ELECTRON-MICROSCOPY AND X-RAY-ANALYSIS OF LACUSTRINE CLAYS FROM THE CHARO CANYON, STATE OF MICHOACAN, MEXICO

In this paper we analyzed by electron microscopy and X-ray diffraction (XRD) the exposed lacustrine clay in a stratigraphic column at Charo Canyon, State of Michoacan, Mexico. Smectite, cristobalite, albite and quartz are the main mineral species in the sediments. Smectite is the most abundant and has a nanometric twinned small particle habit. The low crystallinity of the smectite detected in some of the samples seem s to be associated with instability of the paleohydrological regime in which clayey material was deposited. Iron from underlying volcanic as h is apparently responsible for the iron concentration detected in the smectite structure.