Field of Science

Petrified Forest National Park Landmarks - Herbert Gregory's "Stump"

The USGS Geologist Herbert E. Gregory formally named and described the Chinle Formation in detail in a 1917 publication titled "Geology of the Navojo Country".  Plate X, figure B of this publication is a photo of a "petrified tree" from Lithodendron Wash, an area which in 1931 would become part of the then Petrified Forest National Monument.  Although later determined by park naturalists not to represent a true standing tree, it was deposited in this position after some transport distance, this specimen looks exactly the same today.  It is in the Black Forest Bed, a prominent tuffaceous sandstone in the Petrified Forest Member of the Chinle Formation and located in a large accumulation of logs called the Black Forest in the Painted Desert portion of the park.  Below is a scan Gregory's published photo as well as a photo of the same specimen taken in 2010.  It is fortunate that Gregory recorded much of his work and travels with photographs.  They provide an excellent account of the geology and people of the Colorado Plateau in the early 20th century.



(From Gregory 1917)


REFERENCE

Gregory, H. E. 1917. Geology of Navajo Country. United States Geological Survey Professional Paper 93, p. 161.

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