DOCSLIB.ORG

Past Climate Changes and Permafrost Depth at the Lake El'gygytgyn Site: Implications from Data and Thermal Modeling

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Past Climate Changes and Permafrost Depth at the Lake El'gygytgyn Site: Implications from Data and Thermal Modeling Clim. Past, 9, 119–133, 2013 www.clim-past.net/9/119/2013/ Climate doi:10.5194/cp-9-119-2013 of the Past © Author(s) 2013. CC Attribution 3.0 License. Past climate changes and permafrost depth at the Lake El’gygytgyn site: implications from data and thermal modeling D. Mottaghy1, G. Schwamborn2, and V. Rath3 1Geophysica Beratungsgesellschaft mbH, Aachen, Germany 2Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany 3Department of Earth Sciences, Astronomy and Astrophysics, Faculty of Physical Sciences, Universidad Complutense de Madrid, Madrid, Spain Correspondence to: D. Mottaghy ([email protected]) Received: 6 July 2012 – Published in Clim. Past Discuss.: 16 July 2012 Revised: 12 December 2012 – Accepted: 13 December 2012 – Published: 22 January 2013 Abstract. This study focuses on the temperature field ob- perature, an estimate of steady-state conditions is possible, served in boreholes drilled as part of interdisciplinary sci- leading to a meaningful value of 14 ± 5 K for the post-glacial entific campaign targeting the El’gygytgyn Crater Lake in warming. The strong curvature of the temperature data in NE Russia. Temperature data are available from two sites: shallower depths around 60 m can be explained by a compar- the lake borehole 5011-1 located near the center of the lake atively large amplitude of the Little Ice Age (up to 4 K), with reaching 400 m depth, and the land borehole 5011-3 at the low temperatures prevailing far into the 20th century. Other rim of the lake, with a depth of 140 m. Constraints on per- mechanisms, like varying porosity, may also have an influ- mafrost depth and past climate changes are derived from ence on the temperature profile, however, our modeling stud- numerical simulation of the thermal regime associated with ies imply a major contribution from recent climate changes. the lake-related talik structure. The thermal properties of the subsurface needed for these simulations are based on labo- ratory measurements of representative cores from the qua- ternary sediments and the underlying impact-affected rock, 1 Introduction complemented by further information from geophysical logs ◦ 0 and data from published literature. The crater Lake El’gygytgyn in NE Russia (67 30 N, ◦ 0 The temperature observations in the lake borehole 5011-1 172 5 E, 492 m above sea level) was formed by an Aster- are dominated by thermal perturbations related to the drilling oid impact 3.6 Myr ago (Fig. 1). Since it is believed to have process, and thus only give reliable values for the lowermost never been covered by ice during the glacial cycles since value in the borehole. Undisturbed temperature data recorded then, it provides the unique possibility to investigate Arctic over more than two years are available in the 140 m deep climate and environmental changes back to the impact. For land-based borehole 5011-3. The analysis of these observa- this reason, in 2008/2009 an interdisciplinary drilling cam- tions allows determination of not only the recent mean an- paign targeted this area. General information on this Interna- nual ground surface temperature, but also the ground sur- tional Continental Drilling Program (ICDP) project is given face temperature history, though with large uncertainties. Al- by Melles et al. (2011), while the most important paleocli- though the depth of this borehole is by far too insufficient for matological results were published by Melles et al. (2012). a complete reconstruction of past temperatures back to the In the course of the project, boreholes were drilled at Last Glacial Maximum, it still affects the thermal regime, and two sites, one near the deepest part of the lake (ICDP thus permafrost depth. This effect is constrained by numer- site 5011-1), and the other on land close to its shore- ical modeling: assuming that the lake borehole observations line (ICDP site 5011-3). From borehole 5011-1, 315 m of are hardly influenced by the past changes in surface air tem- sediment cores were retrieved, complemented by 200 m from the underlying volcanic bedrock, while from 5011-3 a Published by Copernicus Publications on behalf of the European Geosciences Union. 120 D. Mottaghy et al.: Lake El’gygytgyn site: thermal modeling a Siberia Alaska Fig. 2. Basin scheme of the Lake El’gygytgyn site with the digital elevation model in the background. The numerical model is based on this conceptual model by Melles et al. (2011). b crater rim 2007; Lemke et al., 2007; Serreze et al., 2007; Miller et al., 2010a,b; Serreze and Barry, 2011). When studying heat transfer in the Earth’s upper crust, the upper boundary condition of heat transport is determined by the local climatic conditions. The variations of this bound- 5011-1 ary condition induces a transient signal which diffuses into 5011-3 the subsurface. Thus, ground temperatures may be seen as an Lake El`gygytgyn archive of past climate signals. Reconstructing past changes is of major interest, since one of the most important com- ponents of climatic change is the variation of temperature at the Earth’s surface. However, the diffusive character implies that the older the signal is, the more it is attenuated, with N a corresponding larger uncertainty in magnitude and timing. Analyzing the variation of temperature with depth, past fluc- 18 km tuations at the Earth’s surface can be reconstructed to a cer- tain extent (see, e.g. the recent review by Gonzalez-Rouco´ Fig. 1. (a) Geographic position of the El’gygytgyn Crater in NE et al., 2009, and the references therein). This reconstruc- Russia (red box). (b) A Landsat image showing the crater (dotted tion can be performed by numerical forward modeling with line) and the drill sites 5011-1 and 5011-3. models of varying complexity, or inverse methods in the nar- row sense (amongst others, Shen and Beck, 1991; Beltrami and Mareschal, 1991; Beck et al., 1992; Rath and Mottaghy, 2007). A prerequisite for such a reconstruction is the avail- 141.5-m-long permafrost core composed of frozen deposits ability of sufficient data, the most relevant of which is tem- was recovered (Fig. 2). perature observations. Here, we limit ourselves to forward In this paper, we focus on the characterization of the ther- modeling for determining the present-day temperature pro- mal field beneath and around the lake, studying the influence file, because the available temperature data is not sufficient of variations of thermal properties and past ground surface for a reliable reconstruction by inversion of the ground sur- temperature changes using numerical modeling techniques face temperature history (GSTH) at the study area. Neverthe- (e.g. Osterkamp and Gosink, 1991; Galushkin, 1997; Mot- less, we propose that the combination of forward modeling taghy and Rath, 2006; Holmen´ et al., 2011). In the recent and sensitivity studies allow some meaningful statements to years, the impact of climate change on permafrost forma- be made concerning the local GSTH. tion and evolution has become a particular subject of inter- As our approach relies on forward modeling, we must as- est. The understanding of the response of permafrost regimes sume a certain GSTH entering the simulations. In particular, to transient changes in surface temperatures is a key issue it has been shown that the amplitude of the Last Glacial Max- regarding the prediction of the influence of global warm- imum (LGM) and the following warming from Pleistocene to ing on permafrost areas (amongst many others, Saito et al., Holocene influence the temperature distribution at all depths Clim. Past, 9, 119–133, 2013 www.clim-past.net/9/119/2013/ D. Mottaghy et al.: Lake El’gygytgyn site: thermal modeling 121 0 0 T 5.5 ºC 1 T2 100 T3 T4 water column 50 borehole 5011-3 T5 200 z(m) 300 100 25.1 ºC lake sediments total depth (m) 400 T avg 150 -7.5 -7 -6.5 -6 -5.5 -5 -4.5 -4 500 T (°C) 0 Breccia 2 0102030 temperature (ºC) 4 Fig. 4. Temperature logs in borehole ICDP site 5011-1. T5 is the 6 most reliable, and thus is used for estimating the temperature gradi- 8 ent (data by ICDP-OSG, 2009). 10 z(m) julian days 12 15 165 315 matic changes affect the ground surface temperature (Mot- 14 45 195 345 taghy and Rath, 2006; Rath and Mottaghy, 2007). This im- 75 225 365 plies that the reconstruction of past temperatures by forward 16 105 255 or inverse methods must include these processes. 18 -5135 285 0 20 -15 -10 -5 0 5 10 2 Available data T (°C) The data used for this study originate from the aforemen- Fig. 3. Selection of the temperatures logs in the permafrost borehole 5011-3 during the year 2010. Note the different scales in the two tioned boreholes, one in the deepest part of the lake (ICDP panels. site 5011-1, depth 517 m below lake bottom), and one close to its shoreline (ICDP site 5011-3, depth 140 m below sur- face). Their locations are shown in Fig. 2, which provides a schematic sketch of the basin. Our investigations rely on up to the surface (Rath et al., 2012). In the arctic region the (a) temperature measurements in both boreholes; and (b) de- values of this amplitude are not well known, but the avail- termination of thermal properties from laboratory measure- able data suggest a 18 ± 7 K cooler mean temperature than ments on cores and γ -ray logging in borehole 5011-1. today (Miller et al., 2010a,b). There have been some efforts The temperature data from the lake borehole ICDP site to determine the spatial distribution of this parameter (De- 5011-1 do not represent steady-state conditions.
Load more

Recommended publications
  • The Future of Continental Scientific Drilling U.S
    THE FUTURE OF CONTINENTAL SCIENTIFIC DRILLING U.S. PERSPECTIVE Proceedings of a workshop | June 4-5, 2009 | Denver, Colorado DOSECC WORKSHOP PUBLICATION 1 Front Cover: Basalts and rhyolites of the Snake River Plain at Twin Falls, Idaho. Project Hotspot will explore the interaction of the Yellowstone hotspot with the continental crust by sampling the volcanic rocks underlying the plain. Two 1.5 km holes will penetrate both the surficial basalt and the underlying rhyolite caldera-fill and outflow depos- its. A separate drill hole will explore the paleoclimate record in Pliocene Lake Idaho in the western Snake River Plain. In addition to the understanding of continent-mantle interaction that develops and the paleoclimate data collected, the project will study water-rock interaction, gases emanating from the deeper curst, and the geomicro- biology of the rocks of the plain. Once scientific objectives and set, budgets are developed, and funding is granted, successful implementation of projects requires careful planning, professional on-site staff, appropriate equip- ment, effective logistics, and accurate accounting. Photo by Tony Walton The authors gratefully acknowledge support of the National Science Foundation (NSF EAR 0923056 to The University of Kansas) and DOSECC, Inc. of Salt Lake City, Utah. Anthony W. Walton, University of Kansas, Lawrence, Kansas Kenneth G. Miller, Rutgers University, New Brunswick, N.J. Christian Koeberl, University of Vienna, Vienna, Austria John Shervais, Utah State University, Logan, Utah Steve Colman, University of Minnesota, Duluth, Duluth, Minnesota edited by Cathy Evans. Stephen Hickman, US Geological Survey, Menlo Park, California covers and design by mitch favrow. Will Clyde, University of New Hampshire, Durham, New Hampshire document layout by Pam Lerow and Paula Courtney.
    [Show full text]
  • Terrestrial Impact Structures Provide the Only Ground Truth Against Which Computational and Experimental Results Can Be Com­ Pared
    Ann. Rev. Earth Planet. Sci. 1987. 15:245-70 Copyright([;; /987 by Annual Reviews Inc. All rights reserved TERRESTRIAL IMI!ACT STRUCTURES ··- Richard A. F. Grieve Geophysics Division, Geological Survey of Canada, Ottawa, Ontario KIA OY3, Canada INTRODUCTION Impact structures are the dominant landform on planets that have retained portions of their earliest crust. The present surface of the Earth, however, has comparatively few recognized impact structures. This is due to its relative youthfulness and the dynamic nature of the terrestrial geosphere, both of which serve to obscure and remove the impact record. Although not generally viewed as an important terrestrial (as opposed to planetary) geologic process, the role of impact in Earth evolution is now receiving mounting consideration. For example, large-scale impact events may hav~~ been responsible for such phenomena as the formation of the Earth's moon and certain mass extinctions in the biologic record. The importance of the terrestrial impact record is greater than the relatively small number of known structures would indicate. Impact is a highly transient, high-energy event. It is inherently difficult to study through experimentation because of the problem of scale. In addition, sophisticated finite-element code calculations of impact cratering are gen­ erally limited to relatively early-time phenomena as a result of high com­ putational costs. Terrestrial impact structures provide the only ground truth against which computational and experimental results can be com­ pared. These structures provide information on aspects of the third dimen­ sion, the pre- and postimpact distribution of target lithologies, and the nature of the lithologic and mineralogic changes produced by the passage of a shock wave.
    [Show full text]
  • Multivariate Statistic and Time Series Analyses of Grain-Size Data in Quaternary Sediments of Lake El’Gygytgyn, NE Russia
    Clim. Past, 9, 2459–2470, 2013 Open Access www.clim-past.net/9/2459/2013/ Climate doi:10.5194/cp-9-2459-2013 © Author(s) 2013. CC Attribution 3.0 License. of the Past Multivariate statistic and time series analyses of grain-size data in quaternary sediments of Lake El’gygytgyn, NE Russia A. Francke1, V. Wennrich1, M. Sauerbrey1, O. Juschus2, M. Melles1, and J. Brigham-Grette3 1University of Cologne, Institute for Geology and Mineralogy, Cologne, Germany 2Eberswalde University for Sustainable Development, Eberswalde, Germany 3University of Massachusetts, Department of Geosciences, Amherst, USA Correspondence to: A. Francke ([email protected]) Received: 14 December 2012 – Published in Clim. Past Discuss.: 14 January 2013 Revised: 20 September 2013 – Accepted: 3 October 2013 – Published: 5 November 2013 Abstract. Lake El’gygytgyn, located in the Far East Rus- glacial–interglacial variations (eccentricity, obliquity), and sian Arctic, was formed by a meteorite impact about 3.58 Ma local insolation forcing and/or latitudinal teleconnections ago. In 2009, the International Continental Scientific Drilling (precession), respectively. Program (ICDP) at Lake El’gygytgyn obtained a continu- ous sediment sequence of the lacustrine deposits and the up- per part of the impact breccia. Here, we present grain-size data of the past 2.6 Ma. General downcore grain-size varia- 1 Introduction tions yield coarser sediments during warm periods and finer The polar regions are known to play a crucial but not ones during cold periods. According to principal component yet well understood role within the global climate system analysis (PCA), the climate-dependent variations in grain- (Washington and Meehl, 1996; Johannessen et al., 2004), in- size distributions mainly occur in the coarse silt and very fluencing both the oceanic and the atmospheric circulation.
    [Show full text]
  • Central Ring Structure Identified in One of the World's Best-Preserved Impact
    Central ring structure identi®ed in one of the world's best-preserved impact craters A.C. Gebhardt F. Niessen Alfred Wegener Institute for Polar and Marine Research, Columbusstraûe, 27568 Bremerhaven, Germany C. Kopsch Alfred Wegener Institute for Polar and Marine Research, Telegrafenberg A43, 14473 Potsdam, Germany ABSTRACT Seismic refraction and re¯ection data were acquired in 2000 and 2003 to study the morphology and sedimentary ®ll of the remote El'gygytgyn crater (Chukotka, northeast- ern Siberia; diameter 18 km). These data allow a ®rst insight into the deeper structure of this unique impact crater. Wide-angle data from sonobuoys reveal a ®ve-layer model: a water layer, two lacustrine sedimentary units that ®ll a bowl-shaped apparent crater mor- phology consisting of an upper layer of fallback breccia with P-wave velocities of ;3000 m/s, and a lower layer of brecciated bedrock (velocities .3600 m/s). The lowermost layer shows a distinct anticline structure that, by analogy with other terrestrial and lunar cra- ters of similar size, can be interpreted as a central ring structure. The El'gygytgyn crater exhibits a well-expressed morphology that is typical of craters formed in crystalline target rocks. Keywords: impact crater, El'gygytgyn, lakes, seismic refraction, seismic re¯ection. INTRODUCTION (Belyi, 1998; Gurov et al., 1979a, 1979b). The Grette, 2006; Nolan et al., 2002) formed in- The El'gygytgyn crater, located in the Rus- Anadyr Mountains are part of the Okhotsk- side the crater (the crater and crater lake are sian Arctic, is one of the world's best- Chukotka Volcanic Belt, composed of Late not concentric; see Fig.
    [Show full text]
  • PDF Linkchapter
    Index [Italic page numbers indicate major references] A arsenic, 116, 143, 168 brecciation, shock, 225, 231 Ashanti crater, Ghana. See Bosumtwi Brent crater, Ontario, 321 Abitibi Subprovince, 305 crater, Ghana bromine, 137 Acraman depression, South Australia, A thy ris Broodkop Shear Zone, 180 211, 212, 218 gurdoni transversalis, 114 Budevska crater, Venus, 24 geochemistry, 216 hunanensis, 114 Bunyeroo Formation, 209, 210, 219, geochronology, 219 aubrite, 145 220, 221, 222 melt rock, 216, 218 augite, 159 Bushveld layered intrusion, 337 paleomagnetism, 219 Australasian strewn field, 114, 133, See also Acraman impact structure 134, 137, 138, 139, 140, 143, Acraman impact structure, South C 144, 146 Australia, 209 australite, 136, 141, 145, 146 Cabin-Medicine Lodge thrust system, Adelaid Geosyncline, 210, 220, 222 Austria, moldavites, 142 227 adularía, 167 Cabin thrust plate, 173, 225, 226, Aeneas on Dione crater, Earth, 24 227, 231, 232 aerodynamically shaped tektites, 135 B calcite, 112, 166 Al Umchaimin depression, western Barbados, tektites, 134, 139, 142, 144 calcium, 115, 116, 128 Iraq, 259 barium, 116, 169, 216 calcium oxide, 186, 203, 216 albite, 209 Barrymore crater, Venus, 44 Callisto, rings, 30 Algoman granites, 293 Basal Member, Onaping Formation, Cambodia, circular structure, 140, 141 alkali, 156, 159, 167 266, 267, 268, 271, 272, 273, Cambrian, Beaverhead impact alkali feldspar, 121, 123, 127, 211 289, 290, 295, 296, 299, 304, structure, Montana, 163, 225, 232 almandine-spessartite, 200 307, 308, 310, 311, 314 Canadian Arctic,
    [Show full text]
  • An Unusual Occurrence of Coesite at the Lonar Crater, India
    Meteoritics & Planetary Science 52, Nr 1, 147–163 (2017) doi: 10.1111/maps.12745 An unusual occurrence of coesite at the Lonar crater, India 1* 1 2 1 3 Steven J. JARET , Brian L. PHILLIPS , David T. KING JR , Tim D. GLOTCH , Zia RAHMAN , and Shawn P. WRIGHT4 1Department of Geosciences, Stony Brook University, Stony Brook, New York 11794–2100, USA 2Department of Geosciences, Auburn University, Auburn, Alabama 36849, USA 3Jacobs—NASA Johnson Space Center, Houston, Texas 77058, USA 4Planetary Science Institute, Tucson, Arizona 85719, USA *Corresponding author. E-mail: [email protected] (Received 18 March 2016; revision accepted 06 September 2016) Abstract–Coesite has been identified within ejected blocks of shocked basalt at Lonar crater, India. This is the first report of coesite from the Lonar crater. Coesite occurs within SiO2 glass as distinct ~30 lm spherical aggregates of “granular coesite” identifiable both with optical petrography and with micro-Raman spectroscopy. The coesite+glass occurs only within former silica amygdules, which is also the first report of high-pressure polymorphs forming from a shocked secondary mineral. Detailed petrography and NMR spectroscopy suggest that the coesite crystallized directly from a localized SiO2 melt, as the result of complex interactions between the shock wave and these vesicle fillings. INTRODUCTION Although there is no direct observation of nonshock stishovite in nature, a possible post-stishovite phase may High-Pressure SiO2 Phases be a large component of subducting slabs and the core- mantle boundary (Lakshtanov et al. 2007), and Silica (SiO2) polymorphs are some of the simplest stishovite likely occurs in the deep mantle if basaltic minerals in terms of elemental chemistry, yet they are slabs survive to depth.
    [Show full text]
  • Depadmentoffichems &Oceans
    ISSN 0704-3716 91-009 83 / Canadian Translation of Fisheries and Aquatic Sciences No. 5510 The current status of research on salmonid fishes: Proceedings (Abstracts) of the III All-Union Conference on Salmonid Fishes March 1988 Editor: S. M. Konovalov (ed.) (Table of contents and 76 of 252 abstracts only translated.) Original title: Sovremennoe sostoyanie issledovanii lososevidnykh ryb: Tezisy III Vsesoyuznogo soveshchaniya po lososevidnym rybam Published by: Akademiia Nauk, Tolyatti (USSR), 1988. Original language: Russian Available from: Canada Institute for Scientific and Technical Information National Research Council Ottawa, Ontario, Canada KlA 0S2 — 1990 DepadmentofFicheMs &Oceans 'JAN 21 1993 et do: Ministèrf.,› k 177 typescript pages o T reŒLY Secretary Secrétariat 14 of State d'État MULTILINGUAL SERVICES DIVISION — DIVISION DES SERVICES MULTILINGUES 1 TRANSLATION BUREAU BUREAU DES TRADUCTIONS 1 LIBRARY IDENTIFICATION — FICHE SIGNALÉTIQUE Translated from - Traduction de Into - En RUSSIAN ENGLISH Author - Auteur S.M. Konovalov (ed.) Title in English or French - Titre anglais ou français CURRENT STATUS OF INVESTIGATIONS OF SALMONID FISHES Title in foreign language (Transliterate foreign characters) Titre en langue étrangère (Transcrire en caractères romains) SOVREMENNOE SOSTOYANIE ISSLEDOVANII LOSOSEVIDNYKH RYB Reference in foreign language (Name of book or publication) in full, transliterate foreign characters. Référence en langue étrangère (Nom du livre ou publication), au complet, transcrire en caractères romains. Tezisy III Vsesoyuznogo soveshchaniya po lososevidnym rybam Reference in English or French - Référence en anglais ou français Abstracts of reports to the IIIrd All—Union Conference on Salmonid Fishes. Publisher - Editeur Page Numbers in original DATE OF PUBLICATION Numéros des pages dans DATE DE PUBLICATION l'original Year Issue No.
    [Show full text]
  • Lake El'gygytgyn Site: Thermal Modelling
    Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Clim. Past Discuss., 8, 2607–2644, 2012 www.clim-past-discuss.net/8/2607/2012/ Climate doi:10.5194/cpd-8-2607-2012 of the Past CPD © Author(s) 2012. CC Attribution 3.0 License. Discussions 8, 2607–2644, 2012 This discussion paper is/has been under review for the journal Climate of the Past (CP). Lake El’gygytgyn Please refer to the corresponding final paper in CP if available. site: thermal modelling Past climate changes and permafrost D. Mottaghy et al. depth at the Lake El’gygytgyn site: Title Page implications from data and thermal Abstract Introduction modelling Conclusions References Tables Figures D. Mottaghy1, G. Schwamborn2, and V. Rath3 1 Geophysica Beratungsgesellschaft mbH, Aachen, Germany J I 2Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany 3Department of Earth Sciences, Astronomy and Astrophysics, Faculty of Physical Sciences, J I Universidad Complutense de Madrid, Madrid, Spain Back Close Received: 6 July 2012 – Accepted: 9 July 2012 – Published: 16 July 2012 Full Screen / Esc Correspondence to: D. Mottaghy ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. Printer-friendly Version Interactive Discussion 2607 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract CPD We present results of numerical simulations of the temperature field of the subsurface around and beneath the crater Lake El’gygytgyn in NE Russia, which is subject of an 8, 2607–2644, 2012 interdisciplinary drilling campaign within the International Continental Drilling Program 5 (ICDP). This study focuses on determining the permafrost depth and the transition be- Lake El’gygytgyn tween talik and permafrost regimes, both, under steady-state and transient conditions site: thermal of past climate changes.
    [Show full text]
  • The Lake El'gygytgyn Scientific Drilling Project – Conquering Arctic
    Science Reports Science Reports The Lake El’gygytgyn Scientific Drilling Project – Conquering Arctic Challenges through Continental Drilling by Martin Melles, Julie Brigham-Grette, Pavel Minyuk, Christian Koeberl, Andrei Andreev, Timothy Cook, Grigory Fedorov, Catalina Gebhardt, Eeva Haltia-Hovi, Maaret Kukkonen, Norbert Nowaczyk, Georg Schwamborn, doi:10.2204/iodp.sd.11.03.2011 Volker Wennrich, and the El´gygytgyn Scientific Party record provides the first comprehensive and widely time- Abstract continuous insights into the evolution of the terrestrial Arctic since mid-Pliocene times. This is particularly true for the Between October 2008 and May 2009, the International lowermost 40 meters and uppermost 150 meters of the Continental Scientific Drilling Program (ICDP) sequence, which were drilled with almost 100% recovery and co-sponsored a campaign at Lake El´gygytgyn, located in a likely reflect the initial lake stage during the Pliocene and 3.6-Ma-old meteorite impact crater in northeastern Siberia. the last ~2.9 Ma, respectively. Nearly 200 meters of under- Drilling targets included three holes in the center of the lying rock were also recovered; these cores consist of an 170-m-deep lake, utilizing the lake ice cover as a drilling almost complete section of the various types of impact brec- platform, plus one hole close to the shore in the western lake cias including broken and fractured volcanic basement rocks catchment. At the lake’s center. the entire 315-m-thick lake and associated melt clasts. The investigation of this core sediment succession was penetrated. The sediments lack sequence promises new information concerning the any hiatuses (i.e., no evidence of basin glaciation or desicca- El´gygytgyn impact event, including the composition and tion), and their composition reflects the regional climatic nature of the meteorite, the energy released, and the shock and environmental history with great sensitivity.
    [Show full text]
  • 42 7992 Sudbury Coherence
    42 7992 Sudbury Coherence (as well as limited chemical) analyses have indicated that this buried At present we can conclude that the Manson crater is the only structure may in fact be of impact origin [8]. The impact origin was confirmed crater of K/T age, but Chicxulub is becoming a strong recently confirmed by the discovery of unambiguous evidence for contender, however, detailed geochemical, geochronological, and shock metamofphism, e.g., shocked quartz and feldspar [9]. The isotopic data are necessary to provide definitive evidence. stratigraphy of the crater and the exact succession and age of rocks Acknowledgments: I thank J. Hartung. R. R. Anderson, and are not entirely clear at this time, largely because the structure is V. L. Sharpton for Manson and Chicxulub samples and valuable now buried under about 1 km of Tertiary sediments, mainly lime- discussions. Work supported by Austrian " Fonds zur Fordenmg der stone, and because of limited sample availability due to the destruc- wissenschaftlichen Forschung," Project P8794-GEO. tion of core samples in a fire. The sedimentary sequence (composed References: [1] Alvarez L. W. et al. (1980) Science. 208, mainly of carbonates and evaporites) overlies a basement at 3-6 km 1095-1108. [2] BohorB. F. et al. (1984) Science, 224, 867-869. depth that is inferred to be composed of metamorphic rocks. If [3] Sigurdsson H. (\99l)N<uure, 353,839-842. [4] KoeberlC. and Chkxulub was formed by impact at a time at or before the end of the Sigurdsson H. (1992)GCA, 56. in press. [5] Kunk M. J. et al.
    [Show full text]
  • FROZEN GROUND the News Bulletin of the International Permafrost Association Number 27, December 2003
    FROZEN GROUND The News Bulletin of the International Permafrost Association Number 27, December 2003 Frozen Ground INTERNATIONAL PERMAFROST ASSOCIATION The International Permafrost Association, founded in 1983, has as its objectives to foster the dissemination of knowledge concerning permafrost and to promote cooperation among persons and national or international organisations engaged in scientific investigation and engineering work on permafrost. Membership is through adhering national or multinational organisations or as individuals in countries where no Adhering Body exists. The IPA is governed by its officers and a Council consisting of representatives from 23 Adhering Bodies having interests in some aspect of theoretical, basic and applied frozen ground research, including permafrost, seasonal frost, artificial freezing and periglacial phenomena. Committees, Working Groups, and Task Forces organise and coordinate research activities and special projects. The IPA became an Affiliated Organisation of the International Union of Geological Sciences in July 1989. The Association’s primary responsibilities are convening International Permafrost Conferences, undertaking special projects such as preparing databases, maps, bibliographies, and glossaries, and coordinating international field programs and networks. Conferences were held in West Lafayette, Indiana, U.S.A., 1963; in Yakutsk, Siberia, 1973; in Edmonton, Canada, 1978; in Fairbanks, Alaska, 1983; in Trondheim, Norway, 1988; in Beijing, China, 1993; in Yellowknife, Canada, 1998, and in Zurich, Switzerland, 2003. The ninth conference will be in Fairbanks, Alaska, in 2008. Field excursions are an integral part of each Conference, and are organised by the host country. Executive Committee 2003-2008 Council Members President Argentina Dr. Jerry Brown, U.S.A. Austria Vice Presidents Belgium Professor Charles Harris, U.K.
    [Show full text]
  • Catastrophes, Extinctions and Evolution: 50 Years of Impact Cratering Studies
    GOLDEN JUBILEE MEMOIR OF THE GEOLOGICAL SOCIETY OF INDIA No.66, 2008, pp.69-110 Catastrophes, Extinctions and Evolution: 50 Years of Impact Cratering Studies 1 2 W. UWE REIMOLD and CHRISTIAN KOEBERL 1Museum for Natural History (Mineralogy), Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin, Germany 2Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090Vienna, Austria Email: [email protected]; [email protected] Abstract Following 50 years of space exploration and the concomitant recognition that all surfaces of solid planetary bodies in the solar system as well as of comet nuclei have been decisively structured by impact bombardment over the 4.56 Ga evolution of this planetary system, impact cratering has grown into a fully developed, multidisciplinary research discipline within the earth and planetary sciences. No sub-discipline of the geosciences has remained untouched by this “New Catastrophism”, with main areas of research including, inter alia, formation of early crust and atmosphere on Earth, transfer of water onto Earth by comets and transfer of life between planets (“lithopanspermia”), impact flux throughout Earth evolution, and associated mass extinctions, recognition of distal impact ejecta throughout the stratigraphic record, and the potential that impact structure settings might have for the development of new – and then also ancient – life. In this contribution the main principles of impact cratering are sketched, the main findings of the past decades are reviewed, and we discuss the major current research thrusts. From both scientific interests and geohazard demands, this discipline requires further major research efforts – and the need to educate every geoscience graduate about the salient facts concerning this high-energy geological process that has the potential to be destructive on a local to global scale.
    [Show full text]