THE FOSSIL RECORD Movement of Ocean Water Surface currents Coriolis Effect

THE FOSSIL RECORDMovement of Ocean Water

Surface currents

Coriolis Effect


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.


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.


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


Biogenic or Organic Sediments

Sediment of biologic origin



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



Calcareous oozes



Siliceous oozesForm in cold, deep waterRadiolarians and diatoms



Phosphatic sedimentsFish bones and teeth


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

THE FOSSIL RECORD Movement of Ocean Water Surface currents Coriolis Effect

Documents

Transcript of THE FOSSIL RECORD Movement of Ocean Water Surface currents Coriolis Effect