Re-Os geochronological evidence for oil generation during the early Oligocene in the South Llanos basin of Colombia: Insights into the Understanding of giant heavy oil accumulations in northwestern South America
Bibliographic record
Abstract
The Southern Province of the onshore Llanos Basin of Colombia is characterized by accumulations of heavy-biodegraded oils (<20°API gravity oils) sourced from Upper Cretaceous rocks localized in the adjacent Eastern Cordillera. There are some uncertainties regarding the precise age of oil generation in this sector of the Llanos Basin, however, previous time-temperature models have restricted the timing of oil generation to the Paleogene . Re-Os geochronology in crude oils has shown promising potential to directly determine the age of hydrocarbon generation , migration, or charge in basins with complex tectono-sedimentary settings. Here, we conducted Re-Os isotopic analyses in 29 oil samples from the Castilla, Peguita, and Rubiales oilfields to constrain the timing of hydrocarbons generation in the Southern Province of the Llanos Basin. The Re-Os isotopic data yield an isochron age of 28.9 ± 4.4 Ma, consistent with basin evolution models that support a maximum thermal maturity reached by source rocks of the Eastern Cordillera in the Early Oligocene . This age also seems to precede the onset of exhumation of the Eastern Cordillera at ca. 25 Ma, providing new chronological controls to constrain the timing of cessation of oil generation by Upper Cretaceous rocks. This study highlights the applicability of the Re-Os geochronometer to (1) constrain the temporal evolution of petroleum systems in the Llanos Basin, and (2) evaluate the influence of exhumation of the Eastern Cordillera in the development of petroleum kitchens in the adjacent foreland basin . The new data are instrumental in confirming the evolutionary models of the giant heavy oil accumulations of the South Llanos Basin.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".