The Devonian landscape factory : plant–sediment interactions in the Old Red Sandstone of Svalbard and the rise of vegetation as a biogeomorphic agent

The Devonian Period was a crucial interval in the evolution of plants. During its 60 myr duration, it witnessed the successive evolution of roots, wood, trees and forests. In addition, many of the biogeomorphic phenomena that operate in modern terrestrial environments came online for the first time. The ‘Old Red Sandstone’ of Svalbard consists of a near-continuous Silurian to Late Devonian record of sedimentary environments colonized by land plants and provides a perfect natural laboratory to aid our understanding of the facies signatures and evolution of these phenomena. We describe and illustrate a catalogue of ‘Old Red Sandstone’ features that provide evidence for the stepwise appearance of novel plant–sediment interactions, including preserved plant material and rooting structures, early large woody debris accumulations, cannel coal deposits and the oldest known vegetation-induced sedimentary structures, in addition to vegetation-influenced motifs of elevated mudrock content and complex alluvial sand bodies. These characteristics are combined to reconstruct changes to non-marine environments in this Devonian ‘landscape factory’. In addition to tectonic and climate influences, plant evolution first served as a control on the construction of the sedimentary record during this period and has persisted as a fundamental influence on Earth surface processes and landforms ever since.