A Simplified Geology of the Perth Metropolitan Area
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A Simplified Geology of the Perth Metropolitan Area Fred Verheyde Geotechnical Principal / Branch Manager WA Geological Setting Present d Perth 4.6 Ga: Birth of the Earth WA Geological Setting Present d Pilbara Craton Y Yilgarn P Craton Perth 4.6 Ga: Birth of the Earth WA Geological Setting Present d North Australian Craton WA Pilbara Craton NA Y Yilgarn P Craton Perth 4.6 Ga: Birth of the Earth WA Geological Setting Present d NUNA Nuna North Australian Craton WA Pilbara Craton NA Y Yilgarn P Craton Perth 4.6 Ga: Birth of the Earth WA Geological Setting Present d NUNA Nuna North Australian Craton WA Pilbara Craton SA NA Y Yilgarn South Australian Craton P Craton Perth 4.6 Ga: Birth of the Earth WA Geological Setting Present d Gondwana Aus RHODINIA Rhodinia Nuna North Australian Craton WA Pilbara Craton SA NA Y Yilgarn South Australian Craton P Craton Perth 4.6 Ga: Birth of the Earth WA Geological Setting Present d Gondwana GONDWANA Aus Rhodinia Nuna North Australian Craton WA Pilbara Craton SA NA Y Yilgarn South Australian Craton P Craton Perth 4.6 Ga: Birth of the Earth WA Geological Setting Present d Gondwana Aus Rhodinia Nuna North Australian Craton WA Pilbara Craton SA NA Y Darling Fault Yilgarn South Australian Craton P Exotic crust Exotic Craton Perth 4.6 Ga: Birth of the Earth WA Geological Setting Present h d Aus Pilbara North Australian Craton WA SA NA Y Darling Fault Yilgarn. P South Australian Craton Pinjarra Orogen Pinjarra A A' Perth 4.6 Ga: Birth of the Earth Deep Geology in the Perth Area A A' tnest Is. Rot Perth Darling Scarp Darling Range 300 m A 60 m A' Earth Surface -30 m Ocean Perth Basin Oceanic -12 km crust Yilgarn craton Exotic crust A A' Magma -30 km Magma Landform Darling Range (Granitic rock of Yilgarn Craton) Darling Scarp (Darling Fault) Gingin Scarp: Former foreshore Coastal Plain: Pinjarra Plain (Guildford Formation) Bassendean Dune System (Bassendean Sand) Spearwood Dune System (Tamala Limestone and sand) Quindalup Dune System (Safety Bay Sand) A' A Perth Ocean Perth Basin Oceanic crust Yilgarn craton Exotic crust Magma Geology / Landform Surface Geology Landform A A' Perth Superficial Geological Formations A' A Perth Ocean A A' Perth Basin Oceanic crust Yilgarn craton Exotic crust Magma from upper mantle Tamala A' Safety Bassendean Yoganup Limestone Bay Sand Sand Sand and sand Guildford Spearwood Dunes Bassendean Dunes Formation Perth A Quindalup Dunes Pinjarra Plain 0 m ocean Yilgarn Craton -30 m Perth Basin Chronology of the Local Geology Present 5 h d M yrs Young Old Aus 1 000 M yrs WA Safety Tamala Bassendean Guildford Yoganup Bay Limestone Sand Formation Sand Sand and sand 200 10 000 100 000 180 000 2 500 000 Y 3 000 - - - - - M yrs 6500 420 000 800 000 1 800 000 5 000 000 ? yrs ? P Perth Yilgarn ocean 0 m Craton 4.6 Ga: Birth of the -30 m Perth Basin 3 000 000 000 yrs Earth 65 000 000 - 300 000 000 yrs Safety Bay Sand Quindalup Dune System Safety Bay limestone Tamala Limestone and Sand Quindalup Dune System Sand derived from Tamala Limestone Tamala Limestone Perth CBD Ocean Safety Bay Sand Bassendean Dunes Sand from Tamala Limestone Tamala Limestone Tamala limestone Bassendean Sand Bassendean Sand Sand derived from Tamala Limestone Bassendean Sand Coffee rock Guildford Formation Yilgarn craton / Darling Range 1,000,000(model) yrs ago Deposition of Guildford Formation in progress (Coalescent alluvial fans) Perth coastal plain • Variable, alluvial Guildford Formation • Variable, alluvial • Poor trafficability, water management • Excavation • Locally blanketed by Bassendean sand The Hills • Hard ground • Dolerite dyke • Erodibility Sea Level (Fremantle) Time before -300 000 -200 000 -100 000 present (yrs) +10 m 0 m (Present) -50 m -100 m -120 m -14 000 Sea Level yrs Paleo Sea Level Humans in Perth Modern humans on Earth 164 x earlier (-66 000 000 yrs) Extinction of dinosaurs Sea Level (Fremantle) Time before -300 000 -200 000 -100 000 present (yrs) +10 m 0 m • Fremantle: (Present) 1897-2004: 1.54 mm/yr 1992-2010: 4 mm/yr -50 m (consistent with global trend) -100 m Global Sea Level Predictions -120 m -14 000 Sea Level yrs 'High Emission' scenario Paleo Sea Level 'Strong Mitigation' scenario Instrumented records Prediction (Intergovernmental Panel on Climate Change, 2013 ) Sea Level (Fremantle) Time before -300 000 -200 000 -100 000 present (yrs) +10 m 0 m • Fremantle: (Present) 1897-2004: 1.54 mm/yr 1992-2008: 4 mm/yr -50 m (consistent with global trend) -100 m Global Sea Level Predictions -120 m + 0.9 m ----> -14 000 Sea Level yrs Above today's level Paleo Sea Level + 0.4 m ----> • State Coastal Planning Policy: Instrumented records • Untill 2010: 0.38 m sea rise for next 100 yrs. • 2013: 0.9 m over next 100 years, then 10 mm per year. Prediction • Excludes extreme water levels. (Intergovernmental Panel on Climate Change, 2013 ) Tamala Limestone - Caves Two Rocks • Cavities occur in high strength limestone. • Greater risk near groundwater level, in contact with acidic water, specific vegetation. • City of Wanneroo local Planning Policy 4.13: Caves and Karstic Features Yanchep Tamala Limestone - Karst Risk ‘Fissure Cave’ Tamala Limestone - Karst Risk ‘Fissure Cave’ Tamala Limestone - Karst Risk ‘Fissure Cave’ Tamala Limestone - Karst Risk � 200 mm 200 mm Thank you. Queries? PILBARA KIMBERLEY PERTH SOUTH WEST.