Chemostratigraphy And Geochemical Constraints On The Deposition Of The Bakken Formation, Williston Basin, Eastern Montana And Western North Dakota
Bibliographic record
Abstract
The late Devonian-early Mississippian Bakken Formation was deposited in a structural-sedimentary intracratonic basin that extends across a large part of modern day North Dakota, eastern Montana, and the southern portion of Canada's Saskatchewan Province. The deposition of the Bakken Formation occurred during a fascinating period of geologic time that is linked to one of the five major mass extinctions. The occurrences of these mass extinctions are recorded worldwide as organic rich mud rocks similar to the ones found in the Bakken Formation. Collectively, the Bakken Formation consists of a middle dolomitic siltstone that is representative of a transgressive deposit and is bound by regressive organic rich mud rocks deposits that were influenced by rapid flooding events induced by the late Devonian-early Mississippian seaway. Geochemical proxies, total organic carbon and stable isotopic results that were recovered from four cores provide insight into the paleoenvironmental conditions during the deposition of the Bakken Formation. Geochemical analysis and interpretation of sample suites exhibit aggregate mineralogical composition from related shifts in elemental concentrations in weight percent (wt. %) consisting of magnesium (Mg), calcium (Ca), silicon (Si), aluminum (Al) and iron (Fe). The occurrence of chemostratigraphic shifts from concentrations of the Bakken Formation's bulk rock mineralogical composition represent facies changes of sedimentary packages within the middle Bakken and are linked to dolomite, calcite, quartz, pyrite, and clay (mainly illite) content. Furthermore, geochemical proxies of redox sensitive elements expressed as enrichment factors (EF) brought insight into the redox conditions during deposition of the upper and lower Bakken shales across the Williston Basin (e.g., Mo, U, V, Zn, Ni, and Cu). Molybdenum-total organic carbon (Mo-TOC) relationships, established two separate anoxic episodes that are represented by the Bakken shales and also provided insight into the degree of basin restriction the Williston Basin experienced during late-Devonian-early Mississippian time. Observed geochemical Mo-TOC relationships from the Bakken shales display similar trends of basin restriction comparable to modern silled basin analogues, specifically the Cariaco Basin (Algeo et al. 2006). The elemental shifts from Mo-TOC vs. depth profiles, demonstrate that the Bakken shales were deposited under semi-restricted conditions. Furthermore, Mo-TOC relationships also inferred water mass residence times and variable hydrographic mixing from deep basin waters from the Williston Basin. TOC and stable isotopic composition of TOC (δ¹³C) from the Bakken shales were utilized as geochemical proxies to examine the change and distribution of organic matter across the Williston Basin. Lastly, stable isotopic composition of TOC results potentially demonstrate a blend of kerogen source formed from marine organic matter (plankton) and land-plant lipids based on previous studies.
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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".