Terrestrial cosmogenic nuclide dating of ice-marginal moraines can provide unique insights into Quaternary glacial history. However, pre- and post-depositional exposure histories of moraine boulders can introduce geologic uncertainty to numerical landform ages. To avoid geologic outliers, boulders are typically selected based on their depositional context and individual characteristics but while these criteria have good qualitative reasoning, many have not been tested quantitatively. Of these, boulder location is critical, as boulders located on moraine crests are prioritised, while those on moraine slopes are typically rejected. This study provides the first quantitative assessment of the relative utility of moraine crest and moraine slope sampling using new and published ¹⁰Be and ³⁶Cl ages (n = 19) and Schmidt hammer sampling (SH; n = 635 moraine boulders, ∼19,050 SH R-values) in the northern and southern Pyrenees. These data show that for many of the studied moraines, the spatial distribution of “good” boulders is effectively random, with no consistent clustering on moraine crests, ice-proximal or -distal slopes. In turn, and in contrast to prior work, there is no clear penalty to either moraine crest or moraine slope sampling. Instead, we argue that landform stability exerts a greater influence on exposure age distributions than the characteristics of individual boulders. For the studied landforms, post-depositional stability is strongly influenced by sedimentology, with prolonged degradation of matrix-rich unconsolidated moraines while boulder-rich, matrix-poor moraines stabilised rapidly after deposition. While this pattern is unlikely to hold true in all settings, these data indicate that differences between landforms can be more significant than differences at the intra-landform scale. As ad hoc assessment of landform stability is extremely challenging based on geomorphological evidence alone, preliminary SH sampling, as utilised here, is a useful method to assess the temporal distribution of boulder exposure ages and to prioritise individual boulders for subsequent analysis.

冰缘冰碛的陆地宇宙成因核素测年可以提供对第四纪冰川历史的独特见解。然而，冰碛巨石沉积前和沉积后的暴露历史会给数值地貌年龄带来地质不确定性。为避免地质异常值，通常根据其沉积背景和个体特征选择巨石，但虽然这些标准具有良好的定性推理，但许多标准尚未经过定量测试。其中，巨石位置至关重要，因为位于冰碛顶部的巨石会被优先考虑，而位于冰碛斜坡上的巨石通常会被拒绝。本研究使用新发布的¹⁰ Be 和³⁶Cl 年龄 ( n = 19) 和施密特锤取样 (SH; n = 635 冰碛巨石, ∼19,050 SH R-values）在北比利牛斯山和南比利牛斯山。这些数据表明，对于许多研究的冰碛，“好”巨石的空间分布实际上是随机的，在冰碛顶部、近冰或远侧斜坡上没有一致的聚类。反过来，与之前的工作相反，对冰碛顶部或冰碛坡度采样没有明显的惩罚。相反，我们认为地形稳定性对暴露年龄分布的影响大于单个巨石的特征。对于所研究的地貌，沉积后稳定性受到沉积学的强烈影响，富含基质的松散冰碛长期降解，而富含巨石、基质贫乏的冰碛在沉积后迅速稳定。虽然这种模式不太可能在所有环境中都适用，这些数据表明，地貌之间的差异可能比地貌内部尺度的差异更显着。由于仅根据地貌证据对地貌稳定性进行临时评估极具挑战性，因此这里使用的初步 SH 采样是评估巨石暴露年龄的时间分布和确定单个巨石的优先级以进行后续分析的有用方法。