eesti teaduste
akadeemia kirjastus
SINCE 1984
Oil Shale cover
Oil Shale
ISSN 1736-7492 (Electronic)
ISSN 0208-189X (Print)
Impact Factor (2020): 0.934


Full article in PDF format | doi: 10.3176/oil.2010.2.02


The oil shale deposit in the Abakaliki anticlinorium has not been demarcated. The present study focused on the age, correlation and depositional environ­ment of the oil shale using abundance, planktonic/benthonic ratio and species diversity of foraminiferal and ostracod assemblages. The result shows that three prominent peaks or biozones namely 1st, 2nd and 3rd were recognized. The 1st biozone showed that Praeglobotrucana and Guembelitria are the dominant species and ranged from Albian to Mid-Cenomanian (96–108 my). The 2nd biozone indicated that Hedbergella and Heterohelixare the dominant species, and ranged from Upper Cenomanian to Early Turonian (92–95 my). The 3rd biozone showed that Heterohelicids are the dominant species and ranged from Middle Turonian to Coniacian (82–91 my). The 1st, 2nd, and 3rd biozones correspond to the deposition of Asu River Group (Abakaliki Shale), Eze-Aku Formation and Awgu Formation respectively. The 2nd peak is bimodal and has the highest frequency and this supports the maximum transgression occurring at the Cenomanian-Turonian boundary event (ocean anoxic event). The oil shale is deposited in outer shelf to bathyal environment and ranged from Upper Cenomanian to Early Turonian age and belongs to the Eze-Aku Formation.

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