dr. rolfe d. mandel, executive director odyssey research program kansas geological survey university...
TRANSCRIPT
Dr. Rolfe D. Mandel, Executive Director Odyssey Research ProgramKansas Geological Survey
University of Kansas
Using Soils to Reconstruct Climate
Five Soil Forming Factors
• Climatic Factor• Biotic Factor• Topographic Factor• Parent Material• Time Factor
When using soils to reconstruct climate, it is useful to consider the concept of “pedogenic pathways.”
A pedogenic pathway is a set of pedogenicprocesses leading to a given soil morphology.
Soils in different bio-climatic regions follow different pedogenic pathways.
A good way to understand the relationship between bio-climates and pedogenic pathways is to consider modern analogs.
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.
Tallgrass prairie in the Flint Hills of eastern Kansas
Mean Annual Precipitation: 26-28 inches
Mixed grass prairie on the High Plains of central Kansas
Mean Annual Precipitation: 22-24 inches
Short grass prairie on the High Plains of northwestern Kansas
Mean Annual Precipitation: 17-19 inches
Short grass prairie on the High Plains of southwestern Kansas
Mean Annual Precipitation: 11-13 inches
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
Southern Pine forest of SE Texas
Alfisol
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)
Oxisol in Hawaii
Oxisol in Brazil
Laterite in Brazil
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
Buried soils represent previous land surfaces (landscapes) that were stable for long enough periods to develop recognizable soil profile characteristics.
Buried Soils
20,080 ± 56020,080 ± 560
32,850 ± 53032,850 ± 530
13,960±±150
2003 Excavation in Lower Mammoth/Camel Level2003 Excavation in Lower Mammoth/Camel Level
Lower Mammoth/Camel Bone Level, June 2003
12,215 ± 3512,215 ± 35
14SN105, Area A
92409240±70±70
97509750±70±70
10,37010,370±20±20
10,95010,950±60±60
12,21512,215±35±35
Folsom Folsom ComponentComponent
Clovis Clovis ComponentComponent
Pre-Clovis Pre-Clovis ComponentComponent ??
The following fossils may be preserved in soils and can provide valuable information about climate change:
PhytolithsGastropods
There is almost always some organic carbon preserved in soils – Stable carbon isotope (13C) analysis.
• 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
Phytolith = “Plant Stone”
Why do plants produce phytoliths?
• Structural functionsStructural functions: silica provides plant rigidity
• Physiological functionsPhysiological functions: lessens effects of heavy metals
• Protective functionsProtective functions: against herbivores, insects, pathogenic fungi
Grass phytoliths are:abundant, durable, morphologically different, taxonomically identifiable…
Excellent for reconstructing paleoenvironments, including climate!
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
Some diagnostic trees & shrubs
Celtis occidentalis
(Hackberry)Diagnostic seed covering of sedges
Stable Isotope Geochemistry
• Stable Carbon Isotopes in Soil Organic Matter
• Stable Carbon and Oxygen Isotopes in Soil Inorganic Carbon
• Oxygen Isotopes in Faunal Remains
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‰ From Koch, P.L., 1998,
Isotopic Reconstructionof Past ContinentalEnvironments:Ann. Rev. Earth Planet.Sci. 26:573-615.
δ13C value differences trees (C3) vs. grasses (C4)
CO2
C-3 C-4
δ13C= -26 to - 22 δ13C= -16 to -12
PhotosynthesisPhotosynthesis
Soil Organic Matter-26 -24 -22 -20 -18 -16 -14 -12
Gastrocopta contracta
(2.4 mm)
Carychium exiguum
Discus whitneyi Gastrocopta contracta
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.
14SN105, Area A
92409240±70±70
97509750±70±70
10,37010,370±20±20
10,95010,950±60±60
12,37512,375±35±35
Folsom Folsom ComponentComponent
Clovis Clovis ComponentComponent
Pre-Clovis Pre-Clovis ComponentComponent ??
a = Charcoale = Burnt phytolith
B and C = Sporormiella spore
10,350+25
9240+70
6025+40
12,375+40
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
Kanorado at ca. 12,500-11,000 14C yr B.P.
Kanorado at ca. 10,500 14C yr B.P.
Kanorado at ca. 9000 14C yr B.P. (minus the vehicles, billboard, and portable toilet)
14SN105, Area A
92409240±70±70
97509750±70±70
10,37010,370±20±20
10,95010,950±60±60
12,37512,375±35±35
Folsom Folsom ComponentComponent
Clovis Clovis ComponentComponent
Pre-Clovis Pre-Clovis ComponentComponent ??
JVC Device
Md. A Core
Let’s look at some soil and learn something about climate change!