Lower Ordovician House Limestone

Millard County, Utah

A Great Basin paleontology field trip participant (lower right) inspects the lower Ordovocian House Limestone (oldest member of the Pogonip Group) in western Millard County, a number of miles east of the eastern border of White Pine County, Nevada. The House yields conodonts (minute parts of a unique feeding apparatus, unrelated to modern jaws, from an extinct lamprey eel-like animal), in addition to ledges of silicified (replaced by the mineral silicon dioxide) trilobites and brachiopods. Photograph courtesy Dave Smith; I edited and processed the image through photoshop.

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