Geology, Geophysics & Environment
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ISSN 2299-8004
e-ISSN: 2353-0790
Issue Date
2020
Volume
Vol. 46
Number
No 3
Description
Journal Volume
Geology, Geophysics & Environment
Vol. 46 (2020)
Projects
Pages
Articles
An Entzia-dominated marsh-type agglutinated foraminiferal assemblage from a salt marsh in Tubli Bay, Bahrain
(Wydawnictwa AGH, 2020) Kaminski, Michael A.; Amao, Abduljamiu O.; Garrison, Thomas F.; Fiorini, Flavia; Magliveras, Simeon; Tawabini, Bassam S.; Waśkowska, Anna
A salt-marsh assemblage of agglutinated foraminifera was recovered from a salt marsh on the east side of Tubli Bay in eastern Bahrain. This locality is one of the last remaining patches of salt marsh on the east coast of Tubli Bay. The salt marsh is covered by a single marsh plant species, <i>Arthrocnemum macrostachyum</i>. Samples were collected from beneath the <i>Arthrocnemum</i> canopy in two transects beginning at the maximum landward extent of halophytic plants in the high marsh and extending to a tidal channel at the seaward side of the low marsh. A distinct elevation-related zonation in foraminifera is observed from the high marsh to the low marsh. The trochamminids <i>Entzia macrescens</i> and <i>Trochammina inflata</i> are characteristic of the high marsh, whereas <i>Ammonia</i>, <i>Elphidium</i>, <i>Peneroplis</i> and smaller miliolids become common in the middle part of the marsh transect. The tidal channel at the lower limit of the marsh contains an assemblage dominated by <i>Ammonia</i>, <i>Elphidium</i>, adult specimens of <i>Peneroplis</i>, and smaller miliolids, with <i>Clavulina</i> and <i>Agglutinella</i> as the only agglutinated taxa. Living specimens of <i>Entzia</i> and <i>Trochammina</i> were observed during the winter 2019–2020 sampling season, whereas samples collected in Autumn 2019 contained only dead specimens. One new species, <i>?Sigmoilina canisdementis</i> sp. nov., is described herein. This is the first report of a live <i>Entzia</i>-dominated salt marsh assemblage in the Arabian Gulf region.
The geomorphology of the Makran Trench in the context of the geological and geophysical settings of the Arabian Sea
(Wydawnictwa AGH, 2020) Lemenkova, Polina
The study focuses on the Makran Trench in the Arabian Sea basin, in the north Indian Ocean. The area is tectonically active, with a system of ridges and fracture zones morphologically separating the Arabian Sea. The study examined the relationships between the topographic structure of the Makran Trench and the regional settings of the Arabian Sea: geomorphology, sediment thickness, geophysical fields, geology and tectonic lineaments. The methodology is based on the GMT scripting toolset. The spatial analysis includes high-resolution datasets GEBCO, EGM2008, GlobSed and data on tectonics, geology, geophysics, sediment thickness and topographic terrain model visualized by GMT. The paper also defined a way in which the proprietary ESRI data format can be transformed into the freely available GMT geospatial data of the geoid EGM2008 model. The geomorphological modeling included the automatic digitization of 300-km width cross-section profiles of the trench demonstrating its submarine relief. The analysis showed a correlation between the geological and tectonic structures, asymmetric geomorphology and geophysical anomaly fields. Gravity data indicate a crustal structure with anomalies generated by the bending of the lithosphere into the Makran subduction zone and density variations in the mantle reflected on the gravity maps. The gravity correlates with lineaments of the geomorphic structures. Bathymetric analysis revealed the most frequent depth (448 samples) at −3,250 to −3,500 m, followed by intervals: −3,000 to −3,250 m, −2,750 to −3,000 m. The declining continental slope correlates with gradually decreasing depths as equally distributed bins: 124 samples (−2,500 to −2,750 m), 96 (−2,250 to −2,500 m), 86 (−2,000 to −2,250 m). The trench is an asymmetric form with a high steepness on the continental slope of Pakistan and low steepness with a flat valley on the oceanward side. The multi-source data integration is important for seafloor mapping and the geomorphological analysis of oceanic trenches hidden to direct observations. The machine learning methods of GMT and cartographic modeling provide possibilities for the effective visualization of the trench. The comparison of the geomorphology with gravity anomalies, tectonic lineation, geological structures and topographical variations provides more detail to studies of the seafloor in the Arabian Sea.
Change-point detection and trend analysis in monthly, seasonal and annual air temperature and precipitation series in Bartın province in the western Black Sea region of Turkey
(Wydawnictwa AGH, 2020) Yaman, Barbaros; Ertuğrul, Mertol
Studies associated with climate change and variability are of great importance at both the global and local scale in the global climate crisis. In this study, change-point detection and trend analysis were carried out on mean, maximum, minimum air temperatures and total precipitation based on monthly, seasonal and annual scale in Bartın province located in the western Black Sea Region of Turkey. For this aim, 4-different homogeneity tests (von Neumann test, Pettitt test, Buishand range test and standard normal homogeneity test) for changepoint detection, Modified Mann–Kendall test and Şen's innovative trend test for trend analysis, and Şen's slope test for the magnitude estimation of trends were used. According to the test results, the summer temperatures in particular show increasing trends at the 0.001 significance level. Mean maximum temperature in August, mean minimum temperature in June and August, and mean temperature in July and August are in increasing trend at the 0.001 significance level. Over a 51 year period (1965–2015) in Bartın province, the highest rate of change per decade in air temperatures is in August (0.55°C for T$_{max}$, 0.46°C for T$_{min}$ and 0.43°C for T$_{mean}$) based on Şen's slope. However, the study showed that apart from October precipitation, there is no significant trend in monthly, seasonal and annual precipitation in Bartın. Increasing trends in mentioned climate variables are also visually very clear and strong in Şen's innovative trend method, and they comply with the statistical results. As a result, the study revealed some evidence that temperatures will increase in the future in Bartın and its environs.
Spatial distribution of radiogenic heat in the Iullemmeden basin – Precambrian basement transition zone, NW Nigeria
(Wydawnictwa AGH, 2020) Aisabokhae, Joseph; Adeoye, Moses
The area which transcends the Precambrian basement complex onto the Sokoto sector of the Iullemmeden basin in northwestern Nigeria presents a unique prospect for geothermal exploration research in the absence of regional heat production data, despite its tectonic history and depositional characteristics. In this study, geophysical exploration employing radiometric technique was adopted to classify the petrologic units within the fringes of the Iullemmeden basin and the adjoining crystalline basement complex so as to estimate the radiogenic heat potential within the terrain that may support geothermal considerations. Airborne radiometric measurements acquired over the area were digitized and processed to obtain radioelement concentration maps and the K/Th/U ternary map. Results show that the ranges of measured concentrations of $^{40}$K, $^{238}$U and $^{232}$Th are 4.6 to 18.9%, 0.7 to 4.9 ppm and 4.6 to 18.9 ppm respectively. Radiogenic heat estimation derived from radioelement data within eight petrologic units comprising quaternary sediments, schist, carbonates, shale/clay, younger granites, older granites, gneissic rock and migmatite showed that the lowest radiogenic heat production estimates ranging from 0.27–0.66 µW $\cdot$ m$^{-3}$ were recorded in the sedimentary terrain within the quaternary sediments while the highest radiogenic heat production values of between 2.04 to 2.34 µW $\cdot$ m$^{-3}$ were recorded in the basement complex within gneissic rocks. The spatial distribution of radiogenic heat in the area showed an increased heat gradient within the basement complex and a diminishing heat gradient over the Iullemmeded basin.
Progress in the development of the semi-empirical calibration of neutron probes based on Monte Carlo modeling
(Wydawnictwa AGH, 2020) Woźnicka, Urszula
The method of the semi-empirical calibration of a neutron well logging probe was developed by Jan Andrzej Czubek on the concept of the general neutron parameter (<i>GNP</i>) and tested positively at the neutron calibration station in Zielona Góra, Poland. The neutron probe responses in a wide range of neutron parameters (and thus lithology, porosity and saturation) were also computed using the Monte Carlo method. The obtained simulation results made it possible to determine the calibration curves using the Czubek concept in a wider range than by means of the original method. The very good compatibility of both methods confirms the applicability of the <i>GNP</i> as well as the Monte Carlo numerical experiments, which allow for a significant extension of the semi-empirical calibration in complex well geometries taking into account e.g., casing or invaded zones.