Pre-Messinian Deposits of the Mediterranean Ridge: Biostratigraphic and Geochemical Evidence from the Olimpi Mud Volcano Field

Anastasios Nikitas,Ioannis Hatzianestis,Alexandra Gogou,Grigoris Rousakis,Maria V Triantaphyllou,Nikolaos Pasadakis,Ioannis Panagiotopoulos

doi:10.3390/w13101367

Abstract

This study presents the results derived from micropaleontological and organic geochemical analyses of mud breccia samples obtained (through gravity coring) from five mud volcanoes (Gelendzhik, Heraklion, Moscow, Milano, Leipzig) located at the Olimpi mud volcano field on the Mediterranean Ridge accretionary complex. A thorough calcareous nannofossil semi-quantitative analysis was performed to determine the biostratigraphic assignment of the deep-seated source strata. Mudstone/shale clasts of different stratigraphic levels were identified and assigned to the Miocene nannofossil biozones CNM10, CNM8–9, CNM7, CNM6–7, and Oligocene CNO4/CNO5. A single mudstone clast from the Gelendzhik plateau, assigned to the biozone CNM10, demonstrated unique micropaleontological and geochemical characteristics, suggesting a sapropelic origin. Subsequently, the total organic carbon (TOC) content and thermal maturity of the collected mud breccias was evaluated using the Rock-Eval pyrolysis technique, and their oil and gas potential was estimated. The pyrolyzed sediments were both organic rich and organic poor (TOC >0.5% or <0.5%, respectively), with their organic matter showing characteristics of the type III kerogen that consists of adequate hydrogen to be gas generative, but insufficient hydrogen to be oil prone. However, the organic matter of the late Serravallian (CNM10) sapropelic mudstone was found to consist of a mixed type II/III kerogen, implying an oil-prone source rock.

Highlights

Introduction and Geotectonic SettingMud volcanoes (MVs) are very common structures on the eastern Mediterranean seafloor, distributed in areas under a compressional tectonic regime
More than 250 MVs have been identified on the Mediterranean ridge (MR), while such structures are absent throughout the neighboring tectonically inactive Hellenic backstop, even though extensional stresses may prevail in places
100–200 g of material was initially recovered from 14 mud breccia facies and, clasts were carefully removed from the sediment matrix

Summary

Introduction

Mud volcanoes (MVs) are very common structures on the eastern Mediterranean seafloor, distributed in areas under a compressional tectonic regime. More than 250 MVs have been identified on the Mediterranean ridge (MR), while such structures are absent throughout the neighboring tectonically inactive Hellenic backstop, even though extensional stresses may prevail in places. Many studies have been carried out during the past decades in order to determine the MVs’ spatial distribution in the eastern Mediterranean basin (Figure 1) (e.g., [1,2,3,4,5]), their sedimentological and geochemical characteristics [6,7,8,9,10], and their possible relation to gas hydrates and gas seeps [11,12,13,14,15]. In the Miocene–early Pliocene, crustal extension in Crete caused the uplifting of the lower nappes [22,24], and sedimentary basins were developed onshore and offshore (backstop area) Crete and Peloponnese

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Conclusion