Uranium in Igneous Rocks of Central Davis Mountains, West Texas: ABSTRACT

AAPG Bulletin ◽  
1983 ◽  
Vol 67 ◽  
Author(s):  
Wendy E. Schaftenaar, Thomas T. Tie
2009 ◽  
Vol 39 (6) ◽  
pp. 1236-1246 ◽  
Author(s):  
H.M. Poulos ◽  
R.G. Gatewood ◽  
A.E. Camp

While piñon woodlands cover much of arid North America, surprisingly little is known about the role of fire in maintaining piñon forest structure and species composition. The lack of region-specific fire regime data for piñon–juniper woodlands presents a roadblock to managers striving to implement process-based management. This study characterized piñon–juniper fire regimes and forest stand dynamics in Big Bend National Park (BIBE) and the Davis Mountains Preserve of the Nature Conservancy (DMTNC) in west Texas. Mean fire return intervals were 36.5 and 11.2 years for BIBE and DMTNC, respectively. Point fire return intervals were 150 years at BIBE and 75 years at DMTNC. Tree regeneration in west Texas piñon–juniper woodlands occurred historically during favorable climatic conditions following fire years. The presence of multiple fire scars on our fire-scar samples and the multicohort stands of piñon suggested that low intensity fires were common. This study represents one of the few fire-scar-based fire regime studies for piñon–juniper woodlands. Our results differ from other studies in less topographically dissected landscapes that have identified stand-replacing fire as the dominant fire regime for piñon–juniper woodlands. This suggests that mixed-severity fire regimes are typical across southwestern piñon forests, and that topography is an important influence on fire frequency and intensity.


2008 ◽  
Vol 27 (1) ◽  
pp. 113-130
Author(s):  
Richard Francaviglia

In 1895, self-trained mining engineer William K. Gordon, Sr (1862-1949) conducted a geological reconnaissance trip to far West Texas in search of coal deposits. A report from that trip reveals how Gordon's training in geology (acquired largely through reading) and his intrinsic interest in stratigraphy and geomorphology helped him effectively advise the Texas and Pacific Coal Company about the bleak prospects there. In 2005, using Gordon's never-before consulted field report, the author retraced, or rather re-hiked, Gordon's route. Gordon's report features hand-drawn maps and a geological cross-section that were field checked and compared to later data. The author concludes that Gordon enthusiastically, but often inaccurately, described the complex petrology in the rugged, semi-arid Eagle Mountains. Gordon was evidently vexed by how to identify some of the highly varied extrusive igneous rocks here. Nevertheless, Gordon's work should be recognized as the earliest serious geological reconnaissance in a remote area that would much later (1963) be studied in detail by geologists who had at their disposal considerably better tools to analyze the petrology, and possessed a growing awareness of plate tectonics that were unknown in Gordon's time.


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