This article presents geotechnical reconnaissance data that characterize the formation of 122 new and 49 historical cover-collapse sinkholes within 1.13 km2 area in 12 months following the MW 6.4 ...earthquake that occurred on 29 December 2020, in Petrinja, Croatia. Data include a geological background, seismic sequence information, sinkhole geometric characteristics, rainfall data, and results of detailed geotechnical subsurface investigation. The sinkhole geometrical features were collected using aerial and satellite imagery, terrestrial lidar, and manual measurements. Soil properties and groundwater levels were obtained from four geotechnical boreholes, accompanied by in situ geotechnical characterization and standard penetration tests (SPTs). Soil parameters were obtained from consolidated undrained conventional triaxial compression, oedometer, soil water retention, and index tests performed on 31 soil samples. Clayey cover, 4-10 m thick, with sporadic gravel lenses overlying cavernous, intensely karstified carbonate rocks, characterizes the sinkhole area. Clays are mostly overconsolidated, with varying degrees of saturation ranging from very small to fully saturated. Seasonal and climate-induced variations in the groundwater table interact with artesian/subartesian karst aquifer, thus affecting the suction and the shear strength. Soil water retention curves (SWRCs) indicate that desaturation is possible for deeper groundwater tables, thus further affecting the effective stress, shear strength, and interparticle tensile forces. Finally, the observed vertical walls that accompanied sinkholes opening can occur in the overconsolidated cohesive cover clay layer with varying degree of saturation. The presented data provide essential geomechanical information necessary to understand the associated sinkhole failure mechanism. This article will help future investigators to perform detailed analyses and provide a background for complementing future sinkhole precursor research. Geotechnical, geological, seismic, and precipitation data generally indicate that the formation of cover-collapse sinkholes in the study area is a consequence of a specific local geological setting but is significantly expedited by earthquake-induced dynamic loading and complemented by multiple hydro-mechanical factors.
The Minjera bauxites are the first analysed and mined bauxites in the world. They are a group of pyritised bauxites situated in northern Istria, developed during the subaerial exposure phase which ...marked a major part of the Late Cretaceous and Palaeocene in northern Istria. In this study, the morphology, petrography, mineralogy, geochemistry as well as stable sulphur isotopes of the D-1 and D-15 deposits from Minjera were studied, as well as the evolution of their bedrock and cover. This study found that those two deposits differ in morphology, mineralogy and geochemistry as a consequence of their different palaeotopographical positions, with the D-1 deposit located at a higher position at the time of its formation compared to D-15, which led to the higher degree of leaching and desilicification in the D-1 deposit. The pyritisation in the studied deposits was a multi-phase process, which began with the deposition of framboidal pyrite and micrometre-sized anhedral pyrite, over which colloform pyrite was precipitated. This indicates that the solutions were initially supersaturated with iron sulphide, saturation of which subsequently changed, as finally euhedral, dendritic and acicular pyrite were deposited, indicating undersaturated conditions. The final stage was marked by deposition of pyrite veins. This formational sequence of pyrites is also supported by stable sulphur isotopes, as the δ34S values exhibit a wide range from -40.86 to 2.32 ‰, where lower values indicate an open system with an unrestricted sulphate supply in which supersaturated conditions could have been achieved, while the higher values indicate a change towards a closed system with limited sulphate supply. The organic matter necessary for microbial sulphate reduction was derived from the marshy environment established atop of the bauxite. The initial flooding started in the Palaeocene, with the first part of the sequence being deposited under lacustrine conditions, which changed towards fully marine with the deposition of Foraminiferal limestones.
•Palaeosol associated with Upper Jurassic unconformity hosts glauconite.•Glauconite formed by halmyrolysis of a palaeosol.•Formation of glauconite was microbially mediated.•Glauconite may mark ...initial flooding of subaerially exposed terrain.•Glauconite as an indicator of paleolandscape and paleoenvironment.
Glauconite formation is generally perceived as a process occurring in deep-marine environments, but in the last few decades its formation in shallow-marine environments is progressively more recognised and utilized for palaeoenvironmental reconstructions. One such example is the lower Kimmeridgian to upper Tithonian Zlatni Rt palaeosol, which is especially unique since the glauconite occurrence is hosted within the palaeosol material. Micromorphological, mineralogical, and chemical characterisation of the palaeosol was followed by the detailed analysis and description of glauconite using SEM-EDS, XRPD and FTIR. In addition, lithofacies and micropalaeontological analyses have been carried out on the carbonate succession under- and overlying the palaeosol in order to better understand the stratigraphic framework. The palaeosol formed in hydromorphic conditions, in contact with brackish to marine porewater, and is composed of mixed-layer illite–smectite, illite, kaolinite, vermiculite, pyrite, marcasite and titanium oxides. The glauconite was formed after the formation of the palaeosol, predominantly through fixation of potassium and iron into illite and mixed–layer illite–smectite, while part of the glauconite formed authigenically, with evidence for microbial influence. The glauconite is present in a more oxidised and more reduced form, which alternate together with pyrite in veins, indicating fluctuations in the redox potential. This can be connected to the variations in the supply of organic matter and sea-level oscillations during the initial stages of the transgression. Glauconite formation was locally followed by the formation of transgressive breccias and a complete drowning of the area. During this phase lagoonal Kirmenjak limestone was deposited throughout the area, while in the palaeosol coarse pyrite crystals precipitated. Presented study documents a unique glauconite occurrence and proposes that it can be successfully used for the detailed palaeoenvironmental reconstruction of the initial flooding of subaerially exposed terrains.
Abstract Aim Our study aimed to examine the prevalence of non-diabetic renal disease in selected patients with type 2 diabetes mellitus and to determine important risk factors for non-diabetic renal ...disease. Methods We conducted retrospective analysis of clinical, laboratory and pathohistological data of type 2 diabetes mellitus patients in whom renal biopsies were performed from January 2004 to February 2013 at Dubrava University Hospital Zagreb Croatia ( n = 80). Results According to renal biopsy findings, isolated diabetic nephropathy was found in 46.25%, non-diabetic renal disease superimposed on diabetic nephropathy in 17.5% and isolated non-diabetic renal disease in 36.25% of the patients. The most common non-diabetic renal diseases found were: membranous nephropathy, followed by IgA nephropathy and focal segmental glomerulosclerosis. In univariate analysis shorter duration of diabetes, independence of insulin therapy, lower levels of HbA1c and absence of diabetic retinopathy were found to be significant clinical predictors of non-diabetic renal disease. In multivariate analysis only independence of insulin therapy (OR 4.418, 95%CI = 1.477–13.216) and absence of diabetic retinopathy (OR 5.579, 95%CI = 1.788–17.404) were independent predictors of non-diabetic renal disease. Conclusions This study confirmed usefulness of renal biopsy in patients with type 2 diabetes mellitus, due to the high prevalence of non-diabetic renal disease found. Since non-diabetic renal disease are potentially curable, we should consider renal biopsy in selected type 2 diabetes mellitus patients with renal involvement, especially in those with absence of diabetic retinopathy and independence of insulin therapy.
