Dr. Aaron Meilijson
Affiliated researcher
Ari has been implementing sedimentological, stratigraphic and geo-biological tool-sets into the study of diverse geological systems, spanning the Triassic to Upper Miocene, to try and understand paleoclimates and their influence on the biosphere. Ari is specifically interested in the interrelationship between productivity, bottom water environments and organic matter quality, quantity, preservation and source. His work has shown that the biochemical reciprocity of present and deep-time marine systems is found to be extremely complex and dynamic. Moreover, his work on Paleozoic, Mesozoic, and Cenozoic deposits has shown that sustained life, one of the key factors in depositional reconstructions, is found to be very resilient by using remarkable adaptations to cope with, and even thrive in, stressed and extreme environments. Ari is a field and core-analysis geologist, and his dogma is based on a multi-proxy approach as an essential step in the fields of sedimentology, basin analysis and paleoceanographic reconstructions, particularly when studying 'abnormal' organic-rich or hypersaline environments.
His last post-doctoral position was at the Organic and Isotopic Geochemistry Laboratory headed by Prof. Julio Sepúlveda in the INSTAAR institute at CU Boulder, USA. There he focused on the extraction and analysis of organic-matter preserved within an Upper Miocene and onshore organic-rich Eocene sections from the Levant Basin, Cretaceous to Miocene sediments from the Eratosthenes Seamount (Cyprus), and Lower Cretaceous deposits from northern Israel. Today he consults to the oil industry with hydrocarbon exploration, and he also works as an independent consultant in managing geological projects at different localities across the globe.
Research at PetroLab
Cyclo-stratigraphy and biomarkers of Messinian evaporites in the deep Eastern Mediterranean
The Messinian Salinity Crisis (MSC) is considered to be an extreme environmental event driven by changes in climate and tectonics, which affected global ocean salinity and shaped the biogeochemical composition of the Mediterranean Sea. Yet, after more than 50 years of research, the MSC stratigraphy is still controversial. Recent studies agree that the transition from the underlying pre-pvaporite sediments to thick halite deposits is continuous in the Mediterranean. However, the age of the base and the duration of halite deposition are still unclear. The nature of the upper MSC unit, characterized from seismic data as a period of increased clastic deposition into the eastern Mediterranean, is also disputed. We summarize a multidisciplinary study of sedimentary, geochemical and geophysical data from industrial offshore wells in the Levant Basin, which recovered a sedimentary record of deep-basin Mediterranean evaporites deposited during the MSC. Combining the newly analyzed dataset with previous MSC knowledge gathered throughout the Mediterranean promotes the need for a new chronological model. Remarkably, the one-kilometer-thick lower part of the evaporitic unit is composed solely of halite, other than a thin transitional anhydrite layer at its base. The halite is undisturbed and homogeneous, lacking diverse features apparent in more proximal sections, indicating a deep sea depositional environment. Distinct several meters thick non-evaporitic intervals interbedded with the halite, previously thought to be clastic layers, are identified here as diatomites. While XRD analysis confirms an increase in clastic components, these sediments are composed primarily of very well preserved marine and freshwater planktonic diatom species. The occurrence of marine planktonic diatoms, reported only from Pre-Evaporite and Lower Gypsum marginal deposits, indicates input of Atlantic waters into the Mediterranean Basin during early stages of the MSC. Seismic and well log cyclostratigraphy further support deep basin halite deposition, which started about 300 kyr earlier than widely assumed. We propose that halite deposition in the deep Mediterranean took place during stage 1 and 2 of the MSC, rather than being limited to the short 50 kyr MSC acme when sea level is presumed to have been at its lowest. Thus, brine formation, salt precipitation, and faunal extinction occurred at least in part in a deep, non-desiccated basin, with a restricted yet open Mediterranean-Atlantic connection that allowed inflow of oceanic water. We observe an increase in heavy minerals and reworked fauna within the clastic-evaporitic upper part of the basinal MSC section, correlating well to the Upper Gypsum and Lago-Mare interval in marginal sections. This correlation is also corroborated by chemostratigraphic markers, such as the distribution of n-alkanes and organic matter maturity indices based on sterane and hopane biomarkers. This review modifies the current understanding of the mechanisms governing salt deposition throughout the MSC with implications for other evaporitic events in the geologic record.