U. S. DEPARTMENT OF THE INTERIOR U. S. GEOLOGICAL SURVEY REMOTE SENSING AND AIRBORNE GEOPHYSICS IN THE ASSESSMENT OF NATURAL AGGREGATE RESOURCES by D.H. Knepper, Jr.1, W.H. Langer1, and S.H. Miller1 OPEN-FILE REPORT 94-158 1994 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 1U.S. Geological Survey, Denver, CO 80225 CONTENTS ABSTRACT........................................................................................... iv CHAPTER I. INTRODUCTION.............................................................................. I-1 II. TYPES OF AGGREGATE DEPOSITS........................................... II-1 Crushed Stone............................................................................... II-1 Sedimentary Rocks............................................................. II-3 Igneous Rocks.................................................................... II-3 Metamorphic Rocks........................................................... II-4 Sand and Gravel............................................................................ II-4 Glacial Deposits................................................................ II-5 Alluvial Fans.................................................................... II-5 Stream Channel and Terrace Deposits............................... II-6 Marine Deposits................................................................ II-6 III. DISTRIBUTION OF AGGREGATE DEPOSITS IN THE U.S..... III-1 Western Mountain Ranges............................................................. III-1 Alluvial Basins............................................................................... III-1 Columbia Plateau........................................................................... III-4 Colorado Plateau and Wyoming Basin............................................ III-4 High Plains................................................................................ III-4 Nonglaciated Central Region...........................................................III-5 Glaciated Central Region...............................................................III-5 Piedmont Blue Ridge Region..........................................................III-5 Glaciated Northeastern and Superior Uplands................................. III-6 Atlantic and Gulf Coastal Plain.......................................................III-6 Hawaiian Islands............................................................................ III-7 Alaska........................................................................................... III-7 IV. PHYSICAL PROPERTIES AND CHARACTERISTICS............. IV-1 Physical Properties......................................................................... IV-3 Electrical Resistivity (Conductivity)................................... IV-3 Spectral Reflectance and Albedo........................................ IV-5 Thermal Emissivity............................................................ IV-8 Thermal Inertia................................................................. IV-9 Radioactivity....................................................................IV-11 i Porosity and Permeability.................... .......................... IV-11 Characteristics........................................................................... IV-12 Landform........................................................................ IV-15 Drainage Texture..............................................................IV-15 Vegetation....................................................................... IV-17 Geologic Setting...............................................................IV-17 V. CONVENTIONAL AND TRADITIONAL EXPLORATION.........V-1 Where Are The Potential Deposits?.................................................V-1 What Are The Quality And Quantity Of Potential Deposits?............. V-2 Are The Potential Deposits Available?.............................................V-3 What Type Of Processing Is Required?............................................V-3 Getting The Aggregate To Market..................................................V-3 VI. AIRBORNE METHODS...............................................................VI-1 Geophysics............................................................................... VI-1 Resistivity........................................................................ VI-1 Aeromagnetics..................................................................VI-2 Radiometrics.................................................................... VI-2 Remote Sensing......................................................................... VI-3 Visible And Near-Infrared.................................... VI-3 Thermal Infrared................................................................VI-7 Microwave (Radar)............................................................VI-11 VII. NATURAL AGGREGATE AND THE USGS ASSESSMENT PROCESS VII-1 Delineating Permissive Areas.........................................................VII-2 Grade/Tonnage Models................................................................VII-4 Estimating Undiscovered Resources............................................ VII-5 Adaptation Or New Directions?......................................................VII-6 VIII. REFERENCES......................................................................... VIII-1 ii LIST OF TABLES Table III-1 Key to broad aggregate regions of the United States shown in Figure III-1.................................................................... III-3 Table IV-1 Properties and characteristics that define the quality and usefulness of aggregate for construction uses........................... IV-2 Table IV-2 Selected thermal properties of common rocks, sediments, and water............................................................................ IV-10 Table IV-3 Radioelement content measured in some common rock types....... IV-13 Table IV-4 Association of landform with the type of aggregate to be expected....................................................................... IV-16 Table VI-1 Remote sensing systems with possible applications for detecting and mapping sand and gravel deposits and sources of crushed stone............................................................................ VI-4 Table VII-1 Major and minor topics covered in representative descriptive mineral deposit model formats used by the USGS...................... VII-3 LIST OF FIGURES Figure II-1 Production of crushed stone and sand and gravel in the United States in 1991.................................................................. II-2 Figure III-1 Index map of broad natural aggregate regions of the United States............................................................................ III-2 Figure IV-1 Distribution diagrams of resistivities of common rocks and sediments....................................................................... IV-4 Figure IV-2 Spectral reflectance curves of some common rock-forming minerals ........................................................................ IV-7 Figure IV-3 Measured porosities and permeabilities of common igneous and sedimentary rocks............................................................. IV-14 Figure VI-1 Laboratory emission spectra of some common minerals and igneous rocks.................................................................. VI-10 iii ABSTRACT Natural aggregate made from crushed stone and deposits of sand and gravel is a vital element of the construction industry in the United States. Although natural aggregate is a high volume/low value commodity that is relatively abundant, new sources of aggregate are becoming increasingly difficult to find and develop because of rigid industry specifications, political considerations, development and transporation costs, and environmental concerns, especially in urban growth centers where much of the aggregate is used. As the demand for natural aggregate increases in response to urban growth and the repair and expansion of the national infrastructure, new sources of natural aggregate will be required. The USGS has recognized the necessity of developing the capability to assess the potential for natural aggregate sources on Federal lands; at present, no methodology exists for systematically describing and evaluating potential sources of natural aggregate. Because remote sensing and airborne geophysics can detect surface and near- surface phenomena, these tools may useful for detecting and mapping potential sources of natural aggregate; however, before a methodology for applying these tools can be developed, it is necessary to understand the type, distribution, physical properties, and characteristics of natural aggregate deposits, as well as the problems that will be encountered in assessing their potential value. There are two primary sources of natural aggregate: (1) exposed or near-surface igneous, metamorphic, and sedimentary bedrock that can be crushed, and (2) deposits of sand and gravel that may be used directly or crushed and sized to meet specifications. In any particular area, the availability of bedrock suitable for crushing is a function of the geologic history of the area - the processes that formed, deformed, eroded and exposed the bedrock. Deposits of sand and gravel