|Marathon Basin and Caballos Novaculite
Photographs by Steven Schafersman
The Marathon Basin contains rocks of the same age and origin as the Ouachita Tectonic Belt in Arkansas and Oklahoma. The Appalachian Tectonic Belt formed at the same time. Both were a consequence of the tectonic impacting and thrusting of continental plates during the collision of Gondwana (South America and Africa) with Laurentia (North America) to form the super-continent of Pangaea during Late Paleozoic.
A novaculite is a metamorphosed chert. Originally a siliceous deposit (composed of the mineral quartz) formed of deep-water sponge spicules and radiolarians, the siliceous ooze transformed into a chert, and then the high heat and pressure of the Ouachita-Marathon Orogeny transformed the chert into a novaculite. The Caballos Novaculite is the sedimentary- and time-equivalent of the Hot Springs Novaculite from which Arkansas Stone whetstones are made. Harder than steel, novaculite is composed of oriented microscopic crystals of quartz that will easily sharpen a knife blade.
Being composed entirely of quartz, the Caballos Novaculite is a very hard and resistant rock that forms ridge tops and flatirons, all seen below in the photographs. This is a classic area often visited by geology students. The roadcut photos reveal the thin bedding characteristic of deep-water marine deposits. The beds are tilted due to their folding by tectonic mountain-building processes. Many geology textbooks contain photographs identical to some of these.