|Institution:||University of Adelaide|
|Keywords:||Adelaide Geosyncline, Mt Lofty Fold Belt, South Australia; Honours; Geology; Adelaide Geosyncline; stratigraphy; petrology; mineralogy; metamorphism; faulting|
|Full text PDF:||http://hdl.handle.net/2440/84139|
In the area survey, the rock formations are mainly Adelaide Series rock which belong predominantly to the lower Adelaide System in age. Several major faults have been found in the area as well as a number of minor faults and belts of intense drag folding. A major fault extending from Williamstown to Rosedale is approximately parallel in strike with the regional cleavage. The vertical displacement is several thousand feet. Injection of pegmatites took place in the zones of intense faulting and folding and under the high temperatures prevailing talc was formed through metasomatic processes and accumulated in drag folds; clay and damourite were formed under hydrothermal conditions and an introduction of iron-ore in fault zones of the Mt. Kitchener area (this must not be confused with the Mount Bessemer iron ores). According to Sprigg, middle Tertiary Time was a period of faulting (Kosciusko Epoch) in which the present 'Horst' Range took place. The writer considers that the down faulting of the Tanunda Angaston Senkungsfeld corresponds to this period. The older rocks, although much covered by Tertiary sands, clays and gravel beds, and in places lateritized (see Diagram) to a white clay, which is evidence of much secular decay, shows evidences of much folding and served faulting and considerable thermal and metamorphic changes. From Barritt's Estate (north Para) a fault zone runs down to the foothills at Williamstown. This fault is probably of middle Cambrian age when pegmatites were injected into fracture zones during orogenic events. This injection of pegmatites was accompanied by wide spread hydrothermal alteration with development of talc, chrysotile, serpentine, sericitic mica. The marble horizon above the basal grits can be traced across the area occupied by Tertiary sands and gravels in the Lyndock area, mainly from bore results. Between Rosedale and Mr. Hermann Thunn's Winery, the limestones are deposed in the form of an anticlinal fold. The presence of quartzite beds have prevented intense faulting and folding of the less competent strata except in fault zones and these quartzite bands have been found a useful index to the regional dip. Mineralization does not generally occur on a commercial scale in the area surveyed. Copper ores occur at the Enterprise Copper mine and the Lord Lindock mine. However, these have been practically worked out. Rutile occurs as disseminations in damourite schists and clay occurs in important deposits at Williamstown. Gold has been found in many places in the Tertiary gravels.