We present 22 U-series ages for a stalagmite from north-western Cuba based on multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) and thermal ionisation mass spectrometry (TIMS). Our results reveal that the stalagmite continuously grew within the last ~1400a. Low uranium content of the sample and thus, extremely low ²³⁰Th concentrations limit the precision and accuracy of ²³⁰Th/U-dating by TIMS. Samples measured by MC-ICPMS show a high variability of ²³²Th content along the growth axis with some sections significantly affected by initial ²³⁰Th from a detrital phase. An a-priori bulk earth ratio for (²³⁸U/²³²Th) cannot be used to accurately account for this initial ²³⁰Th. Using an age model based on the ²³⁰Th/U ages determined on samples with low or negligible ²³²Th concentration, we find that the (²³⁸U/²³²Th) activity ratio of the detrital phase is an order of magnitude larger than the bulk earth value, indicating the importance of an accurately determined correction factor.