Scientific drilling projects in ancient lakes: Integrating geological and biological histories

Sedimentary sequences in ancient or long-lived lakes can reach several thousands of meters in thickness and often provide an unrivalled perspective of the lake’s regional climatic, environmental, and biological history. Over the last years, deep drilling projects in ancient lakes became increasingly multi- and interdisciplinary, as, among others, seismological, sedimentological, granulometric, biogeochemical, climatic, environmental, and evolutionary information can be obtained from sediment cores. However, these multi- and interdisciplinary projects pose several challenges. The scientists involved typically approach problems from different scientific perspectives and backgrounds, and setting up the program requires clear communication and the alignment of interests. One of the most challenging tasks, besides the actual drilling operation, is to link diverse datasets with varying resolution, data quality, and age uncertainties to answer interdisciplinary questions synthetically and coherently. These problems are compounded by the increasing use of secondary datasets, i.e., datasets obtained independently of the drilling operation. Nonetheless, the inclusion of secondary data such as stable isotope information from fossils found in outcrops or genetic information from extant species as well as recent technological and methodological advances in paleolimnological studies such as subsurface biosphere approaches or statistical advances in dating of molecular phylogenies may help to achieve synthetic answers. Some of these approaches have started to revolutionize scientific drilling in ancient lakes, but at the same time they add a layer of complexity to core data generation and analysis. The enhanced opportunities presented by new scientific approaches to study the paleolimnological history of these lakes, therefore, come at the expense of higher logistic, communication, and analytical efforts. Here we review types of data that can be obtained in ancient lake drilling projects and the analytical approaches that can be applied to empirically and statistically link diverse datasets for creating an integrative perspective on geological and biological histories. In doing so, we highlight strengths and potential weaknesses of new methods and analyses, and provide recommendations for future interdisciplinary deep drilling projects.