DOCSLIB.ORG

Part II Lithostratigraphy and Chronostratigraphy: Introduction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Part II Lithostratigraphy and Chronostratigraphy: Introduction Part II Lithostratigraphy and Chronostratigraphy: Introduction EB. VAN HOUTEN Lithostratigraphy and chronostratigraphy have long Among the many advances in stratigraphic analy­ been central concerns in the study of sedimentary sis several have been especially effective. Recogni­ basins. In the past, however, the focus was com­ tion of regionally extensive unconformity-bound monly on local problems or on conventional codes sequences (Sloss 1963), corroborated by seismic for cataloging global geology. During the past stratigraphy (Vail et al. 1977), emphasized the need several decades a rapid rise of interest in basin analy­ for reliable means of regional correlation, and it sis, generated in part by petroleum exploration and increased the significance of unconformities in basin stimulated by the plate-tectonics paradigm, has led analysis. This has led to a more general interest, the to "the greening of stratigraphy" (Sloss 1984). With meaning of hiatuses in basin history and clues to it has come an expansion of pertinent techniques and lapses in normal sedimentation. Appreciation that methods, recently reviewed by Miall (1984), who sedimentation may be essentially discontinuous, points out that stratigraphy now requires a synthesis consisting of increments and gaps (Sadler 1981), of many sorts of geologic data. Concurrently, the has improved our understanding of "rates of accumu­ principal kinds of basins have been delineated in a lation." Development of the graphic correlation plate-tectonics framework (Bally and Snelson 1980; technique (Shaw 1964) provided a reliable way to Mitchell and Reading 1986). This has increased the discover changes and differences in subsidence his­ role of detailed description, accurate correlation, tory. In the past this method was applied mostly to and precise interpretation of their basin fill because successions with rigorous biostratigraphic control; that is the main source of information about the sub­ its broader value has not yet been fully appreciated. sidence history. A backs tripping method of analyzing stratigraphic Early in the "greening" Francis Pettijohn recog­ sections can produce tectonic subsidence curves of nized the importance of careful study of the sedi­ passive margins which reflect thermal contraction of mentary rock record - a focus that was a persisting the heated lithosphere (Sleep 1971). A continuing theme throughout his constructive career. In partic­ complementary concern has been the identification ular, Pettijohn's extensive work on sedimentary and interpretation of transgressive and regressive structures, as well as that of his many students, is alternations and the role of global rise and fall of sea reflected in the Atlas and Glossary of Primary Sedi­ level. Construction of oxygen, carbon, and sulfur mentary Structures (Pettijohn and Potter 1964) and isotope curves has contributed to the correlation of in Paleocurrents and Basin Analysis (Potter and Pet­ sea-level changes as well as to the interpretation of tijohn 1977). This, in tum, contributed immensely the marine environment. Identification of vertical to the development of facies models. Use of these patterns of magnetic reversals in sedimentary rocks two-dimensional vertical profiles (Visher 1965; affords still another new source of chronostrati­ Walker 1979) in reporting and analyzing sedimen­ graphic markers, especially when they have been tary sequences has helped alert students to the vari­ calibrated with the detailed radiometric time scale ety of successions of facies, and encouraged them to (Berggren et al. 1985). These methods of correlation try to find some order in the lithostratigraphic are especially useful today when there is an enthus­ record. iastic interest in finding allocyclic control expressed 64 EB. Van Houten extensively in the stratigraphic record. With this rate of 1 metre per 1,000 years, and that a significant trend has come an increased awareness of the effect change in the rate of sedimentation recorded within of Milankovitch orbital cycles in producing some of the deposit probably resulted from a major change in the patterned sedimentary sequences. provenance. Each of the papers assembled in this section Bond, Kominz, and Grotzinger have analyzed the elaborates a particular method or technique of lower Paleozoic stratigraphic record of the Cordille­ lithostratigraphic or chronostratigraphic analysis ran and Appalachian orogens to test whether multi­ that contributes to the more general study of ple orders of sea-level change prevailed then. They sedimentary basins and will have an increasingly have constructed subsidence curves by the back­ important role in the future. Miall has reviewed stripping method which show that in general the changing ideas about detrital facies architecture, and subsidence decayed exponentially with time in he concludes that in many situations two­ response to slow cooling of the crust. Significantly, dimensional vertical profiles are inadequate for however, the curves also reveal systematic deflec­ accurate understanding of complex three­ tions. These suggest that the long-term subsidence of dimensional sedimentary deposits. In an effort to the Paleozoic passive margins was modified by generate some new unifying concepts, he empha­ 40-60 m.y. and 2-10 m.y. patterns of eustatic rise sizes the importance of recognizing a hierarchy of and fall of sea level that were similar to patterns that physical scales and three-dimensional architectural prevailed during Jurassic time. elements, or depositional units, characterized by Nemec demonstrates that sequences of coal meas­ their lithofacies composition, and external and ures provide important clues to short-term intrabasi­ internal geometry. In this approach his focus is on a nal differential subsidence not accounted for in six-fold hierarchy of bounding surfaces, or bedding general basin modelling. Noting that beds of coal contacts, as a source of detailed information about commonly accumulate during basin-wide hiatuses in the relation between duration of events and the scale normal sedimentation, he regards them as essen­ and geometry of the product. tially chronostratigraphic markers. Then he uses the Shanmugam returns to an old stratigraphic theme coal measures as "biological" events and analyzes - unconformities. He identifies erosional unconfor­ the data with the graphic correlation technique mities of local to global scale, discusses the origin of (Shaw 1964). By this means he identifies changing subaerial and submarine varieties, and reviews rates of tectonic basin subsidence and sediment criteria for recognizing them. In emphasizing their accumulation in a foreland basin, an intracratonic role in basin analysis Shanmugam points out some of basin, and two extensional basins. The results sug­ the effects of eustatic and tectonic controls of sea gest that other factors, such as compaction and level, as well as problems of distinguishing between sediment loading, have relatively little effect on sub­ them, especially in seismic stratigraphic records. In sidence. petroleum exploration, erosional unconformities are Johnson and his colleagues describe a method for important, especially where they mark the upper calculating stratigraphic variability based on the boundary of increased porosity, separate reservoir magnetic-reversal time scale. Use of these time lines and source rocks, or provide avenues for migration for lateral tracing and correlation of Miocene fluvial of hydrocarbons. deposits in Pakistan reveals both lateral stratigraphic Clifton, Hunter, and Gardner have analyzed a nonuniformity between sections and local unsteadi­ thick late Cenozoic shallow marine and shoreline ness, or vertical variation in sedimentation, within deposit, with the aim of isolating the major factors sections. The authors address the question of how controlling its transgressions and regressions. For much of the observed variability is in the strati­ this purpose ten depositional facies, identified on graphic record and how much may be an artifact of the basis of biota, sedimentary structures, and tex­ sampling. In spite of recognized complications, the tures, have been reconstructed in a succession of identified variation in sedimentation from place to recurring transgressions and regressions. The con­ place and from time to time is a measure of the sistent pattern of alternations compares closely with dynamic processes at work. With continued refine­ a revised Pleistocene eustatic sea-level curve gener­ ment and extension the magnetic-reversal time scale ated by these authors. The study also reveals that the will become an increasingly useful chronostrati­ basin subsided throughout its history at an average graphic tool. Part II. Lithostratigraphy and Chronostratigraphy: Introduction 65 References Geology 89:569-584. SHAW, A.B. (1964) Time in Stratigraphy. New York: BALLY, A.W. and SNELSON, S. (1980) Realms of subsi­ McGraw-Hill, 365 p. dence. In: Miall, A.D. (ed) Facts and Principles of SLEEP, N.H. (1971) Thermal effects of the formation of World Petroleum Occurrence. Canadian Society Atlantic continental margins by continental breakup. Petroleum Geologists Memoir 6, pp. 9-94. Geophysical Journal Royal Astronomical Society BERGGREN, W.A., KENT, DV., FLYNN, J.J., and 24:325-350. VAN COUVERlNG, lA. (1985) Cenozoic geochro­ SLOSS, L.L. (1963) Sequences in the cratonic interior of nology. Geological Society American Bulletin 96: 1407- North America. Geological Society America Bulletin 1418. 74:93-113. MIALL, A.D.
Load more

Recommended publications
  • Lithostratigraphic Mapping Through Saprolitic Regolith Using Soil Geochemistry and High-Resolution Aeromagnetic Surveys
    EGU2020-20242 https://doi.org/10.5194/egusphere-egu2020-20242 EGU General Assembly 2020 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Lithostratigraphic Mapping Through Saprolitic Regolith Using Soil Geochemistry and High-Resolution Aeromagnetic Surveys. Helen Twigg and Murray Hitzman iCRAG, School of Earth Sciences, University College Dublin, Belfield, Dublin, Ireland The Neoproterozoic Central African Copperbelt located in southern Democratic Republic of Congo (DRC) and the northwestern Zambia and contains 48% of the world’s cobalt reserves and significant resources of copper, zinc, nickel and gold. A good understanding of the geology is critical for successful mineral exploration. However, geological mapping is hindered by low topographic relief, limited outcrop, and a generally deep (10-100m) weathering profile developed since the Late Miocene. Multielement soil geochemistry provides a means for conducting geological mapping. Areas with outcrop or containing drill holes and/or trenches were utilized to relate known geological lithologies with soil geochemical results using major element and trace element ratios. The lithostratigraphy within a study area along the DRC-Zambia border can be geochemically sub- divided into three units. Mixed carbonate and siliciclastic lithologies of the lower portion of the local stratigraphy are typically characterised by elevated V, Ti, and Nb. Mudstones and siltstones are dominated by elevated Al, Fe and Ba. The upper portion of the local stratigraphy is geochemically neutral with regards to trace elements. Lithological discrimination through analysis of soil geochemical data is limited in some areas by intense weathering. A A-CNK-FM diagram exhibits how complete weathering of carbonate rocks and carbonate-rich breccias (after evaporites) results in the somewhat counter intuitive outcome that residual soils above carbonate rocks are amongst the most aluminum rich in the study area with >80% Al2O3 (mol%) or >80% combined Al2O3 (mol%) and FeO + MgO (mol%).
    [Show full text]
  • The Paleontology Synthesis Project and Establishing a Framework for Managing National Park Service Paleontological Resource Archives and Data
    Lucas, S.G. and Sullivan, R.M., eds., 2018, Fossil Record 6. New Mexico Museum of Natural History and Science Bulletin 79. 589 THE PALEONTOLOGY SYNTHESIS PROJECT AND ESTABLISHING A FRAMEWORK FOR MANAGING NATIONAL PARK SERVICE PALEONTOLOGICAL RESOURCE ARCHIVES AND DATA VINCENT L. SANTUCCI1, JUSTIN S. TWEET2 and TIMOTHY B. CONNORS3 1National Park Service, Geologic Resources Division, 1849 “C” Street, NW, Washington, D.C. 20240, [email protected]; 2National Park Service, 9149 79th Street S., Cottage Grove, MN 55016, [email protected]; 3National Park Service, Geologic Resources Division, 12795 W. Alameda Parkway, Lakewood, CO 80225, [email protected] Abstract—The National Park Service Paleontology Program maintains an extensive collection of digital and hard copy documents, publications, photographs and other archives associated with the paleontological resources documented in 268 parks. The organization and preservation of the NPS paleontology archives has been the focus of intensive data management activities by a small and dedicated team of NPS staff. The data preservation strategy complemented the NPS servicewide inventories for paleontological resources. The first phase of the data management, referred to as the NPS Paleontology Synthesis Project, compiled servicewide paleontological resource data pertaining to geologic time, taxonomy, museum repositories, holotype fossil specimens, and numerous other topics. In 2015, the second phase of data management was implemented with the creation and organization of a multi-faceted digital data system known as the NPS Paleontology Archives and NPS Paleontology Library. Two components of the NPS Paleontology Archives were designed for the preservation of both park specific and servicewide paleontological resource archives and data. A third component, the NPS Paleontology Library, is a repository for electronic copies of geology and paleontology publications, reports, and other media.
    [Show full text]
  • Historical Development and Problems Within the Pennsylvanian Nomenclature of Ohio.1
    Historical Development and Problems Within the Pennsylvanian Nomenclature of Ohio.1 GLENN E. LARSEN, OHIO Department of Natural Resources, Division of Geological Survey, Fountain Sq., Bldg. B, Columbus, OH 43224 ABSTRACT. An analysis of the historical development of the Pennsylvanian stratigraphic nomenclature, as used in Ohio, has helped define and clarify problems inherent in Ohio's stratigraphic nomenclature. Resolution of such problems facilitates further development of a useful stratigraphy and philosophy for mapping. Investigations of Pennsylvanian-age rocks in Ohio began as early as 1819- From 1858 to 1893, investigations by Newberry, I. C. White, and Orton established the stratigraphic framework upon which the present-day nomenclature is based. During the 1950s, the cyclothem concept was used to classify and correlate Pennsylvanian lithologic units. This classification led to a proliferation of stratigraphic terms, as almost every lithologic type was named and designated as a member of a cyclothem. By the early 1960s, cyclothems were considered invalid as a lithostratigraphic classification. Currently, Pennsylvanian nomenclature of Ohio, as used by the Ohio Division of Geological Survey, consists of four groups containing 123 named beds, with no formal formations or members. In accordance with the 1983 North American Stratigraphic code, the Ohio Division of Geological Survey considers all nomenclature below group rank as informal. OHIO J. SCI. 91 (1): 69-76, 1991 INTRODUCTION DISCUSSION Understanding the historical development of Pennsyl- The Early 1800s vanian stratigraphy in Ohio is important to the Ohio The earliest known references to Pennsylvanian-age Division of Geological Survey (OGS). Such an under- rocks in Ohio are found in Atwater's (1819) report on standing of Pennsylvanian stratigraphy helps define Belmont County, and an article by Granger (1821) on plant stratigraphic nomenclatural problems in order to make fossils collected near Zanesville, Muskingum County.
    [Show full text]
  • Stratigraphical Framework for the Devonian (Old Red Sandstone) Rocks of Scotland South of a Line from Fort William to Aberdeen
    Stratigraphical framework for the Devonian (Old Red Sandstone) rocks of Scotland south of a line from Fort William to Aberdeen Research Report RR/01/04 NAVIGATION HOW TO NAVIGATE THIS DOCUMENT ❑ The general pagination is designed for hard copy use and does not correspond to PDF thumbnail pagination. ❑ The main elements of the table of contents are bookmarked enabling direct links to be followed to the principal section headings and sub-headings, figures, plates and tables irrespective of which part of the document the user is viewing. ❑ In addition, the report contains links: ✤ from the principal section and sub-section headings back to the contents page, ✤ from each reference to a figure, plate or table directly to the corresponding figure, plate or table, ✤ from each figure, plate or table caption to the first place that figure, plate or table is mentioned in the text and ✤ from each page number back to the contents page. Return to contents page NATURAL ENVIRONMENT RESEARCH COUNCIL BRITISH GEOLOGICAL SURVEY Research Report RR/01/04 Stratigraphical framework for the Devonian (Old Red Sandstone) rocks of Scotland south of a line from Fort William to Aberdeen Michael A E Browne, Richard A Smith and Andrew M Aitken Contributors: Hugh F Barron, Steve Carroll and Mark T Dean Cover illustration Basal contact of the lowest lava flow of the Crawton Volcanic Formation overlying the Whitehouse Conglomerate Formation, Trollochy, Kincardineshire. BGS Photograph D2459. The National Grid and other Ordnance Survey data are used with the permission of the Controller of Her Majesty’s Stationery Office. Ordnance Survey licence number GD 272191/2002.
    [Show full text]
  • PHANEROZOIC and PRECAMBRIAN CHRONOSTRATIGRAPHY 2016
    PHANEROZOIC and PRECAMBRIAN CHRONOSTRATIGRAPHY 2016 Series/ Age Series/ Age Erathem/ System/ Age Epoch Stage/Age Ma Epoch Stage/Age Ma Era Period Ma GSSP/ GSSA GSSP GSSP Eonothem Eon Eonothem Erathem Period Eonothem Period Eon Era System System Eon Erathem Era 237.0 541 Anthropocene * Ladinian Ediacaran Middle 241.5 Neo- 635 Upper Anisian Cryogenian 4.2 ka 246.8 proterozoic 720 Holocene Middle Olenekian Tonian 8.2 ka Triassic Lower 249.8 1000 Lower Mesozoic Induan Stenian 11.8 ka 251.9 Meso- 1200 Upper Changhsingian Ectasian 126 ka Lopingian 254.2 proterozoic 1400 “Ionian” Wuchiapingian Calymmian Quaternary Pleisto- 773 ka 259.8 1600 cene Calabrian Capitanian Statherian 1.80 Guada- 265.1 Proterozoic 1800 Gelasian Wordian Paleo- Orosirian 2.58 lupian 268.8 2050 Piacenzian Roadian proterozoic Rhyacian Pliocene 3.60 272.3 2300 Zanclean Kungurian Siderian 5.33 Permian 282.0 2500 Messinian Artinskian Neo- 7.25 Cisuralian 290.1 Tortonian Sakmarian archean 11.63 295.0 2800 Serravallian Asselian Meso- Miocene 13.82 298.9 r e c a m b i n P Neogene Langhian Gzhelian archean 15.97 Upper 303.4 3200 Burdigalian Kasimovian Paleo- C e n o z i c 20.44 306.7 Archean archean Aquitanian Penn- Middle Moscovian 23.03 sylvanian 314.6 3600 Chattian Lower Bashkirian Oligocene 28.1 323.2 Eoarchean Rupelian Upper Serpukhovian 33.9 330.9 4000 Priabonian Middle Visean 38.0 Carboniferous 346.7 Hadean (informal) Missis- Bartonian sippian Lower Tournaisian Eocene 41.0 358.9 ~4560 Lutetian Famennian 47.8 Upper 372.2 Ypresian Frasnian Units of the international Paleogene 56.0 382.7 Thanetian Givetian chronostratigraphic scale with 59.2 Middle 387.7 Paleocene Selandian Eifelian estimated numerical ages.
    [Show full text]
  • A Middle to Late Holocene Record of Arroyo Cut-Fill Events
    A MIDDLE TO LATE HOLOCENE RECORD OF ARROYO CUT-FILL EVENTS IN KITCHEN CORRAL WASH, SOUTHERN UTAH by William M. Huff A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Geology Approved: _________________________ _________________________ Dr. Tammy M. Rittenour Dr. Joel L. Pederson Major Professor Committee Member _________________________ _________________________ Dr. Patrick Belmont Dr. Mark R. McLellan Committee Member Vice President for Research and Dean of the School of Graduate Studies UTAH STATE UNIVERSITY Logan, Utah 2013 ii Copyright © William M. Huff 2013 All Rights Reserved iii ABSTRACT A Middle to Late Holocene Record of Arroyo Cut-Fill Events in Kitchen Corral Wash, Southern Utah by William M. Huff, Master of Science Utah State University, 2013 Major Professor: Dr. Tammy M. Rittenour Department: Geology This study examines middle to late Holocene episodes of arroyo incision and aggradation in the Kitchen Corral Wash (KCW), a tributary of the Paria River in southern Utah. Arroyos are entrenched channels in valley-fill alluvium, and are capable of capturing decadal- to centennial- scale fluctuations in watershed hydrology as evidenced by the Holocene cut-fill stratigraphy recorded within near-vertical arroyo-channel walls. KCW has experienced both historic (ca. 1880-1920 AD) and prehistoric (Holocene) episodes of arroyo cutting and filling. The near- synchronous timing of arroyo cut-fill events between the Paria River and regional drainages over the last ~1 have led some researchers to argue that arroyo development is climatically driven. However, the influence of allogenic (climate-related) or autogenic (geomorphic threshold) forcings on arroyo dynamics are less clear.
    [Show full text]
  • Lithostratigraphy for Quaternary Glacial Deposits: “If It Ain't Broke
    Comment & Reply COMMENTS AND REPLIES of the International Stratigraphic Guide and the NACSN are Online: GSA Today, Comments and Replies similar and that some sort of identifiable homogeneity or unity Published Online: July 2009 in a lithostratigraphic formation is necessary to make lithocor- relation possible. The International Stratigraphical Guide (Salvador, 1994, p. 32) states, “The critical requirement of the unit is the substantial degree of lithologic homogeneity (diversity in detail may in itself constitute a form of overall lithologic unity).” Likewise, Lithostratigraphy for Quaternary the NACSN [2005, article 24, remark (a)] states, “The limits of a formation normally are those surfaces of lithic change that give glacial deposits: “If it ain’t broke, it the greatest practicable unity of constitution,” and [article 24, remark (b)], “A formation should possess some degree of inter- don’t fix it!” nal lithic homogeneity or distinctive lithic features. It may con- tain between its upper and lower limits (i) rock of one lithic type, (ii) repetitions of two or more lithic types, or (iii) extreme M.E. Räsänen, Dept. of Geology, University of Turku, 20014 lithic heterogeneity that itself may constitute a form of unity Turku, Finland, [email protected]; J.M. Auri, Geological Survey of Finland, Vaasantie 6, 67100 Kokkola, Finland; when compared to the adjacent rock units.” J.V. Huitti, A.K. Klap, Dept. of Geology, University of Turku, It is true that the Midwest is an ideal region for lithostratigra- 20014 Turku, Finland; and J.J. Virtasalo, Dept. of Marine phy. But even there the stratigraphic record is, as characterized Geology, Leibniz Institute for Baltic Sea Research, Warnemünde, by Ager (1973), “more gap than record.” So why not use all the Seestrasse 15, D-18119 Rostock, Germany available empirical data to build up a stratigraphic classification and framework? The characteristics of unconformities would then be taken into account to give a hierarchy for the units We thank Johnson et al.
    [Show full text]
  • Lithostratigraphy, Microlithofacies, And
    Lithostratigraphy, Microlithofacies, and Conodont Biostratigraphy and Biofacies of the Wahoo Limestone (Carboniferous), Eastern Sadlerochit Mountains, Northeast Brooks Range, Alaska U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568 j^^^fe^i^^t%t^^S%^A^tK-^^ ^.3lF Cover: Angular unconformity separating steeply dipping pre-Mississippian rocks from gently dipping carbonate rocks of the Lisburne Group near Sunset Pass, eastern Sadlerochit Mountains, northeast Brooks Range, Alaska. The image is a digital enhancement of the photograph (fig. 5) on page 9. Lithostratigraphy, Microlithofacies, and Conodont Biostratigraphy and Biofacies of the Wahoo Limestone (Carboniferous), Eastern Sadlerochit Mountains, Northeast Brooks Range, Alaska By Andrea P. Krumhardt, Anita G. Harris, and Keith F. Watts U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568 Description of the lithostratigraphy, microlithofacies, and conodont bio stratigraphy and biofacies in a key section of a relatively widespread stratigraphic unit that straddles the Mississippian-Pennsylvanian boundary UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1996 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY GORDON P. EATON, Director For sale by U.S. Geological Survey, Information Services Box 25286, Federal Center, Denver, CO 80225 Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Published in the Eastern Region, Reston, Va. Manuscript approved for publication June 26, 1995. Library of Congress Cataloging in Publication Data Krumhardt, Andrea P. Lithostratigraphy, microlithofacies, and conodont biostratigraphy and biofacies of the Wahoo Limestone (Carboniferous), eastern Sadlerochit Mountains, northeast Brooks Range, Alaska / by Andrea P. Krumhardt, Anita G. Harris, and Keith F.
    [Show full text]
  • Prepared By: Dr. Emad Samir Sallam Lecturer of Stratigraphy, Geology Dept., Faculty of Science, Benha University
    Prepared by: Dr. Emad Samir Sallam Lecturer of Stratigraphy, Geology Dept., Faculty of Science, Benha University. - 1 - I) Introduction Sedimentary rocks are formed by materials, mostly derived from the weathering and erosion of the pre-existing rocks (Igneous, metamorphic or even sedimentary rocks), which are transported and then deposited as sediments on the earth's surface. These sediments are then compacted and converted to sedimentary rocks by the process of lithification (rock formation). Diagenesis may be broadly defined as the processes of physical and chemical change which take place within a sediment after its deposition and before the onset of either metamorphism or weathering (Fig. 1). Fig. 1. Rock Cycle - 2 - An important part of applied stratigraphy is the description, classification and interpretation of sedimentary rocks – a study known as sedimentation or sedimentology. A distinction is made between processes of sedimentation (weathering, transportation, deposition, and lithification) and products of sedimentation – sedimentary rocks. A sediment is a deposit of a solid material of earth's surface from any medium (air, water, ice) under normal conditions of the surface. A sedimentary rock is the consolidated or lithified equivalent of a sediment. A description of any sedimentary rock delineates its texture, structure, and composition. Texture refers to the characteristics of the sedimentary particles and the grain-to-grain relations among them. Larger features of a deposit, such as bedding, ripple marks, and concretions, are sedimentary structures. Sediment composition refers to the mineralogical or chemical make-up of sediment. Most sediments are of two main components, a detrital fraction (pebbles, sand, mud), brought to the site of deposition from some source area, or a chemical fraction (calcite, gypsum, and others) formed at/or very near the site of accumulation.
    [Show full text]
  • Chronostratigraphy
    Dr. Maha Al-Hasson Stratigraphy Lectures Chronostratigraphy An elements of stratigraphy that deals with the relative time relations and ages of rock bodies. Chronostratigraphic classification: The organization of rocks into units on the basis of their age or time of origin. Inferential UNITS Groups of strata recognized as being formed during a specific interval of geological time .These units are not self-evident nor directly observable; Chronostratigraphic units: Are bodies of rocks(layered orunlayered), that were formed during a specified interval of a geologic time,they are bounded by synchronous horizons. synchronous horizons(chronohorizon):A stratigraphic surface or interface that is chronous, everywhere of the same age. position within chronostratigraphic unit is expressed by adjectives of position such as; basal, lower, middle, upper, etc.; position within a geochronologic unit is expressed by temporal adjectives such as: early, middle, late, etc. e.g.: lower Cambrian strata/Early Cambrian age middle Cambrian strata/ middle Cambrian strata upper Cambrian strata / late Cambrian strata. 1 Dr. Maha Al-Hasson Stratigraphy Lectures Ranks or types (Hierarchy) of inferential stratigraphic units Chronostratigraphic (Time rock) units Geochronologic (geologic time units) Eon Eonotheme Era Eratheme Period System Epoch Series Age Stage Chron Chronozone Many scientists believe systems & series are units of strata bounded by time surfaces. Stage & Age: all rocks that formed during an age.its a lowest rank of chronostratigraphic unit below series.Age: its' equivalent geochronologic unit, represents their times during rock' deposition . Series & Epochs: Series is achronostratigraphic unit ranking above a stage and below a system,subdivition of System,while Epoch its' equivalent geochronologic unit, representstheir times during rock deposition .
    [Show full text]
  • QUATERNARY SEA LEVEL CHANGE in the CARIBBEAN: the IMPLICATIONS for ARCHAEOLOGY Sherri Baker Littman
    QUATERNARY SEA LEVEL CHANGE IN THE CARIBBEAN: THE IMPLICATIONS FOR ARCHAEOLOGY Sherri Baker Littman ABSTRACT Human habitation of previously subaerial land surfaces is well documented. Geophysical and geological meth­ ods have been applied to elucidate the presence of associated geomorphic features. Records from varved sediments of bottom, anoxic waters yield clues to ancient climate records stored at the bottom of the Cariaco Basin. A sea level curve based upon uranium series (230TH) for Acropora palmata corals off the island of Barbados provides high precision chronology of sea level change since the last glacial maximum. The prograding delta of the Orinoco River has tremendously impacted sites on the island of Trinidad. Tectonic settings, isostasy, coastal hydrodynamics, fluvial and sediment discharge and accumulation rates, along with biostratigraphy and lithos- tratigraphy are necessary to build a valid chronostratigraphy when examining once subaerial archaeological sites. These combined methods provide valuable clues to the "peopling" of the Caribbean and should be employed when searching for prehistoric sites and evaluating settlement models. INTRODUCTION Evidence for Quaternary sea level change has been, at best, tenuous. Since scientific methods for determining sea level change are becoming more widely applied, this scenario is finally beginning to change. Studies show that although sea level has fluctuated eustatically, generalizations regarding specific regions, such as the Caribbean, cannot be made. Hence, this study will briefly examine the regional affects of sea level change on three areas within the Caribbean; the offshore area surrounding the island of Barbados, the Cariaco Basin (offshore Venezuela) and the Orinoco River delta and its affects on the island of Trinidad.
    [Show full text]
  • Chapter 11. Glacial Lithofacies and Stratigraphy
    CHAPTER GLACIAL LITHOFACIES AND STRATIGRAPHY 11 J. Lee British Geological Survey, Nottingham, United Kingdom 11.1 INTRODUCTION Reconstructing the environments, dynamics, and record of past glaciation requires a detailed knowl- edge of both the products of glaciation—effectively the sediments, landforms, and glacitectonic structures that we see in the geological record, and the genetic processes that formed them (Fig. 11.1). Such an understanding of glacial deposits, landforms, and processes underpins our understanding of glacier behaviour, the links between ice masses, climate change, and other feed- back mechanisms, and the applied significance of glaciated terrains from the perspective of resources and geohazards (Fig. 11.1). Building all of this knowledge into a robust geological model requires the employment of a systematic methodology for describing, recording, and interpreting geological evidence. For glacial sediments the principal method, and one routinely employed elsewhere in sedimentology, is the hierarchical lithofacies approach. In turn, understanding how these lithofacies and other glacial features (e.g., landforms and glacitectonic structures) fit together and correlate in both time and space is called stratigraphy. Stratigraphy is a key concept within geology. It enables the development of a framework of events and features that describe both the evolution of a geological succession and how that succession fits into the wider palaeoenvironmental picture or Earth system. Within the context of glacial geology, e.g., a succession of glacigenic sediments and landforms in the Great Lakes region of Canada might document the repeated glaciation of the area. Studying the sediments (lithofacies) and landforms plus their temporal and spatial relationships (stratigraphy), would enable the number of ice advances, their flow directions, and associated geological processes to be reconstructed.
    [Show full text]