Himalayites treubi DOUVILLE (1912), Fósil índice de Titoniano Superior en el sur-oeste del lago Titicaca, Puno; implicaciones bioestratigráficas.

RESUMEN Con motivo de la actualización de la geología regional del Cuadrángulo de Puno (32v) a escala al 50,000, se han desarrollado diversas labores de campo, como ésta contribución que documenta nuevos resultados de rocas mesozoicas del Grupo Yura en las inmediaciones del Distrito de Tiquillaca, (al SO del Lago Titicaca), tales afloramientos solían asignarse a rocas jurásicas del Grupo Lagunillas. El afloramiento en estudio se halla en el Cerro Yana Apacheta, en cuya quebrada principal se elaboró una columna estratigráfica y el perfil correspondiente en el que se encontró el amonite Himalayites treubi DOUVILLE (1912), estableciendo una correlación con las formaciones Chachacumane y Labra. El taxón se describe con base en cinco ejemplares y sus parámetros estándares de tasa de enrollamiento y ornamentación del costillaje. Se considera que el hallazgo de amonites del Tithoniano en el Cuadrángulo 32v amplía y documenta la columna previamente reportada para la localidad y establece una clara correlación con sedimentos del sur de Asia (Indonesia). ABSTRACT On the occasion of the updating of the regional geology of the Puno Quadrangle (32v) at 50,000 scale, several field works have been developed, such as this contribution that documents new results of Mesozoic rocks of the Yura Group in the vicinity of the Tiquillaca District, (SW of Lake Titicaca), such outcrops used to be assigned to Jurassic rocks of the Lagunillas Group. The outcrop under study is located in Cerro Yana Apacheta, in whose main gorge a stratigraphic column and the corresponding profile was elaborated, in which the ammonite Himalayites treubi DOUVILLE (1912) was found, establishing a correlation with the Chachacumane and Labra formations. The taxon is described based on five specimens and its standard parameters of coiling rate and rib ornamentation. The finding of Tithonian ammonites in Quadrangle 32v is considered to extend and document the column previously reported for the locality and establishes a clear correlation with sediments from South Asia (Indonesia).

NEW DATA ON THE AGE AND MATERIAL COMPOSITION OF THE ROCKS OF THE PRE-JURASSIC BASE OF THE TAISKO-BARABINSK FACIES REGION BASED IN THE UVATSKY DISTRICT OF THE SOUTH OF THE TYUMEN REGION

In the West Siberia the structural-facies zoning of pre-Jurassic rocks is based on 2 factors: structural and tectonic structure and formation composition of rocks. The central areas of the Uvat district are located within the boundaries of the Tuisko-Barabinskiy facies region, where there are two main points of view on the age of the formations underlying sedimentary cover. Some experts believe that these are rocks of Lower-Middle Paleozoic formations (Caledonides), others believe that these are rocks of Upper Paleozoic-Lower Mesozoic formations (Hercynides). The data obtained from the results of drilling over the past 15 years on the territory of Uvat district on the material composition and the age of pre-Jurassic rocks made it possible to clarify the typical section of these sediments in the Tuisko-Barabinskiy region of facies.

On the nature of Paleozoic oil deposits and their exploratory "reflection" in the geophysical section of the Jurassic layers (southeast of Western Siberia)

Commercial significance of the majority of Western Siberian oil fields is concerned with the Senomanian, Neocomian and, above all, Upper Jurassic horizons. For now, oil fields are at the late development stage and resource potential of the Jurassic horizon is strongly expired. Commercial potential of the pre-Jurassic (Paleozoic) rocks has been brought out throughout all territory of oil and gas province. Extensive work on estimation of the pre-Jurassic rocks oil and gas potential is performed in southeast, in the territory of Tomsk Region, within which 13 hydrocarbon deposits have been discovered in the Paleozoic. Original hypothesis of anomalousness of geophysical and petrophysical characteristics of the Jurassic layers — uniqueness of «indication» the Paleozoic deposits in geophysical parameters of overlaying Mezozoic-Cenozoic section was stated as a foundation of new prospecting criterion for the Paleozoic deposits. The Paleozoic formations are accepted as a complex with its own oil generating potential, which results in upward migration of hydrocarbon fluids. Additionally, downward direction of vertical interstratal hydrocarbon migration from the Jurassic source rocks into the pre-Jurassic complex is brought out. It was accepted as a conception that as in case of upward, so in case of downward fluid migration, processes of superposed epigenesis perform and lead to secondary epigenetic transformations of rocks of transit Jurassic layers, which result in their anomalous geophysical and petrophysical characteristics. This paper analyzes and compares geophysical and petrophysical characteristics of the Jurassic layers of different field types in Tomsk Region: without oil and gas potential in pre-Jurassic section, with commercial inflows from the pre-Jurassic complex and unknown type. Results of exploration electrical resistivity and carbonatization in the Jurassic layers of 200 wells and also spontaneous potential variation, electrical resistivity and natural radioactivity in Bazhenov suite confirm anomalousness of geophysical and petrophysical parameters of Jurassic rocks in case of pre-Jurassic deposits. This paper determines 6 geophysical and petrophysical characteristics of the Jurassic layers as predictive indicators for oil and gas potential estimation in pre-Jurassic section. Efficiency analysis of using predictive indicators for bringing out fields with and without deposits in the pre-Jurassic complex was performed for different prospecting cases in the research territory with account taken of possible complexing of indicators, their rank and actual availability. This paper states preference of indicators complexing. Application of a new prospecting criterion will improve efficiency of searching in new prioritized stratigraphic horizon — the Paleozoic, which contains unconventional oil.

Evolution of the Tazones Lighthouse slope (Cantabrian coast, N Spain). Multidisciplinary monitoring between 2018 and 2020

The Tazones Lighthouse slope shows different active mass movements affecting an area of 70.000 m2 of the Cantabrian Coast (N Spain), characterized by almost vertical rocky cliffs developed on Jurassic rocks: alternating marl, sandstone and limestone with three main stratigraphic and structural discontinuity families. Between June 2018 and May 2020, 22 monthly monitoring campaigns have been carried out to measure the displacement of 38 control points, located between 95–110 masl. The total station monitoring has been complemented by ortophoto analysis and detailed digital terrain models (DTM) from two drone flights. Since the beginning of the 3D monitoring, about the 50 % of the markers moved more than 1 m, one of them exceeding 15 m. Detailed DTM has shown that the increased activity is controlled by the discontinuities. There is an extraordinary correlation between displacement acceleration and precipitation and soil moisture: the largest displacements have occurred after 2 periods of intense rain (January and October–November 2019, with a maximum 24-hour precipitation of 64.5 mm and 82.1 mm, respectively, and soil moisture values higher than 90 %). This represents an exceptional opportunity to analyse in real time the Jurassic cliffs retreat of the Cantabrian Coast, a question that remained not quantified.

Physical and Mechanical Performance of Frozen Rocks and Soil in Different Regions

The artificial freezing method is extensively used in the reinforcement of engineering strata in various regions for shaft excavation and subway connection channels. In this study, representative rock and soil strata from different regions were subjected to low-temperature physical and mechanical performance tests. The results show that, compared with Cretaceous and Jurassic rock and soil strata, deep topsoil and shallow coastal topsoil have high water content, low thermal conductivities, high frost heave rates, and high freezing temperatures. In addition, the results show that, as the curing temperature decreases, the uniaxial compressive strengths and elastic moduli of deep topsoil and shallow coastal topsoil increase almost linearly. The strength of the sandy soil strata is the highest, followed by the cohesive soil strata, and the strength of the mucky soil and the calcareous clay is the lowest. The strength of the frozen wall and the waterproof requirements must both be taken into account in the freezing design. Deep Cretaceous and Jurassic rocks can have high strength of more than 5 MPa under normal temperature conditions. An increase in the uniaxial compressive strength and elastic modulus with decreasing curing temperature is mainly manifested within the range from the normal temperature to −10°C. The strength can reach more than 10 MPa at −10°C, and only the strength requirements of the frozen wall need to be considered in the freezing design. At low temperatures, deep topsoil and shallow coastal topsoil are dominated by the form of compression failure. The average failure strain at −10°C is typically greater than 5%. When excavating the strata, it is essential to pay attention to the effect of creep. The failure strain of deep Cretaceous and Jurassic rocks is between 1% and 2%, and the breaking and sudden collapse of surrounding rocks should be prevented.

Correction to: Integrating the palynostratigraphy, petrography, X-ray diffraction and scanning electron microscopy data for evaluating hydrocarbon reservoir potential of Jurassic rocks in the Kala Chitta Range, Northwest Pakistan

In the original publication of the article.

Behavioural variation in limulids (Xiphosurida) from the Middle Jurassic of the Cleveland Basin, Yorkshire, UK, as deduced from their traces: a review and reappraisal

The paper is a study of horseshoe crab (limulid) behaviour, based on their ichnites from the Middle Jurassic rocks of the Cleveland Basin, Yorkshire, UK, from a succession spanning a period of c. 8 myr. Five named ichnospecies have been recognized from this sequence as having a limulid maker: Selenichnites hundalensis, S. rossendalensis, Kouphichnium aff. variabilis, K. cf. arizonae and Crescentichnus tesiltus, as well as unassigned ichnospecies (K. isp. indet., S. isp., S. isp. indet., and C. ispp. indet.). These traces have been interpreted as showing behavioural patterns during burial, feeding, locomotion and probing. The occurrence of these traces in both non-marine and marine strata together with their presumed lifestyle is compared to what is known of extant horseshoe crabs, and any difference in lifestyle is discussed.