Pelagiczne stromatolity z wapieni albu wierchowego Tatr

Abstract

Przedstawiono cechy sedymentacyjne, geomikrobiologiczne i diagenetyczne pelagicznych stromatolitów z wapieni albu wierchowego Tatr. Stromatolity te zajmują pośrednie miejsce między stromatolitami strefy litoralnej a stromatolitami oceanicznymi. Tworzyły się w środowisku otwartego szelfu w warunkach powolnej sedymentacji pelagicznej.

PELAGIC STROMATOLITES FROM THE HIGH-TATRIC ALBIAN LIMESTONES IN THE TATRA MTS

A reinterpretation of conditions of stromatolite development in the High-Tatric Albian condensed limestones in the Tatra Mts (Fig. 1) is presented. The stromatolites cover surfaces of mature hardgrounds built of pelagic biomicrites (wackestones - Fig. 2) and are associated with incrusting organisms (Table I, Fig. 6; Table II, Fig. 7). The microstructure of the stromatolites results from a superposition of trapping and flocculation processes, during their growth (Fig. 3); the occurrence of abundant Frutexites forms is characteristic (Table III, Figs 8 - 10; Table IV, Figs 11 - 13). The stromatolites contain remains of abundant and differentiated communities of stromatolite-building and decomposing microorganisms (Table V, Figs 14 - 19) and endolithic ones (Table VI, Figs 20 - 22). Large amounts of non-carbonate (phosphate-silicate-oxide) substance in the investigated stromatolites (Table VII, Figs 23, 24; Table VIII, Figs 25 - 27) and many processes of non-carbonate early diagenesis (Fig. 4) resulted from recession of carbonate sedimentation during growth of stromatolites in the hardground environment.

The High-Tatric Albian stromatolites, as it shown by their sedimentary, geomicrobiologicai and early diagenetic features, represent intermediate position between littoral (tidal) stromatolites and oceanic (basinal) ones. They have orignated in open shelf environment under conditions of slow pelagic sedimentation (Fig. 5). Cyclic development of hard grounds, abundant phosphatic mineralization and stromatolitic horizons might have been controlled by rhythmic changes in sea-level during sedimentation of the Albian limestones.