GY 402: Sedimentary PetrologyGY 402: Sedimentary PetrologyLecture 14:Lecture 14:Immature Siliciclastic Sedimentary EnvironmentsImmature Siliciclastic Sedimentary EnvironmentsAlluvial Fans, Braided StreamsAlluvial Fans, Braided StreamsUNIVERSITY OF SOUTH ALABAMAUNIVERSITY OF SOUTH ALABAMALast TimeLast Time1.1.Immature siliciclastic sedimentImmature siliciclastic sediment2.2.Immature siliciclastic sedimentary rocksImmature siliciclastic sedimentary rocks3.3.Point counting Point counting (for this or the next lab assignment)(for this or the next lab assignment)Immature siliciclastic sediment and sedimentary rocksImmature siliciclastic sediment and sedimentary rocksQQFFRRSource: Source: BlattBlatt, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary R, H., Middleton, G and Murray, R., 1980: Origin of Sedimentary Rocks. Prentice Hill, 782 p.ocks. Prentice Hill, 782 p.““ImmatureImmature””rocksrocks(mineralogically unstable)(mineralogically unstable)Enriched in feldspars and Enriched in feldspars and unstable rock fragmentsunstable rock fragmentsSiliciclastic Sedimentary RocksSiliciclastic Sedimentary RocksImportant Grain ParametersImportant Grain ParametersGrain SizeGrain Size(energy of deposition)(energy of deposition)RoundingRounding(degree of wear)(degree of wear)SortingSorting(energy of deposition)(energy of deposition)Immature Siliciclastic SedimentImmature Siliciclastic SedimentIs usually more diverse Is usually more diverse (mineralogy(mineralogy--wise) than wise) than mature sediment. mature sediment. Grains include:Grains include:XNXN250 250 µµmmPlagioclase feldsparPlagioclase feldsparOrthoclase Orthoclase MicroclineMicroclineMicasMicasLithicsLithicsQuartzQuartzLithic FragmentsLithic FragmentsLithic FragmentsLithic FragmentsHand specimensHand specimensImatureImaturesiliciclastic sandstonessiliciclastic sandstones((arkosearkose--litharenite)litharenite)5 cm5 cmArkoseArkose(basalt(basalt--derived)derived)Litharenite (igneous/sedimentaryLitharenite (igneous/sedimentary--derived)derived)ArkoseArkose(granite(granite--derived)derived)pplpplxnxn750 750 mmArkoseArkoseplagioclaseplagioclaseThinThin--section Photomicrographssection PhotomicrographsTodayToday’’s Agendas AgendaImmature siliciclastic sediment and sedimentary rocksImmature siliciclastic sediment and sedimentary rocksPictorial overview Pictorial overview Alluvial fansAlluvial fansBraided riversBraided riversAlluvial FansAlluvial Fans1 km1 kmAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansFan headFan headmid fanmid fanFan toeFan toeAlluvialplainAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansgradientwindAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial FansAlluvial Fans Alluvial Fans --view from the topview from the topAlluvial FansAlluvial FansFanFan--shaped deposits shaped deposits of siliciclastic of siliciclastic sediment deposited sediment deposited at the base of at the base of mountainsmountainsGravel to clay sizedGravel to clay sizedAngular to sub roundedAngular to sub roundedimmatureimmatureBest developed in arid regionsBest developed in arid regionsAlluvial FansAlluvial FansBest developed in arid regionsBest developed in arid regionsBest developed in tectonically active areasBest developed in tectonically active areasFrom Walker, R.G. 1980. Facies Models. From Walker, R.G. 1980. Facies Models. Geological Association of CanadaGeological Association of CanadaAlluvial FansAlluvial FansBest developed in arid regionsBest developed in arid regionsBest developed in tectonically active areasBest developed in tectonically active areasFrom Walker, R.G. 1980. Facies Models. From Walker, R.G. 1980. Facies Models. Geological Association of CanadaGeological Association of CanadaLateral finingLateral finingAlluvial FansAlluvial FansBest developed in arid regionsBest developed in arid regionsBest developed in tectonically active areasBest developed in tectonically active areasFormed primarily through the action of water flow, Formed primarily through the action of water flow, but there are also mass flow depositsbut there are also mass flow depositsAlluvial FansAlluvial FansBest developed in arid regionsBest developed in arid regionsBest developed in tectonically active areasBest developed in tectonically active areasFormed primarily through the action of water flow, Formed primarily through the action of water flow, but there are also mass flow depositsbut there are also mass flow depositsDebris flows, fluidized flow and Debris flows, fluidized flow and ““sievesieve””depositsdepositsAlluvial FansAlluvial FansChalk BoardChalk BoardWalker, R.G. and James, N.P., 1992. Facies Models. Response to SWalker, R.G. and James, N.P., 1992. Facies Models. Response to Sea ea Level Change.Level Change.Geological Association of Canada, Geological Association of Canada, 409p.409p.Alluvial Fan FaciesAlluvial Fan FaciesgravelgravelWalker, R.G. and James, N.P., 1992. Facies Models. Response to SWalker, R.G. and James, N.P., 1992. Facies Models. Response to Sea ea Level Change.Level Change.Geological Association of Canada, Geological Association of Canada, 409p.409p.Alluvial Fan FaciesAlluvial Fan FaciessandsandWalker, R.G. and James, N.P., 1992. Facies Models. Response to SWalker, R.G. and James, N.P., 1992. Facies Models. Response to Sea ea Level Change.Level Change.Geological Association of Canada, Geological Association of Canada, 409p.409p.Alluvial Fan FaciesAlluvial Fan Facies““mudmud””Walker, R.G. and James, N.P., 1992. Facies Models. Response to SWalker, R.G. and James, N.P., 1992. Facies Models. Response to Sea ea Level Change.Level Change.Geological Association of Canada, Geological Association of Canada, 409p.409p.Alluvial Fan FaciesAlluvial Fan FaciesWalker, R.G. and James, N.P., 1992. Facies Models. Response to SWalker, R.G. and James, N.P., 1992. Facies Models. Response to Sea ea Level Change.Level Change.Geological Association of Canada, Geological Association of Canada, 409p.409p.Alluvial Fan FaciesAlluvial Fan FaciesDebris Debris flowsflowsWalker, R.G. and James, N.P., 1992. Facies Models. Response to SWalker, R.G. and James, N.P., 1992. Facies Models. Response to Sea ea Level