Wstępne dane o środkowodewońskich (dolnoeifelskich) otwornicach z zachodniej części Gór Świętokrzyskich

Jan Malec


 Scharakteryzowano zespoły otwornic występujących w dolnym eiflu otworu Porzecze IG SA. Przedstawiono pionowe rozprzestrzenienie poszczególnych rodzajów otwornic w badanym profilu. Szczegółowo opisano dwa gatunki: Sorosphera columbiense Stewart et Lampe i Webbinelloidea similis Stewart et Lampe.

Zwrócono uwagę na duże podobieństwo gatunków w opisanych z Porzecza do analogicznych gatunków ze środkowego dewonu USA.





The described foraminifers come from core material from the borehole Porzecze IG SA in western part of the Góry Świętokrzyskie Mts (Fig. 1). The borehole column comprises Upper Emsian (Lower Devonian) and Lower Eifelian (Middle Devonian) rocks occurring in reversed position (Fig. 2).

Foraminifers were found to be fairly common at depths 32.8–115.5 m (Fig. 2), forming assemblages typical for certain depth intervals. There were identified foraminifer genera with tests built of pseudochitin substance (Amphitremoida, Lagenammina, Saccammina) and agglutinated, built of fine quartz grains (Hyperammina. Sorosphaera, Tolypammina, Webbinelloidea). An assemblage of foraminifers with pseudochitin tests is known from the depth interval 51.0–67.1 m. The foraminifers are small in size and with thin brown tests. Specimens are ranging from 0.20 to 0.60 mm in length and 0.10 to 0.27 mm in diameter.

Representatives of the genus Tolypammina, found at the depths 40.5–59.5 m. are characterized by thin white tubular tests, sinusoidally bent and built of fine quartz grains. The tests are up to 1.00 mm long and about 0.10 mm in diameter. Representatives of the genus Hyperammina have been found at depths 74.8101.5 m. Their tests have the form of straight massive tubes built of fine quartz grains and white to yellow-white in colour, 0.60–1.30 mm long and 0.17–0.30 mm in diameter. Sorosphaera columbiense Stewart et Lampe is known from the depths 108.0–115.5 m. The majority of specimens represent single chambers only and a few ones – two chambers tightly connected with one another. The tests are about 0.63–0.77 mm-long and 0.35–0.43 mm in diameter. The species Webbinelloidea similis Stewart et Lampe has been found at the depths 32.8–115.5 m. It is here represented by four morphological groups and five subgroups (IA, IB, IIA, IIB, IIIB and IV), differentiated after E. Conkin and B. M. Conkin (1970). Flat, one-chambered or, sometimes, two- or three chambered tests with apertural opening situated far from the middle of upper wall and poorly visible, predominate in lower part of the borehole column, and convex, one to, sometimes, two-chambered tests with apertural opening situated in the middle of upper wall and well visible in upper part of the column.

The described species appear markedly similar to those known from the Middle Devonian in the USA (Columbus Limestone, Delaware Formation).

In the Porzecze section, convex tests of W. similis Stewart et Lampe (Fig. 2) are accompanied by numerous gyrogonites of Charophyta of the genus Sycidum in the depth interval 78.6–101.9 m (J. Malec, 1982). Variable shape of basal walls of these foraminifers (flat. concave. convex. wavy) and their outline (circular, ovate or sometimes quadrate to triangular) presumably represent reflection (negative) of surface to which the tests have been attached. The reflected surface is presumably that of vegetative “stems” of Charophyta, calcified fragments of which have been found to accompany the gyrogonites.


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