Megabeds in Istrian Flysch as markers of synsedimentary tectonics within the Dinaric foredeep (Croatia)

Istrian Flysch was deposited during the Eocene in the Dinaric foredeep and is composed of hemipelagic marls and various gravity flow deposits. The latter are predominantly 5-40 cm thick turbidites, developed mostly as laminated and cross-rippled sandstone beds (Tb-e, Tc-e and Td-e Bouma sequences). In addition to the turbidites, there are deposits characterized by a significant thickness, occasionally more than 10 m, described as complex (bipartite) megabeds. The megabeds are composed of debrites in the lower part (Division I), and high-density turbidites in the upper part (Division II). The distinct clast composition of each megabed indicates that the lithoclasts were derived from tectonically active slopes and fault scarps along which collapses of the different parts of the Cretaceous to Palaeogene neritic carbonate succession, (that underlie the Flysch), occurred. The Division II deposits are well cemented, normally graded calcirudite/calcarenites composed mostly of orthophragminids, nummulitids, and red algae, originating from outer ramp environments. Redeposited marl, observed in the matrix of the debrites and as intraclasts in some megabeds, implies that the collapses along the synsedimentary fault scarps and steep slopes also occurred within the foredeep itself, during the rapid tectono-sedimentary evolution of the Dinaric foreland basin.

The Late Devonian placoderm <i>Aspidichthys</i> Newberry, 1873 from the Holy Cross Mountains, Poland

The reported placoderm remains from the Holy Cross Mountains, Poland, belong to the species Aspidichthys ingens Koenen, 1883. This study focuses on the material described in the past from Wietrznia Quarry but the new specimens were also collected form Kowala and Płucki localities. All specimens presented here differ from others described in the past, mainly by having smaller tubercles and possessing a distinctive crest in the anterior median part of the median dorsal plate, but did not allow the erection of a new taxon. Based on conodont assemblage, all specimens are attributed to a Frasnian age. Aspidichthys occurs in the middle to the upper part of the Frasnian (Palmatolepis punctata to P. linguiformis conodont zone) and is not found in the Famennian boundary. Described specimens also occur in a stepwise deepening environment caused by local synsedimentary tectonics.

El Ordovícico en el área de Los Barrios de Luna, Cordillera Cantábrica (NW de España)

Resumen: El estudio cartográfico y estratigráfico del Ordovícico en el área de Los Barrios de Luna (flanco sur del Sinclinal de Abelgas-Alba), ha permitido reconocer una compleja estratigrafía, con­dicionada por una tectónica sinsedimentaria, probablemente relacionada con el intenso vulcanismo que se observa algo más al este. Se revisa la estratigrafía de la Fm. Barrios, de edad Cámbrico Medio a Tardío en su mayor parte. Se redenomina una unidad estratigráfica informal (capas de El Vento­rrillo), del Ordovícico Temprano?, Medio y Tardío. Se definen formalmente dos formaciones en el Ordovícico Superior-Silúrico basal? (Caliza de La Devesa y Cuarcita de La Serrona), y se precisa la estratigrafía de la unidad informal silúrica capas de Getino. Las costras ferruginosas situadas en la base de las capas de El Ventorrillo y de las capas de Getino se interpretan como originadas por alteración de materiales volcánicos.Palabras clave: Ordovícico, cartografía, estratigrafía, costras ferruginosas, tectónica sinsedimenta­ria, rifting, Cordillera Cantábrica, Macizo Ibérico.Abstract: The mapping and stratigraphic study of the Ordovician rocks in Los Barrios de Luna area (southern limb of Abelgas-Alba Syncline), allowed us to recognize a complex stratigraphy, conditio­ned by a synsedimentary tectonics, probably related to the intense volcanism observed further east. The stratigraphy of the Barrios Fm., mostly Middle to Late Cambrian age, is reviewed. An informal stratigraphic unit (El Ventorrillo beds), of Early?, Middle to Late Ordovician age, is renamed. Two Upper Ordovician-basal Silurian? formations are formally defined (La Devesa Limestone and La Serrona Quartzite), and the stratigraphy of the Silurian informal unit Getino beds is refined. The ferruginous crusts at the base of El Ventorrillo beds and Getino beds are interpreted as a result of alteration of volcanic materials.Key words: Ordovician, cartography, stratigraphy, ferruginous crusts, synsedimentary tectonics, rifting, Cantabrian Mountains, Iberian Massif.