The Stratigraphic and Structural Evolution of the Central and Eastern Magallanes Basin, Southern South America
- P. A. Allen and
- P. Homewood
Published Online: 5 MAY 2009
Copyright © 1986 The International Association of Sedimentologists
How to Cite
Biddle, K. T., Uliana, M. A., Mitchum, R. M., Fitzgerald, M. G. and Wright, R. C. (1986) The Stratigraphic and Structural Evolution of the Central and Eastern Magallanes Basin, Southern South America, in Foreland Basins (eds P. A. Allen and P. Homewood), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303810.ch2
- Published Online: 5 MAY 2009
- Published Print: 22 DEC 1986
Print ISBN: 9780632017324
Online ISBN: 9781444303810
- stratigraphic and structural evolution of central and eastern Magallanes Basin, southern South America;
- Magallanes Basin - stratigraphy or structural and tectonic development of region;
- Tobifera Formation and older sedimentary rocks (Triassic to Upper Jurassic);
- Springhill and Lower Inoceramus Formations (Upper Jurassic to Lower Cretaceous);
- NW-trending shelf margin - subtle feature on seismic data;
- Margas Verdes and Middle Inoceramus Formations (mid-Cretaceous to mid-Late Cretaceous);
- Upper Inoceramus and Arcillas Fragmentosas Formations (mid-Coniacian to mid-Maastrichtian);
- Ballena, Tres Brazos, and Lena Dura Formations and Zona Glauconitica (mid-Eocene to Lower Oligocene);
- Magallanes Basin - foreland basin in front of Patagonian fold and thrust belt and southern Andes mountains
The Magallanes Basin is located at the southern edge of the South American plate and is underlain by crust of Palaeozoic age. The initial history of the basin is one of extension associated with the breakup of the South American sector of Gondwanaland. Triassic to Late Jurassic extension produced a normal-faulted terrane with numerous grabens and half grabens. This extensional event also resulted in extensive, dominantly silicic volcanism. The basin floor subsided from the Late Jurassic to the Late Cretaceous with decay of the thermal anomaly associated with extension. During the Late Cretaceous and Tertiary, uplift and shortening occurred along the western and southern edges of the basin, forming the Patagonian Andes and the fold and thrust belt of southernmost South America. Subsidence in the basin during this interval of time was the result of lithospheric flexure caused by loading.
The sedimentary fill of the basin is related to three major phases of basin development. The rift-related Triassic to Middle/Upper Jurassic succession consists of mostly non-marine volcanic and volcaniclastic rocks largely restricted to isolated grabens. Upper Jurassic to Upper Cretaceous, largely retrogradational sedimentary units were deposited while the basin passively subsided on the remnant-arc side of a small marginal sea. Uppermost Cretaceous and Tertiary units were derived from the south, west, and northwest, and show a progressive onlap geometry from west to east. These deposits mark the onset of sedimentation from the Andes, although subsidence caused by tectonic loading started somewhat earlier in the Late Cretaceous. Depositional patterns for this interval consist of fanglomerates separated by deep-water shales from an eastern complex of low sedimentation rate glauconitic sandstones which onlap a long-lived basement high. The most impressive feature formed during the foreland basin stage is a regional composite unconformity that separates rocks as old as Palaeocene from the Mesozoic section.
Production or shows of oil and gas occur in many of the stratigraphic sequences defined in the basin. The producing interval, the Springhall Sandstone, and the major source-rock units were deposited while the basin was a westward-facing remnant-arc margin. Burial of these rocks during the foreland basin stage led to the maturation and migration of hydrocarbons. Thus, the Magallanes Basin is a polyphase foreland basin and each phase of evolution has had a role in making the basin a productive one.