HEAVY MINERAL ANALYSIS OF THE BLUE MESA, SONSELA, AND PETRIFIED FOREST MEMBERS OF THE TRIASSIC CHINLE FORMATION, AZ

The Chinle Formation has been studied for decades in an attempt to figure out the source areas that contributed sediment to the Chinle Basin during the late Triassic period between 226 and 206 Ma. Paleocurrent reconstruction suggests that detritus was coming from the west, south, and east of the Chinle Basin. Detrital zircons have been used as an age constraint to further narrow down the proposed sources, and to reconstruct the paleogeography, but the provenance of the Chinle Formation is not fully understood. A heavy-mineral analysis could help to better constrain the source rocks and help to determine how much influence the sources had on the deposition of the Chinle Formation because heavy minerals can be very sensitive indicators of provenance.

Previous work has shown that the source areas for the Chinle Formation could include the eastern Ouachita Province, Appalachian Mountains, and ancestral Rocky Mountains; the southern Mezoproterozoic granites, Paleoproterozoic metamorphic and pegmatite rocks, Mogollon Highlands; and the western Cordilleran Magmatic Arc.

This study looked at heavy mineral (minerals with a specific gravity greater then 2.8 g/cm3) in the Chinle Formation located in the Petrified Forest National Park, Arizona, to better constrain the source areas and to better understand how they influenced sedimentation. After eliminating diagenetic alteration effects, the heavy-mineral analysis shows that western and southern sources are the primary provenance regions for the Chinle Formation in the Petrified Forest National Park. The Chinle Formation consists primarily of granitic and metamorphic derived minerals, consistent with the minerals in the southern and western sources, and the eastern sources were likely too far away to contribute a significant amount of detritus.