Sedimentological and plant taphonomic evaluation of the early Middle Devonian Trout Valley formation

The Trout Valley Formation of Emsian-Eifelian age, outcropped in Baxter State Park, Maine, consists offluvial and coastal deposits preserving early land plants. Massive, crudely bedded conglomerate represents deposits of proximal braided channels on an alluvial fan complex. Lithic sandstone bodies in channel-form geometries represent deposits of river channels draining the Acadian highlands whereas associated siltstones represent overbank deposits, intertidal flats, and tidal channels. Localized lenticular quartz arenites represent nearshore shelf bar deposits that were storm influenced. The majority of plant assemblages preserved mainly in siltstone lithologies are allochthonous and parautochthonous, with only one autochthonous assemblage identified in the sequence. Plant remains are found in both fluvial and estuarine environments with trimerophytes (Psilophytons and Pertica quadrifaria), rhyniophytes (Taeniocrada) and lycopods (Drepanophycus and Kaulangiophyton) as the most common plants in estuarine environments near tidal channels. However, they are found also in fluvial settings. The presence of tidal influence in deposits where parautochthonous and autochthonous assemblages are preserved suggests that these plants may have been tolerant of brackish conditions. However, the effects of this physical parameter on the growth and colonization of plants in the Middle Devonian is unknown.