Geosciences Research

6

Authors: Neloy Khare

Twenty one surface sediment samples (comprising Peterson Grab, Piston, Gravity and Spade core top samples) were collected along a north-south transect (between 9.69°N and 55.01°S latitude and 80°E and 40°E longitude). These samples were used to study δ13C values in the calcareous shells of planktic foraminiferal species Globigerina bulloides and the variations were compared with the latitudinal changes in the overall size of the planktic foraminiferal population obtained from earlier published data along similar transect. The results establish an interdependence of δ13C values of planktic species Globigerina bulloides and the overall size of planktic foraminiferal population. The region where the δ13C values of planktic species Globigerina bulloides decrease the overall size of planktic foraminiferal population increases. Such a distinct pattern may be ascribed to the generation of food/nutritive material. It is suggested that similar studies to understand variations in δ13C values in foraminiferal shells and its population size in geographically distinct latitudinal corridors covering distinct marine regime of physico-chemical conditions be undertaken to further strengthen the argument proposed in the present study.

10

Authors: A.A Oghuma, I.I. Obiadi, C.M Obiadi, C.N. Nwokeabia

Evaluation and structural interpretation of aeromagnetic anomalies over parts of Monguno and environs, northeastern Nigeria was carried out using 3-D Euler deconvolution to determine the presence, distribution and depth of intrusives in the area. Analysis of maps and images provided the basis for qualitative as well as quantitative interpretations of the aeromagnetic data so as to obtain information on the presence, depth and distribution of intrusives in the area. Results from the 3-D Euler deconvolution of the aeromagnetic data showed predominantly geologic sources of magnetic anomalies for horizontal cylinder and pipe, spheres, sills and dykes, in order of decreasing magnitude, having structural indices (SI) of 2, 3 and 1 respectively. To a lesser degree are sources of magnetic anomalies for contact, having SI of 0, which may be interpreted to be deep seated faults, which have significantly affected the basement rocks surface configuration. The average depth to which magnetic intrusions occur within the sedimentary formations across all SI is less than 500m. Mineralization may be prevalent in the study area as indicated by the presence of these intrusives, some of which occur at favourable depths that allow for economic extraction.