MicrofossilsMicrofossils

Brandon McKeeBrandon McKee

OverviewOverview

What are microfossils?What are microfossils? Where are microfossils found?Where are microfossils found? How are stromatolites formed?How are stromatolites formed? What are the techniques used in What are the techniques used in

determining a microfossil?determining a microfossil? Do microfossils occur elsewhere in Do microfossils occur elsewhere in

our solar system?our solar system?

What are microfossils?What are microfossils?

Microfossils are just as their name Microfossils are just as their name implies, fossils that are microscopic.implies, fossils that are microscopic.

The oldest known and most familiar The oldest known and most familiar fossils, are from cyanobacteria in fossils, are from cyanobacteria in Archaean rocks. Archaean rocks.

Fossil Evidence - for the origin and Fossil Evidence - for the origin and evolution of early life is limited. Data evolution of early life is limited. Data suggest that life is at least as old as suggest that life is at least as old as the oldest rocks now known. the oldest rocks now known.

Time Line Time Line eon era period when began

myrs ago

duration myrs

Precambrian

Proterozoic

Sinian  (late Proterozoic)

Vendian 610 40

Sturtian 800 190

Riphean  (middle Proterozoic)

Karatau 1050 250

Yurmatin 1350 300

Burizan 1650 300

Animikean 2200 400

Huronian  2450 150

Archaean

   

Randian 2800 350

Swazian 3500 700

Izuan 3800 300

Hadean4000

Priscoan 4560 760

Other types of microfossilsOther types of microfossils Aside from cyanobacteria, identifiable fossil Aside from cyanobacteria, identifiable fossil

bacteria are not particularly widespread. bacteria are not particularly widespread. Under certain chemical conditions, bacterial cells Under certain chemical conditions, bacterial cells

can be replaced with minerals, notably pyrite or can be replaced with minerals, notably pyrite or siderite (iron carbonate), forming replicas of the siderite (iron carbonate), forming replicas of the once-living cells, or pseudomorphs.once-living cells, or pseudomorphs.

Some bacteria secrete iron-coated sheaths that Some bacteria secrete iron-coated sheaths that sometimes fossilize. sometimes fossilize.

Other bacteria may bore into shells or rocks and Other bacteria may bore into shells or rocks and form microscopic canals within form microscopic canals within the shell; such the shell; such bacteria are referred to as endolithic. bacteria are referred to as endolithic.

A chain of cyanobacterial cells, A chain of cyanobacterial cells, Bitter Springs Chert of N. AustraliaBitter Springs Chert of N. Australia

1 billion years old1 billion years old

Where are microfossils found?Where are microfossils found?

Microfossils are found…Microfossils are found…

Microfossils are thought to be found in Microfossils are thought to be found in stromatolites.stromatolites.

Canada has three of the world's known Canada has three of the world's known examples at Red Lake, Ontario, Steep examples at Red Lake, Ontario, Steep Rock Lake, Ontario, and near Yellowknife, Rock Lake, Ontario, and near Yellowknife, Northwest Territories. Northwest Territories.

Samples have been studied in Western Samples have been studied in Western Austalia and South Africa as well.Austalia and South Africa as well.

How are stromatolites formed?How are stromatolites formed?

Stromatolites - Mats of cyanobacteria Stromatolites - Mats of cyanobacteria or blue-green algae. or blue-green algae.

Mats trap carbonate mud. Mats trap carbonate mud. Cyanobacteria grow up through the Cyanobacteria grow up through the

mud to form new mat layer. mud to form new mat layer. These structures trap sediment and These structures trap sediment and

sometimes secrete calcium sometimes secrete calcium carbonate.carbonate.

Stromatolites TodayStromatolites Today

Best known site of stromatolite Best known site of stromatolite development to day is Solar Lake, which is development to day is Solar Lake, which is located 90 feet away from the Red Sea on located 90 feet away from the Red Sea on the Sinai Peninsula.the Sinai Peninsula.

Seepage from the Red Sea overlies saline Seepage from the Red Sea overlies saline water. water.

The upper layer accumulates during winter The upper layer accumulates during winter rains and acts like a lens, focusing the rains and acts like a lens, focusing the sun’s energy into the deeper layer.sun’s energy into the deeper layer.

The suns energy makes it so hot, higher forms The suns energy makes it so hot, higher forms of life cannot survive.of life cannot survive.

Near the shore, stromatolites lie matted on the Near the shore, stromatolites lie matted on the lake floor.lake floor.

In the middle of the lake, a thick mat floats In the middle of the lake, a thick mat floats some two feet below the water surface.some two feet below the water surface.

This makes it possible to walk on water!This makes it possible to walk on water!

How old are the fossils?How old are the fossils?

Structures thought to be 3.4 - 3.5 Structures thought to be 3.4 - 3.5 billion years old by stromatolites of billion years old by stromatolites of Western Australia.Western Australia.

Filaments resembling cyanobacteria Filaments resembling cyanobacteria are found in the Warrawoona Group are found in the Warrawoona Group of Western Australia and 2.8-3.0 of Western Australia and 2.8-3.0 billion year old rocks of southern billion year old rocks of southern Africa. Africa.

Testing TechniquesTesting Techniques

There are different methods in There are different methods in testing whether or not an organism is testing whether or not an organism is biological.biological.

The two I want to talk about are:The two I want to talk about are:– The Fourier Analysis Technique and KPZ The Fourier Analysis Technique and KPZ

equationequation– Megnetosom ComparisonMegnetosom Comparison

Fourier Analysis TechniqueFourier Analysis Technique

This is a method of recent study used This is a method of recent study used to determine if stomatolites formed to determine if stomatolites formed by biological organisms or by a by biological organisms or by a lifeless, physical process.lifeless, physical process.

Through mathematical analysis, two Through mathematical analysis, two Dr.’s (Grotzinger and Rothman) from Dr.’s (Grotzinger and Rothman) from MIT learned that stromatolites can MIT learned that stromatolites can sprout spontaneously on the sprout spontaneously on the seafloor.seafloor.

Rothman took 1.89 billion year old Rothman took 1.89 billion year old stromatolite and put it through the KPZ stromatolite and put it through the KPZ equation.equation.

This equation was developed to describe This equation was developed to describe how particles settle out to form an how particles settle out to form an undulating surface.undulating surface.

An example of this is snow falling. When An example of this is snow falling. When landing on a rocky terrain, there are basic landing on a rocky terrain, there are basic characteristics of a KPZ surface.characteristics of a KPZ surface.

This equation predicts how particles This equation predicts how particles behave as they form a surface—behave as they form a surface—sometimes sticking where they fall, sometimes sticking where they fall, sometimes rolling downhill to stick sometimes rolling downhill to stick somewhere else.somewhere else.

Rothman transformed the hills and valleys on Rothman transformed the hills and valleys on graph paper so there was longitude and latitude.graph paper so there was longitude and latitude.

Using the Fourier Analysis, he broke down the Using the Fourier Analysis, he broke down the irregular meanderings of the layers into smaller irregular meanderings of the layers into smaller undulations.undulations.

Emerging was a broad spectrum of symmetrical Emerging was a broad spectrum of symmetrical little waves, that, when added back together, little waves, that, when added back together, would reproduce the complex patterning in a would reproduce the complex patterning in a stromatolite.stromatolite.

The KPZ equation was then used to generate a The KPZ equation was then used to generate a similar spectrum of waves representing the hills similar spectrum of waves representing the hills and valleys of the stromatolite.and valleys of the stromatolite.

Rothman was correct. The two spectrums were Rothman was correct. The two spectrums were very similar. Similar enough to conclude that this very similar. Similar enough to conclude that this ancient stromatolite could have been made by a ancient stromatolite could have been made by a physical process.physical process.

The other type of testing technique is The other type of testing technique is magnetosom comparison.magnetosom comparison.

Martian meteorites have been analyzed to Martian meteorites have been analyzed to determine biogenics.determine biogenics.

Magnetotactic bacteria produce well Magnetotactic bacteria produce well ordered membrane-bounded intracellular ordered membrane-bounded intracellular crystals of magnetite or greigite called crystals of magnetite or greigite called magnetosomes. magnetosomes.

They are generally arranged in chains They are generally arranged in chains parallel to the long axis of the cell.parallel to the long axis of the cell.

The torque induced by the earths The torque induced by the earths magnetic field on the bacteria causes magnetic field on the bacteria causes them to align passively.them to align passively.

Comparison of a meteorite from Mars Comparison of a meteorite from Mars and Earth could determine if there and Earth could determine if there has been life on mars.has been life on mars.

There are six distinctive properties of There are six distinctive properties of magnetosomes.magnetosomes.– Narrow size range and shapeNarrow size range and shape– Chemical purityChemical purity– Few crystallographic defectsFew crystallographic defects– An unusual truncated hex-octahedral An unusual truncated hex-octahedral

morphologymorphology– Elongation along the [111] axisElongation along the [111] axis– Alignment of chains within cells.Alignment of chains within cells.

The results of the comparison are as The results of the comparison are as follows:follows:– One fourth of the Martian magetites are One fourth of the Martian magetites are

truncated hexa-octahedral which are truncated hexa-octahedral which are chemically and physically indistinguishable chemically and physically indistinguishable from terrestrial samples except for chain from terrestrial samples except for chain alignment. alignment.

– They share 5 of the six characteristics that They share 5 of the six characteristics that define the MV-1 biosignaturedefine the MV-1 biosignature

– Alignment of the chains within the cells was Alignment of the chains within the cells was not observed.not observed.

– This is due to when organisms die, the This is due to when organisms die, the membrane decomposes and the chain membrane decomposes and the chain collapses.collapses.

– Origin of the magnetites are possibly biogenic.Origin of the magnetites are possibly biogenic.

ConclusionConclusion

We have covered the following:We have covered the following:– What are microfossils?What are microfossils?– Where are they found?Where are they found?– How are stromatolites formed?How are stromatolites formed?– What are the techniques used to What are the techniques used to

determine a microfossil?determine a microfossil?– Are there microfossils elsewhere in the Are there microfossils elsewhere in the

solar system?solar system?

ReferencesReferences Earth, Vol. 6 Issue 2, 24, April, 1997Earth, Vol. 6 Issue 2, 24, April, 1997 Proc. Natl. Acad. Sci. USA, Vol. 98, Issue 5, 2164-Proc. Natl. Acad. Sci. USA, Vol. 98, Issue 5, 2164-

2169, February 27, 20012169, February 27, 2001 Natrual History, Vol. 107 Issue 7, 88, September Natrual History, Vol. 107 Issue 7, 88, September

19981998 Rocks and Minerals, Vol. 75 Issue 5, 300, Rocks and Minerals, Vol. 75 Issue 5, 300,

September/October 2000September/October 2000 Bioscience, Vol. 44 Issue 3, 181, March 1994Bioscience, Vol. 44 Issue 3, 181, March 1994 The Biology and Evolution of Fossil Plants. T.N. & The Biology and Evolution of Fossil Plants. T.N. &

E.L. Taylor. 1993.E.L. Taylor. 1993. Hofmann, Grey, Hickman & Thorpe, 1999, Hofmann, Grey, Hickman & Thorpe, 1999,

Geological Society of America Bulletin 111:1256-Geological Society of America Bulletin 111:1256-1262) 1262)