Two Carboniferous Ages: A Comparison of Shrimp Zircon Dating with Conventional Zircon Ages and 40Ar/39Ar Analysis
Published:January 01, 1995
Jonathan C. Claoué-Long, William Compston, John Roberts, C. Mark Fanning, 1995. "Two Carboniferous Ages: A Comparison of Shrimp Zircon Dating with Conventional Zircon Ages and 40Ar/39Ar Analysis", Geochronology, Time Scales and Global Stratigraphic Correlation, William A. Berggren, Dennis V. Kent, Marie-Pierre Aubry, Jan Hardenbol
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Using replicate measurements of a homogeneous reference zircon, the discrimination of Pb+ and UO+ ions relative to U+ observed in zircon analysis with the SHRIMP ion microprobe has been established as a power law relationship. This relationship minimizes uncertainty in comparative measurement of 206Pb/238U ages in zircons. Ages thus obtained have been compared with isotope dilution thermal ionisation mass spectrometric (1DTIMS) analysis of zircons in the Paterson Volcanics (Carboniferous, Australia) and 40Ar/39Ar dating of sanidines in the Z1 tonstein (Carboniferous, Germany). No bias can be detected between the three dating methods, confirming that SHRIMP zircon 206Pb/238U ages are accurate and comparable with other well-measured Phanerozoic ages.
The age of the Westphalian B Stage of Europe is constrained by the Z1 tonstein; SHRIMP zircon analysis supports the 40Ar/39Ar age of 311 Ma and improves on its precision by a factor of two. The Paterson Volcanics mark both the Australian base of the Kiaman magnetic superchron and onset of the major, Late Palaeozoic period of Gondwana glaciation; SHRIMP and 1DTIMS zircon dating reassign these processes to the Namurian from the late Westphalian assignment used until now for global correlations.
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Geochronology, Time Scales and Global Stratigraphic Correlation
Geochronology, Time Scales, and Global Stratigraphic Correlation - The last decade has witnessed significant advances in analytic techniques and methodologic approaches to understanding earth history. This publication is a well-constructed geochronologic framework that allows estimation of rates of geologic processes, correlation of stratigraphies, and placement of discrete events in temporal order. Resulting from a research symposium at the 67th Annual SEPM meeting in New Orleans, Louisiana, April 1993, the 16 papers of this volume represent a broad spectrum of approaches to understanding earth history and the passage of geologic time.