Science & Engineering Faculty

The micrometeorite flux in the Albian–Aptian age (ca. 103–117 Ma): A search for Tycho ejecta in pelagic sediments using chrome spinels

Publication Date Jun 21, 2022


ABSTRACT Numerical models of meteorite delivery from impacts on the Moon have demonstrated that the impact event forming the lunar crater Tycho (~85 km diameter; ca. 109 Ma age) would have delivered considerable amounts of ejected material to Earth. The ejecta, containing lunar Ti- and V-rich chrome spinels, would have been distributed globally and admixed with seafloor sediments over a few meters of a typical marine stratigraphic interval. In order to locate such ejecta, samples weighing ~12–25 kg each, with one-meter spacing were extracted over an ~30 m interval of the deep-sea formed Calera Limestone, Albian and Aptian age (ca. 103–117 Ma), from the Pacifica Quarry, south of San Francisco. The limestone samples were leached in acids and residues searched for possible lunar Ti-rich chrome-spinel grains. In a total of 689 kg of limestone, 1154 chrome-spinel grains were found. Of these, 319 contain >0.45 wt% V2O3, of which 227 originate from equilibrated ordinary chondrites. The majority of the other 92 grains with >0.45 wt% V2O3 are most likely from different types of achondritic meteorites. Among these, we found eleven particularly Ti-rich chrome-spinel grains. The elemental abundances of these grains were compared with chrome spinel from lunar, howardite-eucrite-diogenite (HED) and R-chondritic meteorites. This showed that only one of these grains could potentially be of lunar origin. The bulk of the other grains likely originate from HED meteorites based on oxygen isotopic anal...


Chrome-spinel Grains Chrome Spinel Howardite-eucrite-diogenite Kg Of Limestone Aptian Strata Similar Grains Seafloor Sediments Limestone Samples Aptian Age Impact Event

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No potential conflict of interest was reported by the authors. The conception and design of the study, acquisition of data, analysis and interpretatio...

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