Meteor impact ejecta found in England has been shown to have come from the Manicouagan crater in central Quebec. The crater formation and the debris deposition have been both dated to 214 Ma, late Triassic. The age range of biotites in the sediment aligns with the age of those in the Canadian target rock. At the time of the event Quebec and England were closer together than they are today. The Manicouagan impact event is probably not responsible for the 202 Ma end Triassic extinctions.
The ejecta has been found at sites around Wickwar and Churchwood Quarry, a limestone mining operation northeast of Bristol, England. It consists of spherules, shocked quartz, garnet, ilmenite, zircon and biotite.
Our samples came from an exposure discovered in 2016.
A sawcut sample that has not been polished.
The green millimeter and smaller spherules were once impact melt glass and are now clay. Some are hollow and some have been filled (fillings are white).
A partially filled spherule. Field of view is 3 mm wide.
One of several thin sections we had made. Reflected light.
Same thin section. Transmitted white light.
Spherules in thin section. Plane polarized light. Field of view is 3.8 mm wide.
Shocked quartz grain. Cross polarized light. Note uneven extinction. Grain is 0.3 mm long.
Shocked quartz grain 0.25 mm long. XPL.
Shocked quartz grain with planer deformation features, 0.16 mm tall. XPL.
Shocked quartz grain with planer deformation features. XPL.
Shocked quartz grain with planer deformation features. FOV = 0.3 mm. XPL.
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