Lower Ordovician Fillmore Formation

Millard County, Utah

Folks attending a field trip to the Great Basin district find welcomed shade from an exposure of the lower Ordovician Wah Wah Limestone (third-oldest member of the Pogonip Group) in western Millard County, Utah, a number of miles east of the eastern border of White Pine County, Nevada. Silicified trilobites, algae-sponge patch reefs, conodonts (a minute feeding apparatus, unrelated to modern jaws, from an extinct eel-like organism--seen only in the insoluble residues of carbonates dissolved in a dilute solution of acetic or formic acid), graptolites, gastropods, brachiopods, solitary sponges, nautiloid cephalopods, and cystoid echinoderms constitute members of a large and diverse fossil assemblage from the Wah Wah. Photograph courtesy Dave Smith; I edited and processed the image through photoshop.

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