Petrographic analysis reveals diagnostic planar deformation features in Loftarsten quartz grains, confirming that the Lockne structure originated from a Middle Ordovician marine impact crater.
Microscopic planar deformation features (PDFs) in quartz grains are diagnostic of shock meta‐morphism during hypervelocity impact cratering. Measurements of the poles of sets of PDFs and the optic axis of 25 quartz grains were carried out for a sample of the Loftarsten deposit from the Lockne area, Sweden. The most abundant PDFs observed in the sample from the Lockne area correspond to those found at known impact craters (i.e., ω (10 13} and π (10 12). This study confirms the previous suggestion that the Lockne structure is an impact crater. The Loftarsten is, therefore, interpreted as the final stage of resurge deposition after a marine impact at Lockne in the Middle Ordovician.
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Therriault et al. (1995) studied this question.
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