<P> Deformation of the lithosphere in the plane of the earth (i.e. such that faults are vertical) occurs as a result of near horizontal maximum and minimum principal stresses . The resulting zones of subsidence are known as strike - slip or pull - apart basins . Basins formed through strike - slip action occur where a vertical fault plane curves . When the curve in the fault plane moves apart, a region of transtension results, creating a basin . Another term for a transtensional basin is a rhombochasm . A classic rhombochasm is illustrated by the Dead Sea rift, where northward movement of the Arabian Plate relative to the Anatolian Plate has caused a rhombochasm . </P> <P> The opposite effect is that of transpression, where converging movement of a curved fault plane causes collision of the opposing sides of the fault . An example is the San Bernardino Mountains north of Los Angeles, which result from convergence along a curve in the San Andreas fault system . The Northridge earthquake was caused by vertical movement along local thrust and reverse faults bunching up against the bend in the otherwise strike - slip fault environment . In Nigeria, the dominant type of basement rock intersected by wells drilled for hydrocarbons, limestone, or water is granite . The three sedimentary basins in Nigeria are underlain by continental crust except in the Niger delta, where the basement rock is interpreted to be oceanic crust . Most of the wells that penetrated the basement are in the Eastern Dahomey embayment of western Nigeria . A maximum thickness of about 12,000 m of sedimentary rocks is attained in the offshore western Niger delta, but maximum thicknesses of sedimentary rocks are about 2,000 m in the Chad basin and only 500 m in the Sokoto embayment . </P> <P> As more and more sediment is deposited into the basin, the weight of all the newer sediment may cause the basin to subside further because of isostasy . A basin can continue having sediment deposited into it, and continue to subside, for long periods of geological time; this can result in basins many kilometres in thickness . Geologic faults can often occur around the edge of, and within, the basin, as a result of the ongoing slippage and subsidence . </P> <P> The study of sedimentary basins as a specific entity in themselves is often referred to as basin modelling or sedimentary basin analysis . The need to understand the processes of basin formation and evolution are not restricted to the purely academic . Indeed, sedimentary basins are the location for almost all of the world's hydrocarbon reserves and as such are the focus of intense commercial interest . </P>

Ocean basins in the formation of sedimentary rocks