25th International Meeting on Organic Geochemistry IMOG 2011

P-332
Source rock characterization and depositional environment of
The Middle Miocene Hirka Formation (Beypazari-Ankara/Turkiye)
Berna Yavuz Pehlivanli 1 , Ali Sari 2 , Şukru Koc 2
1 Bozok University, Department of Geological Engineering, 66100, Atatürk Yolu, Yozgat, Turkey, 2 Ankara
University, Faculty of Engineering, Department of Geological Engineering, Ankaka, Turkey (corresponding
author:bernayavuz80@gmail.com)
Hırka Formation oil shales (~100 km NE of Ankara,
Turkiye) occured in Middle Miocene. Hırka Formation
become volcano-sedimentary stack that is generally
formed from claystone, oil shale, trona, mudstone,
intra-formation pebblestone, siltstone and pyroclastic
rocks. All this lithofacies developed to change
environment condition from consistently lake to playa
lake.
This formation has been studied by a combination of
organic geochemical methods (LECO/Rock-Eval) and
elemental analysis (ICP-MS) in order to assess the
hydrocarbon source potential of the abundant and
extensive shale intervals presents in the formation.
According to V / Cr, Ni / Co, V / (V + Ni) and V / Ni
ratios show that the organic matter of the source
rocks had been deposited in between oxic - disoxic
and anoxic conditions. Co/Ni and V/Ni ratios and
cross plots of the absolute values of V and Ni indicate
that these samples had significant terrestrial input.
Organic geochemical methods (LECO / Rock-Eval)
were used to determine oil- source rock potential of
oil-shales Total organic carbon (TOC) values (2.08
and 48.48 wt%) in oil shale samples indicates that it
has a very good-excellent source rock potential.
Furthermore the shales with hydrogen index (HI)
values (from 252 to 911; average 711) was found to
be generally excellent petroleum potential. Rock-Eval
(TOC,S1, S2, HI, OI and Tmax) and organic
petrography (amorphous/alga and inertinit) and
indicate that the shales are dominantly oil and gas
potential, containing Type 1 and II organic matter.
Thermal maturity, assessed from Tmax (Tmax value
between 381 and 447 °C), indicates that Middle
Miocene Hırka Formation range from diagenetic to
over mature with respect to oil generation and may
produce gas and oil.
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