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1 Departamento de Geologia, Universidade Federal do Rio Grande do Norte (UFRN), Natal-RN, 59072-970, Brazil bezerrafh{at}geologia.ufrn.br
2 Department of Geological Sciences, University College, Gower Street, London, WC1E 6BT, UK
3 Escola Técnica Federal do Rio Grande do Norte (ETFRN), Av. Senador Salgado Filho, no. 1559, Nova Descoberta, Natal-RN, 59056-000, Brazil
We have identified two beachrock facies in NE Brazil which can be used as reliable sea-level indicators. Facies (a) represents the lower foreshore and the upper shoreface, being mainly characterized by coarse unsorted sandstones with trough cross-stratification, whereas facies (b) corresponds to sediments deposited on the middle to lower foreshore and is usually characterized by medium to coarse, better sorted sandstones which form seaward-dipping, swash cross beds. The age of the beachrock bodies ranges from c. 7000 to 1150 cal. a BP. Although the relative sea-level record is complicated by oscillations which are probably due to minor climatic changes, it was possible to identify a general rise at c. 7000 cal. a BP which reached its maximum of +2 m c. 5000 cal. a BP and then started to fall to its present level some 300 years later. Our sea-level data are consistent with glacio-hydroisostatic models for the region but dates of 4080 cal. a BP on shells in growth position at +5 m above sea level and 2780 cal. a BP on a beachrock at sea level east of the Carnaubais fault point to rapid, possibly coseismic, late Holocene emergence.
