Abstract
Although numerous pollen records are available worldwide in various databases, their use for synthesis works is limited as the chronologies are, as yet, not harmonized globally, and temporal uncertainties are unknown. We present a chronology framework named LegacyAge 1.0 that includes harmonized chronologies of 2831 palynological records (out of 3471 available records), downloaded from the Neotoma Paleoecology Database (last access: April 2021) and 324 additional Asian records. All chronologies use the Bayesian framework implemented in Bacon version 2.5.3. Optimal parameter settings of priors (accumulation.shape, memory.strength, memory.mean, accumulation.rate, thickness) were identified based on previous experiences or iteratively after preliminary model inspection. The most common control points for the chronologies are radiocarbon dates (86.1 %), calibrated by the latest calibration curves (IntCal20 and SHcal20 for the terrestrial radiocarbon dates in the northern and southern hemispheres; Marine20 for marine materials). The original literature was consulted when dealing with obvious outliers and inconsistencies. Several major challenges when setting up the chronologies included the waterline issue (18.8 % of records), reservoir effect (4.9 %), and sediment deposition discontinuity (4.4 %). Finally, we numerically compare the LegacyAge 1.0 chronologies to the original ones and show that the chronologies of 95.4 % of records could be improved according to our assessment. Our chronology framework and revised chronologies provide the opportunity to make use of the ages and age uncertainties in synthesis studies of, for example, pollen-based vegetation and climate change. The LegacyAge 1.0 dataset and R code used are open-access and available at PANGAEA (https://doi.pangaea.de/10.1594/PANGAEA.933132) and Github (https://github.com/LongtermEcology/LegacyAge-1.0), respectively.
Highlights
Global and continental fossil pollen databases are used for a variety of paleoenvironmental studies, such as past climate and biome reconstructions, palaeo-model validation, and the assessment of human-environmental interactions (Gajewski, 2008; Gaillard et al, 2010; Cao et al, 2013; Mauri et al, 2015; Trondman et al, 2015; Marsicek et al, 2018; Herzschuh et al, 2019)
Chronologies and control points are stored in these databases along with the pollen records
We report on the major challenges when setting up the chronologies and assess the quality of the LegacyAge 1.0 chronologies
Summary
Global and continental fossil pollen databases are used for a variety of paleoenvironmental studies, such as past climate and biome reconstructions, palaeo-model validation, and the assessment of human-environmental interactions (Gajewski, 2008; Gaillard et al, 2010; Cao et al, 2013; Mauri et al, 2015; Trondman et al, 2015; Marsicek et al, 2018; Herzschuh et al, 2019). Several fossil pollen databases have been successfully established (Gajewski, 2008; Fyfe et al, 2009), such as the European Pollen Database (http://www.europeanpollendatabase.net), the North American Pollen. The need for harmonized chronologies and an identical inference of temporal uncertainties have increased as studies are looking for spatiotemporal patterns using multi-record analyses (Jennerjahn et al, 2004; Blaauw et al, 2007; Giesecke et al, 2011; Flantua et al, 2016). Some efforts have been made to harmonize the chronologies for part of the data stored in the databases (Fyfe et al, 2009; Blois et al, 2011; Giesecke et al, 2011; Giesecke et al, 2014; Flantua et al, 2016; Brewer et al, 2017; Wang et al, 2019; Mottl et al, 2021). A harmonized chronology framework is needed, to allow for the consistent inference of age and age uncertainties and to apply to newly published records or one that can be adjusted to the specific requirement of a study
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