Large-magnitude Miocene extension of the Eocene Caetano caldera, Shoshone and Toiyabe Ranges, Nevada
Bibliographic record
Abstract
Because major mineral deposits in northcentral Nevada predate signifi cant Basin and Range extension, a detailed understanding of the timing and kinematics of extensional faulting is necessary to place these deposits in their original structural context.The complexity of pre-Cenozoic deformation in northern Nevada makes restoring Basin and Range faulting diffi cult without locating well-dated, regionally extensive Cenozoic units that can be used to restore slip along normal faults.The goal of this study is to reconstruct extensional faulting in the Shoshone and northern Toiyabe Ranges by using Cenozoic rocks in and around the Caetano caldera, which formed ca.33.8 Ma during eruption of the Caetano Tuff.The caldera fi lled with more than 4 km of intracaldera tuff during initial caldera-forming eruptions, and additional sedimentary and volcanic rocks subsequently fi lled the topographic depression left by the caldera collapse.These rocks are conformable over the interval 34-25 Ma, consistent with little, if any, extension during that time.The 34-25 Ma rocks were later cut by a set of closely spaced (1-3 km) normal faults that accommodated signifi cant extension and footwall rotations of 40º-50º.Restored structural cross sections indicate that the present ~42 km (east-west) width of the Caetano caldera has been extended 110%, resulting in 22 ± 3 km westward translation of the Fish Creek Mountains relative to the southern Cortez Range.Major normal faults mapped within the caldera continue south and north along strike into the surrounding Paleozoic basement rocks; therefore it is likely that parts of surrounding areas are also signifi cantly extended.Miocene (16-12 Ma) sedimentary rocks in the hanging walls of major normal faults include both fl uvial/lacustrine facies and coarser alluvial fan deposits.Where exposed, the bases of the Miocene sedimentary sections are in angular conformity with underlying ~40°E tilted 34-25 Ma volcanic and sedimentary rocks.The distribution, composition, and geometry of these deposits are best explained by accumulation in a set of half-graben basins that formed in response to slip on basin-bounding faults.Extension thus appears to have taken place in the middle Miocene, beginning at or shortly after 16 Ma, and was mostly completed by 10-12 Ma.Fault blocks and basins formed during middle Miocene extension are cut by younger, more widely spaced, high-angle normal faults that began forming more recently than 10-12 Ma.These faults outline the modern basins and ranges in the study area and some have remained active into the Holocene.
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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 | 0.001 | 0.000 |
| 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".