Paleozoic Corals of Alaska

Paleozoic Corals of Alaska Geologic and Paleogeographic Setting of Paleozoic Corals in Alaska Ordovician, Silurian, and Devonian Corals of Alaska Carboniferous Corals of Alaska A Preliminary Report Stratigraphic Distribution of Permian Corals in Alaska GEOLOGICAL SURVEY PROFESSIONAL PAPER 823-A, B, C, D Paleozoic Corals of Alaska Geologic and Paleogeographic Setting of Paleozoic Corals in Alaska By MICHAEL CHURKIN, JR. Ordovician, Silurian, and Devonian Corals of Alaska By WILLIAM A. OLIVER, JR., CHARLES W. MERRIAM, and MICHAEL CHURKIN, JR. Carboniferous Corals of Alaska A Preliminary Report By AUGUSTUS K. ARMSTRONG Stratigraphic Distribution of Permian Corals in Alaska By CHARLES L. ROWETT GEOLOGICAL SURVEY PROFESSIONAL PAPER 823-A, B, C, D UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1975 UNITED STATES DEPARTMENT OF THE INTERIOR STANLEY K. HATHAWAY, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress Cataloging in Publication Data Main entry under title: Paleozoic corals of Alaska. (Geological Survey professional paper ; 823) CONTENTS: Churkin, M. Jr. Geologic and paleogeographic setting of Paleozoic corals in Alaska. Oliver, W. A. Jr., Merriam, C. W. and Churkin, M., Jr. Ordovician, Silurian, and Devonian corals of Alaska, [etc.] Includes bibliographies and indexes. Supt. of Docs, no.: I 19.16:823-A,B,C,D 1. Corals, Fossil. 2. Paleontology Paleozoic. 3. Paleiontology Alaska. I. Churkin, Michael, 1932- II. Series: United States. Geological Survey. Professional paper ; 823. QE778.P34 563'.6'09798 75-619102 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Stock Number 024-001-02666-0 CONTENTS [The letters in parentheses preceding the titles are those used to designate the chapters] Page (A) Geologic and paleogeographic setting of Paleozoic corals in Alaska, by Michael Churkin, Jr. _______________________________ 1 (B) Ordovician, Silurian, and Devonian corals of Alaska, by William A. Oliver, Jr., Charles W. Merriam, and Michael Churkin, Jr. _____ 13 (C) Carboniferous corals of Alaska, a preliminary report, by Augustus K. Armstrong __________________________ 45 (D) Stratigraphic distribution of Permian corals in Alaska, by Charles L. Rowett ______________________________________ 59 III Geologic and Paleogeographic Setting of Paleozoic Corals in Alaska By MICHAEL CHURKIN, JR. PALEOZOIC CORALS OF ALASKA GEOLOGICAL SURVEY PROFESSIONAL PAPER 823-A Corals in geosynclinal and shelf strata of Alaska help correlate adjacent parts of Canada and Northeast U.S.S.R. and test paleogeographic reconstructions of the Arctic CONTENTS Page Abstract _______________________________, ___________ 1 History of Alaskan coral studies ___________________________ 1 Eegional geologic setting _________________________ 1 Eeef and reef-related deposits in volcanic rock-graywacke geosynclinal facies 3 Coral-rich deposits in carbonate-clastic rock shelf facies __ 6 Conclusions and future work ______________________________ 8 Eeferences cited ____________________________________ 10 ILLUSTRATIONS Page FIGURE 1. Map showing major tectonic features of the Arctic _ 2 2. Map showing early Paleozoic paleogeography _ 4 3-5. Columnar sections showing preliminary correlation of the Paleo zoic rocks: 3. Around the northern Pacific basin 5 4. Across the central parts of northeastern U.S.S.E. and Alaska ______________________ 7 5. Around the Canada basin _____________ 8 6. Map showing late Paleozoic paleogeography _________-__ 9 III PALEOZOIC CORALS OF ALASKA GEOLOGIC AND PALEOGEOGRAPHIC SETTING OF PALEOZOIC CORALS IN ALASKA By MICHAEL CHURKIN, JR. ABSTRACT the Devonian corals of east-central Alaska were pub Ordovician through Permian coral faunas in Alaska oc lished (Churkiri and Brabb, 1967). Since about 1950, cur in structurally complex limestone deposits in most of the geological provinces of the State. Coral-rich strata are a small group of specialists including A. K. Arm found in volcanic rock-graywacke geosynclinal facies or in strong, C. W. Merriam, W. A. Oliver, Jr., and carbonate-clastic rocks of the shelf facies. In the early Charles Rowett have become interested in Alaska's Paleozoic the southern and northern margins of Alaska Paleozoic corals. In the last decade, the first mono were oceanic areas with geosynclines in which coral- and graphic descriptions of Paleozoic corals of Alaska stromatoporoid-rich limestone closely associated with volcanic rocks developed in reef and reef-related shallow-water were published (Rowett, 1969; Armstrong, 1970a, deposits around volcanic islands. Separating the two b). oceanic areas was a narrow continental shelf area that re This volume of professional-paper chapters, that ceived mainly carbonate sediments. Reef or reef-breccia de summarizes our knowledge of Alaskan Paleozoic posits are distributed around the margins of this shelf. In the Late Devonian the geosynclinal sediments in corals, is an outgrowth of similar but more general northern Alaska were deformed into a foldbelt and up ized papers prepared by us for the International lifted. During the Carboniferous and Permian, successor- Coral Symposium held in Novosibirsk, U.S.S.R., in basin deposits developed on a broad shelf that covered the August 1971. Besides summarizing the results of all roots of the middle Paleozoic foldbelt. Corals in these shelf the coral studies to date, much of the older work has deposits of arctic Alaska form biostromal carbonate rocks or occur as abraded fossils in clastic nearshore sedimentary been revised and updated to modern standards of rocks. In southern parts of Alaska during the late Paleozoic, taxonomy and classification. Particular emphasis is reef and reef-related deposits developed around volcanic on the distribution and stratigraphic occurrence of centers as in the early Paleozoic. the coral faunas. Preliminary correlations of coral- Preliminary correlations of coral-bearing strata between Alaska and neighboring parts of Canada and Northeast bearing strata with other formations, many contain U.S.S.R. together with resulting paleogeographic recon ing other types of fossils, are shown in a series of structions of the Arctic are offered as working hypotheses correlation diagrams adapted from Churkin (1970, to be tested by future paleontological studies. 1973). HISTORY OF ALASKAN CORAL STUDIES REGIONAL GEOLOGIC SETTING Corals of Paleozoic age have been collected in Paleozoic coral faunas of Alaska occur in struc Alaska since the earliest days of geological explora turally complex limestone deposits of Ordovician tion, but until recently, corals in shelly faunas were through Permian age that are scattered widely identified only in the broadest terms and then only to through most of the geologic provinces of the State. round out the lists of invertebrates. The pioneers in Paleozoic rocks in the Alaska Range and farther Alaskan paleontology who provided most of the fos south are geosynclinal deposits that form the north sil identification for the first geological publications ern end of the Cordilleran foldbelt that rims the are G. H. Girty, E. M. Kindle, Edwin Kirk, and eastern Pacific and continues westward to connect Charles Schuchert (Dutro, 1956). with similar rocks in the Koryak Mountains of The first corals described from Alaska were Northeast U.S.S.R. (fig. 1, loc. 2). Northern Alaska Devonian species from the Porcupine River (Meek, the northeastern Brooks Range (fig. 1, loc. 10) 1867). Much later, a few Mississippian lithostro- and the Arctic Coastal Plain (fig. 1, loc. 12) is tionid corals were described by Hayasaka (1936), a underlain by early Paleozoic geosynclinal rocks that new genus Sciophyllum was described by Harker discontinuously rim the margin of the Canada basin and McLaren (1950), and photographs of some of of the Arctic Ocean and probably connect with simi- PALEOZOIC CORALS OF ALASKA 70°N. 70°N. 180° EXPLANATION FOLDBELTS PLATFORMS Paleozoic and Precambrian Location of section shown Middle Paleozoic in figures 3, 4, and 5 FIGURE 1. Major tectonic features of the Arctic. GEOLOGIC AND PALEOGEOGRAPHIC SETTING lar geosynclinal deposits in the Innuitian foldbelt of REEF AND REEF-RELATED DEPOSITS IN the Canadian Arctic Islands (fig. 1, loc. 8). East- VOLCANIC ROCK-GRAYWACKE central Alaska (fig. 1, loc. 3) and Seward Peninsula GEOSYNCLINAL FACIES (fig. 1, loc. 4) have thinner, mainly carbonate rock In the Cordilleran geosyncline of southern Alaska, sections that represent western extensions of the deposition of graywacke, conglomerate, and argil Yukon shelf that separates the circumarctic geosyn laceous rocks interbedded with pillow basalts, brec clinal trend from the circumpacific geosynclinal cias, and tuffs prevailed throughout most of the trend (Churkin, 1969). Paleozoic (fig. 2), Massive limestones composed In the Late Devonian and Early Mississippian the mainly of shelly fossils are interbedded with the circumarctic geosyncline was deformed, intruded by volcanic rocks. Very rapid facies changes reflect rug granite, and uplifted to produce wedges of coarse ged bottom relief, largely controlled by volcanic ac clastic sediments that spread southward onto ad tivity. Many of the coral- and stromatoporoid-rich joining areas of Alaska, Canada, and Northeast limestones closely associated with volcanic rocks U.S.S.R. (Churkin, 1969). During the Mississippian indicate reef and shallow-water shell bank deposits through the Triassic, successor basins (Brooks and around volcanic islands (Eberlein and Churkin, Sverdrup

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