Spheroidal reduction spots with dark gray bulls-eye centers have been found in the Pierce Canyon Redbeds of Texas and New Mexico. The dark gray center is a concentration of authigenic biotite disseminated between the fibrous crystals of gypsum cement.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.