Shallow Crustal Structure of Chicxulub Impact Crater Imaged With Seismic, Gravity and Magnetotelluric Data: Structure of the Central Uplift and Origin of the Cenotes Ring.
Abstract
The shallow crustal structure of the onshore portion of the Chicxulub impact structure (Yucatan, Mexico) has been studied with seismic, gravity and MT exploration. A dispersion analysis of Rayleigh waves along a 150-km long, east-west profile allowed to image the shallow Tertiary cover to a depth of 400 m. The thickness of the first layer increases towards the central basin, from less than 100 m immediately outside, to more than 200 m in the terrace zone. The second layer also increases its thickness from about 150 m outside the crater rim, to around 250 m in the vicinity of the rim. At the center of the crater the first layer is again about 100 m thick. The increase in thickness of the first two layers as we approach the sinkhole ring from the exterior of the crater is consistent with the existence of a central basin. The velocity distribution along our profile does not have low-velocity layers. Thus, a low velocity layer observed in the Tertiary cover in a previous study, may be delimited to a ring around the crater center. The inferred inward slope of the two shallow layers immediately outside the central basin correlates with a smooth gravity gradient. A gravity model based in detailed measurements along our profile enable us to associate the fracturing that favored the development of the sink holes at the eastern rim with the ring fracture mapped by offshore seismic line. Finally, preliminary results of ongoing magnetotelluric (MT) studies support the existence of the central structural high.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.S72A1127C
- Keywords:
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- 7218 Lithosphere and upper mantle