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The volcanic eruption that produced the Deicke K-bentonite bed which has been dated to 457.1 ±1.0, which was calculated using a concordant uranium-lead dating zircon fraction. [2] The Deicke and Millbrig eruptions have a minimal estimation of 600,000 km 2 (230,000 sq mi) covered and at least 1,122 km 3 (269 cu mi) of pre-compaction bentonite ...
Bentonite layers from an ancient deposit of weathered volcanic ash tuff in Wyoming Gray shale and bentonites (Benton Shale; Colorado Springs, Colorado). Bentonite (/ ˈ b ɛ n t ə n aɪ t / BEN-tə-nyte) [1] [2] is an absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite.
The Tioga Bentonites are a series of ash bed layers occurring in three Sedimentary basins in the eastern and midwestern United States. The primary basin they are found in is the Appalachian Basin, as well as the Illinois Basin and the Michigan Basin. Due to an unconformity these ash beds are not present in the southern Appalachians. [1]
Clay, mud, silt, cross-bedded sand, and pebbles were later deposited by meandering streams and in flood plains, forming the locally 100 to 500 foot (30 to 150 m) thick Salt Wash Member. [14] Claystone and mudstone beds of this member erode into gray slopes that can exhibit brown, red, yellow, and green colors.
Tool marks are a type of sole marking formed by grooves left in a bed by objects dragged along by a current. The average direction of these can be assumed to be the axis of flow direction. Mudcracks form when mud is dewatered, shrinks, and leaves a crack. This tells you that the mud was saturated with water and then exposed to air.
Beds of lava flows exposed on the island of La Gomera. Bed thickness is a basic and important characteristic of beds. Besides mapping stratigraphic units and interpreting sedimentary facies, the analysis of bed thickness can be used to recognize breaks in sedimentation, cyclic sedimentation patterns, and gradual environmental changes. [10]
The Tropic Shale is predominantly marine mudstone and claystone, with several radioisotopically-dated bentonite marker beds, and occasional sandstone layers deposited during the late Cretaceous Period during the Upper Cenomanian through the Middle Turonian (95-92 Ma). The Tropic Shale has an average thickness range from 183–274 m.
The Jurassic-Cretaceous boundary is seen where the red and purple beds of the Morrison Formation abruptly contact the drab, gray bed of the overlying Cedar Mountain Formation. The contact is the K1 unconformity. Jessie's Twist, southwest of Green River City, Utah. Brushy Basin Member showing the purple and red colors of paleosols (ancient soils).