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Fallout radionuclides are being considered as potential global indicators of the beginning of the Anthropocene, yet questions persist about their preservation in bogs. This study assessed the reliability of 241Am records in peat cores from acidic, ombrotrophic bogs. The source of 241Am (half-life 432.7 years) in these natural archives is radioactive decay of the short-lived plutonium isotope 241Pu (half-life 14.329 years) present in fallout from the atmospheric testing of nuclear weapons. We leveraged previously gathered data to gauge the congruence of 241Am records with 210Pb dates, examining the alignment of the 241Am activity peak with the depth corresponding to the year AD 1963, as determined using the 210Pb constant rate of supply (CRS) model. Our analysis employed 35 peat cores from 30 sites across Europe and North America, collected over the last three decades for trace metal deposition studies. Each core underwent independent 210Pb dating. Among the 35 cores, 10 were excluded because of significant uncertainty in 241Am peak quantification. Among the remaining 25 cores, 22 displayed a single 241Am peak and 3 exhibited two peaks with similar 241Am activities. Of the 22 cores with a single peak, 18 were within 10 years of AD 1963, with 10 of those being within 5 years. For 10 of the 22 cores, 14C dates obtained from the atmospheric bomb pulse curve enabled comparison, with 9 showing ≤10 years of difference and 7 of those showing ≤5 years from the 210Pb CRS model AD 1963. Factors contributing to age discrepancies included (i) analytical limitations of 241Am measurements in peat using gamma spectrometry, (ii) the impact of peat accumulation rates on 241Am activities, i.e., dilution effects, (iii) post-depositional migration of 241Pu and (or) 241Am, (iv) uncertainties introduced during 210Pb age-modelling, and (v) the limited number of samples dated using 14C. The usefulness of 241Am as an Anthropocene marker (assuming AD 1963) hinges on the accepted uncertainty level in defining this epoch. Detection of 241Am through gamma spectrometry was statistically validated as a real peak in 22 out of a total of 35 cores: this fraction (63%) is within the range reported in other studies. Given that the cores were gathered from 16 European and 14 North American sites, these peaks can be taken to denote the hemispheric onset of the Anthropocene. Lastly, common post-depositional migration of 137Cs in ombrotrophic peatlands contrasts with its immobility in minerotrophic peatlands, where the presence of mineral matter and neutral pH inhibit its movement. This observation suggests that fens and swamps, characterized by minerotrophic conditions, may also serve as repositories of nuclear weapons test fallout, including 241Am. [ABSTRACT FROM AUTHOR]