Papers by Robert Beauford
The study of terrestrial meteorite impact craters and of impacted meteorites expands our understa... more The study of terrestrial meteorite impact craters and of impacted meteorites expands our understanding of cratered rocky surfaces throughout the solar system. Terrestrial craters uniquely expand upon data from remote imaging and planetary surface exploration by providing analogs for understanding the buried sub-surface portions of impact structures, while impacted meteorites provide examples of a much wider range of surface and subsurface impactite materials than we can directly sample thus far through solar system exploration. This report examines three facets of the impact record preserved in terrestrial impact craters and in meteorites. First, it looks at the macroscopic structure of the Sutters Mill meteorite, a brecciated regolithic CM chondrite that preserves a three-dimensional record of the one of the most primitive known impact gardened surfaces in the solar system. The report details distinct lithologies preserved in the meteorite and the ways in which these lithologies reflect impact and alteration processes, with the intention of contextualizing and illuminating the wider body of recently published instrumental work on the stone by the current authors and others. Second, this dissertation presents a detailed analysis of the origin and nature of unique sub-spherical 'round rocks' commonly associated with the surface exposed sediments at the proposed Weaubleau impact structure, in west-central Missouri. Third, and finally, the dissertation looks at the nature of impact evidence for small impact pits and craters on earth. Unambiguously proving the impact origin of sub-kilometer terrestrial impact craters has presented significant historical challenges. A systematic analysis of field reports for all widely recognized sub-km terrestrial craters addresses both the nature of compelling evidence for impact origin for structures in this size range and the adequacy of the existing record of evidence for currently recognized structures.
Lithologic variation in the Sutter’s Mill CM chondrite records precursor materials and surface pr... more Lithologic variation in the Sutter’s Mill CM chondrite records precursor materials and surface processes that contributed to regolith formation.
The Crooked Creek and Decaturville, Missouri, impact craters offer an opportunity to understand v... more The Crooked Creek and Decaturville, Missouri, impact craters offer an opportunity to understand variation in impactite lithologies in carbonate and mixed sedimentary environments. Impactites involve mixes of carbonates, sandstone, chert, and shale.
The Sutter’s Mill CM chondrite offers constraints on timing and insights into context of fine-gra... more The Sutter’s Mill CM chondrite offers constraints on timing and insights into context of fine-grained rim formation.
Photographs and photomicrographs of 11 slices of a 5.1 gram Sutter"s Mill individual suggest... more Photographs and photomicrographs of 11 slices of a 5.1 gram Sutter"s Mill individual suggest a complex history on the impact plowed surface of a volatile rich body.
Epigenetic hydrothermal mineralization, subsequent to the Crooked Creek and Decaturville impacts,... more Epigenetic hydrothermal mineralization, subsequent to the Crooked Creek and Decaturville impacts, accompanied Paleozoic dolomitization of carbonates at a regional scale in the Ozarks and produced quantities of ferrous minerals at both locations.
An examination of what can be learned from 197 "meteorwrong" samples and letters receiv... more An examination of what can be learned from 197 "meteorwrong" samples and letters received and handled by university students and professors.
ABSTRACT Evaluation of digital elevation models and rock samples justifies tentative consideratio... more ABSTRACT Evaluation of digital elevation models and rock samples justifies tentative consideration of Missouri's Belton Structure as a possible impact crater.
Science, 2012
The Meteor That Fell to Earth In April 2012, a meteor was witnessed over the Sierra Nevada Mounta... more The Meteor That Fell to Earth In April 2012, a meteor was witnessed over the Sierra Nevada Mountains in California. Jenniskens et al. (p. 1583 ) used a combination of photographic and video images of the fireball coupled with Doppler weather radar images to facilitate the rapid recovery of meteorite fragments. A comprehensive analysis of some of these fragments shows that the Sutter's Mill meteorite represents a new type of carbonaceous chondrite, a rare and primitive class of meteorites that contain clues to the origin and evolution of primitive materials in the solar system. The unexpected and complex nature of the fragments suggests that the surfaces of C-class asteroids, the presumed parent bodies of carbonaceous chondrites, are more complex than previously assumed.
Meteoritics & Planetary Science, 2014
ABSTRACT A piece of the Sutter's Mill meteorite, fragment SM2-1d, has been examined using... more ABSTRACT A piece of the Sutter's Mill meteorite, fragment SM2-1d, has been examined using thermoluminescence techniques to better understand its thermal and metamorphic history. The sample had very weak but easily measureable natural and induced thermoluminescence (TL) signals; the signal-to-noise ratio was better than 10. The natural TL was restricted to the high-temperature regions of the glow curve suggesting that the meteorite had been heated to approximately 300 °C within the time it takes for the TL signal to recover from a heating event, probably within the last 105 years. It is possible that this reflects heating during release from the parent body, close passage by the Sun, or heating during atmospheric passage. Of these three options, the least likely is the first, but the other possibilities are equally likely. It seems that temperatures of approximately 300 °C reached 5 or 6 mm into the meteorite, so that all but one of the small Sutter's Mill stones have been heated. The Dhajala normalized induced TL signal for SM2-1d is comparable to that of type 3.0 chondrites and is unlike normal CM chondrites, the class it most closely resembles, which do not have detectable TL sensitivity. The shape of the induced TL curve is comparable to other low-type ordinary, CV, and CO chondrites, in that it has a broad hummocky structure, but does not resemble any of them in detail. This suggests that Sutter's Mill is a unique, low-petrographic–type (3.0) chondrite.
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Papers by Robert Beauford