Gauss’s theorem, mass deficiency at Chicxulub crater (Yucatan, Mexico), and the extinction of the dinosaurs

Campos-Enríquez, J. O.; Morales-Rodríguez, H.F.; Domínguez-Méndez, F.; Birch, Francis

doi:10.1190/1.1444455

Cited by 12 publications

(10 citation statements)

References 35 publications

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“…Our final velocity models are consistent with previous geophysical models, which all contain a 40-50 km-wide dense and/or highly magnetized body [Espindola et al, 1995;Sharpton et al, 1996;Hildebrand et al, 1998;Campos-Enriquez et al, 1998;Pilkington and Hildebrand, 2000;Ebbing et al, 2001] close to the location of the zone of high velocity in Fig. 3 and 4.…”

Section: Discussionsupporting

confidence: 75%

Structural uplift beneath the Chicxulub impact structure

Vermeesch¹,

Morgan²

2008

J. Geophys. Res.

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Models of the central structure of large impact craters are poorly constrained, partly due to the lack of well-preserved terrestrial examples, and partly because of the extreme nature of impact events. Even large impact craters take only a few minutes to form, during which time rocks from the deep crust move upwards many kilometers, interacting with impact melts and breccias before settling to their final position. We construct a new model of central uplift beneath the Chicxulub crater, based upon a well-constrained 3D velocity model, obtained by jointly inverting seismic travel-time and gravity data. The input tomographic dataset has good resolution and many rays cross the central uplift in many directions. We use laboratory measurements to convert between velocity and density. Our velocity model possesses a highvelocity-zone near the crater center, and velocity gradually decreases outside this zone. We use regional refraction data to interpret these velocities in terms of a broad 80-km-wide zone of structural uplift, in which the central rocks originate from the lower crust, and the surrounding rocks from the mid and upper crust. This is in contrast with previous models in 2 2 which the zone of central uplift is either 40-50 km or 150 km wide. Our interpretation is consistent with: scaling laws, Yucatán basement lithology, other velocity data, observations at similar-sized terrestrial craters, and dynamic modeling of peak ring formation. Our model of the uplift at Chicxulub can be used to help distinguish between competing models of effective target strength in numerical models of crater formation.

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Section: Discussionsupporting

confidence: 75%

Structural uplift beneath the Chicxulub impact structure

Vermeesch¹,

Morgan²

2008

J. Geophys. Res.

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“…The first possibility implies a lack of radial symmetry in the velocity structure of the shallow Tertiary cover. An imperfect radial symmetry of the crater can be readily identified in the regional Bouguer anomaly map (De La Fuente et al 1992; Sharpton et al 1993; Campos‐Enríquez et al 1998; Hildebrand et al 1998).…”

Section: Surface Wave Dispersion Analysismentioning

confidence: 99%

Shallow crustal structure of Chicxulub impact crater imaged with seismic, gravity and magnetotelluric data: inferences about the central uplift

Campos-Enríquez

Chávez-García

Cruz

et al. 2004

Geophysical Journal International

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S U M M A R YThe structure of the onshore portion of the Chicxulub impact crater (Yucatan, Mexico) has been studied with seismic, gravity and magnetotelluric (MT) exploration methods. A dispersion analysis of Rayleigh waves along a 150-km long, east-west profile permitted the shallow Tertiary cover to be imaged to a depth of 400 m. Three layers were mapped. The thickness of the first two layers increase as we approach the sinkhole ring from the exterior of the crater (consistent with the existence of a central basin). Those thicknesses change from 100-150 m outside the crater rim to more than 200 m in the terrace zone. At the crater centre, the first layer is again approximately 100 m thick and has a low shear wave velocity (approximately 1 km s −1 ). Its velocity is slightly larger in the rest of the profile. Outside the central basin, we observed a third layer with a shear wave velocity larger than 1.8 km s −1 , but its thickness could not be determined. The velocity distribution along our profile increases monotonously with depth, without low-velocity layers. The inferred inward slope of the two shallow layers immediately outside the central basin correlates well with a smooth gravity gradient. In addition, we present results of detailed gravity measurements along a profile that coincides (in part) with the line covered by the seismic experiment. These gravity measurements were inverted to obtain a density model. In this model (which is of course non-unique), the steep gravity gradients are explained by the faults along which the slumping of the terrace blocks took place. Two of these may correspond to the faults observed at radial distances of 85 and 96 km in offshore seismic data. Finally, we show results obtained using MT soundings. They provide additional, independent constraints on the structure of the Chicxulub crater. MT soundings at the centre of the crater show a sharper increase in resistivity than elsewhere in the impact structure. This sharper increase in resistivity may be related to the uplifted basement of the structural high at a depth of 4 km. Only the MT soundings located over the central gravity high display this feature. Our three different data sets are independently consistent with the existence of a central structural high in the crater and support a twin-peak shape for this high.

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“…With this in mind, there have been numerous geophysical investigations (Camargo-Zanoguera and Suárez-Reynoso 1994;Pilkington et al 1994;Espindola et al 1995;Sharpton et al 1996;Morgan et al 1997Morgan et al , 2000Campos-Enriquez et al 1998;Christeson et al 2001;Ebbing et al 2001), a concerted drilling program by the Universidad Nacional Autónoma de México (UNAM), and most recently, Yax-1 (Fig. 1) has been drilled as part of the International Scientific Drilling Project (ICDP).…”

Section: Introductionmentioning

confidence: 99%

Chicxulub central crater structure: Initial results from physical property measurements and combined velocity and gravity modeling

Vermeesch

Morgan

2004

Meteorit & Planetary Scien

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Abstract-The Chicxulub crater in Mexico is a nearly pristine example of a large impact crater. Its slow burial has left the central impact basin intact, within which there is an apparently uneroded topographic peak ring. Its burial, however, means that we must rely on drill holes and geophysical data to interpret the crater form. Interpretations of crater structures using geophysical data are often guided by numerical modeling and observations at other large terrestrial craters. However, such endeavors are hindered by uncertainties in current numerical models and the lack of any obvious progressive change in structure with increasing crater size. For this reason, proposed structural models across Chicxulub remain divergent, particularly within the central crater region, where the deepest well is only ~1.6 km deep. The shape and precise location of the stratigraphic uplift are disputed. The spatial extent and distribution of the allogenic impact breccias and melt rocks remain unknown, as do the lithological nature of the peak ring and the mechanism for its formation.The objective of our research is to provide a well-constrained 3D structural and lithological model across the central region of the Chicxulub crater that is consistent with combined geophysical data sets and drill core samples. With this in mind, we present initial physical property measurements made on 18 core samples from the Yaxcopoil-1 (Yax-1) drill hole between 400 and 1500 m deep and present a new density model that is in agreement with both the 3D velocity and gravity data. Future collation of petrophysical and geochemical data from Yax-1 core, as well as further seismic surveys and drilling, will allow us to calibrate our geophysical models-assigning a suite of physical properties to each lithology. An accurate 3D model of Chicxulub is critical to our understanding of large craters and to the constraining of the environmental effects of this impact.

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Gauss’s theorem, mass deficiency at Chicxulub crater (Yucatan, Mexico), and the extinction of the dinosaurs

Cited by 12 publications

References 35 publications

Structural uplift beneath the Chicxulub impact structure

Structural uplift beneath the Chicxulub impact structure

Shallow crustal structure of Chicxulub impact crater imaged with seismic, gravity and magnetotelluric data: inferences about the central uplift

Chicxulub central crater structure: Initial results from physical property measurements and combined velocity and gravity modeling

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