Biostruktury w łupkach miedzionośnych a monoklinie przedsudeckiej

Jerzy K. Błaszczyk


W Lubińskim Zagłębiu Miedziowym na monoklinie przedsudeckiej w łupkach miedzionośnych występują lokalnie liczne biostruktury. Wyróżniają się one regularnym i w przybliżeniu powtarzalnym kształtem, owalnym przekrojem oraz stałym położeniem w profilu łupków miedzionośnych. Część ich to wypełnienia pustek po prawdopodobnie allochtonicznych korzeniach krzewów lub niedużych drzewach. Inne natomiast, występujące w stropie łupków, są wypełnieniami jamek mieszkalnych (domichnia) najprawdopodobniej zwierząt bentonicznych zamieszkałych w osadzie i pobierających pokarm z jego powierzchni. Identyfikacja owych biostruktur pozwoliła na wydzielenie dwóch mikrośrodowisk, będących częściami składowymi środowiska równi pływowej, w którym osadziły się łupki miedzionośne.



In the Lubin Copper Basin (Fore-Sudetic Monocline), there are differentiated two microenvironments which represent components of tidal flat environment. One of these microenvironments is characterized by predominance of dark-gray carbonate-clay facies. This facies was developing in depressional parts of area of the-Fore-Sudetic Monocline, connected with one another by a network of tidal channels. Pelitic, phyto- and biogenic material deposited in these depressions was coming from higher situated areas, occupied by salty marshes with halophytie vegetation. Large of plants could be preserved only when previously fossilized. Other fragments of plants became accumulated in the form of fine intercalations in shales as well as scarce black coal accumulations. Moulds of Lower Zechstein roots usually occur in middle part of clay-dolomitic shales, in horizontal, or somewhat oblique position. They are cylindrical in shape, often meandering and with convergent conical diameter. There surface is covered with numerous irregular knobs, ripples and grooves, usually oriented normally to their length, as well as striae arranged parallel to the length and usually best marked at inner side of bends. The moulds are formed of light-gray sandy dolomite.

The other microenvironment has been the major one in areas drained by tidal channels. Sediments accumulated there display influence of light-gray carbonate facies: shales are overlain by light-gray sandy dolomite. Development of benthic fauna is shown by trace fossils ((Scolithos) - dwelling burrows (domichnia) of animals living in sediment and gathering food from its surface. Along their whole length, Scolithos are characterized by uniform, circular or elliptical cross-section, and there is no narrowing at their end. They occur at the top of dolomitic-clay shales, usually in vertical position, normal to shale separateness. Scolithos are formed of sandy dolomite, laminated with dark-gray clay matter, and their external surface sometimes displays irregular ripples, usually arranged oblique to their length.

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