Chitinozoan biostratigraphy - a good correlation tool for Ordovician rocks: Case study of baltoscandian oil shale interval
- Institute of Geology, Tallinn (Estonia)
- Univ. of North Carolina, Chapel Hill, NC (United States)
Chitinozoans are organic-walled microfossils known from marine sedimentary rocks of Ordovician to Devonian age. In Baltoscandia, chitinozoans have been extensively studied since the 1930s and chitinozoan biostratigraphy of Ordovician-Silurian succession is quite well established. Because the Ordovician-Silurian carbonate sequence contains only a scarce graptolite fauna, chitinozoans and conodonts are considered the most valuable faunal groups for stratigraphic correlation, with the chitinozoans offering even better temporal resolution due to their widespread occurrence, planktonic origin, and relatively easy taxonomy. Also, small samples (100-300 g) can yield several hundreds of chitinozoans. In this study, chitinozoan distribution is compared in two Middle Ordovician (Llanvirn to Caradoc) core sections: Tamsalu-565 (central Estonia) and Bliudziai-150 (southern Lithuania). The distance between studied sections is about 470 km. The studied intervals are 51 and 27 m thick in the Tamsalu-565 and Bliudziai-150 cores, respectively. Both sections are highly condensed with numerous hardgrounds, but without major hiatuses. The Tamsalu-565 borehole was drilled in the Tapa oil shale deposits and contains 17 kukersite-type oil shale beds up to 2.3 m thick. Both sections yielded a numerous and diverse chitinozoan fauna. Altogether, 14 genera and 55 species were recorded. Although many chitinozoan species are long ranging, several with limited vertical range are useful biostratigraphically and suggest a good correlation between the studied sections. Chitinozoans can be regarded as a perspective faunal group in the United States for correlating subtidal to basin carbonate sediments, particularly when small sample size is a critical factor.
- OSTI ID:
- 6679088
- Report Number(s):
- CONF-930981-; CODEN: AABUD2
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 77:8; Conference: Eastern Section meeting of the American Association of Petroleum Geologists: eastern energy, environment and education for the 21st century, Williamsburg, VA (United States), 19-21 Sep 1993; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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