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Magnetotelluric sounding evidence of development of nappes in the Tuolai Sag, Yin-E Basin

Penghui Zhang, Hui Fang, Xiaobo Zhang, Yaoyang Zhang, Haihong Xu, Yan Peng, Yongzhen Yuan

Acta Geophysica

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2020

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Vol. 68, no. 1

91--104

EN

To explore the tectonic framework and features of stratigraphic distribution in the Tuolai Sag, Yin-E Basin, a 47-km-long magnetotelluric (MT) sounding measurement was performed around Well MAZD1 in the sag. During feld data acquisition, a remote reference technique was used to ensure data quality, with apparent resistivity and phase curves of all measuring points obtained using the Fourier transform, power spectrum selection, robust estimation and other methods. After MT data processing, dimensionality analysis and the degree of two-dimensional deviation indicated that the study area had the dimensionality needed for two-dimensional inversion. The major electrical axis in the sag was determined, using a multipoint–multifrequency point statistical imaging technique, to be in the WNW direction. Within the constraints of the resistivity log data for Well MAZD1, inversion results for TE and TM models were compared, after which the TM model, which corresponded well to geological conditions, was selected for conducting the nonlinear conjugate gradient method inversion and a reliable resistivity model was fnally obtained. Based on regional petrophysical properties, resistivity logging, and near-well bathymetric data, the electrical characteristics of diferent formations within the sag were obtained and a set of low-resistance clastic rock identifed in the lower Carboniferous strata. Based on an integrated analysis of the regional surface geology, tectonic setting, and depositional environment, and within the constraints of gravity to ft with electrical structure, a tectonic framework of two subsags sandwiched by an uplift is proposed for the Tuolai Sag. The scale of the northern subsag is large, with development of pre-Carboniferous nappe as well as of Carboniferous–Permian strata within the lower part of the nappe. The southern subsag is small and flled mainly with Carboniferous–Permian strata.

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Late Ladinian radiolarians from the Tahtalidag Nappe of the Antalya nappes, SW Turkey : remarks on the late Middle and Late Triassic evolution of the Tahtalidag Nappe

Tekin U., Sonmez I.

Acta Geologica Polonica

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2010

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Vol. 60, no. 2

199-217

EN

The late Ladinian to Late Triassic succession of the Tahtalidag (upper) Nappe of the Antalya nappes was studied in the Egregindere section, north of the city of Antalya, SW Turkey. The chert bands in the central part of the section have yielded poorly to moderately preserved radiolarians documenting the Late Ladinian Muelleritortis firma and Muelleritortis cochleata radiolarian zones. Based on the Egregindere succession, a major deepening event, evidenced by radiolarian cherts, took place between the middle and late Late Ladinian. The Late Triassic thick-bedded neritic limestones represent a shallowing-upward sequence, which formed as a result of the horst-like rising of the Tahtalidag Nappe during the Late Triassic block faulting. Fifty-nine radiolarian taxa have been determined from the Upper Ladinian of the Egregindere section. One species (Muelleritortis elegans) and two subspecies (Muelleritortis firma equispinosa and Muelleritortis firma globosa) are described as new.

3

The Tatras - nappes and landscapes

Felisiak I.

Geoturystyka

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2008

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nr 2

75-87

EN

Geological structure of the Tatra Mts is a result of long-lasting processes. The key nappes have already been completed some 65 Ma ago. However as a mountain range the Tatras has emerged at the surface only 5 Ma ago, when a piece of continental crust separated from African continent at the beginning of Mesozoic era ultimately collided with Europe. Thus, the crystalline core of the Tatras, which builts also the highest crest is a fragment of Africa. This monumental mountains are, however, not an effect of the overthrusting but they resulted from young, vertical tectonic movements, which are still active and which sometimes shake the whole Podhale region. The following paper explains how the Tatras were formed. The figures enclosed illustrate the succeeding formation stages of the mountain range and the photographs allow the Reader to compare drawings with the field. Welcome to the Tatras.

PL

Struktura geologiczna Tatr formowała się bardzo długo, a kluczowe dla niej płaszczowiny były już gotowe przed 65 milionami lat. Pomimo tego jako góry Tatry zaczęły się wyraźnie zaznaczać na powierzchni dopiero 5 mln lat temu. Trzeba było aby kawał skorupy kontynentalnej, oderwany od Afryki z początkiem ery Mezozoicznej, ostatecznie wbił się w kontynent Europejski. Jego fragmentem, okruchem Afryki, jest trzon krystaliczny tworzący m. in. Tatry Wysokie. Ich imponujący wygląd nie jest wszakże efektem ruchów nasuwczych a młodych przesunięć pionowych, które do dziś czasami trzęsą Podhalem. Jak to się stało opisuje poniższy artykuł. Zamieszczone w nim rysunki ilustrują kolejne stadia rozwoju Tatr. Liczne zdjęcia pozwalają porównać papierowe konstrukcje z rzeczywistymi dziełami natury. Zapraszam do lektury i wycieczki w Tatry. Autor.