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Reference
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| Title: |
Report on Referred Fossils
,
1985
(04/12)
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Sample was crushed, acidized and centrated in heavy liquids in the USGS laboratories in Denver. |
| Report by: |
Kirk E. Denkler
,
Anita G. Harris
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| Referred by: |
David A. Brew
,
Norman J. Silberling
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| | Age: | Ladinian-Carnian (late Ladinian - early Carnian) |
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| CAI: | Min: 5 (CAI=very 5 indicating host rock reached at least 300 deg. C) |
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| Comment: | Several kilograms of rock was processed from a sample that contained "a scrap of an ornate ammonite that is taken to be of late Ladinian age" according to Norm Silberling; this sample yielded enomous numbers of conodonts. Only 5% of the sample was picked and produced:
99% Neogondolella polygnathiformis (Budurov & Stefanov)
1% Xaniognathus sp.
The known range of N. polygnathiformis is late Ladinian through early Norian. Early morphotypes of N. polygnathiformis have anterior platform margins that are smooth and keels that are rounded posteriorly according to Tim Carr (ARCO, Dallas); these forms appear to be restricted to the late Ladinian but may extend into the Karnian. A younger morphotype of N. polygnathiformis has anterior platform margins with incipient nodes or crenulations and a keel that is squared off and may even bifurcate posteriorly. These forms appear to be restricted to the late Karnian through early Norian. Your sample is dominated by early forms of N. polygnathiformis with relatively few specimens of a more advanced morphotype. The safest age call appears to be late Ladinian through early Karnian. We have sent a cut of your essence of conodont to Tim Carr for corroborative analysis.
Age: late Ladinian-early Karnian.
CAI=very 5 indicating host rock reached at least 300o C |
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