Pleistocene Glaciations

Jarðsaga 2

Ólafur Ingólfsson

Háskóli Íslands

Classical glacial stratigraphy

Until the 1970's it was believed that 4-5 Pleistoceneglacial-interglacial cycles had occurred. This was based on the classical stratigraphy of Europe and N America.

KansanElsterian

SangamonianEemian

Holocene interglacialHolocene interglacial

AftonianCromerian complex

YarmothianHolsteinian

IllinoianSaalian

Wisconsinan glacialWeichselian glacial

NW Europe N America Age10-0 ka

120-10 ka

130-120 ka

300-130 ka

430-300 ka

560-430 ka

630-560 ka

Quaternary stratigraphyAfter (Zagwijn, 1957)

Weichselian gEemian iSaalian gHolsteinian iElsterian gCromerian i

PLEISTOCENE STAGES

g=GLACIAL - regressioni =INTERGLACIAL - transgression

About 750000 yr BPBavelian/Menapian giWaalian igEburonian giTiglian igPraetiglian gi

ICE AGE CYCLESwww.museum.state.il.us/exhibits/ice_ages/

G =glaciations

Saalian.

Weichselian

Pre-Saalian

Classicalstratigraphicdivision of the

Quaternary

From: Lowe & Walker1998: ReconstructingQuaternary Environments. Harlow, Longman.

>30 glacial-interglacial

cycles

We now know from deepsea sediments and ter-restrial stratigraphythat at least 8 glacial-interglacial cycles have occurred for the past 800 ka, and probably >30 such cycles since late Pliocene.

Stratigraphy and environments of older glaciations poorly known...

The information is often from mining pits or boreholes.Clay mine at Jaroszów, southwestern Poland. Tertiary clay (gray) is

overlain by glacial sediments (brown). Such geology is typical through-out much of central Europe between the Baltic Sea and alpine mountains. Photo

date 8/93; ©; by J.S. Aber.

LITHOSTRATIGRAPHIC LOGGING

sandf m c

pebbles

fossils

15 m

scale• stratigraphy

• sedimentary structures

• deformation structures

• bed contacts

• colour

• fossil content

• erratics

• lateral variations

structures

10

5

lithology

0

clay/silt

mean grain size

Sea level signatures

Isostatic signature: The weightof kilometers of ice depressescontinental crust. Localized sealevel changes alters coastlines significantly. Relative sea level change due to loading and unloading.

Rebound of crust after the ice melts can takethousands of years. Therefore: deglaciation signaled by transgression

Eustatic sea level controlled by volume of ice

At height of last interglacial, thesea stood 5-7 m higher than today. At the Last Glacial Maximum(LGM) global sea level was at -120 m. The figure shows oxygen isotopes and sea level changes for the last 140 ka, from late in the previous glacial period to the present.

Increased glaciation means fallingsea levels, deglaciation means rising sea levels and transgressions

Composite stratigraphy, Kapp Ekholm, Svalbard

The stratigraphy shows four till units, deposited by glaciers during glaciations. They are sparated by four coarsening up-wards marine-littoral units, showing de-glaciation and marine regression.

RELATIVE AND ABSOLUTE DATING METHODS

1. Sidereal (calender/annual) varves, Tree-rings

2. Isotopic δ18OK/Ar or Ar/Ar-methodTh/UFission track (U/U isotopes)

3. Radiogenic 14C Thermoluminescence (TL), optical stimulated luminescence (OSL) electro spin resonance (ESR)

4. Chemical/biological pollen, amino-acid, lichenometry, tephra

5. Geomorphic Weathering, relative position

6. Correlations Lithostratigraphy, magnetostratigraphy

Kapp Ekholm chronology based on 14C, TL/OSL and amino-acid datings

Stratigraphic data used for constructing time-distance diagrams for glacial oscillations

PRAETIGLIAN1st Pleistocene cold stage (2,4 MY)• pollen spectra resemble Weichselian• trees: Betula, Pinus, Alnus• herbs and grasses dominate pollen diagrams

The onset of true cold climatesin the Praetiglian caused a marked change in depositionalstyle with the input of graveland sand; glaciation may already have been established in the Alps; ice-rafted blocks occur in Rhine sediments.

TIGLIAN =Tegelen clay

• Major Quaternary transgression• Poorly known environments, more

stratigraphic information needed trees: Fagus (beech)

herbs: water fernfauna: warm molluscs

Also ice wedges (cold)

CROMERIAN (~500 ka) Complex Originally named after Cromerian Forest Beds (UK), which

are actually of Tiglian Age

CROMERIAN I, A, II, B, III, C, IVLetters = glacialsNumbers = interglacials

We know that there was a continental ice sheet over NW Europe during the Cromerian...

ELSTERIAN COLD STAGE(OIS 12, ~400-500 ka BP)

Ice extent unknown: most till eroded by Saalian ice

• Change in regional drainage (e.g. Elbe, Ice-dammed lakes)

• Incised subglacial tunnel channels + troughsOrigin: fluvioglacial/glacial/liquefaction ???

• Late-glacial glaciolacustrine clays (up to 150 m)

UK: Anglian GlaciationThames valley = southern marginNorfolk: interaction Scandinavian and British ice5 tills but no interglacialN-Am: PRE-ILLINOIAN (formerly Kansan)

The Elsterianmiddle

Pleistocene glaciation

We know that continental ice sheets advancedonto lowland NW Europe during the Elsterianglaciation. stages. The areas overridden by the ice were subjected to total landscape remodelling.

Kansan glaciation landscape

View over glaciated landscape, Wabaunsee County, northeastern Kansas. Erratic boulders of Sioux Quartziteare scattered in the foreground. The glaciation of Kansas took place >0.5 MY ago. Photo date 10/89; © by J.S. Aber.

HOLSTEINIAN INTERGLACIALTypesite= Sleswick-HolsteinMajor transgression: onset by isostatic depressionSites with Holsteinian deposits widespread

Fossil soils, lacustrine and organic strata (diatoms),pollen

UK: Hoxnian Interglacialtypesite= Hoxne (Suffolk)Vegetational succession similar to the ‘continental’

N-Am: YARMOUTH Typesite SE Indiana organic deposits climate warmer and drier than Holocene

SAALIAN COLD STAGEStart = nonglacial prolonged cold2 ice advances (Drenthe and Warthe)MOIS stages 6-9 (?)Older, Middle and Younger Saalian Till

UK: Wolstonian glaciationtypesite= Wolston on Avon (Warwickshire)Limited ice extent compared to continent (why?)No contact between British and Scandinavian Ice sheets?

N-Am: ILLINOIAN Typesite Illinois: 8 tills/4 fossil soils2 major glaciationsToronto: York Till Hudson Bay: 4 tills

Maximum extent of the glaciation during theSaalian (late Middle Pleistocene - Marine Isotope Stage 6 or ?8).

The SaalianGlaciation

Glaciation during theSaalian had comparableeffects to those seenin the prevois ElsterianGlaciation, causingmajor drainagediversion and landscape remodelling. Major ice-pushed ridges in the Netherlands and Germany forced the Rhine to follow a more southerly course.

Saalian in NW Europe

OLDER SAALIAN ADVANCE: PUSH MORAINES OF THE REHBURG PHASE

From: Van der Wateren, 1995 and 1987

Saalian meltwater channel

Subglacial meltwater channel (N-type) of Saalianage in Welzow Süd open-cast mine, Eastern Germany (Photo by J.A. Piotrowski)

Saalian in Eurasia

The Saalian glaciation was the most extensive glaciationrecorded in Eurasia, particularily in the high arctic.

Europe 150 ka BP

The GreatGlaciation

The Illinoian or Great glaciation was the bigone in N America, covering all but the highestsummits of the Rockies, and burying Canada and the northern United States below ice.

The last interglacial-glacial cycle

We know very little about older glacial-interglacial cycles, and information on anything older than the second before the last (the Saalian) glaciation is very fragmentary.

The Eemian was:• Oxygen isotope stage 5 (130,000-75,000 BP) or just substage 5e (130,000-115,000 BP)

• Rapid warming at onset. 2-3°C warmer during theclimate optimum than Holocene. Mid-latitudes slightly warmer than today, high latitudes considerably warmer.

• Globally, ice volumes were smaller than during Holocene

• Global sea levels were ~2-5 m higher than any time during the Holocene

• Faunal and floral zones were considerably displacedtowards North compared to Holocene. Widespread paleosols

• Gradual cooling

The Eemian-Sangamon interglacial

Ice-core, marine andand paleobotanicaldata show Eemian

warmer than Holocene

Ice core records suggest warm Eemian on Greenland

Greenland Inland Icesmaller than presentduring the Eemian –contributed to high global sea levels

Biostratigraphicalrecords from NE Greenland suggestEemian was con-siderably warmer than Holocene. Birch grew on 72°N

Eemian N America

Eemian-Sangamon coastal waters considerably warmerthan during Holocene – particularily at high latitudes. High arctic tundra areas considerably reduced compared to Holocene – tree line much further north,

Eemian N America

Birch and picea (“greni”) much further north than duringHolocene. Birch forest in the arctic. Warm and moist airmasses penetrated the N American continent.

Eemian Ocean warmer than present

The difference between modern and estimatedFebruary SST (in °C) during the Eemian, 120 ka BP.

High Eemian sealevel left Scandi-navia an island...

References used for this presentationStanley, Earth System History.Benn, DI & Evans, DJA (1998) Glaciers & Glaciation. Arnold, London.Clark & Mix (2002) Ice sheets & sea level of the Last Glacial Maximum. Quaternary Science Reviews. 21, 1-7.Lowe, JJ & Walker, MJC (1997) Reconstructing Quaternary Environments. 2nd edition. Longman, London.Siegert, MJ (2001) Ice sheets & Late Quaternary Environmental Change. Wiley, London.Svendsen et al. 2004: Late Quaternary ice sheet history of northern Eurasia. Quaternary Science Reviews 23, 1229-1271.

http://www.joiscience.org/USSSP/Pubs/GreatHits/PDFs/Rhythms/Linsley.pdf

http://www.pbs.org/wgbh/nova/vinson/ice-10.html#fea_top

http://museum.state.il.us/exhibits/ice_ages/index.html

http://pubs.acs.org/hotartcl/est/99/apr/learn.html#0043-99scho1.ev

http://www.gps.caltech.edu/~jess/Adkins5eNature.pdf

http://www.ngdc.noaa.gov/paleo/globalwarming/interglacial.html

http://climchange.cr.usgs.gov/info/lite/results.html

http://www-qpg.geog.cam.ac.uk/research/nweurorivers/