2013 - Speaker's Notes for GSA Presentation Published Speaker's Notes

GSA Talk, 2013:

Slide 1: Magnitude of Quaternary temperature fluctuations inferred from relict paleosols and periglacial features,
Waterton-Glacier Park area, Montana and Alberta

Good morning. In this talk, I will try to try to summarize the “headlines” from 24 years’ research and some 12 professional papers. So I may have to talk fast!

Slide 2: The headlines are:

1) Properties of paleosols preserved on erosion surface remnants in the Waterton-Glacier Parks area suggest mean annual temperatures during interglacial maxima were considerably warmer than present (by at least 6-8° C).

2) Occurrence of fossil periglacial features indicates average annual temperatures were considerably colder than present during glacial maxima (by at least 10 C).

3) These data suggest magnitude of average annual temperatures in this continental area fluctuated by at least 16 to 18 °C.

4) Several independent lines of evidence support these estimates.

Slides 3, 4, and 5: Digression to first principles. As we all know from our introductory geography classes, the global distribution of climates, vegetation types, and soil types strongly overlap. This is because climate, the independent variable, is the primary determinant of what kinds of vegetation assemblages and soil types form where.

Slides 6. Thus, by examining the geographic distribution of plant fossils over the past 55 million years (figure to right), for instance, we are able to infer that Tertiary climates were considerably warmer than the present and that the main trend over the past 55 million years has been toward cooling to the present time.

Slide 7: Here are reconstructed paleotemperatures in Europe, North America and Japan (for example) through time based on plant fossil distribution that show this trend. During early Tertiary (Eocene), when average temperatures were some 10 degrees C higher than present, tropical and subtropical climates extended into the middle latitude areas.

Slide 8. Soil evidence corroborates this. For example, in central/northern California (La Grange north to Ione) is the Eocene Ione Formation, a tropical laterite (Oxisol) soil. Clearly, this paleosol is out of equilibrium with the present climate and vegetation of this region. Rather, its properties record the considerably wetter and warmer tropical environmental conditions under which it formed.

This Oxisol profile consists of ironstone caprock, overlying 2 m pallid zone, and 4+ m red oxic horizon.

Ancient soils or paleosols typically bear the imprint of the “strongest” soil forming interval to which they were exposed. Irreversible soil properties, such as plinthite, paleoargillic horizons, calcrete, etc. reflect environmental conditions under which they formed.

Thus, where paleosols which have characteristics that are out of equilibrium with present climate, past environmental conditions may be inferred from those soil properties.

Slide 9. The study area is along the eastern margin of Waterton-Glacier Parks in Alberta and Montana. This area marks the extreme southwestern extent of the Laurentide continental glacier, in a zone where the continental glacier overlapped with piedmont glaciers emanating from the northern Rocky Mountains. Note that in terms of erosion and deposition of successive continental glaciers, Canada is the zone of erosion, whereas the northern US is the zone of deposition, where the older sediments and soils (i.e., paleosols) are better preserved.

This project began for me with my Ph.D. research in the late 70’s and has continued into this century. My interpretations build mainly on the previous work of W.C. Alden (1920’s), Leland Horberg (1950’s), G.M. Richmond (1950’s), and the Dutch pedologist, P.D. Jungerius (1960’s),

Remnants of various erosion surfaces (referred to as the Flaxville (or No. 1), and No. 2 and 3 benches by Alden, 1920’s) are shown in the lower left and heights and gradients of these surfaces in the North Fork of the Milk River area are shown in the lower right.

Slide 10: Paleosols and periglacial features examined here are preserved on these erosion surface remnants. Note that the No. 1 bench (Flaxville surface) adjoins the easternmost Lewis Range (upper left), that granite erratics from the Canadian shield occur on the No. 2 bench east of the mountains (upper right), and that in some locales all three surfaces are found in the same vicinity (lower right), and an example of pre-Wisconsinan paleosol on a remnant of the youngest (#3) bench.

Slide 11. Soil scientist, Hans Jenny, tried to quantify the influence of each of the 5 soil forming factors, (climate, vegetation, parent material, slope and time) on soil, giving us the famous equation S=f(cl,o, r,p,t….). In mature (zonal) soils, Jenny and others determined that climate is the primary determinant of soil properties.

In the figure to the lower left, various soil Suborders are shown in relation with different moisture and temperature regimes. M indicates the soil suborders identified in this study area that are Modern (post-glacial) soils and P stands for paleosols. Australian soil scientist, Duchafour, uses a different soil classification system that shows the same general correlations between different soil types and the climate factors of moisture and temperature. I include Duchafour’s system because it better describes the soil types in this area.

Slide 12: Map in the upper right shows the boundaries of Laurentide and mt. piedmont glaciers, the distribution of No. 1, 2, and 3 bench remnants, and locations of paleosols and periglacial features examined here. The photos in the upper left show modern soils developed in Wisconsinan-aged moraines (lower left).

Slide 13: Pre-Wisconsinan soils (paleosols) are locally preserved on the erosion surfaces. The Cloudy Ridge site, just east of Waterton Park, Alberta, is the northernmost locale where I sampled and described the pre-Wisconsin.paleosols. Horberg (1952) considered Cloudy Ridge to be a possible Number 2 bench remnant. Pebble fabrics, striated rocks and bullet boulders indicate the parent material is of glacial origin and came from the mountains. Fabrics suggest the entire section is comprised of one undeformed lodgement till or basal till.

W.C Alden made the early descriptions the diamicton that caps these erosion surfaces, referring to this diamict as pre-Wisconsin “Kennedy drift.”

Paleomagnertic analyses by Dr. Rene Baredregt indicates the paleosol and parent till are normally magnetized. Thus, we assigned this unit to the Brunhes Normal Polarity Epoch (last 780,000 yr). The paleosol is a very strongly developed and includes a 183-cm thick, rubified argillic horizon that overlies a 13-m thick CaCO3-cemented horizon or calcrete.

Slide 14. Brief summary of soil properties of modern soils vs. paleosols.

Modern soils are classified as Cryoborolls, Cryochrepts, Cryoboralfs, Cryorthods and typically have 8-20 cm-thick A horizons, 0 – 30 cm thick brown Bt or Bw horizons, and 0 – 119-cm-thick Bk horizons.

Paleosols are harder to classify because they are polygentic. However, based on their meta-stable and irreversible properties, most resemble Paleudalfs, Palustalfs, and Paleudolls (or fersiallitic soils, Duchafour, 1977). They typically include 1 – 4+ m-thick, leached, clay-rich, yellowish red to red argillic (Bt) horizons that overly 0– 15-m-thick Bk and Bkm horizons. Bt horizons in paleosols have an average absolute clay increase of 18.6% and a distinctive clay mineral suite with mixed-layer clays. Depth of leaching ranges from 2.1 – 10 m and averages 440+ cm

Slide 15. Kennedy Drift.

Paleosols are developed in “Kennedy Drift”, a generally massive, matrix-supported sandy loam with weak to no bedding. Diamicton units are 4-10+ m thick, laterally continuous, and include a mix of Precambrian Belt Supergroup sedimentary rocks derived from the mountains. Pebble fabrics and other properties indicate material is mostly of glacial origin (deformed and undeformed lodgment till).

Slide 16. Pick and shovel in hand, I excavated numerous trenches on natural landslide scarp exposures of the Kennedy Drift on the different Flaxville bench remants in order to expose fresh material and work out stratigraphic relations of tills and overlying paleosols. In so doing, I was able to recognize multiple diamicts separated by intercalated paleosols on the various Flaxville bench remants, with 5 superposed till units on Mokowan Butte, Alberta and Saint Mary Ridge, Montana, and 4 units on Two Medicine Ridge, Montana.

Slide 17. After describing the soil horizons in the field, I retired to the laboratory with hundreds of samples of the various soil horizons as well as unweathered parent material. Genearlly speaking, the paleosols share a number of distinctive characteristics. They typically have thick (up to 4+ m) strongly oxidized (rubified), argillic horizons, with significant (9-42%) clay buildup of clay, clay films, distinct clay mineral suite with mixed-layer clays, are leached of carbonates to a depth of 40 cm to 10+ m and are often associated with underlying carbonate-rich zones. In this figure, particle-size analyses of soils and sediments collected from the various paleosol/till sequences clearly indicate the paleoargillic horizons.

Slide 18. Paleomagnetic analyses carried out at the best sites by Canadian earth scientists, Dr. Rene Barendreght and Maria Cioppa indicate that the upper unit (upper two on SMR) falls within the Bruhnes Normal Polarity Epoch (about last 780,000 yr) whereas lower units on Mokowan Butte, Saint Mary Ridge and Two Medicine Ridge, have reversed polarity and are therefore assigned to the Matuyama Reversed Polarity Epoch (0.78 to 2.6 my).

Paleomagnetic analyses permits the following magnetostraphic correlations.

Slide 19. At Mokowan Butte, Alberta, a Flaxville or #1 bench remnant east of Waterton Park, stratigraphic relations of paleosols and parent diamicts were based on fresh roadcuts and excavation of two trenches. Again, description and sampling indicates 5 paleosols occur in 5 diamictons here. The upper paleosol/diamict (unit 5) is normally magnetized and the much thicker, more strongly developed paleosols 4 and 3 have reversed polarity. Striated rocks were found throughout the section.

Slide 20. A series of trenches on Saint Mary Ridge, Montana, another Flaxville bench remnant, also reveal at least 5 superposed tills separated by intervening weathering zones and/or paleosols. Pebble fabric data indicate a glacial origin for all units. Again, the upper two units are normally magnetized whereas the lower three are have reversed polarity.

Slide 21. On Two Medicine Ridge, the farthest south of the Flaxville bench remants, the upper paleosol/till unit has normal polarity, and three underlying units have reversed polarity.

Horberg analyzed this section in detail in 1956, and also concluded that that the “profile of weathering” formed under conditions that were considerably warmer and moister than today, also comparing the paleosol with modern day subtropical and Mediterranean type soils. Dutch soil scientist, P.D. Jungerious reached this same conclusion after analyzing the similar paleosol that caps the Cypress Hills in Saskatchewan.

Slide 22. In my various papers, I have provided extensive lab data for all these paleosols/parent tills.

Slide 23. Field and laboratory properties of the paleosols most resemble those of Paleudalfs and Paleudolls (American system) or fersiallitic soils (Duchafour, 1977). Combining Horberg’s geochemical analyses with the diagrams from Duchafour, 1977, we see that the weathering properties of the paleosol are intermediate between those of temperate and tropical soils. Again, these (fersiallitic) soil types typically form under warmer and moister climates, such as now are found in the SE U.S.

Slide 24. The paleosols are paleosols because:

1) Although they have limited distribution due to erosion, they are laterally continuous across a broad geographic region in northern Montana and in southern Canada (Alberta and Saskatchewan).

2) Nearly identical paleosols occur at the surface and in buried situations. Hence, their properties are pedogenic rather than diagenetic.

3) Their suite of properties resemble those of (fersiallitic) soils that form in subtropical to humid Mediterranean climates. Formation of fersiallitic soils requires MAT of 13 to 20 °C (or 11 to 18 °C warmer than present in this area.)

4) Their great thickness suggests they probably formed over long time periods (hundreds of thousands of years).

Slide 25. Other lines of evidence confirm that past interglacials were considerably warmer than today’s climate? Fossil giant tortoise shells have been identified in Sangamonian deposits in Illinois (King and Saunders, 1986). These types of giant land tortoises are now found in tropical and subtropical regions because they cannot survive freezing temperatures. Researchers who have examined Sangamonian and Yarmouthian vertebrate faunas in the Midwest (Brattstrom, 1961, Hibbard, 1970, Preston, 1976) estimate that the presence of these kinds fossils (including alligators, etc.) suggests mean annual temperatures were 10-11 degrees C warmer during the Yarmouth interglacial and 7 degrees C warmer than present Sangamon interglacial.

Slide 26. In his book, Climatic Fluctuations of the Ice Age (1973), Frenzel concluded that, based on fossil pollen evidence, MATs in Eurasia and North America were 6-12 degrees C warmer than present during Yarmouth and Sangamon interglacials.

Slide 27. Additionally, distribution of temperature-sensitive planktonic foraminifera in the eastern North Pacific ocean indicate that Pleistocene interglacial climates were characterized by sea surface temperatures that were over 5-8 degrees C warmer than today.

Slide 28. Particular kinds of periglacial features also are associated with particular climate regimes. At right is a map showing the modern distribution of zones of continuous, discontinous and sporadic permafrost. Obviously, these boundaries have also shifted significantly during the Quaternary.

Slide 29. One of the best paleotemperature indicators are ice-wedge casts because it has been shown that ice-wedges form under conditons of continuous permafrost where the mean annual temperature is -6 to -8 degees C or colder.

Slides 30 and 31. Hence, identification of ice-wedge casts on the erosion surface remnants (No. 2 bench) that occur along the southern boundary of the Laurentide ice sheet in this area indicates that average annual temperatures here were at least 10 degrees C colder than today. (Today, average annual temperature is about 4 degrees C).

Slide 32. This conclusion is consistent with the CLIMAP projects’ estimate that average July temperatures were 14 to 15 C colder during the last glacial maxima than they are today.

Slide 33. Conclusions.

1. Properties of fossil paleosols and periglacial features in the Waterton-Glacier Park area suggest that mean annual temperatures here were at least 6 °C warmer than present during interglacial maxima and at least -10 to 12 °C colder than today during glacial maxima, a range of at least 16-18 °C.

2. Interglacial climates were probably quite different (warmer, wetter, more “equable” and “oceanic”) than today’s.

3. The great Serbian mathematician, Milutin Milankovitch (of the Milankovitch or astronomic theory of climate change) utilized the concept of “equivalent latitude” to better understand the magnitude of changes in Quaternary climates. Inferred temperature fluctuations discussed here amount to a displacement of “equivalent latitude” in this region of at least 27 degree. I.e., temperatures during glacial maxima in the study area resembled present conditions at 65° N and farther north whereas temperatures during interglacial maxima resembled current conditions at 38° N and farther south.

Slide 34. Secondary conclusions.

1) If you really want to uncover pedological and paleoclimatic truth……

You have to dig for it.

2) Man-caused global warming = no big deal compared to natural climate fluctuations. The postulated O.6 °C warming during the modern warming period (1850-present) is a minor temperature change and well within natural fluctuations of average temperatures. The natural range of temperature change in this continental climate (at least 16 to 18 °C) is about 30+ times greater than the supposedly “unprecedented and catastrophic” global warming postulated for the 20th century.