The former presence of organic matter caused its later absence: Burn‐down of organic matter in oceanic red beds enhanced by bioturbation (Eocene Variegated Shale, Carpathians)

Abstract

Eocene oceanic red beds that formed in a well‐oxygenated setting at low sedimentation rates below the calcite compensation depth are effectively barren of organic carbon in the present state. Recurrent distal low‐erosive turbidites preserve the bioturbated zone underneath that documents seasonal and long‐term fluctuating accumulation of considerable amounts of organic matter on the sea floor as evidenced by Scolicia; the producers of this trace fossil exploited nutritious organic matter conserved in turbidite‐buried sea floor deposits. Over the long‐term, slow average sedimentation of (hemi)pelagic oxic (red) mud led to long oxygen exposure times and low burial of organic matter. Consequently, trace fossils representing persistent sediment‐feeding modes are of small size. Although the food‐limited setting appears appropriate for producers of graphoglyptids, such ‘stationary’ burrows have not been encountered because seasonal deposition of organic matter fostered at least temporary surface layer feeding organisms, for instance producers of Nereites irregularis that intensively reworked the sediment and, hence, hindered graphoglyptid production. These findings confirm palaeoceanographic modelling results that suggest upwelling in the study area during the Eocene.

Large cruzianid trace fossils in the Ordovician of the peri-Baltic area: the case of the Bukówka Formation (Holy Cross Mountains, Poland)

“…Ingall and Cappellen, 1990). Low sed i men ta tion rate causes a low burial rate of organic mat ter (Müller and Suess, 1979;Jung et al, 1997;Löwemark et al, 2006) which is con cen trated shal lowly in the sed i ment, con sumed and burnt down in oxic en vi ron ments (Wetzel and Uchman, 2017). Ac cord ingly, a higher sed i men tation rate causes deeper burial of or ganic mat ter, which at tracted bur row ing or gan isms.…”

Deep-Sea Echinoid Trails and Seafloor Nutrient Distribution: Present and Past Implications

“…Instead, Seilacher (2007) proposed meandering traces as a reflection of more efficient foraging behavior, in which trace makers avoided areas they had already exploited. The presence of surfaces fully covered with echinoid trace fossils (e.g., Scolicia) suggests that the exploited area likely contained a considerable amount of organic matter (Wetzel and Uchman, 2018). The occurrence of large echinoid trails with guided meanders is best explained by an optimized exploitation of high-nutrient value benthic food (Kröncke, 2006;.…”

“…The relationship between ichnological features and organic carbon distribution in the deep-sea, mainly focusing on echinoid trails, is comparatively better studied (Wetzel, 2008;Seike et al, 2020). For example, a considerable amount of organic matter (e.g., organic carbon content) is associated with guided meanders of large echinoid trails (Wetzel and Uchman, 2018). Although previous studies reveal that trails left behind by echinoids can represent searching behaviors and nutrient distribution (Sims et al, 2014), this research is still in its early stages.…”

The Upper Cretaceous variegated shales in the Ropianka Formation of the Magura Nappe (Outer Carpathians) – age and lithostratigraphic position

“…The varie gated shales were de pos ited in deep-wa ter con di tions with a share of sus pen sion. They orig i nated dur ing pe ri ods of lim ited de liv ery of clastic ma te rial to the sed i men tary ba sin and de posited in well-ox y gen ated en vi ron ments (e.g., Leszczyñski and Uchman, 1991;Waoekowska-Oliwa, 2000;Wetzel and Uchman, 2018). In the Carpathian sed i men tary ba sin, dom i nated by turbiditic sed i men ta tion, these con di tions were not fre quent.…”