GEOL 4010 QUATERNARY GEOLOGY

							     GEOL 4010
QUATERNARY GEOLOGY
 Instructor: Dr. Hester Jiskoot


       LECTURE 4


QUATERNARY
 ICE AGES
CAUSES OF CENOZOIC ICE AGES
                 (LAST 65 MILLION YRS)

 Himalayan uplift started ~40 million y BP
       Reduction of atmospheric CO2
        Onset monsoons

 1st Antarctic ice cap at ~33 million y BP
       permanent at 16 million y BP

 Arctic `ice cap` appears ~2.5 million y BP, due to:
       closure of Isthmus of Panama
       changed oceanic circulation

 Once ice caps formed, controlled by Milankovitch cycles
MILANKOVITCH CYCLES & GLACIATION

        Cyclic variations in the Earth's
                  eccentricity
                    axial tilt
                   precession

  Milankovitch Cycles: variations in seasonality,
  location and amount of solar energy on Earth

         contrasts between the seasons
                     eccentricity

                                  aphelion




perihelion


             0 to 5% ellipticity = (aphelion-perihelion)
                             At present 3%

                  Variations in distance Sun-Earth =
                Variations in amount of solar radiation
             axial tilt




             At present 23.5 tilt

 The more tilt the more seasonal variations

Ice Ages would occur when there is little tilt:
      TSummer = low      PWinter = high
        Precession of the equinoxes
                             at present



                             in 5250 yrs




                         in 10500 yrs
   Effective when
   combined with
    eccentricity:
15% variation in radiation
    at high latitudes
   MILANKOVITCH
      CYCLES
www.museum.state.il.us/exhibits/ice_ages/


100000 yrs




22000 yrs




41000 yrs
  ICE AGE CYCLES
     www.museum.state.il.us/exhibits/ice_ages/




Wisc. Illinoian.              Pre-Illinoian     




                    G =glaciations in midwest USA
    ICE AGE PERIODICITY


Glacial Period        ~100000 years

Interglacial period    ~10000 years
    DOWN TO EARTH AGAIN….

               So….

Several Cold Periods in the last 2.5 My


 How can we reconstruct these from
       geologic evidence?
                  STRATIGRAPHY
Stratigraphy = Study of layered rocks/deposits within a
chronostratigraphic framework

Strata = Layers                  stratification = bedding

stratum = sedimentary unit of relatively uniform composition,
 separated by discontinuities in lithological composition,
structure or texture.

Stratigraphic discontinuities visible from gradual or abrupt
changes in colour, hardness, structure, erosion lag, dielectric
properties, etc.
  ASSUMPTIONS IN STRATIGRAPHY

 Original Horizontality (sedimentary layering)

 Superposition (young over old)

 Cross-Cutting Relationships (intrusions, faults)

 Unconformities (buried erosion surfaces)

 Correlation (lateral continuity, facies setting)
          (Lithostrati-) GRAPHIC LOGGING
    15 m
                                        structures
 scale
                                                 • stratigraphy
     10                                          • sedimentary structures
                                                 • deformation structures
                                                 • bed contacts
         5                                       • colour
                                                 • fossil content

lithology                             fossils    • erratics
                                                 • lateral variations
      0
                         f     m c
             clay/silt       sand  pebbles
                 mean grain size
SEDIMENTOLOGY VS TECTONICS
Sedimentary processes (wind, water)
• lamination
• bedform morphology
• texture
• structure
• transitions relate to energy/input (abrupt/gradual) FU, CU

Tectonic processes (ice, orogenesis, gravity)
          syn-, or post- sedimentary deformation
                             or
           pre-,syn-,post-tectonic sedimentation

 Glaciotectonic dislocations disrupt stratigraphic units
       tills of one glaciation can be discontinuous
            KINETO-STRATIGRAPHY
                  (Berthelsen, 1973, 1978; Boulton, 1996)

 Focus on the structural instead of the sedimentary record


Kineto-stratigraphic zones of deposition and erosion

      1                2                      3                   4

Ice divide:      Overdeepening:         Inner margin:       Outer margin:
slight erosion   Strong erosion     advance/retreat tills   continuous till
                                    with erosion surfaces   deposition


      Extension              Ice flow              Compression
          RELATIVE AND ABSOLUTE
             DATING METHODS
1. Sidereal (calender/annual)   varves, Palaeomagnetism

2. Isotopic                     18O
                                K/Ar or Ar/Ar-method
                                Th/U
                                Fission track (U/U isotopes)

3. Radiogenic                   C14
                                Thermoluminescence (TL),
                                optical stimulated luminescence (OSL)
                                electro spin resonance (ESR)

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

5. Geomorphic

6. Correlations
   Quaternary stratigraphy               (Zagwijn, 1957)
                          2.5 My
PLEISTOCENE STAGES
Weichselian     g      g=GLACIAL       - regression
Eemian          i      i =INTERGLACIAL - transgression
Saalian         g
Holsteinian     i
Elsterian       g
Cromerian       i
                            About 750000 yr BP
Bavelian/Menapian gi
Waalian        ig
Eburonian      gi
Tiglian        ig
Praetiglian    gi
           PRAETIGLIAN

1st Pleistocene cold stage
pollen spectra resemble Weichselian
trees:Betula, Pinus, Alnus
herbs dominate: graminae, cyperae, ericacae



         UK: Red Crag formation?
        TIGLIAN =Tegelen clay
     Main Quaternary transgression
     Stratigraphic information needed
 trees: Fagus (beech)
 herbs: water fern
 fauna: warm molluscs

     Also ice wedges (cold)
UK: Ludhamian and Beestonian
     Cromer forest beds
     Baventian (IRD?)
              EBURONIAN

7 units counted
Glacial periods know from:
sediments: fluvial clasts from Baltic River System
fauna: lemming


             UK: missing
                 WAALIAN

3 units:Waalian A, B, C (WCmildw)
   pollen: Tertiary relicts



    UK: missing.
            MENAPIAN
CWC (=cold/warm/cold)
ice wedges and cryoturbation
Scandinavian erratics

              BAVELIAN
   WCWC
   vegetation succession
           UK: both missing
N-Am: PRE-ILLINOIAN (formerly Nebraskan)
                CROMERIAN
    Originally named after Cromerian Forest Beds (UK),
               which are actually of Tiglian Age

CROMERIAN I, A, II, B, III, C, IV
Letters= glacials
Numbers= interglacials

UK: fluvial aggradations of quartz-rich gravel
Glaciation Welsh Mountains
no chronological control
   ELSTERIAN COLD STAGE
Ice extent unknown: most till eroded by Saalian ice
Flint-line best preserved in Saxony (river Elster)

• Change in regional drainage (e.g. Elbe, Ice-dammed lakes)
• Incised subglacial tunnel channels + troughs
       Origin: fluvioglacial/glacial/liquefaction ???
• Late-glacial glaciolacustrine clays (up to 150 m: FU sequence)
       (e.g. Lauenburger Ton/Potklei)
    UK: Anglian Glaciation
    Thames valley = southern margin
    Norfolk: interaction Scandinavian and British ice
    5 tills but no interglacial
    N-Am: PRE-ILLINOIAN (formerly Kansan)
    HOLSTEINIAN INTERGLACIAL
Typesite= Sleswick-Holstein
Major transgression: onset by isostatic depression
Sites with Holsteinian deposits widespread

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

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

N-Am: YARMOUTH  Typesite SE Indiana
 organic deposits climate warmer and drier than Holocene
      SAALIAN COLD STAGE
 Start = nonglacial prolonged cold
 2 ice advances (Drenthe and Warthe)

 Older, Middle and Younger Saalian Till
UK: Wolstonian glaciation
typesite= 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 soils
2 major glaciations
Toronto: York Till
Hudson Bay: 4 tills
   OLDER SAALIAN ADVANCE:
PUSH MORAINES OF THE REHBURG PHASE




    From: Van der Wateren, 1995 and 1987
     EEMIAN INTERGLACIAL
Typesite = Eem river in central Netherlands
Slightly warmer than Holocene
marine deposits, vegetational history and soils


 UK: Ipswichian Interglacial
 Bobbitshole (Ipswich) and Trafalgar Square (London)
 botanical record associated with large mammals

  N-Am: SANGAMONIAN (130000-75000 BP)
   Paleosols found outside Wisconsin limit
   drier and warmer than Holocene (Newfoundland)
   Sea level-25 to +9m (San Francisco Bay and Mexico)
   Canada sea level 4-6 m above present
WEICHSELIAN COLD STAGE
Maximum ice advance in late Weichselian
Last Glacial Maximum (LGM) (22000 -18000 BP)
Younger Dryas (10800-10000 BP)
Fennoscandian ice sheet completely melted by 8500 BP


                         UK: Devensian Glaciation
                         LGM= Dimlington Stadial
                         Loch Lomond = Younger Dryas
                         Irish Sea hot debate
 N-Am: WISCONSIN
 Laurentide:
 3 glaciation centres (Labrador/Keewatin/Fox Basin)
 Cordilleran western Canada
LAURENTIDE ICE SHEET DURING LGM
RECONSTRUCTION FORMER ICE SHEETS


           Dynamics

           Processes

           Location
LAURENTIDE ICE SHEET TIME SERIES


                     • Shifting centres
                     • Shifting ice divides
                     • Number of domes


                    Changing morphology
                              &
                        ice dynamics
                              =
                       cross-cutting
                      relationships in
                     streamlined forms
            Past and future temperature trends.

                                                     < 10,000 y BP based on
                                                        deep-sea cores &
                                                        terrestrial glacial
                                                            evidence.

                                                   > 10,000 yrs, constructed
                                                     from mountain glacier
                                                       variations & other
                                                      climate-proxy data,

                                                     Projections based on
                                                     Milankovitch (Earth-
                                                      orbital) variations.

                                                      Red curve = various
                                                      greenhouse warming
                                                           scenarios
http://faculty.washington.edu/scporter/Rainierglaciers.html