Chondrites targionii (Brongniart, 1828)

Anistoroae, Anca & Miclăuș, Crina, 2015, The Cruziana Ichnofacies In The Lower Member Of The Bisericani Formation (Eastern Carpathians, Romania), Acta Palaeontologica Romaniae 11 (2), pp. 9-23 : 15

Chondrites targionii (Brongniart, 1828)

Material: numerous specimens encountered in siltstone and mudstone beds, throughout the entire sedimentary succession, but mainly in its upper part (from R 17 to R 25, Fig. 2 a-c), were observed in the field.

Description: plantlike ( Fig. 4a ) or featherlike ( Fig. 4b ) branched-pattern of small cylindrical tunnels system; some branches are very long (up to 7 cm; right-upper part of Fig. 4a ) and largely curved. The third order branches are rather short (up to 2 cm) with uniform diameter (no more than 3 mm). Overall the system is from 5 to 12 cm wide. The tunnels fill consist of light-colored mud which contrast with the surrounding dark-colored mudstone.

Remarks: this trace fossils were produced by deep infaunal wormlike tracemakers that may have populated different types of sediment accumulated from littoral to abyssal environment ( Seilacher, 2007).

Chondrites intricatus ( Brongniart, 1823)

Material: Several larger specimens in two mudstone beds of R 17 and R 20 intervals ( Fig. 4c, d ); many smaller specimens throughout the entire analyzed log ( Fig. 4e, f ).

Description: radial system with straight to slightly curved branches at a maximum 20º angle between them, generally looking like an inverted tree. The relative constant diameter of the branches is no more than 1.5 mm. The entire system is around 7 cm wide ( Fig. 4c ). The tunnels fills show dark-colored contrast with the surrounding rock, but also light-colored fills are present ( Fig. 4c, d, e, f ).

Remarks: Chondrites intricatus and Ch. targionni are ethologically diagnosed as deep tier wormlike fodinichnia ( Häntzschel, 1962, 1975; Savrda & Bottjer, 1991), Bromley (1996) suggesting chemichnia as special feeding behavior. They occur in different types of sediments (mudstone and siltstone in the examined section), even those accumulated in low-oxygen conditions, showing a post-depositional character ( Bromley, 1996; Uchman et al., 2012). They are described from littoral to abyssal environments and usually represent the last and the deepest tier in a given bioturbated sequence ( Ekdale et al., 1984; Bromley & Ekdale, 1984; Martin, 2004), although Thalassinoides cross-cutting Chondrites was reported (Rodríguez-Tovar and Uchman, 2006).

Figures

Fig. 2 Upper part of the red and green shale member of the Bisericani Formation (Runcu Brook log) with the labeled intervals “R”. a the lower part of the section; b the middle part of the section; c the upper part of the section

Fig. 4 Trace fossils: a plantlike Chondrites targionii; b featherlike Chondrites targionii; c, d large specimens of Chondrites intricatus; e, f small specimens of Chondrites intricatus; g Planolites in the background mudstone - full relief; h Planolites – positive hyporeliefs; i Planolites with rusty material infill; j Planolites with dark material infill; k Planolites with transversal fine ornamentation.