Search results for "Paleozoic"
showing 10 items of 76 documents
Carboniferous granites on the northern margin of Gondwana, Anatolide-Tauride Block, Turkey - Evidence for southward subduction of Paleotethys
2016
Carboniferous metagranites with U-Pb zircon crystallization ages of 331-315 Ma crop out in the Afyon zone in the northern margin of the Anatolide-Tauride Block, which is commonly regarded as part of Gondwana during the Late Palaeozoic. They are peraluminous, calc-alkaline and are characterized by increase in Rb and Ba, decrease in Nb-Ta, and enrichment in Sr and high LILE/HFSE ratios compatible with a continental arc setting. The metagranites intrude a metasedimentary sequence of phyllite, metaquartzite and marble; both the Carboniferous metagranites and metasedimentary rocks are overlain unconformably by Lower Triassic metaconglomerates, metavolcanics and Upper Triassic to Cretaceous recry…
Late Palaeozoic to Mesozoic kinematic history of the Talas-Ferghana strike-slip Fault (Kyrgyz West Tianshan) as revealed by 40Ar/39Ar dating of syn-k…
2013
International audience; The NW-trending Talas-Ferghana Fault (TFF) in Kyrgyzstan, Central Asia, is one of the largest intracontinental strike-slip faults in the world. It extends over a distance of more than 2000 km from southern Tourghai to western Tarim and exhibits a maximum dextral offset of ∼200 km during the late Palaeozoic to present. The history of the fault provides important insights for the understanding of the evolution of southern Central Asia but remains poorly constrained due to lack of reliable geochronological data. We present new Ar-Ar ages and structural data from the Kyrgyz West Tianshan, that elucidate the kinematic history of the TFF in the Palaeozoic and Mesozoic. 40A…
Phanerozoic geological evolution of Northern and Central Africa: An overview.
2005
61 pages; International audience; The principal paleogeographic characteristics of North and Central Africa during the Paleozoic were the permanency of large exposed lands over central Africa, surrounded by northerly and northwesterly dipping pediplanes episodically flooded by epicontinental seas related to the Paleotethys Ocean. The intra-continental Congo–Zaire Basin was also a long-lived feature, as well as the Somali Basin from Late Carboniferous times, in conjunction with the development of the Karoo basins of southern Africa. This configuration, in combination with eustatic sea-level fluctuations, had a strong influence on facies distributions. Significant transgressions occurred duri…
Single zircon U–Pb ages and geochemistry of granitoid gneisses from SW Poland: evidence for an Avalonian affinity of the Brunian microcontinent
2010
AbstractSeven granitoid gneisses from the contact zone between the eastern margin of the Variscan belt and the Brunian microcontinent in SW Poland have been dated by ion-microprobe and207Pb/206Pb single zircon evaporation methods. The zircons define two age groups for the gneiss protoliths: (1) late Neoproterozoicc.576–560 Ma and (2) early Palaeozoicc.488–503 Ma granites. The granitoid gneisses belonging to the basement of the Brunian microcontinent contain abundant Mesoproterozoic to latest Palaeoproterozoic inherited material in the range of 1200–1750 Ma. The gneisses of the Variscan crustal domain lack Mesoproterozoic inherited zircon cores. Trace element geochemistry of Proterozoic gnei…
Influence of basement heterogeneity on the architecture of low subsidence rate Paleozoic intracratonic basins (Reggane, Ahnet, Mouydir and Illizi bas…
2018
The Paleozoic intracratonic North African Platform is characterized by an association of arches (ridges, domes, swells, or paleo-highs) and low subsidence rate syncline basins of different wavelengths (75–620 km). The Reggane, Ahnet, Mouydir and Illizi basins are successively delimited from east to west by the Amguid El Biod, Arak-Foum Belrem, and Azzel Matti arches. Through the analysis of new unpublished geological data (i.e., satellite images, well logs, seismic lines), the deposits associated with these arches and syncline basins exhibit thickness variations and facies changes ranging from continental to marine environments. The arches are characterized by thin amalgamated deposi…
A new ichnofauna from the Permian of the Zat Valley in the Marrakech High Atlas of Morocco
2020
Abstract A new ichnofauna from the Permian of Morocco is described in details: it is the first Palaeozoic ichnofauna from the Zat Valley in Marrakech High Atlas. The new tracksite was found in the Tighdouine region, in the middle-upper Permian of the Cham-el-Houa Siltstone Formation. An abundant and diverse ichnoassemblage composed of both protostomian (probably arthropods and annelids) traces and vertebrate tracks is recorded. The presence of protostomian burrows and traceways, associated with tetrapod tracks corresponds to the Scoyenia ichnofacies. Protostomian traces are ascribed to Diplichnites gouldi, Diplopodichnus biformis, Scoyenia cf. gracilis and Spongeliomorpha carlsbergi. Tetrap…
Was climatic cooling during the earliest Carboniferous driven by expansion of seed plants?
2021
Abstract The expansion of land plants is considered to have played a key role in triggering the Late Paleozoic Ice Age (LPIA), but evidence linking climatic events to terrestrial floral changes is limited. Here, we generated bulk carbonate δ13C, conodont δ18O and 87Sr/86Sr profiles from the lowermost Carboniferous of South China and Vietnam in order to investigate their relationship to contemporaneous land plant evolution. Climatic cooling in the mid-Tournaisian coincided with large perturbations to the global carbon cycle and continental weathering regimes as well as with a major diversification episode among seed plants. These relationships are consistent with terrestrial floral changes t…
Structural contacts in subduction complexes and their tectonic significance: the Late Palaeozoic coastal accretionary wedge of central Chile
2007
Understanding the contact between the very low-grade metagreywacke of the Eastern Series and high-pressure metamorphosed schist of the Western Series in the Late Palaeozoic accretionary wedge of central Chile is fundamental for the understanding of the evolution of ancient accretionary wedges. We show the progressive development of structures and finite strain from the least deformed rocks in the eastern part of the Eastern Series of the accretionary wedge to high-pressure schist of the Western Series at the Pacific coast. Upright chevron folds of sedimentary layering are associated with an axial-plane foliation, S1. As the F1 folds became slightly overturned to the west, S1 was folded abou…
REWORKING OF FUSULINIDS AND CALCIPHAERIDS IN THE LERCARA FORMATION (SICILY, ITALY); GEOLOGICAL IMPLICATIONS
2004
Different fusulinids have been identified in the Lercara Formation (Sicily). They are: Reichelina sp., Schubertella paramelonica, Toriyamaia (?) sp., Neofusulinella lantenoisi, Yangchienia compressa, Rauserella staffi, Darvasites contractus, Chalaroschwagerina (Taiyuanella?) aff. davalensis, Levenella aff. evoluta, Pamirina darvasica, and Neoschwagerina ex gr. craticulifera. Small Permian foraminifers, as well as the calcispherid Asterosphaera pulchra also exist. The microfossils indicate reworking of different Permian stages, at different periods of time, and possibly also of the Mississippian (Early Carboniferous). All these resediments have been deposited within the Lercara Formation, a …
Unravelling extrinsic and intrinsic factors of the early Palaeozoic diversification of blastozoan echinoderms
2010
19 pages; International audience; The Subphylum Blastozoa represents more than one third of the early Palaeozoic echinoderm fauna. A comprehensive database including all records of blastozoans was built to provide quantitative analyses of palaeogeography and diversity patterns and processes, for the 10 classes currently included in this subphylum during the early Palaeozoic. The global pattern of taxonomic diversity shows two peaks during the Cambrian Series 3 and the Late Ordovician intervals. In Cambrian times, the high taxonomic diversity seems to be related with a high turnover rate and a high endemicity of blastozoan genera, whereas in Ordovician times, the rise in diversity is associa…