Quaternary palaeoenvironments

1. Quaternary palaeoenvironments “Except for the observations made over the last 130 or so years at weather stations and on ships, our knowledge of past climates is based on records kept in sediment and ice. The task of the palaeoclimatologist is to decipher these proxies”. Wally Broecker, 1993

2. Proxy indicators of environmental change Proxy: “ (the action of) a substitute, or deputy” (OED) In palaeoenvironmental research the properties of natural archives substitute for direct measurement. Reconstruction of palaeoenvironmental information requires that these proxies be translated (qualitatively or quantitively) into environmental parameters.

3. Examples of the proxy approach Research question #1: “How warm were the summers in Arctic Canada 6 000 years ago?” Answer may be derived from various temperature-sensitive properties of lake sediments, bogs, or glaciers. Research question #2: “How frequent were typhoons in Japan in the period before records were kept?” Answer may be derived from proxies recording intense storms at sea and flooding on land.

4. What are the main kinds of proxies in Quaternary research? • glaciological • geological • historical • biological

5. Glaciological archives Ice cores: a) oxygen isotopes b) ice fabric (size and shape of ice crystals) c) trace elements (gases), and d) microparticle (dust) concentration and composition

6. Geological proxies Marine environmentsOrganics oxygen isotopesfaunal and floral componentsInorganics mineralogy and texture accumulation rates geochemistry

7. Geological proxies Terrestrial environmentsglacial deposits periglacial features palaeo-shorelines aeolian deposits (dunes, loess) lacustrine deposits palaeosols speleothems

8. Historical proxies Written records of paraclimatic phenomenae.g. Hudson Bay factors’ journals record freeze-up and breakup of Arctic rivers; ships’ logs record tropical storm frequency (e.g. logs of Manila- Mazatlan voyages of Spanish galleons); whalers’ catch records locate edge of sea ice in Antarctica; Norse sagas describe subpolar landscapes (e.g. Greenland); arrival of spring recorded in journals and diaries (phenological records); size and date of crop harvest recorded by merchants, etc..

9. ‘Historical’ proxies Oral traditionse.g. Haida stories of flooding of Hecate Strait (but native traditions tend to ‘float’ in time) Imagerye.g. Breughel’s “Hunters in the Snow” records LIA winters in N. Europe, cave art in SW France records local game animals 20-30 ka.

10. European temperature records only begin in C18th - but how cold/warm were previous years?

11. Single proxies: French grape harvest dates (AD 1484 -1880)

12. Multiple proxies: phenological observations Phenology - study of the timing of natural events e.g. Robert Marsham (1707-1797) kept a journal on 27 “indications of Spring” on his estate in Norfolk (England) from 1736 until his death. Indicators included flowering of spring bulbs, leafing-out of shrubs and trees, appearance of migratory birds and butterflies, etc.

13. Winter of 1740 in eastern England For example, from Marsham’s journals we read that the first few months of 1740 were so cold that: … the gorse and heather died, the rabbits starved in their warrens, the beer froze on the dinner table, and the piss in his chamber pot “froze to a cake”. In London the River Thames froze ….

14. Biological proxies ecological processes taphonomic processes Physical environment (esp. climate) biological community fossil community Reconstruction (palaeoecological methods)

15. Factors determining the utility of organisms as biological proxies Species-related factors 1. Is the species abundant? 2. Is it (or are its parts) readily identifiable? 3. Is the abundance of the organism readily determinable from its fossil components?

16. Bio-proxies Plant:1 trunk 102 cones* 103 seeds* 103 leaves* 106 pollen grains* Vertebrate:1 skull 101 ribs 101 vertebrae 102 scales *annual production

17. 1 spruce trunk = 1 tree 1 diatom frustule = 1 diatom 1 articulated shell = 1 clam 1 skull = 1 mammoth 1 articulated skeleton = 1 fish 2 spruce cones = ? 20 fish vertebrae = ? 40 fish scales = ? 200 spruce seeds = ? 2000 spruce pollen grains = ? Estimates of absolute abundance possible Estimates of relative abundance possible Determining organism abundance from body parts

18. Factors determining the utility of organisms as biological proxies Environmental factors 1. Is the species abundance primarily controlled by environmental factors? 2. Is the relationship between abundance and environment known or readily determined?

19. Factors determining the utility of organisms as biological proxies Taphonomic factors 1. Does the organism (or ecological community) survive post-mortem diagenesis? 2. What changes take place pre-burial? 3. What changes take place post-burial? *diagenesis: processes affecting sediments at temperatures and pressures characteristic of the Earth’s surface.

20. Factors determining the utility of organisms as biological proxies Preservation factors ANATOMY Hard parts? YESNO YES clams jellyfish HABITAT Rapid burial? birds butterflies NO

21. Live and dead assemblages of shelly invertebrates in the main tidal channel, Mugu Lagoon, California 1. Sanguinolaria nuttalli 2. Cryptomya californica 3. Dendraster excentricus 4. Diplodonta orbella 5. Olivella plicata 6. Chione californiensis 7. Spisula dolabriformis 8. Nassarius fossatus 9. Lunatia lewisii 10. Polinices reclusianus Relative abundance 1 2 3 4 5 6 7 8 9 10

22. Taphonomic stages in the preservation of a modern oyster community Stage A B C # phyla 9 7 7 # species 80 45 18 % preservation 100 56 23 A = original community; B = all hard parts preserved (e.g. late Quaternary “subfossils”). These are mainly molluscs and other species with hard skeletons ; C = aragonitic, calcitic and siliceous skeletons lost (e.g. mid-Tertiary sediments)

23. Preservation potential of macrofauna, Baffin Island fjords and continental shelf Fjords Nearshore Inner shelf Outer shelf 217 197 126 # genera 112 many fossils no fossils few fossils Aitken, A.E. 1990. Fossilization potential of Arctic fjord and continental shelf benthic macrofaunas. In: Dowdeswell, J.A. and Scourse, J.D. (eds.) Glacimarine Environments: Processes and Sediments. Geological Society Special Publication No. 53: pp. 155-176.

24. Differential preservation by habitat, Baffin Island fjords and continental shelf Fjords Nearshore Inner shelf Outer shelf Quaternary fossils no fossils Aitken, A.E. 1990. Fossilization potential of Arctic fjord and continental shelf benthic macrofaunas. In: Dowdeswell, J.A. and Scourse, J.D. (eds.) Glacimarine Environments: Processes and Sediments. Geological Society Special Publication No. 53: pp. 155-176.

25. Differential preservation of trophic categories, Baffin Island fjords and continental shelf Modern community Quaternary sediments 210 genera 36 genera Aitken, A.E. 1990. Fossilization potential of Arctic fjord and continental shelf benthic macrofaunas. In: Dowdeswell, J.A. and Scourse, J.D. (eds.) Glacimarine Environments: Processes and Sediments. Geological Society Special Publication No. 53: pp. 155-176.

26. Environmental controls on organic preservation 1. Ambient temperature - fossils tend to be better preserved at low temperatures. e.g. at water T>15°C fish carcasses float -> scavenged -> bones scattered 2. Oxygenation - oxidation may destroy organic materials; anoxic water reduces scavenger activity 3. Water status - some organic material degrades when dry (see #2 above) 4. pH - acidic porewaters may destroy some organic materials.

27. Aeolian transportation Depositional shadows (90% of total production) needle/seed shadow pollen shadow cone shadow 500 m? 40m? 5m? parts may suffer mild abrasion Result = homogenization of fossil assemblages

28. Fluvial transportation and redeposition Experiments with sheep and coyote bones in small streams Not movedMoved gradually Moved immediately (traction)(saltation/suspension) skull lower jaw femur tibia humerus pelvis ribs vertebrae sternum finger/toe bones these parts may suffer severe abrasion Result = homogenization of species? sorting by body part?

29. Lake and bog sampling sites Habitat representation? alpine lakes bogs and lakes on floodplains valley sideslopes

30. Common biological proxies Terrestrial organisms plants (macrofossils, pollen, tree rings) fauna (esp. insects, molluscs and mammals) Aquatic organisms diatoms, coccolithophores foraminifers, ostracodes, corals chironimids, molluscs, fish

31. Reconstructing palaeoenvironments: temporal calibration of proxy Past P.D. warm cold calibration period Prehistoric Historic instrumental record (e.g. summer T) proxy record (e.g. width of tree ring) inferred summer T

32. Proxy calibration (spatial) e.g. single species morphology % forams coiled to right samples e.g. cold warm Present-day environmental gradient

33. Proxy calibration (spatial) e.g. species distributions sp. C sp. B Relative abundance sp. A samples e.g. cold warm Present-day environmental gradient

34. Transfer functions Quantitative reconstructionse.g. summer T(°C) = 12.5 + 1.7[ring] + 2.09[ring]2 summer T(°C) = 12.5 + 1.66(right-coiled) summer T (°C) = f(abundance species A,B,C)

35. Checking the reconstruction • Replication: does the same proxy produce equivalent results at another site? • Validation: do several proxies produce equivalent results? • Complementary information: do alternative proxies provide useful supplementary data?

36. Analyse archival recorde.g.peat bog Depth geochemical proxy sp. ABC abundance

37. Reconstruction from transfer function geochemical proxy record dominantspecies reconstructed T Past P.D.

38. Replicationof results at local, regional, or global scales

39. Checking with multiproxies: Deserted Lake , VI Vibracoring DL in foreground; Hisnit Inlet (Nootka Sd.) in background

40. Validation from 4 proxies Hutchinson et al., 2000. The Holocene10, 429-439

41. Elk Lake, Itasca Park, Minn.

42. Multiproxy validation and complementarity :Elk Lake: Minn. - pollen, lake geochemistry and diatoms