DOCSLIB.ORG

Sangamonian(?) and Wisconsinan Paleoenvironments in Yellowstone National Park

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Sangamonian(?) and Wisconsinan Paleoenvironments in Yellowstone National Park Sangamonian(?) and Wisconsinan paleoenvironments in Yellowstone National Park RICHARD G. BAKER Department of Geology, University of Iowa, Iowa City, Iowa 52242 ABSTRACT This paper summarizes five pollen sequences, three of which con- tained plant macrofossils (see Fig. 1 for locations). The Grassy Lake Res- Pollen and plant macrofossil records from Yellowstone National ervoir pollen sequence was interpreted as a warm interstadial event (Baker Park, if combined with dated glacial events, provide a paleoenviron- and Richmond, 1978). In this paper, the pollen sequence is compared with mental record of much of the last glacial-interglacial cycle. Bull Lake plant macrofossils collected at the same time from the same section. Sec- glaciation has been dated at -140,000 yr B.P. Section EP-6 records a tion EP-6 was interpreted from initial pollen counts as a late-glacial to late-glacial to full interglacial sequence which is correlated with the full-interglacial sequence (Baker, 1981). The complete pollen sequence is Sangamonian interglacial and estimated to be 127,000 yr old at the presented here, along with a pollen concentration diagram. In addition, the peak warm period. A prevailing Pseudotsuga-Pinus flexilis-Pinus section was resampled, and the pollen and plant macrofossils from the ponderosa forest suggests that climate was considerably warmer than interglacial portion of the sequence are examined in detail. A second any in the Holocene. Section EP-5 is somewhat younger, probably section, EP-S, is stratigraphically above EP-6, and pollen and macrofossils late Sangamonian, and shows a forest dominated by Picea, Abies, from it are presented. Reconnaissance palynology of a younger, cold inter- Pseudotsuga, and a haploxylon Pinus. Slightly cooler conditions than stadial section is also briefly discussed. those of the present are indicated. Pollen sequences from Yellowstone National Park have outlined The warmest phase of the Grassy Lake Reservoir section is con- vegetational changes in late glacial and Holocene time (Baker, 1970,1976; sidered to be -82,000 yr old and records a warm interstadial cycle Waddington and Wright, 1974; Gennett, 1977). Plant macrofossil anal- beginning with tundra. The wanning sequence is indicated by change yses have provided more detailed understanding of these changes (Baker, to a Picea-A bies-Pinus albicaulis forest and then to a Pinus contorta 1976). Pollen sequences from southern Montana (Mehringer and others, forest. The cycle ends with forest destruction and a return to open 1977; Brant, 1980) and some plant-macrofossil work (R. C. Bright, 1980, (tundra?) and, presumably, cold conditions. written commun.) from Montana support the general trends for the region. Extremely low values of arboreal pollen indicate that tundra This late Quaternary work provides a basis for understanding the earlier vegetation and cold conditions continued from -70,000 to -50,000 yr pollen sequences. B.P. One cool and, apparently, short interstadial interrupted this ex- tended period of tundra shortly after 68,000 B.P. when a very open Vegetation and Climate parkland of Picea-A bies-Pinus albicaulis appeared. No records of environment are available between -50,000 and The vegetation of the Yellowstone Park region is grassland or steppe 30,000 yr B.P. The Pinedale icecap apparently expanded -30,000 yr at low elevations (below -1,700 m), a series of overlapping forest series at B.P. and lasted until -14,000 yr B.P. Late-glacial Picea-A bies-Pinus middle and upper elevations (1,700 to 3,000 m), and tundra on the high albicaulis parklands gave way to Pinus contorta forests that have mountaintops (>3,000 m) (Steele and others, 1983; Arno, 1979). The prevailed with minor variation for -10,000 yr. forest zones are broadly controlled by elevation and include (base to top) Pinus flexilis, Pseudotsuga, Pinus contorta, Picea engelmannii, Abies lasio- INTRODUCTION carpa, and Pinus albicaulis (Fig. 2). Topographic aspect, soil types, and other factors cause considerable variability in the elevation of each habitat Pollen sequences of pre-late Wisconsin or Sangamon age are known type, although the general pattern is widely established. Pinus ponderosa from few sites in the western United States. Heusser (1977) has developed does not grow locally in the Yellowstone Park area, but in central Mon- a generalized sequence of pollen assemblages back through the last inter- tana, it forms a habitat type below the Pinus flexilis type along the glacial period for western Washington, using a number of different sec- grassland-forest border (Arno, 1979). tions. Based on long cores from Clear Lake, Adam and West (1983) have Climatic stations in Yellowstone Park provide some data on the produced a continuous pollen sequence from Sangamon to present in climate associated with three of the habitat types (Fig. 2). Mean monthly central California. Few Rocky Mountain pollen records, however, are precipitation curves show that precipitation is rather evenly distributed older than Pinedale (late Wisconsin). Yellowstone National Park is per- throughout the year in this region. Mean monthly temperatures are lower haps unique in having many Wisconsin and older sections that contain each month at high-altitude sites as compared to low-altitude sites. Mean pollen and plant macrofossils (Baker and Richmond, 1978; Baker, 1981). annual temperature also varies inversely with altitude. Mean annual pre- The purposes of this paper are (1) to document vegetational sequences cipitation commonly increases with altitude, but Yellowstone National from early Wisconsin and probable Sangamon sites by comparing pollen Park has substantial variation of precipitation geographically (highest and plant macrofossil sequences and (2) to present a first approximation of values in the southwest corner and lowest along the northern border) so the environmental history of Yellowstone National Park during an esti- that the pattern is not uniform with elevation. The cause for this variation mated 140,000 yr. is uncertain, but it is not, apparently, caused by major air-mass boundaries Geological Society of America Bulletin, v. 97, p. 717-736,13 figs., 1 table, June 1986. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/6/717/3445121/i0016-7606-97-6-717.pdf by guest on 29 September 2021 718 R. G. BAKER Figure 1. Map of Yellowstone National Park showing ssunple lo- cations and arias men- tioned in text. Modified from Baker arid Rich- mond (1978). 440J 0 10 20 30 KILOMETERS L- _JI I _J in the region (Miichell, 1976). It may be that the southwest corner of the park has been glaciated several times (Richmond, 1970, 1976), iind the park receives maximum effect from westerly and southwesterly winds last major icecaps apparently occurred -140,000 and 20,000 to 30,000 yr blowing across the relatively low Snake River Plain (Mitchell,1976) and B.P. (Pierce and others, 1976; Pierce, 1979). suddenly cooling adiabatically as a result of the orographic effect of the Yellowstone Plateau. Methods The geology of Yellowstone National Park is fairly well known (Christiansen and Blank, 1972; Smedes and Prostka, 1972; Ruppel, 1972; The large sections exposed along stream cuts were measured using a Love and Keefer, 1975; Pierce, 1979). Volcanic and glacial geologic fea- steel tape, and samples were collected using shovels and knives. The slope tures predominate. Sedimentary rocks are exposed in the northwest and angles were measured with a Brunton compass, and the tape measure- south-central border areas of the park (U.S. Geological Survey, 1972). ments were corrected to vertical. Measurements of dipping units were Eocene volcanic and volcaniclastic rocks compose the Absaroka Range corrected to true thicknesses. Sediments were placed in plastic boxes or along the eastern border. Quaternary rhyolites from early to late Quater- zip-lock plastic bags and stored at room temperature. nary volcanic eruptions and related volcanic events cover central areas in Sediments were processed for pollen using a treatment modified from the park (Christiansen and Blank, 1972). The latest eruptive event took Faegri and Iversen (1975). Samples used for pollen concentration were place -70,000 yr ago and resulted in the Pitchstone Plateau flow. The immersed in water and their volume measured in a graduated centrifuge Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/6/717/3445121/i0016-7606-97-6-717.pdf by guest on 29 September 2021 SANGAMONIAN(?) AND WISCONSINAN PALEOENVIRONMENTS, YELLOWSTONE PARK 719 tube. A tablet containing 16,180 ± 1,500 gTains oi Eucalyptus pollen was GRASSY LAKE RESERVOIR added to these samples. All sediments were treated with KOH, HCL, HF, and acetolysis solution; rinsed in tertiary butyl alcohol; and mounted in The sample site at Grassy Lake Reservoir (Fig. 1) exposes lake sedi- silicon oil. In the spiked samples, Eucalyptus pollen grains were counted ments underlying Pinedale Till (Richmond, 1973, sec. 2; Baker and Rich- along with a minimum of 300 indigenous grains for calculation of pollen mond, 1978), and, in nearby sections, these lake sediments interfinger with concentration (Maher, 1972). Pollen was identified using the University of Bull Lake Till. Obsidian hydration dates indicate that the Bull Lake Till Iowa Pollen Reference Collection. was deposited before 130,000 yr B.P. near West Yellowstone, Montana About 200 ml of sediment for plant macrofossils analysis were (Pierce and others, 1976). Pieces of the Pitchstone Plateau rhyolite flow, washed through 35- and 105-mesh screens using a gentle stream of water which crops out "up-glacier" from Grassy Lake Reservoir, occur in the from a shower nozzle. The fossils were hand picked and then stored in overlying Pinedale Till but not in the lake sediments nor in Bull Lake Till glycerin. Seeds, fruits, leaves, bracts, and other macrofossils were identified by comparison with the Seed Collection of the Geology Department, University of Iowa. Elevations [-10,000 ft. (2970 m.) •9000 (2743) 8000 (2438) t/> <D N PI NUS CONTORTA PHASE 0C) E 7000 o CT (2133) eTín o X T) PSEUDOTSUGA MENZIESII SERIES <4— •D a>w 3 0.
Load more

Recommended publications
  • Wisconsinan and Sangamonian Type Sections of Central Illinois
    557 IL6gu Buidebook 21 COPY no. 21 OFFICE Wisconsinan and Sangamonian type sections of central Illinois E. Donald McKay Ninth Biennial Meeting, American Quaternary Association University of Illinois at Urbana-Champaign, May 31 -June 6, 1986 Sponsored by the Illinois State Geological and Water Surveys, the Illinois State Museum, and the University of Illinois Departments of Geology, Geography, and Anthropology Wisconsinan and Sangamonian type sections of central Illinois Leaders E. Donald McKay Illinois State Geological Survey, Champaign, Illinois Alan D. Ham Dickson Mounds Museum, Lewistown, Illinois Contributors Leon R. Follmer Illinois State Geological Survey, Champaign, Illinois Francis F. King James E. King Illinois State Museum, Springfield, Illinois Alan V. Morgan Anne Morgan University of Waterloo, Waterloo, Ontario, Canada American Quaternary Association Ninth Biennial Meeting, May 31 -June 6, 1986 Urbana-Champaign, Illinois ISGS Guidebook 21 Reprinted 1990 ILLINOIS STATE GEOLOGICAL SURVEY Morris W Leighton, Chief 615 East Peabody Drive Champaign, Illinois 61820 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/wisconsinansanga21mcka Contents Introduction 1 Stopl The Farm Creek Section: A Notable Pleistocene Section 7 E. Donald McKay and Leon R. Follmer Stop 2 The Dickson Mounds Museum 25 Alan D. Ham Stop 3 Athens Quarry Sections: Type Locality of the Sangamon Soil 27 Leon R. Follmer, E. Donald McKay, James E. King and Francis B. King References 41 Appendix 1. Comparison of the Complete Soil Profile and a Weathering Profile 45 in a Rock (from Follmer, 1984) Appendix 2. A Preliminary Note on Fossil Insect Faunas from Central Illinois 46 Alan V.
    [Show full text]
  • Lexicon of Pleistocene Stratigraphic Units of Wisconsin
    Lexicon of Pleistocene Stratigraphic Units of Wisconsin ON ATI RM FO K CREE MILLER 0 20 40 mi Douglas Member 0 50 km Lake ? Crab Member EDITORS C O Kent M. Syverson P P Florence Member E R Lee Clayton F Wildcat A Lake ? L L Member Nashville Member John W. Attig M S r ik be a F m n O r e R e TRADE RIVER M a M A T b David M. Mickelson e I O N FM k Pokegama m a e L r Creek Mbr M n e M b f a e f lv m m i Sy e l M Prairie b C e in Farm r r sk er e o emb lv P Member M i S ill S L rr L e A M Middle F Edgar ER M Inlet HOLY HILL V F Mbr RI Member FM Bakerville MARATHON Liberty Grove M Member FM F r Member e E b m E e PIERCE N M Two Rivers Member FM Keene U re PIERCE A o nm Hersey Member W le FM G Member E Branch River Member Kinnickinnic K H HOLY HILL Member r B Chilton e FM O Kirby Lake b IG Mbr Boundaries Member m L F e L M A Y Formation T s S F r M e H d l Member H a I o V r L i c Explanation o L n M Area of sediment deposited F e m during last part of Wisconsin O b er Glaciation, between about R 35,000 and 11,000 years M A Ozaukee before present.
    [Show full text]
  • Glacial Geology of the Vandalia, Illinois, Region
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE i42 ILLINOtS GEOLOGICAL provided by Illinois Digital Environment for Access to Learning and Scholarship... S SURVEY LIBRARY 14.GS: CIR442 STATE ILLINOIS c. 1 OF DEPARTMENT OF REGISTRATION AND EDUCATION GLACIAL GEOLOGY OF THE VANDALIA. ILLINOIS. REGION Alan M. Jacobs Jerry A. Lineback CIRCULAR 442 1969 ILLINOIS STATE GEOLOGICAL SURVEY URBANA, ILLINOIS 61801 John C. Frye, Chief Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/glacialgeologyof442jaco GLACIAL GEOLOGY OF THE VANDALIA, ILLINOIS, REGION Alan M. Jacobs and Jerry A. Lineback ABSTRACT Deposits and soils of the Kansan, Yarmouthian, Illinoian, Sangamonian, and Wisconsinan Stages are pre- sent in the region surrounding Vandalia (south-central), Illinois. Kansan till exposures, with a truncated Yarmouth Soil, are exposed at a few places. The unaltered till is sandy and silty M and its less than 2-micron size fraction contains abundant illite and more calcite than dolomite. The Smithboro till (lowermost Illinoian) is relatively silty, plastic, and its less than 2-micron size fraction contains more dolomite than calcite and more expandable clay min- erals than any till in this region. The overlying Vandalia till (Illinoian) is relatively sandy, friable, and its less than 2-micron size fraction contains abundant illite and more dolomite than calcite. The Mulberry Grove silt lies between the Vandalia and Smithboro tills at some localities. The Hagarstown beds (Illinoian) overlie the Vandalia till and consist of sand, gravel, poorly sorted gravel, and gravelly till.
    [Show full text]
  • Stratigraphy and Pollen Analysis of Yarmouthian Interglacial Deposits
    22G FRANK R. ETTENSOHN Vol. 74 STRATIGRAPHY AND POLLEN ANALYSIS OP YARMOUTHIAN INTERGLACIAL DEPOSITS IN SOUTHEASTERN INDIANA1 RONALD O. KAPP AND ANSEL M. GOODING Alma College, Alma, Michigan 48801, and Dept. of Geology, Earlham College, Richmond, Indiana 47374 ABSTRACT Additional stratigraphic study and pollen analysis of organic units of pre-Illinoian drift in the Handley and Townsend Farms Pleistocene sections in southeastern Indiana have provided new data that change previous interpretations and add details to the his- tory recorded in these sections. Of particular importance is the discovery in the Handley Farm section of pollen of deciduous trees in lake clays beneath Yarmouthian colluvium, indicating that the lake clay unit is also Yarmouthian. The pollen diagram spans a sub- stantial part of Yarmouthian interglacial time, with evidence of early temperate and late temperate vegetational phases. It is the only modern pollen record in North America for this interglacial age. The pollen sequence is characterized by extraordinarily high per- centages of Ostrya-Carpinus pollen, along with Quercus, Pinus, and Corylus at the beginning of the record; this is followed by higher proportions of Fagus, Carya, and Ulmus pollen. The sequence, while distinctive from other North American pollen records, bears recogniz- able similarities to Sangamonian interglacial and postglacial pollen diagrams in the southern Great Lakes region. Manuscript received July 10, 1973 (73-50). THE OHIO JOURNAL OF SCIENCE 74(4): 226, July, 1974 No. 4 YARMOUTH JAN INTERGLACIAL DEPOSITS 227 The Kansan glaeiation in southeastern Indiana as discussed by Gooding (1966) was based on interpretations of stratigraphy in three exposures of pre-Illinoian drift (Osgood, Handley, and Townsend sections; fig.
    [Show full text]
  • Overkill, Glacial History, and the Extinction of North America's Ice Age Megafauna
    PERSPECTIVE Overkill, glacial history, and the extinction of North America’s Ice Age megafauna PERSPECTIVE David J. Meltzera,1 Edited by Richard G. Klein, Stanford University, Stanford, CA, and approved September 23, 2020 (received for review July 21, 2020) The end of the Pleistocene in North America saw the extinction of 38 genera of mostly large mammals. As their disappearance seemingly coincided with the arrival of people in the Americas, their extinction is often attributed to human overkill, notwithstanding a dearth of archaeological evidence of human predation. Moreover, this period saw the extinction of other species, along with significant changes in many surviving taxa, suggesting a broader cause, notably, the ecological upheaval that occurred as Earth shifted from a glacial to an interglacial climate. But, overkill advocates ask, if extinctions were due to climate changes, why did these large mammals survive previous glacial−interglacial transitions, only to vanish at the one when human hunters were present? This question rests on two assumptions: that pre- vious glacial−interglacial transitions were similar to the end of the Pleistocene, and that the large mammal genera survived unchanged over multiple such cycles. Neither is demonstrably correct. Resolving the cause of large mammal extinctions requires greater knowledge of individual species’ histories and their adaptive tolerances, a fuller understanding of how past climatic and ecological changes impacted those animals and their biotic communities, and what changes occurred at the Pleistocene−Holocene boundary that might have led to those genera going extinct at that time. Then we will be able to ascertain whether the sole ecologically significant difference between previous glacial−interglacial transitions and the very last one was a human presence.
    [Show full text]
  • Modelling the Concentration of Atmospheric CO2 During the Younger Dryas Climate Event
    Climate Dynamics (1999) 15:341}354 ( Springer-Verlag 1999 O. Marchal' T. F. Stocker'F. Joos' A. Indermu~hle T. Blunier'J. Tschumi Modelling the concentration of atmospheric CO2 during the Younger Dryas climate event Received: 27 May 1998 / Accepted: 5 November 1998 Abstract The Younger Dryas (YD, dated between 12.7}11.6 ky BP in the GRIP ice core, Central Green- 1 Introduction land) is a distinct cold period in the North Atlantic region during the last deglaciation. A popular, but Pollen continental sequences indicate that the Younger controversial hypothesis to explain the cooling is a re- Dryas cold climate event of the last deglaciation (YD) duction of the Atlantic thermohaline circulation (THC) a!ected mainly northern Europe and eastern Canada and associated northward heat #ux as triggered by (Peteet 1995). This event has been dated by annual layer counting between 12 700$100 y BP and glacial meltwater. Recently, a CH4-based synchroniza- d18 11550$70 y BP in the GRIP ice core (72.6 3N, tion of GRIP O and Byrd CO2 records (West Antarctica) indicated that the concentration of atmo- 37.6 3W; Johnsen et al. 1992) and between 12 940$ 260 !5. y BP and 11 640$ 250 y BP in the GISP2 ice core spheric CO2 (CO2 ) rose steadily during the YD, sug- !5. (72.6 3N, 38.5 3W; Alley et al. 1993), both drilled in gesting a minor in#uence of the THC on CO2 at that !5. Central Greenland. A popular hypothesis for the YD is time. Here we show that the CO2 change in a zonally averaged, circulation-biogeochemistry ocean model a reduction in the formation of North Atlantic Deep when THC is collapsed by freshwater #ux anomaly is Water by the input of low-density glacial meltwater, consistent with the Byrd record.
    [Show full text]
  • The Great Ice Age Owned Public Lands and Natural and Cultural Resources
    U.S. Department of the Interior / U.S. Geological Survey____ As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally The Great Ice Age owned public lands and natural and cultural resources. This includes fostering wise use of our land and water resources, protecting our fish and wildlife, preserving the environ­ mental and cultural values of our national parks and histor­ ical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also promotes the goals of the Take Pride in America campaign by encouraging stewardship and citizen responsibility for the public lands and promoting citizen participation in their care. The Department also has a major responsibility for American Indian reservation communities and for people who live in Island Territories under U.S. Administration. Blue Glacier, Olympic National Park, Washington. The Great Ice Age land, indicating that conditions somewhat similar to those which produced the Great Ice by Louis L. Ray Age are still operating in polar and subpolar climates. The Great Ice Age, a recent chapter in the Much has been learned about the Great Ice Earth's history, was a period of recurring Age glaciers because evidence of their pres­ widespread glaciations. During the Pleistocene ence is so widespread and because similar Epoch of the geologic time scale, which conditions can be studied today in Greenland, began about a million or more years ago, in Antarctica, and in many mountain ranges mountain glaciers formed on all continents, where glaciers still exist.
    [Show full text]
  • Glacial/Interglacial Variations in Atmospheric Carbon Dioxide
    review article Glacial/interglacial variations in atmospheric carbon dioxide Daniel M. Sigman* & Edward A. Boyle² * Department of Geosciences, Guyot Hall, Princeton University, Princeton, New Jersey 08544, USA ² Department of Earth, Atmospheric, and Planetary Sciences, Room E34-258, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Massachusetts 02139, USA ............................................................................................................................................................................................................................................................................ Twenty years ago, measurements on ice cores showed that the concentration of carbon dioxide in the atmosphere was lower during ice ages than it is today. As yet, there is no broadly accepted explanation for this difference. Current investigations focus on the ocean's `biological pump', the sequestration of carbon in the ocean interior by the rain of organic carbon out of the surface ocean, and its effect on the burial of calcium carbonate in marine sediments. Some researchers surmise that the whole-ocean reservoir of algal nutrients was larger during glacial times, strengthening the biological pump at low latitudes, where these nutrients are currently limiting. Others propose that the biological pump was more ef®cient during glacial times because of more complete utilization of nutrients at high latitudes, where much of the nutrient supply currently goes unused. We present a version of the latter hypothesis that focuses on the open ocean surrounding Antarctica, involving both the biology and physics of that region. he past two million years have been characterized by of these mechanisms with data from the recent geological and large cyclic variations in climate and glaciation. During glaciological record has been a challenging and controversial task, cold `ice age' periods, large continental ice sheets cover leading as yet to no consensus on a fundamental mechanism.
    [Show full text]
  • How Did Marine Isotope Stage 3 and Last Glacial Maximum Climates Differ? – Perspectives from Equilibrium Simulations
    Clim. Past, 5, 33–51, 2009 www.clim-past.net/5/33/2009/ Climate © Author(s) 2009. This work is distributed under of the Past the Creative Commons Attribution 3.0 License. How did Marine Isotope Stage 3 and Last Glacial Maximum climates differ? – Perspectives from equilibrium simulations C. J. Van Meerbeeck1, H. Renssen1, and D. M. Roche1,2 1Department of Earth Sciences - Section Climate Change and Landscape Dynamics, Faculty of Earth and Life Sciences, VU University Amsterdam, de Boelelaan 1085, 1081HV Amsterdam, The Netherlands 2Laboratoire des Sciences du Climat et de l’Environnement (LSCE/IPSL), Laboratoire CEA/INSU-CNRS/UVSQ, C.E. de Saclay, Orme des Merisiers Bat. 701, 91190 Gif sur Yvette Cedex, France Received: 15 August 2008 – Published in Clim. Past Discuss.: 6 October 2008 Revised: 14 January 2009 – Accepted: 20 February 2009 – Published: 5 March 2009 Abstract. Dansgaard-Oeschger events occurred frequently mimics stadials over the North Atlantic better than both con- during Marine Isotope Stage 3 (MIS3), as opposed to the fol- trol experiments, which might crudely estimate interstadial lowing MIS2 period, which included the Last Glacial Max- climate. These results suggest that freshwater forcing is nec- imum (LGM). Transient climate model simulations suggest essary to return climate from warm interstadials to cold sta- that these abrupt warming events in Greenland and the North dials during MIS3. This changes our perspective, making the Atlantic region are associated with a resumption of the Ther- stadial climate a perturbed climate state rather than a typical, mohaline Circulation (THC) from a weak state during sta- near-equilibrium MIS3 climate.
    [Show full text]
  • The Sangamonian Stage and the Laurentide Ice Sheet Le Sangamonien Et La Calotte Glaciaire Laurentidienne Die Sangamonische Zeit Und Die Laurentische Eisdecke Denis A
    Document généré le 4 oct. 2021 02:19 Géographie physique et Quaternaire The Sangamonian Stage and the Laurentide Ice Sheet Le Sangamonien et la calotte glaciaire laurentidienne Die sangamonische Zeit und die laurentische Eisdecke Denis A. St-Onge La calotte glaciaire laurentidienne Résumé de l'article The Laurentide Ice Sheet La présente revue des travaux sur le Sangamonien (jusqu'à juin 1986) effectués Volume 41, numéro 2, 1987 dans des régions clés démontre qu'il n'y a pas encore de réponse satisfaisante à la question suivante: « À quel moment la glace, qui allait devenir la calotte URI : https://id.erudit.org/iderudit/032678ar glaciaire laurentidienne, a-t-elle commencer à s'accumuler? » Dans la plupart DOI : https://doi.org/10.7202/032678ar des régions, la séquence stratigraphique ne fait que signaler l'existence probable d'une période interglaciaire, sans toutefois permettre de déterminer le moment où la glace a commencé à s'accumuler après l'intervalle climatique Aller au sommaire du numéro chaud. Il existe toutefois quelques indices. Les sédiments d'un delta glaciolacustres de la Formation de Scarborough, dans la région de Toronto, et le Till de Bécancour, dans la région de Trois-Rivières, datent probablement du Éditeur(s) Sangamonien (sous-phases isotopiques marines 5d-b). Le Till d'Adam, dans les basses terres de la baie James, leur est probablement corrélatif. Dans les Les Presses de l'Université de Montréal régions atlantiques du Canada, en particulier à l'île du Cap-Breton, des restes de plantes indiquent que le climat au cours du Sangamonien moyen aurait été ISSN très semblable à celui de la période de 11 000 à 12 000 ans BP.
    [Show full text]
  • And Wisconsinan Paleoenvironments in Yellowstone National Park
    Sangamonian(?) and Wisconsinan paleoenvironments in Yellowstone National Park RICHARD G. BAKER Department of Geology, University of Iowa, Iowa City, Iowa 52242 ABSTRACT This paper summarizes five pollen sequences, three of which con- tained plant macrofossils (see Fig. 1 for locations). The Grassy Lake Res- Pollen and plant macrofossil records from Yellowstone National ervoir pollen sequence was interpreted as a warm interstadial event (Baker Park, if combined with dated glacial events, provide a paleoenviron- and Richmond, 1978). In this paper, the pollen sequence is compared with mental record of much of the last glacial-interglacial cycle. Bull Lake plant macrofossils collected at the same time from the same section. Sec- glaciation has been dated at -140,000 yr B.P. Section EP-6 records a tion EP-6 was interpreted from initial pollen counts as a late-glacial to late-glacial to full interglacial sequence which is correlated with the full-interglacial sequence (Baker, 1981). The complete pollen sequence is Sangamonian interglacial and estimated to be 127,000 yr old at the presented here, along with a pollen concentration diagram. In addition, the peak warm period. A prevailing Pseudotsuga-Pinus flexilis-Pinus section was resampled, and the pollen and plant macrofossils from the ponderosa forest suggests that climate was considerably warmer than interglacial portion of the sequence are examined in detail. A second any in the Holocene. Section EP-5 is somewhat younger, probably section, EP-S, is stratigraphically above EP-6, and pollen and macrofossils late Sangamonian, and shows a forest dominated by Picea, Abies, from it are presented. Reconnaissance palynology of a younger, cold inter- Pseudotsuga, and a haploxylon Pinus.
    [Show full text]
  • STAGES of the ICE AGE 1 (Presented Before the Society
    BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA VOL. 33, PP. 491-514 SEPTEMBER 1, 1922 \ STAGES OF THE ICE AGE 1 BY WARREN UPHAM (Presented before the Society December 28, 1921) CONTENTS Page Sequence of glacial and interglacial stages....................................................... 491 Nebraskan' glaciation.................................................................................................. 493 The Aftonian interglacial stage............................................................................. 495 Kansan glaciation.... t............................................................................................. 499 The Yarmouth interglacial stage.......................................................................... 503 Illinoian glaciation..................................................................................................... 504 The Sangamon interglacial stage........................................................................... 505 Iowan glaciation and loess deposition................................................................. 506 The Peorian interglacial stage................................................................................ 506 Wisconsin glaciation.................................................................................................. 507 The Champlain stage................................................................................................. 510 Estimated time ratios...............................................................................................
    [Show full text]