Three dimensional gravity field modelling of the Chicxulub impact crater

Details Three dimensional gravity field modelling of the Chicxulub impact crater Three dimensional gravity field modelling of the Chicxulub impact crater

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja....14414h&link_type=abstract

EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #14414

Physics

Geophysics

Scientific paper

Three dimensional gravity field modeling of the Chicxulub crater’s gravity field has refined our working structural model [e.g. 1, 2], and differs somewhat from the results of [3]. The 3D gravity model establishes that the central uplift is within reach of scientific drilling. The 3D gravity modeling method employed is that of [4]. Modelling results particularly reveal the crater’s central structures. The central uplift is a twin peaked structural high with vergence towards the southwest as previously indicated by 2D models [1] and consistent with seismic refraction results [5]. An arm extends towards the northeast, in contrast to the steep gradients that bound the central uplift to the southwest. The width of the uplift at 4 km depth is ~45 km broadening to ~60 km at 5 km depth consistent with 2D modeling. The central uplift rises into the melt sheet to ~2 km depth in contrast to the results of [4] where a top of ~4 km was obtained. However, as refraction results [5] independently constrain the central uplift width and the central uplift density contrast is limited (+0.11gcm-3 here), this is probably a realistic result. The shape of the modeled central uplift is radically different from that advocated by [6] who, based on seismic refraction results, proposed a cup-shaped central uplift (concave top) with a top at ~3 km depth, but of similar width. This interpretation requires substantial departure from density velocity proportionality, and we doubt that the central uplift has an annular top. The filling of the CDC, which we interpret as melt, is revealed as a body slightly elongated in a NE-SW sense with a size consistent with previous 2D model results. With the density contrast measured from the top of the melt sheet, its base lies near ~4 km is obtained consistent with the result of [4]. This depth is dependent upon the density contrast used (-0.15 g/cc), however, and all the mass deficiency need not be melt. The derived melt volume is 1.5 X 104 km3, slightly smaller than that of [4], and in agreement with melt volumes estimated by a variety of methods. [1] Hildebrand, A.R. et al. (1998) in Meteorites: Flux with Time and Impact Effects. Pp. 153-173, Geol. Soc. Lond. Spec. Pub. 140. [2] Pilkington, M. and Hildebrand, A.R. (2000) JGR 105, 23,479 23,491. [3] Ebbing, J. et al. (2001) Planet. &Space Sci. 49, 599-609 [4] Talwani, M. and Ewing, E. (1960) Geophysics, 25, 203 225. [5] Christeson, G.L., 1999, Geol. Soc. Am. Spec. Pap. 339, 291-298. [6] Morgan, J.V. et al., (2002), Geol. Soc. Am. Spec. Pap. 356, 39-46.

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