Strat

• Stratigraphy


  The study of rock layers and the sequence of events they reflect
• Sedimentology


  The science that deals with the description, classification, and origin of sedimentary rock
• Chemostratigraphy


  Correlation of strata using ratios of chemical isotopes
• Magnetostratigraphy


  The comparison of the pattern of magnetic reversals in a sequence of strata, with a reference column showing the succession of reversals through time
• Angle of repose


  The steepest angle at which loose material remains stationary without sliding downslope
• Facies


  A body of rock characterized by a particular combination of lithology, physical, and biological structures that bestow an aspect different from the bodies of rock above, below and laterally adjacent
• Lithologic correlation


  Matching rocks of the same character from one place to another
• Sedimentary logs are one-dimensional representations of vertical sedimentary successions
• Polymict


  Contain an assortment of many kinds of clasts
• Metamict


  A state in which a material has become almost amorphous (non-crystalline) due to the breakdown of the original crystal structure by radioactivity within the material, e.g. zircon
• Walther's Law


  States that the vertical succession of facies reflects lateral changes in environment
• Johannes Walther, a German geologist in 1894, noted a fundamental relationship between the vertical and lateral distribution of facies
• Transgression or sea level rise


  Will produce a vertical sequence of facies representing progressively deeper water environments. As a result, this sequence will have finer-grained facies overlying coarser-grained facies (fining-upward from sand at the bottom, then to silt, then to shale)
• Regression


  This produces a sequence of facies representing progressively shallower water environments. As a result, this type of sequence will have coarser-grained facies overlying finer-grained facies (coarsening upward)
• Progradation


  Outward extension of the shoreline through deposition of sediment
• Retrogradation


  "Backstepping" of shoreline
• Accommodation space


  Space available for sediment to accumulate vertically
• International Commission on Stratigraphy (ICS) is responsible for maintaining the official timetable of earth's history
• International Subcommission on Stratigraphic Classification is responsible for the publication of the International Stratigraphic Guide which helps promote international agreement on principles of stratigraphic classification and to develop an internationally acceptable stratigraphic terminology and rules of procedures in the interest of improved accuracy and precision in international communication, coordination, and understanding
• Stratigraphic unit


  A naturally occurring body of rock or rock material distinguished from adjoining rock on the basis of some stated property or properties: Composition, Texture, Included fossils, Magnetic signature, Radioactivity, Seismic velocity, Age
• Lithostratigraphic ranks of units

  Group – two or more formations

  Formation – primary unit of lithostratigraphy

  Member – named lithologic entity within a formation

  Bed – named distinctive layer in a member or formation

  Flow – smallest distinctive layer in a volcanic sequence
• Lithodemic units are defined bodies of predominantly intrusive, highly deformed, and
• Lithostratigraphic ranks of units:Group – two or more formations

  Formation – primary unit of lithostratigraphy

  Member – named lithologic entity within a formation

  Bed – named distinctive layer in a member or formation

  Flow – smallest distinctive layer in a volcanic sequence
• Lithodemic units are defined bodies of predominantly intrusive, highly deformed, and/or highly metamorphosed rock, distinguished and delimited on the basis of rock characteristics. They do not conform to the Law of Superposition
• Lithostratigraphic unit is a body of sedimentary rock, such as a formation, defined solely by its physical attributes
• Biostratigraphic unit is a unit of sedimentary rock defined solely by its fossil content
• Chronostratigraphic unit is a body of rock established to serve as the material reference for all rocks formed during the same span of time
• Geochronologic unit is a division of time distinguished on the basis of the rock record preserved in a chronostratigraphic unit
• Correlation is determining correspondence between geographically separated parts of a geologic unit
• Stratotype is the standard for a named geologic unit or boundary and constitutes the basis for definition and recognition of that unit or boundary
• Unit stratotype is the type section of a layered stratigraphic unit that serves as the standard of reference for the definition and characterization of the unit
• Global Stratotype Section & Point (GSSP) is the selected type or standard for the definition and recognition of a stratigraphic boundary between two named standard chronostratigraphic units
• Paraconformity has no major erosional surface while disconformity has a major erosional surface, but both have parallel layers
• Intertonguing is the lateral splitting of a lithologic unit into many thin units to extinction
• Pinch out is when rock thins progressively to zero
• Lithodemic is applicable to a defined body of predominantly intrusive, highly deformed, and/or highly metamorphosed rock, distinguished and delimited on the basis of rock characteristics
• Suite comprises two or more associated lithodemes of the same class
• Complex is used for igneous and/or metamorphic rock bodies of diverse and irregularly mixed lithology, whether or not they are strongly deformed and/or metamorphosed.
• Melange is a mass of chaotically mixed brecciated blocks in a highly sheared matrix
• Interval zones are bounded by 2 first or last occurrences