Huriye Demircan

A zoophycos group trace fossil from miocene flysch in Southern Turkey: Evidence for a U‐shaped causative burrow

Echinospira isp., a relatively small, lobate, trace fossil of the Zoophycos group, occurs in Miocene flysch deposits of the Cingoz Formation of southern Turkey. It displays a burrow system which contains U‐shaped Rhizocorallium‐like elements. The burrow system resulted from successive lateral shifts of a causative U‐shaped burrow, which reworked most of the previously formed ones. More and less systematic patterns of sediment reworking by the trace fossil producer were observed. The trace fossil occurs in a low diversity ichnoassemblage related to environmental stress conditions probably caused by frequent turbiditic deposition and lithological changes. In comparison, Echinospira pauciradiata occuring in pelagic sediments of the same age is much larger and displays a more regular pattern, related to more stable environmental conditions.

Chronology of subduction and collision along the İzmir-Ankara suture in Western Anatolia: records from the Central Sakarya Basin

ABSTRACT Western Anatolia is a complex assemblage of terranes, including the Sakarya Terrane and the Tauride-Anatolide Platform that collided during the late Cretaceous and Palaeogene (80–25 Ma) after the closure of the Izmir-Ankara Ocean. Determining the precise timing at which this ocean closed is particularly important to test kinematic reconstructions and geodynamic models of the Mediterranean region, and the chronology of suturing and its mechanisms remain controversial. Here, we document the Cretaceous-Eocene sedimentary history of the Central Sakarya Basin, along the northern margin of the Neotethys Ocean, via various approaches including biostratigraphy, geochronology, and sedimentology. Two high-resolution sections from the Central Sakarya Basin show that pelagic carbonate sedimentation shifted to rapid siliciclastic deposition in the early Campanian (~ 79.6 Ma), interpreted to be a result of the build-up of the accretionary prism at the southern margin of the Sakarya Terrane. Rapid onset of deltaic progradation and an increase in accumulation rates in the late Danian (~ 61 Ma), as well as a local angular unconformity are attributed to the onset of collision between the Sakarya Terrane and the Tauride-Anatolide Platform. Thus, our results indicate that though deformation of the subduction margin in Western Anatolia started as early as the Campanian, the closure of the İzmir-Ankara Ocean was only achieved by the early Palaeocene.

Ichnology of prodelta deposits of the Mezardere Formation (late Eocene – early Oligocene) in the Gökçeada Island, western Turkey

On Gökçeada Island, the Mezardere Formation is dominated by the prodelta facies composed mostly of light grey, thinly bedded, fissile calcareous mudstones and siltstones, which mostly display parallel lamination or rarely ripple lamination. These sediments are intercalated with isolated thin beds of very fine- or fine-grained slightly muscovitic sandstones, which display parallel lamination in the lower part and ripple lamination in the upper part, or only ripple lamination. Thicker sandstone beds, referred to as mouth bars, are present in places. The prodelta sediments are poorly bioturbated (ii = 0–1), but moderately diverse trace fossils occur on some bedding surfaces, including 22 ichnotaxa referred to 13 ichnogenera and three trace fossils left in open nomenclature. The impoverished trace fossil assemblages are typical of deltaic sediments, but paucity of the trace fossils and poor bioturbation of the prodelta sediments in the Mezardere Formation is striking. The typically marine ichnoataxa are rare or absent in most outcrops. This trace fossil assemblage, resembling the Mermia ichnofacies, suggests a strong brackishness of the palaeoenvironment; however, the occurrence of Bichordites kuzunensis in one outcrop suggests local and temporal normal marine conditions referred to as salinity fluctuations.