Sacit Özer

A synoptical classification of the Bivalvia (Mollusca)

Preface This classification summarizes the suprageneric taxonomy of the Bivalvia for the upcoming revision of the Bivalvia volumes of the Treatise on Invertebrate Paleontology, Part N.

Rudist bearing Upper Cretaceousmetamorphic sequences of the Menderes Massif (Western Turkey)

The Menderes Metamorphic Massif is located between the Izmir-Ankara zone to the north, and theLycianinappes and Bey Daglari platform to the south in the western part of Turkey. The massif consists of core rocks of Precambrian to Cambrian gneisses, schists, metagranites, and cover rocks of Paleozoic micaschists and marbles, Mesozoic thick bedded platform-type metacarbonates, and Lower Tertiary pelagic metacarbonates and flysch type rocks. Rudists were discovered locally from the southern sector of the Menderes Massif, around Milas area, and they were accepted as a very important paleontologic data indicating however only a Late Cretaceous age in the previous studies. The presence of several new localities showing a wide geographic distribution of the rudists in the southern and nerthern sectors of the massif is revealed, and presented in this study. The rudist-bearing metamorphic sequences are mainlyrepresented by platform-type carbonates. However, sequences consistin of clastics and carbonates are also present. The Upper Cretaceous metamorphic sequences consist of, from base to top, emery-bearing marbles and marbles with rudists (Cenomanian), rudist-bearing marbles (Santonian-Campanian), and red-pinkish pelagic marbles (late Campanian-Maastrichtian). Flysch type rocks (Early Tertiary) overlie these sequences. Two rudist associations allowing precisely to establish the Upper Cretaceous stratigraphy in the massif are distinguished. The first association is characterized by the abundance of rudists with canals such as Neocaprina gigantea, Caprina schiosensis, Schiosia cf. schiosensis, Sphaerucaprina cf. forojuliensis, Ichthyosarcolites poljaki, Ichthyosarcolites rotundus, Ichthyosarcolites bicarinatus, Ichthyosarcolites cf. tricarinatus indicating a middle-late Cenomanian age. This association also consists of Eoradiolites cf. liratus, Durania sp., Apricardia sp., Chondrodonta sp., and Distefanella close to Distefanella bassani and Distefanella cf. montagnei which are found for the first time in Turkey. The second association is represented mainly by hippuritids: and radiolitids such as Vaccinites taburni, Vaccinites cf. sulcatus, Hippurites nabresinensis Hippurites colliciatus, Sauvagesia cf. tenuicostata, and Durania sp., indicating a Santonian-Campanian age.

Miocene transgression in the central and eastern parts of the Sivas Basin (Central Anatolia, Turkey) and the Cenozoic palaeogeographical evolution

We present here a reappraisal of the tectonic setting, stratigraphy and palaeogeography of the central part of the Sivas Basin from Palaeocene to late Miocene. The Sivas Basin is located in the collision zone between the Pontides (southern Eurasia) and Anatolia (a continental block rifted from Gondwana). The basin overlies ophiolites that were obducted onto Anatolia from Tethys to the north. The Central Anatolian Crystalline Complex (CACC) experienced similar ophiolite obduction during Campanian time, followed by exhumation and thrusting onto previously emplaced units during Maastrichtian time. To the east, crustal extension related to exhumation of the CACC created grabens during the early Tertiary, including the Sivas Basin. The Sivas Basin underwent several tectonic events during Paleogene–Neogene. The basin fill varies, with several sub-basins, each being characterised by a distinctive sequence, especially during Oligocene and Miocene. Evaporite deposition in the central part of the basin during early Oligocene was followed by mid-late Oligocene fluvio-lacustrine deposition. The weight of overlying fluvial sediments triggered salt tectonics and salt diapir formation. Lacustrine layers that are interbedded within the fluviatile sediments have locally yielded charophytes of late Oligocene age. Emergent areas including the pre-existing Sivas Basin and neighbouring areas were then flooded from the east by a shallow sea, giving rise to a range of open-marine sub-basins, coralgal reef barriers and subsiding, restricted-marine sub-basins. Utilising new data from foraminifera, molluscs, corals and nannoplankton, the age of the marine transgression is reassessed as Aquitanian. Specifically, age-diagnostic nannoplankton assemblages of classical type occur at the base of the transgressive sequence. However, classical stratigraphic markers have not been found within the planktic foraminiferal assemblages, even in the open-marine settings. In the restricted-marine sediments, there are rich planktic foraminiferal assemblages of classical type but these are of little use in stratigraphy. In contrast, the gastropod fauna indicate a Burdigalian age. Sediment reworking in the restricted-marine environments precludes stratigraphic determination. In such environments, micro- and nano-organisms experienced atypical developmental conditions. The small benthic foraminifera and associated ostracod assemblages are good indicators of salinity which varied considerably within the restricted-marine sub-basins. Some of the corals within the coralgal reefs barriers are also dated as Aquitanian. A combination of the salt tectonics and the late Miocene north-westward-verging thrusting created the present basin complexity.

Facies Characteristics of the Cenomanian–Maastrichtian Sequence of the Beydaglari Carbonate Platform, Korkuteli Area, Western Taurides, Turkey

In the Korkuteli area of the western Taurides, Upper Cretaceous sequences consist of the neritic and hemipelagic Beydaglari Formation and the pelagic Akdag Formation. These formations show important facies variations and stratigraphic gaps. The Beydaglari Formation, ranging in age from Cenomanian to Santonian, is approximately 600 m thick, and is composed mainly of platform-type neritic carbonates. Five microfacies indicating tidal-flat, subtidal (lagoonal), reef, and forereef subenvironments are distinguished in the neritic carbonates of the formation. Benthic foraminifera and rudists are the main biological components that provide information about the environment and age of the unit. In addition, cryptalgal lamination also is recognized as an important tool in determining environment. The uppermost part of the Beydaglari Formation is composed of hemipelagic carbonates (a sixth microfacies), which were deposited under basinal conditions. The Akdag Formation consists of planktonic foraminifera-bearing pelagic carbonates, suggesting a Campanian-Maastrichtian age and deposition as a basinal facies. The formation disconformably overlies the Beydaglari Formation along an erosional surface. Eocene transgressive pelagic clayey carbonates of the Ulucak Formation unconformably overlie the Upper Cretaceous carbonate sequences. Detailed investigations have shown that, at least in the studied part of the autochthonous unit, the platform began to drown during the Santonian and that a true basinal environment persisted from the Campanian to the Maastrichtian. Two erosional phases are recorded; one occurred after the Santonian and is characterized by a prominent erosional surface, and the other is responsible for the post-Cretaceous regression.

Kinematics and U-Pb zircon ages of the sole metamorphics of the Marmaris Ophiolite, Lycian Nappes, Southwest Turkey

ABSTRACT In the eastern Mediterranean, the Lycian Nappes are found in the structurally uppermost position in the Anatolide-Tauride belt related to the closure of the Neotethys. In Western Turkey, the Marmaris Ophiolite with the metamorphic sole occupies the uppermost tectonic position in the Lycian belt. The metamorphic sole is represented by discontinuous tectonic slices composed of amphibolites, phyllites, micashists and quartzo-feldspathic micaschists. Zircons from the micashists and quartzo-feldspathic micaschists display dark cores and rims. The cores yield ages between 229 and 175 Ma, inner rims yield ages between 153 and 143 Ma and the outer rims show a concordia age of 96.7 ± 0.79 Ma. In terms of their Th/U ratios, the cores and inner rims indicate igneous origin, whereas the outer rims indicate accretion during metamorphism. By dating of these zircons, the deposition time for the protolith of micaschists and quartzo-feldspathic micaschists could be constrained as the Early Cretaceous. Present-day orientation of the kinematic data from the sole metamorphics and the uppermost part of the Karabörtlen formation clearly suggest a top-to-the NE sense of shear. By taking into account the 25º–30º anticlockwise post-emplacement rotation of Southwest Turkey, it follows that the Lycian Nappes were emplaced eastward onto the Menderes Nappes. This tectonic model disagrees with the previous tectonic models suggesting northward or southward movement of the Lycian Nappes onto Menderes Nappes.

Chemostratigraphy of the Cenomanian-Turonian shallow-water carbonate: new correlation for the rudist levels from north Sinai, Egypt

The present study aims to provide carbon-isotope curves for the Cenomanian to Turonian rudist-dominated successions in north Sinai. The high-resolution carbon-isotope curves obtained from north Sinai sections provide new insight for calibrating the age of rudists as well as for evaluating the effects of the oceanic anoxic event 2 (OAE2) on rudist communities. The primary goals are (1) to provide a high-resolution sequence stratigraphic framework for the Cenomanian-Turonian succession, (2) to use rudist and ammonite biostratigraphic data to distinguish the stratigraphic levels of the rudist species, and (3) to integrate the chemostratigraphic (δ13C) profile and the rudist levels to improve the biostratigraphy based on the rudist distributions and the carbon-isotope data. The recognition of three ammonite zones through the Cenomanian-Turonian succession was utilized to identify four temporally significant rudist levels indicative of the Lower Cenomanian, Middle Cenomanian, Upper Cenomanian, and Middle Turonian, respectively. Most of the rudists occur in the highstand deposits of medium-scale sequences. Carbon- and oxygen-isotopic analyses were carried out on both rudists and surrounding carbonate units. Based on the variations in the carbon-isotope signals, 12 chronostratigraphic segments were identified in the studied sections. The Cenomanian carbon-isotope segments (C23–C30) were obtained from the Halal Formation at Gabal Yelleg and Gabal Maaza sections, while the Turonian segments (C30–C34) were measured from the Wata Formation at Gabal Yelleg section. The carbon-isotope record from the studied sections is consistent with the trends documented in previous studies of the Tethyan realm. The Cenomanian-Turonian boundary is placed at the onset of falling carbon-isotope values (δ13C) from 2.61 to −0.25‰ in the upper part of OAE2 with the carbon-isotope segment C30 at Gabal Yelleg. The negative shift in δ13C values (C33) occurred in the Middle Turonian lowstand deposits characterizing the global sea level fall during this interval.

Stratigraphy and Microfacies of Cretaceous Limestones in the Bornova Flysch Zone (Spil Mountain, Manisa, Western Turkey)

Spil Mountain (Manisa, western Turkey) is situated in the Bornova Flysch Zone, which is bounded by the Izmir–Ankara Suture Zone (northern branch of Neo-Tethys) to the northwest and by the Menderes Massif to the southeast. The purpose of this study is to describe microfacies and microfossil assemblages of the Spil Mountain carbonate sequences. Two carbonate sequences in autochthonous and allochthonous settings are differentiated. The autochthonous sequence begins with inner-platform carbonates of Early Cretaceous age, which are represented by algal wackestone, fenestral mudstone, intraclastic packstone with Praechrysalidina infracretacea, Salpingoporella annulata, and charophyte oogonia. The platform succession is disconformably overlain by calciclastic turbidites and pelagic wackestones of Maastrichtian age, representing platform drowning, and then passes upward into siliciclastic sediments containing large limestone blocks. Allochthonous carbonate sequences range in age from the ?Cenomanian to Santonian–early Campanian, and were deposited in peritidal to outer-shelf palaeoenvironments. The lower part of the allochthonous sequence is composed of foraminiferal–intraclastic wackestones–packstones with mainly miliolids and Cuneolina pavonia. The middle part consists of peloidal wackestone/packstone with Aeolisaccus, Thaumatoporella, benthic foraminifers, and rudist shell fragments. The benthic foraminifera are represented by Pseudocyclammina sphaeroidea, Keramosphaerina tergestina, Moncharmontia apenninica/compressa, and Scandonea samnitica. In the upper part of the allochthonous sequence, pelagic wackestone with Marginotruncana and Dicarinella is alternated with foraminiferal–peloidal packstone with rudist shell fragments and microbioclastic wackestone.