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Which fossil zone marks the base of the Devonian System?
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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.
The base of the Devonian System is marked by the graptolite zone of Monograptus uniformis.12
This boundary, which represents the transition from the Silurian Period to the Lochkovian Stage of the Devonian, is defined by a Global Stratotype Section and Point (GSSP) located at Klonk in the Czech Republic. While the Monograptus uniformis biozone serves as the primary marker, it is reinforced by associated conodont and trilobite taxa to ensure precise stratigraphic correlation.132