A uniform approach to ichnotaxonomy has been for the most part positively received by the scientific community. We carry it further here, presenting a revised treatment of trace fossil groups. These should include cololites and regurgitalites as well as ...

A number of biogenic processes leads to the formation of distinctive traces in terrestrial lithic substrates. These include: burrowing by vertebrates in moderately lithified rocks; scraping by mammals; smoothing and polishing of limestone surfaces by the locomotion of mammals; excavation by bees, wasps, and ants producing nesting and dwelling tunnels; dissolution of limestone surfaces by terrestrial snails; endolithic activity of fungi, algae, and lichens on subaerial rock surfaces; root corrosion; etc. Processes of biochemical weathering, biophysical erosion, and enlargement of cracks and fissures by the pressure of plant roots do not leave distinctive traces and therefore lie outside the ichnological realm. The fossil preservation of terrestrial bioerosional traces is expected to be uncommon. Nevertheless, various possible means of preservation must be considered, such as by rapid burial by volcanic material, by fluvial sediments, by travertine or tufa, by loess, “conservation”; in caves, case hardening of surfaces of porous rocks, and preservation of subsoil traces below fossil soils.

Trace fossils are abundant in the Cambrian Kunzam La Formation in the Lahaul and Spiti regions of the Himalaya. All previously known records belong stratigraphically to the upper part of the Cambrian Series 2/Stage 4 to the Miaolingian Series. In the present work, 15 ichnogenera comprising 26 recorded ichnospecies come from the lower part of the Kunzam La Formation exposed in the Chandra Valley, eastern Lahaul and Spiti, Himachal Pradesh. Three trace fossils associations, based on their sequence of appearance, are: (i) the Treptichnus pedum association (trace fossil association–I)-, a low diversity association, containing Planolites beverleyensis, Palaeophycus isp., and Treptichnus pedum, (ii) the Monomorphichnus association (trace fossil association–II) characterized by a sudden increase in trace fossil diversity and traces of arthropod/trilobite origin comprising Cruziana problematica, Cruziana isp., Catenichnus contentus,? Diplocraterion isp., Dimorphichnus obliquus, Dactylophycus isp., Lockeia siliquaria, Monomorphichnus multilineatus, M. lineatus, Planolites annularis, P. montanus, P. beverleyensis, Palaeophycus imbricatus, P. tubularis, Rusophycus didymus, R. leifeirikssoni, R. dispar, Rusophycus isp., Saerichnites abruptus, and serially repeated Rusophycus and Cruziana, Treptichnus pollardi and arthropod resting traces, and (iii) the Psammichnites association (trace fossil association–III) characterized by a dominant presence of large burrowing systems of Psammichnites gigas and traces of Diplichnites isp. and Ctenopholeus kutcheri. Considering the same rate of sedimentation for these deposits determined in the >50 km distant Parahio Valley and the stratigraphic position of the Psammichnites gigas assemblage zone in the Himalaya, these trace fossil associations probably fall within Cambrian Series 2, Stage 4, though the sudden increase in diversity and complexities of traces suggest an older age. Stratigraphically, the trace fossils presently described are the oldest yet recorded from the Cambrian of the Lahaul and Spiti regions.

Benefits and limits of x-ray micro-computed tomography for visualization of colonization and bioerosion of shelled organisms

An assemblage of trace fossils comprising Asteriacites stelliformis, A. quinquefolius, Biformites insolitus, Helminthoidichnites? isp., Lingulichnus isp., Lockeia siliquaria, Palaeophycus tubularis, Planolites isp., Protovirgularia isp. A, Protovirgularia isp. B, Protovirgularia isp. C, Psammichnites isp., Rusophycus isp., and Treptichnus isp. from the Po Formation (Visean-Serpukhovian) exposed along the base of Ganmachidam Hill near the village of Chichong, Spiti Valley in the Himalaya, is described. Storm beds (tempestites) are highly bioturbated. Sedimentary structures such as hummocky cross-stratification (HCS), low-angle planar and trough cross beds, and shallow, slightly asymmetrical gutter casts are observed. The overall trace fossil assemblage indicates the presence of upper shoreface to lower shoreface Cruziana ichnofacies of an open shelf.