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Title: Understanding the genesis and emplacement of impact ejecta : from proximal to distal
Author: Thackrey, Scott Neil David
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2010
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Impact ejecta material is produced during every significant impact event in our Solar System. Bodies that possess an atmosphere and sub‐surface volatiles produce unique morphologies of ejecta that are not observed on bodies that are devoid of these properties. Recent advancements in planetary exploration have lead to an explosion in research of cratering processes on Mars and other planets. However, the enthusiasm to interpret distant worlds has led many to neglect the areas of impact processes that are still to be fully understood on Earth. In doing so, interpretations of impact ejecta processes on other planets have been based on untested models. I present here extensive research that has set out to test the validity of published models of impact ejecta processes (both distal and proximal) by critically comparing them to actual geological observations. To achieve this I have developed new techniques, conducted various detailed laboratory and field investigations, and report for the first time the discovery of 2 new layered ejecta deposits. The results of this study have shown that published models for the genesis of proximal layered ejecta deposits are flawed. I suggest an alternative model based on geological observations showing that the morphologies of proximal layered ejecta deposits are controlled by identical processes (although on a larger scale) that occur in the volcaniclastic environment. I also state that both sub‐surface volatiles (in the form of water) and atmospheric interaction play vital roles in their development. Through the analysis of the Manicouagan impact crater and its associated distal ejecta deposit I have been able to prove, for the first time, the spatial origins of distal impact ejecta showing that it is derived from the top 1/3 of the target sequence. In doing so, the research presented also quantifies the actual amount of erosion that has occurred since the formation of the Manicouagan impact structure (>3.5 km) and that distal impact ejecta without a preserved melt component can still be successfully correlated to a crater through heavy mineral correlation techniques.
Supervisor: Not available Sponsor: University of Aberdeen ; College of Physical Sciences
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Impact craters