Multiring-forming large bolide impacts and evolution of planetary surfaces

Abstract

In the past few years, meteoritic and cometary impacts have emerged as a major geological agent in the construction and evolution of planetary surfaces. Formation of complex central ring, peak ring and multiring craters involves excavation and melting of large volumes of crustal material. High-resolution geophysical mapping measuring gravity, magnetics, and topography of the Moon and Mars have recently provided information on the subsurface structure of large basins and aided in identifying buried giant craters. The terrestrial crater record has been significantly erased by tectonic, magmatic, and erosion processes and only a small proportion of impact structures remain. Record of multiring craters is limited to three examples: Vredefort, Sudbury and Chicxulub. Deep geophysical surveys and geochemical and isotopic studies of those craters provide means to evaluate the influence of large impacts on the lithospheric and crustal evolution by providing estimates of excavation depth and volume, amounts of material fragmented, ejected, vaporized and melted, and effects on the crustal stratigraphy and crustal thickness. Analyses on the melt from Vredefort, Sudbury, and Chicxulub indicate andesitic composition derived from lower-crustal material. The melt formed inside the lower transient cavity from lower crustal material that was then redistributed and emplaced in upper-crustal levels, resulting in crustal redistribution. Crystalline basement clasts fragmented and incorporated into the breccias show varying degrees of alteration but no significant thermal effects. Ejecta were deposited locally within the crater region and ballistic material and fine ejecta are globally distributed on the planetary surface. Impacts influence the crust-mantle boundary, with Moho uplift. Material from the mantle was not incorporated into the melt and impact breccias, indicating that the excavation cavities were confined to the lower crust. This is also apparently the case for the giant basins on the Moon, including the 2500 km diameter South Pole-Aitken Basin. Considering the numbers of large multiring basins, possible flux of large impacts, and effects on target surfaces, crustal scale redistribution of material during those large impacts has played a major role in the evolution of planetary surfaces.

The Chicxulub multi-ring impact crater, Yucatan carbonate platform, Gulf of Mexico

“…The geological and geomorphological characteristics Figure 22. Schematic model for crater formation processes in large multi-ring structures (adapted from Melosh, 1989;Gulick et al, 2008;Urrutia-Fucugauchi and Pérez-Cruz, 2009). Crater formation of large complex structures inveves several stages, from initial contact, compression, excavation of transient cavity, basement aplift and modification.…”

Planetary Sciences, Geodynamics, Impacts, Mass Extinctions, and Evolution: Developments and Interconnections

“…Large impacts produce deep transient excavation cavities in the curst, fragmenting and removing large volumes of rock and redistributing crustal material. On Earth, the active tectonic environment and erosion have effectively erased the record of impacts, with a relatively small number of craters documented and only three large multiring basins [39]. The Chicxulub crater, with a ∼200 km rim diameter formed at the K/Pg boundary, is the youngest of the multiring basins and the only one with the ejecta preserved [26,27,29].…”

“…Analysis of frequency, density, and size distribution of craters permits estimating the age of the planetary surfaces, with ancient surfaces marked by high density of craters, often including the large multiring basins [39]. The size-frequency crater relationships are also related to the geodynamics and deep structure.…”

Chicxulub crater post-impact hydrothermal activity - evidence from Paleocene carbonates in the Santa Elena borehole

“…Craters formed on continental shelf settings like Sudbury, Chicxulub, Siljan, Ries, Puckezh-Kantunki, Kara and others present evidence of hydrothermal alteration in the impact lithologies. The fluid circulation appears related to permeability, porosity, fracturing and crater morphology (e.g., Melosh, 1989;Kring, 2004, Urrutia-Fucugauchi andPerez-Cruz, 2009). Study of hydrothermal systems in geologic settings with sedimentary, igneous and metamorphic rocks in addition to the impact lithologies is a complex task.…”