Discussion Paper - Part A - Victorian Environmental Assessment ...

Table 2.2 Structural zones identified within Victoria.Structural zonesDelamerian Fold BeltRock typesMain deformationepisodesGlenelg ZoneDeep-marine sedimentary rocks and very minor basaltof Proterozoic to Early Cambrian age. Deformation andheating converted some of the rocks into schist andgneiss, and granitic rocks. Rocks are mostly buriedbeneath younger sequences.Delamerian OrogenyGrampians-Stavely ZoneCambrian age volcanics and sedimentary rocks of theGlenthompson Sandstone. Minor occurrences ofserpentinite and ultramafic rocks occur in thin slivers,and have been intersected in drill holes at depth (e.g.Dimboola Igneous Complex).Delamerian OrogenyLachlan Fold BeltStawell ZoneDeep-marine sedimentary rocks and minor basalt ofEarly Cambrian age overlain by extensive Cambro-Ordovician quartz-rich turbidites (Cambrian St Arnaud/Early to middle Ordovician Castlemaine Group)Delamerian OrogenyBendigo ZoneThree main sequences: deep-marine sedimentary rocksand minor basalt of Cambrian to Ordovician agecomprising Ordovician turbidites (Castlemaine Group);Upper Cambrian shales and cherts; mid to lowerCambrian volcanics and volcanoclasticsBenambran OrogenyMelbourne ZoneDeep to shallow marine sedimentary rocks of EarlyOrdovician to Early Devonian ageTabberabberan OrogenyTabberabbera ZoneDeep-marine sedimentary rocks and minor basalt ofCambrian to Ordovician ageBenambran OrogenyOmeo ZoneDeep-marine sedimentary rocks and minor basalt ofCambrian to Ordovician age, deformed at relativelydeeper level so that much of the rock has undergonehigh-grade metamorphism to schist and gneiss, andmelting to migmatite and granite.Benambran OrogenSource: VandenBerg et al. (2000)The major events in Victoria’s geological history occurredin three eras. Rocks from the earliest or Palaeozoic era(542–251 million years ago) form the basementunderlying the entire study area, but few outcrops occur(see Map 2.1). Mesozoic era (251–65 Ma) rocks are onlyfound at depth within depositional troughs of theMurray Basin (Figure 2.3) and near the eastern part ofthe study area in the King River valley. Most surfacegeology is from the extensive Cainzoic era (65–0 Ma)sediments of the riverine plain.PalaeozoicThe Lachlan Fold Belt (Figure 2.2) comprises mostPalaeozoic age rocks in Victoria, specifically from theCambrian until the Carboniferous. Each structural zonewithin this sequence has experienced a uniquegeological history including periods of orogenicmountain building, sediment deposition and graniteintrusion, leading to the diverse character of landscapeacross Victoria today, described in Table 2.2.Discussion Paper9