Geoid change indications along the brazilian coast during the last 7,000 years = Indices de déformation

Proceedings of the Fifth International Coral Reef Congress, Tahiti, 1985, Vol. 3 I' I& d - GEOID CHANGE INDICATIONS ALONG THE BRAZILIAN COAST DURING THE LAST 7,000 YEARS INDICES DE DEFORMATION DE LA SURFACE DU GEOIDE, LE LONG DU LIlTORAL BRESILIEN, AU COURS DES 7 O00 DERNIERES ANNEES L. MARTIN, J-M. FLEXOR Departamento de Geofisica, Observatorio Nacional, rua General Bruce 586, 20921 RIO DE JANEIRO, BRAZIL. 1 D. BLITZKOW Instituto AstronÔmico e Geofisico, Universidade de Sao Paulo, C.P. 30627, SA0 PAULO, BRAZIL. K. SUGUIO Instituto de Geociências, de Sao Paulo, C.P. 20899, SA0 PAULO, BRAZIL. ABSTRACT '6' Many radiocarbon ages have allowed us to reconstruct sea-level changes during the past 7000 years along 2000 h of the Brazilian coastline. From these data, it has been possible to define sea-level fluctuation curves for different sectors. Despite these curves being very similar in shape, (1 it is possible to observe some differences in amplitude which cannot be fortuitous. L The geoid map of Brazil shows that the coastline of the State of Bahia, approximately in the N-S direction, is parallel to the isobases of the geoidal height. In this case, shifts between different sea-level curves are not observed: for instance the 5100 years B.P. maximum is everywhere situated 5.0m above the present level. Otherwise, the coastline of the States of Sao Paulo and Parana, in the NE-SW direction, intercepts the isobases of the geoidal height. In this case, the ...