Holocene history in the Gulf of Panama is based on lithology and faunal changes in cores from the continental shelf and on surface and subsurface sediment patterns. A transgression that started at the beginning of the Holocene caused deposition of nearshore sediments and fauna near the shelf edge. Approximately 11,500 years B.P., sea level was about 50 m. below its present position. The rise in sea level caused a change from Nearshore Fauna to Outer-Shelf Fauna in the center of the Gulf. Supply of sediments from land to the center of the Gulf was drastically reduced as a result of the fast landward migration of the shoreline, and only sediments formed in situ were deposited. With stabilization of the sea level, sediments started to spread from the shoreline seaward, forming a lens of modern clayey mud that overlies transgressive sand. The contact between this modern sediment lens and the transgressive sand is a disconformity. The time gap between the two, near the seaward edge of the clayey-mud lens (abou...