THE FOSSIL RECORDMovement of Ocean Water
Surface currents
Coriolis Effect
THE FOSSIL RECORDMovement of Ocean Water
Surface currents
Currents are also affected by the Earth's rotation through the Coriolis Effect. Currents in the northern hemisphere tend to be deflected toward the right (or clockwise), and currents in the southern hemisphere tend to be deflected to the left (or counter clockwise) as a result of the Coriolis Effect.
THE FOSSIL RECORDMovement of Ocean Water
Thermohaline currents
Thermohaline currents are initiated at the ocean surface by temperature and salinity conditions.
Gravity acts to pull colder (or more saline) denser water downward, displacing less dense water upward.
THE FOSSIL RECORDMovement of Ocean Water
Thermohaline currents
Tides are generated by the effect of the Moon's gravity (and to a lesser extent, the Sun's gravity) on the oceans. THE FOSSIL RECORDMovement of Ocean Water
Tides
Areas that are alternately submerged and exposed by rising and falling tides are called tidal flats. THE FOSSIL RECORDMovement of Ocean Water
Tides
THE FOSSIL RECORDWater Temperature and DepthWater temperature varies with latitude
THE FOSSIL RECORDWater Temperature and DepthWater temperature also varies with depth
THE FOSSIL RECORDWater Temperature and DepthA zone of rapid temperature decrease with depth in awater mass is called the thermocline. At great ocean depths, temperatures may be just above freezing.
THE FOSSIL RECORDLightThe well-illuminated water near the surface of the ocean is called the photic zone.
Light is used by certain organisms in the water for photosynthesis. Photosynthetic organisms are restricted to the near-surface waters. THE FOSSIL RECORDLight
Light penetration into the sea depends on: Sun angle THE FOSSIL RECORDLight
Light penetration into the sea depends on: Atmospheric conditions THE FOSSIL RECORDLight
Light penetration into the sea depends on: Conditions at the water surface THE FOSSIL RECORDLight
Light penetration into the sea depends on: Clarity of the water (or conversely, the amount of suspended sediment in the water) THE FOSSIL RECORDLight
In some areas, light may penetrate as deep as 200 m or more, but generally there is light adequate to support photosynthesis only in the upper tens of meters of the sea (to perhaps 100 m). THE FOSSIL RECORDLight
THE FOSSIL RECORDSeafloor Sediments
Terrigenous Sediments
Material weathered from the continentsMostly silt and clay
THE FOSSIL RECORDSeafloor Sediments
Biogenic or Organic Sediments
Sediment of biologic origin
THE FOSSIL RECORDSeafloor Sediments
Biogenic or Organic Sediments
Calcareous oozesForm in depths
THE FOSSIL RECORDOcean ChemistryCarbonate Compensation DepthThe Carbonate Compensation Depth or CCD is a particular depth in the oceans (varying from place to place), which effects where calcareous oozes may or may not accumulate.
THE FOSSIL RECORDOcean ChemistryCarbonate Compensation DepthAbove the CCD, water is warmer, and precipitation of CaCO3 is greater than dissolution. Calcareous plankton can be found in the water column, and on the bottom. Bottom sediments can consist of calcareous sediments forming chalk or limestone.
THE FOSSIL RECORDOcean ChemistryCarbonate Compensation DepthBelow the CCD, water is colder, and CaCO3 tends to dissolve (dissolution is greater than precipitation)
Tiny shells of CaCO3 dissolve, and do not accumulate on the bottom if water is deeper than the CCD
Below the CCD, the bottom sediments consist of clay andsiliceous ooze
THE FOSSIL RECORDSeafloor Sediments
Biogenic or Organic Sediments
Calcareous oozes
THE FOSSIL RECORDSeafloor Sediments
Biogenic or Organic Sediments
Siliceous oozesForm in cold, deep waterRadiolarians and diatoms
THE FOSSIL RECORDSeafloor Sediments
Biogenic or Organic Sediments
Phosphatic sedimentsFish bones and teeth
THE FOSSIL RECORDSeafloor Sediments
Hydrogenous Sediments
Manganese nodules
(Authigenic or diagenetic minerals)Minerals that precipitate from sea water by chemical reactions.
THE FOSSIL RECORDReconstructing Ancient Geography
Fossils can be used to interpret paleoclimates or ancient climatesFossil spore and pollen grains THE FOSSIL RECORDAncient Climatic Conditions
Presence of corals indicates tropical climates THE FOSSIL RECORDAncient Climatic Conditions
Plant fossils showing aerial roots, drip tips on leaveslack of yearly rings, large wood cell structure Indicate tropical climates THE FOSSIL RECORDAncient Climatic Conditions
Marine molluscs (clams, snails, etc.) with spines and thick shells inhabit warm seas THE FOSSIL RECORDAncient Climatic Conditions
Planktonic organisms vary in size and coiling direction according to temperature
foraminifer Globorotalia THE FOSSIL RECORDAncient Climatic Conditions Right coiledwarm
Left coiledcold
Oxygen isotope ratios in shells. 16O evaporates easier than oxygen-18 because it is lighter. 16O falls as precipitation and gets locked up in glaciers, leaving sea water enriched in 18O during glaciations. Shells that are enriched in 18O indicate times of glaciation. THE FOSSIL RECORDAncient Climatic Conditions
THE FOSSIL RECORDAncient Climatic Conditions
THE FOSSIL RECORDExtinctions The history of life has been marked by extinctions. The five largest extinction events are termed mass extinctions. These mass extinctions were sudden, global in extent, and very devastating. Mass extinctions occurred at the ends of the following periods: Ordovician Devonian (roughly 70% of the ocean's invertebrates disappeared) Permian (the greatest extinction. More than 90% of all marine species at that time disappeared or nearly went extinct) Triassic Cretaceous (affecting the dinosaurs ano other animals on land as well as organisms in the sea, about one fourth of all known families of animals became extinct)
THE FOSSIL RECORDExtinctions