Is Evolution of Blind Mole Rats Determined by Climate Oscillations?

The concept of climate variability facilitating adaptive radiation supported by the ‘‘Court Jester’’ hypothesis is disputed by the ‘‘Red Queen’’ one, but the prevalence of one or the other might be scale-dependent. We report on a detailed, comprehensive phylo-geographic study on the ,4 kb mtDNA sequence in underground blind mole rats of the family Spalacidae (or subfamily Spalacinae) from the East Mediterranean steppes. Our study aimed at testing the presence of periodicities in branching patterns on a constructed phylogenetic tree and at searching for congruence between branching events, tectonic history and paleoclimates. In contrast to the strong support for the majority of the branching events on the tree, the absence of support in a few instances indicates that network-like evolution could exist in spalacids. In our tree, robust support was given, in concordance with paleontological data, for the separation of spalacids from muroid rodents during the first half of the Miocene when open, grass-dominated habitats were established. Marine barriers formed between Anatolia and the Balkans could have facilitated the separation of the lineage ‘‘Spalax’’ from the lineage ‘‘Nannospalax’’ and of the clade ‘‘leucodon’’ from the clade ‘‘xanthodon’’. The separation of the clade ‘‘ehrenbergi’’ occurred during the late stages of the tectonically induced uplift of the Anatolian high plateaus and mountains, whereas the separation of the clade ‘‘vasvarii’’ took place when the rapidly uplifting Taurus mountain range prevented the Mediterranean rainfalls from reaching the Central Anatolian Plateau. The separation of Spalax antiquus and S. graecus occurred when the southeastern Carpathians were uplifted. Despite the role played by tectonic events, branching events that show periodicity corresponding to 400-kyr and 100-kyr eccentricity bands illuminate the important role of orbital fluctuations on adaptive radiation in spalacids. At the given scale, our results supports the ‘‘Court Jester’’ hypothesis over the ‘‘Red Queen’’ one

An experimental study of liquid compositions in equilibrium with plagioclase + spinel lherzolite at low pressures (0.75 GPa)

Models of formation of basaltic crust at mid-ocean ridges by adiabatic upwelling of fertile mantle lherzolite require knowledge of phase relations and phase compositions during melting at appropriate pressures. Spinelþplagioclase lherzolites are found among peridotite samples from the ocean floor and ophiolitic exposures. At low pressure (51·2 GPa) the five-phase assemblage (olivineþorthopyroxeneþclinopyroxeneþplagioclaseþspinel) is present at the anhydrous lherzolite solidus. New experimental data on mineral and melt compositions, at 0·75 GPa and 1140^12608C in the (CrþNaþFeþCaþMgþAlþSi) system, demonstrate smooth covariant relationships between oxides for melt compositions and in partition relationships both between mineral pairs and between minerals and melts. Molecular normative projections demonstrate that liquids on the five-phaseþliquid cotectic occupy a narrow compositional range. Of the mineral solid solutions that control the liquid composition, the [Ca/(CaþNa)] or anorthite/ albite content of the plagioclase is dominant and liquids vary from silica undersaturated and nepheline-normative at the sodic (oligoclase) end to orthopyroxene and quartz-normative at the calcic (anorthite) end of the cotectic. Spinel (Cr^Al) solid solution has limited variation on the five-phaseþliquid cotectic. It is very Cr-rich at the sodic end and has limited compositional variation from50 to 20 in Cr/(CrþAl) at the anorthitic end.With fixed plagioclase composition on the cotectic, melt compositions show small compositional shifts with Fe^Mg (at Mg# between 85 and 95) and with Cr/(CrþAl). The compositional vectors are consistent with effects observed in the end-member simple systems (FCMAS) and (CrCMAS). In comparing liquids at the anorthite end of the five-phaseþliquid cotectic with those on the Cr-free CMAS four-phaseþliquid cotectic at 0·75 GPa, it is evident that the presence of Al-rich Cr^Al spinel shifts liquid compositions to more silica-rich and silica-oversaturated composition.These experimentally defined melt compositions in equilibrium with plagioclaseþspinel lherzolite are unlike quenched glasses from mid-ocean ridge settings.The data do not support models of mantle upwelling at low potential temperature (12808C) that produces low melt fractions at low pressures, leaving residual plagioclaseþspinel lherzolite. The detailed mineral compositional data at the solidus provide a template for comparison with natural plagioclaseþspinel lherzolites refertilized by porous reactive flow

40Ar/39Ar Dating of magmatic activities in the Donbas Foldbelt and the Scythian Platform (Eastern Europe).

The Donbas Fold Belt is the compressionally deformed southeasternmost part of the intracratonic late Paleozoic Dniepr-Donets rift basin. It is situated in an intracratonic setting but close to the southern margin of the East European Craton, south of which lies the Scythian Platform. A range of igneous rocks from the Donbas Fold Belt and the Scythian Platform were dated by th

The Mesozoic-Cenozoic tectonic evolution of the Greater Caucasus

The Greater Caucasus (GC) fold-and-thrust belt lies on the southern deformed edge of the Scythian Platform (SP) and results from the Cenoozoic structural inversion of a deep marine Mesozoic basin in response to the northward displacement of the Transcaucasus (lying south of the GC subsequent to the Arabia-Eurasia collision. A review of existing and newly acquired data has allowed a reconstruction of the GC history through the Mesozoic and Cenozoic eras. In Permo(?)-Triassic times, rifting developed along at least the northern part of the belt. Structural inversion of the basin occurred during the Late Triassic corresponding to the Eo-Cimmerian orogeny, documented SE of the GC and probably linked to the accretion of what are now Iranian terranes along the continental margin. Renewed development of extensional basin formation in the area of the present-day GC began in Sinemurian-Pliensbachian times with rift activity encompassing the Mid-Jurassic. Rifting led to extreme thinning of the underlying continental crust by the Aalenian and concomitant extrusion of mid-ocean ridge basalt lavas. A Bathonian unconformity is observed on both sides of the basin and may either correspond to the end of active rifting and the onset of post-rift basin development or be the record of collision further south along the former Mesozoic active margin. The post-rift phase began with deposition of Late Jurassic platform-type sediments onto the margins and a flysch-like unit in its deeper part, which has transgressed the basin during the Cretaceous and Early Cenozoic. An initial phase of shortening occurred in the Late Eocene under a NE-SW compressional stress regime. A second shortening event that began in the Mid-Miocene (Sarmatian), accompanied by significant uplift of the belt, continues at present. It is related to the final collision of Arabia with Eurasia and led to the development of the present-day south-vergent GC fold-and-thrust belt. Some north-vergent retrothrusts are present in the western GC and a few more in the eastern GC, where a fan-shaped belt can be observed. The mechanisms responsible for the large-scale structure of the belt remain a matter of debate because the deep crustal structure of the GC is not well known. Some (mainly Russian) geoscientists have argued that the GC is an inverted basin squeezed between deep (near)-vertical faults representing the boundaries between the GC and the SP to the north and the GC and the Transcaucasus to the south. Another model, supported in part by the distribution of earthquake hypocentres, proposes the existence of south-vergent thrusts flattening at depth, along which the Transcaucasus plunges beneath the GC and the SP. In this model, a thick-skinned mode of deformation prevailed in the central part of the GC whereas the western and eastern parts display the attributes of thin-skinned fold-and-thrust belts, although, in general, the two styles of deformation coexist along the belt. The present-day high elevation observed only in the central part of the belt would have resulted from the delamination of a lithospheric root