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Geochemistry and petrology of the Upper Silurian greywackes from the Holy Cross Mountains (central Poland) : implications for the Caledonian history of the southern part of the Trans-European Suture Zone (TESZ)

Kozłowski W., Domańska-Siuda J., Nawrocki J.

Geological Quarterly

2014

Vol. 58, No. 2

311--336

The Ludlovian greywackes of the Holy Cross Mountains (HCM) represent a part of the sedimentary cover of the Łysogóry and Małopolska terranes located in the Trans-European Suture Zone, central Poland. The rocks form the sedimentary infill of the Caledonian foreland basin that developed at the Tornquist margin of Laurussia and had source-areas located on the orogen side of the basin. Until the present, the source terrane of the basin has not been identified in its potential location – at the south-west margin of the East European Platform. The Ludlovian greywackes of both parts of the HCM show a lot of similarities in clast spectrum, timing, and geochemical features, which implies similar sources of the clastic material. The petrographic modal composition and geochemical features indicate recycled orogen signatures with a distinct undissected, evolved magmatic arc component. The latter is particularly evident from the extraclast spectrum that contains andesite, trachyte and dacite clasts. Beside the volcanic rocks, the source area consisted of sedimentary and metasedimentary rocks with high amounts of cherts. The geochemical and petrological features in the rock succession point to an evolution of the tectonic setting from an active to a more passive margin type indicating synorogenic formation of the studied rocks. Based on the rock record, we suggest that the Upper Silurian greywackes originated as a result of the collision of the Tornquist margin of Laurussia with a volcanic arc (here: the Teisseyre Arc) – located probably at the easternmost extent of the Avalonian Plate. In this scenario, the arc-continent orogen was composed of an uplifted filling of the forearc basin, an accretionary prism, volcanic arc rocks, and an exhumed foreland basement - analogously to the present-day Taiwan orogen. The second key issue is the palaeogeographical relation between the Małopolska (Kielce Region) and the Łysogóry terranes in the Late Silurian. Despite the analogous grain composition and clast types, the Łysogóry Region greywackes are composed of distinctly more altered detritus, which is in accordance with the more distal character of the Łysogóry Basin. The latter is manifested, e.g., in the lack of Caledonian deformations. The present-day adjacency of both domains containing correlative greywacke formations coupled with contrasting alteration and Late Silurian transport directions parallel to the terrane boundary imply small to medium-scale (below palaeomagnetic resolution) left-lateral movements of the Małopolska and Łysogóry crustal blocks along the Holy Cross Fault in post-Silurian times.

Trace fossils in the Cretaceous-Eocene flysch of the Sinop-Boyabat Basin, Central Pontides, Turkey

Uchman A., Janbu N. E., Nemec W.

Annales Societatis Geologorum Poloniae

2004

Vol. 74, No 2

197--235

Sixty six ichnotaxa have been recognized in Barremian-Lutetian deep-marine deposits of the Sinop- Boyabat Basin, north-central Turkey, which evolved from a backarc rift into a retroarc foreland, with two episodes of major shallowing. The blackish-grey shales of the Çađlayan Fm (Barremian-Cenomanian) contain low- diversity traces fossils of mobile sediment feeders influenced by low oxygenation. One of the oldest occurrences of Scolicia indicates early adaptation to burrowing in organic-rich mud. The "normal" flysch of the Coniacian- Campanian Yemişliçay Fm bears a low-diversity Nereites ichnofacies influenced by volcanic activity. The Maastrichtian-Late Palaeocene carbonate flysch of the Akveren Fm contains a Nereites ichnofacies of moderate diversity, which is impoverished in the uppermost part, where tempestites indicate marked shallowing. The overlying variegated muddy flysch of the Atbaşý Fm (latest Palaeocene-earliest Eocene) bears an impoverished Nereites ichnofacies, which is attributed to oligotrophy and reduced preservation potential. The sand-rich silici-clastic flysch of the Kusuri Fm (Early-Middle Eocene) bears a high-diversity Nereites ichnofacies, except for the topmost part, where tempestites and littoral bioclastic limestone reflect rapid shallowing due to the tectonic closure of the basin. The turbiditic channel-fill and proximal lobe facies show a reduced trace-fossil diversity, but abundant Ophiomorpha , which is typical of the Ophiomorpha rudis sub-ichnofacies of the Nereites ichnofacies. The high abundance of Ophiomorpha in the Kusuri Fm and its low abundance in the Akveren Fm are related to plant detritus supply. The Kusuri turbiditic system was fed by a large delta, supplying rich plant detritus, whereas the Akveren system was fed by a carbonate ramp that supplied little or no such material. The extension of the Nereites ichnofacies into the tempestite-bearing neritic deposits at the top of both the Akveren and Kusuri formations indicates the capacity of the deep-water ichnofauna to survive in a rapidly-shoaling restricted basin. Only the topmost shoreface sandstones of the Akveren Fm show sporadic Ophiomorpha ? nodosa, a typical shallow-marine trace fossil.