SEDIMENTARY GEOLOGY STABLE ISOTOPES. SEPM Short Course No. 10. Dallas MICHAEL A. ARTHUR, Organizer THOMAS F. ANDERSON JAN VEIZER LYNTON S.

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1 STABLE ISOTOPES IN SEDIMENTARY GEOLOGY SEPM Short Course No. 10 Dallas 1983 by MICHAEL A. ARTHUR, Organizer THOMAS F. ANDERSON ISAAC R. KAPLAN JAN VEIZER and LYNTON S. LAND Printed in U.S.A.

2 Additional copies ofthis publication may be purchased from SEPM for $ each (Members) and $20.00 each (Nonmembers). Send yourorderto: SEPM P. 0. Box 4756 Tulsa, OK Cnpyright. SEPM, i 983. AH rights reserved.

3 SEPM SHORT COURSE NO. IO CONTRIBUTORS MICHAEL A. ARTHUR DEPARTMENT OF GEOLOGY UNIVERSITY OF SOUTH CAROLINA COLUMBIA, S.C THOMAS F. ANDERSON DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF ILLINOIS URBANA, IL ISAAC R. KAPLAN DEPARTMENT OF EARTH AND SPACE SCIENCES UNIVERSITY OF CALIFORNIA LOS ANGELES, CA f JAN VEIZER, / DEPARTEMENT, DE GEOLOGIE r FACULTE DES SCIENCES ET GENIE UNIVERSITE D ' OTTOWA OTTOWA, ONTARIO CANkDA LYNTON S. LAND DEPARTMENT OF GEOLOGICAL SCIENCES UNIVERSITY OF TEXAS AUSTIN, TX

4 ACKNOWLEDGEMENTS We sincerely thank all of the people who have made this course and book possible. In particular we thank Peter A. Scholle for his encouragement to undertake this effort and Robin Dixon (SEPM) for her patience, guidance and enthusiasm. The final preparation of this text would not have been possible without the efforts of John Harrison (illustrations and paste-up), Maria Burdett (illustrations), and Pris Ridgell, Leigh Harrison, Melòdy Alderman, and Melissa Watson for manuscript preparation.

5 INTRODUCTION This course and the accompanying text should be of value to SEPM members as well as to other geologic professionals. Stable isotope geochemistry has come into its own in the last few years as our inventory of processes and materials has improved from the result of much basic research. Stable isotope techniques should become a standard application to most studies of sedimentary rocks and depositional environments, and we emphasize that it has applications in explorat:ion for hydrocarbons and minerals as well as in basic research. However, rapid progress depends on adequate and proper professionals in the techniques, the correct selection education of of samples, consideration of problems of interpretation, and concern for other types of data required to constrain interpretation of stable isotopic data. This text is designed to supplement the Society of Economic Paleontologists and Mineralogists continuing education course dealing with the application of stable isotopes to geologic problems. Stable isotope geochemistry is taught in relatively few universities or colleges, and although a few textbooks and other volumes present general principles of stable isotope geochemistry, they well documented case studies or applications to contain few adequate, relevant problems of interest to sedimentary geologists or paleoecologists. These short notes are an integral part of this course and should also fill a void in the literature. However, we do not pretend that the coverage of topics is entirely comprehensive. For example, the reader will find relatively little concerning the stable isotopic compositions of clay

6 minerals, biogenic silica or chert. The text is designed as an introduction to stable isotope techniques and interpretations, and the reader is by all means encouraged to follow this up with further study of the literature cited in the extensive bibliography. The short course text concentrates on the application of stable isotope geochemistry to the solution of problems in sedimentary geology. The stable isotopic composition of primary biogenic skeletal minerals, authígenic minerals and organic matter, when combined with other available chemical, textural and/or biological evidence, provides a powerful tool for tracing the operation of the geochemical cycles through time of, for example, carbon and sulfur, for interpretation of the paleosalinity, paleotemperature and paleofertility of depositional environments of sedimentary strata, and for understanding the processes of diagenetic alteration of sediments and sedimentary rocks. The text overall considers the principles and patterns of fractionation primarily of the stable isotopes of hydrogen, carbon, oxygen, nitrogen and sulfur and their partitioning between gaseous, fluid and mineral phases during primary and diagenetic sedimentary processes. An introduction to the theory of stable isotope abundances and fractionation and to the basic elements of measurement and notation is presented in Chapter 1 by T. F. Anderson and M.A. Arthur. The emphasis of the first chapter is on stable isotopes as tracers of the hydrologic cycle, the geochemical cycling of carbon and sulfur, and the application of oxygen isotopes in paleotemperature estimates. This begins with a discussion of global patterns of hydrogen and oxygen isotopic values in precipitation and in bodies of water as a

7 function of the operation of the hydrologic cycle. These data are necessary for consideration of the hydrogen and oxygen isotopic composition of bound water in clay minerals, chert, evaporite minerals, organic matter and hydrocarbons, and for consideration of fractionation in the water - CO2 - carbonate system as a function of temperature and other factors. We discuss the fractionation of carbon and sulfur isotopes (see Chapter 2) as well as patterns of carbon isotopic ratios in different components of the carbon cycle and sulfur in the sulfur cycle. These points will lead to consideration of the meaning of secular variations 13 in ó C and 3S in marine carbonates and evaporites. Patterns of oxygen isotopic f ractionation between mineral phase and fluid during inorganic and biologic precipitation of carbonate minerals are also treated as a prelude to paleotemperatur analysis. The second chapter, by I.R. Kaplan, deals with the use of sulfur, nitrogen and hydrogen isotopes in recognizing sources of organic matter and subsequent organic matter alteration during oxidation, bacterial degradation and thermal maturation and in tracing the geochemical cycles of nitrogen and sulfur. Chapter 3, by J. Veizer, considers carbonate diagenesis and the use of stable isotopes in recognizing the relative influence of meteoric or marine waters, different sources of dissolved carbonate, and changes in pore fluids and the extent of rock-water interactions throughout the diagenetic history of a particular sediment and sedimentary basin. In this part of the text, Veizer aleo presents the basic concepts of trace element partitioning and textural changes

8 during carbonate diagenesis in order to emphasize that stable isotopic analysis alone cannot provide for a unique solution to the chemistry of natural waters during diagenetic events. Finally, in Chapter 4, L. Land demonstrates the application of stable isotope geochemistry to the origin of sedimentary dolomite and diagenesis in clastic systems -- clay mineral authigenesis, quartz, carbonate, and zeolite cementation. Case studies are used liberally in this section on diagenesis to illustrate the mode of application of stable isotopic analyses. Michael A. Arthur, Organizer Thomas. F. Anderson Isaac R. Kaplan Jan Veizer Lynton S. Land

Characteristics of Sedimentary Rocks

Characteristics of Sedimentary Rocks Deposited at the earth s surface by wind, water, glacier ice, or biochemical processes Typically deposited in strata (layers) under cool surface conditions. This is