SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1922. 



ADDITIONS TO THE FLORA 0^ THE WILCOX GROUP. 



By Edward Wilber Berry. 



A rather full account of the extensive flora 

 contained in the lower Eocene strata of the 

 Mississippi embayment which are referred to 

 the Wilcox group was published in 1916. ' At 

 that time it was not possible to obtain sections 

 of the numerous specimens of petrified wood 

 that had been collected from these beds: 

 These woods have since been sectioned and 

 studied, and it seems eminently desirable to 

 place the results of this study on record, for 

 although much of the material had suffered 

 greatly from decay before silicification, some 

 of it is fairly well preserved and shows, among 

 other results, that conifers were individually 

 much more plentiful during Wilcox time than 

 would be inferred from the almost total ab- 

 sence of their foliage in the very large collec- 

 tions of remains of this class that have been 

 studied. 



Moreover, these coniferous woods show well- 

 marked seasonal rings, indicating periodicity 

 in the climate, which can be explained as due 

 either to severity of winters or to a seasonal 

 rainfall and a regularly recurring dry season. 

 As the facies of the flora appears to preclude 

 the first alternative, the second would seem 

 established, except that the general character 

 of the flora is equally opposed to this alter- 

 native. As both the pines and the bald 

 cypress in the existing flora at their southern 

 limit in peninsular Florida show annual rings, 

 it seems to me that a somewhat similar winter 

 season must be predicated for the Wilcox. 

 This does not mean annual snow or frost, al- 

 though freezes may have occurred at intervals 

 of years. Severity is a relative term, and I 

 would not expect the Wilcox climate, even at 

 the north end of the embayment, near the 



i Berry, E. \\\, U. S. Geol. Survey P.rof. Paper 91, 1916. 



present mouth of the Ohio, to have been any 

 more severe during the winter than the present 

 climate, for example, of Fort Pierce, in the 

 southern Indian River region of peninsular 

 Florida. This conclusion is practically the 

 same as that arrived at in the previous analysis 

 of the Wilcox flora. 



Very little has heretofore been known of the 

 Wilcox flora in the Texas area. In Profes- 

 sional Paper 91 Wilcox plants were recorded 

 from 011I3' three localities in Texas, and two of 

 these — Old Port Caddo Landing, in Harrison 

 County, and Sabine River in Sabine County — 

 are in the extreme eastern part of the State. 

 The third and westernmost locality from which 

 Wilcox plants had been recorded is on Calaveras 

 Creek in Wilson County. That the lack of 

 fossils from the Wilcox in the region between 

 San Antonio and the Rio Grande was due en- 

 tirely to lack of exploration was shown by a 

 short trip through this region during 1921. 

 Although fossil plants are not so common there 

 as farther east, because the upper Wilcox, 

 which alone crops out, contains a large propor- 

 tion of sandy beds, long ago recognized as the 

 Carrizo sandstone, several collections were 

 obtained. The age of the Carrizo sandstone 

 has heretofore been somewhat uncertain. Re- 

 ferred originally to the Wilcox, it has been 

 considered to be of Claiborne age by several 

 Texas geologists. The plants found in the 

 Carrizo sandstone, as well as those found both 

 above and below it near the Rio Grande, 

 definitely settle its upper Wilcox age. These 

 will be discussed on a subsequent page. 



In addition, a few collections have been sent 

 to me from tune to time from new localities, and 

 I am particularly indebted to Mr. O. M. Ball for 

 a large collection obtained near Mansfield, La. 



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