DEPOSITIONAL ENVIRONMENTS AND SEQUENCE STRATIGRAPHY OF GLAUCONITES OF WESTERN BLACK SEA REGION

Yıl 2000, Cilt: 122 Sayı: 122, 1 - 21, 01.03.2000

Baki Varol A- Mete Özgüner Erdal Koşun , Şefik Imamoğlu Mahmut Daniş Tahir Karakullukçu

Öz

Glauconitic sediments which are subject to this study, have been
deposited with different age and facies characteristics around Devrek-Zonguldak
and Kastamonu regions. Glauconies within Lower Cretaceous sequence of Western
Black sea region, developed in siliciclastic units which had been deposited in
outer shelf by transgressive conditions. Typical occurrences, are found in
Sapca formation of Zonguldak region. Glauconitic sandstones have preferably
been accumulated in sand bars during sea level changes controlled by eustatic
and tectonic factors. These sediments are characterised by large and small scale
cross beddings, sheet sands with parallel lamination, and bioturbation.
Glaucony grains within the sandstones have autochthon and allocton
characteristics according to their depositional environments. The movements
within the environment of glaucony formation had been accomplished by long and
short distance displacements. In consequence limestone, quartz, feldspar and
mafic rock grains which had been subjected to different degrees of
glauconitisation were concentrated in off shore sand bars. The glauconies have
been cemented by argillaceous matrix that shows different degree of
glauconitisation or rarely cemented by carbonate within the silicislastics. The
glauconitisation in Kastamonu region is observed within Lower Eocene units. This
mineralisation had been developed in carbonate facies which differs from
Zonguldak region. The areas where Lower Eocene limestones of reefal
characteristics laterally pass to open sea facies, have prepared suitable
environmental conditions for the glaucony formations. Fossil, intraclast and
pellet type carbonate grains in this level have been glauconitised by different
degrees and exhibit hard ground and complete authocthon properties. Glaucony
occurrences of the region have widely been controlled by sea level changes.
Autochthon glauconies of silisiclastics of Zonguldak region which had
especially been formed in periods of maximum transgression, were transported to
the lower system tracts by regression of the sea. Glaucony formation of
Kastamonu region occurred in hard grounds which marked upper surface of reefs
when they had been drowned by rapid rising of sea level.

Anahtar Kelimeler

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Kaynakça

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