Budowa geologiczna południowego skrzydła fałdu Gorlic między Gorlicami a Krygiem (Karpaty środkowe)

Franciszka Szymakowska

Abstract


Geology of the southern limb of the Gorlice fold between Gorlice and Kryg (Polish Flysch Carpathians)

The Gorlice fold is the southernmost, fold of the Silesian nappe which in turn plunges under the highest unite of the Flysch Carpathians i. e. the Magura nappe (Fig. 1). The border zone of the Magura nappe on the territory under discussion is built of Upper Cretaceous and Paleogene deposits. In the axial zone of the Gorlice fold there crape out the uipper Istebna beds in the sandstone facies (Upper Cretaceous). The southern limb of the fold is build of Paleocene, Eocene and Oligoeene deposits (Figs. 2,4). To the Paleocene belong the lower variegated shales which are 30 to 50 metres thick. Over them develope the Ciężkowice Sandstones (Lower Paleocene — Eocene). They are dividd by variegated shale intercalations into Ciężkowice Sandstone I and II, 50—150 and 30—55 metres thick respectively. The Paleocene age of the base part of the Ciężkowice Sandstone II is documented by Discocyelina seuense Douv. and Rzehakina fissistomata (Grzyb.). The sedimentation of Ciężkowice Sandstones comes to a close with the variegated shales. Their thin horizon (1—2 metres tick) can be observed along the entire length of the southern flank of the Gorlice fold. Over them appear the Hierogliphic Beds, 50 (eastern part) up to 100 metres thick (western part). In the lower part of these beds there occur Nuimmulite pianatus Grzyb., which points to Lower Eocene. The upper part of these beds encloses Middle Eocene with Cyclammina amplectens Grzyb, and Upper Eocene with C. rotundidorsata (Hantken) and Ammodiscus umbonatus Grzyb. Immediately over the Hieroglyphic Beds lie Magdalena Sandstones which in this region begin the sedimentation of Menilite Beds (Fig. 4). Lack of cherts in the lower part of the Menilite Beds is the characteristic distinguishing this territory from the remaining part of the Silesian nappe. Menilite Beds (Magdalena Sandstones) in some profiles pass gradually into the next lithostratigraphic unit, i. e. the Krosno Beds, in others no passage zone is visible. The Krosno Beds have been divided into three units: lower — thick bedded sandstones (about 400 metres thick) middle — corrugated sandstones, platy and thick bedded and grey shales (about 550 metres thick) upper — shales with subordinate sandstones (about 1200 metres thick). In the region SW from Kryg there is a patch built of Cretaceous and Paleogene formations (Figs. 1, 2). These formations belong to Harklowa facies of the Magura nappe and lie over the Lower Krosno Beds of the Silesian nappe at a distance of about 600 metres north of the contemporaneous border of the Magura nappe. The genesis of this patch is not at all clear. It can be a tectonic outlier of the Magura nappe or an oTistostroma formed by a submarine or a land slide. The Gorlice fold in the west plunges under Wola Łużańska promontory of the Maigura nappe and in the east under Harklowa promontory of the same nappe (Fig. 1). Both promontories belong to the northern facial zone of the Magura nappe (Harklowa facies). The southern limb of the fold is pushed steplike towards the north along several N — S running faults. These faults were formed as a result of pressure exercised by the Magura nappe from the south (Fig. 2). Chiefly arenaceous development of the sediments starting with the Upper Cretaceous up till Oligocene, the lack of cherts in the base of the Menilite Beds (Maigdalena Sandstones), and recurring numerous intercalations and lenses of conglomerates in the Istebna Beds, Magdalena Sandstones and Lower Krosno Beds indicate that there existed here a fuirrow of highly mobile sedimetation within the range of strong activity of currents carrying detritic material. The flute oasts indicate that starting with the Ciężkowice Sandstones up to the Lower Krosno Beds the material was transported from W, SW and NW in the case of the Upper Krosno Beds from S and SW.

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