page_title: Perspective geological correlation
section_title: Extension to biostratigraphy
hierarchical_section_title: Perspective geological correlation / Extension to biostratigraphy
caption_attribution_description: English: Ideal LOC
context_page_description: Geological perspective correlation is a theory in geology describing geometrical regularities in the layering of sediments. Seventy percent of the Earth's surface are occupied by sedimentary basins – volumes consisted of sediments accumulated during million years, and alternated by long interruptions in sedimentation. The most noticeable feature of the rocks, which filled the basins, is layering. Stratigraphy is a part of Geology that investigates the phenomenon of layering. It describes the sequence of layers in the basin as consisted of stratigraphic units. Units are defined on the basis of their lithology and have no clear definition. Geological Perspective Correlation is a theory that divided the geological cross-section in units according strong mathematical rule: all borders of layers in this unit obey the law of perspective geometry.
  Sedimentation layers are mainly created in shallow waters of oceans, seas, and lakes. As new layers are deposited the old ones are sinking deeper due to the weight of accumulating sediments.
context_section_description: In 1964 Shaw proposed the method of correlating fossiliferous stratigraphic profiles using the two-axis graph (H) . The markers on each axis are the observed depths of lowest (FAD) and highest (LAD) occurrences of a specially defined group of fossils (taxa).  The appearances/ disappearances of taxa are regarded as synchronous and used as markers of correlation. When projected on a graph, the corresponding points of two compared profiles form the Line of Correlation (LOC).  Shaw showed that the ideal LOC consists of linear segments (H).  Such conditions occur when the number of collected fossils is big, and one can be sure that the material covers the complete range of fossils appearance, and FADs and LADs can be accurately determined. In the reality, some sampled ranges will be shorter than true ranges, and this can disturb the linearity of the LOC.  
  In every stratigraphic interval correlated ends of the range (FAD or LAD) belong to the same time surface, and in each geological cross-section (well or outcrop) this interval has identical duration but different thickness. It means that accumulation rates (thickness-to-duration ratio = tg β) are different in different locations. From the fact that the relation of durations of the units and their thicknesses are linear follows that in the limits of the linear section of LOC all strata have the same accumulation rate. 
  The reliability and accuracy of Shaw's method have been tested by Edwards, using a computer simulation on hypothetical data sets, and by Rubel and Pakin terms of the formal logic and stochastic theory.
  The graphical correlation became a very important tool of stratigraphy in coal and oil industries.
  In 1988 Nemec showed the equivalence of Haites' perspective correlation, and Shaw's graphical correlation
caption: H Ideal Line of Correlation
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