Sampled depth intervals and selected trace element concentrations as determined by X-ray fluorescence analysis of the intact floodplain cores in the Tri-State Mining District, 2011-12. All samples were collected by the U.S. Geological Survey using conventional coring methods with the exception of cores SH-FB-1 and SH-FB-4 which were collected using a plastic scoop; analysis was conducted using an x -ray fluorescence instrument owned and operated by U.S. Fish and Wildlife Service personnel following the U. S. Environmental Protection Agency Method 6200 (EPA, 2007) at the U.S. Fish and Wildlife Service and U.S. Geological Survey offices. Table Headings: Core_identifier, Site_identifier, Depth_1, Depth_2, Ave_depth, Arsenic, Cadmium, Barium, Cobalt, Copper, Manganese, Nickel, Lead, and Zinc which are explained further in the referenced data dictionary.