SEDIMENTOLOGY, ICHNOLOGY AND SEQUENCE STRATIGRAPHY OF THE LOWER CAMBRIAN GOG GROUP, SOUTHERN ROCKY MOUNTAINS, CANADA
Bibliographic record
Abstract
The architecture, distribution and facies of sandstone bodies in the Gog Group of the southern Rocky Mountains of western Canada record the dynamics of sand movement on the broad continental shelf of West Laurentia during the Early Cambrian phase of worldwide transgression. This study focuses on the stratigraphy, sedimentology and ichnology in the Bow Valley region, specifically the sector from Mount Assiniboine northwest to the North Saskatchewan River. The objectives of this project were several-fold: (1) revise the existing stratigraphic nomenclature; (2) document the sedimentary facies; (3) identify facies assemblages and interpret them in terms of sedimentary processes and environments; (4) characterize sandstone body geometries; (5) develop a sequence-stratigraphic framework; (6) document trace-fossil occurrences; and (7) characterize different trace-fossil assemblages in terms of colonization trends and prevailing paleoenvironmental conditions. The Gog Group in this area has historically comprised four units, the Fort Mountain, Lake Louise, St. Piran and Peyto formations. North of Bow Pass an additional unit, the Jasper Formation, occurs below the Fort Mountain Formation and is related to accommodation created by active rift-faulting during the latest Neoproterozoic. In the Lake Louise and Lake O'Hara area, four new formal subdivisions within the St. Piran Formation are proposed: Lake O'Hara, Lake Oesa, Lake Moraine and Wiwaxy Peaks members. The sequence stratigraphy of tide-dominated setting has yet not been fully explored. The stratal architecture of the Lake O'Hara and Lake Oesa members reveals a new mechanism for the formation of the regressive surface of marine erosion landward of the lever point of balance between sedimentation and erosion in the subtidal environment. As the shoreline is forced to regress with falling sea level, the laterally continuous tidal flats advance and the preexisting shallow-subtidal compound dunes are scoured by strong tidal currents that carve gradually a new equilibrium profile. We argue that the accretion of intertidal flats on top of subtidal sands is an overlooked yet predictable component of falling-stage systems tracts in tide-dominated settings. The Gog Group also offers an opportunity to explore animal-sediment relationships in a high-energy setting, during the early phase of Phanerozoic diversification. The presence of constrasting ichnofabrics within a single Early Cambrian sand-sheet complex illuminates how the colonisation trends of suspension and detritus feeders were controlled by factors specific to the various subenvironments. The variety of sandbody types in the Gog Group reflects varying sediment supply and location on the inner continental shelf. Five types of compound cross-stratified sandstone are distinguished based on foreset geometry, sedimentary structures and internal heterogeneity. These represent five broad categories of subtidal sandbodies: (1) compound-dune fields; (2) sand sheets; (3) sand ridges; and (4) patchy dunes. Trace-fossil distribution in these tide-dominated sand bodies and adjacent sediments is mostly controlled by an interplay of substrate mobility, grain size, turbidity, water-column productivity, and sediment organic matter. Salinity is a critical factor in marginal-marine locations but played no role in this region of the shelf.
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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 | 0.002 | 0.004 |
| 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) | 0.001 | 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".