Pedogenic Gypsum of Southern New Mexico: Genesis, Morphology, and Stable Isotopic Signature
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UNLV Retrospective Theses & Dissertations 1-1-2000 Pedogenic gypsum of southern New Mexico: Genesis, morphology, and stable isotopic signature John Grant Van Hoesen University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Van Hoesen, John Grant, "Pedogenic gypsum of southern New Mexico: Genesis, morphology, and stable isotopic signature" (2000). UNLV Retrospective Theses & Dissertations. 1186. http://dx.doi.org/10.25669/cudd-yb7b This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. 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UMI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PEDOGENIC GYPSUM IN SOUTHERN NEW MEXICO: GENESIS, MORPHOLOGY, AND STABLE ISOTOPIC SIGNATURE by John Van Hoesen Bachelors of Science, Geology University of Albany 1998 A thesis submitted in partial fulfillment of the requirements for the Master of Science Degree Department of Geoscience College of Sciences Graduate College University of Nevada, Las Vegas August 2000 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number 1401782 Copyright 2000 by Van Hoesen, John Grant All rights reserved. UMI UMI Microform 1401782 Copyright 2001 by Bell & Howell Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. Bell & Howell Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. © 2000 John Van Hoesen All Rights Reserved Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Thesis Approval IJND/ The Graduate College University of Nevada, Las Vegas July 21 _,20_QD_ The Thesis prepared by John Van Hoesen EntiUed Pedogenic Gypsum in Southern New Mexico; Genesis. Morphology, and Isptppic Signature. is approved in partial fulfillment of the requirements for the degree of Masters of Science _________________________________________ ExamrmtiOÊi Committee Chair Dean o f the Graduate College Examination Committee Member Examination Committee Member 2 Graduate College fa tu ity Représenta, P R /1017-5.1/1-00 n Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Pedogenic Gypsum in southern New Mexico: Genesis, Morphology, and Stable Isotopic Signature by John Van Hoesen Dr. Brenda J. Buck, Examining Committee Chair Assistant Professor of Geology University of Nevada, Las Vegas Recent work in Canada and Iran (Dowuona et aL, 1992 and Khademi et al., 1997a; 1997b) suggested a correlation exists between the and 8 D ratios of the hydration water of pedogenic gypsum and the ô'*0/6D ratios of meteoric water. However, a pedogenic origin for the sampled gypsum was not clearly supported and the results &om this procedure were not compared to other paleoclimatic indicators. Therefore, the goals of this study were, (1) evaluate the genesis and soil morphology of pedogenic gypsum in arid to semi-arid regions and ( 2) determine the applicability of pedogenic gypsum as a paleoclimatic indicator. Six profiles containing soils of late Pleistocene through Holocene age in the Tularosa and Jornada basins of Southern New Mexico were described and sampled for isotopic analysis. Gypsum soil morphology was expanded to include a new “snowball” morphology, as well as Stage I filaments and Stage II nodules, a classification scheme formerly only applied to carbonate morphology. A pedogenic origin for gypsum crystals 111 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. found throughout the six profiles was determined using a scanning electron microscope. These crystals do not exhibit any sign of re-precipitation, dissolution, or transport that would suggest secondary crystallization and contamination fi*om yoimger meteoric water. The hydration water of gypsum was extracted fi’om high-graded bulk sediment samples containing gypsum and analyzed for and 6D iso topic values. The 5*^0 and ÔD values collected fi’om the hydration water of gypsum were substantially enriched in the heavier isotopes indicating extensive evaporation. There is no trend between the isotopic signature of pedogenic gypsum and age, and there is no trend with depth. No correlation exists between the isotopic signature of pedogenic gypsum and the isotopic signature of pedogenic carbonate fixim this region. Results fiom this study indicate that isotopic analysis o f pedogenic gypsum is not an applicable tool for paleoclimatic reconstruction. Authors Note: An HTML version of this manuscript, additional SEM and fieldwork images not displayed in this manuscript, and relevant statistical data are contained on the enclosed CD-ROM. IV Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS ABSTRACT..............................................................................................................................üi LIST OF HGURES................................................................................................................ vii ACKNOWLEDGEMENTS.................................................................................................... xi CHAPTER 1 BACKGROUND..............................................................................................1 Purpose of Study .................................................................................................................... 1 Field Area Location. ...............................................................................................................1 Geology and Geo morphology of the Tularosa and Jornada Basins .................................3 Carbonate Horizon Morphology ..........................................................................................4 Gypsic Horizon Morphology ................................................................................................7 Gypsum Soil Morphology .................................................................................................... 9 Micromorphology of Gypsum ........................................................................................... 10 Stable Isotopes Background ...............................................................................................13 Isotopic Fractionation .......................................................................................................... 13 Explanation of Delta Notation ( 6)......................................................................................14 Oxygen and Hydrogen Isotopes Related to Paleoclimate ...............................................15 Oxygen Isotopes from Pedogenic Carbonate .................................................................. 20 Possible Sources of Error ...................................................................................................22