Chixculub

CHIXCULUB SCIENTIFIC DRILLILNG PROGRAM

The formation of the Chicxulub impact basin approximately 65 million years ago represented one of the most dramatic events in Earth's history since the onset of the Phanerozoic. A 10-15 km diameter comet or asteroid struck the shallow sea over what is now the northern Yucatan and explosively released the energy equivalent to over a hundred million megatons of TNT. While the vast majority of this energy was transferred to near surface materials at the impact site, this collision clearly had global effects distributing a discrete layer of ejected dust, ash, and spherules worldwide at the Cretaceous-Tertiary boundary. Associated with this layer is evidence not only of its impact origin but also of global wildfires, global cooling, acid rain, and widespread extinctions in the oceans and on the continental landmasses.

The extinction event initiated by this cosmic collision marks the end of the Mesozoic Era and is one of the most profound excursions in biological evolution since the inception of life on Earth. The terrestrial production rate of craters such as Chicxulub, whose diameter exceeds 200 km, is less than one per 100 million years and, to date, only two others have been recognized. These are the Sudbury (Ontario, Canada) and the Vredefort (South Africa) structures; both are nearly 2 billion years old, heavily eroded and tectonically modified. Chicxulub, on the other hand, is relatively young and because it formed in an area of active deposition (a shallow sea over a stable carbonate platform), its interior morphology has been shielded from the effects of erosion.

Chicxulub, therefore, offers a unique opportunity to gather new and important information on the nature of such large multiring impact basins and to determine how their formation affected geological and biological evolution.

DOSECC, under contract to the International Continental Scientific Drilling Program (ICDP), provided coring services for the collection of continuous core from a drill site near Merida, Mexico. In late 2000 and early 2001, drilling took place using the DOSECC Hybrid Coring System. Continuous core samples were collected from 250m to 1511m. These cores sampled the basal Tertiary sequences, the epiclastic transition from impact rocks to Tertiary carbonates and the underlying impact breccias. Analysis of the core is presently underway, and few results have been released at this time.

More Information on the Chixculub Impact Structure:

33rd International Geological Congress
6–14 August 2008
Oslo, Norway

IRIS Real-Time Earthquake Map

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