Loess and loess-like sediments cover approximately 13% of the Bulgarian territory, mainly within the Danubian plain. From the Danube River to the Fore-Balkan, the loess soils form a loess complex where its depth varies from 50–60 meters in the north to few meters in the south, respectively. Widespread loess sediments possess a specific feature: they typically form deep unsaturated zones. Quantification of the near surface water balance is extremely important for evaluating land-atmosphere interactions, and the impact of land-use change on the subsurface flow and the evapotranspiration rate is an essential term in this quantification. In the frames of a scientific project, an automatic weather station was installed in a typical plain terrain of the loess complex in Northeast Bulgaria, recording meteorological data from September 2015 to February 2017.
This study provides a mathematical description of processes (i.e., Penman-Monteith and Hargreaves Methods) used to estimate daily evapotranspiration rates implemented into the numerical model HYDRUS-1D, as well as a respective rate investigation of months with and without intensive rainfalls. Overall results indicate that using the Hargreaves formula for evaluation of the potential evapotranspiration leads to overestimation between 10% and 20%, respectively for a “wet” and “dry” month.
The investigations of the Upper Cretaceous Panagyurishte and Chelopech volcano-sedimentary strips of the Central Srednogorie tectonic subzone date back to the end of 19th and became more intensive during the middle of the 20th century, mainly due to the discovery of important mineral deposits in the area. Our field work during the last 15 years and analysis of previously published data show that the existing lithostratigraphic scheme does not cover the entire spectrum of lithologies, successions and interrelations in both strips. This study deals with four stratigraphic sections, along the valleys of the Topolnitsa, Kamenitsa and Mirkovska rivers, and their correlation on the basis of the Turonian/Coniacian boundary, local extinction event and palaeontological data that demonstrate the unreliability of already existing schemes. The previously used “layer-cake” stratigraphic model does not reflect the diachronism of the studied units or the existence of subaerial volcano craters, together with synchronous deposits. In this paper, we also propose a subdivision of the intervals containing magmatic and sedimentary rocks into individual members, including non-layered magmatic centres, stratified lava flow and volcanoclastic flow deposits and stratified epiclastic deposits of mainly turbiditic origin, instead of the currently used Chelopech Formation. The presented herein new data do not cover entirely the wide palette of problems with the lithostratigraphy of the area, but clearly demonstrate the necessity of its revision, especially for practical application and better understanding of the Late Cretaceous evolution of the area.
The study covers the coastal slope in the Zelenka locality (northern Bulgarian Black Sea coast). This is a beautiful but also dangerous area due to constant sloping and falling of huge blocks of land on the shore. The slope is composed of Miocene sediments: diatomaceous clays (Euxinograd Formation), unconsolidated aragonite sediments with limestone interbeds (Topola Formation), and a steep limestone rock crown (Karvuna Formation). An assessment of the material eroded from the slope, composed of aragonite sediments of the Topola Formation, for the period from October 2018 to March 2019 was made. The quantities of this material were measured and laboratory tests were carried out on the aragonite sediments. The grain size and plasticity (classification characteristics) of the soil were determined. The surface of the slope is waterlogged (or wet), as water flows down the slope of the contact formed between the Topola and Karvuna formations. The geotechnical studies and mapping of the coastal slope revealed that the erosion processes can affect not only the slope stability, but also of the road integrity, and therefore may pose a real geological risk.
No abstract is available for this article.
Garnet–clinopyroxene–K-feldspar granulite occurs as a thick layer or boudin within the variegated rocks of the Chepelare shear zone in the Central Rhodope massif, Bulgaria. It consists of several domains: mesocratic homogeneous matrix (clinopyroxene–plagioclase–K-feldspar–quartz ± amphibole), porphyroblastic garnet, K-feldspar and clinopyroxene, and strongly foliated fine-grain bands (chloritized biotite–chlorite–prehnite–albite ± epidote). The origin and nature of the matrix mineral association is still unclear. The peak porphyroblast association forms at the expense of plagioclase from the matrix at higher pressure. The fine-grain deformation zones channel the lattermost fluid infiltration. The clinopyroxene-garnet and Zr-in-titanite thermometry give temperatures higher than 790–860 ºC at 2 GPa and, with thermodynamic modeling, suggests crystallization at ~1.8–2.1 GPa and temperature of ~850 ºC in HP granulite field for the porphyroblast granulite association.
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