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--- which_fossils [20/03/2023 08:37] – mike_gss
+++ which_fossils [20/03/2023 09:30] (current) – mike_gss
@@ Line 37: / Line 37: @@
 Such an organism would have a distribution in space and time (called the “biochronal envelope”) like this…
+{{:which_fossils01.jpg?nolink|}}
+//Character of an "ideal" biostratigraphic fossil – short-ranging and widely spread.//
 Unfortunately, no such organisms exist! In reality, organisms are not so helpful for the poor biostratigrapher. A more typical “biochronal envelope” (the red box above) is more likely to have this appearance…
+{{:which_fossils02.jpg?nolink|}}
+//Biochronal envelope of a more "typical" organism.//
 …and the characteristics of this organism would be more like…
@@ Line 65: / Line 71: @@
   * may become locally extinct due to local environmental factors whilst persisting elsewhere
-However, even zonation based on planktonic organisms can be subject to spatial and temporal variations due (mainly) to environmental effects.
+However, even zonation based on planktonic organisms can be subject to spatial and temporal variations due (mainly) to environmental effects:
+{{:biostratigraphy06.jpg?nolink|}}
+//Standard Neogene planktonic foram zonation showing latitudinal variations (from McGowran, 2005).//