HR: 0800h
AN: T41A-10    [Abstracts]
TI: Geophysical modeling of the Araguainha impact structure, Brazil
AU: * Vasconcelos, M
EM: marquinhos.arv@pop.com.br
AF: Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, IAG-USP, Rua do Matao, 1226, Cidade Universitaria, Sao Paulo, SP 05508-090, Brazil
AU: Molina, E
EM: eder@iag.usp.br
AF: Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, IAG-USP, Rua do Matao, 1226, Cidade Universitaria, Sao Paulo, SP 05508-090, Brazil
AU: Marangoni, Y
EM: yara@iag.usp.br
AF: Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, IAG-USP, Rua do Matao, 1226, Cidade Universitaria, Sao Paulo, SP 05508-090, Brazil
AU: Yokoyama, E
EM: elder@iag.usp.br
AF: Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, IAG-USP, Rua do Matao, 1226, Cidade Universitaria, Sao Paulo, SP 05508-090, Brazil
AU: Lana, C
EM: lana@sun.ac.za
AF: Department of Geology, University of Stellenbosch,Private Bag X1,Matieland 7620, South Africa
AU: Trindade, R
EM: 55-11-30914764
AF: Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, IAG-USP, Rua do Matao, 1226, Cidade Universitaria, Sao Paulo, SP 05508-090, Brazil
AU: Souza Filho, C
EM: beto@ige.unicamp.br
AF: Departamento de Geologia e Recursos naturais, Instituto de Geociencias, UNICAMP, Campinas, SP 13083-970, Brazil
AB: The Araguainha crater is the largest impact structure of South America, formed over horizontal sediments of the Paraná Basin. This structure of 40 km in diameter has a central uplift which presents a negative contrast of density. The depth analysis of Araguainha presented in this work is supported by gravimetric modeling in two profiles of E-W and N-S directions. The results of 2,5 D gravity models allow one to classify the Araguainha structure as a concentric, symmetrical structure, with an average basement depth of 1,0 km. However, at the southern rim, the structure shows a relatively smaller depth when compared with the others regions, with is coincident with a local low gravity anomaly; the eastern, western, and southern rims have depths between 0,5 and 0,9 km. The maximum basement depth is found in the annular basin, which reaches about 1,4 km, caused by sediment constriction at the transient cavity together with specular pairs of radial faults that appear in the modification stage of the crater. This thickening of the sedimentary layers is observed in numerical experiments involving other similar structures, what reinforces the results here obtained. The brittle structures are responsible for the greatest depths in the annular basin region, and they promote a sediment constriction with horizontal radial tension. These observations allow us to characterize Araguainha as a brittle-ductile domain impact structure
DE: 0545 Modeling (4255)
DE: 0920 Gravity methods (1219)
DE: 1214 Geopotential theory and determination (0903)
DE: 8005 Folds and folding
SC: Tectonophysics [T]
MN: 2007 Joint Assembly