GEOL40310 Lecture A3 Sedimentary Basins 2023 PDF

Geol 40310 Fossil Fuels and Carbon Capture & Storage (CCS) Lecture A3: Sedimentary basins and Sedimentary rocks Autumn 2023-24 1 1 Lecture A3: Sedimentary basins and Sedimentary rocks Sedimentary basins Examples: Foreland Basin, Rift Basin, Strike-slip basin Clastic Sedimentary rocks: Depositional...

Geol 40310 Fossil Fuels and Carbon Capture & Storage (CCS) Lecture A3: Sedimentary basins and Sedimentary rocks Autumn 2023-24 1 1 Lecture A3: Sedimentary basins and Sedimentary rocks Sedimentary basins Examples: Foreland Basin, Rift Basin, Strike-slip basin Clastic Sedimentary rocks: Depositional environments of clastic sediments Lithification of sediments to rocks Classification of clastic sedimentary rocks Biochemical and Chemical sedimentary rocks Organic Sedimentary rocks 2 2 Geol 40310 Lecture A3 1 Sedimentary Basins The world’s giant oilfields The World’s sedimentary basins Oil and gas is almost always located in young sedimentary basins 3 3 Sedimentary Basins • Sediments are deposited in topographic lows. • Sedimentary basins are formed where tectonic activity produces these lows 4 4 Geol 40310 Lecture A3 2 Types of basins hosting giant oil and gas fields discovered 2000-2012 Bai and Xu, Oil and Gas Journal, 02/03/2014 5 5 Rift basin – e.g. the Central and Viking Grabens, North Sea • e.g. North sea. • Space created by divergent plate boundary • Subsidence of the thinned crust creates additional space for younger, “sag” deposits. • Sediment supplied from the adjacent basement highs. Post rift (sag) Syn-rift Pre-rift 10 km 100 km 6 6 Geol 40310 Lecture A3 3 Rift basin Codling Fault Space created by extension perpendicular to basin orientation e.g. Central Irish Sea Basin: NE-SW striking basin produced by NW-SE oriented extension 7 7 Strike-slip basins Space created by extensional step in the transform fault. Loch Neagh basin created by a step in the still-active Codling fault e.g. Loch Neagh 8 Hugh Anderson PhD, (2013) 8 Geol 40310 Lecture A3 4 Foreland Basin • Flexure of crust due to overthickened mountain belt • Basin filled from erosion of mountains. • e.g. Po basin, Italy 9 9 Erosion and Sediment Load Suspended load: ca. 1000 million tons/year Dissolved load: ca. 150 million tons/year Himalayan foreland basin 10 10 Geol 40310 Lecture A3 5 Sediment Fans Sediment from rivers can travel thousands of kilometres underwater before being deposited 11 11 Fluvial (River) deposits Braided Rakaia River, New Zealand Budleigh Salterton Pebble bed, SW England. 12 12 Geol 40310 Lecture A3 6 Shallow Marine deposits Selanga river delta, Lake Baikal Delta deposits, Book Cliffs, Utah (Photo Jennifer Aschoff) 13 13 Deepwater fan deposits Lobe sandstone deposits at Ross Bay, Co Clare, Ireland 14 14 Geol 40310 Lecture A3 7 Fine-grained deposits Fine-grained clastics are deposited in quiet water settings: Floodplains, lagoons, mudflats, deltas, deep-water basins. Organic-rich shales are the source of oil and gas. Marshak (2011) 15 15 Aeolian (wind-blown) deposits Namib desert, Namibia Navajo Sandstone, Utah 0.1mm Sandstone (McCann and Sothcott (2009) 16 16 Geol 40310 Lecture A3 8 Depositional environments for siliciclastic sedimentary rocks Alluvial fan Delta River Deep marine turbidite fan Desert 17 Diagenesis and metamorphism Sediment Sedimentary rock Diagenesis Metasedimentary rock Metamorphism 18 18 Geol 40310 Lecture A3 9 19 19 20 20 Geol 40310 Lecture A3 10 Classification of sedimentary rocks – Composition Sandstones, limestones, clays: Silica Carbonates Pure and impure sandstones: Hydrated clays More about this in practical 2… 21 21 Classification of clastic sedimentary rocks – Grain size and angularity 22 22 Geol 40310 Lecture A3 11 Classification of clastic sedimentary rocks – sorting and angularity Mature sandstone – well sorted, rounded quartz grains. Immature sandstone – poorly sorted angular grains,mixed mineralogy 23 Marshak (2011) 23 carbonates 24 24 Geol 40310 Lecture A3 12 Biochemical Sedimentary rocks Limestone atoll surrounding a volcanic Island (Maupiti , French Polynesia) Limestones form reefs in warm, shallow, clean seas. Acidification is having a detrimental effect on limestone formation in many oceans Photo: Khaled bin Sultan Living Oceans Foundation Great Barrier Reef - Australia Photo: Australian Geographic 25 25 Biochemical Sedimentary rocks - limestone Limestones form in shallow, warm waters where invertebrate animals (e.g. shells, crinoids, byrozoans) live. They absorb calcium carbonate from the water to form their skeletons. When they die their skeletal calcareous debris is lithified to form limestones. 26 26 Geol 40310 Lecture A3 13 Biochemical Sedimentary rocks - Chalk SEM Photomicrograph of Chalk porosity. (Strand et al. 2007) 2μm SEM of Recent Coccoliths 2μm 27 27 Chemical Sedimentary rocks - evaporites 28 28 Geol 40310 Lecture A3 14 Chemical Sedimentary rocks - Ooidal limestones Modern day ooids, Bahamas Kansas Geological Society Ooids are spherical grains of calcium carbonate precipitated around a nucleus in shallow tropical seas 1 mm (Wikipedia) 29 29 Organic Sedimentary rocks - Peat, lignite, coal… 8 million year old cypress trees preserved in lignite, Hungary Photo: Reuter.com 30 Geol 40310 Lecture A3 15 Global Sediment Thickness Allen and Allen (2013) 31 31 31 Lecture A3: Sedimentary basins and Sedimentary rocks Sedimentary basins Examples: Foreland Basin, Rift Basin, Strike-slip basin Clastic Sedimentary rocks: Depositional environments of clastic sediments Lithification of sediments to rocks Classification of clastic sedimentary rocks Biochemical and Chemical sedimentary rocks Organic Sedimentary rocks 32 32 Geol 40310 Lecture A3 16