Loess Investigations in Mississippi CEOLOCY OF MISSISSIPPI LOESS J. O. SNOWDEN, JR. RICHARD R. PRIDDY FORESTS OF WEST CENTRAL MISSISSIPPI AS AFFECTED BY LOESS C. D. CAPLENOR, ET AL BULLETIN 111 MISSISSIPPI GEOLOGICAL, ECONOMIC AND TOPOGRAPHICAL SURVEY WILLIAM HALSELL MOORE Director and State Geologist JACKSON, MISSISSIPPI 1968 PRICE $3.00 Loess Investigations in Mississippi CEOLOCY OF MISSISSIPPI LOESS J. O. SNOWDEN, JR. RICHARD R. PRIDDY FORESTS OF WEST CENTRAL MISSISSIPPI AS AFFECTED BY LOESS C. D. CAPLENOR, ET AL BULLETIN 111 MISSISSIPPI GEOLOGICAL, ECONOMIC AND TOPOGRAPHICAL SURVEY WILLIAM HALSELL MOORE Director and State Geologist JACKSON, MISSISSIPPI 1968 PRICE $3.00 STATE OF MISSISSIPPI Hon. John Bell Williams — Governor MISSISSIPPI GEOLOGICAL, ECONOMIC AND TOPOGRAPHICAL SURVEY BOARD BOARD Hon. Henry N. Toler, Chairman _— ..Jackson Hon. Don H. Echols, Vice Chairman — Jackson Hon. William E. Johnson — Jackson Hon. N. D. Logan - Oxford Hon. Richard R. Priddy _..Jackson STAFF William H. Moore Director and State Geologist Wilbur T. Baughman Geologist Alvin R. Bicker, Jr. Geologist Theo H. Dinkins, Jr _ - Geologist Thad N. Shows _ — Geologist Charles H. Williams, Jr Geologist Jean K. Spearman - Secretary Shirley J. Webb Secretary LETTER OF TRANSMITTAL Office of the Mississippi Geological, Economic and Topographical Survey Jackson, Mississippi August 15, 1968 Mr. Henry N. Toler, Chairman, and Members of the Board Mississippi Geological, Economic and Topographical Survey Gentlemen: Herewith is Mississippi Geological Survey Bulletin 111, "Loess Investigations in Mississippi," by J. O. Snowden, Jr., Richard R. Priddy, and others. This Bulletin is the result of eight years of study. It contains the results of intensive field and laboratory studies. The loess is examined from the standpoint of stratigraphy, mineralogy, chemistry and electrical character. In addition there are supporting articles on ceramic properties and the flora and fauna supported by the loess. Bulletin 111 is the most comprehensive study of the loess that has been made in this area. Respectfully submitted, William H. Moore Director and State Geologist WHM:js LOESS INVESTIGATIONS IN MISSISSIPPI 5 GEOLOGY OF MISSISSIPPI LOESS CONTENTS Page GEOLOGY OF MISSISSIPPI LOESS (Snowden and Priddy) 13 Abstract 13 Introduction 14 Review of Literature 15 Preliminary Statement 15 Summaries of Selected Reports on Loess 15 General Description of the Study Area 31 Location 31 Topography 31 Field Investigations 35 Preliminary Statement — 35 Methods of Field Investigations 35 Collection of samples 35 Exposed sections ~ 35 Roadcuts 35 Gravel pits 38 Hand auger holes 38 Core holes 38 Measuring sections 39 Measuring electrical properties 39 Exposed sections 39 Auger and core holes 39 Gamma ray emission logging — 40 Thickness and areal distribution 40 Preliminary Statement 40 Relation of Loess to Pre-Loess Topography 40 Relation of Loess Thickness and Areal Distribution to Distance from Bluff 44 Eastern Limit of Mississippi Loess Belt — 47 Laboratory Investigations 49 Preliminary Statement 49 Preparative Procedures 50 Analytical Methods—Mineralogical, Textural, Chemical, and Radiometric 51 Instrumentation—X-ray, Microscopes, Hydrometer, and Computer 53 Mineralogy 54 Preliminary Statement 54 Quartz and Feldspar 54 Carbonates 58 Accessory Heavy Minerals 67 Description of heavy minerals 68 Provenance of the loess based on its heavy mineral assemblage 73 Clay Mineralogy 74 Identification and classification of clay minerals 74 Quantitative estimation of clay minerals in Mississippi loess ~ 79 Distribution of clay minerals 82 Source of clay minerals in Mississippi loess 85 Mineralogical Classification 85 MISSISSIPPI GEOLOGICAL SURVEY Page Texture 89 Preliminary Statement 89 Textural Variability 89 Geographic variability 93 Interrelations among the textural parameters 94 Other Textural and Structural Characteristics 98 Shape and arrangement of grains 98 Cementation and structural stability of Mississippi loess .. 98 Electrical Measurements as an Aid in Stratigraphy 101 Preliminary Statement 101 Electrical Conductivity Logging of the Outcrops 101 Electrical Conductivity Logging of Holes Drilled into the Loess 103 Neltronic Gamma Ray Logging of Holes 108 Utilization of Physical, Electrical, and Chemical Variations in Loess Stratigraphy 109 Preliminary Statement 109 Physical Criteria for Zoning in the Field 110 Color 110 Moisture content 111 Effervescence with acid 111 Caliche content 112 Snail content 112 Grain size 113 Chemical Criteria for Zoning in the Field 113 Soluble carbonate determinations 113 pH and Eh determinations 113 pH readings—basicity of loess 114 Eh readings—reducing-oxidizing potential of loess ...114 Electrical Determinations of Loess in the Field 115 Between movable electrodes 115 Gamma ray logging 117 Stratigraphy 118 Preliminary Statement 118 Previous Stratigraphic Reports and General Observations 118 Radiocarbon Dating of Mississippi Loess 119 Standard Section and Stratigraphic Classification 124 Pre-Loess Stratigraphy 128 Orgin 129 Preliminary Statement 129 Source of Mississippi Loess 129 Mode of Loess Deposition 129 Eolian deposition of loess 130 Loessification 132 Observations on the genesis of Mississippi loess 132 Conclusions 138 Acknowledgments 140 Selected Bibliography 142 Appendix 170 Location and General Description of Loess Samples 170 Chemical Analyses of Loess 184 Texture of Loess and Related Sediments 190 Pyrophysical (Ceramic) and Plastic Properties of Mississippi Loess 195 Pulmonate Gastropods in the Loess 201 LOESS INVESTIGATIONS IN MISSISSIPPI 7 LIST OF TABLES Table Page 1. Accessory heavy minerals and non-carbonate light minerals in the loess and related sediments 55 2. Hornblende-kyanite ratios of mixed loess-Citronelle non opaque accessory heavy mineral assemblages _ 73 3. Average non-opaque heavy mineral assemblage of Mississippi loess compared with upper Mississippi Valley and Illinois Valley loesses 75 4. Record of hand auger hole drilled at footage 12,445, atop first bench of road cut, east side of U. S. Highway 61 bypass 107 5. Radiocarbon ages of fossil pulmonate gastropod shells and one fossil wood sample from loess deposits near Vicksburg, Mississippi 121 6. Location and general description of loess samples 170 7. Chemical analyses of loess —184 8. Texture of loess and related sediments 190 9. Pyrophysical properties of Mississippi loess 198 10. Dry and plastic properties of Mississippi loess 200 11. Fossil gastropods in Mississippi loess 202 LIST OF FIGURES Figure PaSe 1. Generalized distribution of loess in the central United States facing page 14 2. Sample stations and general topography in the central Mississippi loess belt — — 32 3. Sample stations in the Greenwood, Mississippi area — 33 4. Sample stations in the Louisiana-Mississippi border area — 34 5. Vertical, terraced highway cuts on U. S. Highway 61 bypass near Vicksburg, Mississippi — ~ - - 36 6. Highway profiles through the loess hills near Vicksburg, Mississippi 37 7. Section A-A': Loess distribution and bedrock stratigraphy near Vicksburg, Mississippi - — 41 8. Cross section of lower Mississippi Valley region near Natchez, Mississippi 42 9. Roadcut on U. S. Highway 61 bypass showing loess-pre-loess topographic relationship — — 43 10. Roadcut along U. S. Highway 61 bypass showing general topography and highway engineering practice 43 11. Roadcut on U. S. Highway 61 bypass showing a truncated loess-covered ridge facing the Mississippi Alluvial Plain 44 12. Relationship between ridge-top loess thickness and distance from Mississippi River bluffs, Vicksburg east to Jackson, Mississippi - 45 13. Thickness of loess in the lower Mississippi Valley 46 14. Roadcut on U. S. Highway 80 near Clinton, Mississippi showing typical thin leached loess near to east margin. The loess rests on gray silty sand of the Catahoula (Miocene) forma tion -— — - 48 15. Flow diagram of preparative procedures and mineralogical- textural analytical techniques .— 49 16. Flow diagram of preparative procedures and chemical analy tical techniques ——— - 52 17. MgO, CaO, and COo mole fractions in loess from auger hole 3, Warren County, Mississippi, revealing carbonate mineral zones - 59 8 MISSISSIPPI GEOLOGICAL SURVEY Figure Page 18. X-ray diffractograms of bulk loess from auger hole 3, show ing mineralogy of the three carbonate zones 61 19. X-ray diffractograms of bulk loess demonstrating the range of carbonate mineral variation 62 20. X-ray diffractogram of loess concretion showing high calcite content due to ground water concentration 63 21. X-ray diffractograms comparing shell mineralogy of fossil and living Allogona profunda 64 22. Loess concretions 65 23. MgO, CaO, and COL, mole fractions in loess at road cut 10 (Figure 6) showing cyclic carbonate mineral zones 67 24. Mean accessory heavy mineral assemblages of loess and re lated sediments 71 25. Mean non-opaque, non-micaceous accessory heavy mineral composition of loess and related sediments 72 26. X-ray powder diffractograms showing typical loess clay mineralogy 77 27. X-ray powder diffractograms showing mineralogical differ ences between the less-than-two micron and the 2-5 micron particle diameter fractions of the loess 80 28. X-ray powder diffractograms showing clay mineral differ ences among loess, "Citronelle", and mixtures of the two 83 29. Petrographic classification of Mississippi loess 87 30. Mean mineral composition of Mississippi loess 87 31. Grain-size distribution of Mississippi loess and related sediments .. 90 32. Typical cumulative