A New Calibration Point for the Late Cretaceous Time Scale: The 40Ar/39Ar Isotopic Age of the C33r/C33n Geomagnetic Reversal from the Judith River Formation (Upper Creataceous), Elk Basin, Wyoming, USA

1995 ◽  
Vol 103 (3) ◽  
pp. 243-256 ◽  
Author(s):  
Jason F. Hicks ◽  
John D. Obradovich ◽  
Lisa Tauxe
Keyword(s):  
Late Cretaceous ◽  
Time Scale ◽  
Calibration Point ◽  
Isotopic Age ◽  
Geomagnetic Reversal ◽  
Judith River Formation

EVIDENCE FOR TREMATODE PARASITISM IN LATE CRETACEOUS (CAMPANIAN) FRESHWATER BIVALVES FROM THE JUDITH RIVER FORMATION, MONTANA

2017 ◽  
Author(s):  
Raymond R. Rogers ◽  
◽  
Kristina Curry Rogers ◽  
Michal P. Zaton ◽  
Jeffrey T. Thole ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Freshwater Bivalves ◽  
Judith River Formation

A new K—Ar age from uppermost Tremadoc rocks of north Wales

1982 ◽  
Vol 119 (2) ◽  
pp. 207-211 ◽  
Author(s):  
B. P. Kokelaar ◽  
F. J. Fitch ◽  
P. J. Hooker
Keyword(s):  
Time Scale ◽  
Calibration Point ◽  
Volcanic Group ◽  
North Wales ◽  
Scale Calibration ◽  
Lower Palaeozoic ◽  
New Time

SummaryNew conventional K–Ar dating of virtually unaltered pargasite phenocrysts extracted from a metabasalt of the uppermost Tremadocian Rhobell Volcanic Group, cropping out near Dolgellau, Gwynedd, north Wales, yields an age of 508 ± 11 Ma. This result provides a valuable new time-scale calibration point although incompatible with some other versions of the radiometric time-scale for the Lower Palaeozoic which have indicated ages of less than 508 ± 11 Ma for the Tremadoc/Arenig boundary.

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