PETROGRAPHIC STUDY OF AMASIRI SANDSTONE IN OZARA UKWU AND ITS ENVIRONS, AFIKPO BASIN,NIGERIA
Petrographic analysis were carried out on sixteen samples obtained from Amasiri, Ozara Ukwu, Asaga- Amangwu, Iyioka and Macgregor college area of Afikpo, located in part of the Abakaliki in the Southern Benue Trough. The study area lies between latitudes 5050 N and 551N and longitude 705213011E and 70551E within the Abakaliki anticlinorium in the South Benue Trough, Nigeria. The samples represent the sedimentary infills in the South Benue Trough and are composed of quarter arenite, arkosic sandstone, siltstones, greywacke, ferruginized bioclastic sandstone, and shale. They form part of the formations of the Asu Rivers Group, Eze-Aku and Agwu shale deposited during cenomanian-Turonian-Santonian period and affected by Santonian orogeny and magnetism. The lithology had undergone progressive metamorphism based on the textural documentation of features in thin section. Petrographic analysis and photomicrograph indicate changes to hornfels of shale showing finely crystallized quartz, arkosic sandstone and siltstone with exsolved globules, rods and perthites, buchite of quartz arenite with elongate, lenticular and rounded grains aligned in preferred orientation, glass matrix, ferromagnesian minerals, the boundaries are not distinct but transit with margins of reaction rims and web texture.