The Orca Basin is a mid-slope, silled, mini-basin in the northern Gulf of Mexico some 300 km southwest of the Mississippi River mouth on the Louisiana continental slope. It is unique amongst the mini-basins in this area, in containing a large brine pool of anoxic salt brine. The lake is approximately 123 km² (47 sq mi) in area and up to 220 m (720 ft) deep under 2,400 m (7,900 ft) depth of Gulf water and is derived from dissolution of underlying Jurassic age Louann Salt. With a volume of 13.3 km³ (3.2 cu mi) the pool results from the dissolution of about 3.62 billion tonnes of the Louann Salt bed into seawater.