Oregon Geologic Digital Compilation Rules for Lithology Merge Information Entry
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State of Oregon Department of Geology and Mineral Industries Vicki S. McConnell, State Geologist OREGON GEOLOGIC DIGITAL COMPILATION RULES FOR LITHOLOGY MERGE INFORMATION ENTRY G E O L O G Y F A N O D T N M I E N M E T R R A A L P I E N D D U N S O T G R E I R E S O 1937 2006 Revisions: Feburary 2, 2005 January 1, 2006 NOTICE The Oregon Department of Geology and Mineral Industries is publishing this paper because the infor- mation furthers the mission of the Department. To facilitate timely distribution of the information, this report is published as received from the authors and has not been edited to our usual standards. Oregon Department of Geology and Mineral Industries Oregon Geologic Digital Compilation Published in conformance with ORS 516.030 For copies of this publication or other information about Oregon’s geology and natural resources, contact: Nature of the Northwest Information Center 800 NE Oregon Street #5 Portland, Oregon 97232 (971) 673-1555 http://www.naturenw.org Oregon Department of Geology and Mineral Industries - Oregon Geologic Digital Compilation i RULES FOR LITHOLOGY MERGE INFORMATION ENTRY The lithology merge unit contains 5 parts, separated by periods: Major characteristic.Lithology.Layering.Crystals/Grains.Engineering Lithology Merge Unit label (Lith_Mrg_U field in GIS polygon file): major_characteristic.LITHOLOGY.Layering.Crystals/Grains.Engineering major characteristic - lower case, places the unit into a general category .LITHOLOGY - in upper case, generally the compositional/common chemical lithologic name(s) for the major rock types in the unit, but can also reflect the grain size (for sediments) or the general geomorphological setting (for unconsolidated rocks) .Layering - upper case L followed by lower case describer, describes the thickness/type of bedding .Crystals/Grains - upper case C or G followed by lower case describer, describes the size of the crystals or grains that make up the lithology .Engineering - upper case E followed by lower case describer, describes some of the rock mechanic or outcrop-level structural features of the lithology unc.FLV.Ltc.Gslt_gvl.End = unconsolidated rock, fluvial, thick layering, silt to gravel grains, no data engineering NOTE All of the terms in the different parts of the three merge labels are chosen by the DOGAMI staff and other geologists most familiar with the pertinent area’s formations and lithologies. They reflect the present general understanding within the geologic community of the accepted stratigraphy and lithologies in that part of the state. Thus, the merge units usually reclassify the unit from the map author’s original stratigraphic scheme. The stratigraphic and the lithologic nomenclature cannot be referenced to a single publication’s definition of terms. Instead, they represent the general consensus among geologists, working in a particular area of the state or in a particular field of geology, of a term’s definition at the time of the merge units’ formulation and for that version of the Oregon Geologic Framework Layer. Oregon Department of Geology and Mineral Industries - Oregon Geologic Digital Compilation 1 General rules The geological terms used in the lithology merge name come from the original author’s description of the unit. In some cases, we will opt to use the map unit name and map subunit name to derive the lithology merge unit label. They refl ect the changes in geologic usage through the years. They are descriptive, rather than quantitative, and therefore do not carry any relationship to specifi c engineering defi nitions or geological classifi cations When placed between the abbreviations within each part of the lithology merge unit, the underscore equals “to” and no space between abbreviations equals “and”. Example: f_m=fi ne to medium, fm=fi ne/medium Use only the author’s characterization of the rocks--the major subunit or, if no major/minor subunits are designated, the “nd” subunits (from the map subunit relative abundance fi eld of the Geologic Map Unit name table), to decide on the major characteristics and lithology parts of the lithology merge unit, and whether or not to use a layering, crystals/grains or engineering descriptive term. Do not use the minor subunits. If, based on the major subunits and/or the descriptive information found in the lithology tables, the nature of the unit is still equivocal, then use the author’s original map unit name to help decide on the major characteristics or lithology parts of the lithology merge unit Use “sd” or “some data”, rather than “nd” (no data) within the layering, crystals/grains and engineering describers for the following situation: 1. If any of the major subunit names contain applicable lithology description information (like layer thickness), but that information is not found for all of the major subunits. 2. If none of the major subunits contain information, but it is found in one or more of the minor subunits. An example is a case where one or several minor subunits descriptions contain layering information, because that lithology is usually layered, but the major subunits do not contain any layering information A data rule that applies to the entire database and particularly to the lithology merge portion is that we will consider using the map unit name instead of, or in addition to, the subunit name where the subunit name is not discussed in unit explanation or there is a question as to the author’s intent, e.g. no major or minor subunit is identifi ed. The Glossary of Geology, 4th edition, is the guide for understanding the defi nitions of the geological terms and describers used in the lithology merge unit Oregon Department of Geology and Mineral Industries - Oregon Geologic Digital Compilation 2 major characteristics “Flow rocks”=fl w =used for any unit that consists solely of lava fl ows, and does not contain any volcaniclastic parts (includes vitrophyre) “Interbedded sedimentary rocks”=isx=used for sedimentary rocks (usually as subunits) interbedded with AND, BAS, etc. “Intrusive rocks”=intr=used for masses of rock in which are the major subunit name contains the words “dikes” or “intrusives” “Metamorphic rocks”=met=used for units in which the subunit names are clearly metamorphic lithologies, e.g. schist, amphibolite, gneiss, quartzite, etc. “Plutonic rocks”=plu=used for masses of igneous rocks, basically denoting stocks, batholiths and sills, or for any rock where “dike”or “intrusive” is not clearly named in the subunit name Sediment=sed=used for unconsolidated sedimentary deposits that do not have a geomorphological characterization with them, e.g. “gravel” in map subunit name but no modifi er in map subunit modifi er. “Sedimentary rocks”=srx=used for consolidated sedimentary deposits, and is based on the presence of rock names rather than sediment sizes in the major subunit name (example: sandstone is srx, sand is sed) “Ultramfi c rocks”=umf=used for units in which the major subunit names are clearly ultramafi c lithologies, e.g. dunite, peridotite, pyroxenite, serpentinite, etc. “Unconsolidated rocks”=unc=unconsolidated surfi cial rocks that are described by a geomorphological term in the subunit or map unit names. Includes: alluvium, colluvium, talus, landslide, alluvial fan, eolian, loess, lacustrine, terrace, glacial, deltaic deposits “Sedimentary/Volcanic rocks” =sv= used for basalt fl ows and two or more major and minor sedimentary subunits; use “mix” as the lithology and “CG” for Crystals/Grains. “Volcaniclastic rocks”=vlc=used for unit in which the major subunits contain any type of volcanic particulate rock (tuff, breccia, ash, pyroclastic rocks, cinders, etc.) If a sedimentary subunit is modifi ed by “volcanic”, then it is a volcanic rock, and not a sedimentary rock. If the only major volcanic subunit in an otherwise sedimentary rock is “tuff”, then the unit is an “srx” “Volcanic rocks”=vol= used for a unit in which the major subunits contain both volcanic particulate lithologies and lava fl ows or if the major subunits are named “volcanic, unspecifi ed” Single letters, such as “s”=sedimentary, “p”=plutonic, “v”=volcanic, “i”=intrusive, “u”=ultramfi c, “m”=metamorphic, are used together for a mixture of several different types of major or “nd” Oregon Department of Geology and Mineral Industries - Oregon Geologic Digital Compilation 3 lithologies in the same unit. They are listed in alphabetical order and can be modifi ed by “m” at the end, if the rocks are metamorphosed. “m” at the end of any of the major characteristic units names means that the units or subunits are metamorphosed to some extent. Use an “m” for subunits that are described as foliated, and/or begin with the prefi x “meta”. The description of the metamorphism as “slight”, or hydrothermal or other alteration, or as lineated is not enough, by itself, to modify the major characteristic with “m”. Gabbros and melagabbros are excluded from ultramafi cs unless they are accompanied by other clearly ultramafi c major subunits Peridotites are ultramafi c rocks and include wehrlite Pyroxenites are ultramafi c rocks and include harzburgite, lherzolite, websterite Do not use mélange as a major characteristic term Lithology Abbreviation Argillite, can be “srx” rather than “met”, if it amphibolite amp is the only metamorphic subunit among other andesite and sedimentary subunits. The name, by itself, does aplite apl not mean that the major characteristic name should argillite arg be modifi ed with an “m” ash ash basalt bas basaltic andesite bnd Agglomerate=”tuff” basaltic trachyandesite bta basanite bst Lithology: breccia bxa chert cht All of the letters in the lithology part of the lithology cinder cin claystone cls merge unit name are capitalized, like BAS for conglomerate cgl basalt or GVL for gravel. dacite dac diorite drt Up to two lithologic names are listed in the dunite dun lithology part of the merge unit.