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2 Annales Societatis Geologorum Poloniae

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Lacustrine trace fossils and environmental conditions in the Early Miocene Ermenek Basin, southern Turkey

Uchman A., Nemec W., Ilgar A., Messina C.

Annales Societatis Geologorum Poloniae

2007

Vol. 77, No 2

123-139

The Early Miocene lacustrine succession of the Ermenek Basin, an intramontane graben in southern Anatolia, consists of hemipelagic, variably calcareous mudstones and pelagic marlstones densely interspersed with tempestite sandstone sheets, subordinate turbidite sandstone sheets and sporadic layers of evaporitic limestone. The marly lake was hydrologically closed and mainly no deeper than 10 m, with the mean fairweather wave base at 1.5 m and storm wave base around 5 m. The deposits abound in trace fossils, including Vagorichnus cf. anyao (its second recognized occurrence), endichnial ferruginous ribbons, large tubular structures, oblique cylinders, small discontinuous ridges, undulating ridges, planar wall structures and a range of other bioturbational features. The tempestites and turbidites show both pre-and post-event trace fossils, with recognizable mixed and transitional layers similar as reported from marine tempestites and turbidites. The trace fossils constitute an impoverished Mermia ichnofacies indicating a considerable environmental stress. The lake salinity fluctuated, and the stress factor is attributed to the extreme environmental conditions (increased salinity and unusual water chemistry) caused by episodes of brackishness due to decreases in rainfall and increases in evaporation. Freshwater conditions are indicated by benthic ostracods and mollusc shells in offshore mudstones and by gastropod shells in coastal coal deposits, whereas marly layers contain only the ostracod species Miocyprideis glabra asulcata, implying mesohaline to polyhaline conditions.

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.