Sequence Stratigraphic Correlation and Eustatic Events from Latest Cambrian to Early Early Ordovician between North China and Yangtze Platforms
Bibliographic record
Abstract
Four orthosequences have been recognized both from the Yeli Formation to the lower Liangjiashan Formation in northern and northeastern North China platform and from the upper Wuduhe Formation to the Fenxiang Formation in central Yangtze platform during the latest Cambrian to early Early Ordovician ( from the Fryxellodontus inornatus Subzone to Paltodus deltifer Zone ).δ 13 C value of carbonates from C.proavus Zone to C. angulatus Zone shows three rise and drop cyclic changes. Similar changes can be recognized during this interval in the δ 13 C profiles at Black Mountain, Australia, Lawson Cove , USA and Batyrbay , Kazakhstan .The simultaneous changes in carbon isotopes are useful in international correlation of the Cambrian Ordovician boundary strata . Based on the biostratigraphic data of conodonts and graptolites, and on the carbon isotopic stratigraphic data, four third order sequences could be well correlated on both platforms . During the latest Cambrian to early Early Ordovician ( from Fryxellodontus inornatus Subzone to Paltodus deltifer zone ), there existed 6 eustatic events : ( 1 ) the eustatic event ( equivalent to the Lange Ranch Eustatic Event in North America ) between the Fengshan Formation and the Yeli Formation, and in the upper part of the Wuduhe Formation (Lower C.proavus ; (2)the eustatic event between the First Member and the Second Member of the Yeli Formation and between the Wuduhe Formation and the Xilingxia Formation (between C. proavus Zone and C. intermedius Zone); (3) the regression event in the upper Xilingxia Formation on the Yangtzi platform (equivalent to the Aceroceras regression event in Australia);(4) the eustatic event between the Xilingxia Formation and the Nanjingguan Formation (between C. lindstromi Zone and C.angulatus Zone ), equivalent to the Black Mountain eustatic event in Australia; (5) the eustatic event between the Second Member and the Third Member of the Yeli Fomation, and between the Nanjingguan Formation and the Fenxiang Formation, the maximum transgression during Tremadocian occurred in the Psigraptus Zone to Adelograptus Zone; (6) the eustatic event between the lower and the middle Liangjiashan Formaion, and between the Fenxiang Formation and the Honghuayuan Formation (between Paltodus deltifer Zone and Serratognathus Zone) .At the Dayangcha section, in the lower C. lindstromi Zone which represents a maximum transgression period, there abundantly occurred the planktonic graptolite fauna of the Rhabdinopora flabelliformis parabola Zone which is significant for the global correlation. The maximum flood surface near this graptolite zone and below the FAD of C. prolindstromi could be taken as an important inference boundary for the Cambrian Or dovician Boundary. Iapeognathus fluctivagus in 23 bed of the Green Point section , Canada, has a limited distribution, and is not practical to be taken as an index fossil for the global correlation .
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".