The gravity field and gravity data reduction across the continental area of Nigeria  

作　　者：Oluwatimilehin B.Balogun Isaac B.Osazuwa 

机构地区：[1]Department of Geosciences,Mountain Top University,Prayer City,Ogun State,Nigeria [2]Department of Geophysics,Federal University,Oye-Ekiti,Ekiti State,Nigeria

出　　处：《Geodesy and Geodynamics》2023年第3期304-320,共17页大地测量与地球动力学（英文版）

摘　　要：This research presents the variation of the gravity field and associated gravity field components over the continental area of Nigeria to provide data for geoscience research,geodetic and engineering works,aerodynamic studies and deep crustal inferences.Accurate positions and elevations were observed at 58 of the 59 base stations of the Primary Gravity Network of Nigeria(PGNN),whose absolute gravity values had been accurately determined.The absolute gravity values were plotted against their respective positions to reveal the distribution pattern and strength of the gravity field within the study area.Theoretical gravity values at each base station were generated using the Somigliana's equation.The free-air gravity and free-air anomaly gravity values were generated with respect to the World Geodetic System 1984(WGS84)ellipsoid using GPS-derived elevation data.Then,the perturbing potential,free-air gravity with respect to the geoid,and the indirect effects were evaluated.The average of the indirect effects was used to adjust the WGS84 gravity formula to produce a gravity formula that better approximates the geoid across the continental area of Nigeria,compatible with the heights measured relative to the geoid,which can serve as a reference for establishing a vertical height control.The Bouguer gravity and Bouguer gravity anomalies across Nigeria revealed a“trans-southern gravity high strip”interpreted to be associated with mantle upwelling.Two new major mega-lineaments related to mantle upwelling were mapped.A batholith province trending NWeSE was delineated,occurring from north central Nigeria to the north western region and containing closures of“Bouguer gravity lows”interpreted as batholiths.A separate closure of“Bouguer gravity low”was detected at Azare,north eastern Nigeria,which may be due to the presence of intrusive granitic body.It is recommended that the mantle structure beneath“the trans-southern gravity high strip”,“delineated batholith province”and“isolated gravity closures”arou

关 键 词：Absolute gravity Continental Nigeria landmass Primary gravity network of Nigeria(PGNN) WGS84 ellipsoid Indirect effect Height datum 

分 类 号：P223[天文地球—大地测量学与测量工程]