Stratigraphic Implications of Meteoric Sphaerosiderite δ18O Values in Paleosols of the Cretaceous (Albian) Boulder Creek Formation, NE British Columbia Foothills, Canada
Bibliographic record
Abstract
Abstract The MD 80-08 coal exploration core from the Albian Boulder Creek Formation of northeastern British Columbia contains 90 m of alluvial strata that underwent extensive pedogenic modification. Gleyed colors, pedogenic slickensides, clay coatings, mottling, sphaerosiderite, and sedimentary pyrite characterize the paleosols. The isotopic compositions of 30 sphaerosiderite-bearing horizons commonly show trends of invariant δ18O and variable δ13C values. Equal-area plots of δ18O vs. δ13C were used to construct meteoric sphaerosiderite lines (MSLs). The MSLs indicate that meteoric groundwater compositions ranged from approximately -11‰ to -16‰ (SMOW). The sphaerosiderite δ18O values indicate formation in shallow groundwaters predominantly recharged by local precipitation. The sphaerosiderite isotopic compositions are a proxy record of mid-Cretaceous precipitation, and are useful for quantifying changes in the hydrologic cycle during humid "greenhouse" periods. Micromorphology of a 1.15 meter interval (69.75-68.6 m), with a +1.31‰ increase in the average δ18O values, records a polygenetic history of paleosol development. The pedocomplex has a four-stage developmental history characterized by: (1) an initial well-drained phase, with wet-dry cycles and relatively low baselevel; (2) erosion, baselevel rise and coarser-grained sedimentation; (3) saturated, reducing soil conditions, high baselevel, with some marine influence on pedogenesis; and (4) meteoric-water-dominated hydromorphic soil conditions, high baselevel, and sphaerosiderite precipitation. The δ18O excursion recorded through this interval reflects minor mixing of marine and meteoric groundwaters. The modal abundance of pyrite, and increased Mg/(Ca + Mg) and Mg/Fe cation ratios in the sphaerosiderites further substantiate marine influence on pedogenesis. The alluvial section of the Boulder Creek Formation is aggradational, and several changes in baselevel recorded in the paleosols are interpreted to have been driven by minor (parasequence-scale) changes in relative sea level.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".