This data release is an archive of sedimentary laboratory analytical data produced by scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (USGS SPCMSC) for sediment cores and surface samples collected from coastal marshes in Georgia (GA), Virginia (VA), and Massachusetts (MA). Collaborators from USGS Patuxent Wildlife Research Center (PWRC) and the Virginia Institute of Marine Science (VIMS) collected these samples in South Altamaha, GA, Mockhorn Island, VA, Goodwin Island, VA and Laws Point, Plum Island Estuary, MA during a period spanning 2015 to 2019. This work provides the USGS and VIMS with the necessary data needed to assess the emergence rates (chronology and sedimentation rates) of coastal marshes at these locations. This publication includes data for marsh sediment cores and surface samples collected by collaborators at the USGS PWRC and VIMS from 2015-2019. Data products include site locations, loss on ignition and radiochemical data (alpha and gamma spectrometry), and Federal Geographic Data Committee (FGDC) metadata.