Sergipe-Alagoas Basin
From Wikipedia, the free encyclopedia
| Sergipe-Alagoas Basin | |
|---|---|
| "Bacia de Sergipe-Alagoas" | |
 | |
  | |
| Coordinates | 9°11′13″S 37°35′30″W / 9.18694°S 37.59167°W |
| Etymology | Sergipe and Alagoas |
| Location | South America |
| Region | Northeast |
| Country |  Brazil |
| State(s) | Sergipe, Alagoas, Pernambuco |
| Characteristics | |
| On/Offshore | onshore and offshore |
| Boundaries | Pernambuco Lineament & Itapuã Fault |
| Area | ~20,000 km2 (7,700 sq mi) to ~50,000 km2 (19,000 sq mi) |
| Geology | |
| Basin type | Rift basin |
| Plate | South American |
| Orogeny | Break-up of Gondwana |
| Age | Proterozoic-Recent |
| Stratigraphy | Stratigraphy |
The Sergipe-Alagoas Basin is a continental margin basin in the Sergipe and Alagoas states of northeastern Brazil, about 20 to 50 kilometres wide onshore, but with its widest extension offshore,[1] more precisely 13,000 km2 onshore and 40,000 km2 offshore.[2] In general, "Sergipe-Alagoas Basin" refers to the Sergipe and Alagoas sub-basins, but it also consists of the Jacuípe and Cabo sub-basins. Studies of the basin's geology date back to the first half of the 19th century, when J. Henderson in 1821 published preliminary notes on the region's geology.
The basin formed during the opening of the South Atlantic Ocean in the Late Jurassic and Cretaceous periods alongside other basins in the Brazilian coast.[1]
Studies of the basin's geology date back to the first half of the 19th century, when J. Henderson in 1821 published preliminary notes on the region's geology, but the first geological and paleontological surveys were carried out in 1865–1866 by the Canadian naturalist Charles Frederick Hartt, a participant of the Thayer Expedition. The results of this expedition were published in the book “Geology and Physical Geography of Brazil” from 1870, where it was described fossils of ammonites and a gastropod from the municipalities of Maruim and Larangeiras. With the Commissão Geológica do Império do Brazil, an expedition from 1875 and 1878 directed by Hartt, important studies were carried by the American palaeontologist Charles A. White, describing ammonites, bivalves, gastropods and echinoids. John Casper Branner published in 1890 a report on the Sergipe-Alagoas Basin about the localities of White's materials.[1]
Ralph Sopper published in 1914 the first geological map of the basin, but a more detailed map was published in 1924 by the “Serviço Geológico e Mineralógico do Brasil”.
Research of the Basin received strong motivation when search for petroleum begun in the 1940s, resulting in detailed maps and new fossil collections. Since 1953, the Brazilian Petroleum Company, PETROBRAS, produced various reports with the aim of improving knowledge of the region during the search for petroleum. Biostratigraphic studies by Karl Beurlen established a zonation of the Aptian-Albian Riachuelo Formation based on ammonites. He also published a number of subsequent studies from 1961 to 1968.[1]
Geological History
The geological evolution of the basin represents 5 tectonic stages: syneclise, pre-rift, rift, transitional and drift.[1]
1) Syneclise stage - Late Carboniferous to Early Permian - It is represented by the Batinga Formation, which probably was of glacial origin, which comprises siliciclastic rocks, and the Aracaré Formation, comprising eolian sandstones, shales and lacustrine algal laminites.
2) Pre-rift stage - Late Jurassic - Represented by the Candeeiro Formation, Bananeiras Formation and Serraria Formation, when crustal uplift resulted in a series of depressions which were filled by fluvial and lacustrine sediments.
3) Rift stage - Early Cretaceous - Represented by the Rio Pitanga Formation, Penedo Formation, Barra de Itiúba Formation and Coqueiro Seco Formation, increasing tectonism led to the formation of a rift-valley, the newly created rift was filled by an alluvial-fluvial-deltaic system.
4) Transitional stage - Early Aptian - Represented by the Muribeca Formation and Maceió Formation, the transitional stage began when the first marine sediments were deposited.
5) Drift stage - Early to mid Albian - Represented by the Riachuelo Formation, begun in the Albian, even though marine regime was established already in the late Aptian. Events during the Cenomanian and early Turonian cause the drowning of the Riachuelo platform system.
