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Grand Staircase-Escalante National Monument Geology Unit 2 Student Activity VII. Carmel Jc and Page Jp Formations Time formed Rock Appearance: Special features Environment when formed Similar modern day habitats ~ 170 mya, Mesozoic/Late Jurassic Silty limestone, shaly sandstone, shale, minor gypsum Red, white, brown; 90 to 200 feet. Composed of many different member layers, some form cliffs, others, slopes. Notable member is the Thousand Pockets Tongue of the Page Sandstone, composed of windblown, cross-bedded sandstone. Alabaster gypsum, crinoid fossils. Marine and coastal environments along which huge shallow bays of seawater, cut off from the neighboring ocean, evaporated leaving layers of gypsum salts. The Carmel represents a time when a seaway entered the area from the North. The Page Sandstone formed from desert dunes that pushed into the area from the east. Persian Gulf Time formed Rock Appearance: Special features Environment when formed Similar modern day habitats Missing rock layers VIII. Entrada Sandstone –Je ~165 mya, Mesozoic/ Late Jurassic Sandstone, siltstone Red, gray, white; 200 to 800 feet; some cliff forming The Entrada forms the lower part of the Gray Cliffs; can erode into “slick rock” shapes; dinosaur track ways. Partly windblown sand dunes and partly tidal flat; sabhka and beach type deposits. At times the ocean encroached into the area, creating marine sandstones and siltstones. A sandy desert along a beach, similar to beaches along the Persian Gulf. Another unconformity 9
Grand Staircase-Escalante National Monument Geology Unit 2 Student Activity Time formed Rock Appearance: Special features Environment when formed Similar modern day habitats Missing rock layers VIII. Eastern – Morrison Formation – Jm ~150 mya, Mesozoic/Late Jurassic River deposited sandstone, mudstone Gray, blue, red/purple/green and yellow-brown streaks; 0 to 900 feet; some members cliff forming, others slope-forming. Low grade uranium; in northern Utah, this layer has Dinosaur National Park’s fossils Lowlands with rivers, streams, and their associated sandbars; floodplains and gravel beds (conglomerates) Braided rivers and streams similar to those coming off the Andes Mountains in South America Another unconformity IX. Dakota Formation –K Time formed Rock Appearance: Special features Environment when formed Similar modern day habitats ~95 mya, Mesozoic/Late Cretaceous. Sandstone, mudstone, shale, conglomerate, and coal. Brown, yellow, gray; 0-250 feet, mostly slope-forming. Some coal present. Dakota Sandstone is one of the most widespread formations in the western United States. It forms the upper part of the Gray Cliffs, which are not as visually striking as the White Cliffs below and Pink Cliffs above. The Gray Cliffs lack towering, massive cliff faces, and have a rather rounded or eroded appearance. Varied. Shallow marine and near shore swamps. The Western Interior Seaway was advancing into the North American Continent, extending from the Gulf of Mexico to the Arctic, depositing belowsurface sandstone and other layers. Over the next tens of millions of years, the sea would rise and fall, sometimes leaving marine sediments, and other times retreating to allow terrestrial environments. Coal was formed in lagoon swamps with lush plant growth. Coastlines of Florida or Louisiana. 10
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Plate Tectonics and the Rock Layers of Grand ... - Gsenmschool.org

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