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Trace fossils and ichnofabrics were recognized in the Middle to Upper Devonian deposits of the East European Platform at the Onega Lake (NW Russia), developed as the Old Red Sandstone facies. The studied sequence is aged from the upper Givetian to the Middle Frasnian. The most diverse ichnoassemblage was ascertained in the earliest Frasnian (lower to middle part of the Andoma Formation), comprising the ichnogenera ?Arenituba, Cochlichnus, Cruziana, Diplocraterion, Lockeia, Palaeophycus, Planolites, Rusophycus, Skolithos, Teichichnus, and Undichna. Combination of ichnologic and sedimentary data points to the assumption that these deposits probably originated in wave- and tide-influenced environments, possibly in a brackish-water estuary. Towards the middle Frasnian, Skolithos-like trace fossil dominate; the ichnoassemblage can be attributed to the tidally influenced channels and bars. [ABSTRACT FROM AUTHOR]

Lukševičs, E., Ahlberg, P.E., Stinkulis, Ģ., Vasiļkova, J. & Zupiņš, I. 2011: Frasnian vertebrate taphonomy and sedimentology of macrofossil concentrations from the Langsēde Cliff, Latvia. Lethaia, Vol. 45, pp. 356-370. The siliciclastic sequence of the Upper Devonian of Kurzeme, Western Latvia, is renowned for abundant vertebrate fossils, including the stem tetrapods Obruchevichthys gracilis and Ventastega curonica. During the first detailed taphonomic study of the vertebrate assemblage from the Ogre Formation cropping out at the Langsēde Cliff, Imula River, abundant vertebrate remains have been examined and identified as belonging to one psammosteid, two acanthodian and three sarcopterygian genera; the placoderm Bothriolepis maxima dominates the assemblage. Besides fully disarticulated placoderm and psammosteid plates, separate sarcopterygian scales and teeth, and acanthodian spines, partly articulated specimens including complete distal segments of Bothriolepis pectoral fins, Bothriolepis head shields and sarcopterygian lower jaws have been found. The size distribution of the placoderm bones demonstrates that the individuals within the assemblage are of approximately uniform age. Distinct zones have been traced within the horizontal distribution of the bones. These linear zones are almost perpendicular to the dominant dip azimuth of the cross-beds and ripple-laminae and most probably correspond to the depressions between subaqueous dunes. Concavity ratio varies significantly within the excavation area. The degree of fragmentation of the bones and disarticulation of the skeletons suggest that the carcasses were reworked and slightly transported before burial. Sedimentological data suggest deposition in a shallow marine environment under the influence of rapid currents. The fossiliferous bed consists of a basal bone conglomerate covered by a cross-stratified sandstone with mud drapes, which is in turn overlain by ripple laminated sandstone, indicating the bones were buried by the gradual infilling of a tidal channel. All the Middle-Upper Devonian vertebrate bone-beds from Latvia are associated with sandy to clayey deposits and have been formed in a sea-coastal zone during rapid sedimentation episodes, but differ in fossil abundance and degree of preservation. □ Agnathans, Devonian, facies analysis, fish, fossil assemblage, palaeoenvironment. [ABSTRACT FROM AUTHOR]