Abstract

Detailed geochemical analysis of the turbidite-associated shales of the Cretaceous Katafito Formation, Greece, reveals important details regarding the paleoenvironment, paleoproductivity, and regional tectonics of the Pindos Basin. The Katafito Formation was deposited along an active margin at the early onset of closure of the Tethys Sea in the Pindos sub-basin. While careful studies of the coarse clastic component of turbidites are common, this study consisted of a detailed geochemical characterization of the fine-grained portions, which helped reveal paleoenvironmental information about the basin. This study combined organic and inorganic geochemistry utilizing elemental, mineralogical, and organic chemical signatures from fine-grained turbidite-associated sediments across six regional outcrops; three in the Peloponnese region and three in the Eprius region of Greece. In addition, shales from two outcrops associated with shallow marine deposits were sampled from Crete in the absence of identified turbidite outcrops and were used as reference point for geochemical indicators. In total 117 shale samples were analyzed via X-ray florescence (XRF) for elemental quantification, X-ray powdered diffraction (XRPD) for quantitative phase analysis of the minerals present, and Rock-Eval Pyrolysis for organic quality and type. Chemical trends between northern and southern outcrops reveal details about the tectonics, climate, and ocean circulation of the Pindos sub-Basin during the Cretaceous. Potassium feldspar and plagioclase feldspar show distinct trends between northern and southern outcrops, with a relative decrease in plagioclase to the north despite the source terrain becoming more mafic toward the north. This decrease in plagioclase to the north could show that the mountains were more developed in the north during the Cretaceous, leading to a higher orographic effect and the resulting increase in precipitation rates and the associated increase in weathering rate. Geochemical proxies for paleo-oxygenation (U/Th, V/Cr, Authigenic uranium, and degree of pyritization) are similar in abundance between northern Pindos, southern Pindos, and Crete samples, but using a Kolmogorov-Smirnov test at the 99% confidence level, these proxies show that the northern part of the basin was more oxic than the south at the time of deposition. This is interpreted to show that although the Pindos Basin waters were still well-oxygenated and in communication across the study area, the early signs of tectonic constriction were beginning to be seen in the north during the Late Cretaceous. Most samples contain less than 0.5% total organic carbon (TOC) based on Rock-Eval analysis, with a median of 0.36% and IQR of 0.29-0.47%. This could be the result of either low primary productivity or efficient recycling of organic matter in oxic conditions. However, paleo-TOC indicators such as nickel enrichment suggest that total organic carbon was likely 2-3% higher at time of deposition, which, given the interpretation that waters were dominantly oxic, suggests high primary productivity rates at the time of deposition. The large discrepancy between original and preserved TOC is at least partially explained by the high thermal maturation of the samples (Tmax median of 591Â°C and IQR of 594-437Â°C), suggesting that hydrocarbons have been generated and migrated out of the shales. Lastly, based on elevated calcium carbonate concentrations measured in shale samples and common preservation of detrital carbonate grains in the associated turbidite sandstones, along with the regional prevalence of time-equivalent limestones preserved across much of Greece and the broader region, it is interpreted that the turbidites of the Katafito Formation were deposited basinward of a well-developed carbonate shelf, and that siliciclastics were efficiently transported across this shelf through well developed and focused transport fairways.

Degree

College and Department

Physical and Mathematical Sciences; Geological Sciences

Rights

https://lib.byu.edu/about/copyright/