Provenance discrimination in late Quaternary sediments from the Amerasian Basin (Arctic Ocean) constrained by mineralogical record
Bibliographic record
Abstract
This study focuses on the determination of potential source areas for the terrigenous material derived from Eurasia and North America to reconstruct the circumArctic ice-sheet history and sedimentary processes in the Amerasian Basin of the Arctic Ocean during Quaternary times. Investigations are carried out on marine sediment cores recovered during the ARK-XXIII/3 (2008) Expedition of RV “Polarstern”. Coring sites are located along a transect at 77◦33,6’ N from the East Siberian Sea continental margin across the Mendeleev Ridge to the Chukchi Abyssal Plain (Stein et al., 2009). To determine the provenance of terrigenous material, we investigate the mineralogical composition of sediments and the petrography of rock clasts (IRD). In order to distinguish between different agents of particle transportation such as icebergs, sea ice and currents, we study the grain-size distribution of the sediments. Currently we report the results of the quantitative mineralogical analysis performed on bulk sediments using the X-ray diffraction (XRD) method as well as the distribution of coarse-grained material in different fractions separated via dry sieving. Our results provide an evidence for two different source areas for the terrigenous material deposited close to the East Siberian Sea continental margin. Sites located at the Mendeleev Ridge and to the east are characterized by significant amount of dolomite probably supplied from the Canadian Arctic Archipelago (e.g., Phillips and Grantz, 2001). The dolomite-rich layers (also referred to as pink-white layers; Clark et al., 1980) are consistent with MIS 6/5, 4/3 and 3/2 transitions. The gravel and pebble size of dolomite suggests transport by icebergs due to the collapse of the Laurentide Ice Sheet. These layers enriched in detrital dolomite cannot be traced to the west of the Mendeleev Ridge where the coarse fraction is dominated by quartz. Only the transition MIS 3/2 is marked by higher input of dolomite. Such sedimentation patterns can be explained by the influence of the two major systems of surface ocean currents and ice motion in the Arctic Ocean, the Beaufort Gyre and the Transpolar Drift. In this case, Mendeleev Ridge represents a boundary zone for the sediment pathways which probably have shifted with time due to the relocation of the front between the Atlantic and the Pacific water domains in the Arctic Ocean (Macdonald et al., 2000, and references therein). Future detailed microscopy studies of the coarse fraction will comprise detailed identification and quantification of IRD in order to provide important background provenance information for reconstructions of the extension of the ice masses which grounded on the Mendeleev Ridge and adjacent shelf areas in the late Quaternary as recorded by acoustic profiling (Stein et al., 2009).
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".