Miospores and cryptospores from the Silurian section at Allenport, Pennsylvania, USA

Abstract

Non-marine and marine palynomorphs were collected from a Telychian through Gorstian rock outcrop located near Allenport, Pennsylvania, USA in the east-central part of the Appalachian Foreland Basin. Close sampling of the section revealed six distinct palynological assemblages of spores, cryptospores, acritarchs and prasinophycean algae, likely deposited in nearshore marine settings. The Silurian Period is a critical time in plant evolution as megafossils found elsewhere indicate that vascular plants (tracheophytes) originated during this interval. Palynoflorules generally show a transition from cryptospore-dominated to miospore-dominated assemblages during the latter half of the Silurian. This transition is evident at Allenport, where over 30 species of miospores and cryptospores are recognized, including two new species:Vermiverruspora cotteraandRugosphaera falloambita.The sequential progression of innovations in exine structure and sculpture seen in the nonmarine palynomorphs at Allenport closely matches evolutionary patterns documented previously in the Appalachian Basin, Avalonia, and elsewhere around the world.