Skala Waktu Geologi 12 Okt 2012

7/30/2019 Skala Waktu Geologi 12 Okt 2012

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Geologic time is divided into a four-level hierarchy

of time intervals:

EONS -- The first and largest division of geologic time. ERAS -- The second division of geologic time; each era has

at least two periods.

PERIODS-- The third division of geologic time.

Periods are named for either location or characteristics of thedefining rock formations.Location = the region where the period's characteristicrocks were first studied.

Characteristics = the nature of the unique system of rocksand rock formations that define the Period.

EPOCHS -- The fourth division of geologic time;represents the subdivisions of a period.


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Geologists use a number of techniques to determine theage of rocks, for instance:

basic field observations help them work out therelative sequence of geological events, such as the

order in which sediments were deposited; because species evolve and become extinct, fossils of

some plants and animals are confined to knownperiods of geological time; and

because radioactive elements decay at a known rate, insome circumstances they can be used to calculate howmany years have passed since a mineral crystallised ora rock was deposited.
http://www.bgs.ac.uk/discoveringGeology/time/fossilfocus/home.htmlhttp://www.bgs.ac.uk/discoveringGeology/time/fossilfocus/home.html


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Fossil yang bisa digunakan untuk penentuan umur

hanya yang bersifat insitu ditempat hidupnya(Biocoenoese) dan atau yang terpindahkan daritempat hidupnya Thanathocoenoese).

Fossil yang bisa digunakan untuk penentuan

lingkungan hidup atau lingkungan pengendapanhanya yang bersifat insitu (Biocoenoese)

Fossil yang berasal dari rombakan yang lebih tuatidak bisa digunakan untuk menentukan baik

Umur maupun lingkungan pengendapan(Reworked fossil)


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Life began 3.8 billion years ago, and insects diversified 290

Million years ago, but the human and chimpanzee

Lineages diverged only five million years ago. How have

scientists figured out the dates of long past evolutionary

events?

Here are some of the methods and evidence that scientists

Use to put dates on events: 1. Radiometric datingrelies on half-life decay of

radioactive elements to allow scientists to date rocks andmaterials directly.

2. Stratigraphy provides a sequence of events from whichrelative dates can be extrapolated.

3. Molecular clocks allow scientists to use the amount ofgenetic divergence between organisms to extrapolatebackwards to estimate dates.


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The age of the Earth and its inhabitants has been determined

Through two complementary lines of evidence: relative

Dating and numerical (or radiometric) dating.

Relative datingplaces fossils in a temporal sequence bynoting their positions in layers of rocks, known as strata.Sometimes this method doesn't work, either because thelayers weren't deposited horizontally to begin with, or

because they have been overturned.If that's the case, we can use one of three other methods todate fossil-bearing layers relative to one another:

faunal succession, crosscutting relationships, and

inclusions.By studying and comparing strata from all over the worldwe can learn which came first and which came next, butwe need further evidence to ascertain the specific, or

numerical, ages of fossils.


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Fundamental principles of Geology(7 principles to establish the relative ages of rocks).

Most sedimentary rocks occur in the form oflayers called beds or strata.Each layer is the result of the deposition ofsediment during some natural event (such as aflood or storm).


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A. Steno's Laws Named for Nicholaus Steno, a Danish

physician living in Florence, Italy in the 1600's.

1. Principle of SuperpositionOldest rocks on the bottomYounger rocks on top

2. Principle of Original HorizontalitySediments are deposited in flat layers

3. Principle of Original Lateral ContinuitySediments are deposited over a large area in acontinuous sheet


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B. Other basic principles of Geology which we can usefor relative dating (or determining which rocks areolder or younger)

4. Principle of intrusive relationships

The intrusion is younger than the rocks it cuts


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5. Principle of cross-cutting relationships

The fault is younger than the rocks it cuts.


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6. Principle of components or inclusions

Note the irregular erosional surface.This is an Unconformity.

The clasts (in the bed above the unconformity) are derivedfrom the underlying (older) bed.The gravel clasts are olderthan the layer which containsthem. The layer containing the gravel must be younger thanthe layer from which the clasts originate.


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The principle of components or inclusions also

applies to xenoliths.

A xenolith is a fragment of country rockswhich has been broken off during an

intrusion, and has become surrounded bymagma.

The xenolith is older than the igneous rock whichcontains it.


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7. Principle of fossil succession

Fossils occur in a consistent vertical order insedimentary rocks all over the world.(William"Strata Bill" Smith, late 1700's,

England). This principle is valid and does not depend on any

pre-existing ideas of evolution. Geologists interpret fossil succession to be the

result of evolution - the natural appearance anddisappearance of species through time.


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Angular unconformities Implies tectonic deformationand erosion of underlying strata.

Nonconformity Sedimentary strata overlying igneous

or metamorphic rocks (in an erosional - not intrusive-contact)

Disconformity An irregular surface of erosion betwentwo units of parallel strata

Paraconformity A planar surface between two parallelunits of sedimentary rock, representing a period ofnon-deposition, but no erosion.


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ANGULARunconformity

Nonconformity

Disconformity

Paraconformity


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Numerical datingrelies on the decay ofradioactive elements, such as uranium, potassium,

rubidium and carbon.Very old rocks must be dated using volcanicmaterial. By dating volcanic ash layers both aboveand below a fossil-bearing layer, as shown in the

diagram, you can determine "older than X, butyounger than Y" dates for the fossils.

Sedimentary rocks less than 50,000 years old canbe dated as well, using their radioactive carboncontent


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Many minerals contain radioactive isotopes. In theory, the age of any of theseminerals can be determined by

1) counting the number of daughter isotopes in the mineral, and

2) using the known decay rate to calculate the length of time required to producethat number of daughters.


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The time of the transition from one interval of

geologic time to the subsequent one is usuallymarked by a relatively abrupt change in fossiltypes and numbers.

is not known precisely, with the uncertaintyincreasing with increasing age since fossilsbecome rarer and harder to identify in the

distant past.


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http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13


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PRE-ARCHEAN EON (or HADEAN EON)(4.6 to 3.8 Billion years)

~4.6 BYA -- Formation of Earth and Moon (asindicated by dating of meteorites and rocks from

the Moon) ,

The Earth forms and is bombarded by meteorites andcomets.

~4 BYA -- Likely origin of life

This is the "hidden" portion of geologic time asthere is little evidence of this time remaining inEarth's rocks
http://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.html


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ARCHEAN EON (3.8 to 2.5 Billion years)

The eon of first life

~3.8 BYA -- Oldest known rocks, Replicatingmolecules (the precursors of DNA) form.

~3.5 BYA -- Oldest known fossils (single celledorganisms resembling bacteria), Unicellular lifeevolves. Photosynthetic bacteria begin to releaseoxygen into the atmosphere.

3.2 BYA -- First known plants (algae)
http://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.html


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PROTEROZOIC EON

(2.5 Billion to 570 Million years)

The eon of the first multicelled life

1.2 BYA -- First known animal (jellyfish)(End of the Pre-Cambrian -- a period at leastfive times longer than all the geologic time thatfollows.),


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The eon of complex life


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The era of ocean life;

land animals appear toward the end ofthis era

Cambrian Period (570 to 505 Millions years)O k d b h f fi h llfi h d


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Onset marked by the appearance of first shellfish andcorals; sometime called the "age of marine invertebratesAbundant fossils appear in the rock record for the first

timeEnd of the Cambrian denoted by the appearance of fish,Multi-cellular marine organisms are common.

Between 510M and 505MYA - Fish first appear in the fossil

record; these are the first vertebrates,

Ordovician Period (505 Million years to 438 Millionyears)

Arthropods move onto the land. Their descendants evolveinto scorpions, spiders, mites, and millipedes. Fish-likevertebrates evolve.

Invertebrates, such as trilobites, crinoids, brachiopids, andcephalopods, are common in the oceans.

Sil i P i d (438 Milli t 408 Milli )
http://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.html


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Silurian Period (438 Million to 408 Million years)Appearance of the first land plants; mountain buildingin Europe Land plants evolve, drastically changing

Earth's landscape and creating new habitats.,

Devonian Period (408 to 360 Million years)The first insects and first amphibians/tetrapods; "age

of fishes, first abundant forests on landCarboniferous Period

Mississippian Period (360 to 320 Million years)

Abundant amphibians and the appearance of the first

reptiles, Four-limbed vertebrates move onto the land asseed plants and large forests appear. The Earth's oceanssupport vast reef systems.
http://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.html


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Pennsylvanian Period - 320 to 286 Million years

305 MYA -- The first mammal-like reptiles

Permian Period - 286 to 245 Million yearsReptiles spread and diversify; evaporate deposits;

glaciation in the Southern HemisphereOver 90% of

marine life and 70% of terrestrial life go extinct duringthe Earth's largest mass extinction.

Ammonites are among the survivors.,

The supercontinent called Pangea forms.

Conifer-like forests, reptiles, and synapsids (theancestors of mammals) are common.


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Triassic Period (245 to 208 Million years)Fi t f l ( d 222 MYA)


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First appearance of mammals (around 222 MYA);

First appearance of dinosaurs in the fossil record,Dinosaurs and mammals evolve. Pangea has begun to

break apart.Jurassic Period (208 to 145 Million years)dominance of the dinosaurs; mountain building inNorth America

150 MYA -- First birdsCretaceous Period (145 to 65 Million years)Flowering plants appear and spread rapidly; continuedincrease in dinosaurs.Climate warmer than at present, with sea level higherAs the continents drift toward their present positions,the earliest flowers evolve, and dinosaurs dominate thelandscape. In the sea, bony fish diversify.

This period (and also the Mesozoic Era) end abruptly

with death of the dinosaurs,


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The era of mammals

Tertiary Period (65 Million to 1.6 Million years ago)Paleocene Epoch (65 Million to 58 Million years ago)


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Paleocene Epoch (65 Million to 58 Million years ago)Began with extinction of the dinosaurs , A massiveasteroid hits the Yucatan Peninsula, and ammonites and

non-avian dinosaurs go extinct. Birds and mammals areamong the survivors.Mountain building in Europe and AsiaEocene Epoch (58 Million to 37 Million years ago)Horses (around 53 MYA), whales, and monkeys firstappear in the fossil recordOligocene Epoch (37 Million to 24 Million years ago)Elephants and apes first appear in the fossil recordMiocene Epoch (24 Million to 5 Million years ago)

Hominids first appear in the fossil recordPilocene Epoch (5 Million to 1.6 Million years ago)The ice ages begin, and many large mammals go extinct.2 MYA -- First humanlike animal ,In Africa, an early

hominid, affectionately named "Lucy" by scientists, lives.
http://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.htmlhttp://www.esse.ou.edu/glossary_ess.html


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Quaternary Period ( 1.6 Million years to the Present)

Pleistocene Epoch (1.6 Million to 10,000 yearsago)The modern ice age; first modern humans appear

Holocene Epoch (10,000 years ago to presentday)Began with the end of the most recent glaciation


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Skala Waktu Geologi 12 Okt 2012

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