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Sea Level and Climatic Changes Related to Late Paleozoic Cycles

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Sea Level and Climatic Changes Related to Late Paleozoic Cycles BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA SEA LEVEL AND CLIMATIC CHANGES RELATED TO LATE PALEOZOIC CYCLES BY HAEOLD R. WANLESS AND FRAN CIS P. SHEPARD CONTENTS Page Introduction..................................................................................................... 1178 Cyclic sediments............................................................................................... 1178 General statement...................................................................................... 1178 Piedmont facies.......................................................................................... 1182 Delta facies................................................................................................ 1184 Neritic facies.............................................................................................. 1186 Interpretations of cyclic sediments.................................................................... 1186 General statement...................................................................................... 1186 Hypothesis of intermittent subsidence........................................................ 1187 Hypothesis of alternate subsidence and uplift............................................. 1187 Objections to these hypotheses................................................................... 1188 Hypothesis of sea-level fluctuations................................................................... 1189 General statement...................................................................................... 1189 Advantages of this interpretation............................................................... 1190 Causes of sea-level fluctuations................................................................... 1190 General Statement.............................................................................. 1190 Diastrophism...................................................................................... 1190 Atmospheric moisture......................................................................... 1191 Glacial control....................................................... ............................. 1191 Late-Paleozoic glaciation.................................................................................. 1193 Extent........................................................................... ; ......................... 1193 Age and duration....................................................................................... 1194 Climatic cycles................................................................................................. 1197 Relation to late-Paleozoic cyclic sediments.................................................. 1197 Influence of glacial epochs on climate in non-glaciated areas........................ 1198 Pleistocene evidence............................................................................ 1198 Inferences regarding the late-Paleozoic glacial climates............................... 1199 Evidence for cool, semi-arid glacial epochs.................................................. 1200 Evidence for moist, warm interglacial epochs.............................................. 1200 Periodicity and causes................................................................................ 1200 Interpretation of late-Paleozoic cycles in terms of sea-level fluctuation and climatic cycles............................................................................................................ 1202 General statement...................................................................................... 1202 The channels................................................................................... .......... 1202 The sandstones.......................................................................................... 1202 The underclay........................................................................................... 1203 The coal.................................................................................................... 1203 The black shale.......................................................................................... 1203 The limestones........................................................................................... 1203 The gray shale........................................................................................... 1204 Suggested investigations.................................................................................... 1204 Summary.......................................................................................................... 1205 Supplemental Bibliography............................................................................... 1206 (1177) Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/47/8/1177/3415348/BUL47_8-1177.pdf by guest on 02 October 2021 1178 WANLESS, SHEPARD— SEA LEVEL AND CLIMATIC CHANGES ILLUSTRATIONS Figure Page 1. Representative sections of cyclothems of the piedmont facies 1181 2. Representative sections of cyclothems of the delta facies. 1183 3. Representative sections of cyclothems of the neritic facies... 1185 INTRODUCTION Numerous investigators in recent years have called attention to regu­ larly recurrent sequences in the strata of the Pennsylvanian system in the eastern and central parts of the United States. Wanless, in associa­ tion with J. M . Weller, has been engaged for several years in field studies of the Pennsylvanian in Illinois and surrounding states, for the Illinois State Geological Survey, and has traced many of the recurrent sequences or cyclothems1 over wide areas, using them as an aid in correlation. Reconnaissance studies have also been made by him in Ohio, Kentucky, Indiana, and the northern mid-continent and Rocky Mountain regions. Shepard has suggested the basic idea as to the cause of the cycles developed in this paper and has contributed information from studies of recent sea level oscillations and the influence of these changes on conti­ nental shelf sediments. The authors have attempted to determine whether this peculiar type of sedimentation is largely limited to the eastern part of North America, where it has become fairly well known, or whether comparable sequences are to be found in rocks of corresponding age elsewhere. W ith this point in view, Wanless studied the Pennsylvanian rocks of the Rocky Mountain region during the summer of 1934, and found abundant evidences of cyclic sedimentation in that region. Weller earlier studied evidences of cyclic sedimentation in Ohio, West Virginia, Iowa, Missouri, Kansas, and Oklahoma. The purpose of the present paper is to review the explanations of cyclic sedimentation which have been offered, and to present the new hypothesis that the rhythmic alternations of sediment in the late Paleozoic are con­ trolled largely by sea level fluctuations and climatic variations related to late Paleozoic glaciation. CYCLIC SEDIMENTS GENERAL STATEMENT Pennsylvanian cycles were first described by Udden2 from central Illinois, where they include coal, limestone, shale, sandstone, and clay. 1 H. R. Wanless and J. M. Weller: Correlation and extent of Pennsylvanian cyclothems, Geol. Soc. Am., Bull., vol. 43 (1932) p. 1003. 2 J. A. Udden: Geology and mineral resources of the Peoria quadrangle, Illinois, U. S. Geol. Surv., Bull. 506 (1912) p. 47-50. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/47/8/1177/3415348/BUL47_8-1177.pdf by guest on 02 October 2021 CYCLIC SEDIMENTS 1179 Cyclical sediments of the same age have since been described from Illinois,8 Kansas,4 Missouri and Iowa,5 Ohio,6 West Virginia,7 Michigan,8 Texas,9 Colorado,10 the British Isles,11 and the Silesian basin.12 Other described sections which indicate the presence of cyclic sediments are in the maritime provinces,13 Rhode Island,14 Alabama,15 Oklahoma,16 New Mexico,17 Utah,18 Idaho,19 California,20 the Westphalian coal basin,21 and the Donetz basin.22 I t seems probable that Pennsylvanian sediments 8J. M. Weller: Cyclic sedimentation in the Pennsylvanian and its significance, Jour. Geol., vol. 38, no. 2 (1930) p. 97-135; The conception of cyclical sedimentation during the Pennsylvanian ‘period, 111. State Geol. Surv., Bull. 60 (1931) p. 163-177. H. R. Wanless : Pennsylvanian cycles in western Illin o is, HI. State Geol. Surv., Bull. 60 (1931) p. 179-193; Pennsylvanian section in western Illinois, Geol. Soc. Am., Bull., vol. 42 (1931) p. 801-812. H. R. Wanless and J. M. Weller: op. cit., p. 1006-1009. 4 R. C. Moore : Sedimentation cycles in the Pennsylvanian of the northern mid-continent region, [abstract] Geol. Soo. Am., Bull., vol. 41 (1930) p. 51-52; Pennsylvanian cycles in the northern m id­ continent region, 111. State Geol. Surv., Bull. 60 (1931) p. 247-257; Correlation of phases in sedi­ mentation cycles in Pennsylvanian and “Permian” rocks of Kansas, Geol. Soc. Am., Pr. for 1934 (1935) p. 100. 5 H. R. Wanless and J. M. Weller : op. cit., p. 1009-1015. •Wilber Stout: Coed-formation clays of Ohio, Ohio Geol. Surv., 4th ser., Bull. 26 (1923) p. 533- 568; Pennsylvanian cycles in Ohio, 111. State Geol. Surv., Bull. 60 (1931) p. 195-216. TD. B. Reger: The Monongahela series of West Virginia, W. Va. Acad. Sci., Pr., vol. 3 (1929) p. 134-146; Pennsylvanian cycles in West Virginia, 111. State Geol. Surv., Bull. 60 (1931) p. 217-239. 8W. A. Kelly: Pennsylvanian stratigraphy near Grand Ledge, Michigan, Jour. Geol., vol. 41 (1933) p. 79-86. 9F. B. Plummer: Pennsylvanian
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