Evaluating 14C and 14C/10Be terrestrial age dating systems for meteorites using experimental data and model calculations

Abstract

This study presents a refined approach to determine ¹⁴C saturation activities and ¹⁴C/¹⁰Be saturation activity ratios in chondritic meteorites with the goal to improve terrestrial age dating. By combining new model calculations for ¹⁰Be, ¹⁴C, and cosmogenic (²²Ne/²¹Ne)_cos, along with experimental data from 17 freshly fallen chondrites, we established reliable correlations for ¹⁴C production rates and ¹⁴C/¹⁰Be production rate ratios as a function of (²²Ne/²¹Ne)_cos. The experimental data agree with the model calculations, and they fully confirm that ¹⁴C production rates and ¹⁴C/¹⁰Be production rate ratios depend on shielding. Constrained correlations describe the experimental data for all shielding conditions and all ordinary chondrites mostly within the uncertainties given by the model. The new correlations therefore provide a significant improvement compared to the earlier approaches, in which average meteorite-type-dependent ¹⁴C production rates and average ¹⁴C/¹⁰Be production rate ratios were assumed. Ignoring the shielding dependence introduces a size-dependent bias into the terrestrial age database. This study enables the determination of shielding-corrected ¹⁴C saturation activities and ¹⁴C/¹⁰Be production rate ratios to calculate shielding-corrected terrestrial ages for meteorites reducing or eliminating a size bias in the database. In addition, this novel approach enables to give reliable uncertainty estimates of within 15% for the ¹⁴C and ¹⁴C-¹⁰Be terrestrial ages.