Plio-Pleistocene Outer Arc Basins in Southern Central America (Osa Peninsula, Costa Rica)
- L. E. Frostick4 and
- R. J. Steel5
Published Online: 16 APR 2009
Copyright © 1993 The International Association of Sedimentologists
Tectonic Controls and Signatures in Sedimentary Successions
How to Cite
von Eynatten, H., Krawinkel, H. and Winsemann, J. (1994) Plio-Pleistocene Outer Arc Basins in Southern Central America (Osa Peninsula, Costa Rica), in Tectonic Controls and Signatures in Sedimentary Successions (eds L. E. Frostick and R. J. Steel), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304053.ch21
- Published Online: 16 APR 2009
- Published Print: 28 FEB 1994
Print ISBN: 9780632037452
Online ISBN: 9781444304053
- Plio-Pliocene outer-arc basins in southern Central America;
- Osa Peninsula;
- plate tectonic setting;
- regional tectonic framework;
- Punta la Chancha;
- Playa Sombrero section
The Osa Peninsula forms part of the outer fore-arc area of the southern Central American isthmus near the triple junction of the Cocos, Nazca and Caribbean plates. Increasing northward drift rates at the eastern part of the Cocos Plate since Early Pliocene times has resulted in oblique subduction between the Cocos and Caribbean plates, producing trench-parallel dextral strike-slip faults in the fore-arc area. The Plio-Pleistocene sedimentary succession of the Osa Peninsula was deposited in two fault-bounded basins.
1 In the southern part of the Peninsula sedimentation was dominated by coarse-grained mass flow deposits, characteristic of coarse-grained delta and submarine fan depositional systems. Clast composition shows exclusive recycling of outer arc material. The overall retrogradational stacking patterns display clear deepening-upward trends, while high sedimentation rates continue. Therefore most probably strong basinal subsidence occurred, owing to the formation of a ‘stepped fan system’ seaward of a cliff-lined faulted slope.
2 In the eastern part of the Peninsula, Early Pliocene deposits start with a small coarse-grained deltaic section, overlain by 430 m of shelf deposits with intercalated tempestites. Aggradational stacking patterns as well as high sedimentation rates reflect high subsidence rates within an open marine embayment. Facies architecture and sedimentation style suggest deposition in a pull-apart basin. This basin opened within the outer fore-arc area in a trench-parallel direction.
The Osa arc area has been recently affected by strong uplift and arcward tilting caused by the subduction of the aseismic Cocos Ridge, which started 1 My ago. These subduction-related processes have superimposed the former strike-slip basin geometry. Major faults are now mainly perpendicular to the trench, following the direction of the Cocos Ridge.