Millennial-scale VML Dating of Arizona Meteor Crater, Western USA


Figure Caption:   VML dating of a meteor impact event in northern Arizona. (A) Barringer Meteor Crater. (B) Sampled eject block on the east rim of the crater. (C) and (D) Visual microstratigraphies uncovered in varnish from the meteor impact-ejected rock block in (B) display two oldest layering sequences of LU-1/.../LU-4 (WP5c), yielding a minimum-limiting VML age estimate of 49.15 ka for the cratering event, closely matching the TL age 49±3 ka and slightly younger than the recently revised cosmogenic 36Cl age of 56.0±2.4 ka (Sutton, 1985; Marrero et al., 2010). (E) A meteor impact-produced layer of melt silica about 50-μm thick underneath the varnish formation, indicating zero erosion of the sampled ejecta face and thus the oldest possible varnish formed on it (cf. Liu and Broecker, 2013).


 

VML Dating of Boxhole Meteor Crater in Northern Territory, Australia


Figure Caption:   VML dating of Boxhole meteor crater in Northern Territory, Australia. Visual microstratigraphy uncovered in varnish from the meteor crater displays the oldest layering sequence of LU-1/.../LU-4 (WP3), yielding a minimum-limiting VML age estimate of 30 ka (if the radiometrically calibrated and climatically correlated varnish layering sequence in the drylands of western USA is tentatively assumed). This age estimate is consistent with the previously reported cosmogenic 10Be/26Al surface exposure age of ~ 30 ka for the crater (Shoemaker et al., 1990).