Early Bartonian orthophragminids (Foraminiferida) from Reineche Limestone,north African platform,Tunisia: taxonomy and paleobiogeographic implications

The orthophragminids in lower Bartonian Reineche Limestone member, a fossiliferous shallow-marine unit exposed in Cap Bon peninsula in Tunisia, are represented by 17 species assigned to Discocyclinidae Galloway 1928 and Orbitoclypeidae Brönnimann 1946. These taxa, associated with nummulitids and alveolinids, belong to the lineages of Discocyclina Gümbel 1870, Nemkovella, 1987, Orbitoclypeus Silvestri 1907, and Asterocyclina Gümbel 1870, described for the first time from north Africa lying at the southern margin of Tethyan ocean during Paleogene. We identified Nemkovella evae, previously not recorded in upper Lutetian/lower Bartonian and younger Eocene deposits of northern Tethyan platforms, and erected a new subspecies, N. evae reinechensis n. ssp. A comparison of Reineche orthophraminids, assigned to orthophragmines zone (OZ) 12 and shallow benthic zone (SBZ 17), to the well-described coeval assemblages at northern Tethyan platforms in Italy, Hungary, Turkey, and to those in Kutch Basin in the Indian subcontinent suggests that some species are confined to certain paleogeographic domains. Orbitoclypeus haynesi, the only orbitoclypeid and the most abundant orthophragminid in lower Bartonian deposits in Kutch, appears to be the most common orbitoclypeid in Reineche Limestone. In Europe, this species is not known and is replaced by Orbitoclypeus varians, the most common orbitoclypeid in middle Eocene of central Europe. Both species occur in varying proportions in marine successions in Turkey. Asterocyclina sireli, identified so far only in Turkey, occurs in Reineche Limestone and in lower Bartonian deposits in Kutch. This species is recorded for the first time in the Indian subcontinent. Relying on present study, as well as our recent studies in Kutch Basin, we conclude that the generic and specific diversity of orthophragminids decreases eastward from the peri-Mediterranean region to Indian subcontinent and to the western Pacific.     

From Tethys to Eastern Paratethys: Oligocene depositional environments, paleoecology and paleobiogeography of the Thrace Basin (NW Turkey)

The Oligocene depositional history of the Thrace Basin documents a unique paleogeographic position at a junction between the Western Tethys and the Eastern Paratethys. As part of the Tethys, shallow marine carbonate platforms prevailed during the Eocene. Subsequently, a three-staged process of isolation started with the Oligocene. During the Early Rupelian, the Thrace Basin was still part of the Western Tethys, indicated by typical Western Tethyan marine assemblages. The isolation from the Tethys during the Early Oligocene is reflected by oolite formation and endemic Eastern Paratethyan faunas of the Solenovian stage. The third phase reflects an increasing continentalisation of the Thrace Basin with widespread coastal swamps during the Late Solenovian. The mollusc assemblages are predominated by mangrove dwelling taxa and the mangrove plant Avicennia is recorded in the pollen spectra. The final continentalisation is indicated by the replacement of the coastal swamps by pure freshwater swamps and fluvial plains during the Late Oligocene (mammal zone MP 26). This paleogeographic affiliation of the Thrace Basin with the Eastern Paratethys after ~32 Ma contrasts all currently used reconstructions which treat the basin as embayment of the Eastern Mediterranean basin.     

A different method for interpretation of magnetic anomalies due to 2-D dipping dikes

In this study a new method is presented to determine model parameters from magnetic anomalies caused by dipping dikes. The proposed method is applied by employing only the even component of the anomaly. First, the maximum of the even component is divided to its value at any distance x in order to obtain S1. Then, theoretical even component values are computed for the minimal depth (h) and half-width (b) values. S2 is obtained by dividing their maximum to the value computed for the same distance x. A set of S2 values is calculated by slowly increasing the half-width, and h and b for the S2 closest to S1 are determined. The same procedure is repeated by increasing the depth. The determined b values are plotted against the corresponding values of h. After repeating the process and plotting curves for different distances, it is possible to determine the actual depth and half-width values.     

Multi-disciplinary earthquake researches in Western Turkey: Hints to select sites to study geochemical transients associated to seismicity

Warm and hot spring water as well as soil gas radon release patterns have been monitored in the Aegean Extensional Province of Western Turkey, alongside regional seismic events, providing a multi-disciplinary approach. In the study period of 20 months, seven moderate earthquakes with M _L between 4.0 and 4.7 occurred in this seismically very active region; two earthquakes with magnitude 5.0 also occurred near the study area. Seismic monitoring showed no foreshock activity. By contrast, hydro-geochemical anomalies were found prior to these seismic events, each lasting for weeks. The anomalies occurred foremost in conjunction with dip-slip events and seem to support the dilatancy and water diffusion hypothesis. Increased soil gas radon release was recorded before earthquakes associated with strike-slip faults, but no soil radon anomalies were seen before earthquakes associated with dip-slip faults. Geochemical anomalies were also noticeably absent at some springs throughout the postulated deformation zones of impending earthquakes. The reason for this discrepancy might be due to stress/strain anisotropies.     

The South Marmara Fault

We use about 800 km of multichannel exploration seismic reflection profiles of the seventies as well as the results of three drill holes that penetrated the sedimentary cover down to the Upper Cretaceous basement to describe a continuous gently curvilinear, south-concave zone of deformation about 10 km wide that extended over the whole southern shelf of the Sea of Marmara from the Gulf of Gemlik to the Dardanelles Straits in Lower Pliocene time, about 4 Ma. We call this zone of deformation the South Marmara Fault (SMF) system and propose that the SMF was then a branch of the dextral North Anatolian Fault. This branch passed to the north of the Marmara Island Eocene block and thus had a south-facing concavity. This curvature resulted in a significant component of shortening in the western part of the fault. The SMF was deactivated at the end of Lower Pliocene, about 3.5 Ma, except for its easternmost branch between the Gulf of Gemlik and ?mral? Island where about 5 mm/year of dextral motion is still occurring today.     

Major and trace element geochemistry of the Bigadi? Borate deposit, Balikesir, Turkiye

This study investigates the major and trace element geochemistry of Bigadi borate deposits, the largest colemanite and ulexite deposits in the world. The known borate deposits of Turkiye were deposited in the lacustrine environment during Miocene when the volcanic activity occurred from Tertiary to Quaternary. All of the Turkish borate deposits are classified as volcanic related deposits. Boron ore deposits intercalated with claystone, mudstone, tufa and fine layered limestone show lens shape. Borate minerals formed in two zones. Tiilu and Acep-Simav open mines represented the lower and upper borate zones, respectively. Colemanite and ulexite are dominant minerals at all ore zones. The major elements of Bigadi borates contain Ca, Si, Mg, Al, Fe, S, Na, P and Mn at Tiilu, Ca, Na, Si, Mg, S, Al, P and Mn at Simav, and Ca, Na, Si, Mg, S, AI and Mn at Acep samples respectively. Except for Li, Mo, Sb, As, Sr and Se, concentrations of other trace elements are significantly lower than averages of earth crust and andesite at the three mines. With respect to averages of earth crust and andesite, Mo, Sr, As, Li and particularly Se are enriched significantly in the Bigadi. In examining depth-dependent variations of major and trace elements, four element groups at the Tiilu site and six element groups at the Simav and Acep sites were determined. Element abudances or element geochemical trends show differences at the Tülü, Simav and Acep mines. These differences can be explained by the diversity of physicochemical conditions in the deposition environment by the effect of differences at the recharge regime and source.     

Light curve variations in ER vulpeculae

Photoelectric observations of the peculiar eclipsing variable ER Vul were obtained in blue and yellow light, in the 1981 and 1982 observing seasons. The light curves suffer to change in short time-intervals. The wave-like distortion superimposed on the light curves is clearly seen, but sometimes there is no indication about its existence. The migration period has been estimated roughtly about eight months. Moreover, small-amplitude light fluctuations in the light curves are noticeable. These variations seem to be occur randomly. When the IUE and optical observations are taken into consideration together it is strongly suggested that both of the components in the system ER Vul are too active.     

Mapping multi‐year ground water salinity patterns in irrigation areas using time‐series analysis of ground water salinity maps

In irrigation areas, ground water salinity (GWS) levels may vary depending on the amount and quality of irrigation water applied and on the activity of the drainage system. GWS plays a vital role in irrigation systems by influencing whether the environment is suitable for plant growth. Hence, it is necessary to monitor changes in GWS both temporally and spatially. Maps are generally used to visualize this information. However, evaluation of temporal and spatial variations of GWS can be difficult because of the necessity of assessing many maps together to understand both temporal and spatial changes. In this study, a data assessment method that can be used for multi‐year ground water salinity evaluations is presented. The method looks at the spatial and temporal relationships between the main salinity classes present in the study area, their typical locations (i.e. areas where the salinity classes are most frequently located), and the alternate salinity classes in those locations in any of the years of the time series. As a case study, the method was applied to multi‐year (1990–2000) GWS observations in the Mustafakemalpasa irrigation project (19 370 ha) in the Marmara region of north‐western Turkey. Copyright © 2007 John Wiley & Sons, Ltd.