Serpent Mound Crater

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The Serpent Mound Crater is an eroded impact crater in the southern US state of Ohio . The impact took place after the Upper Carboniferous ( Mississippium ).

location

The Serpent Mound Crater, captured from an airplane

The Serpent Mound Crater, also known as the Serpent Mound Disturbance , is named for the Serpent Mound , which is located on a plateau in the Bush Creek Valley to the southwest of the crater structure. The pioneers of the time had already noticed the unusual terrain in the 19th century and it was consequently often assumed that the Native Americans had built their mound in the crater for this reason .

Most of the crater belongs to Adams County , touching Highland County to the north and Pike County to the northeast .

geology

The Precambrian basement is found below the Serpent Mound Crater at a depth of 1,128 meters. It belongs to the neoproterozoic Grenville Province , which is pushed along the Grenville Front 50 kilometers further west on the Granite-Rhyolite Province flat to the west. The basement is covered discordantly by the Paleozoic, which dips only slightly to the east . The Paleozoic sediment sequence is here on the western edge of the Appalachian Basin , in the transition area to the high altitude of the Cincinnati Arch . The relatively undisturbed series of sediments outside the crater begins with the Middle Cambrian and extends into the early Lower Carboniferous ( Mississippian ). The sediments mainly consist of dolomites , limestone , clay slate , sandstones and subordinate siltstones , potassium-rich bentonites and chert . The series deposited on the eroded Precambrian basement is generally transgressive. The more than 1000 meters thick Paleozoic Era is then in turn covered discordantly by glacial deposits of the Pleistocene ( Illinois ), which, together with Holocene alluvium , colluvium and recent soils, mask the area of ​​the crater.

description

The Serpent Mound Crater is a complexly composed crater with a central impression, a transition zone and an annular trench - a ring-shaped trench structure on the outer rim of the crater. The crater is now completely eroded, but its original diameter has been narrowed down to 8 kilometers. However, a study from 2010 estimated it to be much higher at 14 kilometers.

Impact structures

R. S Dietz had already found cones of rays in the crater area in 1960 . In 1979, two boreholes were drilled to a depth of 629 and 903 meters in the crater area, which were able to detect very disturbed layer conditions in the crater. RW Carlton and colleagues examined the 903 meter long drill core from the central area in 1998 and found planar deformation lamellae in all rock-forming minerals, especially in quartz . In this borehole, additional cones of rays up to 17 centimeters in size could be discovered. Breccias with possible evidence of impact melts were also found . The breccias also showed accumulations of siderophilic elements such as chromium , cobalt , nickel and iridium , which suggest up to 0.2% of a meteorite component in the breccias.

Age

The exact age of the crater structure is not yet available, so it can only be narrowed down relatively. A paleomagnetic study by Doyle R. Watts (2004) suggests that it cannot be less than 256 million years old (outgoing Permian , Lopingian ). Mississippi Valley-type carbonate-based mineralizations limit their maximum age to the end of Upper Carboniferous ( Pennsylvania ) (around 300 million years).

Individual evidence

  1. ↑ Reidel, SP, Koucky, FL and Stryker, RJ: The Serpent Mound disturbance, south central Ohio . In: American Journal of Science . tape 282 (9) , 1982, pp. 1343-1375 , doi : 10.2475 / ajs.282.9.1343 .
  2. ↑ Baranoski, Mark T. et al .: Subsurface geology of the Serpent Mound Disturbance, Adams, Highland, and Pike Counties, Ohio . In: Report of Investigations . No. 146. State of Ohio, Columbus 2003, pp. 1-60 .
  3. ↑ Milam, Keith A.: A Revised Diameter for the Serpent Mound Impact Crater in Southern Ohio . In: The Ohio Journal of Science . tape 110 (3) , 2010, p. 34-43 .
  4. ↑ RS Dietz: Meteorite impact suggested by shatter cones in rock . In: Science . tape 131 , 1960, pp. 1781-1784 .
  5. ^ Richard W. Carlton et al .: Discovery of microscopic evidence for shock metamorphism at the Serpent Mound structure, south-central Ohio: confirmation of an origin by impact . In: Earth and Planetary Science Letters . tape 162 , 1998, pp. 177-185 .
  6. ↑ Watts, DR: Paleomagnetic Determination of the Age of the Serpent Mound Structure . In: Ohio Journal of Science . Volume 104, Issue 4, 2004, pp. 101-108 .

Coordinates: 39 ° 2 ′ 0 ″  N , 83 ° 24 ′ 0 ″  W.