Sedimentology and taphonomy of the Early to Middle Devonian plant-bearing beds of the Trout Valley Formation, Maine

The Trout Valley Formation of Emsian–Eifelian age in Baxter State Park, Maine, consists of fl uvial and coastal deposits that preserve early land plants (embryophytes). Seven facies are recognized and represent deposits of main river channels (Facies 1, 2), fl ood basin (Facies 4), storm-infl uenced nearshore shelf bars (Facies 3), a paleosol (Facies 5), and tidal fl ats and channels (Facies 6, 7). The majority of plant assemblages are preserved in siltstones and are allochthonous and parautochthonous, with only one autochthonous assemblage identifi ed in the sequence above an apparent paleosol horizon. Taphonomic analysis reveals that plant material within allochthonous assemblages is highly fragmented, poorly preserved, and decayed. Plant material within parautochthonous assemblages shows evidence of minimal transport, is well preserved, and shows signs of biologic response after burial. The one autochthonous assemblage contains small root traces. Trimerophytes (Psilophyton and Pertica quadrifaria), rhyniophytes (cf. Taeniocrada), and lycopods (Drepanophycus and Kaulangiophyton) are the most common taxa in estuarine environments. Psilophyton taxa, Pertica, cf. Taeniocrada, and Drepanophycus are found also in fl uvial settings. The presence of tidal infl uence in deposits where parautochthonous and autochthonous assemblages occur shows that these plants occupied coastal-estuarine areas. However, the effects on the growth and colonization of plants of the physical conditions (e.g., salinity) that exist in these settings in the Early to Middle Devonian are unknown.