Relating outcrop and subsurface expressions of the Magallanes-Austral Basin: Provenance of the eastern Magallanes-Austral Basin from detrital zircon U-Pb sediment core ages, Southern Patagonia
Abstract/Contents
- Abstract
- Analyzing how provenance signatures of tectonically complex ancient sedimentary basins vary between the outcrop and the subsurface is crucial to understanding basin filling history. The 500+ km-long outcrop belt of the Magallanes-Austral Basin in southern Patagonia and its subsurface to the east allows us to constrain relationships between longitudinal and transverse sediment sources feeding the basin. New detrital zircon U-Pb ages (n=2558) from nine subsurface core samples from the Springhill, Piedra Clavada, and La Anita Formations along a 140 km east-west seismic reflection transect (50°S latitude; 71.5-69.5°W longitude) reveal provenance and filling history of the basin’s eastern subsurface extent. Detrital zircon ages (n=1068) were also collected from four outcrop Springhill Formation samples 140 km northwest from the transect near Lago San Martin. Maximum depositional ages (MDAs) from the Springhill Formation cores range from 154.9–146.8 Ma, which are older than correlative outcrop ages of 144.6–126.7 Ma. MDAs from the Piedra Clavada and La Anita Formations range from 93.4–91.4 Ma and 78.9–78.3 Ma, respectively, and overlap in age or are slightly younger than outcrop ages. The unimodal Late Jurassic age distribution from the Springhill Formation suggests that it almost exclusively was sourced by recycling of its underlying El Quemado Complex and highlights the underfilled nature of the Rocas Verdes Basin. By the Early Cretaceous, detritus supplied to the basin was derived from the arc, fold and thrust belt, and distal synrift volcanic sources. The occurrence of Early–Middle Jurassic ages in the Piedra Clavada Formation samples suggest either the basin was sourcing from the North Patagonia Massif to the north-northeast and from the Deseado Massif to the northeast or recycling exhumed volcaniclastic sequences in the northern margin of the basin. By the Late Cretaceous, the basin fill was more locally sourced, as suggested by the muted signal of Early–Middle Jurassic ages in La Anita Formation samples and a second mode of Late Jurassic–Early Cretaceous ages locally derived from recycling exhumed El Quemado Complex from the fold and thrust belt. We suggest that the longitudinal and local transverse drainages that sourced the Magallanes-Austral Basin outcrop belt also propagated eastward across the basin (what is now subsurface strata). Distal sourcing from the North Patagonian Massif is determined by subsidence and bypass in the Golfo San Jorge Basin and existence of Albian–Turonian fluvial transport systems capable of transporting Jurassic sediment to the Magallanes-Austral Basin.
Description
| Type of resource | text |
|---|---|
| Publication date | December 8, 2023 |
Creators/Contributors
| Author | Gross Almonte, Nicholas |
|---|---|
| Contributor | Malkowski, Matthew |
| Contributor | Dobbs, Stephen |
| Thesis advisor | Graham, Stephan |
| Editor | McHargue, Timothy |
Subjects
| Subject | Detrital Zircon |
|---|---|
| Subject | Maximum Depositional Age |
| Subject | Magallanes-Austral Basin |
| Subject | Patagonia |
| Subject | Springhill Formation |
| Subject | La Anita Formation |
| Subject | Piedra Clavada Formation |
| Genre | Text |
| Genre | Thesis |
Bibliographic information
| Related item | |
|---|---|
| DOI | https://doi.org/10.25740/ks753pq1769 |
| Location | https://purl.stanford.edu/ks753pq1769 |
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- License
- This work is licensed under a Creative Commons Attribution Non Commercial 4.0 International license (CC BY-NC).
Preferred citation
- Preferred citation
- Gross Almonte, N., Malkowski, M., Dobbs, S., and Graham, S. (2023). Relating outcrop and subsurface expressions of the Magallanes-Austral Basin: Provenance of the eastern Magallanes-Austral Basin from detrital zircon U-Pb sediment core ages, Southern Patagonia. Stanford Digital Repository. Available at https://purl.stanford.edu/ks753pq1769. https://doi.org/10.25740/ks753pq1769.
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Master's Theses, Doerr School of Sustainability
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