February 1st to 5th 2016
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Aeolianite as a proxy to evaluate former coastline position in northwest Ceara state – Northeast Brazil

Scientific Exhibition
Habitat Loss and Ocean Noise
Thursday, February 4, 2016 -
17:30 to 19:30

Carvalho, A.M. 1 Castelo Branco, R.M.G. 2 Lima Júnior, S.B. 3 Maia, L.P. 4 Ellis, J.T. 5 Gastão, F.G. da C. 6

1Institutode Ciências do Mar-LABOMAR, Universidade Federal do Ceará, Fortaleza, CE, Brazil
2Laboratório de Geofísica de Prospecção e Sensoriamento Remoto - LGPSR/ Universidade Federal do Ceará
3Institutode Ciências do Mar-LABOMAR, Universidade Federal do Ceará, Fortaleza, CE, Brazil
4Institutode Ciências do Mar-LABOMAR, Universidade Federal do Ceará, Fortaleza, CE, Brazil
5Marine Science Program and Department of Geography, University of South Carolina, SC, 29208, USA
6Institutode Ciências do Mar-LABOMAR, Universidade Federal do Ceará, Fortaleza, CE, Brazil

Stretches of the northwest coast of Ceará (NE - Brazil) were analyzed to identify whether the current coastline is a possible sediment source for the aeolianites that are currently present. Various factors were considered: modern day wind dynamics, coastline geometry, internal structures of the aeolian deposits, and dune migration pattern and evolution through the analysis of geological maps, GPR, and patterns of wind transport. For the latter we assume the generation and evolution of the dunes is controlled by the relationship between the wind direction transport and orientation of coastline segments and that the morphology of the aeolianites and their spatial distribution can be correlated to the current dunes fields.It was observed that the aeolianites have similar internal structures compared to the modern compound dune type, thus eliminating its correlation with isolated barchans, parabolic and frontal dunes. The outer edge limits of the compound dunes are 1000 to 5000 m away from the coastline that is its sediment source. This, in addition to the fact that the aeolianites are currently distributed very close to the coastline (and in some cases are being eroded by the waves) makes it impossible to assume that the present coastline was the sediment source of this aeolianites. The analysis of the distances between aeolianites outer edge and a line of sandy reefs, which is assumed as the hypothetical ancient coast line position, ranges from just over 700 to more than 4000 m from the outer boundary of aeolianites, demonstrating certain compatibility.Combined, these provide convincing evidence that the sediments that yielded the aeolianites likely came from an ancient coastline positioned offshore from the current coastline.
keywords: 
Coastline position, aeolianite, dunes, internal structures, GPR sections, wind dynamics.

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