[en] The age of the emplacement of the Ronda Peridotites has been widely debated during recent decades, and ages ranging from the Palaeozoic to the early Miocene have been proposed, although most of the current interpretations suggest an Oligocene-Miocene age. In this article, we describe two meta-sedimentary formations (the lower one formed by detrital sediments and the upper one by marbles) that were unconformably deposited over the Ronda peridotites and now record low-grade metamorphism. The detrital formation contains layers of acidic rocks with an age of 269±9 Ma and the overlying marbles are assumed to be Triassic. The existence of these unconformable formations over the peridotites is crucial for the dating of the exhumation of the latter. The presence of peridotite clasts in the detrital formation indicates that peridotites were exposed during the Permian and other data suggest that peridotites were exhumed during the late Carboniferous. During the Alpine cycle, the peridotites operated as an element situated at the bottom of the tectonically higher Alpujarride/Sebtide unit (the Jubrique unit) and forming part of it, then being incorporated to the Alpine thrusts of this unit. (Author)

[en] Complete text of publication follows. Magnetic susceptibility (MS) records from Holocene, Pleistocene and Tertiary sedimentary successions have been widely used as palaeoclimatic proxies. The use of MS in Palaeozoic sediments is becoming more common but still suffers from some controversy. One of the problems is the origin of the magnetic minerals. Most sedimentologists accept the hypothesis that magnetic minerals reflect lithogenic inputs. However, it remains unclear if these inputs are of fluvial or of aeolian nature and if they are influenced by climatic, sea-level or tectonic changes, which act probably at different time-scales. In order to differentiate between different impacts, a strong interdisciplinary characterisation of facies, cyclostratigraphy and the MS signal and MS carriers is required. Furthermore, concerning of Palaeozoic rocks, the influence of diagenesis on the magnetic mineralogy has to be assessed. We would like to promote the interdisciplinary IGCP-project 850, recently funded by the UNESCO, in order to invite collaborators to possibly join our research. The project aims at compiling published magnetic susceptibility records from Palaeozoic sedimentary rocks and at acquiring new data for testing the correlation between susceptibility and sedimentological parameters. Another goal is to investigate the cause of the magnetic susceptibility signal in different sedimentary environments and its relationship to climate controlled environmental parameters. Finally, magnetic susceptibility records from different globally distributed sites will be correlated for reconstructions of past climatic variations.

[en] We have analysed the diversity of the late Paleozoic palynoflora of the Paraná (Brazil and Uruguay), Parnaíba and Amazon (Brazil) basins using already published data. In order to do this the total diversity and diversity with range-through approach curves were built up, as well as Foote’s appearance and disappearance rates at the generic level. These parameters were also obtained separately for each group of sporomorphs. An important increase in diversity in the Asselian and Sakmarian and a posterior decrease until the Lopingian were observed. The values of the appearance rates were higher than those of disappearance and they peaked in the Asselian, while the highest disappearances took place in the Capitanian and, to a lesser extent, in the Sakmarian. On the other hand, spores and pollen grains show some differences in the general diversity trend. However, there are differences in the patterns of appearance and disappearance. Despite possible biases, mainly related to the collecting effort, the diversity curves and appearance and disappearance rates obtained are congruent with the climatic phases proposed for this region in these periods. The increase in the number of palynomorph genera is associated to the early Permian climatic amelioration whilst a decrease in diversity is related to the beginning of an arid phase.

[en] Experimental results of coral dating and paleo-environment studies by using the thermal ionization spectrometry (TIMS) uranium series method were introduced. The TIMS result for BKM-4 standard coral measured by the MAT-262 MS instrument is consistent with that by α spectrometry method

[en] The marble of the Samaná complex presents a widespread foliation formed during its exhumation following a general decompressive strain path from high pressure (2.0>P>0.7 GPa) and low temperature (<500 ºC) conditions. The foliation is plano-linear and blastomylonitic. Deformation distribution is highly heterogeneous. Calcite preferred orientation is poor, even though the marble has a well-defined tectonic fabric. The blastomylonitic fabric is masking an earlier tectonic fabric. Cathodoluminiscence images reveal that intense fracturing formed prior to foliation development in the marbles. The thermodynamic modelling of mineral phase transformations during prograde metamorphism indicate an increase in water content (1.2%< w.t. H2O<1.8%) that may have involved an increase in fluid pressure and triggered rock embrittlement and subsequent exhumation. Stress drops after a cataclastic event, as well as grain-size reduction by abrasion, may have activated dissolution-precipitation processes along cataclastic bands. Differential stress |s1-s3| increased as exhumation progressed after the cataclastic event. Estimates of paleostress based on calcite mechanical twinning indicate values of |s1-s3| >350 MPa during deformation. In contrast, mean flow stress during grain-boundary migration is estimated in |s1-s3| <150 MPa. The high paleostress record and microstructures of the marble are consistent with the high exhumation rate calculated (>110 MPa Ma-1). All of these data suggest that exhumation always occurred near the brittle-ductile regime of deformation.

[en] Short communication

[en] Complete text of publication follows. Magnetostratigraphic data series (ChRM and bulk magnetic susceptibility) from two Late Paleozoic glacial rhythmite successions from the Itarare Subgroup (Parana Basin, southern Brazil) were examined by means of spectral analysis for paleoclimate variations recorded by sedimentation. Astronomical calibration through orbital spectral peak ratios predicted for Permian times leads to recognition of variations with millennial-scale quasi-periodicities, reminiscent of abrupt climate changes during Late Quaternary times, and suggestive of Dansgaard-Oeschger and Heinrich events (Bond cycles) and the ∼2.4-kyr solar cycle. This remarkable evidence could indicate a prevalence of these harmonic features in the atmosphere-ocean system that is not restricted to the Quaternary Period, and would help to advance discussions about forcing mechanisms that are a common source for large climatic changes throughout geological time.

[en] Full text :The study of geotectonic modes of organic zones has important meaning for specifying of Earths' deep structures. The present work is dedicated to research of Paleozoic geotectonic modes of Mediterranean Sea zone by character of regional gravity anomalies of Caspian Sea and Azerbaijan. There are three typical maximums in Buggier reduction for gravity field in researching region: Mughan-Garabaghs (onshore); South-Caspian and Middle-Caspian (offshore). Mughan-Garabaghs and South-Caspian maximums are represented by low intensity and sizes and are not interconnected. Mughan-Karabagh maximum is expressed in oval-shaped form, and its impossible to judge about its spreading direction, but South-Caspian maximum has dominant spreading in NW-SE direction. The geological nature of South Caspian maximum was associated with tectonics of folded surface of crystalline basement by previous researches, but revealing of Mesozoic complex on 12-14 km depth by seismic method of survey showed that the nature of this maximum is associated with deep-buried intrusive inculcation. The Middle-Caspian maximum is associated with Turan plate-Epi-Hurricane platform, and this is beyond doubt for specialists. Analyzing above mentioned comparison features of these regional anomalies, we suppose that they arose just in connection with change of geotectonic modes in Paleozoic Age

[en] Cambrian–Devonian sedimentary rocks of the northern Canadian Cordillera record both the establishment and demise of the Great American Carbonate Bank, a widespread carbonate platform system that fringed the ancestral continental margins of North America (Laurentia). Here, we present a new examination of the deep-water Road River Group of the Richardson Mountains, Yukon, Canada, which was deposited in an intra-platformal embayment or seaway within the Great American Carbonate Bank called the Richardson trough. Eleven detailed stratigraphic sections through the Road River Group along the upper canyon of the Peel River are compiled and integrated with geological mapping, facies analysis, carbonate and organic carbon isotope chemostratigraphy, and new biostratigraphic results to formalize four new formations within the type area of the Richardson Mountains (Cronin, Mount Hare, Tetlit, and Vittrekwa). We recognize nine mixed carbonate and siliciclastic deep-water facies associations in the Road River Group and propose these strata were deposited in basin-floor to slope environments. New biostratigraphic data suggest the Road River Group spans the late Cambrian (Furongian) – Middle Devonian (Eifelian), and new chemostratigraphic data record multiple global carbon isotopic events, including the late Cambrian Steptoean positive carbon isotope excursion, the Late Ordovician Guttenberg excursion, the Silurian Aeronian, Valgu, Mulde (mid-Homerian), Ireviken (early Sheinwoodian), and Lau excursions, and the Early Devonian Klonk excursion. Together, these new data not only help clarify nomenclatural debate centered around the Road River Group, but also provide critical new sedimentological, biostratigraphic, and isotopic data for these widely distributed rocks of the northern Canadian Cordillera. (author)

[en] The main features of geological structure and history of forming Mesozoic and Cenozoic structure and formations complexes are given. Forming of Mesozoic-Cenozoic Depressive structures had been going on under the condition of infiltrations regime of artesian basins with forming of regional ground and stratum oxidation zones in Zhalpak and Paleogenic sediments which are including uranium deposits belonging to four uranium ore formation. The main raw materials base and extraction of uranium by in-situ leaching method are connected with deposits of epigenetic uranium-ore formation of regional stratum oxidation zones. There are most important deposits: Maikuduk, Inkai, Zhalpak, Uvanas, Suluchekenskoe, Koldzatskoe, Nizhneilyiskoe. All deposits are described according to same plan: stratigraphy, tectonic structure, hydrogeology, hydrochemics, uranium mineralization, morphology of deposits, mineral compound of ores, geologic characteristics of ores, genetics. Except uranium, the main deposit component, there is an information about the accompanied elements: rhenium, selenium, rare-earth ones, industrial concentration of which are in competitions with the same elements extracted from ores