PALEOENVIRONMENTS OF THE FORT CRITTENDEN FORMATION, SOUTHEAST ARIZONA

The University of Wisconsin-Stevens Point was recently asked by the Arizona Museum of Natural History (AZMNH) to analyze eleven late Cretaceous sedimentary rock samples from the Fort Crittenden Formation in southeastern Arizona for fossil pollen and other palynomorphs. The Fort Crittenden, well-known for its Campanian faunal assemblages, outcrops in the Santa Rita Mountains near Tuscon. In the spring of 2014, researchers affiliated with the AZMNH collected the samples from layers that harbor dinosaur and other vertebrate remains. The Fort Crittenden members are comprised of conglomerates, shales, and sandstones that are interpreted to be freshwater (fluvial and lacustrine) and subaerially-derived valley deposits. Despite ample fossiliferous faunal material and fossilized wood, little is known of the flora or the micropaleontology. To better understand the environments in which these dinosaur remains accumulated, we are using physical and chemical maceration techniques to disaggregate the rock and isolate palynomorphs. Light and scanning electron microscopy are being used for pollen identification. Experimental use of x-ray diffraction to detect cellulose presence will be tested for pollen recognition. Preliminary results show a high degree of sediment oxidation with several possible pollen and non-pollen palynomorphs that may be useful paleoenvironmental indicators.