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In an area spanning the margin of the Amadeus Basin and the crystalline basement rocks (the Arunta Complex) to the north , the effects of five deformational and metamorphic events are distinguished. Of these, the second (D2 ), third (D3 ), and fifth (D5) are major orogenic events of probable regional significance : they correspond respectively to isotopic dates of around 1600 m.y ., 1100 m.y . and 400 m.y. D 1 and D 4 are of local significance only.During D2 , rocks within the Arunta Complex, some of them of sedimentary origin, were metamorphosed to granulite facies in the extreme northern part of the area and to amphibolite facies in the southern part; the metamorphic grade was controlled by a probable greater depth of burial of the rocks to the north. A major deformed zone (the Redbank Zone) separates the two metamorphic regimes and was initiated during D2 . The Redbank Zone marks the site of a major thrust-fault zone with upthrow to the north , which can be traced within the Arunta Complex for at least 350 kms along strike. D2 deformation is most intense in the Redbank Zone , where it produces a north- dipping mylonitic foliation and north- plunging reclined intrafolial folds with strong axial mineral-orientation lineation; north and south of the Zone the intensity of D2 deformation becomes progressively less. Correlation of D2 structures south of the Redbank Zone is made difficult by the development of a D3 migmatite complex: the complex is the result of a rise in geothermal gradient in the area, coupled with, and perhaps caused by, metasomatism and granite intrusion. D2 and D3 took place prior to the deposition, in the Late Proterozoic and Palaeozoic, of the sediments of the Amadeus Basin. D5 is the Alice Springs Orogeny and affected both basement and cover. During D 5, uplift to the north took Place along reactivated, steep north- dipping faults within the Redbank Zone. These thrust faults penetrated the Heavitree Quartzite - the basal unit of the Basin sequence - to drive a wedge of basement with an attached veneer of Heavitree Quartzite (the Razorback Nappe) for at least 20 kms southward into the overlying shales and dolomites of the Bitter Springs Formation . Sediments above the Bitter Springs Formation were tilted into a vertical attitude but were not overridden by the Nappe . Subsequently D5 stresses within the Arunta Complex were relieved by lesser movements to form a fold-thrust complex underlying the Razorback Nappe . A marked linear break in outcrop within the Arunta Complex and an intense gravity gradient , which are the major present-day features of the Redbank Zone, probably largely result from Alice Springs Orogeny Movements.D5 deformation is restricted to the vicinity of major faults . Within the fold-thrust complex, a deformed zone up to 1 km wide , defined by a north- dipping mylonitic foliation and by isoclinal folds with west-trending, horizontal axes, is developed in the Heavitree Quartzite south of the Ormiston Thrust.