Fig. 1

Study area map. a Regional map showing the study location (red square) and other sites discussed: (1) Faxahatchee Strand37, (2) Northeast Shark River Slough38, (3) Cariaco Basin42, (4) No Man’s Land, Bahamas46, (5) Dos Anas Cave, Cuba47, (6) Church’s Bluehole, Andros48, (7) Lake Miragoane, Haiti40, (8) Valle de Bao, Dominican Republic50, (9) Turneffe Atoll, Belize51. b Aerial photographs show core locations on each island; use of a Russian peat corer eliminated sediment compaction and allowed determination of accurate paleo-elevations of peat deposits. c Detail of Florida Bay: locations of the four mud islands studied in Florida Bay, showing bedrock topography and indicating the proposed paleo-drainage channels of Taylor Slough83. Rhizophora (red) and Avicennia (black) mangroves ring the islands, creating a buffer for the fresh to hypersaline carbonate mudflats in the island centers, which were situated below sea level when cores were taken in 2014. Satellite images collected by DigitalGlobe’s WorldView-3 sensor on September 13, 2017