Abstract
We present three new high-precision U–Pb zircon chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS) dates from western European Carboniferous diagenetically altered volcanic ash layers (bentonites and tonsteins) that occur interbedded with cyclic siliciclastic sedimentary rocks. The dates constrain the average periodicity of western European late Carboniferous (Arnsbergian to early Langsettian) cyclic sedimentation to between 89 and 124 ka per cycle. This is consistent with the 100 ka ‘short’ eccentricity Milankovitch cycle and supports previous suggestions that the cycles are the product of glacio-eustasy. Cyclostratigraphic tuning of Namurian cycles to the 100 ka eccentricity cycle revises the timing of the global Mississippian–Pennsylvanian boundary to c . 323.9 Ma. CA-ID-TIMS dates also facilitate correlation between different facies belts where biostratigraphical correlations are difficult. Correlation between eastern and western European sequences confirms that the base of the Moscovian stage is located within the Duckmantian (Westphalian B) western European regional substage. Supplementary materials: Zircon separation and concentration procedures, U–Pb zircon CA-ID-TIMS methods and data table, average periodicity calculations for western and central European Namurian and Westphalian sedimentary cycles, and procedures for recalibrating legacy 40 Ar/ 39 Ar dates are available at www.geolsoc.org.uk/SUP18547 .
Highlights
The timescale for late Mississippian and Pennsylvanian strata of western and centralEurope assigned to the Namurian and Westphalian regional stages is poorly constrained because of the paucity of precise isotopic ages
We present new high-precision dates determined by the U–Pb zircon CA-ID-TIMS
Technique from three western European diagenetically altered volcanic ash horizons. These dates are used to determine the average periodicity of western European late Carboniferous (Arnsbergian to Duckmantian) sedimentary cycles
Summary
The timescale for late Mississippian and Pennsylvanian strata of western and centralEurope assigned to the Namurian and Westphalian regional stages is poorly constrained because of the paucity of precise isotopic ages. 1984; Hess & Lippolt 1986), and by the U–Pb zircon Sensitive High Resolution Ion. Microprobe (SHRIMP) method, from the 1990s (e.g. Riley et al 1993; Claoué-Long et al 1995). Microprobe (SHRIMP) method, from the 1990s (e.g. Riley et al 1993; Claoué-Long et al 1995) Modern U–Pb zircon CA-ID-TIMS dating can yield ages with. We present new high-precision dates determined by the U–Pb zircon CA-ID-TIMS technique from three western European diagenetically altered volcanic ash horizons (bentonites and tonsteins). These dates are used to determine the average periodicity of western European late Carboniferous (Arnsbergian to Duckmantian) sedimentary cycles. The new data yield dates bracketing the global Mississippian-
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