Górnojurajskie ooidy o niewspółśrodkowych powłokach

Andrzej Gąsiewicz

Abstract


 Opisano specyficzne ooidy o niewspółśrodkowo ułożonych powłokach, pochodzące z górnojurajskich

mikrooolitow – otwor Hedwiżyn 2 na południowej Lubelszczyznie. Ekscentryczne powłoki świadczą,

że oolityzacja ziarn zachodziła w kilku fazach przedzielonych dłuższymi okresami ich spoczynku na dnie zbiornika.

 

UPPER JURASSIC OOIDS WITH ECCENTRICAL COVERS

 

Specific ooids with eccentrically arranged covers are described from Upper Jurassic microoolites in the borehole column Hedwiżyn 2, southern part of the Lublin region.

Eccentric ooids form a very small admixture in pelloidal wackestones and grainstoncs and ooid packstones. The grains are built of a number of larger and larger ooids, usually with very thin accretional cover. They are arranged in this way that internal grains are placed in one focus of ellipse, alternatively in both foci, or completely eccentrically. Moreover, micritic inter-envelopes varying in thickness and extent, occur between laminae of ooid.

The phases of oolitization, up to four at the most here have been separated by relatively long periods of rest of grain at the sea floor and development of micritic covers. In successive periods of increase in water turbulence, some grains were moved and subjected to abrasion and oolitization. The repeated cycles of water turbulence and quiescence resulted in origin of eccentrical arrangement of laminae in

ooids.


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