LITHOLOGIC CORRELATION IN ' BEND SERIES, TEXAS. 



one of which has been offered by Waite and 

 l^dden," who suggest that the sulphide is due 

 to mineraUzation after deposition, made possi- 

 ble by the porosity of the sandy beds. Though 

 some of the sulphide I found in the coarse, gen- 

 erally more or less sandy basal beds may have 

 been introduced in this way, I am inclined to 

 believe that most of it is formed syngenetically 

 as a product of the same large amounts of de- 

 caying organic matter that probably caused the 

 formation of ghiuconite. This close relation 

 between glauconite and sulphide has been rec- 

 ognized in modern deposits.' The occurrence 

 of sulphide in the glauconitic beds encoun- 

 tered in the two wells here considered appears 

 to be independent of the porosity of the beds. 

 So far as mere impressions can be relied on, the 

 sulphide seems to be as abundant in the dense, 

 argillaceous phases of these beds as in the open, 

 sandy phases. Then, too, it is m several occur- 

 rences associated closely with the shells in the 

 beds, filling the tissues of some of them. 



On the other hand, I gained the impression 

 that chertification was rather more extensive 

 in some of these coarse basal beds than in beds 

 that lay adjacent to them, a difference which 

 may indicate effects due to circidation, though 

 it may be due merely to the abimdance of 

 coarse calcareous fragments in these beds. If 

 due to circulation, this supports the interpre- 

 tation of Waite and Udden, though it conflicts 

 with their observations. Probably the beds 

 contain both syngenetic and epigenetic sul- 

 phide, and though it may be difficult to dis- 

 tinguish these two types a possible means of 

 discrimination may be foimd in the fact that 

 the snUphide found in material from these wells 

 appears to occur in two forms, one minutely 

 spheroidal, generally gathered into large con- 

 cretions, the other having sharp crystal faces. 

 These forms may be respectively syngenetic 

 and epigenetic. The problem deserves study, 

 as the differentiation of syngenetic and epige- 

 netic sulphide would help to thi'ow light on the 

 processes of circulation in the rocks. 



The classification of tne beddmg planes that 

 are overlain by glauc;onite and that mark the 

 boundaries of the units diflerentiated in this 



' Waite, V. v., and Udden, J. .\., Observations on the Bend in Bough 

 No. 1 in Brown County: Am. Assoc. Petr. Geologists Bull., vol. 3, p. 

 33S, 1919. 



' Collet, L. W., Les depots marins, especially pj). 16S-1T2, Paris, Octave 

 Doin, 1908. 



paper or the determination of their significance 

 as compared with other bedding planes must, 

 I believe, be postponed until many more ob- 

 servations on this subject have been made. 

 Every bedding plane represents a break in 

 sedimentation and is related by a series of 

 innumerable intermediate types to universally 

 recognized "disconformities" and finally to un- 

 conformities. Barren's analysis of stratigraphic 

 breaks' is very Uluminatmg, but their pos- 

 sible causes seem to me so numerous and their 

 possible relations so complex that, until more 

 detailed study has given better ground for dif- 

 ferentiation, I prefer to call the boundaries I 

 have indicated merely stratigniphic breaks, 

 ^\^thout attempting to define the relative order 

 of magnitude of the time intervals they repre- 

 sent. Tha t they are at least " disconformities " 

 of order B-B in Barrell's system ^ is, I think, 

 unquestionable. In the accompanying plate I 

 have used the wavy line that is generally re- 

 gai-ded as symbolizing an unconformity merely 

 because it emphasizes the breaks, \vithout wish- 

 ing thereby to indicate their significance. 



For the same reason that no more specific 

 name has been given to the stratigraphic 

 breaks, the portions of the section separated by 

 the breaks have been called merely strati- 

 graphic units, without an attempt to determine 

 whether they are of the order of members, 

 formations, series, gi'oups, or any other recog- 

 nized subdivisions. Their variation in lith- 

 ology and the recognition of most of them so 

 far only underground makes it seem preferable 

 to identify them merely by letters rather than 

 by names. 



LOCATION OF WELLS EXAMINED. 



In order to give the method adopted for this 

 investigation a thorough test it was desirable 

 that the wells studied should be far apart and 

 that the samples from then^. should represent a- 

 nearly complete section of the "Bend series." 

 In the collections available in the office of the 

 United States Geological Survey these require- 

 ments seemed to be fulfilled by sami>les from 

 two wells of the Roxana Petroleum Corpora- 

 tion — the Seaman No. 1, m Palo Pinto County, 

 and the Rudd No. 1, in northern Comanche 

 County, both of which were. drilled into the 



e Uarrell, Joseph, op. cit., pp. 77ft-S34. 

 » Idem, fig. h, p. 796. 



