If you do not need this report after it has served your purpose, please return it to the Geological Survey, using the official mailing label at the end UNITED STATES DEPARTMENT OF THE INTERIOR Harold L. Ickes, Secretary GEOLOGICAL SURVEY W. C. Mendenhall, Director Professional Paper 186—L THE CORRELATION OF THE UPPER CAMBRIAN SECTIONS OF MISSOURI AND TEXAS WITH THE SECTION IN THE UPPER MISSISSIPPI VALLEY BY JOSIAH BRIDGE Shorter contributions to general geology, 1936 (Pages 233-237) UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1937 For sale by the Superintendent of Documents, Washington, D. C. Price 5 cents THE CORRELATION OF THE UPPER CAMBRIAN SECTIONS OF MISSOURI AND TEXAS WITH THE SECTION IN THE UPPER MISSISSIPPI VALLEY' By JOSIAH BRIDGE The Upper Cambrian section in the upper Mississippi The upper Mississippi Valley section is dominantly Valley has long been accepted as the standard for North clastic, whereas the sections in Missouri and Texas America, largely because it was the first to be studied are in the main calcareous. Therefore, lithologic in detail, because it contains a large number of distinct correlations have been of very little value. Many of faunas, and because it is still the best-known and the the faunas and especially certain elements of them are most complete Upper Cambrian section in the Middle distinctly facies faunas, and this, together with the West. Various classifications have been proposed lack of study of the Missouri and Texas sections and from £ime to time, but the latest and most detailed is certain miscorrelations in the upper Mississippi Valley that used by the ninth annual field conference of the section which have only recently been corrected, has Kansas Geological Society in the summer of 1935.2 greatly retarded correlations among these three areas. It is not the purpose of this paper to discuss the Recent work in Texas by Miss Christina Lochman merits and demerits of the Kansas Geological Society's and the writer has shown that the section in the Central classification, which is frankly a compromise that will Mineral Region is nearly as complete as the upper require further elaboration, refinement, modification, Mississippi Valley section and that most of the faunal and the elimination of certain names and their replace­ zones of the latter are present there. As now classified ment by others before it can be generally accepted. by the United States Geological Survey for the forth­ Reference to it in this paper does not imply that it has coming geologic map of Texas, the Upper Cambrian of been accepted either by the writer or by the United Texas comprises three formations and part of a fourth. States Geological Survey. The proposed reduction of These formations were all established on the basis of formations to three or four is certainly a step forward, lithology and without direct reference to the newly for the Conference seems to have kept the definition of proposed upper Mississippi Valley classification. There a formation—that is, a cartographic unit—firmly in is, however, a striking similarity between the two mind and has drawn the boundaries on that basis. classifications. Whether some of the units now classed as members The Hickory sandstone, which forms the base of the should be regarded as formations or not is beyond the Texas Cambrian section, appears to grade upward into scope of this paper. The proposed column is note­ the limestones of the Cap Mountain formation, and worthy in that it presents the most complete sequence together these formations make a unit which is roughly of faunas published to date, and in then* proper order, the equivalent of the Dresbach formation of the thereby facilitating the correlation with other sections. Conference classification. Table 1 of this paper presents a tentative correlation As the Hickory thickens the Cap Mountain thins, of the Upper Cambrian of three different areas—the the combined thickness of the two formations remaining upper Mississippi Valley, Missouri, and central Texas. about constant. A further proof of the gradational The sequence of faunas as worked out in the upper character of the two formations is the presence of the Mississippi Valley is shown in the first column, and Cedaria zone in both formations. This relationship will the presence of these faunas in the various stratigraphic be more fully described in a forthcoming paper by Miss units is indicated by a dot, or, if doubtful, by an interro­ Lochman. The Crepicephalus zone is present, although gation point. Crepicephatus itself is not a common form. The domi­ The determination of the succession of faunas is nant genera of this zone are Tricrepicephalus, which largely the work of Ulrich and Resser, Edwards, and extends downward into the Cedaria zone, and Coosia. Raasch; and although they are not in complete agree­ The Aphelaspis zone, characterized by Aphelaspis ment concerning details of the stratigraphy, they and depressa (Shumard), is well developed and is probably all other students of the Upper Cambrian of the Pacific the most widespread of all the Cap Mountain faunal province of North America agree very closely as to the zones. It occurs in the highest limestone beds of the details of the faunal succession. formation immediately beneath a thick bed of glau- conitic sandstone which Paige 3 included in the Cap 1 Presented before the Paleontological Society, Dec. 27,1935. 2 Kansas Geol. Soc., Guidebook, Ninth Annual Field Conference, upper Missis­ 3 Paige, Sidney, U. S. Geol. Survey Geol. Atlas, Llano-Burnet folio (no. 183) sippi Valley, p. 18, fig. 1 and elsewhere, 1935. p. 45 (field ed.), p. 6 (library ed.), 1912. 79233—37 233 234 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936 TABLE 1. — Tentative correlation of Upper Cambrian of upper Mississippi Valley, Missouri, and central Texas Texas Faunas Upper Mississippi Valley Missouri (II. S. Geological Survey, (Kansas Geological Society Conference classification, 1935) (U. S. Geological Survey, 1936) 1936) Gasconadia. 73 Oneota dolomite • Gasconade dolomite • • ot-t Burenoceras. Not represented Van Buren formation • ? Plethopeltis. Madison [sandstone] member • • ? Jordan sandstone of Ulrich Ellenburger limestone Trempealeauformation Jordan [sandstone] (lower part) • Acheilops. member • Eminence dolomite • Norwalk sandstone Eurekia-Euptychaspis. of Ulrich • Dikelocephalus minneso- tensis. Lodi [shale and siltstone] member • ? Scaevogyra. St. Lawrence dolomite [member] • Potosi dolomite • • t Lower Dikelocephalus. Mazomania formationof Bad Axe [sandstone] member • ? Doe Run dolomite Ulrich CambrianUpper ? Briscoia. • • Franconiaformation Prosaukia. Hudson [sandstone] member • Derby dolomite • Elvinsgroup Ptychaspis. • Wilberns formation ? formationUJrichof Billingsella. • • • Franconia Goodenough [sandstone] member Eoorthis. • • • Davis formation Camaraspis. • • • Ironton [sandstone] member Hypseloconus, a local shore • • phase of the Camaraspis fauna. Galesville [sandstone] member Lion Mountain sand­ Dresbachformation stone member Bonneterre dolomite Aphelaspis. • Cap Mountain for- • Crepicephalus. Eau Claire [sandstone] member • ~~~~~~ — -~__mation • Cedaria. • • • • ~""~"~^—--~~ ; Mount Simon [sandstone] member Lamotte sandstone Hickory sandstone Mountain formation. This sandstone, which is per­ In Missouri the lower portion of the Upper Cambrian haps the best horizon marker in the Central Mineral section is composed of the Lamotte sandstone and the Region, is here designated the "Lion Mountain sand­ Bonneterre dolomite. The contact between the two stone member of the Cap Mountain formation." The formations is believed to be gradational, although St. name is taken from Lion Mountain, in the northwestern Clair 4 has postulated an unconformity between them. part of the Burnet quadrangle. The section of the Cap The Cedaria fauna has been found in the lower 50 feet of Mountain formation exposed along State Highway 29 the Bonneterre dolomite along the Farmington anti­ on the southwest side of Lion Mountain is much thicker cline east of the St. Francois Mountains, where the and far superior to the type section on Cap Mountain. basal beds are predominantly limestone, and this The presence of the three faunas in both the upper occurrence serves to tie this portion of the section with Mississippi Valley and Texas definitely establishes the the uppermost Hickory and basal Cap Mountain of equivalence of this part of the section. Whether the Texas and with the lower part of the Eau Claire member Lion Mountain sandstone member is to be considered of the Conference classification for the upper Mississippi the full equivalent of the Galesville member of the Valley. The Crepicephalus and Aphelaspis faunas Conference classification is, of course, purely con­ 4 St. Olair, Stuart, Geology of Ste. Genevieve County, Mo.: Missouri Bur. Geology jectural. and Mines, vol. 22, pp. 37, 44, 1928. CORRELATION OF UPPER CAMBRIAN SECTIONS OF MISSOURI AND TEXAS 235 have not been found in Missouri, but one or both of The presence of the Camaraspis fauna in the base of them might well occur in the upper portion of the the Davis is another reason for assuming that the non- Bonneterre dolomite, which thus far has yielded no fossiliferous portion of the Bonneterre may represent fossils. the Crepicephalus and Aphelaspis zones. Overlying the Cap Mountain formation in Texas is Overlying the Davis are two thin dolomitic forma­ the Wilberns formation, which comprises all the strata tions—the Derby and Doe Run dolomites—which have between the