Ocean circulation: The open university 2nd edition. p. 286. • Kennett J.P., 1982.
Marine Geology. • Emery, D. and Myers, K.J., 1996, Sequence Stratigraphy ...
GEO 3121: Marine Geology Juergen Mienert
Høst 2008
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Literature • The ocean basins: Their structure and evolution. The open • • •
university 2nd edition. p. 185. Ocean chemistry and deep-sea sediments. p.134 Seawater: Its composition, properties and behaviour. The open university 2nd edition. p. 168. Ocean circulation: The open university 2nd edition. p. 286.
• Kennett J.P., 1982. Marine Geology. • Emery, D. and Myers, K.J., 1996, Sequence Stratigraphy 2
Introduction • What is the goal of this course? • What is marine geology and why is it important? • Sediments of the Oceans: Touring today’s sea bed from microscopic to macroscopic features
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What is the goal of this course? • Understanding the oceans and its geology: To introduce the fundamental oceanographic and geological processes active in marine environments.
• Understanding the marine environment: To provide a solid background for the characteristics of marine geology in various parts of the world's oceans focussing on polar regions.
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What is marine geology? • Marine geology is a discipline of geological sciences in oceans. (sea floor spreading & plate tectonic, ocean crust, sediments above ocean crusts, stratigraphy, chronostratigraphy, sea floor morphology)
• Investigations concentrate on ocean conditions relevant for sediment accumulation or transportation. Data acquisition (CTD, sediment traps, benthic sledges, current meters etc.) carried out from ships.
• Investigations concentrate on the sea floor and sub-sea floor geology. Data acquisition (seismic profiling, sediment coring) carried out from ships, submersibles or remotely operated vehicles.
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Oceans: 1338 x 106 km3 Total: 1386 x 106 km3 7
Properties of water
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The ocean planet- OCEANUS 1. How did the earth acquire such a large amount of water in the first place? 2. Once acquired, how was it retained? First question has to do how the earth was formed, and the second involves the evolution of the earth and its atmosphere! 1. Earth created by a gravitational collapse, where heavier elements migrate to the centre and lighter elements (H,O,..) are still in the orbit. 2. Sun stabilized and the Earth went through a process of degassing from its interior and it developed a lithosphere, atmosphere (CH4, CO2 but no oxygen) and hydrosphere. The tempertaure of the Earth dropped and water condensed into the oceans. The mass of water present in the ocean is about the same as the mass of water that was contained in the crust when the degassing process started. Note: First known rock evidence for water comes from zircons (E-Greenland= 3,8 billion yrs, Australia= 4,3 billion yrs) 9
Why is it important? • The ocean is covering approx. 71 % of our planet; it is the very source of life on Earth. Over 90 percent of our planet’s living and non-living resources are found within ocean margins a few hundred kilometres of the coasts, where two-thirds of the world’s population is living.
• Even if we are improving our understanding of how the ocean system is functioning today, we are a very long way from being able to predict natural changes and man induced changes that may be expected in the next century due to global climate impacts. 10
• Improved and more systematic observations of the ocean surrounding our continents allow a better understanding of our planet’s dynamics (Storegga film).
• There are drastic environmental changes natural and man made and research knowledge may help to forecast or even prevent otherwise unforeseen events.
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• The majority of rocks exposed at the Earth's surface have their origin in the oceans, either as sediments or as igneous rocks. An igneous rock has solidified from magma (lava flows, ocean crust).
• Therefore, to understand earth science processes it is necessary to know what is happening in ocean basins.
• If you do understand the action of endogen forces than you can answer why 70% of the earth is covered by the ocean, why 2/3 of the land masses is on the northern hemisphere, why the average water depth of the ocean is 3700 meters, why marine resources such as for example oil and gas occur in ocean margins?
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The planet earth “Oceanus” • The ocean contains about 1.360.000 km3 of liquid water. Since there have been about 26 ice ages during the last 2,6 Mio years, water mass volume and sealevel changed as well.
• How much ice exists on earth today and how much sea-level change could be caused by these ice masses? - 32.000.000 km3of ice equivalent to - 70 m sea level rise
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Sediments of the oceans Touring today’s sea bed from microscopic to macroscopic features
Ocean chemistry and deep sea sediments
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Biogenous sediments Calcareous ooze (calcitic or aragonitic): 48% Silicious ooze (zooplankton and phytoplankton): 14%
Terrigenous sediments fluvial aeolian ice rafted debris (IRD)
Ocean chemistry and deep sea sediments
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Carbonate sediments - foraminifera • calcitic zooplankton • quite large (scale bar 50 micron)
Ocean chemistry and deep sea sediments
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Carbonate sediments - pteropods • aragonitic zooplankton • size variable
Ocean chemistry and deep sea sediments
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Carbonate sediments - coccoliths
• phytoplankton (algae) • small (typically 10 micron)
Ocean chemistry and deep sea sediments
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Calcareous ooze
Photograph H. Edmonds
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Siliceous sediments - radiolarians • siliceous zooplankton • 50 - 300 microns (scale bar 50 microns)
Ocean chemistry and deep sea sediments
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Siliceous sediments - diatoms • siliceous phytoplankton • 10-200 microns in diameter (scale bar 20 micron)
Ocean chemistry and deep sea sediments
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Red clay sediments • cosmic dust particles / •
spherules of Ni-Fe with oxidisation layer aeolian sediments
Ocean chemistry and deep sea sediments
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Red clay of the deep ocean
Heezen and Hollister, 1971
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Pillow basalts of the mid-ocean ridges (MOR)
Heezen and Hollister, 1971
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Manganese nodules of the seabed
More on web site
Heezen and Hollister, 1971
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Photograph of the Sea Bed • pelagic •
sedimentation bioturbation
Heezen and Hollister, 1971
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Evidence for life in the abyss
Heezen and Hollister, 1971
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Evidence for deep ocean currents – sediment ripples
Heezen and Hollister, 1971
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Terrigeneous sediments • Debris from erosion processes or ice melting (IRD) • Grain size varies from very coarse in littoral to very fine grained in distal ocean regions depending on the transport energy
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Summary • The sea floor of the deep ocean is often flat due to reduced gravitational forces and minor submarine erosion.
• There are terrigenous and biogenous sediments that lie upon igneous rocks. (There are also sediments due to chemical processes but we will hear about them later).
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