312 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 9 



tree rings by archeologists in dating ancient pueblos in New Mexico 

 and Arizona, In this way the geologists obtain extremely accurate 

 data for mapping structure on the surface and in core drilling. 



An investigation by N. W. Bass (1, 2) and his coworkers of the 

 shoestring sand bodies that yield much petroleum in Greenwood and 

 Butler Counties, Kans., and Osage County, Okla., has shown that 

 these elongated lenticular sand bodies represent sand bars along an- 

 cient shore lines during the Pennsylvania epoch. A study of 22,000 

 well logs in and near the oil fields supplemented by an investigation 

 of nearly the full length of the Atlantic and Gulf coasts has made 

 possible the mapping of land features and shore lines of the ancient 

 seas as they existed in Kansas and Oklahoma 250 million years ago. 



The recognition and determination of changes in facies of sedi- 

 ments occupy the attention of all stratigraphic geologists. Many 

 such changes may be noted in the exposed rock strata, as in the 

 Permian section of Utah and in the Cretaceous section of the Book 

 Cliffs of Colorado and Utah. The most striking and best-known 

 example of such facies changes in this country is offered by the 

 Permian rocks of the Delaware Basin of New Mexico and Texas. 

 The basin was surrounded by a reef zone, and this in turn by a back 

 reef zone. Each of these — the basin and the two zones — is character- 

 ized by different kinds of deposits. These relations are exceptionally 

 well displayed in the Glass and Guadalupe Mountains and also by 

 the records of thousands of oil wells in the plains east of the 

 mountains. 



Stratigraphic information and also areal geologic maps have been 

 contributed generously by oil companies to State and Federal Geo- 

 logical Surveys for use in connection with official investigations in the 

 petroleum-producing States. The publication of such modern State 

 geologic maps as those of Oklahoma (11), Kansas (12), and Texas 

 (4) was greatly facilitated through the active interest and support 

 of the petroleum geologists and companies in those States. The 

 great stock of information acquired by oil companies in California 

 has been drawn upon in large measure in the preparation of two 

 recently issued volumes — one entitled "Geology of California," by 

 K. D. Reed (15), and the other "Structural Evolution of Southern 

 California," by E. D. Reed and J. S. Hollister (16). 



The stratigraphic information supplied by the wells drilled for oil 

 and gas enables the geologist to draw geologic maps of the past. 

 Such maps are areal geologic maps and they thus differ from paleo- 

 geographic maps which show the distribution of land and water. 

 An early, and perhaps the first, aerial geologic map based almost 

 entirely on well data was one for northeastern Oklahoma compiled 

 by Luther H. White. It was published in 1926 by the Oil and Gas 

 Journal (23) and also by the Oklahoma Geological Survey (23). 



