10 



MAZOCABPON OEDIPTERNUM 



tions by the Illinois Geological Survey. 

 Details of the mid-continent section 

 have been discussed by Moore (1936). 



Most trustworthy intercontinental cor- 

 relations apparently can be made be- 

 tween the middle Pottsville New River 

 beds and the Westphalian A. For ex- 

 ample, Bertrand (1933, 1935), Moore 

 (1937, p. 671), and D. White (posthum- 

 ous unpublished manuscript recently 

 completed for publication by Charles B. 

 Read) have all suggested that the Na- 

 murian-Westphalian boundary is at 

 least approximately correlative with the 

 Pocahontas-New River boundary in the 

 American Pottsville. The Carboniferous- 

 Permian boundary seems fairly well es- 

 tablished in some areas but is still con- 

 troversial in others. Thus the relative 

 age of the three species of Mazocarpon 

 that are now known can be established 

 approximately, and this is the first step 

 in understanding the phytogeny and in 

 adding to the stratigraphic usefulness 

 of this group of plants. 



Mazocarpon is generally definable only 

 on the basis of petrifactions, and these 

 are most commonly found in Carbon- 

 iferous rocks as fossils in coal-balls. 

 Further investigation of coal-ball fossils 

 will doubtless supplement the somewhat 

 scant information now available as to 

 the occurrence of Mazocarpon and will 

 also provide other fossils of geological 

 and botanical importance. Because of 

 this, and the fact that the relative strati- 

 graphic positions of various coal-ball 

 horizons have commonly been disregard- 

 ed, most of the significant coal-ball 

 horizons of America and Europe have 

 also been indicated on the chart (fig. 1) 

 in their approximate relative positions. 

 A few other horizons, significant in cor- 

 relation or as a source of important 

 plant fossils, also are indicated. 



ILLINOIS COAL-BALL HORIZONS 



Seven coal-ball horizons are now rec- 

 ognized in the Illinois basin, and others 

 will probably be discovered. Two, the 

 Shumway and the Parker, are here re- 

 ported for the first time. 



Coal-balls from the Shumway coal, at 

 the top of the Illinois section, contain 

 chiefly fern material. They differ from 



most other coal-balls in that they are 

 silicified, but since they are entirely in- 

 cluded within a 6- to 10-inch coal bed 

 and show the characteristic type of 

 plant tissue preservation there seems to 

 be no reason why they should not be 

 called "coal-balls". The occurrence is 

 unusual because silicified plant material 

 is not ordinarily found in Illinois coal 

 beds. David White (1925, p. 10) at- 

 tributes the "segregative precipitation 

 of colloidal silica" to rapid invasions 

 of saline or brackish water at the time 

 of, or very soon after, deposition of the 

 plant material. Unfortunately, he did 

 not cite instances which he undoubtedly 

 had in mind, and we have no way of 

 knowing whether the Illinois silicified 

 coal-balls correspond exactly with his 

 interpretation or not. 



The next lower coal-ball occurrence 

 is the Calhoun (Richland County) coal 

 horizon from which the new species de- 

 scribed in this paper, Mazocarpon oedip- 

 termim, was obtained. The Calhoun 

 horizon is in the upper part of the Mc- 

 Leansboro group of Illinois. Recent 

 studies have indicated that the Calhoun 

 horizon is stratigraphically higher than 

 it was previously considered by Newton 

 and Weller (1937). Its relative posi- 

 tion is somewhat uncertain although it 

 is known to be considerably higher than 

 the LaSalle limestone.-^ The limestone 

 that overlies the Calhoun coal bed, and 

 is continuous in a few places with the 

 pockets of coal-ball concretions in the 

 coal bed itself, has been called the Cal- 

 houn limestone by Grogan and Lamar 

 (1940, p. 42). About 800 feet below it 

 is the Herrin (No. 6) coal which marks 

 the top of the Carbondale group in Illi- 

 nois. Feliciano (1924, p. 232) has listed 

 coal-balls from the Calhoun locality as 

 if they were from the Herrin (No. 6) 

 coal, but the Herrin coal is not mined 

 and does not crop out in this part of the 

 State. Miss Reed (1939, pp. 770-771) has 

 stated that the Calhoun coal-balls "are 

 of the same geologic age as those from 

 Harrisburg," but the Harrisburg coal- 

 balls are from the second coal below the 

 Herrin (No. 6) coal, and are thus from 

 the Carbondale group. 



^Weller, J. M., personal communication. 



