Impact of Geomorphological Variables in Weighing the Lithological Influence on Geochemical Composition of Stream and Overbank Sediments: A Regression Model for the Zumberak Area (NW Croatia)

The two multiple regression models were compared on the assumption that the geochemical composition of the alluvial material is basically originally derived from the bedrock lithology of a drainage basin of the Zumberak Area (NW Croatia). The latter was integrated with both stream sediment and overbank sediment geochemical data via the two essentially different approaches as regards the catchment basin geomorphological data: (1) as the relative area of influence representing a portion of the catchment basin occupied by a certain rock type; (2) as the relative “line” of influence representing a narrow tract of a certain rock type traversed by the majority of perennial streams which form the active stream network. The model comparison was accomplished on the basis of the goodness-of-fit test for both experimental designs and for the same set of data. The most important result of these experiments highlights the linear approach as the more appropriate model for ascertaining the lithological influence on the analyzed sample media. This can be explained by the stronger erosive and transportational power of the water which flows in the well defined channel network in contrast to the unconcentrated surface runoff in the interfluvial area, coupled with the buffering effects of rich slope and riparian vegetation, which is characteristic of the Zumberak heartland

Geochemical Comparison of Stream and Overbank Sediments: A Case Study from the Zumberak Region, Croatia

Geochemical comparison between the stream and overbank sediments from low- to medium-order drainage basins is grounded on the presupposed statistical contradistinction of their locality-paired sample correlatives. Discriminant analysis differentiated the overbank from stream material mainly on account of higher content of most of the analyzed elements in the former vis-a-vis an otherwise common geochemical semblance. Only the carbonate material seems to be depleted in overbank sediment samples. Investigations also demonstrated that in the relatively non-contaminated area it may be more difficult to verify the supposed purity-contamination reciprocity between the investigated media, since the recent and prehistoric materials were not contrasted as regards their non-lithogenic components

Geochemical Comparison of Stream and Overbank Sediments: A Case Study from the Zumberak Region, Croatia

Geochemical comparison between the stream and overbank sediments from low- to medium-order drainage basins is grounded on the presupposed statistical contradistinction of their locality-paired sample correlatives. Discriminant analysis differentiated the overbank from stream material mainly on account of higher content of most of the analyzed elements in the former vis-a-vis an otherwise common geochemical semblance. Only the carbonate material seems to be depleted in overbank sediment samples. Investigations also demonstrated that in the relatively non-contaminated area it may be more difficult to verify the supposed purity-contamination reciprocity between the investigated media, since the recent and prehistoric materials were not contrasted as regards their non-lithogenic components

Qualitative–Quantitative Analyses of the Influence of Depth and Lithological Composition on Lower Pontian Sandstone Porosity in the Central Part of Bjelovar Sag (Croatia)

Results of several tests (porosity–depth graphic relation, t-test, F-test, Pearson’s R), were used to analyse and interpret the regularity in porosity values of Lower Pontian oil-bearing sandstones from the central part of Bjelovar sag. Data came from 7 cored intervals within 5 wells in the Pepelana member and from 6 cored intervals (in 4 wells) in the Poljana member. The expected porosity decrease with increasing depth was checked against lithological variations. Sandstones are mostly fine-grained lithoarenites. The detritus is composed of quartz, various micas, carbonate fragments and feldspars. Across the study area, the depth range of the sandstones varies from 430 m (top of the Pepelana member near Sandrovac) to 2046 m (base of the Poljana member near Velika Ciglena). Cores included in the analyses vary between 2.75 to 15.5 m in length. Mean porosity and relative depth data were collected for two groups: Group 1 comprised wells Pav–1, Pav–2, Rov–1, Sa–5, Sa–35, and Group 2 included well VC–1. These groups were subdivided for analysis into two (litho)stratigraphic units (Pepelana and Poljana ss.). Porosity variation within each group is explained with reference to the silt or clay fraction. Differences between the porosities of the two groups (~10% lower absolute porosity near Velika Ciglena) is the result of compaction and other processes. Interval of 400 m thickness in particular sandstone member is set as minimum value for observing influence of compaction. Such statement is based on sandstone’s tops and bottoms comparison as well as graphical presentation of relation core porosity–relative depth interval. The analysis was improved by statistical calculation of Pearson’s R, t-test and F-test, which more precisely described the relationship between porosity and depth. Using these statistical tests and regression equitation, the depth difference is calculated as 621 m in the Pepelana and 667 m in the Poljana sandstones, as the limits when the influence of compaction in the porosity–depth relationship could be noticed. Compaction was observed, in the study area, when data from Velika Ciglena are compared to data from the other wells

Normalization and Trace Element Contamination of Soils in a Karstic Polje - An Example from the Sinjsko Polje, Croatia

Estimation of the anthropogenic over natural contribution in the chemical content of soils and sediments is very important but not easy to measure. Normalization based on either aluminium or iron, as reference conservative elements having supposed natural distributions, is a useful tool in solving this problem. However, several independent factors can influence the normalization procedure, which if not taken into account could lead to completely erroneous conclusions about the origin of the particular elevated concentrations of certain elements. Therefore, a great deal of caution should be exercised during application of the normalization procedure. Analytical data from 95 soil samples from the Sinjsko polje enabled us to critically apply this procedure. Linear regression analysis, evaluation of enrichment factors and trend surface analysis with the construction of appropriate maps were used to test the procedure. Presuming an existing linear dependence between the conservative element and the heavy metal it is possible with the use of linear regression to simultaneously define the heavy metal geochemical background (baseline) and to isolate natural and/or anthropogenic outliers (anomalies). Coupled with geographic plotting facilities this type of outlier-screening is used to locate areas of man made pollution. Statistical treatment of selected elements included the calculation of means, standard deviations and other estimates of basic statistic parameters. Evaluation of enrichment factors reveals the dependence of this parameter upon four main factors: the choice of reference element; the choice of reference material; the homogeneity of reference element distribution in the study area; and correlation of particular element with reference element. Examination of trends is a common procedure in the analysis of geochemical maps. Its purpose is to segregate the underlying trend that possibly pervades the study area, from the local variations, that is, the “noise” or “background”. Statistical analysis, as suggested by the results in this work, would be more properly used over general areas in the karstic terrain, with different geological, geomorphologic and hydrogeological characteristics, rather than being focused on the relatively small phenomena such as poljes, with many local geologic, hydrogeological and geochemical constraints

Frequency Distribution Curves as an Indicator of Evolutionary Trends in Geomorphological Systems: A Case Study from the Northwestern Part of Hrvatsko Zagorje (Croatia)

Frequency distribution curves can be indicative of the dynamics and evolutionary development of geomorphological systems. Normally distributed geomorphological data are a reliable indicator of the equilibrium fluctuations prevalent within such systems. This occurs, for example, when a delicate balance is established between various types of landforms and geomorphological processes. Landforms that exist in this geomorphological steady state can be properly called “equilibrium” structures. They show no permanent trends of either growth or destruction. On the contrary, a positively skewed frequency distribution curve indicates a type of non-equilibrium conditions and non-linear relationships within geomorphological systems, which may be the result of major external energy inputs (particularly from tectonic uplift). This, in turn, gives rise to new and more complex higher-order landforms. These represent structures of growth, or evolution. Alternatively, a negatively skewed frequency distribution curve, also being a consequence of non-equilibrium conditions, indicates a lack of free energy in the system, which induces destruction of the existing landforms. Such landforms represent structures of degeneration. The fluvial landscape in the northwestern part of Hrvatsko Zagorje, portrayed in terms of an open system, has been used as the geomorphological framework for this study, the primary purpose of which was to apply frequency distribution curves in the interpretation of the processes influencing the creation and destruction of the landscape. Horizontal and vertical dissection, slope and other morphometric characteristics reflect the specific dynamics of the geomorphological processes, which relate a variety of landforms to their geologic framework and climate in the study area

Interdependence of Petrophysical Properties and Depth: Some Implications of Multivariate Solution on Distinction Between the Lower Pontian Hydrocarbon-bearing Sandstone Units in the Western Part of the Sava Depression

Statistical analysis of reservoir data from the Lower Pontian clastics (the most important hydrocarbon reservoir rocks in the Sava depression), supports established knowledge of the interdependence of petrophysical properties and depth. Irrespective of the focus that the reservoir data may be studied and presented, depth always emerges as a fundamental reservoir descriptor. This is particularly evident when studying the differences between widely spaced oil and gas fields, when the numerical model completely separates the two sets of descriptor variables, indicating two different sources of their internal variability. Porosity and permeability belong to “intrinsic rock properties” while depth must be ascribed to other sources, e.g. tectonic subsidence. Discriminant function weighted with depth (DF1) has such group centroid values, that zones can be drawn within a particular field that coincide with structural relationships. On the function marked with reservoir properties (DF2), group centroid values are higher close to the axes of palaeotransport channels, where sandstone layers are the thickest and particles are best sorted. Group centroid values on the third function (DF3) depict the areas of relatively higher permeability in the apical parts of structures, possibly caused by fracturing due to folding, or by cementation of other parts of reservoirs, where the circulation of pore waters was more pronounced. In the case of the most thoroughly investigated Zutica field, the inverse relationship between depth and porosity becomes evident when compared with the direction of palaeotransport and thickness of reservoir rocks on the respective structure and thickness maps

A Factor Model of the Relationship between Stream Sediment Geochemistry and Adjacent Drainage Basin Lithology, Medvednica Mt., Croatia

A mathematical model is constructed to relate the geochemical composition of recent stream material in a number of catchments on Medvednica Mt. to a broadely defined bedrock lithology which represents the parent material for the former. It is a system based factor model, which synthesizes eight lithological and 25 geochemical variables (major, minor and trace elements), reducing their relationships to six geologically meaningful factors. Five of these divulged a definite relationship between geochemistry and lithology. These are labelled as follows: factor of metamorphic rocks; factor of igneous rocks; factor of Tertiary carbonate rocks; factor of parametamorphic rocks and factor of Mesozoic carbonate rocks. Two lithologies; the Mesozoic clastic rocks and Quaternary sediments showed no clear association to any of the factors. Alternatively, one of the factors (F2) can be identified as “non-lithologic” indicating other, perhaps anthropogenic, contributions to the stream sediment geochemical composition

Pozadinski geokemijski šum u tlima Istre

The geochemical background is postulated for two major groups of soils of the Istrian Peninsula, depending on the type of bedrock, or parent material as one of the main soil-forming factors. An effort is made to combine conceptual fundamentals of non-linear dynamic theory with the principles, methods and practical application of basic statistics in order to elucidate the nature and origin of elemental subpopulations hidden in the original geochemical data of Istrian topsoils. In this sense, the 4σ-outlier test and iterative 2σ-statistical technique are utilized, by which the outliers and anomalous values are removed from the total data set and assigned to the consequences of non-linear system dynamics, which prevents the development of a simple cause-and-effect relationship between geochemical variables. The geochemical background is then defined as the normal range of data of the remaining data set. As confirmed by the study, the carbonate-derived soils have a higher natural or geogenic baseline and are also more strongly loaded with heavy metals and other trace elements, in some places critically. On the other hand, flysch-derived soils, except for higher Ca contents, are actually depleted in many elements and also devoid of outliers. Such behaviour implies »dilution« due to the characteristic nature of the weathering of the underlying parent material and other soil-forming processes controlling their fate. In a general sense, the character of the probability distribution curves among chemical elements in the topsoil (or soils in general) can be used as reliable indicator of their evolutionary trends, that is, their enrichment or depletion, or, as regards the geochemical background, the equilibrium between the two, which in the case studied depends principally upon the contrasting Istrian bedrock lithology.U radu je razmatran geokemijski šum zasebno za dvije skupine tala na Istarskom poluotoku, ovisno o tipu geološke podloge, odnosno ishodišnog materijala kao jednog od glavnih čimbenika u razvitku tla. Povezana je teorija nelinearnih dinamičkih sustava s načelima, metodama i praktičnom primjenom elementarne statistike s ciljem da se razjasni priroda i porijeklo elementnih subpopulacija skrivenih u izvornim geokemijskim podacima površinskog horizonta istarskih tala. U tu svrhu korištene su statističke metode – 4σ-test za određivanje ekstremnih vrijednosti i 2σ-metoda iteracije – kojima su ekstremi i anomalne vrijednosti odvojeni od glavnog skupa podataka i pripisani posljedicama nelinearne sistemske dinamike koje su brana uspostavi jednostavnih, uzročno-posljedičnih odnosa među geokemijskim varijablama. U skladu s navedenim, geokemijski šum je određen kao raspon normalnih vrijednosti reduciranog skupa podataka nastalog nakon oba statistička postupka. Pokazalo se da tla razvijena na karbonatnim stijenama imaju višu prirodnu razinu kemijskih elemenata, a također sadrže i veću koncentraciju teških metala i elemenata u tragovima koja je na pojedinim lokacijama i ekstremno visoka. S druge strane, tla razvijena na flišu, s izuzetkom povišenog sadržaja kalcija, u stvarnosti su siromašnija sadržajem većine elemenata i ne sadrže ekstremnih vrijednosti. Takvo ponašanje ukazuje na »razrjeđenje« zbog karakteristične prirode trošenja ishodišnog materijala i drugih čimbenika koji utječu na raspodjelu elemenata u površinskom horizontu tla. U općem slučaju, karakter krivulje statističke distribucije elemenata kemijskih elemenata u površinskom horizontu (i u tlu općenito) može se uzeti kao pouzdan pokazatelj evolucijskih trendova, odnosno obogaćenja ili osiromašenja pojedinim elementima ili, kad je riječ o geokemijskom šumu, ravnoteže među ovim procesima. Kod tala na području Istre na ove odnose primarno utječe izrazita razlika u karakteru geološke podloge

Discriminant Analysis as a Tool for the Distinction of Quaternary Sediments in the Region of Djurdjevac

Discriminant analysis of Quaternary sediments in the region of Djurdjevac was performed in order to determine the optimum criteria for distinguishing between previously established groups of deposits. Geological properties utilized in the procedure of discrimination are represented by the results of modal analysis. Among the seven groups related to the Quaternary sediments of the Drava river depression, only three proved to be distinctive; Pleistocene alluvial deposits (Q1), Pleistocene loess (lQ1), and Holocene deluvium (dQ2), while others proved to be modally uniform. The close relationship between characteristic minerals and individual genetic groups (Quaternary facies) proved to be useful in labelling the most prominent discriminant functions, thus equipping them with particular sedimentological meaning. Three of the six functions indicated the provenance of the source material, as well as conditions of transport and sedimentation within the Quaternary sedimentary cycle of the studied part of the Drava river depression in the Pannonian basin