Stromatolity jurajskie w Polsce

Michał Szulczewski



The present paper is concerned with all the Jurassic stromatolites of Poland; those known previously as well as the new ones found by the writer. They come from the Bathonian of the Tatra Mts., the Lower- and Upper Callovian of the Mesozoic margin of the Holy Cross Mts., the Callovian and Lower Oxfordian of the Cracow-Częstochowa Jura and the Callovian boreholes in the Polish Lowland. Speculations as to the organic or inorganic origin of the Jurassic stromatolites are made and their biosedimentary nature is clearly shown. Various stromatolitic forms and character of their association are described. Stromatolitic microstructures are described in greater detail. Stress is laid on the abundance of detrital material and its selective deposition in Jurassic stromatolites, as well as on the dependence of stromatolitic microstructures on the character of the surrounding rocks. Profiles are presented to illustrate the position of stromatolites in the development of Jurassic sedimentation. The foIlowing constant features in the occurrence at stromatolites have -been emphasized and interpreted: their connection with sratigraphic gaps, with transgressive or regressive deposits, with stratigraphic condensation and the stirring up of variously aged faunal remains, also with distinctly shallow-water deposits. It is pointed out that stromatolites seem to occur exclusively in epicontinental areas and on intrageanticlinal ridges in geosynclinal areas. The potential value of Jurassic stromatolites as facial index is discussed on the results at analyses of profiles bearing Jurassic stromatolites, and by comparison with recent stromatolites. It has been found that in the mode of origin Jurassic stramatolites are analogous with the recent marine forms. Hence they may be reasonably accepted as indicators of the littoral zone as well as of the shallowest part of the infralittoral zone. The occurrence zone of some types of stromatolites is particularly limited. A comparison of the Jurassic and other Mesozoic stromatolites with pre-Mesozoic and recent forms shows closer analogies of the Mesozoic stromatolites with the recent forms than with the old-Paleozoic and Precambrian stromatolites. On the presence and characteristic features of stromatolites conclusions have been drawn concerning the sedimentation and paleogeography of their occurrence area.

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