The gravity and magnetic data along the profile across the southern part of the Cauvery basin have been collected and the data is interpreted for crustal structure depths.The first profile is taken from Karikudito Embalecovering a distance of 50 km. The gravity lows and highs have clearly indicated various sub-basins and ridges. The density logs from ONGC, Chennai, show that the density contrast decreases with depth in the sedimentary basin, and hence, the gravity profiles are interpreted using variable density contrast with depth. From the Bouguer gravity anomaly, the residual anomaly is constructed by graphical method correlating with well data and subsurface geology. The residual anomaly profiles are interpreted using polygon and prismatic models. The maximum depths to the granitic gneiss basement are obtained as 3.00 km. The regional anomaly is interpreted as Moho rise towards coast. The aeromagnetic anomaly profiles are also interpreted for charnockite basement below the granitic gneiss group of rocks using prismatic model.