A New Specimen of the Ornithischian DinosaurHaya griva, Cross-Gobi Geologic Correlation, and the Age of The Zos Canyon Beds
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Although Mesozoic fossils are quite common in the Gobi Desert of Central Asia, it is often difficult to correlate among different localities because of a dearth of rocks amenable to absolute dating. Specifically, correlating between the eastern Gobi Desert and more western localities has been challenging. Here we give a Santonian-Campanian age for the enigmatic Zos Canyon beds in the Nemegt basin. This is based on the occurrence of the primitive ornithopod dinosaur Haya griva at both eastern Gobi exposures of the Javkhlant Formation and the Zos Canyon locality.Keywords:
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United States Geological Survey, Woods Hole, Massachusetts. Chief Scientists: Dennis O'Leary, Bonnie McGregor. Data (navigation) of field activity 81029 (G-12-81-NA) in Oceanographer Canyon, Lydonia Canyon, Atlantis Canyon, Alvin Canyon, United States, North America, North Atlantic from 07/27/1981 to 08/17/1981, http://walrus.wr.usgs.gov/infobank/g/g1281na/html/g-12-81-na.meta.html.
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It is found that the Polungtsangpo valley is also one of great canyons in the world. It might be at least the third greatest canyon fallowing the Yalungtsangpo Canyon and the second one, Kaligendege Canyon of Nipal. Its depths can reach up to 4 001 m, 3 397 m and 3 271 m in the down and upper streams, respectively. It is 50 km and 76 km long depending on different upper branches.
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Channel expansions are sites of deposition in bedrock canyons and alluvial rivers.Within these areas, deposition is commonly focused at the separation point, reattachment point, eddy center, or along the shear surface that separates the recirculation zone from the downstream flow in the main channel.This study examined the internal structure of reattachment bars, separation bars, and natural levees along the Colorado River in Grand Canyon, Arizona.The recirculation deposits (separation and reattachment bars) are characterized by a rotary flow pattern that includes upstream flow.Flow patterns within channel expansions vary with discharge.Increases in discharge generally increase the length of the recirculation zone.Both the rotary flow pattern and lengthening of the recirculation zone have been documented from internal structures in the bars.The character of climbing-ripple structures in the bar deposits demonstrates that recirculating flows pulsate erratically; field and lab current-meter measurements have demonstrated that these erratic pulsations occur even when discharge in the main channel is steady.Depositional processes and internal structures differ for the three kinds of bars that were studied.During a single flood, deposits of reattachment bars are thickest.Reattachment bars typically produce fining-upward sequences, because circulation over the bars eventually weakens as upward growth restricts flow from the main channel.Separation-bar flood deposits are relatively thinner and are characterized by transgressive deposits that are commonly dominated by wave-generated structures.Levee deposits originated where bankward-directed flow transported sand onto narrow floodplains along the channel.Flow behind the levees was relatively weak and was typically directed downstream.Depositional rates were determined for a variety of sites by examining sedimentary structures in deposits that survived subsequent flows.During the large flood of 1983 (with a peak that approached 100,000 cfs), deposition on some bars exceeded several meters, corresponding to a depositional rate of a few tens of centimeters per day.During the weaker floods of 1984, 1985, and 1986 a total of approximately three months of flow that approached 50,000 cfs deposition was limited to a few tens of centimeters, corresponding to a depositional rate of approximately 1 cm per day.During flows within the range of power-plant operations (not exceeding approximately 30,000 cfs), depositional rates range to approximately 5 cm per day.In all flows, the range of depositional rates can be expected to have varied considerably, from sites that experienced net erosion or nondeposition to sites that exceeded the observed rates.Three kinds of effects must be considered when evaluating flow alternatives on camping beaches: submergence/emergence of bars, erosion/deposition of bars, and net sediment transport through the canyon.A relatively large annual fluctuation and small daily fluctuation allow deposition at high elevations for a short time and allow emergence through most of the year; low daily fluctuations allow camping on bars that otherwise would be inundated daily.
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A Grand Old Canyon In the southwestern United States, the Grand Canyon is a striking example of the power of erosion over time. Over millions of years, flowing river water carved out the canyon that today measures over 1.6 km deep and 29 km long. Most models posit that the majority of the canyon formed 5 to 6 million years ago. Using thermochronometry, Flowers and Farley (p. 1616 , published online 29 November) examined the temperature-dependent diffusion of helium within mineral grains representative of the canyon basement, which cools as erosion brings crustal rocks near the surface. After validating the approach across the younger eastern canyon, the model suggests that the western canyon experienced an ancient cooling event induced by erosional processes, such that the canyon likely reached near modern depths by 70 million years ago—nearly 60 million years earlier than generally believed.
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Reviewed by: Canyon of Dreams: Stories from Grand Canyon History by Don Lago, and: The Grand Canyon Reader ed. by Lance Newman Hal Crimmel Don Lago, Canyon of Dreams: Stories from Grand Canyon History. Salt Lake City: U of Utah P, 2014. 368pp. Paper, $19.95; e-book, $16.00. Lance Newman, ed., The Grand Canyon Reader. Berkeley: U of California P, 2011. 264pp. Cloth, $52.95; paper, $20.95; e-book, $19.95. Anyone planning a visit to or reflecting on an experience in the Grand Canyon will find Canyon of Dreams: Stories from Grand Canyon History and The Grand Canyon Reader engaging. Much as the canyon itself reveals its secrets with every mile hiked or floated, so too do these books provide ever-greater insights into one of America’s most iconic places. Both books seem a reflection of the canyon itself—a place where experience leads simultaneously to greater insight about self, place, and human nature but also leads to a profound sense of wonder because, despite all the stories, the historical accounts, and the geological and scientific studies, that essence of mystery and possibility remains intact, if not stronger, for one’s time in the canyon. Don Lago’s Canyon of Dreams is a highly engaging and expertly researched book about off-the-radar Grand Canyon history. As the author notes, “many great stories have barely been noticed or have remained entirely unknown” (6), and this book brings to light many of these fascinating stories. These include the geologic training provided to the Apollo astronauts, Edwin Hubble’s visit, the battles between the National Park Service and William Randolph Hearst over Hearst’s property on the rim, and the details behind the famous children’s book Brighty of the Grand Canyon. There are also chapters on the canyon connection of singer-songwriter Roger Miller (of “King of the Road” fame) and the role of writers such as Harriet Monroe (founder of Poetry magazine), John Muir, Edgar Lee Masters, Carl Sandburg, William Burroughs, and Mary Austin in shaping the public’s view of the canyon. As Lago notes, the poets “had little influence on public perceptions of the Grand Canyon,” perhaps due to their brooding introspection, whereas writers such as “Muir and Mary Austin seemed fairly immune to existential doubt, and they and John C. Van Dyke helped create the Grand [End Page 404] Canyon that today’s visitors expect to find: a scene of deep beauty and peace” (249). The book is rounded out by chapters on British writers, Henry Miller, tall tales, and a personal reflection on history; readers already familiar with the Grand Canyon will get a great deal from this book, though it will also enhance the experience of those visiting for the first time. Canyon of Dreams is fascinating not only for its deft storytelling around little-known events, such as the conflict between the Roosevelt family and Hearst, which becomes part of a larger narrative about the debate over the role of wilderness in America, or for placing Hubble’s visit to the canyon in the context of his famous discovery that the universe was expanding, but also for its ability to help us see so much more about the canyon than meets the eye. My own experiences in the Grand Canyon, which include several private river trips, hiking, and some rim tourism, certainly were defined by that sense of “deep beauty and peace” Lago identifies. But as a result of reading this book I now find that the human conflicts—the jealousies, the greed, the petty baroque dramas—have also entered my canyon sense of place. In the final chapter Lago discusses John Hance, for whom a trail and rapid are named in the canyon, and notes “the mystery of how one life blends with the currents of a nation’s history” (326). Visitors to the canyon who read Lago’s book will likely share in that mystery. One can’t ask much more of a book. Lance Newman’s The Grand Canyon Reader contains twenty-seven selections primarily from well-known authors such as Edward Abbey, Linda Hogan, Barry Lopez, John Muir, and Terry Tempest Williams, as well as...
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