Source rock characteristics and biostratigraphy of the Lower Silurian (Telychian) organic-rich shales at Akyaka, central Taurus region, Turkey

• Published in: Marine and petroleum geology Vol. 23; no. 9; pp. 901 - 911
• Main Authors: Varol, Ö.N., Demirel, I.H., Rickards, R.B., Günay, Y.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2006; Elsevier Science
• Subjects: Central Taurus; Earth sciences; Earth, ocean, space; Exact sciences and technology; Graptolite biostratigraphy; Graptolite reflection measurements; Graptolithina; Hydrocarbons; Marine; Marine geology; Sedimentary rocks; Source rock; Telychian hot shales; Middle East; Turkey; Central Taurus; Graptolite reflection measurements; Telychian hot shales; Graptolite biostratigraphy; Source rock; Mesozoic; Paleogene; Silurian; Chordata; hydrogen; Rock-Eval; pyrolysis; burial; upper Eocene; kerogen; graptolites; Lower Silurian; Cenozoic; Protochordata; oxygen; organic carbon; clastic rocks; black shale; overburden; thermal maturity; geologic sections; maturity; reflectance; Tertiary; upper Mesozoic; Hemichordata; source rocks; Eocene; Paleozoic; sedimentary rocks; Asia; upper Paleozoic; Graptolithina; organic materials; Phanerozoic; biostratigraphy
• ISSN: 0264-8172; 1873-4073
• DOI: 10.1016/j.marpetgeo.2006.07.003

The Akyaka section in the central Taurus region in the southern part of Turkey includes the organic matter and graptolite-rich black shales which were deposited under dysoxic to anoxic marine conditions in the Early Silurian. A biostratigraphical analysis, based on graptolite assemblages, indicates that the sediments studied may well be referable to the querichi Biozone and early Telychian, Llandovery. A total of 15 samples have been subjected to Leco and Rock-Eval pyrolysis and graptolite reflectance measurements for determination of their source rock characteristics and thermal maturity. The total organic carbon content of the graptolite-bearing shales varies from 1.75 to 3.52 wt% with an average value of 2.86 wt%. The present Rock-Eval pyrolytic yields and calculated values of hydrogen and oxygen indexes imply that the recent organic matter type is inert kerogen. The measured maximum graptolite reflectance ( G Rmax %) values are between 5.04% and 6.75% corresponding to thermally over maturity. This high maturity suggests a deep burial of the Lower Silurian sediments resulting from overburden rocks of Upper Paleozoic to Mesozoic Upper Cretaceous and Middle-Upper Eocene thrusts occurred in the region.