Claire Carter
George Donald Eberlein
Michael Churkin Jr.
1970
<div id="abstract-1" class="section abstract"><p id="p-2">The first discovery in North America of a succession of graptolite faunas across the Ordovician–Silurian boundary has been made on Esquibel Island, in south-eastern Alaska, where five graptolite zones are represented in an 18 m interval of shale in the Descon Formation. Despite the thinness of the graptolite zones, no stratigraphical breaks can be inferred from more complete graptolite successions known elsewhere. The Alaskan faunas can be closely correlated with those of the standard British zones—the<span> </span><i>Dicellograptus anceps</i><span> </span>Zone (uppermost Ordovician), the<span> </span><i>Glyptograptus persculptus</i><span> </span>Zone (lowermost Silurian) and the immediately overlying<span> </span><i>Akidograptus acuminatus, Orthograptus vesiculosus</i><span> </span>and<span> </span><i>Monograptus cyphus</i><span> </span>Zones of the Lower Silurian. They thus give evidence of the cosmopolitan distribution of graptolite faunas during latest Ordovician and earliest Silurian time.</p></div>
application/pdf
10.1144/gsjgs.126.1.0319
en
Geological Society of London
Graptolite succession across the Ordovician–Silurian boundary in south-eastern Alaska
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