View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by University of Northern Iowa Proceedings of the Iowa Academy of Science Volume 22 Annual Issue Article 32 1915 Foundation of Exact Geologic Correlation Charles Keyes Copyright ©1915 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Keyes, Charles (1915) "Foundation of Exact Geologic Correlation," Proceedings of the Iowa Academy of Science, 22(1), 249-267. Available at: https://scholarworks.uni.edu/pias/vol22/iss1/32 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact [email protected]. ~..,.-=.c:-___:;o'.::...-- --- --- -- -- ------- ~ -- - Keyes: Foundation of Exact Geologic Correlation GEOLOGIC CORRELATION. 249 FOUNDATION OF EXACT GEOLOGIC CORRELATION. CHARLES KEYES. In the last generation or two there appears to have been little advancement made along lines of general geologic correla­ tion. Two controlling reasons stand out prominently. On ac­ count of the fact that the criterion of fossils is so largely mis­ used and is so generally unchecked by other critical criteria it is continually losing much of its former precedence. The adop­ tion of the lithologic formation as the cartographic unit is also almost a complete failure for the reason that no account is taken of the change,· replacement and effacement of its essential characters from place to place. All this confusion gives rise to an interminable synonymy which even a specialist in a circum­ scribed region cannot always satisfactorily make out without de­ tailed review of the original sections on the ground. When the mania for proposing new tit.res for geologic forma­ I I &.: tions becomes. so acute as it has in the case of the collector of ( fossils there is little real h.ope of simplifying stratigraphy so ! that the average. worker going into a district may. easily un­ derstand, aNd· without undue expenditure Of time and effort, acquire fundamental insight into the problems presented. In the last quarter, of a century there appears to be not a single systematic effort on the part of the geological surveys of the country to accomplish what should have been done years and years ago. Instead matters in this respect are growing rapidly worse instead of better. In no field of science is there presented so chaotic a state of nomenclature as that relating to stratig­ raphy. l In casting about for tlie proper area for which to construct a suitable generalized section of local rocks the quadrangle as r ordinarily selected appears to be much too small to be of any real ' service. The county is likewise too limited in extent. In size the state seems most satisfactory for trial-tests: in continental correlations. A comprehensive section of the Iowa rocks was given last year in the Proceedings of the Academy. This year a similarly constructed section of the Missouri rocks is annexed for comparison. Later, sections of Kansas, Oklahoma, Western Published by UNI ScholarWorks, 1915 1 Proceedings of the Iowa Academy of Science, Vol. 22 [1915], No. 1, Art. 32 250 IOWA ACADEMY OF SCIENCE GEOLO~ Texas, New Mexico and Arizona will be presented, as parts of a ' south . can be suggested fc broad but exact scheme of general correlation. known only from the ~ecc As fundamental elements in the upbuilding of the North Of the Ozarkian series. American continent the areas of Iowa and Missouri present some very nearly the exact eqm exceptionally instructive contrasts. In the geological sections · th The Roubidoux sa of these two. states the record of each physical event is accentu­ nor . mond sandstone of the s ated and paralleled with those of others. probably represents so:ne Several notable features first deserve enumeration. In the The Gunter sands~one .is. one area certain phases of unconformity are repre8ented by tre­ In the Ordovicic divi1 mendous sections of sediments. At one time a great and. lofty represented by the yell mountain range stretched across the northern area, while in the found in• the north. Eai south remained a lowland plain. In its present aspect the Ozark sented in Iowa by depoi dome did not exist until very recent times. These circumstances which have no sediment have an important bearing upon the proper interpretation of the developed in the sout~. regional stratigraphy. The Tennessean seri~s For many years the two sections have appeared to be so un­ .re aches in southern. Mis. like that little exact comparison was possible. This apparent attains great diversity ll discrepancy arises from several causes. First, there is small distribution it exten~s attempt to assign to the several geologic formations recognized the Mississippian series their proper taxonomic ranks. Second, different· names for the therefore, really belong same terranes are used in the two states. Third, state lines pre­ the sedimentation of .w vent workers in the one province from extending their investi­ The importance of t~1s gations into adjoining districts and thus making exact strati­ The Arkailsan series . graphic correlations. Fourth, terranes are represented in one by a marked hiatus. T state which have no exact depositional equivalent in another. strata in such a mannE Fifth, change in lithologic character of formations tend to con­ if not one of co:mple1 fuse the delimitation of formations. Ozark dome in souther'. The similarities of the two sections are as important as are great Arkansan foni;! sandstones. This atta11 their differences. The former are the more app.arent since the ness of more than 15 taxonomic values of the several formations, the usage of the equivalent of the ~nc~ same nomenclature, and the positions of the terranes in the time­ the coal meas:iires m t scale are made to harmonize in a way never before attempted. bonic successioD; !1l?P, To the detailed differences a,ttention is specifically called in an­ any marked divisim to assign a taxo1 other place. ~ose visions eguivalen~ to Of the larger differences between the two sections the most cedure is not behevei notable may he briefly enumerated. First of these are those and it is difficult. to which relate to the Cambric rocks. The Croixan series, which vance over our prior in Iowa is scarcely exposed above stream-level, is well differen­ Another notable c tiated in Missouri and· widely outcrops around the Ozark dome. general sections is tl rine Tertiaric beds; Although the successions in the two states have nearly the same nental deposits of thi thickness no equivalents of the subdivisions recognized in the sections with the gre https://scholarworks.uni.edu/pias/vol22/iss1/32 2 !~ . Keyes: Foundation of Exact Geologic Correlation )!ENCE GEOLOGIC CORRELATION 251 pr~sented, as parts of a Iat10n. south can be suggested for Iowa, where the rocks are mainly of the North buil~ing known only from the records of deep-well sections. i M1ssouri present some Of the Ozarkian series the Jefferson dolomite appear8 to be th: geological sections . very nearly the exact equivalent of the Shakopee dolomite o:f the ysrnal event is accentu- north. The Roubidoux sandstone corresponds to the New Rich­ mond sandstone of the same region. The Gasconade dolomite enumeration. In the probably represents somewhat more than the Oneota dolomite. ~re represented by tre- The Gunter sandstone is a local deposit. 1me a great and. lofty r In the Ordovicic division the Early part of the sequence, iern area, .wnile in the represented by the Yellville dolomite, does not appear fo be isent aspect the Ozark found in•the north. Early Siluric sedimentation is not repre­ : Thes!l circumstances sented in Iowa by deposits. Early and Mid Devonic terranes, ~ interpretation of the which. have no sedimentative representatives in Iowa, are well developed in the south. ppeared to be so un­ The Tennessean series, which is so poorly developed in Iowa, ~i~le. This apparent reaches in southern Missomi a quite remarkable thickness and li'1rst, there is small attains great diversity in lithologic character. In its geographic ~rmations recognized . distribution it extends far southeastward into Alabama; while :erent. names for th the Mississippian series extends southwestward. The· two- series h" e Ird, state lines pre- therefore, really belong fo quite distinct geographic provinces, mding their investi­ the sedimentatio-n of which overlaps somewhat along one edge. naking exact strati­ The impo-rtance o-f this distinction is not generally recognized. represented in one The Arkansan. series in both Missouri and Iowa is represented tivalent in another by a marked hiatus. The plane of unconformity bevels all older lations tend to con~ strata in such a manner as to indicate a long period of erosion, if not o-ne of complete planation. On the south side of the s important as are Ozark dome in southern Missouri appears the feather..edge of the apparent since the great Arkansan formation comprisjng coal-bearing shales and sandstones. This attains in central Arkansas an enormous thick­ ' ·the usage of the ness of more than 15,000 feet. This series is the depositional irranes in the time­ equivalent of the unconformity which characterizes the base of . before attempted. the coal measures in both Missouri and Iowa. The entire Car­ lcally called in an- bonic succession appears so important terranally and has so many marked division lines that Chamberlin and Salisbury pro­ pose to assign a taxonomic to each of its two principal di­ sections the most rank visions equivalent to that of .Devonic or Cambric.