DOCSLIB.ORG

A Multi-Proxy Reconstruction of Paleolimnology and Paleoclimatic Variability Using Authigenic Lake Carbonates from Cleland Lake, British Columbia

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Multi-Proxy Reconstruction of Paleolimnology and Paleoclimatic Variability Using Authigenic Lake Carbonates from Cleland Lake, British Columbia A MULTI-PROXY RECONSTRUCTION OF PALEOLIMNOLOGY AND PALEOCLIMATIC VARIABILITY USING AUTHIGENIC LAKE CARBONATES FROM CLELAND LAKE, BRITISH COLUMBIA A dissertation submitted to Kent State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy by Lorita Nivanthi Mihindukulasooriya December 2014 © Copyright All rights reserved Except for previously published materials Dissertation written by Lorita Nivanthi Mihindukulasooriya B.Sc., University of Peradeniya, Sri Lanka, 2006 M.Sc., Ohio University, Athens, Ohio, 2009 Ph.D., Kent State University, 2014 Approved by Dr. Joseph Ortiz, PhD, Department of Geology, Doctoral Advisor Dr. Alison J. Smith, PhD, Department of Geology Dr. Neil Wells, PhD, Department of Geology Dr. Darren Bade, PhD, Department of Biology Dr. Laura Leff, PhD, Graduate Representator, Department of Biology Accepted by Dr. Daniel Holm, PhD, Chair, Department of Geology James L. Blank, PhD, Dean, College of Arts and Sciences TABLE OF CONTENTS LIST OF FIGURES .................................................................................................................................... vii LIST OF TABLES ....................................................................................................................................... xi PREFACE....................................................................................................................................................xii ACKNOWLEDGEMENTS ....................................................................................................................... xiii ABSTRACT ............................................................................................................................................... xvi CHAPTER 1 ................................................................................................................................................. 1 INTRODUCTION ........................................................................................................................................ 1 Research Questions and Objectives .......................................................................................................... 1 Study Area ................................................................................................................................................ 2 Geology of the Study Area.................................................................................................................... 3 Lake Hydrologic Properties .................................................................................................................. 7 Research Hypothesis ................................................................................................................................. 8 Holocene Climate of Southern British Columbia: A literature Review .................................................. 10 Late Glacial Climate of British Columbia .......................................................................................... 12 Early Holocene Climate of British Columbia ..................................................................................... 14 Mid Holocene Climate of British Columbia ....................................................................................... 18 Late Holocene Climate of British Columbia ....................................................................................... 20 CHAPTER 2 ............................................................................................................................................... 24 Reconstruction of Late Quaternary paleohydrologic conditions in southeastern British Columbia using visible derivative spectroscopy of Cleland Lake sediment ......................................................................... 24 (Manuscript in review in Quaternary Research) ......................................................................................... 24 Abstract ................................................................................................................................................... 24 Introduction ............................................................................................................................................. 25 Study Area .............................................................................................................................................. 27 Methods ................................................................................................................................................... 28 Sediment Core Collection ................................................................................................................... 28 Geochronology .................................................................................................................................... 29 Visible Derivative Spectroscopy ......................................................................................................... 30 X-ray Fluorescence ............................................................................................................................. 31 Results ..................................................................................................................................................... 32 iii Lake Limnological Properties ............................................................................................................. 32 Age Model .......................................................................................................................................... 32 Interpretation of the Principal Components ........................................................................................ 34 Discussion ............................................................................................................................................... 38 Evolution of the Lake Phytoplankton Community over the Holocene ............................................... 38 Paleohydrological Conditions Inferred from Phytoplankton Abundance ........................................... 41 Regional Comparison .......................................................................................................................... 48 Possible Mechanism for the Late Quaternary Drought ....................................................................... 52 Conclusions ............................................................................................................................................. 54 CHAPTER 3 ............................................................................................................................................... 56 MODERN HYDROLOGY IN THE PACIFIC NORTWEST DURING THE MID-HOLOCENE ........... 56 Abstract ................................................................................................................................................... 56 Introduction ............................................................................................................................................. 57 Methods ................................................................................................................................................... 60 Geochronology .................................................................................................................................... 60 Visible Derivative Spectroscopy ......................................................................................................... 61 Principal Component Analysis............................................................................................................ 61 Carbon and Oxygen Isotope Analysis ................................................................................................. 62 X-ray Fluorescence ............................................................................................................................. 63 Results ..................................................................................................................................................... 63 Present Isotopic Properties of the Lake Water .................................................................................... 63 Age model ........................................................................................................................................... 64 Visible Derivative Spectroscopy and Principal Component Analysis ................................................ 66 Elemental Concentrations ................................................................................................................... 69 Discussion ............................................................................................................................................... 73 Conclusions ............................................................................................................................................. 79 CHAPTER 4 ............................................................................................................................................... 81 EFFECT OF MAZAMA TEPHRA ON LAKE SEDIMENTARY COMPOSITION AND PRIMARY PRODUCTIVITY ....................................................................................................................................... 81 Abstract ..................................................................................................................................................
Load more

Recommended publications
  • Multi-Scale, Multi-Proxy Investigation of Late Holocene Tropical Cyclone Activity in the Western North Atlantic Basin
    Multi-Scale, Multi-Proxy Investigation of Late Holocene Tropical Cyclone Activity in the Western North Atlantic Basin François Oliva Thesis submitted to the Faculty of Graduate and Postdoctoral Studies in partial fulfillment of the requirements for the Doctorate of Philosophy in Geography Department of Geography, Environment and Geomatics Faculty of Arts University of Ottawa Supervisors: Dr. André E. Viau Dr. Matthew C. Peros Thesis Committee: Dr. Luke Copland Dr. Denis Lacelle Dr. Michael Sawada Dr. Francine McCarthy © François Oliva, Ottawa, Canada, 2017 Abstract Paleotempestology, the study of past tropical cyclones (TCs) using geological proxy techniques, is a growing discipline that utilizes data from a broad range of sources. Most paleotempestological studies have been conducted using “established proxies”, such as grain-size analysis, loss-on-ignition, and micropaleontological indicators. More recently researchers have been applying more advanced geochemical analyses, such as X-ray fluorescence (XRF) core scanning and stable isotopic geochemistry to generate new paleotempestological records. This is presented as a four article-type thesis that investigates how changing climate conditions have impacted the frequency and paths of tropical cyclones in the western North Atlantic basin on different spatial and temporal scales. The first article (Chapter 2; Oliva et al., 2017, Prog Phys Geog) provides an in-depth and up-to- date literature review of the current state of paleotempestological studies in the western North Atlantic basin. The assumptions, strengths and limitations of paleotempestological studies are discussed. Moreover, this article discusses innovative venues for paleotempestological research that will lead to a better understanding of TC dynamics under future climate change scenarios.
    [Show full text]
  • Paleolimnology – Recreating the History of a Lake Background: Every Minnesota Lake Accumulates Sediment
    St. Croix Watershed Research Station Paleolimnology – recreating the history of a lake Background: Every Minnesota lake accumulates sediment. Since the glaciers left over 11,000 years ago most lakes have accumulated between 10 and 80 ft of sediment in their deep basins. Sediments preserve a record of physical, chemical, and biological clues of how, when, and why a lake and its watershed have changed. Sediment coring ü Scientists (called paleolimnologists) work from an anchored boat or from the surface of the ice and use specialized equipment designed for recovering sediment cores. For example, a piston corer uses a clear tube that is lowered to the lake bottom using 10 ft-long alloy rods that thread together. The tube is fitted with a piston that is held in place with a cable; as the tube is pushed into the mud, the piston helps “pull” the sediment into the tube. Sediment core analyses – we test and measure physical, chemical, and biological clues that are preserved in the sediment ü Radioisotopes – To establish a date-depth relationship for a core, we use natural (Lead-210) or man-made (Cesium-137; from atomic bombs) radioisotopes. This tells us the approximate year that a layer of sediment A piston corer was deposited. ü Sediment type – We do a test called “Loss-on-ignition” to figure out what makes up the sediment: Inorganics – a measure of the mineral matter in the core. Inorganics may increase with erosion, land clearance, or rising water levels Carbonates – carbonates accumulate due to input of hard groundwater and as a result of
    [Show full text]
  • SVP's Letter to Editors of Journals and Publishers on Burmese Amber And
    Society of Vertebrate Paleontology 7918 Jones Branch Drive, Suite 300 McLean, VA 22102 USA Phone: (301) 634-7024 Email: [email protected] Web: www.vertpaleo.org FEIN: 06-0906643 April 21, 2020 Subject: Fossils from conflict zones and reproducibility of fossil-based scientific data Dear Editors, We are writing you today to promote the awareness of a couple of troubling matters in our scientific discipline, paleontology, because we value your professional academic publication as an important ‘gatekeeper’ to set high ethical standards in our scientific field. We represent the Society of Vertebrate Paleontology (SVP: http://vertpaleo.org/), a non-profit international scientific organization with over 2,000 researchers, educators, students, and enthusiasts, to advance the science of vertebrate palaeontology and to support and encourage the discovery, preservation, and protection of vertebrate fossils, fossil sites, and their geological and paleontological contexts. The first troubling matter concerns situations surrounding fossils in and from conflict zones. One particularly alarming example is with the so-called ‘Burmese amber’ that contains exquisitely well-preserved fossils trapped in 100-million-year-old (Cretaceous) tree sap from Myanmar. They include insects and plants, as well as various vertebrates such as lizards, snakes, birds, and dinosaurs, which have provided a wealth of biological information about the ‘dinosaur-era’ terrestrial ecosystem. Yet, the scientific value of these specimens comes at a cost (https://www.nytimes.com/2020/03/11/science/amber-myanmar-paleontologists.html). Where Burmese amber is mined in hazardous conditions, smuggled out of the country, and sold as gemstones, the most disheartening issue is that the recent surge of exciting scientific discoveries, particularly involving vertebrate fossils, has in part fueled the commercial trading of amber.
    [Show full text]
  • Early Tetrapod Relationships Revisited
    Biol. Rev. (2003), 78, pp. 251–345. f Cambridge Philosophical Society 251 DOI: 10.1017/S1464793102006103 Printed in the United Kingdom Early tetrapod relationships revisited MARCELLO RUTA1*, MICHAEL I. COATES1 and DONALD L. J. QUICKE2 1 The Department of Organismal Biology and Anatomy, The University of Chicago, 1027 East 57th Street, Chicago, IL 60637-1508, USA ([email protected]; [email protected]) 2 Department of Biology, Imperial College at Silwood Park, Ascot, Berkshire SL57PY, UK and Department of Entomology, The Natural History Museum, Cromwell Road, London SW75BD, UK ([email protected]) (Received 29 November 2001; revised 28 August 2002; accepted 2 September 2002) ABSTRACT In an attempt to investigate differences between the most widely discussed hypotheses of early tetrapod relation- ships, we assembled a new data matrix including 90 taxa coded for 319 cranial and postcranial characters. We have incorporated, where possible, original observations of numerous taxa spread throughout the major tetrapod clades. A stem-based (total-group) definition of Tetrapoda is preferred over apomorphy- and node-based (crown-group) definitions. This definition is operational, since it is based on a formal character analysis. A PAUP* search using a recently implemented version of the parsimony ratchet method yields 64 shortest trees. Differ- ences between these trees concern: (1) the internal relationships of aı¨stopods, the three selected species of which form a trichotomy; (2) the internal relationships of embolomeres, with Archeria
    [Show full text]
  • Holocene Chironomid-Inferred Salinity and Paleovegetation Reconstruction
    Document generated on 10/02/2021 8:21 a.m. Géographie physique et Quaternaire Holocene chironomid-inferred salinity and paleovegetation reconstruction from Kilpoola Lake, British Columbia La salinité (déterminée par les chironomides) et la reconstitution paléovégétale du Kilpoola Lake (Colombie-Britannique) à l’Holocène Salzgehalt, bestimmt durch die Chironomidae, und Rekonstruktion der Paläovegetation des Kilpoola-Sees, British Columbia Mark L. Heinrichs, Ian R. Walker, Rolf W. Mathewes and Richard J. Hebda Volume 53, Number 2, 1999 Article abstract Salinity fluctuations in lakes of semi-arid regions have been recognised as URI: https://id.erudit.org/iderudit/004878ar indicators of paleoclimatic change and have provided a valuable line of DOI: https://doi.org/10.7202/004878ar evidence in paleoclimatic reconstruction. However, factors other than climate, including sedimentologic events, may also affect salinity. At Kilpoola Lake, See table of contents early postglacial freshwater chironomids (Microtendipes, Sergentia, and Heterotrissocladius) occur in the basal sediments and yield a chironomid-inferred salinity of <0.03 g/l. Higher salinities, ranging from 1.0 to Publisher(s) 3.5 g/l, with Cricotopus/Orthocladius and Tanypus (chironomids typical of saline environments) follow and, persist for most of the remainder of the Les Presses de l'Université de Montréal Holocene. An inferred 450% salinity increase (from 1.6 to 7.3 g/l) occurred in the sediment above the Mount Mazama tephra, followed by a return to the ISSN pre-Mount Mazama salinity. The early Holocene pollen spectra are typical of open steppe, but the post-Mazama Artemisia pollen percentages are 0705-7199 (print) exceptionally high and are associated with silty clays.
    [Show full text]
  • Order of the Executive Director May 14, 2020
    PROVINCE OF BRITISH COLUMBIA Park Act Order of the Executive Director TO: Public Notice DATE: May 14, 2020 WHEREAS: A. This Order applies to all Crown land established or continued as a park, conservancy, recreation area, or ecological reserve under the Park Act, the Protected Areas of British Columbia Act or protected areas established under provisions of the Environment and Land Use Act. B. This Order is made in the public interest in response to the COVID-19 pandemic for the purposes of the protection of human health and safety. C. This Order is in regard to all public access, facilities or uses that exist in any of the lands mentioned in Section A above, and includes but is not limited to: campgrounds, day-use areas, trails, playgrounds, shelters, visitor centers, cabins, chalets, lodges, resort areas, group campsites, and all other facilities or lands owned or operated by or on behalf of BC Parks. D. This Order is in replacement of the Order of the Executive Director dated April 8, 2020 and is subject to further amendment, revocation or repeal as necessary to respond to changing circumstances around the COVID-19 pandemic. Exemptions that were issued in relation to the previous Order, and were still in effect, are carried forward and applied to this Order in the same manner and effect. Province of British Columbia Park Act Order of the Executive Director 1 E. The protection of park visitor health, the health of all BC Parks staff, Park Operators, contractors and permittees is the primary consideration in the making of this Order.
    [Show full text]
  • Fish Fossils As Paleo-Indicators of Ichthyofauna Composition and Climatic Change in Lake Malawi, Africa
    Palaeogeography, Palaeoclimatology, Palaeoecology 303 (2011) 126–132 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Fish fossils as paleo-indicators of ichthyofauna composition and climatic change in Lake Malawi, Africa Peter N. Reinthal a,⁎, Andrew S. Cohen b, David L. Dettman b a Department of Ecology and Evolutionary Biology, The University of Arizona, Tucson, AZ 85721, USA b Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA article info abstract Article history: Numerous biological and chemical paleorecords have been used to infer paleoclimate, lake level fluctuation Received 27 February 2009 and faunal composition from the drill cores obtained from Lake Malawi, Africa. However, fish fossils have Received in revised form 23 October 2009 never been used to examine changes in African Great Lake vertebrate aquatic communities nor as indicators Accepted 1 January 2010 of changing paleolimnological conditions. Here we present results of analyses of a Lake Malawi core dating Available online 7 January 2010 back ∼144 ka that describe and quantify the composition and abundance of fish fossils and report on stable carbon isotopic data (δ13C) from fish scale, bone and tooth fossils. We compared the fossil δ13C values to δ13C Keywords: fi Lake Malawi values from extant sh communities to determine whether carbon isotope ratios can be used as indicators of Cichlid inshore versus offshore pelagic fish assemblages. Fossil buccal teeth, pharyngeal teeth and mills, vertebra and Fish fossils scales from the fish families Cichlidae and Cyprinidae occur in variable abundance throughout the core. Carbon isotopes Carbon isotopic ratios from numerous fish fossils throughout the core range between −7.2 and −27.5‰, Cyprinid similar to those found in contemporary Lake Malawi benthic and pelagic fish faunas.
    [Show full text]
  • Paleoecology: an Untapped Resource for Teaching Environmental Change
    International Journal of Environmental & Science Education Paleoecology Vol. 4, No. 4, October 2009, 441-447 International Journal of Environmental & Science Education Vol. 3, No. 3, July 2008, xx-xx Paleoecology: An Untapped Resource for Teaching Environmental Change Diana J. Raper Oregon State University, USA Holli Zander Brevard Public Schools, USA Received 06 February 2009; Accepted 13 May 2009 Global warming and climate change have become hot topics that incite debate, inspire scientific research, and influence international policy. However, the scientific research that provides the past climate and environmental information upon which contemporary envi- ronmental change is measured, receives little attention in high school curriculum. Paleoe- cology, the study of ancient ecosystems, provides a unifying theme for teaching multiple high school science curriculum concepts involving global environmental change. As a teaching tool, paleoecology establishes a framework linking concepts such as geologic time, climate change, adaptation, survival, extinction, human impact and ecological interac- tions that are often taught separately. This article provides a brief overview of how the science of paleoecology can be introduced to students and incorporated into the curriculum through simple activities. The activities outlined here include using elevation maps or Ga- zetteers to investigate potential sites where marine fossils may be found far from the ocean, using multiple biological proxies to measure climate change, and creating models to dem- onstrate the impact of sea level rise on coastal ecosystems. These activities provide numer- ous opportunities for the students to discuss the scientific research associated with climate change, the economic impacts of changing climate, and how science may influence policy regarding climate change mitigation.
    [Show full text]
  • At Mahoney Lake, British Columbia, Canada 219 DOI 10.2478/Limre-2020-0021
    Limnol. Rev. (2020)Fifty years 20, 4:of 219-227limnology (1969-2019) at Mahoney Lake, British Columbia, Canada 219 DOI 10.2478/limre-2020-0021 Fifty years of limnology (1969-2019) at Mahoney Lake, British Columbia, Canada Markus L. Heinrichs1,*, Ian R. Walker2, Ken J. Hall3, Jörg Overmann4, 5, Molly D. O’Beirne6 1 Department of Geography and Earth & Environmental Science, Okanagan College, 1000 K.L.O. Road, Kelowna, British Columbia V1Y 4X8, Canada, e-mail: [email protected] (*corresponding author) 2 Department of Biology and Department of Earth, Environmental and Geographic Sciences, University of British Columbia, Okanagan Campus, 3333 University Way, Kelowna, British Columbia V1V 1V7, Canada, e-mail: [email protected] 3 Department of Civil Engineering, Institute for Resources, Environment and Sustainability, University of British Columbia, 2329 West Mall, Vancouver, British Columbia V6T 1Z4, Canada, e-mail: [email protected] 4 Leibniz-Institut DSMZ- German Collection of Microorganisms and Cell Cultures, Inhoffenstraße 7B, 38124 Braunschweig, Germany, e-mail: [email protected] 5 Braunschweig University of Technology, Universitätsplatz 2, 38106, Braunschweig, Germany 6 Department of Geology and Environmental Science, 4107 O’Hara Street, University of Pittsburgh, Pittsburgh, PA 15260, United States of America, e-mail: [email protected] Abstract: Mahoney Lake is a small, meromictic saline lake in south-central British Columbia noted for its unique layer of purple sulfur bacteria. First examined in 1969, this lake has undergone physical, chemical, biological, and pre-historical research to generate an understanding of how the lake and its biota function have developed through time. Advances in understanding the sulfur transformations and bacterial nutrient cycling over the last fifty years have been prolific, resulting in the description of several new taxa.
    [Show full text]
  • Fossil Communities in Paleoecology: Their Recognition and Significance
    J. A. FAGERSTROM Dept. Geology, University of Nebraska, Lincoln, Nebr. Fossil Communities in Paleoecology: Their Recognition and Significance Abstract: Fossil assemblages consist of individuals mentary aggregate, lithofacies relationships, sur- that were members of one or more ancient com- face condition of fossils, and ratio of whole to frag- munities. Four types of fossil assemblages (fossil mented shells. Replacement, leaching, and crush- communities, residual or winnowed fossil com- ing of shells are the causes of most postbunal munities, transported fossil assemblages, and mixed alteration and may profoundly influence the cri- fossil assemblages) may be differentiated on the teria for preburial alteration. basis of amount, and in some cases, cause of pre- Analysis of a fossil assemblage from the Pennsyl- burial alteration. The most damaging agents to vanian of Nebraska indicates that the specimens marine communities are predators, scavengers, and have been subject to considerable postburial crush- especially bottom currents which selectively re- ing which has reduced the significance of some of move shells. To assess the preburial alteration of a the criteria for assessing preburial alteration. None- particular fossil assemblage one must evaluate as theless, right-skewed size-frequency distributions many of the following criteria as can be reasonably for two species of fossil invertebrates give strong applied: size-frequency distributions, ratio of indication that this assemblage is a fossil community. articulated to disarticulated valves, ratio of oppo- This conclusion is supported by the fact that the site valves, dispersion of fossils, population density, elongated shells show no tendency toward parallel community density, faunal composition and alignment and the absence of primary sedimentary diversity, orientation of clastic particles (including structures indicative of deposition from strong fossils), texture, sorting, and structure of sedi- directional currents.
    [Show full text]
  • Vertebrate Paleontology of the Cloverly Formation (Lower Cretaceous), II: Paleoecology Author(S): Matthew T
    Vertebrate Paleontology of the Cloverly Formation (Lower Cretaceous), II: Paleoecology Author(s): Matthew T. Carrano , Matthew P. J. Oreska , and Rowan Lockwood Source: Journal of Vertebrate Paleontology, 36(2) Published By: The Society of Vertebrate Paleontology URL: http://www.bioone.org/doi/full/10.1080/02724634.2015.1071265 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Journal of Vertebrate Paleontology e1071265 (12 pages) Ó by the Society of Vertebrate Paleontology DOI: 10.1080/02724634.2015.1071265 ARTICLE VERTEBRATE PALEONTOLOGY OF THE CLOVERLY FORMATION (LOWER CRETACEOUS), II: PALEOECOLOGY MATTHEW T. CARRANO,*,1 MATTHEW P. J. ORESKA,1,2 and ROWAN LOCKWOOD3 1Department of Paleobiology, Smithsonian Institution, P.O. Box 37012, MRC 121, Washington, DC 20013-7012, U.S.A., [email protected]; 2Department of Environmental Sciences, University of Virginia, Clark Hall, 291 McCormick Road, P.O.
    [Show full text]
  • Redalyc.Biostratigraphy and Paleoecology of the Qom Formation
    Revista Mexicana de Ciencias Geológicas ISSN: 1026-8774 [email protected] Universidad Nacional Autónoma de México México Behforouzi, Elham; Safari, Amrollah Biostratigraphy and paleoecology of the Qom Formation in the Chenar area (northwestern Kashan) , Iran Revista Mexicana de Ciencias Geológicas, vol. 28, núm. 3, diciembre, 2011, pp. 555-565 Universidad Nacional Autónoma de México Querétaro, México Available in: http://www.redalyc.org/articulo.oa?id=57221165016 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Revista Mexicana de Ciencias Geológicas,Biostratigraphy v. 28, núm. and 3, paleoecology 2011, p. 555-565 of the Qom Formation, Iran 555 Biostratigraphy and paleoecology of the Qom Formation in Chenar area (northwestern Kashan), Iran Elham Behforouzi* and Amrollah Safari Department of Geology, Faculty of Sciences, University of Isfahan, Isfahan, Iran, 81746-73441. * [email protected] ABSTRACT A study of large benthic foraminifera from the 147 m-thick Qom Formation in the Chenar area (northwestern Kashan) is reported. One hundred and twelve thin sections were prepared and the distribution of benthic foraminifera was analyzed to reconstruct paleoenvironmental conditions. Study of these sections led to the identification of 28 genera and 38 species. On the basis of the recognized foraminifera, the section is comparable to Lepidocyclina- Operculina- Ditrupa Assemblage zone, and the age of the Qom Formation in the studied section is assigned to the Oligocene. Evidence of sea level changes is observed from bottom to top of the studied section.
    [Show full text]