Publication details
Subglaciální štěrkovité tilly u Jindřichova na Osoblažsku
| Title in English | Subglacial gravely tills from Jindřichov in the Osoblaha Spur |
|---|---|
| Authors | |
| Year of publication | 2010 |
| Type | Article in Periodical |
| Magazine / Source | Časopis Slezského zemského muzea |
| MU Faculty or unit | |
| Citation | |
| Field | Geology and mineralogy |
| Keywords | Subglacial tills Clast petrology Nordic indicators Till clast fabric Continental glaciation Pleistocene Elsterian glaciation Jindřichov sandpit Osoblaha Spur Czech Republic |
| Description | The description of a sedimentary succession in the Jindřichov sandpit in the NW Osoblaha Spur is given in this paper. The studied site lies at 385 m a.s.l. and represents the only known exposure of glacigennic sediments in the Osoblaha Spur. The exposed section includes the succession of lodgement till, subglacial glaciofluvial sand, subglacial melt-out till, geliflucted and cryoturbated subglacial melt-out till, and finally loess loam. The lowermost two tills were studied from sedimentary petrological point of view. They are both very gravely, lodgement till contains ~46 wt.% of gravel, subglacial melt-out till ~33–43 wt.% of gravel fraction. Petrological composition in 16–64 mm fraction comprises in both till units Culmian sediments, quartz, crystalline rocks from Jeseník region (mainly quartzite of the Vrbno Group), rocks from Poland territory (platform Cretaceous sediments, Sudetian porphyry) and Nordics, which make ~5,5–6% of the clasts. Fabrics of elongated clasts in tills show their genetic relationship and strong influence of melt-out processes for the sedimentation in the subglacial zone. According to preferred clast orientation the ice sheet moved from the NE towards the SW at the site. Due to the high share of the Vrbno Group quartzites and only accessory share of the crystalline rocks from NW Jeseník region we assume the general movement in the northern forefield of the Osoblaha Spur from the NNW towards the SSE. The spectrum of Nordic indicators is characterized by a significant predominance of Eastern Fennoscandian rocks (~53 %) over the Southern Swedish rocks (~24,5 %) and the rocks from Dalarna (~22,5 %). These shares correspond to other Elsterian tills in the territory of the Odra lobe of the ice sheet. |