Fig. 5. Sedimentological characteristics of the Stainmore Formation at the southern end of Howick Bay, attesting to lower delta plain deposition. (a) Rotated view of fallen block hosting fossil at starred horizon, showing lithology of amalgamated trough cross-beds of fine sandstone, coarsening upwards from laminated very fine sandstone and siltstone. Located at c. 8–10 m on stratigraphic log in Figure 3d. Scale bar 20 cm. (b) Casts of syneresis cracks on underside of fallen block. Located at 8 m on stratigraphic log in Figure 3d. Scale bar 10 cm. (c) Detail of cross-bedded sets in which Arthropleura fossil was interred. Note clasts of coaly debris. Located at 9.5 m on stratigraphic log in Figure 3d. Ruler 20 cm. (d) Crudely developed rhythmites of probable tidal origin, colonized with Skolithos (Sk) and Teichnichnus (Te) burrows. Located at 6 m on stratigraphic log in Figure 3d. Scale bar 15 cm. (e) Inclined heterolithic stratification in form of lateral accretion set of small tidal channel; northwards direction of migration arrowed. Located at 1.5 m on stratigraphic log in Figure 3d. Scale bar 70 cm. (f) Incised channel filled with braided alluvium and cutting into underlying sequence at far southern end of Howick Bay. Approximate channel base highlighted. The channel truncates the sequence illustrated in Figure 3d. Scale bar 2 m.

Published as part of Davies, Neil S., Garwood, Russell J., McMahon, William J., Schneider, Joerg W. & Shillito, Anthony P., 2021, The largest arthropod in Earth history: insights from newly discovered Arthropleura remains (Serpukhovian Stainmore Formation, Northumberland, England), pp. 1-18 in Journal of the Geological Society (jgs2021-115) 179 (3) on page 5, DOI: 10.1144/jgs2021-115, http://zenodo.org/record/5801508