Widespread basement erosion during the late Paleocene-early Eocene in the Laramide Rocky Mountains inferred from 87Sr/86Sr ratios of freshwater bivalve fossils
Bibliographic record
Abstract
Research Article| September 01, 2011 Widespread basement erosion during the late Paleocene–early Eocene in the Laramide Rocky Mountains inferred from 87Sr/86Sr ratios of freshwater bivalve fossils Majie Fan; Majie Fan † Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA †E-mail: mfan1@uwyo.edu Search for other works by this author on: GSW Google Scholar Jay Quade; Jay Quade Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar David Dettman; David Dettman Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar Peter G. DeCelles Peter G. DeCelles Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Majie Fan † Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Jay Quade Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA David Dettman Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Peter G. DeCelles Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA †E-mail: mfan1@uwyo.edu Publisher: Geological Society of America Received: 07 Dec 2009 Revision Received: 10 Jun 2010 Accepted: 25 Jun 2010 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2011 Geological Society of America GSA Bulletin (2011) 123 (9-10): 2069–2082. https://doi.org/10.1130/B30219.1 Article history Received: 07 Dec 2009 Revision Received: 10 Jun 2010 Accepted: 25 Jun 2010 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Majie Fan, Jay Quade, David Dettman, Peter G. DeCelles; Widespread basement erosion during the late Paleocene–early Eocene in the Laramide Rocky Mountains inferred from 87Sr/86Sr ratios of freshwater bivalve fossils. GSA Bulletin 2011;; 123 (9-10): 2069–2082. doi: https://doi.org/10.1130/B30219.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Reconstruction of the timing and pattern of exhumation of basement-involved uplifts during the Laramide is essential to the understanding of the mechanisms of crustal shortening and thickening in the region. We use reconstructions of the 87Sr/86Sr ratios of Late Cretaceous–early Cenozoic river water from fossil shells in six basins of the Rocky Mountains contextualized by modern river-water Sr chemistry studies to trace the erosion of Precambrian basement cores in the Laramide ranges. The 87Sr/86Sr ratios and Sr concentration of modern river water in the Rocky Mountains are controlled by river bedrock lithology. Weathering of Precambrian silicate rocks in the cores of Laramide ranges produces high 87Sr/86Sr ratios in highland rivers. Weathering of Paleozoic and Mesozoic carbonates along the basin margins reduces the 87Sr/86Sr ratios and increases Sr concentration of rivers as they flow basinward. Lowland rivers that have headwaters in Precambrian basement mostly have 87Sr/86Sr ratios >0.711, whereas rivers confined to or with very long reaches in basins have 87Sr/86Sr ratios between 0.709 and 0.711. River-water δ18O values do not change in response to changes in catchment elevation.Our results from fossil shells show that carbonate weathering dominated the river-water Sr chemistry in the Alberta Foreland, Williston, and Crazy Mountains Basins, and that Proterozoic low-grade metamorphic carbonates in the Belt-Purcell Supergroup were not exposed in the Canadian Rocky Mountains during Late Cretaceous–early Paleocene time. Silicate weathering influenced the Sr chemistry of surface waters in the Powder River Basin during the late Paleocene and the Washakie Basin during the early Eocene, suggesting Precambrian silicate basement rock was extensively exhumed and eroded. The observation that Precambrian basement was eroded earlier around the Powder River Basin than around the Washakie Basin is consistent with a previous study that suggests Laramide ranges in northeast Wyoming reached high elevation earlier than the ranges adjacent to the Sevier thrust belt. Widespread basement erosion in late Paleocene–early Eocene time was controlled by tectonic exhumation, and may have been intensified by the wet and warm global climate. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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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 | 0.003 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".