historical geology: fossils how do fossils form?

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HISTORICAL GEOLOGY: FOSSILS How do fossils form?

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Page 1: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

HISTORICAL GEOLOGY:FOSSILS

How do fossils form?

Page 2: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

What gets preserved?

• Fossils are the record of life preserved in stone. Almost all living organisms can leave fossils, but usually only the hard parts of plants and animals fossilize.

• The soft part get yucky and do not get preserved generally. There are some exceptions.

Page 3: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Trace Fossils

• Trace Fossils include the footprints of animals left in soft mud, later to be buried, and turned into stone.

http://consumerincentivezone.com/?nc=1

Page 4: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Fossils Don’t Stink• Under certain circumstances fossils of

animal dung, eggs, and even complete nest with eggs have been preserved in stone.

Page 5: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

ABC of Fossil Preservation

• Fossils are formed in a number of different ways, but most are formed when a plant or animal dies in a watery environment and is buried in mud and silt.

• Soft tissues quickly decompose leaving the hard bones or shells behind.

• Over time sediment builds over the top and hardens into rock.

• As the encased bones decay, minerals seep in replacing the organic material cell by cell in a process called "petrification."

Page 6: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Petrification

Page 7: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Mold Verse Cast

• Alternatively the bones may completely decay leaving a cast of the organism. The void left behind may then fill with minerals making a stone replica of the organism (mold).

http://people.uncw.edu/dockal/gly312/fossils/fossil2.jpg

http://www.gpc.edu/~pgore/myphotos/fossils/cast&mold.jpg

Page 8: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Sap to Amber

• Fossils can form in unusual ways. Small bugs or insects can become trapped in tree sap. Eventually the sap hardens and forms the semiprecious material called amber. In some pieces of amber the entombed remains of organisms can be found.

Page 9: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Let me Out of Here!!!!!

Page 10: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

When your Hot your Hot!!!• Volcanic eruptions can form fossils when

animals get trapped in the hot ash flows. In this case, the fossil is a hole in the shape of the animal.

http://www.msnucleus.org/membership/html/k-6/pt/hazards/3/images/pompeii.jpgwww.me.berkeley.edu

Page 11: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

To the Sea, to the Sea, to the Wonderful Sea.

• By far the most common fossil remains are those of shelled invertebrate sea loving creatures such as snails, corrals, and clams. These make up most of the fossil record.

http://oak.ucc.nau.edu/llc7/Photo%20Albums/Geology/slides/Cretaceous%20Marine%20Fossils.jpg

Page 12: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

MARINE FOSSILS RULE

http://www.langsfossils.com/sale-pics/marine/section-pics/marine-directory.jpg

www.lbl.gov

http://www.nhm.ac.uk/visit-us/galleries/life-galleries/fossil-marine-reptiles/

http://www.nhm.ac.uk/visit-us/galleries/life-galleries/fossils-from-britain/index.html

http://www.stonecompany.com/fossils/images/reptilez.JPG

Page 13: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Rare Finds

• Fossils of land animals are scarcer than those of plants. In order to become fossilized, animals must die in a watery environment and become buried in the mud and silt. Because of this requirement most land creatures never get the chance to become fossilized unless they die next to a lake or stream. Indeed there may be whole species of land animals in which no fossil record has been discovered. We may never know how many and diverse these animals were.

Page 14: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

The Incomplete Record

http://www.blackwellpublishing.com/ridley/tutorials/Fossils_and_the_history_of_life22.asp

http://www.ucmp.berkeley.edu/carboniferous/carblife.html

Page 15: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Relative Time

• Telling relative time simply involves placing events in a sequence relative to one another. This sort of time says nothing at all about age in years before the present.

Page 16: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Geologic Column

• • The geologic calendar

that we use to place events in a sequence of relative time is the geologic column. •The largest scale

division of time is into two eons.

•Precambrian eon (older)

•Phanerozoic eon (younger)

Page 17: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

ERAS

• Eons are divided into eras.

• Archean (older Precambrian)

• Proterozoic (younger Precambrian)

• Paleozoic (oldest Phanerozoic)

• Mesozoic (middle Phanerozoic)

• Cenozoic (youngest Phanerozoic)

Page 18: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

PERIODS

• •Eras are divided

into periods (see column for divisions)

•Periods are divided into epochs (see column for epochs of the Tertiary Period of the Cenozoic Era (Paleocene, Eocene, etc.)

Page 19: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Absolute time

• Absolute time is the age in years before the present of a rock or a particular geologic event. Ma refers to millions of years, and Ba refers to billions of years.

Page 20: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Absolute timeAbsolute ages are

generally assigned to events in the geologic column by radiometric dating of rocks formed during the events.

Radiometric dating depends upon the constant rate of decay of radioactive isotopes to produce stable daughter products. During the decay process, the isotope gives off energy in the form of subatomic particles and radiation generating heat.

Radioactive parent isotopes and their stable daughter

products

Radioactive Parent Stable Daughter

Potassium 40 Argon 40

Rubidium 87 Strontium 87

Thorium 232 Lead 208

Uranium 235 Lead 207

Uranium 238 Lead 206

Carbon 14 Nitrogen 14

Page 21: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Absolute time

• Basically, the geologist measures the ratio of parent isotope to daughter isotope in a rock, and knowing the rate of decay to form the daughter product, is able to calculate an age in years before the present.

• For this procedure to work, the rock must be a closed system, that is, no material can have been added or lost following the formation of the rock.

Radioactive Parent

Stable Daughter

Half life

Potassium 40 Argon 40 1.25 billion yrs

Rubidium 87 Strontium 87 48.8 billion yrs

Thorium 232 Lead 208 14 billion years

Uranium 235 Lead 207704 million

years

Uranium 238 Lead 2064.47 billion

years

Carbon 14 Nitrogen 14 5730 years

Page 22: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Absolute time

• Dates on igneous rocks give the age of crystallization

• Dates on metamorphic rocks give the age of the last metamorphic event.

• Dates on sedimentary rocks are meaningless if they come from minerals that predated the formation of the rock (i.e., minerals in a siliciclastic or terrigenous rock).

Parent

Daughter

1/2 Useful Range Type of Material

238

U206Pb 4.47

b.y

>10 million years 

Igneous & sometimes

metamorphic rocks and minerals

235

U207Pb 707

m.y

232

Th208Pb 14 b.y

40K40Ar &

40Ca

1.28 b.y

>10,000 years

87R

b87Sr 48 b.y

>10 million years

147

Sm143 106

b.y.

14C 14N 5,730 y

100 - 70,000 years Organic Material

>10 million years

Page 23: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Absolute time

Sedimentary rocks are usually dated by knowing their relationships to igneous rocks of known age, using superposition and cross-cutting relationships.

                                                      

Page 24: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Telling relative time• Principle of

Superposition - In a layered or stratified sequence of rocks, such as sedimentary rocks or lava flows or ash deposits, the rock at the bottom of the pile is the oldest and rocks successively higher in the pile are successively younger.

• http://www.classzone.com/books/earth_science/terc/content/investigations/es2903/es2903page03.cfm

Page 25: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Principle of Original horizontality

•Layered or stratified rocks are generally deposited horizontally.

•Departure from horizontality generally indicates some sort of deformation, such as tilting or folding.

• Deformation usually occurs during mountain building, but gentle regional tilting of rocks can occur during regional uplift of otherwise stable parts of the continent (the craton).

http://creationwiki.org/images/9/9f/Strata_folds.jpg

Page 26: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Cross-Cutting Relationships

When one body of rock, such as a dike, cuts across another rock, such as a sequence of layered sedimentary rocks, the rocks being cut are older and the rock doing the cutting is younger.

This also applies to situations where a fault cut across rocks. The rocks being faulted are older than the fault.

Page 27: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Principle of faunal succession •Organisms

change or evolve through time and species do not repeat themselves during this evolution.

•Certain fossils may be good indicators of certain intervals of time. “INDEX FOSSILS”

http://www.indiana.edu/~geol105b/images/gaia_chapter_6/relative_age_determination.htm

Page 28: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Index fossils

• Index fossils enable geologists to correlate sedimentary rocks. Index Fossils are fossils of organisms that were...

• abundant • geographically

wide-ranging • readily preserved • lived a short period

of time

http://www.utexas.edu/tmm/npl/beachcombing/images/austin_group.jpg

Page 29: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

• Unconformities and their significance • an unconformity is a surface in the rock record along which rocks

are missing and time is therefore not recorded. • the most obvious type of unconformity is an angular

unconformity, where rocks beneath the surface are more strongly deformed and those above the surface are less strongly deformed.

• unconformities often represent an interval of mountain building, where rocks are deformed, intruded by plutons and uplifted. Erosion removes rocks from the uplifted region, and subsequent subsidence (sinking) of the region is followed by deposition of sediment atop the unconformable surface.

Page 30: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Principle of Uniformitarianism

• Principle of Uniformitarianism or Actualism • This principle underlies all of the work we do in geology. This

is the way it works. Natural laws are unchanging. Therefore, the way natural laws govern geologic processes that are operating today is the same way that natural laws governed geologic processes that operated in the past. We can therefore use our understanding of present-day geologic processes to interpret past geologic events.

• Sometimes this principle is paraphrased as "the present is the key to the past", but be careful.

• Note, however, that the principle does not imply that past rates of process, or conditions under which the processes work, were the same as today. Nor does it imply that Earth's processes work at constant or uniform rates. Consequently, to avoid confusion, we often refer to the principle of uniformitarianism as "actualism."

Page 31: HISTORICAL GEOLOGY: FOSSILS How do fossils form?
Page 32: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

PRECAMBRIAN• The Precambrian

record starts about 3.8 billion years ago and lasted till 543 million years ago. Most of the earth’s history is during the Precambrian. Index fossil is the Stromatolite formed from Cyan bacteria and sediments in a shallow waters near shore.

http://3.bp.blogspot.com/_CqK2iKj3zjM/R1B8CWDzmrI/AAAAAAAAAMk/1wOk7RZtmHI/s1600-R/Proterozoic-Stroms.jpg

Page 33: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

CAMBRIAN the first Period in the Paleozoic Era

Time of the Cambrian Explosion– Many different life form suddenly developed (Burgess Shale).

Index fossils is the Trilobite.

Time: 543 to 490 Million years ago.

http://science.nationalgeographic.co.in/staticfiles/NGS/Shared/StaticFiles/Science/Images/Content/trilobite-fossil-422863-ga.jpg

http://users.path.ox.ac.uk/~wjames/Evolution/evolution4_files/slide0006_image035.jpg

Page 34: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

ORDOVICIAN PERIOD• Ordovician life

consisted of brachiopods, bryozoans, Cephalopods, gastropods, echinoderms, corals pelecypods and the graptolites (Index fossil). Time span 443 -490 million years ago.

http://www.fossils-facts-and-finds.com/images/graptolite-250.jpg

http://www.museumwales.ac.uk/media/3/7/3/4/thumb_200/graptolite.jpg

Page 35: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

SILURIAN PERIOD

• Silurian life is similar to those found in the Ordovician. Except a new animal has appeared. The Eurypterid (sea scorpion). Shallow seas covering N.A. begin to dry up. Large deposits of Salt and Gypsum develop.

http://geology.stlawu.edu/wp-content/uploads/eurypterid.jpg

Page 36: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Devonian Period

• Age of the Fishes– Jawless fish like

lampreys, jawed fish which were armored.

– First lungfish appears.– Birth of the

Appalachian Mountains occurs.

– Time 417 - 354 Million years ago.

http://allhatnocattle.net/fossil-fish.jpg

http://www.fmnh.helsinki.fi/verkkonayttelyt/elamanhistoria/nayttelykuvat/devoni_kalafossiili.jpg

Page 37: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Carboniferous Periodor the Mississippian and Pennsylvanian Periods

• Mississippian was when the crinoids and foraminifera made their appearance.

• Pennsylvanian (Swamps) was when the first reptiles became the 1st land animals.

• Time Miss- 354 – 323 million years ago.

• Time Penn- 324 – 290 million years ago.

http://www.fossilmall.com/EDCOPE_Enterprises/echinoderms/crinoids11/CK04B.jpg

http://www.kgs.ku.edu/Extension/fossils/gifs/fusul_draw.gif

Page 38: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Permian Period

• Time of wide spread mountain building. Pangaea has formed

• Nearly ½ of all known animal groups have become extinct. Diversity of animals within a group is greatly reduced.

• Survivors Cephalopods and reptiles.

• Time 290 to 248 Million years ago.

http://www.gc.maricopa.edu/earthsci/imagearchive/cephalopod.jpg

http://www.tucsonshow.com/reports/tucson2002/images/mvc-112x.jpg

Page 39: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Mesozoic Era-Triassic, Jurassic, and Cretaceous Periods

• Triassic Period 248-206 million years ago.

Index fossil is the Ammonites part of the Cephalopods. Plants have invaded the land including fern trees, cycads, and conifers. Pangaea is joined still but has begun to split.

http://www.discoveringfossils.co.uk/ammonite_sutures2.jpg

Page 40: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Mesozoic Era-Triassic, Jurassic, and Cretaceous Periods

• Jurassic Period- 206 to 144 million years ago.

• Large Dinosaurs roam the earth, and some smaller dinosaurs are evolving into birds and Insects are everywhere.

• Mammals make their first appearance (rodent like)

http://ngm.nationalgeographic.com/2008/07/tyrannosaur-trap/gwin-text

Page 41: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Mesozoic Era-Triassic, Jurassic, and Cretaceous Periods

• Cretaceous Period 144 to 65 Million years ago.

• Tyrannosaurus roamed the earth along with many other large meat eaters.

• The period comes to an abrupt halt. Why, not really known. Possible Asteroid impact, causing dust to block the sun. What ever the cause 50 % of all plants and animals were wiped out.

http://www.uky.edu/KGS/education/images/k_extinct.jpg

Page 42: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Cenozoic Era – Paleogene, Neogene, and Quaternary Periods

• Cenozoic Era 65 million years ago to recent.

• Paleogene Period 65 to 24 million years.

• Consist of the Paleocene, Eocene, and Oligocene Epoch.

• During the Paleocene the western mountains are forming. In the Eocene coal in western NA is forming. And during the Oligocene the Alps and Himalayas are rising.

• The Cenozoic Era

http://hoopermuseum.earthsci.carleton.ca/evolution/equidae/cenozoicera.html

Page 43: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Cenozoic Era – Paleogene, Neogene, and Quaternary Periods

• Plaeogene Period-fossils indicate many new species of mammals.

http://www.paleocene.com/copyright/images/paleocene_forest.jpg

Page 44: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Cenozoic Era – Paleogene, Neogene, and Quaternary Periods

• Neogene Period 24 to 2 million years ago.

• Consist of the Miocene, and Pliocene Epochs.

• Mammals have made great progress and are the dominate large organism.

• During the Pliocene Man makes his entrance. The climate is changing.

http://www.talkorigins.org/faqs/homs/dawn.gif

Page 45: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Cenozoic Era – Paleogene, Neogene, and Quaternary Periods

• Welcome to the Quaternary Period which started about 2 million years ago and continues thru today.

• If you haven’t noticed Hominids have done real well, and are now the top dog so to speak.

Page 46: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

The Family Picture

• 1 HOMO HABILIS ~ NICKNAME: Handyman LIVED: 2.4 to 1.6 million years ago HABITAT: Tropical Africa DIET: Omnivorous – nuts, seeds, tubers, fruits, some meat2 HOMO SAPIEN ~ NICKNAME: Human LIVED: 200,000 years ago to present HABITAT: All DIET: Omnivorous - meat, vegetables, tubers, nuts, pizza, sushi3 HOMO FLORESIENSIS ~ NICKNAME: Hobbit LIVED: 95,000 to 13,000 years ago HABITAT: Flores, Indonesia (tropical) DIET: Omnivorous - meat included pygmy stegodon, giant rat4 HOMO ERECTUS ~ NICKNAME: Erectus LIVED: 1.8 million years to 250,000 to 30,000 years ago HABITAT: Europe and Western Asia DIET: Relied heavily on meat, such as bison, deer and musk ox

• 100,000 years ago HABITAT: Tropical to temperate - Africa, Asia, Europe DIET: Omnivorous - meat, tubers, fruits, nuts5 PARANTHROPUS BOISEI ~ NICKNAME: Nutcracker man LIVED: 2.3 to 1.4 million years ago HABITAT: Tropical Africa DIET: Omnivorous - nuts, seeds, leaves, tubers, fruits, maybe some meat6 HOMO HEIDELBERGENSIS ~ NICKNAME: Goliath LIVED: 700,000 to 300,000 years ago HABITAT: Temperate and tropical, Africa and Europe DIET: Omnivorous - meat, vegetables, tubers, nuts7 HOMO NEANDERTHALENSIS ~ NICKNAME: Neanderthal LIVED:

http://www.theage.com.au/ffximage/2005/03/18/evolution_1903_wideweb__430x328,1.jpg

Page 47: HISTORICAL GEOLOGY: FOSSILS How do fossils form?

Cited

• http://www.scienceviews.com/dinosaurs/fossilformation.html

http://www.winona.edu/geology/MRW/lecture5.htmlhttp://facstaff.gpc.edu/~pgore/geology/geo102/radio.htmhttp://www.tulane.edu/~sanelson/eens211/radiometric_dating.htmhttp://websearch.cs.com/cs/img.jsp?img=http%3A%2F%2Fwww.theage.com.au%2Fffximage%2F2005%2F03%2F18%2Fevolution_1903_wideweb__ __430x328%2C1.jpg