Summary Hydrocarbon exploration of the East African continental margin has not received the same level of focus as the Atlantic margin. However, since the giant gas discoveries off the coasts of Tanzania and Mozambique, it has been a hotspot of frontier deepwater exploration activity. From Mozambique to Somalia this gigantic continental passive margin basin has been under-explored despite the offshore success stories from the Rovuma, Mozambique and Tanzania basins. The large volumes of gas discovered have raised the question whether any liquid hydrocarbons have been trapped. The large amount of gas might have been generated from oil prone Jurassic or older source rocks. Recently an oil discovery was reported from the Lamu basin, offshore Kenya in 2014. This newly established liquid hydrocarbon play is being studied in detail. Future hydrocarbon exploration campaigns may expand towards the north-eastern Somali basin and into the ultra-deep water areas of the Madagascar channel beyond the Davie ridge, guided by the tectono-sedimentary evolution of the margin. Key risks to the development of such plays will include source rock maturity, related to the nature of the underlying crust and associated heat flow, and regional hydrocarbon migration pathways. This extended abstract intends to summarize key challenges and potential risks in the exploration for oil rather than gas in the East African continental margin basins.
The central part of Indian craton is believed to be a stable continental region with low strain build-up and long earthquake recurrence periods. It comprises two major Archean cratonic fragments (i.e. the Bundelkhand and the Bastar Cratons) and a Proterozoic mobile belt called Central Indian Tectonic Zone (CITZ), along which the cratonic fragments were amalgamated in the Proterozoic. Gavilgarh Fault Zone (GFZ) is an important component of CITZ and is represented by a >250 km long, ENE-WSW trending fault line which demarcates the southern boundary of the Satpura mountains. Although the eastern part of the lineament shows evidences of polyphase tectonic movements in the Meso-Neoproterozic (Chattopadhyay and Khasdeo, 2011), there is no focussed analysis of neotectonic activity in this fault zone although a number of earthquakes have been recorded within the CITZ in last 100 years or so. The present study comprises structural mapping and geomorphological analysis of a 200 km long stretch of the GFZ lineament. GFZ shows evidences of reverse fault-slip movements that possibly resulted in an uplift of the northern side, as deeper level rocks (e.g. Paleozoic Gondwana sandstones) are juxtaposed against the overlying Deccan Trap basalts of Mesozoic age along the fault line. Crushing of basalts along the lineament, asymmetric folds within Gondwana sandstone, inclination of Anisotropic Magnetic Susceptibility (AMS) axes etc. provide evidences for fault-drag folding related to the post-Deccan reverse faulting. Drainages crosscutting the lineament adjusted with the tectonic uplift either by incising their own sediments and bed rock or by increasing their sinuosity, only in the northern side, as seen in the satellite images. Hypsometric Integral values suggest that the immature/in-equilibrated drainage basins were restricted in the north while mature/equilibrated basins developed in the south of the lineament. Longitudinal profiles and S-L Index of the river profiles, prepared from DEM, clearly mark the knick ponits related to the faulting. Ages of terrace sediment samples obtained by luminescence dating method (OSL/IRSL) and ages calculated from knick point migration rate (following Loget and Van den Driessche, 2009) suggest that reverse slip movement along GFZ started possibly at c. 93ka and the fault reactivated again at c. 41 ka and further after c. 12 ka. This neotectonic movement may be a result of the reported regional shortening of 2±1 mm/yr across the CITZ obtained from geodetic GPS measurement (Banerjee et al., 2008).
'%3e%3ccircle r='20' fill='%23008'/%3e%3ccircle r='17.5' fill='%23fff'/%3e%3ccircle r='3.5' fill='%23008'/%3e%3cg id='d'%3e%3cg id='c'%3e%3cg id='b'%3e%3cg id='a' fill='%23008'%3e%3ccircle r='.875' transform='rotate(7.5 -8.75 133.5)'/%3e%3cpath d='M0 17.5.6 7 0 2l-.6 5L0 17.5z'/%3e%3c/g%3e%3cuse xlink:href='%23a' transform='rotate(15)'/%3e%3c/g%3e%3cuse xlink:href='%23b' transform='rotate(30)'/%3e%3c/g%3e%3cuse xlink:href='%23c' transform='rotate(60)'/%3e%3c/g%3e%3cuse xlink:href='%23d' transform='rotate(120)'/%3e%3cuse xlink:href='%23d' transform='rotate(-120)'/%3e%3c/g%3e%3c/svg%3e)
