Fig. 7

Sedimentological and ichnological features. a Fluctuations of bottom currents: lamination (lam.) in the bottom (stagnation, no trace fossils), followed by altered periods of more stagnant/more dynamic (arrowed) current conditions. Changing oxygenation and nutrient delivery is reflected in different morphotypes of Phycosiphon incertum (Ph2, Ph3): small Ph3 (more stagnant conditions) and larger Ph2 (more dynamic conditions), depth 824.0 m. b Enlarged framed fragment of A. c Ichnofabric showing succession (tiering) of the earliest/shallowest Phycosiphon incertum morphotype 2 (Ph2), followed by Thalassinoides (Th) and bivalve burrow (b.b.), 603.6 m. d Cross-bedded (low-angle), very fine sandstone with mudstone intercalations. Bivalve resting trace ?Lockeia (b.b.), 818.67 m. e Thalassinoides burrow systems (Th) in siltstone/sandstone, in places infilled by Phycosiphon incertum morphotype 4 (Ph4)—arrowed. Numerous Phycosiphon incertum morphotype 2 (Ph2) in the background, 823.35 m. f Thalassinoides galleries of tubular burrows (Th, deeper tier), Phycosiphon incertum morphotype 2 (Ph2, shallower tier) in the background, 726.1 m. (g) Trichichnus—pyritized horizontal and oblique, unbranched or branched, thread-like, cylindrical structure produced by bacteria consortium, 712.6 m. h Planolites (Pl—thinner, randomly oriented tubes) and Thalassinoides (Th—larger burrows), 782.7 m. i Post-depositional colonization of a sandstone/grainstone bed with Phycosiphon incertum morphotype 2 (Ph2, earlier stage—shallower tier) and Thalassinoides isp. (Th, later stage—deeper tier), 821.6 m. j Teichichnus (Te, shallow tier) and pyritized, aggregated Trichichnus cylindrical vertical structures (Tr, deeper tier), 850.5 m. k Chondrites (Ch, deep tier) and shallow tier Thalassinoides (Th) and Planolites (Pl), 669.5 m. Scale = 1 cm