Anaerobic degradation of organic matter controlled by productivity variation in a restricted Late Triassic basin

Vetö, István; Hetényi, Magdolna; Hámor-Vidó, Mária; Hufnagel, Heinz; Haas, János

doi:10.1016/s0146-6380(00)00011-5

Cited by 14 publications

(6 citation statements)

References 27 publications

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“…3, 4) representing the uppermost part of the Rezi Dolomite, the TOC ranges from 0.7 to 6.8%. The organic matter is predominantly of marine origin (unicellular planktonic algae) and immature (R o 0.32-0.34%; Vető et al 2000;Hetényi et al 2002). Ostracodes occur in some layers in rock-forming quantity (Budai et al 1999b).…”

Section: Geological Settingmentioning

confidence: 99%

Dolomitization of Late Norian carbonate deposits of restricted basin facies in the Keszthely Mts., Transdanubian Range, Hungary

Haas

Budai

Hips

et al. 2021

Int J Earth Sci (Geol Rundsch)

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In the Transdanubian Range (Hungary), a wide spectrum of Triassic dolomites is known. Mechanism of dolomitization of the platform carbonate successions was subject of a number of studies but the study of dolomitization of basinal carbonates is very limited. Petrographical and isotope–geochemical characteristics of the Upper Triassic dolomitized carbonate deposits, formed in a fault-controlled intraplatform basin, and interpretation of the dolomite-forming processes are presented in the current paper. From the latest Carnian to Middle Norian under semi-arid climatic conditions density-driven flux of seawater derived mesohaline fluids was the dominant mechanism of the near-surface pervasive dolomitization of the thick platform carbonate succession. In the late Middle Norian incipient rifting of the Alpine Tethys led to establishment of an extensional structural regime and onset of the formation of the Kössen Basin. In the study area, above the dolomitized platform carbonate succession, platform-derived carbonate sediments were accumulated in a fault-bounded, semi-restricted sub-basin of the Kössen Basin, whereas talus breccias and debrites were deposited near a basin-bounding master fault. The basin deposits (lower and upper members of the Rezi Dolomite Formation) were subject of early diagenetic dolomitization in shallow burial setting. Enhanced salinity seawater was the dolomitizing fluid; the synsedimentary fracturing may have promoted the fluid flow and thereby the dolomitization. Thick-bedded carbonates (middle member of the Rezi Dolomite Formation) representing a progradational tongue of the ambient platform are intercalated between the basin deposits. The dolomitization of this unit can be explained by the reflux model.

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Section: Geological Settingmentioning

confidence: 99%

Dolomitization of Late Norian carbonate deposits of restricted basin facies in the Keszthely Mts., Transdanubian Range, Hungary

Haas

Budai

Hips

et al. 2021

Int J Earth Sci (Geol Rundsch)

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“…A szerves kén és szén atomaránya (S/C) 200 métertől kezdődően 0,04 feletti, és ennél fogva a kénben dús, IIS típusú kerogén jelenlétét jelzi (VETŐ et al 2000) (4. ábra). Az említett szakaszban (>200 m) a kőzetek karbonáttartalma 60% feletti, kisebb mélységben viszont 20-60% közötti, lényegesen alacsonyabb.…”

Section: A Hi éS S/c Adatok Trendjeiunclassified

Anyakőzet-tulajdonságok és termikus átalakulások a Kösseni Formációban

Koncz¹

2021

Földt. Közl.

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Az olaj-anyakőzet korrelációk eredményei szerint a Nagylengyelben felfedezett nehéz-olajat a Kösseni Formáció generálta. A Rock-Eval adatok és a szerves kén-szén atomarányok alapján a Kösseni Formáció alsó része a Rezi-1 fúrásban magas szénhidrogén-potenciálú és a kénben dús, IIS típusú kerogén jelenlétét mutatja. Felhasználva a Bak-Nova árokban lévő Kösseni Formáció eltemetődési történetét és a IIS típusú kerogénnek megfelelő kinetikai konstansokat, a nehéz-olaj képződése a felsőkréta időszakban, 70°C hőmérsékleten ért véget. Az olaj ilyen korai képződése a kénben dús, IIS típusú kerogén jelenlétének köszönhető. A nehéz-olajnak a túlnyomás által létrehozott primer migrációja egybeesik a nehéz-olajban lévő aszfaltének bomlása kezdetével. A Kösseni Formáció felrepedése a pórusokban jelen lévő olaj térfogat-növekedése miatt előállt nyomásnövekedésnek köszönhető, ami az aszfaltén-bomlás következménye. A Kösseni Formáció kerogénjének termikus átalakulása gáz-képződéssel zárul a legalább 1.3 % vitrinitreflexiónak megfelelő magasabb termikus érettségi szinteken.

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“…T max measurements for samples of the Middle and Upper Menilite suggest a higher thermal maturity than for Lower Oligocene (Lower Menilite) samples, despite being younger. This may be attributed to a deeper structural position in the lowermost tectonic slice in the Skyba nappe, or to differences in facies; for example, source rocks with a higher sulphur content may display lower T max values (Vetö et al, 2000). This is noticeable in the Upper Menilite Member.…”

Section: Maturitymentioning

confidence: 99%

The Oligocene–miocene Menilite Formation in the Ukrainian Carpathians: A World‐class Source Rock

Rauball

Sachsenhofer

Bechtel

et al. 2019

Journal of Petroleum Geology

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This study investigates the hydrocarbon potential of Oligocene–Miocene shales in the Menilite Formation, the main source rock in the Ukrainian Carpathians. The study is based on the analysis of 233 samples collected from outcrops along the Chechva River in western Ukraine in order to analyse bulk parameters (TOC, Rock‐Eval), biomarkers and maceral composition. In Ukraine, the Menilite Formation is conventionally divided into Lower (Lower Oligocene), Middle (Upper Oligocene) and Upper (Lower Miocene) Members. The Early Oligocene and Early Miocene ages of the lower and upper members are confirmed by new nannoplankton data. The Lower Menilite Member is approximately 330 m thick in the study area and contains numerous chert beds and turbidite sandstones in its lower part together with organic‐rich black shales. The shales have a high content of silica which was probably derived from siliceous micro‐organisms. The TOC content of the shales frequently exceeds 20 wt.% and averages 9.76 wt.%. HI values range between 600 and 300 mgHC/gTOC (max. 800 mgHC/gTOC). The Middle Member contains thin black shale intervals but was not studied in detail. The Upper Member is about 1300 m thick in the study area and is composed mainly of organic‐rich shales. Chert layers are present near the base of the Member, and a prominent tuff horizon in the upper part represents a volcanic phase during shale deposition. The member grades into overlying molasse sediments. The average TOC content of the Upper Menilite succession is 5.17 wt.% but exceeds 20 wt.% near its base. Low Tmax and vitrinite reflectance measurements for the Lower (419°C and 0.24–0.34 %Rr, respectively) and Upper (425°C and 0.26–0.32 %Rr, respectively) Menilite Member successions indicate thermal immaturity. Biomarker and maceral data suggest a dominantly marine (Type II) organic matter input mixed with varying amounts of land‐plant derived material, and indicate varying redox and salinity conditions during deposition. Determination of the Source Potential Index (SPI) shows that the Menilite Formation in the study area has the potential to generate up to 74.5 tons of hydrocarbons per m2. The Chechva River outcrops therefore appear to have a significantly higher generation potential than other source rocks in the Paratethys realm. These very high SPI values for the Menilite Formation may explain why a relatively small area in Ukraine hosts about 70% of the known hydrocarbon reserves in the northern and eastern Carpathian fold‐thrust belt.

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Anaerobic degradation of organic matter controlled by productivity variation in a restricted Late Triassic basin

Cited by 14 publications

References 27 publications

Dolomitization of Late Norian carbonate deposits of restricted basin facies in the Keszthely Mts., Transdanubian Range, Hungary

Dolomitization of Late Norian carbonate deposits of restricted basin facies in the Keszthely Mts., Transdanubian Range, Hungary

Anyakőzet-tulajdonságok és termikus átalakulások a Kösseni Formációban

The Oligocene–miocene Menilite Formation in the Ukrainian Carpathians: A World‐class Source Rock

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