This article may be too technical for most readers to understand.(January 2020) |
Eagle Ford Group | |
---|---|
Stratigraphic range: Cenomanian-Turonian ~ | |
Type | Group |
Sub-units | Britton Formation, Arcadia Park Shale Formation, Lake Waco Formation, South Bosque Formation, Boquillas Formation |
Underlies | Austin Chalk |
Overlies | Woodbine Formation or Buda Limestone |
Lithology | |
Primary | Shale |
Other | Marl, limestone, sandstone, volcanic ash beds |
Location | |
Region | Texas |
Country | United States |
Type section | |
Named for | Eagle Ford, Texas[1] |
Named by | Robert T. Hill[1] |
Year defined | 1887 |
The Eagle Ford Group (also called the Eagle Ford Shale) is a sedimentary rock formation deposited during the Cenomanian and Turonian ages of the Late Cretaceous over much of the modern-day state of Texas. The Eagle Ford is predominantly composed of organic matter-rich fossiliferous marine shales and marls with interbedded thin limestones. It derives its name from outcrops on the banks of the West Fork of the Trinity River near the old community of Eagle Ford,[1] which is now a neighborhood within the city of Dallas. The Eagle Ford outcrop belt trends from the Oklahoma-Texas border southward to San Antonio, westward to the Rio Grande, Big Bend National Park, and the Quitman Mountains of West Texas.[2] It also occurs in the subsurface of East Texas and South Texas, where it is the source rock for oil found in the Woodbine, Austin Chalk, and the Buda Limestone,[3] and is produced unconventionally in South Texas and the "Eaglebine" play of East Texas.[4]
The Eagle Ford was one of the most actively drilled targets for unconventional oil and gas in the United States in 2010,[5] but its output had dropped sharply by 2015.[6] By the summer of 2016, Eagle Ford spending had dropped by two-thirds from $30 billion in 2014 to $10 billion, according to an analysis from the research firm Wood Mackenzie. This strike has been the hardest hit of any oil fields in the world. As of 2016, the spending was, however, expected to increase to $11.6 billion in 2017. A full recovery was not expected any time soon.[7]
Fossils are relatively common in Eagle Ford rocks. Fossilized Plesiosaurs, mosasaurs, Fish, shark teeth, crustaceans, sea urchins, feather stars, ammonites, oysters, clams, and other gastropod shells have all been found there.[8][9][10]
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