Non‐palimpsested crowded Skolithos ichnofabrics in a Carboniferous tidal rhythmite: Disentangling ecological signatures from the spatio‐temporal bias of outcrop

Abstract

A heterolithic tidalite succession yielding spring–neap bundles is newly reported from a mid‐Carboniferous (Serpukhovian) section of the Alston Formation of Northumberland, England. The rhythmite records deposition over an interval that can be confidently calibrated to at least 84 lunar days, and attests to a non‐negligible tidal range in parts of the Northwest European Seaway in the late Mississippian. The tidalite is notable for the presence of a striking crowded Skolithos ichnofabric on both bedding planes and in vertical section. Bedding plane expressions of the ichnofabric reveal true substrates of sand piles excavated during burrow construction, in addition to an apparently remarkable equal spacing between individual burrows that is shown to be genuine through pair correlation function analysis. These characteristics show that the burrowed horizons were registered by contemporaneous ichnocoenoses, with no palimpsesting of burrows. The irregular vertical distribution of burrow horizons, despite a near‐continuous semi‐diurnal record of sedimentation, is suggested to be an artefact of spatial patchiness of burrowing communities in the depositional environment; imperfectly registered in a vertical profile with high‐temporal, low‐spatial resolution. The succession proves that burrow palimpsesting is not an inevitable ichnological conclusion of sedimentary stasis, and attests to intermittent palaeoecological fidelity of the stratigraphic record at the small spatio‐temporal scales recorded at outcrop.

Deep Time Biogeomorphology: The Co-Evolution of Life and Sediments

“…The counterintuitive nature of such incidents has traditionally provoked a demand for special explanation: standing Carboniferous trees have been accounted for by rapid subsidence (Bailey, 2011) and apparently contemporaneous communities of burrows on shared substrates have been dismissed as implausible (McIlroy and Garton, 2010). Yet both these instances have been shown to be more readily explainable as mundane artefacts of the relationship between the time-length scales of ancient environments and present day outcrop (Miall, 2015;Holbrook and Miall, 2020;Allport et al, 2022). Fundamentally this means that they are not surprising or exceptional: rather, they are examples of what Paola et al (2018) termed the "strange ordinariness of the stratigraphic record".…”

The largest arthropod in Earth history: insights from newly discovered Arthropleura remains (Serpukhovian Stainmore Formation, Northumberland, England)

“…Most of the strata exposed at Howick Bay belong to the Visean Alston Formation (Fig. 3) and are typified by marine limestones and storm-and tide-deposited siliciclastic strata (Reynolds 1992;Booth et al 2020;Allport et al 2021). At the southern end of the bay, the Howick Fault juxtaposes these against the younger strata of the Stainmore Formation, in which the fossil was discovered, which yield a greater abundance of signatures of non-marine deposition among less frequent limestones and tidally influenced siliciclastic strata.…”