A Classification of Extraterrestrial Spherules Found in Sedimentary Rocks and Till
Creators:Lougheed, M. S.
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Citation:The Ohio Journal of Science. v66 n3 (May, 1966), 274-283
Extraterrestrial spherules have been recovered from Pleistocene drift and from more ancient sedimentary rocks. Modern deposits also contain spherules, but, because a significant percentage of these spherules can be shown to be of recent terrestrial and industrial origin, such deposits are not dependable sources of extraterrestrial spherules. A classification of extraterrestrial spherules has been developed, based on microscopic observation, which shows a continuous series between two end members. One end member is magnetic and has a luster that varies from bright metallic to black submetallic, probably indicating a composition varying between iron and magnetite. The surface is notably reticulated. The other end member is nonmagnetic and is a generally colorless to amber-colored, transparent glass, probably with a composition varying between those of olivine and pyroxene. The surface is usually smooth, though submicronsized "percussion" marks or micron-sized indentations may be observed on some specimens. These members are referred to as Type I and Type III, respectively. Spherules intermediate between these end members are called Type II.
Author Institution: Department of Geology, Bowling Green State University, Bolwing Green, Ohio
Rights:Reproduction of articles for non-commercial educational or research use granted without request if credit to The Ohio State University and The Ohio Academy of Science is given.
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