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

Abstract

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.

Autochthony and orientation patterns in Olduvai Bed I: a re-examination of the status of post-depositional biasing of archaeological assemblages from FLK North (FLKN)

“…Further, to practitioners of these historical sciences "primary position" typically implies a "Pompeian scenario", a most rare situation given that the vast majority of known sites show various degrees of disturbance, even those that are autochthonous. Autochthony is thus defined as occurring in the same location where deposited, whereas allochthony implies significant post-depositional modification, with embedding or burial of items in a different location than where initially deposited (Callender and Powellm, 1992;Jacobs and Winkler, 1992;Jenkins, 1992;Callender et al, 1994;Darrah, 1995;Farinati and Zavala, 1995;Rasser and Nebelsick, 2003;Allen and Gastaldo, 2006;Jones, 2006;Martin, 2006). More precisely, autochthonous entities are defined as located within the area of production (deposition), even though, in some cases, they may have been subsequently rearranged within this area (Fernández-López, 1990;Alcalá, 1994).…”

Considering river structure and stability in the light of evolution: feedbacks between riparian vegetation and hydrogeomorphology

“…Such floristic contrasts were a response to the diversification of conditions for submersion frequency and duration, sediment erosion/deposition and nutrient availability (Allen and Gastaldo, 2006). Such floristic contrasts were a response to the diversification of conditions for submersion frequency and duration, sediment erosion/deposition and nutrient availability (Allen and Gastaldo, 2006).…”

“…In part due to these biogeomorphic feedbacks between vegetation evolution and geomorphology, by the Middle Devonian riparian ecosystems began to be partitioned along the longitudinal, transverse and vertical dimensions. Such floristic contrasts were a response to the diversification of conditions for submersion frequency and duration, sediment erosion/deposition and nutrient availability (Allen and Gastaldo, 2006). This floristic and geomorphic partitioning certainly involved a strong feedback between engineer plants affecting water flow, sedimentation and landforms and their evolutionary trajectory.…”

“…Biomechanical traits promoting this habit include a high resistance to breakage and flexibility of roots and aerial structures that permitted plants to modulate the geomorphic setting in the most active zones of the river corridor. For example, calamitalean sphenopsids were adapted to hydrogeomorphic disturbance and sediment burial, with diverse propagation modes and the possibility of clonal growth after breakage (Gastaldo, 1992;Pfefferkorn et al, 2001;Allen and Gastaldo, 2006). Such plants may have spread upstream along the energy gradient, and consequently may have contributed to the modulation of fluvial landforms directly from inside river channels along both longitudinal and transverse river dimensions.…”

Siluro-Devonian landscapes of southern Britain: the stability and nature of early vascular plant habitats

“…Initial attempts at this have focused on the palaeobotany with minimal sedimentological details (Andrews et al 1977;Gensel & Andrews 1984;Edwards & Fanning 1985). A few integrated studies have been conducted (Jarvis 2000;Powell et al 2000), including investigations on the Lower Devonian fluvial successions at Gaspé Bay, Canada (Griffing et al 2000;Hotton et al 2001) and in Maine, USA (Allen & Gastaldo 2006), where fossil assemblages are placed in a palaeogeomorphological context. As a result of this integrated approach, Hotton et al (2001) and Allen & Gastaldo (2006) recognized that plant communities during the Emsian comprised patches of monospecific stands, each with specific depositional settings, a hypothesis first presented by DiMichele & Hook (1992).…”