Holocene sea-level history: Evidence from coastal sediments of the northern Rio Grande do Norte coast, NE Brazil

The Holocene sea-level history of the mesotidal northern Rio Grande do Norte coast, NE Brazil, was reconstructed from sedimentology and AMS radiocarbon dating of beachrock and tidal lagoonal sediments. At 7000 cal. year BP at -3 m sea level stood and passed the modem sea level 6700 cal. year ago. The Holocene highstand reached 1.3 m above modem sea level at 5900 cal. year BP as determined by beachrock samples from the uppermost part of an intertidal foreshore deposit. A 5700 cal. year old shell midden overlies this beachrock that represents the spring-tide sea level. After the highstand, sea level dropped to its present position. Beachrock samples from intertidal upper foreshore deposits were used for elevation and age control. Beachrock positions with their error bars are all within the tidal-range envelope. Therefore, no secondary oscillations during the sea level fall can be confirmed. A linear sea-level fall of this magnitude can be explained by the mechanism of equatorial ocean syphoning. (c) 2005 Elsevier B.V. All rights reserved.