Statistics – Computation
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p34a..08a&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P34A-08
Statistics
Computation
[0545] Computational Geophysics / Modeling, [6240] Planetary Sciences: Solar System Objects / Meteorites And Tektites, [4300] Natural Hazards
Scientific paper
Ejecta from impact craters received a scientific attention not too many years ago, after the revolutionary discovery of the global K-Pg layer and its Ir-anomaly. Impact ejecta are subjected to quick erosion and, hence, are not widely presented on Earth. However, globally distributed ejecta from the largest terrestial craters may be locally preserved even if the crater itself is totally obliterated. The oldest craters on Earth, Vredefort and Sudbury, are ~1.5 Gyr younger than then oldest Archean spherule layers [1-2]. These ejecta layers potentially allow to extract an important information regarding a projectile type/size, the Earth's crust and ocean. Recent numerical modeling of the K-Pg layer [3] successfully reproduced ejecta distribution around the globe including chemical composition, shock metamorphic features, and pressure-temperature history of deposited materials. It has been shown that the main components of global ejecta are projectile and sediments (the uppermost layer of the target), while materials from the crystalline basement represent the minor component and have been transported non-ballistically by atmospheric flows. These results could serve as a benchmark for the modeling of ancient impacts. As the Archean layers are much thicker and the spherules are larger, we can speculate about much larger and more frequent impacts. A few questions should be addressed via numerical modeling: 1) are these ejecta layers proximal layers of relatively small impacts or distal layers of giant impacts; 2) is there any correlation between layers at different locations;.3) why there are no any shocked minerals within these layers; 3) why the composition of spherules is mainly basaltic? In this paper the modeling results are compared with available observations (mainly on K-Pg boundary) and then are extrapolated to much larger impacts. [1] Lowe D.R., Byerly G. R., Asaro F., Kyte F. T. (1989) Science 245:959-962. [2] Simonson, B. M. and B. P. Glass (2004) Annual Review of Earth and Planetary Sciences 32:329-361 [3] Artemieva N. A., Morgan J. (2009) Icarus 201:768-780.
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