Publication details
Terciérní říční sedimenty v širším okolí Jihlavy
| Title in English | Tertiary river deposits in the wider surroundings of the Jihlava city |
|---|---|
| Authors | |
| Year of publication | 2019 |
| Type | Article in Periodical |
| Magazine / Source | Geologické výzkumy na Moravě a ve Slezsku |
| MU Faculty or unit | |
| Citation | |
| Web | https://journals.muni.cz/gvms/article/view/12024 |
| Doi | http://dx.doi.org/10.5817/GVMS2019-1-2-24 |
| Keywords | Jihlava Furrow-facies analysis-channel infill-flood plain-crevasse splay |
| Description | Tertiary deposits have been known around Jihlava town for many years. However, they have never been thoroughly studied. Most of the known occurrences of these deposits are situated in the Jihlava Furrow. During the drilling research, these Tertiary deposits were newly detected in three wells: HGM-1, V1 and V4. Facies analysis, petrography and gamma spectrometry were performed on the studied samples taken from all three wells. The model of basement of Cenozoic deposits has been constructed. Based on facies analysis, 8 lithofacies (7 studied deposits and 1 eluvium) have been described. The study of lithofacies have made possible to recognized the depositional environments of the Tertiary deposits. The depositional environments of these deposits are interpreted as fluvial channelized gravels and non-channelized deposits (flood plain, crevasse splays, oxbow lake and lake). The channelized gravels have been found by the well HGM-1 in the overburden of the crystalline rocks of the Moldanubian. Their thickness is relatively low (1.7 m) and the channels were probably not deep. The non-channelized deposits are formed by clays, silts and fine-grained sands. In the upper part of the succession the layer of the organic deposits (peat) has been detected. The results of petrography have shown that material originated from the local sources, especially Moldanubian Unit and Jihlava Massif (gneisses, mica-schistes, granitoids, less pegmatites and phyllites). The high concentrations of Th and U have been found in the studied deposits. These high concentrations can be associated with the source rocks. The values of Th/U and Th/K ratios are significantly higher in the studied deposits than in eluvium. This indicates conditions of weathering and sedimentation, and also points to input of the material from several sources. The model of basement crystalline shows that there were probably at least two spatially separated fluvial river systems. One river system was situated in the area Velký Beranov and Měšín. The preserved remains of the second system are visible in the area of Jihlava city and its peripheral parts (Bedřichov and Pávov). |