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AN ABSTRACT OF THE THESIS OF Scott R Stewart for the degree of Doctor of Philosophy in Soil Science presented on March, 1997 Title: Origin and Age of Fe-Mn-P Concretions and Nodules in an Oregon Wetland Signature redacted for privacy. Abstract approved: I' ' J. Herbert Huddleston Signature redacted for privacy. Abstract approved: I // Joseph R. Glasmann Wetland soils with complex stratigraphy and redoximorphic features occur on the margin of the Willamette Valley, Oregon. In the Jackson-Frazier wetland, vertisols show three distinct stratigraphic units that rest uncomformably upon each other and correspond to the Bashaw series Bss, 2Bt and 3BC horizons. Holocene alluvium deposited as distal alluvial fan sediment overlies partially eroded valley floor lake deposits (Willamette formation) and is mineralogically distinct from the lower two strata.Fe-Mn concretions differ among horizons in distribution, morphology, mineralogy and chemistry. Pressure oriented clays coat the exterior of the Bss and 2Bt concretions; low porosity, stable isotopic composition and subtle differences in mineralogy appear to indicate an early onset of formation and a long-term protected weathering environment within the concretions and 3BC nodules. Photomicroscopy provides evidence that despite distinct, sharp boundaries the concretions/nodules began forming in their current location after the transport and mixing of materials with disparate provenance. The concretions/nodules are enriched in Fe and P, relative to the matrix soil, by as much as an order of magnitude. Mn enrichment can exceed two orders of magnitude. During the reduced phase of the annual redox cycle, concentration values for dissolved and KCl/HCl-Fe2 are in the range of 40-60 and 5OO-6OOOmgFe2kg1soiI, respectively, and are sufficient to support Bss concretion formation within the known age of the associated geomorphic surface. Comparing the age of the concretion-C14 and the stratum in which the concretions are formed, places the larger, older Bss concretions between I 500-3300y old. The amount of Fe+2 available in the reduced-soil phase compared to the degree of FeDCB enrichment within the concretions suggests 2300-3500y for this enrichment to occur, with an average near 2800y. Some of the 3BC nodules may be near 38ky of age while the 2Bt concretions must be between 3.3ky and l5ky. The Bss-2Bt concretions and 3BC nodules appear to be currently forming in situ as a function of climate, redox and local valley stratigraphy. Origin and Age of Fe-Mn-P Concretions and Nodules in an Oregon Wetland by Scott R. Stewart A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Completed March 31, 1997 Commencement June 1997 Doctor of Philosophy thesis of Scott R. Stewart presented on March 31,1997 APPROVED: Signature redacted forprivacy. 0-Major Professor, representingoii Science Signature redacted for privacy. Co-Mr Professor, representing Soil Science Heid of Department of Crop and Soil Sciences Signature redacted for privacy. Dean of Graf'ate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Signature redacted for privacy. Scott R. Stewart, Author CONTRIBUTION OF AUTHORS Dr. Reed Glassmann assisted in the mineralogical, photomicroscopy, and SEM characterization of concretions and nodules and the writing of this manuscript. Chemical analysis were performed in the soil chemistry laboratory under the supervision of Dr. John Baham who assisted in the analysis and interpretation of the chemical data. Dr. Herb Huddleston assisted in sample collection, the interpretation of data and the writing of this manuscript. David D'Amore installed the monitoring equipment in the Jackson-Frazier wetland and provided data and ideas. TABLE OF CONTENTS Chapter I. Description of Study Area and Sampling Methodology I Chapter II. Mineralogy, Morphology, and Origin of Fe-Mn Concentrations In Stratigraphic Units of an Oregon Wetland. 7 Abstract 8 Introduction 10 Methods and Materials 12 Results 14 Discussion 28 Summary and Conclusions 49 Literature Cited 51 Chapter III. Ages and Rates of Formation of Fe-Mn-P Concretions in an Oregon Hydric Soil. 56 Abstract 57 Introduction 58 Methods and Materials 60 Results 62 Discussion 67 Summary and Conclusions 71 Literature Cited 73 Chapter IV. Stratigraphic Control of Hydrology, Redox, and Concretion/Nodule Distribution in an Oregon Wetland 76 Abstract 77 Intorduction 78 Materials and Methods 80 Results 81 Discussion 91 Summary and Conclusions 96 Literature Cited 97 Chapter V. Summary and Conclusions 101 Bibliography 104 List of Figures Elgure Page 1-1. Location of study area and sampling sites. 2 1-2. Jackson-Frazier wetland stratigraphy and ages. 2 1-3. Bashaw series soil profile. 4 2-1. Scanning electron micrographs of concretions and nodules 17 2-2. Detailed concretion and matrix mineralogy with depth. 19 2-3. Mineralogical differences with depth. 20 2-4. Concretion/nodule Fe-Mn oxide/hydroxide mineralogy 22 2-5. Scanning electron micrographs of primary minerals and features found within concretions and nodules 29 2-6. Elemental mapping and line profiles for Fe and Mn in concretions and nodules. 32 2-7. Polarizing microscope photography on thin sections from intact peds. 35 2-8. Mineralogy of the <0.2pm size fraction used for stable isotope analysis 43 4-1. Precipitation (bottom) and water postion (top) as observed in piezometers. 83 4-2. Duration of saturation determined by piezometers (bottom) and Eh values (top). 85 4-3. Dissolved oxygen values. 88 List of Tables Table Page 2-1. Concretion and nodule distribution, sizes, and densities. 15 2-2. Soil bulk densities, concretion/nodule distribution and porosity. 16 2-3. Summary of concretion, nodule, and matrix mineralogy for the three size classes. 21 2-4. Isotopic signatures for matrices, nodules, and Malpass member 41 2-5. DCB-Fe-Mn extracted from concretions, nodules, and soil matrix 42 3-1. Mean values for total organic carbon in concretions, nodules, and matrices. 63 3-2. Total Fe extracted from soil matrix, and large and small concretions and nodules. 64 3-3. Total Mn extracted from soil matrix, and large and small concretions and nodules. 65 3-4. P extracted from concretions, nodules, and soil matrix 66 3-5. KCl/HCl-Fe2 with depth in the Bashaw Bss horizons. 67 Origin and Age of Fe-Mn-P concretions and Nodules in an Oregon Wetland Chapter I. Description of Study Area and Sampling Methodology Soil strata were sampled within the Jackson-Frazier (J-F) wetland to separate and characterize redoximorphic concentrations - ie concretions and nodules. Concretions and nodules were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), polarizing microscope photography, and wet chemistry techniques to: i) determine their origin, ii) estimate their age and rate of formation, iii) decipher their history and the history of their location, iv) relate these features to field monitoring observations and, v) increase understanding of wetland functions on a more fundamental level. The J-F wetland lies on the western margin of the Willamette Valley immediately east of highway 99W in northeast Corvallis, Benton County, Oregon (Fig. I-I). The wetland is 64 hectares of shrub-scrub, forested and prairie palustrine plant communities on Holocene alluvial fan/valley fill material (Marshall, 1985; D'Amore, 1995) and ranges from 65m elevation in the southeast to 68m in the northwest (D'Amore, 1995). The wetland receives an average of 115 cm of rain per year, while the adjacent foothills receive slightly more. Ambient temperatures average 3°C in January and 18°C in July. The J-F wetland receives overland and subsurface flow, and the soil profile becomes saturated from both the top and the bottom of the profile. Much of the surface of the wetland can be ponded for up to 10 months per annum. The wetland is drained by Stewart slough to the southeast and a ditch from Frazier Creek which drains to the northeast. The stratigraphy of the JF wetland consists of Holocene alluvium deposited over a clayey stratum that lies unconformably upon silty sediments of Pleistocene age (Fig. 1-2). 2 Fr zier Creek 0 Jacksn Creek Jackson-Frazier Wetland Site 3 64 ha Site 2 0 o 0 L) 0 Site 1 Stewart Slough CORVALLIS, OREGON Figure 1-1. Location of study area and sampling sites. Holocene - Pleistocene stratigraphy and age Coast Range - Foothill Landscapes Frazier 'Creek Jacksn' 'reek Valley Floor Greenback silts Bashaw Vertisol - Alluvium 1 2ky V 2Bt-Malpass clay?l2.8-l5ky Irish Bend silts - 3BC 38-6Oky Figure 1-2. Jackson-Frazier wetland stratigraphy and ages. The Holocene alluvium has been transported via Jackson and Frazier creeks which drain Fe-rich Ultisols overlying Fe-Mn rich alkalic and tholeiitic basalt parent materials of the Eocene Siletz River volcanics in the foothills of the Coast Range (Snavelly et al., 1968; Glasmann and Simonson, 1985). The J-F alluvium contains most of the secondary minerals identified as alteration products of these basalts (Glasmann and Simonson, 1985). Complex Willamette Valley stratigraphy and geomorphology has resulted from catastrophic Pleistocene floods (Bretz, 1969), and the resulting alluvium (Willamette formation) has been divided into distinct stratigraphic units by Baister and Parsons (1969). At the Corvallis location the lowest and oldest unit is the Irish Bend (IB) member (Bashaw 3BC and 3C horizons) of the Willamette formation (38,410 ± 3,450y, Glenn, 1965; 40-60 ka, Reckendorf, 1992). This unit consists of "faintly bedded, micaceous, silty sediments with well defined upper and lower boundaries" and may be 4m thick at the J-F location (Balster and Parsons, 1969).It is unclear if the 2Bt silty clay horizon is the Malpass member of the Willamette formation or reworked lB materials.