R.H. Meade H.A. Mahoney B.M. Delany Carl F. Nordin Jr. 1977 Sixty-five samples of bed material were collected from the Amazon River and its major tributaries between Belem, Brazil, and Iquitos, Peru. Samples were taken with a standard BM-54 sampler, a pipe dredge, or a Helley-Smith bedload sampler. Most of the samples have median diameters in the size range of fine to medium sand and contain small percentages of fine gravel. Complete size distributions are tabulated. application/pdf 10.3133/ofr77400 en U.S. Geological Survey, Particle size of sediments collected from the bed of the Amazon River and its tributaries in June and July 1976 reports