Structural uplift beneath the Chicxulub impact structure

Abstract

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.

Ring faults and ring dikes around the Orientale basin on the Moon

“…However, while simple gravity scaling of the diameters of the innermost peak rings suggest they should have comparable structures (D Chicx g Earth /g Moon = 80 km9.8/1.6=490 km; D Orientale,IR = 464 km), important differences exist that caution against a simple comparison. In particular, the central depression of Orientale exhibits an uplift of the crust-mantle interface by 25-30 km, whereas seismic and gravity data from Chicxulub reveal that structural uplift of ~10 km within the peak ring is largely confined to the crust, with only ~2 km of uplift of the crust-mantle interface (Christeson et al, 2009;Vermeesch and Morgan, 2008). This difference between the two basins can likely be ascribed to the difference between the excavation depth relative to the crustal thickness, with Chicxulub excavating only the upper ~1/3 of the crust, and Orientale excavating the majority of the crustal column.…”

Volume 364: Chicxulub: Drilling the K-Pg Impact Crater

“…The acquired seismic data show that the water was deeper and the Mesozoic sediments thicker in the northeast quadrant of the crater than in the other quadrants (Bell et al, 2004;Gulick et al, 2008) and that lateral variation in the target at the impact site might explain the current crater asymmetry (Collins et al, 2008). Velocities and densities of the rocks that form the peak ring are low (Morgan et al, 2000;Vermeesch and Morgan, 2008;Barton et al, 2010), and a high-resolution velocity model obtained using full-waveform inversion ( Figure F4) shows that the uppermost peak ring is formed from about 100-150 m of rocks with low P-wave velocity (3000-3200 m/s) (Morgan et al, 2011). Given the lack of intact peak rings exposed at the Earth's surface, there is no consensus as to either their geologic nature (of what material are they composed and from what stratigraphic location this material originates) or the mode of formation of a peak ring.…”

Candidates for multiple impact craters?: Popigai and Chicxulub as seen by the global high resolution gravitational field model EGM2008

“…The analysis of Espindola et al (1995) did not support more rings. From the most recent papers we recommend Vermeesch and Morgan (2008) and the review with many references (French and Koebert, 2010). Bottke et al (2007) discovered that Chicxulub is a result of an impact of a fragment (of carbonaceous chondrite) from the Baptistina asteroid family, the first such specific identification of an origin among Earth impactors.…”