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Vol.4 , No. 2, Publication Date: Aug. 8, 2017, Page: 8-19
 interbeded with mudstones. Palynological analysis of shale samples from selected surface outcrops of the unit yielded 20 palynomorph taxa comprising pollen, spores, and marine dinoflagellate cysts. The presence of palynomorph species <i> Elaterosporites</i> sp., <i> Perotriletes pannuceus</i> and <i> Steevesipollenites giganteus</i> suggest the shales outcropping in Ohana, Apiapum, Ntamkpo and Abaomege areas were deposited during the late Cenomanian-early Turonian. The lower age limit of late Cenomanian in this study is based on occurrence of <i> Elaterosporites</i> sp. and absence of the Albian palynoflora. Middle - late Turonian is assigned to shale outcropping in Oyadama and Ediba using palynomorph species: <i> Ephedripites</i> cf. <i>multicostatus, Monocolpopollenites spheroidites</i> and <i> Proteacidites dehaanii</i>. Samples collected from Usumutong and Ediba showed a mixture of Campanian - Maastrichtian palynoflora and Turonian palynomorphs and absence of the Coniacian - Santonian index pollen <i> Droseridites senonicus</i>. This supports absence of the Coniacian Awgu Formation in the eastern flank of Abakaliki Anticlinorium and overstepping of the Campano - Maastrichtian Nkporo Group onto the Eze-Aku units in the basin. The paleoenvironment has been interpreted as shallow, open marine to a slightly deeper water setting dominated by influence of waning flows typical of storm wave or turbidity current.&picture=http://www.aascit.org/aascit/decorators/img/journal/924.jpg)
| [1] | Ezekiel Obinna Igwe, Department of Geology, Ebonyi State University, Abakaliki, Nigeria. |
The Eze-Aku Shale represents the extensive basal unit of the Eze-Aku Group in the eastern flank of the Abakaliki Anticlinorium, southeastern Nigeria. The shale unit comprises of flaggy, dark-grey to black calcareous shales rich in pelagic faunas (pelecypods and gastropods) interbeded with mudstones. Palynological analysis of shale samples from selected surface outcrops of the unit yielded 20 palynomorph taxa comprising pollen, spores, and marine dinoflagellate cysts. The presence of palynomorph species Elaterosporites sp., Perotriletes pannuceus and Steevesipollenites giganteus suggest the shales outcropping in Ohana, Apiapum, Ntamkpo and Abaomege areas were deposited during the late Cenomanian-early Turonian. The lower age limit of late Cenomanian in this study is based on occurrence of Elaterosporites sp. and absence of the Albian palynoflora. Middle - late Turonian is assigned to shale outcropping in Oyadama and Ediba using palynomorph species: Ephedripites cf. multicostatus, Monocolpopollenites spheroidites and Proteacidites dehaanii. Samples collected from Usumutong and Ediba showed a mixture of Campanian - Maastrichtian palynoflora and Turonian palynomorphs and absence of the Coniacian - Santonian index pollen Droseridites senonicus. This supports absence of the Coniacian Awgu Formation in the eastern flank of Abakaliki Anticlinorium and overstepping of the Campano - Maastrichtian Nkporo Group onto the Eze-Aku units in the basin. The paleoenvironment has been interpreted as shallow, open marine to a slightly deeper water setting dominated by influence of waning flows typical of storm wave or turbidity current.
Keywords
Eze-Aku Shale, Palynomorph Taxa, Palynological Analysis, Paleoenvironment
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