The Biomarker Inventory, Trace, and Source of Heinrich Events and Heinrich-type Layers (MIS 8-16) in the North Atlantic
Bibliographic record
Abstract
AB: Multiple cores from different locations in the North Atlantic were recovered during IODP Expeditions 303/306. We have investigated the biomarker distributions of identified Heinrich layers (HL) and ambient glacial/interglacial samples from Site U1305, located in the Labrador Sea in proximity to the former major iceberg discharge pathway derived via the Hudson Strait from the Laurentide-Ice-Shield (LIS).A unique association of a multitude of "petrogenic" compounds such as benzohopanes, D-ring monoaromatic 8,14-secohopanes, rearranged diasterenes, mono- and triaromatic steranes, isorenieratene-derivatives as well as characteristic pristane/n- C17 and pristane/phytane ratios ideally allows to distinguish organic matter from HL compared to adjacent samples. They therefore are regarded and can be used as organic-geochemical tracers not only for the occurrence of Heinrich Events of the last glacial cycle but also for older Heinrich-like events.We present a biomarker based high resolution record of such events during a time interval from about 320-460 kyr at Site U1313 (MIS 10-12) and an extended record (MIS 8-16) of Heinrich-type events from Site U1308, i.e. from positions near the Mid-Atlantic Ridge and distal to the LIS.In addition, the HL-specific biomarker association provides circumstantial evidence to derive from a relatively immature, Paleozoic marine rock deposited under occasional photic zone anoxic conditions, that is today located on the Laurentide/Canadian shield. Reinvestigation of available geologic and organic-geochemical data allowed narrowing down this assumed source to an Ordovician oil shale close to Hudson Strait, that indeed bears a striking resemblance in terms of biomarker distributions when compared to the specific association of compounds from samples of Heinrich Events.
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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 | 0.001 | 0.001 |
| 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".