A complete database of AMS radiocarbon estimates from Lake Baikal sediment cores with a lake-wide assessment of TOC age offsets

Abstract. We present a database of AMS radiocarbon dates from Lake Baikal sediment cores, encompassing 51 cores and 518 dates, providing a complete record from literature spanning 1992 to 2025 (with transcription errors corrected) and including 22 previously unpublished dates from cores CON01-603-5 and CON01-605-5. The dataset is available at https://doi.org/10.1594/PANGAEA.973799 (Newall et al., 2025). The most common material used for radiocarbon dating in our dataset is total organic carbon (TOC). Unfortunately, the interpretation of TOC ages in lake sediments is hindered by issues such as the reservoir effect, in situ contamination by old organic carbon, and/or the hardwater effect. These issues may culminate in age estimates thousands of years older than the true depositional age of that sediment, which we term the “age offset”. Linear regression of uncalibrated radiocarbon dates has previously been used to estimate the age offset in Lake Baikal, with results ranging from 0 to 1.5 14C kyr in different cores. Estimates from other methods have returned estimates of approximately 2 14C kyr. Despite this, most previous studies have not incorporated age offset uncertainty in their age depth modelling, or have included uncertainty of, at most, ±0.09 14C kyr. Furthermore, the varying age offset estimates have been interpreted by some as evidence that different regions of Lake Baikal have different age offsets, with implications as to the cause of the age offsets. We apply the linear regression age offset method to all suitable cores in our database, returning 21 estimates of age offset from throughout the lake. Our results return a lake-wide TOC radiocarbon age offset of 1.62 ± 0.76 14C kyr, suggesting previous studies in Lake Baikal have significantly underestimated the temporal uncertainty of radiocarbon ages from TOC. Furthermore, we find no statistically significant evidence for a systematic difference in age offset in different regions of Lake Baikal (specifically Academician Ridge and Buguldeika Saddle). Finally, our results are a caution that linear regression-based age offset estimates in lake sediments have a large uncertainty that might only be observable with multiple datasets.