Analysis of two arc-associated basins and onset of their deep-water stages: Magallanes Basin, Chile, and Talara Basin, Peru

The evolution and sedimentary successions of two distinct, yet kindred basins located in South America, the Magallanes Basin and the Talara Basin, have been re-visited and re-interpreted in this thesis.; Magallanes Basin is the southernmost of the Chilean-Argentinean basins. It is a foreland basin developed in a retroarc position with respect to the Andes. The Zapata Formation and the Punta Barrosa Formation, now part of the Ultima Esperanza fold thrust belt, recorded the Mesozoic evolution of the Andean Cordillera of southernmost Patagonia. The shale dominated Zapata Formation was deposited over 50--40 m.y. in an irregular extensional basin that was eventually bounded by an arc to the west in the Neocomian. The scarcity of sandstone in the Zapata Formation and the geochemical signature of the shale suggest a partitioned basin with prominent horsts, with sand deposition confined to sub-basins closer to the arc. Changes in sediment dispersal patterns related to the onset of Andean compression and formation of the Magallanes foreland basin are recorded by sediment of the overlying Punta Barrosa Formation. Its sediment composition confirms the presence of an arc, and detrital zircon data establishes a Turonian age for the onset of the southernmost Andes. Metamorphic terranes recognized in the Cordillera are also represented in sediment that reached the basin during Punta Barrosa deposition.; Talara Basin, located in a forearc position of the Andean Cordillera, is the northernmost of the Peruvian coastal basins. Its sedimentary fill records the influence of subduction tectonics and Andean orogenic phases. A Tertiary extensional phase formed a complex horst-graben system and partitioned the basin into localized depositional areas. Abrupt tectonic pulses punctuated the apparently constant subsidence related to normal faulting driven by subduction erosion. Eocene strata record transitions from deltaic and fluvial to deep-marine depositional environments as a response to relative sea-level changes controlled by tectonics.; Petrographic and geochemical data indicate changes in source terranes at major unconformities. A sharp change in provenance signature for the Talara Group is interpreted as an effect of plate rearrangement during the Middle Late Eocene and to the onset of the Inca orogenic phase with uplift in the arc region.