Ewolucja diastroficzno-sedymentacyjna basenu śródsudeckiego w późnym silezie i wczesnym autunie

Jerzy B. Miecznik



Intra-Sudetic Basin originated in the Early Carboniferous during the geosynclinal stage of the Variscan development, as an intermontane molasse-trough. In the Late Carboniferous it was incorporated into the pattern of superimposed intermontane troughs of the Bohemian Massif. In the course of its evolution during the Carboniferous to Permian times the expansion of sedimentary area was paralleled by a distinct migration of the depocenter in the SE direction. The latter phenomenon was probably an effect of the Karkonosze granitoid intrusion at the NW-margin of the Basin.
In the early Westphalian a deposition took place mostly in local troughs of which the largest i.e. the Wałbrzych and Żacler ones are located in the northern part of the Intra-Sudetic Depression. The important feature of the lower Westphalian deposits is the occurrence of coal horizons. During the Westphalian B the troughs were being gradually filled with sediments, and subsequently in the late Westphalian the strongest subsidence started in the central part of the Depression. The marginal parts of the Basin became the sites of alluvial fans developing along active faults while in the central area fine-grained sediments were deposited in fluviatile, lacustrine and intermittently also marsh environments. At the same time the volcanism became active as expressed i.e. by lava flows and explosive eruptions.
In the early Stephanian a relative uplift of the framing massifs resulted in a deposition of more coarsely grained sediments - arkosic in the south (the Zaltman Arkose), while enriched in the rhyolitic material in the north. This latter material was largely derived from the Rusinowa-Grzmiąca Volcanic Belt which has been emerging as a positive morphological element at this time.
The important restructuring of the Intra-Sudetic Basin occurred as a result of the tectonic Intrastephanian Phase, at the turn of the Stepbanian B and C. The movements of this phase were reflected in a predominance of sedimentation, partial erosion of Carboniferous deposits and slight tilting of Carboniferous strata. The depocenter shifted farther to the south-east.

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