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| Content Provider | Springer Nature Link |
|---|---|
| Author | Swisher, C. C. Wang, Xiaolin Zhou, Zhonghe Wang, Yuanqing Jin, Fan Zhang, Jiangyong Xu, Xing Zhang, Fucheng Wang, Yuan |
| Copyright Year | 2002 |
| Abstract | We report new $^{40}$Ar÷$^{39}$Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion $^{40}$Ar÷$^{39}$Ar dating of biotite, argues for a Jurassic age for the Yixian Formation. The third tuff is a previously undated tuff from the upper part of the underlying Tuchengzi Formation. Single crystal total fusion $^{40}$Ar÷$^{39}$Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca÷K ratios, excellent reproducibility and gave a mean age of 125.0±0.18 (1SD)±0.04 (SE) Ma. Single sanidine crystal total fusion $^{40}$Ar÷$^{39}$Ar analyses of the Hengdaozi tuff gave a mean age of 125.0±0.19 (1SD)±0.04 (SE) Ma, which is indistinguishable from the Sihetun tuff. The Tuchengzi Formation tuff gave a mean age of 139.4±0.19 (1SD)±0.05 (SE) Ma. Detailed laser incremental-heating analyses of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components. We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of the Tuchengzi Formation can be referred to the Early Cretaceous. |
| Starting Page | 136 |
| Ending Page | 139 |
| Page Count | 4 |
| File Format | |
| ISSN | 10016538 |
| Journal | Chinese Science Bulletin |
| Volume Number | 47 |
| Issue Number | 2 |
| e-ISSN | 18619541 |
| Language | English |
| Publisher | Science in China Press |
| Publisher Date | 2002-01-01 |
| Publisher Place | Beijing |
| Access Restriction | Subscribed |
| Subject Keyword | $^{40}$Ar÷$^{39}$Ar dating Cretaceous Yixian Formation Tuchengzi Formation western Liaoning Science Life Sciences Physics Chemistry/Food Science Geosciences Engineering |
| Content Type | Text |
| Resource Type | Article |
| Subject | Multidisciplinary |
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