Lacustrine organic carbon burial dynamics regulate Aptian-Albian greenhouse-cooling climate oscillations
Bibliographic record
Abstract
• Lacustrine biogeochemical and phytoplankton dynamics are different across Aptian and Albian. • Anoxic water columns and sufficient nutrient supply favor organic carbon burial. • Distinct roles in regulating Aptian-Albian greenhouse and cooling climates. Investigating terrestrial response to typical greenhouse periods is essential to understand past and present climate-carbon-cycle interactions. The Cretaceous climate transition is thought to be related to carbon cycles, yet the role of lacustrine systems in modulating global carbon-climate feedback remains poorly constrained. Here, we present a high-resolution biogeochemical record from an Aptian-Albian paleolake in northwestern China, integrating biomarkers, nitrogen isotopes, and elemental proxies. We reveal that warm-humid climates during the early Aptian amplified lacustrine organic carbon burial via intensified denitrification, methane cycling, and nutrient fluxes, potentially reinforcing oceanic anoxic event 1a (OAE1a) hyperthermal conditions through N 2 O/CH 4 emissions. Subsequent nitrogen limitation triggered cyanobacterial dominance, sustaining carbon sequestration under moderate weathering and contributing to cooling the late Aptian climate. A transient early Albian warming phase shifted the nitrogen pool towards NH 4 + and favored the bloom of eukaryotic algae, aligning with global OAE1b carbon burial and serving as one of the contributors to the late early Albian cooling climate. These dynamics demonstrate that paleolakes acted as both carbon sinks and greenhouse gas sources, exerting a critical but previously overlooked feedback on Cretaceous climate oscillations. Our findings highlight the dual role of lacustrine systems in past carbon cycle perturbations, offering insights for refining the relationships between the carbon cycle and climate changes in the Cretaceous.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".