DOCSLIB.ORG

Age of Pre-Neoglacial Cirque Moraines in the Central North

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Age of Pre-Neoglacial Cirque Moraines in the Central North Document generated on 09/24/2021 10:42 p.m. Géographie physique et Quaternaire Age of Pre-Neoglacial Cirque Moraines in the Central North American Cordillera L’âge des moraines de cirques pré-néoglaciaires du centre de la Cordillère nord-américaine Datierung der präneoglazialen Moränen im zentralen Norden der amerikanischen Kordilleren P. Thompson Davis and Gerald Osborn Volume 41, Number 3, 1987 Article abstract In the western mountains of the United States and Canada are pre-Neoglacial URI: https://id.erudit.org/iderudit/032692ar cirque moraines that lie up to about 3 km outside Neoglacial moraines. There is DOI: https://doi.org/10.7202/032692ar considerable uncertainty as to the ages of the outer moraines and whether or not they are age-equivalent from range to range. The variety of assigned See table of contents radiocarbon ages found in the literature may be partly due to some authors' use of minimum-limiting dates as near-absolute dates, and use of dates that cannot be definitely related to the deposits in question. With one possible Publisher(s) exception, all the dated moraines described in the literature could be as old as the type Temple Lake moraine of Wyoming which has a minimum age of about Les Presses de l'Université de Montréal 11,400 yrs BP based on a recently obtained radiocarbon date. Nearly all paleoecological proxy data from the North American Cordillera, generally ISSN derived from continuous sedimentary records, suggest that early Holocene climate was warmer than at present. Global circulation models also suggest an 0705-7199 (print) early Holocene thermal maximum in the Cordillera, probably due to 1492-143X (digital) Milankovitch forcing. For these reasons a proposal gaining popularity in the literature that widespread "Mesoglaciation" occurred in early Holocene time is Explore this journal premature. We hypothesize that most, if not all, of the moraines in question are correlative and date from Late Pleistocene time. Cite this article Thompson Davis, P. & Osborn, G. (1987). Age of Pre-Neoglacial Cirque Moraines in the Central North American Cordillera. Géographie physique et Quaternaire, 41(3), 365–375. https://doi.org/10.7202/032692ar Tous droits réservés © Les Presses de l'Université de Montréal, 1987 This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ Géographie physique et Quaternaire, 1987, vol. XLI, n° 3, p. 365-375, 4 fig., 3 tabl. AGE OF PRE-NEOGLACIAL CIRQUE MORAINES IN THE CENTRAL NORTH AMERICAN CORDILLERA* P. Thompson DAVIS and Gerald OSBORN, Department of Natural Sciences, Bentley College, Waltham, Massachusetts 02254, U.S.A., and Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4. ABSTRACT In the western mountains of RÉSUMÉ L'âge des moraines de cirques ZUSAMMENFASSUNG Datierung der the United States and Canada are pre- pré-néoglaciaires du centre de la Cordillère pràneoglazialen Morànen im zentralen Nor- Neoglacial cirque moraines that lie up to nord-américaine. Dans les montagnes de den der amerikanischen Kordilleren. In den about 3 km outside Neoglacial moraines. l'ouest des États-Unis et du Canada se westlichen Bergen der Vereinigten Staaten There is considerable uncertainty as to the trouvent des moraines de cirque qui s'éten­ und Kanadas gibt es prâneoglaziale Hoch- ages of the outer moraines and whether or dent jusqu'à quelque 3 km des moraines talmorânen, die sich bis zu ungefàhr 3 km not they are age-equivalent from range to néoglaciaires. On connaît mal l'âge de ces auBerhalb der neoglazialen Morânen beo- range. The variety of assigned radiocarbon moraines externes et on ignore s'il concor­ bachten lassen. Es besteht eine betrâcht- ages found in the literature may be partly de d'une chaîne à l'autre. La grande diver­ liche UngewiBheit, was das Alter der âuBe- due to some authors' use of minimum-limit­ sité des âges au radiocarbone que l'on ren Morànen betrifft, und ob sie von Stufe ing dates as near-absolute dates, and use trouve dans la littérature relève probable­ zu Stufe gleichaltrig sind oder nicht. Die in of dates that cannot be definitely related to ment en partie du fait que certains auteurs Verôffentlichungen vorgefundene Ver- the deposits in question. With one possible considèrent les dates minimales comme schiedenheit der Radiokarbondatierungen exception, all the dated moraines described des dates significatives ou exploitent des mag zum Teil darauf zurùckzufùhren zu in the literature could be as old as the type dates qui ne peuvent pas être parfaitement sein, daB manche Autoren die Minimal- Temple Lake moraine of Wyoming which attribuées aux dépôts étudiés. Toutes les grenzwerte als nahezu absolute Werte has a minimum age of about 11,400 yrs BP moraines, sauf peut-être l'une d'entre elles, benutzen und sich auf Daten stùtzen, die based on a recently obtained radiocarbon pourraient être aussi vieilles que la moraine nicht einwandfrei zu den betreffenden Ab- date. Nearly all paleoecological proxy data de référence de Temple Lake, au Wyo­ lagerungen in Beziehung gesetzt werden from the North American Cordillera, gener­ ming, dont l'âge minimal est de 11 400 BP kônnen. Mit einer môglichen Ausnahme ally derived from continuous sedimentary selon une datation au radiocarbone récen­ kônnen all in den Verôffentlichungen records, suggest that early Holocene cli­ te. Presque toutes les données paléoécolo­ beschriebenen datierten Morànen so alt mate was warmer than at present. Global giques indirectes trouvées dans la Cordillè­ sein wie der Typus der Temple-Lake- circulation models also suggest an early re nord-américaine, qui proviennent Moràne von Wyoming, welche ein Mini- Holocene thermal maximum in the Cor­ généralement de séquences sédimentai- malalter von ungefàhr 11 400 BP. hat, dillera, probably due to Milankovitch forc­ res, démontrent que le climat au début de gestùtzt auf eine neuere Radiokarbon- ing. For these reasons a proposal gaining l'Holocène était plus chaud que mainte­ datierung. Fast aile palàoôkologischen popularity in the literature that widespread nant. Les modèles de circulation générale Proxy-Datierungen von den nordamerika- "Mesoglaciation" occurred in early Holo­ laissent également croire que la Cordillère nischen Kordilleren, die im allgemeinen cene time is premature. We hypothesize a connu un maximum thermique au début aus kontinuierlichen Sediment-Aufzei- that most, if not all, of the moraines in ques­ de l'Holocène. Pour toutes ces raisons, chnungen abgeleitet sind, lassen anneh- tion are correlative and date from Late l'hypothèse selon laquelle une mésoglacia­ men, daB das Klima im frùhen Holozàn Pleistocene time. tion répandue se serait produite au début warmer war als in der Jetztzeit. Globale Zir- de l'Holocène est pour le moins prématu­ kulationsmodelle legen auch ein ther- rée. Les auteurs croient plutôt que la plus misches Maximum in den Kordilleren im grande partie, sinon toutes les moraines frùhen Holozàn nahe, welches wahrschein- dont il est question ici, sont corrélatives et lich durch den Milankovitch-Effekt hervor- datent du Pleistocene supérieur. gerufen wurde. Aus ail diesen Grùnden ist eine Interpretation, die in den Verôffent­ lichungen immer populàrer wird, wohl voreilig, daB im frùhen Holozàn eine aus- gedehnte "Mesoglaziation" stattfand. Wir stellen die Hypothèse auf, daB die meisten wenn nicht gar aile betreffenden Morânen zusammenhângen und aus dem spàten Pleistozàn stammen. * Contribution du premier symposium de la CANQUA, sous la direction de René W. Barendregt. 366 PT. DAVIS and G. OSBORN INTRODUCTION TABLE I In numerous mountain ranges of western North America, Pre-Neoglacial Cirque Moraines some moraines lie up to about 3 km beyond more obvious and almost always present Neoglacial (post-Altithermal) moraines. These outer moraines represent depressions in BRITISHCOLUMBIA equilibrium-line altitudes up to about 100 m below Neogla­ 1. Mt. Tatlow, Coast Ranges (Ricker, 1983) cial values. The moraines are known in some cases, and in­ 2. Shuswap Highland (Duford and Osborn, 1978) ferred in others, to be early Holocene or older in age, and 5. Purcell Mountains (Osborn, unpubl.) 6. Kokanee Park, Selkirks (Osborn, unpubl.) are commonly designated only as "pre-Altithermal" (e.g., 7. Elk valley (Ferguson, 1978) CURREY, 1974). There is considerable uncertainty as to the specific age(s) of these moraines and whether or not ALBERTA 3. Jasper National Park they are equivalent in age from range to range (DAVIS, (Luckman and Osborn, 1979) 4. Banff National Park (Luckman and Osborn, 1979) 1984). 8. Highwood Pass (Gardner et al., 1983) This paper seeks to establish some order from the confu­ 9. Waterton Lakes National Park (Osborn, 1985) sion concerning distribution and ages of pre-Neoglacial cir­ MONTANA que moraines in the Cordillera of the conterminus United 10. Glacier National Park (Osborn, 1985) States and adjacent Canada. We (1) review the available 19. Eastern Tobacco Root Range (Hall and Heiny, 1983) radiocarbon ages and show that few can be closely related 22. Beartooth Mountains (Graf, 1971) to the ice advances they supposedly date, (2) review theo­ WASHINGTON retical paleoclimatic and proxy climatic data, and (3) con­ 11. Mt. Baker (Easterbrook and Burke, clude that the early Holocene was not a likely time for even 1972; Fuller era/., 1983) a minor glacial advance in the North American Cordillera. 12. Glacier Peak (Beget, 1981,1983) 13. Enchantment Lakes (Waitt efa/., 1982) The conventional Holocene/late Pleistocene boundary of 14. Mt. Rainier (Crandell and Miller, 1974) 10,000 yrs BP is used in this paper. We use the terms "Al- OREGON tithermal" and "Hypsithermal" interchangeably to mean 15.
Load more

Recommended publications
  • The Conservation of Hardwoods and Associated Wildlife in the Cbfwcp Area in Southeastern British Columbia
    THE CONSERVATION OF HARDWOODS AND ASSOCIATED WILDLIFE IN THE COLUMBIA BASIN CBFWCP AREA IN SOUTHEASTERN FISH & WILDLIFE BRITISH COLUMBIA COMPENSATION PROGRAM PREPARED BY Bob Jamieson, Everett Peterson, Merle Peterson, and Ian Parfitt FOR Columbia Basin Fish & Wildlife Compensation Program May 2001 www.cbfishwildlife.org THE CONSERVATION OF HARDWOODS AND ASSOCIATED WILDLIFE IN THE CBFWCP AREA IN SOUTHEASTERN BRITISH COLUMBIA. Prepared for: THE COLUMBIA BASIN FISH AND WILDLIFE COMPENSATION PROGRAM 333 Victoria St., Nelson, B.C. V1L 4K3 By: Bob Jamieson BioQuest International Consulting Ltd. Everett Peterson and Merle Peterson Western Ecological Services Ltd. Ian Parfitt GIS Coordinator, Columbia Basin Fish and Wildlife Compensation Program Note on the organization of this report: The appendices to this report are included on an attached CD-ROM. Maps showing the distribution of hardwoods (1:250,000 scale) in each Forest District are included as ADOBE pdf files. The hardwood data, in ARCINFO format, are available at the CBFWCP office in Nelson. Age class and cover categories by Forest District, Landscape unit and species are provided in Excel spreadsheets. Citation: Jamieson, B., E.B. Peterson, N.M. Peterson and I. Parfitt. 2001. The conservation of hardwoods and associated wildlife in the CBFWCP area in southeastern British Columbia. Prepared for: Columbia Basin Fish and Wildlife Compensation Program, Nelson, B.C. By: BioQuest International Consulting Ltd., Western Ecological Services Ltd. and I. Parfitt. 98p. Contacts: Bob Jamieson BioQuest International Consulting Ltd. Box 73, Ta Ta Creek, B.C. VOB 2HO Phone: 250-422-3322 E-mail: [email protected] Everett and Merle Peterson Western Ecological Services Ltd.
    [Show full text]
  • Two Contrasting Phanerozoic Orogenic Systems Revealed by Hafnium Isotope Data William J
    ARTICLES PUBLISHED ONLINE: 17 APRIL 2011 | DOI: 10.1038/NGEO1127 Two contrasting Phanerozoic orogenic systems revealed by hafnium isotope data William J. Collins1*(, Elena A. Belousova2, Anthony I. S. Kemp1 and J. Brendan Murphy3 Two fundamentally different orogenic systems have existed on Earth throughout the Phanerozoic. Circum-Pacific accretionary orogens are the external orogenic system formed around the Pacific rim, where oceanic lithosphere semicontinuously subducts beneath continental lithosphere. In contrast, the internal orogenic system is found in Europe and Asia as the collage of collisional mountain belts, formed during the collision between continental crustal fragments. External orogenic systems form at the boundary of large underlying mantle convection cells, whereas internal orogens form within one supercell. Here we present a compilation of hafnium isotope data from zircon minerals collected from orogens worldwide. We find that the range of hafnium isotope signatures for the external orogenic system narrows and trends towards more radiogenic compositions since 550 Myr ago. By contrast, the range of signatures from the internal orogenic system broadens since 550 Myr ago. We suggest that for the external system, the lower crust and lithospheric mantle beneath the overriding continent is removed during subduction and replaced by newly formed crust, which generates the radiogenic hafnium signature when remelted. For the internal orogenic system, the lower crust and lithospheric mantle is instead eventually replaced by more continental lithosphere from a collided continental fragment. Our suggested model provides a simple basis for unravelling the global geodynamic evolution of the ancient Earth. resent-day orogens of contrasting character can be reduced to which probably began by the Early Ordovician12, and the Early two types on Earth, dominantly accretionary or dominantly Paleozoic accretionary orogens in the easternmost Altaids of Pcollisional, because only the latter are associated with Wilson Asia13.
    [Show full text]
  • Climate Change May Induce Connectivity Loss and Mountaintop Extinction in Central American Forests ✉ Lukas Baumbach 1 , Dan L
    ARTICLE https://doi.org/10.1038/s42003-021-02359-9 OPEN Climate change may induce connectivity loss and mountaintop extinction in Central American forests ✉ Lukas Baumbach 1 , Dan L. Warren 2, Rasoul Yousefpour1 & Marc Hanewinkel 1 The tropical forests of Central America serve a pivotal role as biodiversity hotspots and provide ecosystem services securing human livelihood. However, climate change is expected to affect the species composition of forest ecosystems, lead to forest type transitions and trigger irrecoverable losses of habitat and biodiversity. Here, we investigate potential impacts of climate change on the environmental suitability of main plant functional types (PFTs) across Central America. Using a large database of occurrence records and physiological data, 1234567890():,; we classify tree species into trait-based groups and project their suitability under three representative concentration pathways (RCPs 2.6, 4.5 and 8.5) with an ensemble of state-of- the-art correlative modelling methods. Our results forecast transitions from wet towards generalist or dry forest PFTs for large parts of the study region. Moreover, suitable area for wet-adapted PFTs is projected to latitudinally diverge and lose connectivity, while expected upslope shifts of montane species point to high risks of mountaintop extinction. These findings underline the urgent need to safeguard the connectivity of habitats through biological corridors and extend protected areas in the identified transition hotspots. 1 Chair of Forestry Economics and Forest Planning,
    [Show full text]
  • (1987): "Tectonomagmatic Evolution of Cenozoic Extension in the North American Cordillera"
    Downloaded from http://sp.lyellcollection.org/ by Frances J Cooper on January 21, 2013 Geological Society, London, Special Publications Tectonomagmatic evolution of Cenozoic extension in the North American Cordillera Brian P. Wernicke, Philip C. England, Leslie J. Sonder and Robert L. Christiansen Geological Society, London, Special Publications 1987, v.28; p203-221. doi: 10.1144/GSL.SP.1987.028.01.15 Email alerting click here to receive free e-mail alerts when service new articles cite this article Permission click here to seek permission to re-use all or request part of this article Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection Notes © The Geological Society of London 2013 Downloaded from http://sp.lyellcollection.org/ by Frances J Cooper on January 21, 2013 Tectonomagmatic evolution of Cenozoic extension in the North American Cordillera B.P. Wernicke, R.L. Christiansen, P.C. England & L.J. Sonder SUMMARY: The spatial and temporal distributions of Cenozoic extension and magmatism in the Cordillera suggest that the onset of major crustal extension at a particular latitude was confined to a relatively narrow belt (< 100 km, pre-extension) and followed the onset of intermediate and silicic magmatism by no more than a few million years. Extension began in early Eocene time in southern British Columbia, northern Washington, Idaho and Montana. Farther S, extension began at about the Eocene- Oligocene boundary in the Great Basin and slightly later in the Mojave-Sonora Desert region. The intervening area, at the latitude of Las Vegas, remained quiescent until mid- Miocene time. Compositional and isotopic characteristics of most pre-Miocene magmas are consistent with their containing major components of melted continental crust.
    [Show full text]
  • 2009-2013 Jasper National Park Caribou Progress Report
    2009-2013 Jasper National Park Caribou Progress Report Lalenia Neufeld Mark Bradley Saakje Hazenberg With contributions from: John Wilmshurst Shelley Bird Colleen Arnison Amy Flasko Executive Summary Woodland caribou (Rangifer tarandus caribou) range throughout North America has retracted northward and many populations across Canada are in decline. The Committee on the Status of Endangered Wildlife in Canada has defined Canadian populations as Endangered (Atlantic- Gaspésie), Threatened (Southern Mountain and Boreal), Special Concern (Northern Mountain), and Not at Risk (Newfoundland) (Thomas and Gray 2002). Woodland caribou in Jasper National Park belong to the Threatened Southern Mountain Population. Phase I of the Jasper Woodland Caribou Recovery Action Plan was implemented in 2005. Its larger goals were to increase awareness of woodland caribou and recommend a suite of actions to mitigate factors contributing to caribou decline. Implementation of recovery actions began in the 2005-2006 fiscal year, shortly after the Plan was signed by Parks Canada. In 2007, as a follow-up to the Action Plan, the Mountain Parks Caribou Coordinating Committee initiated development of a Conservation Strategy for caribou in the mountain national parks. The strategy is intended to contribute towards meeting Parks Canada’s obligations under Canada's National Parks Act and the Species at Risk Act. Key direction for caribou recovery and sustainability, which is aligned with Parks Canada’s mandate of ecological integrity, public education, and visitor experience, is being formulated with the incorporation of the results from the public and Aboriginal consultations recently completed into the management plan. Required knowledge for informed management relies on the caribou monitoring program, the results of which are reported herein.
    [Show full text]
  • Brief Overview of North American Cordilleran Geology by Cin-Ty Lee Topography Map of North America
    Brief overview of North American Cordilleran geology by Cin‐Ty Lee Note: make sure to take notes as I will talk or sketch on the board many things that are not presented explicitly in these slides Topography map of North America Topography map How does the NthNorth AiAmerican Cor dillera fit itinto a glbllobal contt?text? Dickinson 2004 P‐wave tomography: Seismic structure beneath western USA Burdick et al. 2008 Crustal provinces of North America (Laurentia) ‐Proterozoic and Archean terranes were already assembled by 1.6 Ga Hoffman, 1988 Crustal provinces in southwestern USA Hoffman, 1988 Bennett and DePaolo, 1987 Some examples of tectonic margins for your reference Dickinson and Snyder, 1978 1.1 Ga = Rodinia Super‐continent (Grenvillian age) Neo‐Proterozoic = Rodinia breaks up “western” margin of Laurentia represents a passive margin due to opening of the Panthalassan ocean 700‐400 Ma Western margin of Laurentia represents a passive margin Dickinson and Snyder, 1978 400‐250 Ma Passive margin is interrupted in Devonian times by the accretion of island arcs Antler and Sonoma orogenies Accretion of allochthonous terranes to the western margin of the NhNorth AiAmerican craton Antler/Sonoma orogenies result in the accretion of Paleozoic island arc terranes to western North America Permian Formation of Pangea “”“western” margin of NhNorth AiAmerica now didominate d by subduct ion zone 250‐50 Ma Subduction results in continued accretion of fringing island arcs and the generation of continental magmatic arcs Sierra Nevada batholith Sevier and
    [Show full text]
  • Mount Robson Provincial Park, Draft Background Report
    Mount Robson Provincial Park Including Mount Terry Fox & Rearguard Falls Provincial Parks DRAFT BACKGROUND REPORT September, 2006 Ministry of Environment Ministry of Environment BC Parks Omineca Region This page left blank intentionally Acknowledgements This Draft Background Report for Mount Robson Provincial Park was prepared to support the 2006/07 Management Plan review. The report was prepared by consultant Juri Peepre for Gail Ross, Regional Planner, BC Parks, Omineca Region. Additional revisions and edits were performed by consultant Leaf Thunderstorm and Keith J. Baric, A/Regional Planner, Omineca Region. The report incorporates material from several previous studies and plans including the Mount Robson Ecosystem Management Plan, Berg Lake Corridor Plan, Forest Health Strategy for Mount Robson Provincial Park, Rare and the Endangered Plant Assessment of Mount Robson Provincial Park with Management Interpretations, the Robson Valley Land and Resource Management Plan, and the BC Parks website. Park use statistics were provided by Stuart Walsh, Rick Rockwell and Robin Draper. Cover Photo: Berg Lake and the Berg Glacier (BC Parks). Mount Robson Provincial Park, Including Mount Terry Fox & Rearguard Falls Provincial Parks: DRAFT Background Report 2006 Table of Contents Introduction .....................................................................................................................................................1 Park Overview.................................................................................................................................................1
    [Show full text]
  • The Paleoecological Record of 6 Ka BP Climate in the Canadian Prairie
    Document generated on 09/25/2021 5:12 a.m. Géographie physique et Quaternaire The Paleoecological Record of 6 ka BP Climate in the Canadian Prairie Provinces Données paléoécologiques sur le climat des provinces des Prairies à 6 ka BP Palaoökologische Belege über das Klima in den kanadischen Prärie-Provinzen um 6 ka v.u.Z. Robert E. Vance, Alwynne B. Beaudoin and Brian H. Luckman La paléogéographie et la paléoécologie d’il y a 6000 ans BP au Canada Article abstract Paleogeography and Paleoecology of 6000 yr BP in Canada Synthesis of available paleoecological studies in the Prairie provinces of Volume 49, Number 1, 1995 Canada indicates that although the peak in postglacial aridity that characterized early Holocene climate of the western foothills and plains had URI: https://id.erudit.org/iderudit/033031ar passed, conditions remained warmer and drier than present throughout the DOI: https://doi.org/10.7202/033031ar region ca. 6000 yr BP Compared to today, treeline elevations were higher and alpine glaciers were reduced in size in the Rocky Mountains, lake levels were lower over much of the Interior Plains, and the grassland and boreal forest See table of contents ecozones extended north of their present positions. Forest fires were more prevalent ca. 6000 yr BP than they are today, aiding westward migration of jack pine (Pinus banksiana) through the boreal forest and increasing the area Publisher(s) occupied by grassland in boreal and montane forest regions. Attempts to quantify the magnitude of 6 ka temperature and precipitation differences have Les Presses de l'Université de Montréal produced variable results, but suggest that mean annual temperature was 0.50°C to 1.50°C higher than today (summer temperature may have been up to ISSN 3°C higher) and mean annual precipitation was reduced by 65 mm (or summer 0705-7199 (print) precipitation was reduced by 50 mm), compared to present.
    [Show full text]
  • Helens Volcanic Eruptions Had Upon Prehistoric Populations in The
    AN ABSTRACT OF THE THESIS OF Loren G. Davis for the degree of Master of Arts inInterdisciplinary Studies in Anthropology Geography and Soil Science, presented on May 18,1995. Title: Volcanism, Climate Change. and Prehistoric CulturalSuccession in Southern Washington and North-Central Idaho. Abstract approved: /; David R. Brauner The cultural influence of volcanic eruptions has beenemphasized in the archaeological literature. However, the largereffects that Mount St. Helens volcanic eruptions had upon prehistoricpopulations in the Pacific Northwest is not understood. This thesis asks questionsof the archaeological and paleoenvironmental record of the PacificNorthwest to assess the degree of influence Late Pleistocene and Holocene volcaniceruptions of Mount St. Helens had upon the cultural record of human existencein southern Washington and north-central Idaho. The record of eruptiveactivity at Mount St. Helens is reviewed and its tephra lobesmapped from reports of pyroclastic identification in the Pacific Northwest and westernCanada, to gain a temporal and spatial understanding of the eruptions.A general systemic model is presented to identify the factorsresponsible for the deposition, removal and alteration of tephra. Thismodel illustrates the complexity of tephrostratigraphic deposition, and increasesthe awareness of its residence within archaeological sites. Several setsof paleoenvironmental data are correlated with archaeological records ofhuman occupation in southern Washington and north-central Idaho,including records of pollen fluctuation,
    [Show full text]
  • The American Cordillera: a Long Journey Through Time & Space
    The American Cordillera: A Long Journey Through Time & Space Part III:The North American Taphrogen Lecture 25: April 25, G. Zandt An overview of the collapse of the American Cordillera 1 Some of the Big Questions • What caused the extreme inboard migration of deformation and magmatism during the Laramide? [Flat Slab] • What caused the mid-Tertiary extensional collapse and ignimbrite flareup? [Slab Rollback] • Why is the extension and associated magmatisn separated into two domains with different spatial-temporal evolutions? • How did the Colorado Plateau escape significant deformation and magmatism during both periods? Major questions we want to address today. 2 North American Cordillera Topography is the first-order expression of orogeny, and high topography extends half way across the continent (>1000 km). And it remains high despite significant extension which normally leads to subsidence. 3 Western US today We will follow Dickinson (2002) in this review of the Cordilleran taphrogen. He follows Sengor in dividing the Basin and Range taphrogen into the Numic and Piman subtaphrogens. Black bodies are core complexes with arrows indicating direction of vergence (movement of upper plate). We will focus today on the relationship between the subtaphrogens and the Colorado Plateau–Laramide Rocky Mountains. Dickinson, W. R., The Basin and Range Province as a Composite Extensional Domain, Int. Geol. Rev., 44, 1-38, 2002. 4 The tectonic evolution of the Cordillera can be divided into 7 frames (Coney): 1) Formation of the continental margin in late Precambrian time and development of the Cordilleran passive margin. 2) Mid- to late Paleozoic brief orogenic events (Antler, Ancestral Rockies, Sonoma orogenies).
    [Show full text]
  • Climate Change in Central America and Mexico: Regional Climate Model Validation and Climate Change Projections
    Clim Dyn DOI 10.1007/s00382-011-1099-9 Climate change in Central America and Mexico: regional climate model validation and climate change projections Ambarish V. Karmalkar • Raymond S. Bradley • Henry F. Diaz Received: 6 January 2010 / Accepted: 10 May 2011 Ó Springer-Verlag 2011 Abstract Central America has high biodiversity, it har- the form of orographic precipitation show significant bors high-value ecosystems and it’s important to provide decreases in precipitation in the dry season. Projected cli- regional climate change information to assist in adaptation matic changes can have detrimental impacts on biodiver- and mitigation work in the region. Here we study climate sity as they are spatially similar, but far greater in change projections for Central America and Mexico using magnitude, than those observed during the El Nin˜o events a regional climate model. The model evaluation shows its in recent decades that adversely affected species in the success in simulating spatial and temporal variability of region. temperature and precipitation and also in capturing regio- nal climate features such as the bimodal annual cycle of keywords Regional climate change Á Biodiversity Á precipitation and the Caribbean low-level jet. A variety of Central America climate regimes within the model domain are also better identified in the regional model simulation due to improved resolution of topographic features. Although, the model 1 Introduction suffers from large precipitation biases, it shows improve- ments over the coarse-resolution driving model in simu- The Mexican and Central American landmass has consid- lating precipitation amounts. The model shows a dry bias erable topographic relief, which implies the existence of in the wet season and a wet bias in the dry season sug- large gradients in many critical climate variables such as gesting that it’s unable to capture the full range of pre- temperature, precipitation, humidity, and wind.
    [Show full text]
  • Cross Cordillera Field Trip Guide
    GS Field Trip: End of Summer 2016 GS191/291 (Miller, no Klemperer (went to Tibet), Lund Snee, Gottlieb) Listed as Fall Quarter class under Miller Crossing the Cordillera: From the Colorado Plateau to the Sierra Nevada Field trip (1 credit), advanced ugrad to grad level, but all welcome Dates: September 15 to Sept. 21 (T.A. Eric Gottlieb) There is unprecedented controversy about the paleo-topographic evolution of the western United States. How thick and how high was the crust following Mesozoic crustal shortening? Did the region between the Sierra Nevada and the Colorado Plateau form a high plateau, the Nevadaplano, underlain by 60 km thick crust? When did this thick crust collapse to its present crustal thickness of only 30 km? Did extension happen as a result of, during and shortly after crustal thickening? Or did extension take place only in the Miocene, during formation of Basin and Range topography? How much stretching is represented by Basin and Range faulting? Can it account for thinning of crust by 30 km? This field trip will provide you with an exceptional opportunity to view a complete cross-section of the geology of the southern part of the North American Cordillera, from the undeformed Colorado Plateau on the east to Mount Whitney and the Mesozoic Sierra Nevada arc on the west. With these big questions in mind, our stops will focus on Mesozoic shortening, when the Cordillera is believed to have looked like the Andes, and on younger extensional structures (including a variety faults in Death Valley), with a critical view and discussion of age, geometry and offset along normal faults.
    [Show full text]