Chicxulub crater stratigraphy

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The Chicxulub crater is a subsurface basin, 180 km in diameter on the northwestern Yucatan Peninsula of Mexico. It is thought to be the result of an asteroid impact approximately 66 Ma., dating at approximately the same time as the Cretaceous-Paleogene (K/T) extinction event. The impact crater formed a basin that allowed sediment deposition and digenesis to occur throughout the Cenozoic Era. Seismic images describe the crater as a circle of peak rings and annular troughs within a large depression of underlying melt and impact breccias. Tektites, shocked quartz and high traces of iridium have also been found along the K/T boundary in areas surrounding the basin.

Post-impact deposition

Horizons along the Chicxulub basin

During the Paleocene immediately following the impact, shallow-water deposition of pelagic sediment began to infill the basin. A prograding shelf sequence downlaps onto the unconformity in the eastern annular trough. Early to middle Eocene sedimentation occurred in shallow-water.

Clinoform packages suggest a marine regression occurred with sedimentation decreasing in the western trough. Deposition of carbonate and evaporites resulted from subaerial exposure of the carbonate platform. Chaotic reflectors in the seismic images can be interpreted as mass flow deposits during a regression. Using dates obtained from well data, the western and northwestern basins were filled entirely by 40 Ma.

During the Late Eocene to Early Oligocene, the exposed surface underwent freshwater diagenesis which led to extensive dolomitization. Sparse reef growth developed within a shallow platform until the early Miocene. From the middle Miocene through Pleistocene, restricted water deposits filled the basin to its current flat surface. Subaerial exposure and freshwater diagenesis led to replacive dolomite and karsting. The perimeter of the crater can be identified by cenotes at the surface.

See also

[1]Extinction

References

  1. Barton, P.J., Christeson, G.L., Grieve, R.A.F., Gulick, S.P.S., Morgan, J.V., Urrutia-Fucugauchi, J. (2013) Geophysical characterization of the Chicxulub impact crater. Retrieved from https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/rog.20007
  2. Bell, C., Hampson, G.J., Morgan, J.V., Trudgill, B. (2004) Stratigraphic and sedimentological observations from seismic data across the Chicxulub impact basin. Retrieved from https://onlinelibrary-wiley-com.ezproxy.lib.uh.edu/doi/epdf/10.1111/j.1945-5100.2004.tb01130.x
  3. Lefticariu, L., Lefticariu, M., Perry, E.C., Ward, W.C. (2006) Post-Chicxulub depositional and diagenetic history of the northwestern Yucatan Peninsula, Mexico. Retrieved from https://www-sciencedirect-com.ezproxy.lib.uh.edu/science/article/pii/S0037073805003118

External links