Present Day38823901383665C00C749301386840A00A19768821388110B00BThere were three main climatic conditions during the Cenozoic: the early semi tropical, ice age glaciation and lastly to our present semiarid desert. The Early Tertiary climate was hot and humid. Deposits of coal, tar and oil shale have been found in rocks of this age, representing semi tropical conditions, dense with plant life and a thriving populace of animals that evolved from the early shrew like creatures of the Mesozoic CITATION Bla08 \l 1033 (Blakey & Ranney, 2008). Scientists do not know the exact cause of an ice age. Research suggests a combination of factors such as reduced CO2 in the atmosphere, continental drift redirecting oceanic currents and the widespread uplift of new mountain ranges, collectively cause periods of glaciation CITATION Hay02 \l 1033 (Hay, Soeding, DeConto, & Wold, 2002). While the mountains and high plateaus would have been covered with snow, ice and glaciers, Utah’s ice age valleys would have been lush with vegetation. Heaton explains in his article, Quaternary Mammals of the Great Basin: Extinct Giants, Pleistocene Relicts, and Recent Immigrants “the largest mammals such as mammoths, sloths, bison, and oxen never seem to have been abundant in the Great Basin, some large mammals are found in great numbers at most fossil sites, especially horses (several varieties), camels, llamas, and bighorn sheep. When the valleys, which make up 95% of the land area, had much more vegetation and water during the last glacial, the region could probably support a much greater mammalian biomass” (Section 4). Humans appeared in Utah approximately 10 to 12 thousand years ago. They probably did not settle in the area, but travelled through in search of large prey animals, such as mammoth. By about 8,000 years ago large mega faunal mammals were forced to extinction, most likely by abrupt climate change and possible over hunting by early humans CITATION Sco \l 1033 (Elias., 1997). Up until about two thousand years ago, humans eked out an existence as hunter-gathers. It was not until about 750 AD that evidence of permanent housing structures has been found. The Fremont people of Central Utah and the Anasazi people of the Four Corners region either built sophisticated villages, consisting of underground pit houses or elaborate cliff dwellings. Both cultures were known to use advanced irrigation techniques for farming corn and squash. The Fremont and the Anasazi Indians disappeared between 1250 and 1500 A.D., reasons for their disappearance are unknown, but extensive drought is the most common theory CITATION Mad89 \l 1033 (Madsen, 1989). Indian tribes such as the Paiute and Navajo Indians survived the drought and still live in Utah today.ConclusionEarth has undergone great changes in its geography, climate and animal species since its beginning four and a half billion years ago. Utah had a tumultuous beginning; involving plate tectonic collisions, volcanic eruptions and periods of extensive submersion by oceans. These forces have sculpted and formed the crust into the geography that is seen in today.Climate in Utah is tremendously affected by plate tectonics. As the North America plate drifted into its current position, weather patterns also changed. Utah has experienced conditions ranging from hot dry deserts to cold glacier valleys and everything in-between. The animals that have lived in Utah have had to adapt to significant changes in temperature and climate in order to survive. Mass extinctions have wiped out all but a few of the organisms that have existed in Utah; these hardy creatures have evolved into the animals that exist in Utah today.As tectonic forces continue to affect Utah into coming millennia, what changes are in store for Utah’s continued history?References BIBLIOGRAPHY Brusatte, S. L., Nesbitt, S. J., Irmis, R. B., Butler, R. J., Benton, M. J., & Norell, M. A. (2010). The origin and early radiation of dinosaurs. Earth-Science Reviews. 10, 68-100. doi: 10.1016/j.earscirev.2010.04.001.Baldridge, W. S. (2004). Geology of the American Southwest: a journey through two billion years of plate-tectonic history. New York, NY: Cambridge University Press.Blakey, R. C., & Ranney, W. (2008). Ancient landscapes of the Colorado Plateau. Representation of the Paleozoic ocean floor. Grand Canyon, AZ: Grand Canyon Association.Blakey, R. (2011). Paleogeographic and tectonic history of western North America. Paleogeography Maps of Western North America during the Cenozoic Era, Maps showing the geography and tectonic processes during the Mesozoic Period, Paleogeography maps of Western North America during the Proterozoic Eon.Retrieved from Colorado Plateau Geosystems, Inc.: ., S. A. (1997). Paleoindian and archaic peoples. Retrieved from Colorado Plateau: Land use history of North America: Retrieved from , J. (2007). Jurassic west. Bloomington, IN: Indiana University Press.Hay, W. W., Soeding, E., DeConto, R. M., & Wold, C. N. (2002). The Late Cenozoic uplift – climate change paradox. International Journal of Earth Sciences, 91, 746–774. doi: 10.1007/s00531-002-0263-1.Heaton, T. H. (1990). Quaternary mammals of the Great Basin: Extinct giants, Pleistocene relicts, and recent immigrants. In R. M. Ross, & W. D. Allmon, Causes of Evolution: a Paleontological Perspective. (eds.) (pp. 422-465). University Chicago Press.Heaton, T. H. (n.d.). Quaternary mammals of the great basin:. In R. M. Ross, & W. D. Allmon, Causes of Evolution: a Paleontological Perspective. Hintze, L. F., & Kowallis, B. J. (2009). Geologic history of Utah. Provo, UT: Department of Geology, Brigham Young University.Lieberman, B. S., & Kaesler, R. (2010). Prehistoric life: evolution and the fossil record. Hoboken, NJ: Wiley-Blackwell. Retrieved from , D. (2007). Precambrian time—the story of the early earth. U.S. Geological Survey Fact Sheet. para. 5, Retrieved from , D. B. (1989). Fremont. Retrieved from Colorado Plateau: Land use history of North America: , M., & Shukla, Y. (2009). The evolution and distribution of life in the Precambrian eon-global. Journal of Biosciences 34(5), 765-776. doi:10.1007/s12038-009-0065-8.Shibata, K., Matsukawa, M., & Lockley, M. G. (2006). Energy flow modeling applied to data from the Lower Jurassic Navajo Sandstone, Western North America: implication for ecological replacement between the Late Triassic and Early Jurasic ecosystems. In J. Harris, S. G. Lucas, J. A. Spielmann, M. G. Lockley, R. C. Milner, & J. I. Kirkland, The Triassic-Jurassic terrestrial transition ( 29-34). Albuquerque: New Mexico Museum of Natural History & Science.Stokes, W. L. (1986). Geology of Utah. Salt Lake City, UT: Utah museum of natural history & Utah geological and mineral survey.Tinsley, C. (2009) Grand Canyon National Park, Deer Creek Falls. USGS. (2006, 8 18). What is the quaternary? Retrieved from USGS Science for a Changing World: . (2010). Divisions of geologic time- major chronostratigraphic and geochronologic units. Retrieved from USGS fact sheet: , K., Arndt, N., Cockell, C., Halliday, A., Nisbet, E., Selsis, F., & Sleep, N. H. (n.d.). Emergence of a habitable planet. Space Science Reviews, 129, pp. 35-78. DOI 10.1007/s11214-007-9225-z. ................
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