Describing krotovinas: A contribution to methodology and interpretation

摘要

Filled mammal tunnels (krotovinas) are the most common traces in modern grassland soils and trace fossils in loess paleosols. Krotovinas are still insufficiently used in paleogeographic reconstructions owing to the absence of a procedure for documenting their features. When their tracemaker can be identified, krotovinas complement body fossil evidence for past geographic ranges of fossorial mammals. Moreover, local palaeoenvironments can be reconstructed more precisely based on the preferred habitat of the identified species. However, the morphology of krotovinas has rarely been reported in detail that would allow their identification.In this article, we suggest five groups of diagnostic features that should be recorded and assessed for taxonomic identification of krotovinas. (1) Ornamentation on the burrow walls, which can be observed when there is sediment compaction contrast between infill and the host material, provides the most taxonomically specific features. (2) Infill type distinguishes between subterranean forms and other burrowers. (3) Tunnel repair and reburrowing patterns. (4) Motifs representing distinctive architectural elements: shafts, spirals, their connections to horizontal tunnels, the shape of chambers, and the predominant orientation of tunnels (horizontal, inclined, vertical). (5) Diameter, which has to be measured transverse to each tunnel or estimated from oblique sections. The measurements and observations can be compared against a reference collection of burrow plaster casts. Synoptic diagrams are suggested as a method for condensing images of diagnostic features from several sections. We suggest that the presence of krotovinas is one criterion for distinguishing grassland paleosols from humus-rich colluvial deposits.