U.S. Geological Survey Open-File Report 2015-1153
/ Title Page / List of Figures / Conversion Factors / Abbreviations / Abstract / Introduction / Methods / Results / Discussion / Summary / Acknowledgments / References Cited / Appendix — Geospatial Data / Citation Page /
Figure 8. Barnhardt and others (1998) bottom-type classification based on four basic sediment units: Rock (R), Gravel (G), Sand (S), and Mud (M). If one of the basic sediment units represents more than 90 percent of the texture, only its uppercase letter is used. Twelve additional two-part units represent combinations of the four basic units, where the primary texture (greater than 50 percent) is given an uppercase letter and the secondary texture (less than 50 percent) is given a lowercase letter.