THE FOSSIL RECORD Movement of Ocean Water Surface currents Coriolis Effect

THE FOSSIL RECORD Movement 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 RECORD Movement 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 RECORD Movement of Ocean Water Thermohaline currents

THE FOSSIL RECORD Movement of Ocean Water Tides 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 RECORD Movement of Ocean Water Tides Areas that are alternately submerged and exposed by rising and falling tides are called tidal flats.

THE FOSSIL RECORD Water Temperature and Depth Water temperature varies with latitude

THE FOSSIL RECORD Water Temperature and Depth Water temperature also varies with depth

THE FOSSIL RECORD Water Temperature and Depth A zone of rapid temperature decrease with depth in a water mass is called the thermocline. At great ocean depths, temperatures may be just above freezing.

THE FOSSIL RECORD Light The well-illuminated water near the surface of the ocean is called the photic zone.

THE FOSSIL RECORD Light Light is used by certain organisms in the water for photosynthesis. Photosynthetic organisms are restricted to the near-surface waters.

THE FOSSIL RECORD Light Light penetration into the sea depends on: Sun angle

THE FOSSIL RECORD Light Light penetration into the sea depends on: Atmospheric conditions

THE FOSSIL RECORD Light Light penetration into the sea depends on: Conditions at the water surface

THE FOSSIL RECORD Light Light penetration into the sea depends on: Clarity of the water (or conversely, the amount of suspended sediment in the water)

THE FOSSIL RECORD Light 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 RECORD Seafloor Sediments Terrigenous Sediments Material weathered from the continents Mostly silt and clay

THE FOSSIL RECORD Seafloor Sediments Sediment of biologic origin Biogenic or Organic Sediments Sediment of biologic origin

THE FOSSIL RECORD Seafloor Sediments Calcareous oozes Biogenic or Organic Sediments Calcareous oozes Form in depths <4000 m Foraminifera, coccolithophores, and pteropods

THE FOSSIL RECORD Ocean Chemistry Carbonate Compensation Depth The 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 RECORD Ocean Chemistry Carbonate Compensation Depth Above 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 RECORD Ocean Chemistry Carbonate Compensation Depth Below 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 and siliceous ooze

THE FOSSIL RECORD Seafloor Sediments Calcareous oozes Biogenic or Organic Sediments Calcareous oozes

THE FOSSIL RECORD Seafloor Sediments Siliceous oozes Biogenic or Organic Sediments Siliceous oozes Form in cold, deep water Radiolarians and diatoms

THE FOSSIL RECORD Seafloor Sediments Phosphatic sediments Biogenic or Organic Sediments Phosphatic sediments Fish bones and teeth

THE FOSSIL RECORD Seafloor Sediments Manganese nodules Hydrogenous Sediments Manganese nodules (Authigenic or diagenetic minerals) Minerals that precipitate from sea water by chemical reactions.

THE FOSSIL RECORD Reconstructing Ancient Geography

THE FOSSIL RECORD Ancient Climatic Conditions Fossils can be used to interpret paleoclimates or ancient climates Fossil spore and pollen grains

THE FOSSIL RECORD Ancient Climatic Conditions Presence of corals indicates tropical climates

THE FOSSIL RECORD Ancient Climatic Conditions Plant fossils showing aerial roots, drip tips on leaves lack of yearly rings, large wood cell structure Indicate tropical climates

THE FOSSIL RECORD Ancient Climatic Conditions Marine molluscs (clams, snails, etc.) with spines and thick shells inhabit warm seas

THE FOSSIL RECORD Ancient Climatic Conditions Planktonic organisms vary in size and coiling direction according to temperature foraminifer Globorotalia Right coiled warm Left coiled cold

THE FOSSIL RECORD Ancient Climatic Conditions 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 RECORD Ancient Climatic Conditions

THE FOSSIL RECORD Extinctions 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 RECORD Extinctions