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Evolution of a sedimentary infill of a palaeovalley at a distal margin of the peripheral foreland basin

Nehyba Slavomír, Gilíková Helena, Tomanová-Petrová Pavla, Otava Jiří, Skácelová Zuzana

Geological Quarterly

2019

Vol. 63, No. 2

319--344

The entrenched Odra palaeovalley, cut into the bedrock of the distal margin (forebulge basal unconformity) of the Moravian Carpathian Foredeep (peripheral foreland basin) is filled with an almost 300 m thick pile of Miocene deposits. The directon of the valley (NW-SE to NNW-SSE) has been controlled by faults subparallel with the system of “sudetic faults“. The sedimentary succession consists of 5 facies associations/depositional environments, which are interpreted (from bottom to top, i.e. from the oldest to the youngest) as: 1 - colluvial deposits to deposits of alluvial fan, 2 - deposits of alluvial fan, 3 - fan-delta deposits, 4 - shallow water delta to nearshore deposits and 5 - open marine deposits. This fining-up and deepening-up succession reveals the following: the formation of the new flexural shape of the basin; deep erosion connected with uplift and tilting of the forebulge and reactivation of the NW-SE trending basement faults; the Early/Middle Miocene sea level fall; alluvial deposition mostly driven by tectonics and morphology; forebulge flexural retreat; Middle-Miocene sea level rise; back-stepping of valley infill; marine invasion during the Early Badenian with shift of the coastline further landward of the pallaeovalley. Tectonics related to contemporary thrusting processes in the Western Carpathians are assumed to be the dominating factor of the studied deposition at the expense of eustatic sea level changes. Provenance studies have proven that the pre-Neogene basement (i.e. the Early Carboniferous clastic “Culmian facies” ofthe Moravian-Silesian Paleozoic) represents an important source for the conglomerates and sands, which volumetrically dominate in the palaeovalley infill. However, they also showed, that the deposits of the earlier Carpathian Foredeep Basin sedimentary stage (Karpatian in age?) covered the area under study and were eroded and resedimented into the palaeovalley infill.

Foreland provenance of thick conglomerates in the early stage of the Carpathian Foredeep development : the case of the Sloboda Conglomerate (Lower Miocene), western Ukraine

Oszczypko N., Uchman A., Bubniak I.

Geological Quarterly

2012

Vol. 56, No. 4

789--802

The upper part of the Lower Miocene Sloboda Conglomerate, a 250–1400 m thick unit, was deposited mainly on an alluvial fan and fan delta during the early stages of Carpathian Foredeep development. During of the Old Styrian overthrust movements of the Carpathian orogen, a forebulge was formed, which supplied clasts to the conglomerate. The clasts are dominated by Late Proterozoic–Early Cambrian phyllites, while Paleozoic carbonates are common, and Mesozoic and other rocks are rare. The source area formed mainly by a prolongation of the Małopolska Massif that was involved in the forebulge; this was located close to a palaeovalley cut into Mesozoic and Paleozoic rocks, buried under younger strata. Additional material was derived from the advancing front of the Carpathian Flysch nappes.