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THE FOSSIL FORESTS OF THE YELLOWSTONE 

 NATIONAL PARK. 



By F. PI. Knoavltox, 



United fates (reoJor/Jcal Survey. 

 INTRODUCTION. 



Isolated pieces of fossil wood are of comparatively common and 

 Avidespread occurrence, especially in the more recent geological de- 

 posits of the West. Not infrequently scattered logs, stumps, and 

 roots of petrified or lignitized trees are brought to light, but only 

 exceptionally are they so massed and aggregated as to be worthy of 

 the designation of fossil forests. Examples of such are the celebrated 

 fossil forests of relatively late geological age near Cairo, Eg^q:)t, 

 the huge prostrate trunks in the Napa Valley near Calistoga, Cal., 

 and the geologically much older and far more extensive forests now 

 Avidely knoAvn as the Petrified Forest National Monument in Apache 

 County, Ariz. But in many respects the most remarkable fossil 

 forests known are those noAV to be described in the Yellowstone 

 National Park. In the forests first mentioned the trunks and logs 

 Avere all prostrated before fossilization, and it is perhaps not quite 

 correct to designate such aggregations as veritable fossil forests, 

 though they usually are so called. In the fossil forests of Arizona, 

 for example, which are scattered over many square miles of Avhat is 

 noAv almost desert, all the trunks shoAV evidence of having been 

 transported from a distance before they Avere turned to stone. Most 

 of them are not even in the position in which they were originally 

 entombed, but haA^e been eroded from slightly higher horizons and 

 haAx rolled in the greatest profusion to loAver levels. As one a icAvs 

 these Arizona forests from a little distance, Avith their hundreds, 

 even thousands, of segments of logs, it is difficult to realize that they 

 are really turned to stone and are noAV exhumed from the eartli. 

 The appearance they present (see fig. 1) is not unlike a " log drive 

 that has been stranded by the receding waters and left until the bark 

 had disappeared and many logs had fallen into partial decay. 

 Trunks of many sizes and lengths are now mingled and scattered 

 about in the wildest profusion, and the surface of the ground is car- 

 peted with fragments of Avood that have been splintered and broken 

 from them. In the Yellowstone National Park, however, most of 



