Using Soils to Reconstruct Climate

1. Using Soils to Reconstruct Climate Dr. Rolfe D. Mandel, Executive Director Odyssey Research Program Kansas Geological Survey University of Kansas

2. Five Soil Forming Factors • Climatic Factor • Biotic Factor • Topographic Factor • Parent Material • Time Factor

3. When using soils to reconstruct climate, it is useful to consider the concept of “pedogenic pathways.” A pedogenic pathway is a set of pedogenic processes leading to a given soil morphology. Soils in different bio-climatic regions follow different pedogenic pathways.

4. A good way to understand the relationship between bio-climates and pedogenic pathways is to consider modern analogs.

5. Pedogenic pathways in the modern grasslands of the dry-subhumid to semi-arid Great Plains. • Accumulation of organic matter and other plant nutrients in the A horizon. The organic carbon content and thickness of the A horizon generally decreases as mean annual precipitation decreases. • Accumulation of calcium carbonate in the subsoil.

8. Tallgrass prairie in the Flint Hills of eastern Kansas Mean Annual Precipitation: 26-28 inches

10. Mixed grass prairie on the High Plains of central Kansas Mean Annual Precipitation: 22-24 inches

11. Short grass prairie on the High Plains of northwestern Kansas Mean Annual Precipitation: 17-19 inches

12. Short grass prairie on the High Plains of southwestern Kansas Mean Annual Precipitation: 11-13 inches

13. Pedogenic pathways in moist sub-humid to humid coniferous forests of North America. • Podzolization – A process that involves a pronounced downward translocation of iron, aluminum, and organic matter to form a silica-enriched eluvial E horizon above a spodic or Bt horizon enriched in some combination of Fe, Al, and organic matter (Birkeland, 1999:108). • Thin A horizon. • Thick E horizons with low organic carbon, Fe, Al, and clay content • Thick B horizons with high Fe, Al, and OM content

14. Southern Pine forest of SE Texas

15. Alfisol

17. Pedogenic pathways in tropical climates. • Evolution of Oxisolic or lateritic profiles – Thick (meters), deeply weathered profiles composed of highly weathered material (Birkeland, 1999:121). Characterized by: • Massive enrichment of Fe, Al, or both, and associated oxide, hydroxide, and oxyhydoxide minerals. • Massive depletion of silicates (few original minerals are left) • Extensive depletion of bases • Formation of 1:1 layer clay minerals, especially kaolinite • Part of the profile may harden irreversibly on drying (laterite)

18. Oxisol in Hawaii

20. Oxisol in Brazil

21. Laterite in Brazil

22. In soil science, paleosols are defined as soils that formed under past environmental conditions; the chemical and physical characteristics of paleosols are not products of the modern bio-climate. There are three types of pleosols: • Relict paleosol – at the surface • Buried paleosols • Exhumed paleosols

25. Buried Soils Buried soils represent previous land surfaces (landscapes) that were stable for long enough periods to develop recognizable soil profile characteristics.

28. 20,080 ± 560 32,850 ± 530 13,960±150

31. 2003 Excavation in Lower Mammoth/Camel Level

32. Lower Mammoth/Camel Bone Level, June 2003

33. 12,215 ± 35

34. 9240±70 9750±70 10,370±20 Folsom Component Clovis Component 10,950±60 12,215±35 14SN105, Area A Pre-Clovis Component ?

35. The following fossils may be preserved in soils and can provide valuable information about climate change: Phytoliths Gastropods There is almost always some organic carbon preserved in soils – Stable carbon isotope (d13C) analysis.

36. Phytolith = “Plant Stone” • Particles of hydrated silica formed in living plants • Plant absorbs soluble silica from groundwater, deposited as solid SiO2 in cell walls, cell interiors, and intracellular spaces

37. Why do plants produce phytoliths? • Structural functions: silica provides plant rigidity • Physiological functions: lessens effects of heavy metals • Protective functions: against herbivores, insects, pathogenic fungi

38. Grass phytoliths are: abundant, durable, morphologically different, taxonomically identifiable… Excellent for reconstructing paleoenvironments, including climate!

39. Major grass subfamilies: • Chloridoideae: short-grass prairie, C4 • Saddle-shaped • Blue grama and Buffalo Grass • Panicoideae: tall-grass prairie, C4 • Bilobate and cross-shaped • Big Bluestem, Indian Grass • Pooideae: northern prairie, C3 • Wavy, trapezoidal • Needle grasses, Western Wheatgrass

40. Some diagnostic trees & shrubs Celtis occidentalis (Hackberry) Diagnostic seed covering of sedges

41. Stable Isotope Geochemistry • Stable Carbon Isotopes in Soil Organic Matter • Stable Carbon and Oxygen Isotopes in Soil Inorganic Carbon • Oxygen Isotopes in Faunal Remains

42. From Koch, P.L., 1998, Isotopic Reconstruction of Past Continental Environments: Ann. Rev. Earth Planet. Sci. 26:573-615. Stable Carbon Isotope Analysis • SOM contains 13C/12C isotope ratio that reflect the photosynthetic pathways of C3 and C4 plant communities • The δ13C value: the difference between the 13C/12C ratio and a known standard • expressed in ‰ • C3 values range from -32‰ to -22‰ • C4 values range from -17‰ to -9‰

43. δ13C value differences trees (C3) vs. grasses (C4) C-4 C-3 CO2 Photosynthesis Photosynthesis δ13C= -26 to - 22 δ13C= -16 to -12 -26 -24 -22 -20 -18 -16 -14 -12 Soil Organic Matter

44. Gastrocopta contracta Discus whitneyi (2.4 mm) Gastrocopta contracta Carychium exiguum Land Snails Discus whitneyi and Gastrcopta contracta are typical of moist, woodland setting. Carychium exiguum demands a moist environment and is common near springs or seeps.

45. 9240±70 9750±70 10,370±20 Folsom Component Clovis Component 10,950±60 12,375±35 14SN105, Area A Pre-Clovis Component ?

46. a = Charcoal e = Burnt phytolith B and C = Sporormiella spore

47.  6025+40  9240+70  10,350+25  12,375+40

48. Carychium exiguum The analysis of the Kanorado gastropod assemblage has not been completed, but preliminary results are as follows: Ca. 12,400-11,000 14C yr B.P. An abundance of aquatic gastropods, and the presence of Carychium exiguum, indicates ponded water (perhaps seasonal). Ca. 11,000-10,300 14C yr B.P. Aquatic species gradually decline in number at the expense of terrestrial species. It is getting drier at Kanorado. Ca. 10,300-9200 14C yr B.P. Aquatic species disappear from the assemblage and are replaced by terrestrial land snails that prefer dry environments. James L. Theler, Department of Sociology and Archaeology, University of Wisconsin-LaCrosse

49. Kanorado at ca. 12,500-11,000 14C yr B.P.

50. Kanorado at ca. 10,500 14C yr B.P.