LITHOSTRATIGRAPHY OF NIGERIA AN-OVERVIEW

摘要

Nigeria lies very close to the equator (hot country) West coast Africa between latitude 4 N and 14 N degree and longitude 2 E and 15 E degree. The country is located at the Northern end of Eastern branch of west coast of Africa rift system. Nigeria geological set up comprises broadly sedimentary formation and crystalline basement complex, which occur more or less in equal proportion all over the country. The sediment is mainly Upper Cretaceous to recent in age while the basement complex rocks are thought to be Precambrian. The studied area lies between latitude 12.4" and 11.11"W and longitude 13.81" and 14.13" S. The studied area is underlain by Precambrian basement complex of southern western Nigeria .The major rock in the area is charnokite and granite rock. The granite rock which are member of the older granite suite occupy about 65% of the total area .The principal granite is petrographic variety are recognized .The fine grained biotite-granite medium-coarse, non porphyritic biotite -hornblende granite and coarse-porphyritic biotite -hornblende granite. Also three main textural type of Charnokitic rock are also distinguished are coarse grained, massive fine grained and gneissic fine grained .The mode of occurrence of rock is three (1) core of the granite rock as exemplified by study area and few smaller bodies (2) Margin of the granite bodies as seen in Ijare and Uro edemo-idemo Charnokitic bodies and (3) Discrete bodies of the gneissic fine grained Charnokitic rock within the country gneisses as seen in Ilaro and Iju and Emirin village. All the charnokite in the region are dark-greenish to greenish-gray rocks with bluish quartz and greenish feldspar.