Lecture03

Lecture03 - Parks Formed by Stream Erosion and Weathering...

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Unformatted text preview: Parks Formed by Stream Erosion and Weathering (part 2) BRYCE CANYON ARCHES MESA VERDE Arches Bryce Mesa Verde Stratigraphy of Colorado Plateau From Geology of the Colorado Plateau, 1999, Annabelle Foos, Geology Department, University of Akron Mesa Verde & Bryce Canyon Native American History Basket Maker Culture Later, Pueblo Culture ~ 1200 AD Paiute tribes farmed and hunted, no settlement Photo: NPS Human History (con’t) 1776, Escalente & Dominquez Expedition 1850’s trappers and Mormons in area 1871, John Wesley Powell 1871­76 Wheeler Survey Expedition 1874­1891 Mormon Settlers 1923 NM 1928 NP 1905 area became National Forest Geologic Features Stream Erosion Structural features Differential Weathering Horseshoe Shaped Basin Three regions in park Uplift creates cracks & joints – control features such as pinnacles, The Wall, arches, windows, and natural bridges – similar to Zion Structural Features Joints, differential erosion, frost action, oxidation to give colors Differential Weathering Volcanic Rocks Cenozoic Geologic History ­ Stratigraphy Lake Table 3.2, p. 53 Erosion Rivers Mesozoic Coastal Marine Geologic History – Mz – Cretaceous – Marine to River Cz – Eocene – Claron formation Inland lake – changed size, different rocks Fossils mammals, clams, snails, turtles, plants – Oligocene – volcanic rocks – Miocene – uplift and faulting – Quaternary ­ glaciers Leads to erosion and cooler climate – Arches National Park Human History Early Native Americans used area for chalcedony for tools no known settlements 1800’s – Trappers and Mormons 1929 Arches NM 1971 Arches NP Geologic Features Stream Erosion Differential Weathering Structural Features The Arches Salt Anticline Structural Features – Joints Similar to previous parks Fins Arches Pinnacles and Balanced Rocks Salt Anticline Geologic History Similar to Zion Pennsylvanian – near shore – Permian – Cutler Fm. – evaporites – salt and gypsum – shallow sea Mesozoic History Triassic – similar to Zion Entrada SS –> Arid, near shore and shallow seas Navajo Sandstone ­> Geologic History Cretaceous (End of Mz) – deposition then erosion Lt. Miocene (~13mya) block faulting – Tilted – Uplifted – salt graben forms, jointing Mesa Verde National Park History AD 1­750 Basket Maker Culture AD 750­1300 Classic Pueblo Mid 1700’s Spanish traders, named mesa 1776 Escalante camped in area 1888 dwellings discovered by local rancher 1900 Colorado Cliff Dwellings Association 1906 TR established Mesa Verde NP Possible scene from Spruce Tree House, ~1250 Geologic Features The Cuesta Weathering Erosional Features Water supply The Dwellings Cuesta Geologic Features The Cuesta Erosional Features Weathering – Mesa – Canyons Water supply The Dwellings Erosional Features ­ Mesa Point Lookout Sandstone ­> Mancos Shale ­> Point Lookout Erosional Features ­ Canyons Geologic Features – The Dwellings Geologic History Cretaceous marine rocks Cenozoic tectonics Beaches and dunes Lagoons and Bays Off shore sands Near shore Southern Rocky Mountains in Distance (Looking to the East) Point Look out Sands tone Mancos Format ion Shal es Point Lookout sandstone above Mancos Formation (shales). (Photo by David B. Hacker) Cretaceous Cliff House Sandstone ...
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