|Emory Caldera, Mimbres, New Mexico|
Emory Caldera, Mimbres, New Mexico
The Emory Caldera located in southwest New Mexico has been mapped as a large collapse caldera for many years and I do not expect the geological community to accept the Emory Impact Crater theory without a fight. The discussion about the relevance of the Planar Microstructures in the Cretaceous Bear Tooth (Dakota?) Formation could prove to be very important. First of all are the Planar Microstructures PDF's (Planar Deformation Features) or even Bohm Lamallae. If they are Pm's or PDF's what is their genesis, bolide impact, the explosion that formed the caldera, or were they transported from a shocked terrain and deposited in the Beartooth formation. The Emory Caldera is a giant eliptical caldera some 70 miles across along the long axis which required a very large explosion to have formed and the pressures may have reached high enough levels to have formed PM's or PDF's. There is another possibility the samples of the Beartooth Formation I collected are within the moat area of the Emory Caldera, but they are close to the Hanover Pit of uncertain origin. The Hanover Pit could be the crater of a younger simple impact structure which shocked the adjacent Beartooth Formation. I have some samples of the Beartooth formation taken from the resurgent dome (possible central uplift) near the summit of Emory Peak that could help clear up this argument, but I have not had time to analyze them. In other respects the Emory Caldera is morphologically similar to a complex impact structure containing multiple rings, central uplift, moat, mega breccia and a melt sheet.
Personal communication with Wolfgang E. Elston, and Field excursions to volcanic terranes in the western United States, Volume 1: Southern Rocky Mountain region, 1989, Memoir 46, New Mexico Bureau of Mines and Mineral Resources, Wolfgang E. Elston, Day 5: Field guide to the Emory caldera along NM-152 and in Tierra Blanca Canyon.
The following photomicrographs illustrate some planar and curviplanar microstructures in the Beartooth member of the Cretaceous Dakota? Formation that fit the scale of Planar Deformation Features (PDF's).