Introduction to Quaternary Geology (MA-Modul 3223) Prof. C. Breitkreuz, SS2012, TU Freiberg

Transcription

1 Introduction to Quaternary Geology (MA-Modul 3223) Prof. C. Breitkreuz, SS2012, TU Freiberg 1. Introduction: - Relevance, and relations to other fields of geoscience - Lower stratigraphic boundary and subdivision of the Quaternary 2. The paleoclimatic evolution: - paleoclimatic proxies and controlling parameters 3. Stratigraphic methods and age dating of Quaternary processes 4. Glacials: glacial and periglacial processes on land, deposits and structures 5. Glacio-marine processes 6. Interglacials, including the Holocene, the Pleistocene-Holocene transition : one-day Field trip to Quaternary outcrops (put your name into list at Frau Klocke s office) : written test / Klausur

2 Large glaciations (Vereisungen) Glacial (Eiszeit) - Interglacial Within a Glacial: - Stadial and Interstadial East Greenland: IRD* in N Atlantic (Eldrett et al. 2007, Nature) *ice rafted debris Zachos et al. 2001

3 Paleoclimate archives isotopes Bradley 1999

4 Bradley ka 700 ka

5 18 O - Master-Proxy in: Water, Ice cores Biogene carbonates (forams) Recent forams

6 Ice Ocean PDB Cool climate (e.g.): 1. Temperature proxy: a) ocean: forams* w. high 18 O b) polar air: low 18 O, low D 2. Ice volume proxy: High volume: high marine 18 O * 18 O in a foram is controlled by water temperature and salinity, and by volume of land ice shields

7 Odd number = warm Even number = cold Oxigen isotope stages: - the first studies Marine sediment cores offshore Greenland

8 First Ocean-land correlations: e.g., marine 18 O vs. Dead Sea pollen Horowitz 1989, PPP, figure incomplete

9 30 years later Stacked marine oxygen isotope record ( PISO-1500 ) of 13 sites Channell et al. 2009, EPSL

10 Working on an ice core Thin section of ice core under polarized light

11 amrc.ssec.wisc.edu

12 Ice cores Recent data from snow (1b > 2) Delmas 1992 Greenland Ice PDB Compare scales! 18 O Master-Proxy: - In ice cores

13 Dansgaard-Oeschger-Cycles (DO), Starting with quick warming Univ. Texas The central Greenland GISP2 δ 18 O record for the past 80 kyr, interpreted as a proxy for air temperature (Grootes and Struiver, 1997). The abrupt warming events (called Dansgaard-Oeschger Interstadials) have been numbered. Also shown are the amplitudes of several events estimated from measurements of N 2 (+Ar) isotopes in trapped air (Severinghaus et al. 1998; Severinghaus and Brook, 1999; Lang et al., 1999). Delmas 1992 Age-depth models! GISP

14 Bradley 1999 Marine isotopes & temperature-sensitive forams vs. Greenland ice core *IRD-rich horizons in marine sediments in the northern Atlantic Heinrich-Layers* GRIP DO

15 Ice thickness (Univ. Washington) >> Ice coring in the Antarctic ice shield Ice core drill sites NERC

16 Petit et al Vostok ice core

17 Typical evolution of a glacial (< 500 ka): c. 100 ka, slow start, quick finish Vostok ice core After Petit et al. 1999

18 EPICA Dome C ice core: < 700 ka! Differences in orbital forcing between northern and southern hemisphere! (Milankovich cycles, see below) EPICA community members, Nature, 2004

19 North-south-polar paleoclimate correlation Epica Community Members 2006, Nature 444 MIS: Marine Isotope Stage LGM: Last Glacial Maximum EDC: Epica Dome C EDML: Epica Droning Maud Land NGRIP: N Greenland Ice core DO: Dansgaard-Oeschger-Cycle

20 Atlantic climate swing: Atlantic Meridional Overturning Circulation (MOC): DO seems to follow Antarctic warming event AIM: Antarctic Isotope Maximum A1, A2: Antarctic warming events Byrd: Bird Ice Core Methan Synchronisation Epica Community Members 2006, Nature 444 More examples of paleoclimate proxies in the next chapter!

21 What controls climate change? Variation in solar and cosmic radiation Climate-sensitive processes on Earth (volcanism, plate tectonics, human polution etc.) Complex system of positive and negative feed backs in the hydroatmosphere system (e.g., albedo of ice cover, marine gas hydrates) Bradley 1999

22 Climate forcing (Anfachung) by Milancovich-Orbital-Cycles: Excentricity 100 ka Obliquity 41 ka Precession 19, 23 ka Lozan et al July, 65 N 100 W/m 2! Model data from Vostok ice core (Petit et al. 1999)

23 * * *dominance of (Wikipedia, after Lisiecki & Raymo 2005) Stack of 57 marine benthic 18 O records (Lisiecki & Raymo 2005, Paleoceanogr.)

24 The radiation budget of the Earth s atmosphere (units in W/m 2 ) Short wave Long wave Kiehl et al. 1997, Bull-Amer-Meteor-Soc

25 Absorption of long wave radiation from the Earth surface by greenhouse gases Variation in ppm CO 2 : greenhouse effect is not linear! Short wave Long wave Gas Water vapor Carbon dioxide Contributio n (%) 36 72% 9 26% Methane 4 9% Ozone 3 7 % Mitchell 1989, Rev. Geophys.

26 Hydrocarbon emission at sea floor

27 Kvenvolden 1993 Burning gas hydrates Sampled from the sea floor

28 Kvenvolden 1993

29 3D seismic tomography of gas hydrates Hobro et al., JGR 2005 BSR = Bottom simulating reflector

30 Recent permafrost regions on the northern hemisphere Positive feedback Marine gas hydrates: negative feedback (Ehlers 1996) Kvenvolden 1993