Bibliographic record
Abstract
Abstract German geologists began to study rocks now recognized as Triassic during the late 1700s. In 1823, one of those German geologists, a very astute mining engineer named Friedrich August von Alberti (1795–1878), coined the term ‘Trias formation’ for an c . 1 km thick, tripartite succession of strata in southwestern Germany – the Bunten Sandsteins, Muschelkalk and Keuper of the German miners. Alberti also recognized Triassic rocks outside of Germany, throughout much of Europe and as far away as India and the United States. By the end of the nineteenth century, Triassic rocks had been identified across Europe and Asia, and in North America, South America and Africa. Indeed, in 1895, the Austrian geologist Edmund von Mojsisovics (1839–1907) and his collaborators published a complete subdivision of Triassic time based on ammonoid biostratigraphy and, in so doing, introduced many of the Triassic chronostratigraphic terms still used today. The twentieth century saw the elaboration of an ammonoid-based Triassic timescale, especially due to the work of Canadian palaeontologist E. Timothy Tozer (1928-). During the last few decades, work also began on developing a global magnetic polarity timescale for the Triassic, a variety of precise numerical ages tied to reliable Triassic biostratigraphy have been determined, and conodont biostratigraphy has become an important tool in Triassic chronostratigraphic definition and correlations. The current Triassic chronostratigraphic scale is a hierarchy of three series (Lower, Middle, Upper) divided into seven stages (Lower = Induan, Olenekian; Middle=Anisian, Ladinian; and Upper=Carnian, Norian, Rhaetian) further divided into 15 substages (Induan=upper Griesbachian, Dienerian; Olenekian=Smithian, Spathian; Anisian=Aegean, Bithynian, Pelsonian, Illyrian; Ladinian=Fassanian, Longobardian; Carnian=Julian, Tuvalian; Norian=Lacian, Alaunian, Sevatian). Ammonoid and conodont biostratigraphies provide the primary basis for the chronostratigraphy. A sparse but growing database of precise radioisotopic ages support these calibrations: base of Triassic c . 252 Ma, base Olenekian c . 251 Ma, base Anisian c . 247 Ma, base Ladinian c . 242 Ma, base Jurassic c . 201 Ma. A U/Pb age of c . 231 Ma from the Italian Pignola 2 section is lower Tuvalian, and U/Pb ages on detrital zircons from the nonmarine Chinle Group of the western USA of c . 219 Ma are in strata of late Carnian (Tuvalian) age based on the biostratigraphy of palynomorphs, conchostracans and tetrapods. These data support placement of the Norian base at c . 217 Ma, and indicate that the Tuvalian is more than 10 million years long and that the Carnian and Norian are the longest Triassic stages. Magnetostratigraphic data establish normal polarity for all of the Triassic stage bases except Anisian and Ladinian. An integrated biostratigraphic correlation web for the marine Triassic consists of ammonoids, bivalves, radiolarians and conodonts, whereas a similar web exists for the nonmarine Triassic using palynomorphs, conchostracans and tetrapods. Critical to cross correlation of the two webs is the Triassic section in the Germanic basin, where a confident correlation of nonmarine biostratigraphy to Triassic stage boundaries has been achieved. The major paths forward in development of the Triassic timescale are: finish formal definition of all Triassic stage boundaries, formally define the 15 Triassic substages, improve the integration of the Triassic biostratigraphic webs and develop new radioisotopic and magnetostratigraphic data, particularly for the Late Triassic.
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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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.006 | 0.008 |
| Science and technology studies | 0.002 | 0.003 |
| Scholarly communication | 0.005 | 0.006 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.002 | 0.005 |
| Insufficient payload (model declined to judge) | 0.018 | 0.006 |
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".