Primary Structures II

Advanced Tectonics
James S. Aber


Primary Structures in Carbonate Rocks

Canal section in the Key Largo Limestone of Pleistocene age. A large branching coral (Acropora palmata) is shown in growth position. Section is about 3 m (10 feet) high. Key Largo Canal, Florida Keys.
Cross-bedded oolitic limestone of Pleistocene age. This sediment accumulated on a shallow shoal about 125,000 years ago. Miami Oolite, Miami, Florida.
Jackie Puterbaugh demonstrates a "reef" in the Frisbie Limestone Member of the Wyandotte Formation, Holliday, Kansas.
Upper Cretaceous chalk (Maastrichtian) and lower Tertiary limestone (Danian) boundary in the coastal section at Stevns Klint, Denmark. Large "bank" forms are visible in the upper limestone.
Overhang of bryozoan limestone (Danian) above chalk (Maastrichtian).
Subtle channel with cross-bedded chalk (behind scale pole) in Arnager Kalk (upper Cretaceous) on the island of Bornholm, Denmark.
Carbonate turbidites in the Dimple Formation, Marathon Basin, west Texas. Sedimentary structures are similar to clastic turbidites.

Fossils in Sedimentary Strata

U.S. Great Plains. Left: fossil oreodont in Oligocene (Paleogene) alluvial strata, Toadstool Park, northwestern Nebraska. Right: burrow fillings in Pennsylvanian sandstone, north Texas.
Lower Cambrian strata, island of Bornholm, Denmark. Left: burrowed top of Balka Sandstone. Right: burrows in "Grønne Skifre" (green shale. Black spots are phosphorite nodules (Bruun-Petersen 1977).

Footprint trackway. Casts on bottom side of sandstone bed in vertical position, Sangre de Cristo Formation (upper Pennsylvanian), Cuchara, Colorado. Presumably made by a reptile or amphibian on a land surface marked by raindrop impressions.

Primary Structures in Igneous Rocks

Wannenköpfe scoria cone. A complete section through the cone is visible in the scoria mine. Eifel region, western Germany.
Dike on side of Wannenköpfe scoria cone. Dikes formed when superheated ground water erupted through tephra deposits. Eifel region, western Germany.
Growth faults in Eppelsberg scoria cone. Growth faults are caused by internal collapse during continued surficial deposition of tephra. Note people at bottom for scale. Eifel region, western Germany.
Tree molds in tephra near top of Eppelsberg scoria cone, Eifel region, western Germany.
Tephra rim of Leyendecker volcano. Note the evenly bedded, gently inclined layers of tephra. Eifel region, western Germany.
Peridotite (olivine) xenoliths, Leyendecker volcano, Eifel region, western Germany.
Niedermendiger lava flow with columnar jointing, Eifel region, western Germany.
Collapsed lava flow with cave. Late Holocene eruption, 1500-2000 years old. Valley of Fires, New Mexico.
Casa Grande, a thick lava cap on a stratified pile of Tertiary volcanic deposits. Notice vertical dikes on near side of hill. Big Bend National Park, west Texas.
Eroded core of Tertiary volcano, known as the Elephant Tusk, Big Bend National Park, west Texas.
Goemmer Butte, an eroded Tertiary volcano core, Raton Basin, near La Veta, Colorado.
Spectacular columnar jointing is visible in Devils Tower, Wyoming. People at bottom are standing amid large joint blocks.
West Spanish Peak with dikes, seen from Goemmer Butte, Raton Basin, near La Veta, Colorado. Dikes radiate from the peak like spokes of a wheel.
Side view of the Devils Stairsteps, a Miocene dike related to West Spanish Peak, Raton Basin, near La Veta, Colorado.
View along the length of the Devils Stairsteps dike, Raton Basin, near La Veta, Colorado.
Crazy Horse mountain, Black Hills, South Dakota. Precambrian crystalline (gneiss) basement rocks host the gigantic sculpture in progress. Notice people standing on top.
Closeup view of Crazy Horse mountain, Black Hills, South Dakota. Notice inclusions of dark (mafic) rock above the eye and nose.
Felsic pegmatite (pink & white) in mafic Archean gneiss. Granite Falls, south-central Minnesota.

Reference

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Notice: Advanced tectonics is presented for the use and benefit of students enrolled at Emporia State University. Others are welcome to view the course webpages. Any other use of text, imagery or curriculum materials is prohibited without permission of the instructor. All text and imagery © J.S. Aber (2014).