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Why were Devonian corals less reliable than conodonts for dating rock layers?
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Devonian Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the early Devonian Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
In the context of Devonian geochronology, corals are considered less reliable than conodonts for dating rock layers because they were highly sensitive to local environmental changes.1
While conodonts are prized as index fossils due to their rapid evolution, widespread geographic distribution, and ability to define precise geologic time zones, corals often exhibit distribution patterns heavily influenced by their immediate surroundings. This environmental sensitivity makes corals poor indicators of specific time intervals compared to the more consistent and globally correlated conodont assemblages.231