| Meteorite ablation products from till and ice were recovered from the Mt. Achernar Moraine area of Antarctica. These specimens were studied to characterize the grain size distribution, abundance, chemistry, and petrology of spherules from Antarctica. The bulk composition of spherules and the chemical composition of known meteorite classes were used to devise a classification system for spherules based on discriminant functions analysis. In addition, the pre-atmospheric history of six spherules were modelled, and the exposure history of sandstone clasts on the Mt. Achernar Moraine was determined by using {dollar}rmsp{lcub}10{rcub}Be{dollar} and {dollar}rmsp{lcub}26{rcub}Al{dollar} cosmogenic radionuclides. The exposure history of the moraine allowed an evaluation of the chemical composition of spherules trapped in the moraine sediment through time.; The abundance and grain size distribution indicates that the majority of spherules are below 50 {dollar}murm m{dollar} in size and that there is an average mass of 4.2 {dollar}murm g{dollar} spherules per gram of sediment and {dollar}1.08 times 10sp{lcub}-8{rcub}{dollar} g/g of spherules in the ice. The chemical composition of spherules indicates that most have chemical compositions similar to ordinary chondritic meteorites; however, several spherules were discovered that have compositions unlike chondritic meteorites. These spherules have compositions resembling tektites, but a meteoritic origin cannot entirely be ruled out. The petrologic investigation revealed that spherules are composed of olivine, magnetite, and glass, and they have quenched textures. The textures indicate that cooling rates were on the order of {dollar}2000spcircrm C/hr{dollar} or higher.; A classification system based on the association of spherule chemistry with the chemistry of carbonaceous, ordinary or achondrite meteorites was devised using discriminant function analysis. Unknown spherules can easily by placed into sub-types (SC, SO, or SA) by using the discriminant functions and a discriminant diagram defined by the 386 spherules classified in this study.; {dollar}rmsp{lcub}10{rcub}Be{dollar} and {dollar}rmsp{lcub}26{rcub}Al{dollar} exposure dating of the Mt. Achernar Moraine indicates that it began forming 650 ka. Spherules have been trapped as the sediment accumulated and a record of spherule composition through time has been preserved. The results indicate that a systematic variation in the composition of spherules has occurred over time. |
