PHYSICAL SETTING

Posted by on 1/29/2003 1:09:56 PM
Post Comment PHYSICAL SETTING Nigeria

Cross River State, the nation's remaining rain forest and wildlife sanctuary, is physically a micro cosm of Nigeria. Except the Sahel, all the other ecological zones in Nigeria are represented in this state.

Remembrance Arcade,Calabar
Remembrance Arcade,Calabar

Located on Nigeria's southeastern frontier, the Cross River landscape descends precipitously from the ObanObudu rugged foothills (1000 2000m) of the Cameroun Mountains on the east, into the Cross River Plains (30m) to the west, and down to the Bight of Bonny coastal plains to the south, Coastal mangrove wetlands interlaced with creeks, virgin rainforest on the ObanObudu hills, montane parkland on the Obudu Plateau, and derived Savannah on the Cross River Plain, are all parts of the Cross River State vegetation and scenery.

From its name, it is apparent that Cross River State occupies the catchment of the Cross River, which courses down the Cameroun Mountain, across the flatlying Cross River Basin, into a vast estuary located along the southern Nigeria Cameroun border.

Geologically, the Cross River estuary is actually a delta of its own, totally inde pendent of the Niger Delta, but merely coterminous with it (Petters, 1991).

The Cross River Delta is a major petroleum producing area which includes the Rio Del Rey Basin in Cameroun. Because of its geographical location and enormous geologic potentials, Cross River State is crucial to the strate gic interests of Nigeria. Bakassi Peninsular, a dis puted territory between Nigeria and Cameroun is part of Cross River State physically and culturally since colonial days.

The state spans a total area of 21,481 sq. km, which is equally divided into basement and sedi mentary basins. The Basement Complex, which forms the ObanObudu hills, consists of Precambrian schists and gneisses, with intrusives of igneous rocks such as granodiorite, diorite, gab bro and dolerite ((Ekwueme, 1986).

The sedimen tary basins, of Cretaceous Tertiary age, are found in the Ikorn Depression (Mamfe Rift), the Cross River Plain, and the Calabar Flank. Structurally, the Cross River Plain is underlain by the Ogoja syncline and the Abakaliki uplift wherein lie thick Cretaceous sandstones, marine shales and limestones of the Asu River Group and the Cross River Group.

The Ikorn depression is filled with over 3km of Cretaceous sandstones and mudstones and Tertiary basalts. Along the Calabar Flank is a thick sequence of shales and the karstic carbonates of the Mfamosing Limestone, with caves.

Calabar Cenotaph
Calabar Cenotaph

Unconformably, on the Cretaceous of the Calabar Odukpani Flank, is the thick Tertiary sequence of the Cross River Delta which has built out onto the continental shelf where deep submarine canyons (e.g. the Calabar Canyon) have been incised, with deepsea fans building out onto the ocean floor and providing excellent petroleum traps.

The Cross River, with a catchment area of 53,590 sq. km, delivers more sediment load to the coast, than the present Niger Benue drainage system. The Niger delta shoreline is therefore undergoing erosion on account of sedi ment starvation. The strength of the Cross River deltaic sedimentation derives from the Cameroun Mountain which is the most active sediment source area along the West African coast.

Cross River soils are predominantly of five types. These are: (i) the steep, shallow, yellowish and red gravely soils on the ObanObudu Hills; (ii) the deep lateritic, fertile soils on the Cross River Plain; (iii) the dark clayey basaltic soils in Ikorn; (iv) the sandy, heavily leached soils on the older coastal plain which are highly susceptible to gully erosion; and (v) the swampy hydromorphic soils of the lower deltaic coastal plain that is usually floated during the rains.

Humid tropical climate (1300 3000mm rain fall; 30C mean annual temperatures) prevail over Cross River State, except on the Obudu Plateau, where the climate is subtemperate, with tempera tures of 15C 23C.

The vegetation ranges from mangrove swamps, through rainforest, to derived savannah, and montane parkland. Just as its rocks are diverse, so also are the mineral resource potentials of the State.

In the Basement Complex, mineralisation includes tin and gold (mined in colonial days from Akwa lbami and Akamkpa), ilmenite, columbitetantalite, kaolin, graphite, manganese and marble; while in the sed imentary basins are high quality limestones, salts, barytes, leadzinc, and uranium prospects.




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