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The 1895 discovery of a petrified tree near Clover Creek in south-central Idaho, USA, attracted worldwide attention and resulted in the naming of a new species of ancient oak, Quercinium pliocaenicum Schuster. For more than a century, the discovery has largely been forgotten, even though specimens reside in reputable museums. Reinvestigation of the locality in 2014/2015 resulted in newly-collected specimens and a wealth of new data. Optical microscopy confirms the cellular anatomy used for the original taxonomic study. X-ray diffraction, scanning electron microscopy, energy-dispersive electron spectroscopy, Raman spectroscopy and cathodoluminescence microscopy reveal details of the mineralization, showing the presence of opal-CT as the primary component, with chalcedony as a lesser constituent. This mineralogy suggests petrifaction occurred in at least two stages, beginning with opalization of cellular tissue, leaving open vessels that became filled with chalcedony during a later mineralization episode. Clover Creek oak represents relict flora growing in a wetter climate before the uplift of the Cascade Range created a rain shadow that caused profound desertification of the inland Pacific Northwest. [ABSTRACT FROM AUTHOR]

The 1895 discovery of a petrified tree near Clover Creek in south-central Idaho, USA, attracted worldwide attention and resulted in the naming of a new species of ancient oak, Quercinium pliocaenicum Schuster. For more than a century, the discovery has largely been forgotten, even though specimens reside in reputable museums. Reinvestigation of the locality in 2014/2015 resulted in newly-collected specimens and a wealth of new data. Optical microscopy confirms the cellular anatomy used for the original taxonomic study. X-ray diffraction, scanning electron microscopy, energy-dispersive electron spectroscopy, Raman spectroscopy and cathodoluminescence microscopy reveal details of the mineralization, showing the presence of opal-CT as the primary component, with chalcedony as a lesser constituent. This mineralogy suggests petrifaction occurred in at least two stages, beginning with opalization of cellular tissue, leaving open vessels that became filled with chalcedony during a later mineralization episode. Clover Creek oak represents relict flora growing in a wetter climate before the uplift of the Cascade Range created a rain shadow that caused profound desertification of the inland Pacific Northwest.

Hagerman Fossil Beds National Monument (HAFO), Idaho, is internationally significant for the vertebrate fossils from its hundreds of fossil localities spanning more than a million years of the Pliocene. This study establishes the background for comparisons among localities in the Glenns Ferry Formation within HAFO by describing the nature of the fossiliferous deposits, using published data to revise age estimates for HAFO localities, and relating the relative differences in elevation of the fossil-bearing localities to particular time horizons. Fossils from the anthills and blowout localities are considered to be essentially in situ stratigraphically. Species of modern harvester ants do gather fossils from more than the immediate area, but the maximum vertical movement is probably within the resolution of elevation possible at most HAFO localities. The microstratigraphy of blowout localities is described here for the first time, with vertebrate fossils derived exclusively from layers of about 12-cm thickness. Fossils recovered as surface float should be excluded from stratigraphic comparisons. Based on a combination of paleomagnetic and radioisotopic studies, the maximum age for the top of the Glenns Ferry Formation exposed at HAFO is estimated at 3.11 Ma, and the minimum age for the lowermost exposure is estimated at 4.18 Ma. It is improbable that strata of the Glenns Ferry Formation exist at HAFO that are younger than 3.04 or older than 4.29 Ma. Finally, using marker beds and published stratigraphic sections, the differences in elevation needed to compare localities in the Glenns Ferry Formation at HAFO against a generalized composite section are established. Fossil-bearing sites within this framework can be placed in proper stratigraphic context, and faunal change thereby can be evaluated more precisely. [ABSTRACT FROM AUTHOR]