Geologic Time Scale

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http://www.geosociety.org/science/timescale/

What was going on during these time periods?

During the Cenozoic (the last 65 million years): 

Zachos, 2008

The last 5.3 million years…

Raymo and Lisiecki, 2005 

What did the world look like when your sediment sample was deposited? 

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Grain Sizes

Clay – a term of size referring to rock or mineral fragments, of any composition, smaller than 0.004mm; clay is derived through continental weathering and by alteration of a wide range of rock materials

Silt – a term of size referring to rock or mineral fragments, of any composition, between 0.004mm and 0.062mm

Sand – a term of size referring to rock or mineral fragments, of any composition, between 0.062mm and 2mm; in marine environments, sand does not get transported far beyond the continental rise

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Diagram from the University of Texas A&M

Grain Sizes

Types of Sediment

Terrigenous – derived from the land or continent

Biocalcareous – composed of whole or fragmented calcite shells (foraminifera, pteropods, coccoliths…)
Biosiliceous – composed of whole or fragmented silica shells (radiolaria, diatoms…)

Bioclastic – composed of the remains of organisms (shells, bones, teeth…)

Authigenic minerals – formed in place, during or after deposition of the sediment they are found in; minerals that are formed by precipitation or recrystallization (some forms of pyrite and glauconite, calcite, gypsum, clays)

Pyroclastic – composed of volcanic material (ash, pumice…)

Ooze – a pelagic sediment composed of at least 30% skeletal remains (shells of forams, diatoms, radiolaria…), the rest being clay

Marl – calcareous clay; sediment made up of carbonate and clay or silt in varying amounts

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Diagram from the International Ocean Discovery Program

Types of Sediment

Common Types of Microfossils 

Forams (Foraminifera) – single celled organisms that make a calcite shell; scientists can extract chemicals from   their shells that can tell us when the animal lived as well as what its environment was like (~500mya). Forams have been around for millions of years, and there are many kinds of species. We can also figure out what species of Forams are in the sediment to figure out how old the sediment is.

How can we use forams to learn about Earth’s climate?

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Pteropods

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Coccoliths

Radiolaria – single celled organisms that make a shell of silica; by comparing living species to the fossil record, scientists can tell what past environments were like (~600mya) what does it mean if there are lots of radiolaria in your sample?https://micro.magnet.fsu.edu/micro/gallery/radiolarians/radiolarians.html

Diatoms – a type of algae that make a shell of silica; by comparing living species to the fossil record, scientists can tell what past environments were like (~200mya) what does it mean if there are lots of diatoms in your sample?http://www.daviddarling.info/encyclopedia/D/diatom.html

Sponge spicules – the structural framework (skeleton) of sea sponges; they are typically made of silica and mesh together to give the sponge support.

Echinoid spines- the spines of Echinoids, such as sea urchins

 

Common Types of Microfossils 

Some Common Minerals found in Sediment Cores

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Glauconite – typically green, smooth and rounded with a varied chemical composition; authigenic mineral that forms in shallow waters (100-300m) on the Continental Shelf in quiet waters (away from shore) with low sedimentation rates; glauconite can also be detrital


Quartz – clear, glassy with the chemical formula SiO2; the second most abundant mineral in continental crust (after feldspar); amethyst, citrine, rose quartz, smoky quartz, agate, onyx, jasper, tiger’s eye, carnelian, chalcedony, chert, flint, aventurine

 

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Pyrite – pale-bronze or brass-yellow (when ‘new’) with the chemical formula FeS2; can form inside animal shells filling voids and can replace the original shell matrix]


Gypsum – clear, white, gray with various crystal habits and chemical formula CaSO4*2H2O; it forms by precipitation as a result of evaporation


Micas – very common, thin/ flat shiny minerals that can be white or clear (muscovite), brown or green (biotite)  with complex chemical compositions


Limonite (mineral) – yellowish-brown to brown, amorphous; usually a secondary mineral; iron oxide-hydroxide


Calcite (mineral) – calcium carbonate; usually white or colorless

Some Common Minerals found in Sediment Cores