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Το πετρελαιογεωλογικό δυναμικό των κλαστικών Νεογενών σχηματισμών των Ιζηματογενών λεκανών της ΒΔ Κρήτης

Telemenis Dimosthenis

Πλήρης Εγγραφή

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Περίληψη

Crete is one of the largest islands in Mediterranean Sea, located in the Eastern part of it and it is considered of great geological aspects.The geological evolution and conditions that shaped the Neogene paleoenvironmental history of the Mediterranean Sea, have been investigated so far by numerous researchers. The Upper Miocene particularly (late Tortonian and early Messinian) was generally characterized by the rapid building of extensive carbonate platforms and basins which included hemipelagic formations (marls/mudstones, sapropels), as well as shallow-marine deposits (evaporitic formations, coral reefs, bioclastic and red algae limestones). This study focuses on three sedimentary sections in those (marginal) Neogene basins on NW part of Crete in the Prefecture of Chania and their hydrocarbon prospectivity.More specifically, these Neogene basins, in which the sections are contained, are Apokoronas (Kalyves), Kalydhonia and Afrata basins. A macroscopically description of lithologies and sediments has been occurred in all three outcrops and also a geochemical analysis has been conducted.The studied outcrops pinpoint an Upper Miocene (Tortonian/Messinian) pre-evaporitic age of the deposits. Kalyves section is well-laterally extended, presents adequate thickness and is subdivided into three subsections and four profiles (due to dense vegetation and steepness), while the other two are clearly more narrow and continuous. Stratigraphic analysis of the outcrops illustrates clear alternations of fine sands, siltstones/mudstones and laminated diatomaceous beds from bottom to top in each subsection in Apokoronas basin, mudstones alternating with sandstones in Kalydhonia Basin and mud/clay/siltstones beds interchanges with sandstones in Afrata Basin. Bulk sampling of 48 samples has been carried out in the three outcrops. In more detail, 28 samples in the synthetic section of Kalyves, 9 samples in the section of Kalydhonia, 7 samples from Afrata section and 5 extra samples from area near Kalyves section were collected. For this set of samples, geochemical analysis has been fulfilled by the means of Rock-Eval 6 pyrolysis to facilitate the understanding of hydrocarbon potential. Total organic carbon (TOC) values of the samples reach up to 3.3 %. As a result, a kerogen type of II-III, leaning towards type III is documented by the analyzed samples of Kalyves section. The sets of samples of the other two sections indicate a kerogen type IV in both of them.Based on the analysis several outcomes have been made. This study supports and reports the extent of Messinian Diatomites in Western Crete. The stratigraphic analysis of the Kalyves section establishes System Tracts (ST), with a transgressive ST in the bottom part of the section, followed by a Highstand to Regressive ST in middle and top parts. Moreover, it is indicated the potential of Diatomites as source rock for hydrocarbon generation. In addition, a distribution of new potential gas/oil sources in different areas of District of Chania (Western Crete) is demonstrated. That also declares the high significance for the offshore hydrocarbon exploration in the Eastern Mediterranean, and especially in offshore Western Crete.

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