CHARACTERIZING FLOODPLAIN VEGETATION FROM PLANT ROOT TRACE PATTERNS: CATSKILL FORMATION (UPPER DEVONIAN)

An abundance of Upper Devonian (Frasnian-Femennian) root traces from Catskill-age fluvial deposits near Hepburnville, PA have morphological characteristics that may be useful in paleoenvironmental reconstruction. These, as well as sedimentary structures and features, calcrete, and lithology type, reveal some of the different stresses that acted in this paleoenvironment. The root traces are clay-lined casts, ranging in length from 10 to 45 cm, and are less than 3 mm wide. These root traces occur in two lithologies: a fine-grained, reddish-gray to bluish-gray sandstone and a finer-grained reddish-gray sandstone with calcrete layers. Root traces exhibit branching orientations that are both vertically, downward branching as well as laterally, horizontal branching. A variety of these branching patterns can be found in both lithologies. Vertical branching patterns can be described as tap root systems; these plants may have lived in water stressed environments. Laterally branching root traces may indicate water abundant conditions as well as plants extending their boundaries across the surface. The branching patterns of the root traces can be grouped by similar branching angles and length to branch using IMAGEJ analysis software. Organization of root traces by different branching morphological characteristics and aerial traces may aid in the identification of types of vegetation that occupied the floodplain.

The Catskill Formation in Hepburnville, PA can be described as representing a floodplain colonized by different types of vegetation on which a meandering stream system made its way towards a nearby coastline. The stresses associated with this environment may be reflected by the root trace patterns and other features in the rock.