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In the stratigraphy sub-discipline of geology, a Global Standard Stratigraphic Age, abbreviated GSSA, is a chronological reference point and criterion in the geologic record used to define the boundaries (an internationally sanctioned benchmark point) between different geological periods, epochs or ages on the overall geologic time scale in a chronostratigraphically useful rock layer.
The Foraminiferal Colouration Index [1] [2] (FCI) is a tool for assessing the thermal alteration of organic matter buried in sedimentary rock.It uses temperature-controlled colour changes in the organic cement of agglutinated foraminifera (microfossils) to estimate thermal alteration.
Color index, as a geological term, is a measure of the ratio between generally dark mafic minerals and generally light felsic minerals in an igneous rock. [1] [2] The color index of an igneous rock is the volume percentage of mafic minerals in the rock, excluding minerals generally regarded as "colorless" such as apatite, muscovite, primary ...
The geologic time scale, proportionally represented as a log-spiral with some major events in Earth's history. A megaannus (Ma) represents one million (10 6) years.. The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth.
Federal Standard 595 is the color description and communication system developed in 1956 by the United States government. Its origins reach back to World War II when a problem of providing exact color specifications to military equipment subcontractors in different parts of the world became a matter of urgency.
The first set of commonly used mineral symbols was published in 1983 and covered the common rock-forming minerals using 192 two- or three-lettered symbols. [1] These type of symbols are referred to as Kretz symbols. More extensive lists were subsequently made available in the form of publications [2] [3] or posted on journal webpages. [4]
Felsite is a field term for a light-colored rock that typically requires petrographic examination or chemical analysis for more precise definition. Color is generally white through light gray, or red to tan and may include any color except dark gray, green or black (the colors of trap rock ). [ 1 ]
The Devonian Old Port Formation is a mapped bedrock unit in Pennsylvania, USA.Details of the type section and of stratigraphic nomenclature for this unit as used by the U.S. Geological Survey are available on-line at the National Geologic Map Database. [2]