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Letters to Nature
Nature 376, 415 - 417 (03 August 2002); doi:10.1038/376415a0

Size and structure of the Chicxulub crater revealed by horizontal gravity gradients and cenotes

A. R. Hildebrand*, M.  Pilkington*, M. Connors, C. Ortiz-Aleman & R. E. Chavez

* Geological Survey of Canada, 1 Observatory Crescent, Ottawa, Ontario K1A OY3, Canada
Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
Institute de Geofisica, Ciudad Universitaria, Delgacion de Coyoacan, Codigo 04510, Mexico DF, Mexico.

IT is now widely believed that a large impact occurred on the Earth at the end of the Cretaceous period, and that the buried Chicxulub structure in Yucatán, Mexico, is the resulting crater24. Knowledge of the size and internal structure of the Chicxulub crater is necessary for quantifying the effects of the impact on the Cretaceous environment. Although much information bearing on the crater's structure is available, diameter estimates range from 170 to 300 km (refs 1á¤-7), corresponding to an order of magnitude variation in impact energy. Here we show the diameter of the crater to be ˜180 km by examining the horizontal gradient of the Bouguer gravity anomaly over the structure. This size is confirmed by the distribution of karst features in the Yucatan region (mainly water-filled sinkholes, known as cenotes). The coincidence of cenotes and peripheral gravity-gradient maxima suggests that cenote formation is closely related to the presence of slump faults near the crater rim.

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