Geologia e geomorfologia do quaternário costeiro do estado do Rio Grande do Norte

Abstract

This study presents the regional geological-geomorphological map of the Quaternary coastal record of Rio Grande do Norte State, Brazil, with emphasis on the aeolian deposits. The Quaternary record comprises aeolian, alluvial, and marine deposits (peat, intertidal, and tidal flat deposits). They were dated by thermoluminescence (TL) and 14C methods. One active and three inactive aeolian geomorphological domains have been identified, which formed since the early Quaternary by the accumulation of sands from the coastal plain and such continental sources as the Barreiras Formation. TL dates indicate that aeolian deposits were formed in six main phases: 390,000 - 326,000, 270,000 - 240,000, 210,000 - 150,000, 63,000 - 24,000, 11,000 - 9,000, 6,500 years - till the present. These dates also indicate that aeolian deposits formed during both interglacial and glacial stages related to relative sea-level highstands and relative sea-level falls, respectively. Two marine terrace deposits have also been identified: a 210,000 - 214,000 year BP deposit between Natal and Baía Formosa on the N-S-trending coast; and a 120,000 - 114,000 year BP deposit between São Bento and Zumbi, mostly on the E-W-trending coast. Extensive Holocene intertidal deposits, mainly beachrocks, located on the N-S-trending coast exhibit ages of 7,000 - 6,000 and 5,500 - 4,500 cal. yr BP.