The Seismostratigrahy Sequence Model of the Rio Grande Cone, Brazil

Castillo, Luis ¹; Kazmierczak, Thais D.¹; Ruiz, Marvick ¹; Chemale, Farid ²
(1)Geophysics, Universidad Nacional de Colombia, Bogota, Colombia. (2) Geociencias, Universidade de Brasilia, Brasilia, Brazil.

The Rio Grande Cone feature is a large subsurface structure located on the southern continental platform of Brazil. By using seismic line and well log information, we present a seismoestratigraphy sequencial model of the Rio Grande Cone that integrates seismic attribute and seismic interpretation. The integration permits seismostratigraphy interpretation with the identification of sequences boundaries, system tracts and the depositional elements. Some of the geological and geomorphological characteristics obtained contribute to knowledge of the subsurface that has not been obtained with other exploratory methods. Such elements may include shale intrusions, contourites, listric faults, and bottom surface reflectors that comprise important elements of hydrocarbon traps. The Rio Grande Cone (RGC) extend seaward and contains fine-grained sediments. The RGC comprises the shelf to the northwest and the slope to the southeast, including the break shelf. An echelon, N-NE fault system controls the depocenters that developed across the southern offshore region of Brazil. It is possible identify at least two sequences. These sequences are thin at the near offset and have a pinched outer layer; at the far offset (seaward), where the sequences are thicker. Faults are well defined in these thicker areas and cut all of the Rio Grande Cone sequences. The Rio Grande Cone has been characterized seismo-stratigraphically as a sedimentary geoform from the Miocene era. From the Miocene until today, the Upper Rio Grande Cone has consisted of levees filled by sandstones and siltstone. The Intermediate Cone comprises the interdigitalization of semi-developed levees, with the stratification of sandstones and turbidities associated with the slope. The Lower Cone is a feature with smooth and plane topography supplied by hemipelagic muds and turbidites. Bottom surfaces, or contourites, have been reported along paleocurrent flows because of depositional gravitational processes, such as negative paleotopography.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.