Ichnofabrics of outer shelf and deep basin deposits have not received much attention. However, analysis of outer shelf Cambrian carbonates of the Basin and Range of the western United States suggests that ichnofabrics were not well developed and that trace fossils are usually confined to bedding surfaces (Droser 1987). In general, extent of bioturbation in these strata increased through the Cambrian (Droser 1987). The Botoman lower Kutorgina Formation at Labaya on the Siberian Platform is likewise relatively unbioturbated. This is consistent with the suggestions that extensive colonization of the deep sea did not occur until the Early Ordovician (Crimes 1994; Crimes and Fedonkin 1994). Deeper-water mudstones remain a fruitful area for research.
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