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--- correlation [20/03/2023 08:28] – mike_gss
+++ correlation [20/03/2023 08:29] (current) – mike_gss
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 Biozones are the primary tools of correlation. If the fossils used to define them have a short stratigraphic range and widespread distribution (see next section) then we can make a basic assumption:
-**//The same fossils found in two or more separated sections are contemporaneous (evolutions tells us this is so) which means the rocks they are found in are also contemporaneous.//**
+**//The same fossils found in two or more separated sections are contemporaneous (evolution tells us this is so) which means the rocks they are found in are also contemporaneous.//**
 This means we can correlate those sections using true (or very nearly true) timelines that are independent of variable features such as rock thickness and lithology (essential when dealing with sequence stratigraphy), and also we can construct relative timescales based on the order of biostratigraphic events in a basin or region.
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 At the local level, biozonation is often based on fossils organisms which have only limited, local, distribution. Such fossils are still valuable correlation tools, but their geographical applicability is limited. Nevertheless, these fossils need not simply be dismissed when considering larger scale matters. Local biozones can often be calibrated against global “standard” biozones by means of other fossil species who co-existed with both the restricted and the widespread organisms.
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+//Local fossils and biozones based on foraminifera from sections in Oman and Sinai are calibrated to global standard zones defined by ammonites (in this case the Acanthoceras rhotomagense ammonite zone) by the co-occurrence of other ammonites. In this way, the Sequence Boundary (SB) identified in the field is shown to be contemporaneous globally and therefore eustatic in origin.//
 This is useful as it means that we can calibrate locally observed features such as sequence boundaries, flooding surfaces etc. as identified and defined by “local” fossils, to those same features we have seen globally defined by global fossils and therefore place local rock sections within a global stratigraphic framework.