Age-depth modelling

The newly updated inventory of palaeoecological research in Latin America offers an important overview of sites available for multi-proxy and multi-site purposes. From the collected literature supporting this inventory, we collected all available age model metadata to create a chronological database of 5116 control points (e.g. 14 C, tephra, fission track, OSL, 210 Pb) from 1097 pollen records. Based on this literature review, we present a summary of chronological dating and reporting in the Neotropics. Difficulties and recommendations for chronology reporting are discussed. Furthermore , for 234 pollen records in northwest South America, a classification system for age uncertainties is implemented based on chronologies generated with updated calibration curves. With these outcomes age models are produced for those sites without an existing chronology, alternative age models are provided for researchers interested in comparing the effects of different calibration curves and age–depth modelling software, and the importance of uncertainty assessments of chronologies is highlighted. Sample resolution and temporal uncertainty of ages are discussed for different time windows, focusing on events relevant for research on centennial-to millennial-scale climate variability. All age models and developed R scripts are publicly available through figshare, including a manual to use the scripts.

Over the last 20 years, the geoarchaeology of ancient harbours has been a very active area of research around the Mediterranean basin, generating much palaeoenvironmental data from many sites, including estimations of sedimentation rates, the height of the ancient sea-level at different dates and palaeo-geographical reconstructions. Combining this information has proved a major challenge. This article proposes a new chart called the Palaeoenvironmental Age-Depth Model (PADM chart), that allows the researchers to combine all relevant indicators in order to estimate harbour potential of a given ancient port, and to generate comparable data between harbours in terms of degree of closure and water depth available against a synchronised chronology. This new approach, developed in the context of the ERC-funded RoMP Portuslimen project, takes into account estimations of water depths relating to differing Roman ship draughts at different periods. It is tested against the palaeoenvironmental evidence published over 10 years from two Roman harbours located at the mouth of the river Tiber: Ostia and Portus. This reveals that: (1) there has been an underestimate of the real sedimentation rates due to the margins of error of the radiocarbon dates; (2) there was effective control of the water column by dredging; (3) there were different periods of control of the sedimentation. We suggest that the navigability of the Ostia harbour by ships with shallower draughts was maintained until sometime between the 2nd c. BC and 1st c. AD, while at Portus it was retained until the 6th—7th c. AD.