Tectonic assembly of east-central Alaska: Evidence from Cretaceous–Tertiary sandstones of the Kandik River terrane
Bibliographic record
Abstract
Research Article| July 01, 2000 Tectonic assembly of east-central Alaska: Evidence from Cretaceous–Tertiary sandstones of the Kandik River terrane Mark J. Johnsson Mark J. Johnsson 1Department of Geology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2000) 112 (7): 1023–1042. https://doi.org/10.1130/0016-7606(2000)112<1023:TAOEAE>2.0.CO;2 Article history received: 06 Jun 1998 rev-recd: 14 Jun 1999 accepted: 14 Jul 1999 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Mark J. Johnsson; Tectonic assembly of east-central Alaska: Evidence from Cretaceous–Tertiary sandstones of the Kandik River terrane. GSA Bulletin 2000;; 112 (7): 1023–1042. doi: https://doi.org/10.1130/0016-7606(2000)112<1023:TAOEAE>2.0.CO;2 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 East-central Alaska is a tectonically significant region between parautochthonous North America and the Arctic Alaska terrane to the north. The tectonic evolution of the area is recorded in Late Jurassic to early Tertiary sedimentary rocks of the Kandik River terrane. Fine-grained clastic rocks deposited in the area from Late Jurassic to Valanginian time represent a continuation of the passive margin sequence that persisted since the late Precambrian on the nearby North American margin. A pulse of quartz arenites (sandstones in the uppermost Glenn Shale and the Keenan Quartzite) reflects Valanginian rift-shoulder uplift, marking initiation of crustal upwarping and thinning that would later lead to the opening of the Canada basin. Fine-grained turbidites interpreted as distal submarine fan deposits (Biederman Argillite), Valanginian to possibly as young as Aptian, were next deposited along the passive margin. These quartz wackes contain framework grains with the same continental source as the quartz arenites, but geochemical evidence points to arc detritus in the fine-grained (pelagic) intervals. Compressional tectonics began in the Aptian, and are recorded by arc-derived volcaniclastic turbidites (Kathul Graywacke) that were quickly overthrust, buried to depths of 5–8 km, then uplifted and eroded in the Late Cretaceous. These events record the accretion of a previously unreported island arc to the Porcupine and Kandik River terranes, followed by accretion of this complex to North America. A second orogenic event followed in the latest Cretaceous to early Tertiary, when extension, possibly associated with emplacement of Yukon-Tanana terrane along the Tintina fault to the south, produced a half graben (Nation River basin) and a pull-apart basin that were filled with litharenites derived from local sources (unit TKs). These deposits were broadly uplifted and warped in the middle Tertiary, probably by regional Laramide-age events. These results are significant in that they provide evidence for a previously unreported Aptian–Albian volcanic arc in east-central Alaska. In addition, comparison of sedimentation events in east-central Alaska with those recorded in the North Slope sequence of northern Alaska provides constraints on tectonic models for the evolution of northern Alaska. 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 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) | 0.018 | 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".