EESC 2200The Solid Earth System

Igneous RocksAnd Relative Time

24 Sep 08

Continental Tectonics

Homework 2:Due Wednesday

Relative Frequency of Rock Types

A. Crust B. Surface

ES101--Lect 8

Magma chemistryTwo main classes

mafic magmas + rocksma - fic

magnesium + iron (Ferrous) rich

ES101--Lect 8

felsic magmas + rocksfel - sic

Feldspar and silica rich

OR:

ES101--Lect 8

felsic ->intermediate-> mafic

light dark

large ions small ions(K, Na) (Mg, Fe)

more Si (>60%) less Si (≤ 50%)

ES101--Lect 8

felsic ->intermediate-> mafic

light dark

large cations small cations(K, Na) (Mg, Fe)

more Si (>60%) less Si (≤ 50%)

cooler magmas hotter magmas

dense mineralslight minerals

which more explosive? minerals?

ES101--Lect 8

QuartzKSparPlagSparMicasAmph.PyroxeneOlivine

Felsic Intermediate MaficUltra-mafic

ES101--Lect 8

QuartzKSparPlagSparMicasAmph.PyroxeneOlivine

Felsic Intermediate MaficUltra-mafic

Granite Gabbro Perid-otite

Diorite

ES101--Lect 8

Granite Diorite Gabbro

felsic mafic

ES101--Lect 8

Felsic Intermediate Mafic

Granite GabbroDiorite

coar

se

Rhyolite BasaltAndesite

fine

rock slides

Mafic Igneous Rocks

Gabbro (coarse) Basalt (fine)

Intermediate Igneous Rocks

Diorite (coarse) Andesite (fine)

Granite (coarse) Rhyolite (fine)

Felsic Igneous Rocks

Classifying igneous rocks bycomposition and texture

ES101-Lect9

Ridges: Mantle undergoes decompression melting --->>> Basalts (dry)

basalt = mantle melt ("blood of the Earth")

1300°C

ES101-Lect9

Depth

All Solid

AllLiqPartial

Melting

Mantle Melting 1100 °C

Temperature1300°C

LowerPressure!!

ES101-Lect9

water --> mantle wedge, --> basalt arc volcanism...

ES101-Lect9

T

Wet melting

1100˚C800˚C

you are here

H2O -- Lowers Melting Point

Depth

ES101-Lect9

basalticmagma

Olivine Olivine+Pyroxene+ Ca-f'spar

andesiticmagma

cooling

basaltic melts -> andesite melts

ES101-Lect9

Mt. St. Helens

basaltmagma

Crust

Mantle

wetfelsicmagma

H2O

H2O

ES101--Lect 8

Volcanic/Extrusive Rockscool fast, fine-grained

ES101--Lect 8

magma also cools under ground......

ES101--Lect 8

Plutonic/Intrusive Rockscool slowly, coarse-grained

ES101--Lect 8

ES101--Lect 8

ES101--Lect 8Stephen Marshak

Dike

ES101--Lect 8Paul Hoffmann

1) Relative ages

Geochronology Outline:

2. Absolute Radiometric Ages

Geologic Time

How do we determine age in the geological record?

Principles of Geochronology

Go out to the field. Observations yield relative age.

Chapter 12: Deep Time: How Old Is Old? Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak

Relative AgesRelative Ages Logical tools are useful for defining relative age.Logical tools are useful for defining relative age.

Principle of Principle of uniformitarianismuniformitarianism.. Principle of superposition.Principle of superposition. Principle of original horizontality.Principle of original horizontality. Principle of original continuity.Principle of original continuity. Principle of cross-cutting relationships.Principle of cross-cutting relationships. Principle of inclusions.Principle of inclusions. Principle of baked contacts.Principle of baked contacts.

Chapter 12: Deep Time: How Old Is Old? Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak

Geologic TimeGeologic Time Uniformitarianism Uniformitarianism –– The present is key to the past. The present is key to the past.

Physical processes that we observe today operated in thePhysical processes that we observe today operated in thesame way in the geological past.same way in the geological past.

Modern processes help us understand ancient events inModern processes help us understand ancient events inthe rock record. the rock record.

Law of Superposition

Each layer of rock is older thanthe layer above it and youngerthan the rock layer below it.

Nicolaus Steno, a Danish anatomist, geologist, and priest (1636 - 1686)

Chapter 12: Deep Time: How Old Is Old? Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak

Relative AgeRelative Age Horizontality and continuity.Horizontality and continuity.

Strata often form laterally extensive horizontal sheets.Strata often form laterally extensive horizontal sheets. Subsequent erosion dissects once-continuous layers.Subsequent erosion dissects once-continuous layers. Flat-lying rock layers are unlikely to have been disturbed.Flat-lying rock layers are unlikely to have been disturbed.

Law of Cross-cutting Relationships

A fault or dike that cuts throughanother body of rock must beyounger than the rock it cuts

Scotsman James Hutton (1726-1797)

Law of Inclusions

If a rock body (Rock B) containsfragments of another rock body (RockA), it must be younger than thefragments of rock it contains.

James Hutton

Chapter 12: Deep Time: How Old Is Old? Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak

Relative AgeRelative Age Baked contacts.Baked contacts.

Thermal metamorphism occurs when country rock isThermal metamorphism occurs when country rock isinvaded by a plutonic igneous intrusion.invaded by a plutonic igneous intrusion.

The baked rock must have been there first (it is older).The baked rock must have been there first (it is older).

Law of Faunal Successions

Fossils in rock layers appeared in apredictable sequence, within a discreteperiod of time.

William Smith

Chapter 12: Deep Time: How Old Is Old? Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak

UnconformitiesUnconformities An unconformity is a time gap in the rock record.An unconformity is a time gap in the rock record.

NondepositionNondeposition.. Erosion.Erosion.

Chapter 12: Deep Time: How Old Is Old? Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak

Relative AgeRelative Age Determining Determining relativerelative ages empowers geologists to ages empowers geologists to

easily unravel complicated geologic histories.easily unravel complicated geologic histories.

Images of Siccar point outcrop fromhttp://www.wwnorton.com/college/geo/earth2/content/index/animations.asp

James Hutton (1726-1797)

“... we find no vestige of a beginning,–no prospect of an end.”

Winchester, S., 2001, The map that changed the world: William Smith and the birth of modern geology, HarperCollins.

1801

Famennian

Givetian

Eifelian

Lochkovian

Pragian

Frasnian

Emsian

Ludfordian

Gorstian

Homerian

Sheinwoodian

Telychian

Aeronian

Rhuddanian

P h

a n

e r

o z

o i c

P a

l e

o z o

i c

Pridoli

Ludlow

Wenlock

Llandovery

Upper

Middle

Lower

Devonia

n

411.2 ±2.8

416.0 ±2.8

422.9 ±2.5

428.2 ±2.3

Lopingian

Guadalupian

Cisuralian

Upper

Upper

Middle

Middle

Lower

Lower

Upper

Upper

Middle

Middle

Lower

Lower

P h

a n

e r

o z

o i c

P a

l e

o z o

i c

M e

s o

z o

i c

Carb

onifero

us

Perm

ian

Jura

ssic

Triassic

150.8 ±4.0

155.7 ±4.0

161.2 ±4.0

164.7 ±4.0

167.7 ±3.5

171.6 ±3.0

175.6 ±2.0

183.0 ±1.5

189.6 ±1.5

196.5 ±1.0

199.6 ±0.6

203.6 ±1.5

216.5 ±2.0

228.0 ±2.0

237.0 ±2.0

245.0 ±1.5

249.7 ±0.7

251.0 ±0.4

318.1 ±1.3

260.4 ±0.7

253.8 ±0.7

265.8 ±0.7

268.0 ±0.7

270.6 ±0.7

275.6 ±0.7

284.4 ±0.7

294.6 ±0.8

299.0 ±0.8

303.9 ±0.9

306.5 ±1.0

311.7 ±1.1

Tithonian

Kimmeridgian

Oxfordian

Callovian

Bajocian

Bathonian

Aalenian

Toarcian

Pliensbachian

Sinemurian

Hettangian

Rhaetian

Norian

Carnian

Ladinian

Anisian

Olenekian

Induan

Changhsingian

Wuchiapingian

Capitanian

Wordian

Roadian

Kungurian

Artinskian

Sakmarian

Asselian

Gzhelian

Kasimovian

Moscovian

Bashkirian

Serpukhovian

Visean

Tournaisian

Pe

nn

-sylv

an

ian

Mis

sis

-sip

pia

n

359.2 ±2.5

345.3 ±2.1

326.4 ±1.6

374.5 ±2.6

385.3 ±2.6

391.8 ±2.7

397.5 ±2.7

407.0 ±2.8

443.7 ±1.5

436.0 ±1.9

439.0 ±1.8

418.7 ±2.7

Ediacaran

Cryogenian

Tonian

Stenian

Ectasian

Calymmian

Statherian

Orosirian

Rhyacian

Siderian

Neo-

proterozoic

Neoarchean

Mesoarchean

Paleoarchean

Eoarchean

Meso-

proterozoic

Paleo-

proterozoic

Arc

hean

Pro

tero

zoic

P r

e c

a m

b r

i a

n

~630

850

1000

1200

1400

1600

1800

2050

2300

2500

2800

3200

3600

Upper

Middle

Lower

Selandian

Tortonian

Serravallian

Langhian

Burdigalian

Aquitanian

Ypresian

Chattian

Rupelian

Priabonian

Danian

Thanetian

Bartonian

Lutetian

Campanian

Santonian

Turonian

Coniacian

Albian

Aptian

Berriasian

Barremian

Valanginian

Hauterivian

Maastrichtian

Cenomanian

Piacenzian

Messinian

Zanclean

Gelasian

P h

a n

e r

o z

o i c C

e n

o z

o i c

M e

s o

z o

i c

1.806

0.126

0.781

2.588

5.332

7.246

11.608

13.65

15.97

20.43

70.6 ±0.6

65.5 ±0.3

83.5 ±0.7

85.8 ±0.7

89.3 ±1.0

93.5 ±0.8

40.4 ±0.2

37.2 ±0.1

33.9 ±0.1

28.4 ±0.1

23.03

48.6 ±0.2

55.8 ±0.2

58.7 ±0.2

61.7 ±0.2

99.6 ±0.9

112.0 ±1.0

125.0 ±1.0

130.0 ±1.5

136.4 ±2.0

140.2 ±3.0

145.5 ±4.0

Cre

taceous

Pale

ogene

Neogene

Syste

mP

eriod

Eonoth

em

Eon

Era

them

Era

Sta

ge

Age

Age

Ma

GS

SP

Epoch

Series

Eonoth

em

Eon

Era

them

Era

Syste

m

Sta

ge

Age

Age

Ma

GS

SP

Epoch

Series

Period

Eonoth

em

Eon

Era

them

Era

Age

Ma

GS

SP

GS

SA

Syste

mP

eriod

Eonoth

em

Eon

Era

Sta

ge

Age

Age

Ma

GS

SP

Epoch

Series

Period

3.600

Oligocene

Eocene

Paleocene

Pliocene

Miocene

Pleistocene

Upper

Lower

Holocene0.0118

INTERNATIONAL STRATIGRAPHIC CHARTInternational Commission on Stratigraphy

421.3 ±2.6

426.2 ±2.4

Tremadocian

Darriwilian

Hirnantian

Paibian

Upper

Middle

Lower

Series 3

Stage 3

Stage 2

Stage 1

Stage 5

Stage 6

Stage 7

Stage 9

Stage 10

Stage 2

Stage 3

Stage 5

Stage 6

Stage 4Series 2

Series 1

Furongian

Cam

brian

Ord

ovic

ian

~ 503.0 *

~ 506.5 *

~ 510.0 *

~ 517.0 *

~ 521.0 *

~ 534.6 *

460.9 ±1.6

471.8 ±1.6

488.3 ±1.7

~ 492.0 *

~ 496.0 *

501.0 ± 2.0

542.0 ±1.0

455.8 ±1.6

445.6 ±1.5

468.1 ±1.6

478.6 ±1.7

Lower limit is

not defined

Silu

rian

* proposed by ICS

Era

them

Syste

m

542359.2 ±2.5145.5 ±4.0

Qu

ate

rna

ry *

ICS

Copyright © 2006 International Commission on Stratigraphy

Subdivisions of the global geologic record are formally defined by their lower boundary. Each unitof the Phanerozoic (~542 Ma to Present) and thebase of Ediacaran are defined by a basal GlobalStandard Section and Point (GSSP ), whereasPrecambrian units are formally subdivided byabsolute age (Global Standard Stratigraphic Age,GSSA). Details of each GSSP are posted on theICS website (www.stratigraphy.org). International chronostratigraphic units, rank,names and formal status are approved by theInternational Commission on Stratigraphy (ICS)and ratified by the International Union of GeologicalSciences (IUGS). Numerical ages of the unit boundaries in thePhanerozoic are subject to revision. Some stageswithin the Ordovician and Cambrian will be formallynamed upon international agreement on their GSSPlimits. Most sub-Series boundaries (e.g., Middleand Upper Aptian) are not formally defined. Colors are according to the Commission for theGeological Map of the World (www.cgmw.org). The listed numerical ages are from 'A GeologicTime Scale 2004', by F.M. Gradstein, J.G. Ogg,A.G. Smith, et al. (2004; Cambridge University Press).

This chart was drafted by Gabi Ogg. Intra Cambrian unit ageswith * are informal, and awaiting ratified definitions.