METEOR IMPACT SITE FOR NORTHEASTERN SAN DIEGO COUNTY?

The record of an array of multiple impacts on Jupiter, from the Shoemaker-Levy comet in 1994, suggests that such impact arrays, from comets or meteors, may also be found in the geologic record.

In 2000 Wenk and others (Wenk, Hans-Rudolph, and others, Tectonophysics, v.321, issue 2, 2000) reported outcrops of pseudotachylite distributed over 30 kilometers between Palm Desert and Earthquake Valley. Other authors have reported additional localities, the defining content of each being the presence of pseudotachylite. The age of the pseudotachylite is defined both by stratigraphic position (Abbott, Patrick L. and others, Geology, v. 17, 1989) and by several argon dates (Wenk and others, 2000), all of which fit within the KT boundary ages.

Megabreccias with deformation and possible devitrification, found in the Lusardi formation, may have formed as secondary impact related features. These are found as far as 100 kilometers to the southwest of the possible impact sites.

Although Wenk and others propose an earthquake for the origin of the pseudotachylite, most extremely large meteor and comet impacts generate pseudotachylite (Kenkmann and others, ed., Large Meteor Impacts III, GSA Special Paper 384, 2005).