Chicxulub impact: The origin of reservoir and seal facies in the southeastern Mexico oil fields

Stratigraphic and mineralogic studies of Cretaceous-Tertiary (K-T) boundary sections demonstrate that the offshore oil-producing breccias and seals fr om oil fields in the Campeche marine platform are of K-T boundary age and t hat their mode of formation is probably related to the K-T impact event at Chicxulub. The oil-producing carbonate breccia and the overlying dolomitize d ejecta layer (seal) found in several wells on the Campeche marine platfor m contain typical Chicxulub impact products, such as shocked quartz and pla gioclase, and altered glass. These offshore units are correlated with thick (similar to 50-300 m) onshore breccia and impact ejecta layers found at th e K-T boundary in the Guayal (Tabasco) and Bochil (Chiapas) sections. Regio nally the characteristic sequence is composed of, from base to top, coarse- grained carbonate breccia covered by an ejecta bed and typical K-T boundary clay. The onshore and offshore breccia sequences are Likely to have result ed from major slumping of the carbonate platform margin triggered by the Ch icxulub impact. Successive arrival times in this area, similar to 350-600 k m from the crater, of seismic shaking, ballistic ejecta, and tsunami waves fit the observed stratigraphic sequence. The K-T breccia reservoir and seal ejecta layer of the Cantarell oil held, with a current daily production of 1.3 million barrels of oil, are probably the most important known oil-prod ucing units related to an impact event.