Publication details
Redeposition patterns in Mississippian carbonate breccias (Moravo-Silesian Basin, Central Europe): from passive margin to foreland basin
| Authors | |
|---|---|
| Year of publication | 2007 |
| Type | Article in Proceedings |
| Conference | 25th IAS Meeting of Sedimentology 2007, Patras - Greece, Book of Abstracts |
| MU Faculty or unit | |
| Citation | |
| Field | Geology and mineralogy |
| Keywords | microfacies; conodonts; foraminifers; biostratigraphy; erosion; tectonic subsidence; foreland basin |
| Description | Carbonate successions deposited during the passive-margin phase of the Moravo-Silesian Basin (MSB) and younger siliciclastic turbidites deposited during its foreland-basin phase are separated by sparse bodies of Middle Tournaisian to Viséan rudstones and pack/grainstones with phosphate intraclasts (phosphatic breccias). Compositional analysis and conodont biostratigraphy data suggest this facies represents an important lithology in our understanding of this tectono-stratigraphic boundary. The breccias are preserved in lens-like bodies consisting of graded, grain-supported heterolithic rudstones to pack/grainstones, massive, coarse-grained rudstones with packstone/grainstone matrix, and thin, parallel-laminated and/or normally graded pack/grainstones. Allochems include abundant carbonate intraclasts, angular clasts of phosphatised radiolarian mudstones/wackestones, ooids, peloids, oncoids, echinoderms, and less frequently rugose corals, brachiopods, bryozoans, foraminifers and rare conodonts. Their analogues were also found in neptunian dikes. The onset of the breccia sedimentation was distinctly diachronic within the interval from the Middle Tournaisian to the Viséan. The breccias contain reworked conodonts and corals of Tournaisian, Famennian and even Frasnian age. The breccias are often underlain by Famennian carbonates suggesting that their deposition followed an erosional episode. Sedimentary characteristics and composition of the breccias suggest that they were deposited in a high-energy marine environment associated with deep erosion of their source areas, presumably at the toes of submarine slopes. Diachronic start of the breccia sedimentation and their lens-like geometry suggest that local controls prevailed during their deposition, most presumably in a fault-related setting. This is supported by the neptunian dikes and Tournaisian differential subsidence patterns derived from isopach maps of the MSB. Temporal and spatial distribution of the breccias indicates their rejuvenation in W-to-E to NW-to-SE direction, roughly parallel to the distal-to-proximal cross-section of the former passive margin. The breccias recorded a period of intense faulting and surface morphology changes due to plate collision, prior to the flexural subsidence and deposition of the siliciclastic flysch. This tectonic regime presumably acted on the background of eustatic oscillations in the typicus and lower anchoralis CZ. In this respect, the situation resembles the late Tournaisian phosphorite deposition of the Antler foreland of North America. |