Internal structure of the Chicxulub Impact crater imaged with magnetotelluric exploration

The magnetotelluric technique allows remote sensing of the Earth's subsurface structure using natural, low frequency radio waves. It measures the electrical resistivity, a parameter that contains information about the lithology and fluid content of subsurface rock units. In January 2001, magnetotelluric (MT) data were collected on two radial profiles across the Chicxulub impact crater in Yucatan, Mexico. Each profile extended from the centre of the crater near Puerto Chicxulub to beyond the cenote ring. The MT data were processed and then combined with data collected in previous years by UNAM. The combined data set was then inverted to give a two-dimensional image of the subsurface resistivity structure of the crater. The following features can be resolved in the subsurface resistivity model.

The Tertiary sedimentary sequence that fills the crater has a resistivity of 1-3 ohm-m and is approximately 2 km deep.

In the basement a zone of high resistivity is imaged from the centre of the impact structure to a radius of approximately 45 km. This high resistivity at shallow depth can be interpreted as uplifted basement rocks of the structural high in the centre of the crater.

Between radial distances of 50 and 70 km is a zone of lower resistivities in the upper 5-10 km of the crust. This coincides with the observed low in the Bouguer gravity anomaly. The coincidence of these two anomalies suggests a common origin. This is most probably due to a region of breccia that exhibits both low electrical resistivity and density.